Aging of Solder Joints over 1,600 Years: Evidence from Nubian Bronze Artifacts, The

Solder joints and coatings found in bronze artifacts recovered from the Nubian Desert in Egypt show evidence of the decomposition of the lead-tin eutectic structure and solid-state growth of the ε and η intermetallic phases at the solder-bronze interface at ambient temperature. Accelerated aging experiments reproduced the structures observed in the artifacts. The data show that the growth of the intermetallic compounds is diffusion-controlled at low as well as high temperature with an activation energy of 20 kcal/mol.

SOLDER IN THE BRONZE ARTIFACTSThe excavators determined the ages of the artifacts from their knowledge of the burial characteristics and the associated grave goods. Since the only bronze smelting known to have been carried out in Lower Nubia was about 2500 B.C.,9 long before the Meroitic Period, the bronze artifacts are identified as trade goods manufactured within the Roman Empire and traded into Lower Nubia.10 It is possible that Nubian artisans undertook some repairs or modifications before the artifacts were finally placed in graves.INTRODUCTIONThe microstructure of the solder taken from the bottom of bowl B (Figure 7) has a nearly continuous lead phase containing regions of tin phase, and a layer of intermetallic compound that was in contact with the bronze bowl surface. The x-ray maps define the layer of intermetallic compound, showing that the η phase is 6 µm thick and that particles of η are dispersed in the solder. There is no trace of eutectic structure.Metallographic samples were prepared by standard methods. For optical microscopy the lead-tin alloys were etched with a glycerin-acetic acid-nitric acid (84:8:8, respectively) mixture when needed. The specimens were examined in the as-polished condition for microprobe analysis. A JEOL Superprobe 733 operating at 15 kV with a beam current of 20 nA to 50 nA, depending on the element analyzed, was used with wavelength-dispersive spectrometry (WDS) to determine alloy compositions. Energy-dispersive spectrometry (EDS) was used to analyze the coating on bowl PM 262,230. Overall compositions, reported as weight percent in Table II. were determined from the compositions of the individual phases present and the volume fraction of each constituent as found by image analysis.The ladle, D (Figure 3), was made from one piece of 2 mm thick bronze sheet by a complex metal-forming operation that shaped a bowl at the end of a handle that terminates in the figure of a serpent's head. A sample was taken from the solder present in the bottom of the bowl that appears to have been used in an attempt at a repair.The artifacts were recovered by the Pennsylvania-Yale Expedition to Egypt at the sites of two communities in Lower Nubia, Arminna West, and Toshka West, located on the west bank of the Nile between the major archaeological sites of Abu Simbel to the south and Karanog to the north.6,7 The cemeteries at these sites contained more than 250 grave complexes that held iron and bronze artifacts from the Meroitic (300 B.C to A.D. 370) and X-Group (A.D. 370-550) periods.8Two thin-walled bronze bowls (B and C in Table I), have remains of tinning on both interior and exterior surfaces, and bowl B (Figure 2) has an accumulation of solder in the bottom, perhaps from an attempt to repair damage. A sample of this accumulated material was extracted for analysis. The lining material was examined on cross sections taken from the bowl rims.The microstructure of the solder retrieved from ladle D (Figure 8) consists of a continuous lead solid solution (dark in the micrograph), islands of tin solid solution dispersed in the lead constituent, and a few particles of η intermetallic compound. No layer of intermetallic compound detached from the substrate was present in this sample, and there is no trace of eutectic structure.The microstructures of the solders in the artifacts differ from that of a freshly made solder joint in the absence of eutectic structure, the greater thickness of the layer of ε and η intermetallic compounds, the presence of η-phase particles within the solder, and the absence of dendritic form in the primary lead constituent. The composition of the lead and tin phases (Table II) correspond to the equilibrium compositions of the alloy phases at about 50°C. Since in a freshly made solder joint the lead phase contains 3.3% tin in solution and the tin phase, 1.6% lead, it is evident that composition changes in both constituents have occurred in the 1,600-year interval since soldering was done. It is also evident that whatever eutectic structure was present in the solder at the time the joints were made has vanished in the intervening 1,600 years. Recent research has shown that the eutectic structure formed upon cooling; lead-tin solder is not completely stable at room temperature. Coarsening of the eutectic structure can be observed within five years at room temperature, and can be accelerated by creep deformation or stresses induced by temperature changes.15,16 Growth of copper-tin intermetallic compounds at the interface between solder and a copper substrate at room temperature has also been observed.17Microstructures ObservedSoldering with lead-tin alloys was a technique well known and widely used by metalsmiths making bronze and silver products in the ancient world. These artisans also used tinning to decorate bronze and iron objects. In addition, they used it to cover the insides of bronze vessels used as tableware or in the kitchen to protect users from the bad taste that results from direct contact between bronze and food.1-5 Aging of tin-based solders is of particular interest today due to concern about the long-term reliability of soldered connections in electronic devices. This article reports on evidence of microstructural changes in the solder used in bronze artifacts retrieved from the Nubian Desert in Egypt. The solder has aged at ambient desert temperatures for at least 1,600 years.Examples of solder and of tinning were found on a mirror, a ladle, and two bronze bowls in the course of laboratory examination. These artifacts are in the collections of the Peabody Museum at Yale University, and are identified by their numbers in the museum catalog (Table I). The bronze mirror (Figure 1) is from the X-Group Period and is similar to the high-tin bronze mirrors widely used in Etruscan and Roman times, and also in India and China.11-13 A small piece of the solder used to attach the handle was taken for analysis without damaging the artifact.The solder from the mirror (Figure 6) consists of continuous lead solid solution containing regions of tin solid solution, and a layer of intermetallic compound originally in contact with the mirror surface. Dispersed particles of the intermetallic compound η phase are present within the tin phase. Compositions of the constituents are shown in Table II. There is no trace of a eutectic structure in the solder. The composition of the dark constituent in the intermetallic layer is 60% copper and 40% tin, identifying it as the e phase, and the lighter gray constituent has 38% copper and 62% tin, corresponding to the η phase. The average thickness of the e phase is 4 µm, and of the η phase, 12 µm. Since the solder separated from the bronze substrate by fracture through the e phase, the total thickness of the intermetallic compound layer may have been greater than 16 µm.

The microstructures of the solders in the artifacts differ from that of a freshly made solder joint in the absence of eutectic structure, the greater thickness of the layer of ε and η intermetallic compounds, the presence of η-phase particles within the solder, and the absence of dendritic form in the primary lead constituent. The composition of the lead and tin phases (Table II) correspond to the equilibrium compositions of the alloy phases at about 50°C. Since in a freshly made solder joint the lead phase contains 3.3% tin in solution and the tin phase, 1.6% lead, it is evident that composition changes in both constituents have occurred in the 1,600-year interval since soldering was done. It is also evident that whatever eutectic structure was present in the solder at the time the joints were made has vanished in the intervening 1,600 years. Recent research has shown that the eutectic structure formed upon cooling; lead-tin solder is not completely stable at room temperature. Coarsening of the eutectic structure can be observed within five years at room temperature, and can be accelerated by creep deformation or stresses induced by temperature changes.15,16 Growth of copper-tin intermetallic compounds at the interface between solder and a copper substrate at room temperature has also been observed.17

In case you missed it

Hand Soldering

JettingAuthors: Sibel Korkut, Dudley A. Saville and Ilhan A. AksayAbstract: A new technique for printing extraordinarily thin lines quickly over wide areas could lead to larger, less expensive and more versatile electronic displays, as well as new medical devices, sensors and other technologies. Theoretical predictions of the nonaxisymmetric instability growth rate of an electrohydrodynamic jet based on the measured total current overestimate experimental values. The authors show that this apparent discrepancy is the result of gas ionization in the surrounding gas and its effect on the surface charge density of the jet. As a result of gas ionization, a sudden drop in the instability growth rate occurs below a critical electrode separation, yielding highly stable jets that can be used for nano- to microscale printing. (Physical Review Letters, Jan. 25, 2008)"Enhanced Stability of Electrohydrodynamic Jets through Gas Ionization"Authors: Mudasir Ahmad, David Senk, and Jennifer Burlingame; mudasir.ahmad@cisco.com.Abstract: The conversion to Pb-free BGAs has raised several new assembly and reliability issues. One reliability concern becoming more prevalent is the increased propensity of pad cratering. In general, Pb-free solder joints are stiffer than SnPb solder joints, and some Pb-free compatible PCB dielectric materials are more brittle than conventional SnPb-compatible PCB materials. These two factors, coupled with the higher peak reflow temperatures for Pb-free assembly, could transfer more strain to the PCB dielectric structure, causing a cohesive failure underneath the BGA corner pads. The likelihood of pad cratering occurring in any given assembly depends on several factors, including BGA package size, construction and surface finish, PCB pad size, and material and surface finish. Standard assembly-level bend, shock and drop tests can be used to determine if the entire assembly can survive a given strain and strain-rate range without failures. However, with these standard assembly-level tests, it is difficult to determine if the failures occurred as a result of an unusually weak PCB dielectric/PCB pad size or a stiffer BGA package."A Study of Soldering Tip Life on Lead-Free Alloys"In this study, an easy-to-implement test method is presented, along with results comparing known good and known bad PCBs. Different dielectric materials and pad sizes were evaluated to develop a comparative metric that can be used to rank-order different material/pad size combinations. The results were generated over different temperatures, to study the effect of temperature on dielectric mechanical strength characteristics. Finite element analysis was performed to better understand the factors impacting variation in results. (SMTA Pan Pacific Symposium, January 2008)"Analyzing and Predicting Electrochemical Migration Failures On Field Failure Returns"Authors: Juthathip Fangkangwanwong, Jareerat Jintana, Jarinee Ketui and Teng Hoon Ng; fjuthath@celestica.com."Methodology to Characterize Pad Cratering under BGA Pads in Printed Circuit Boards"Abstract: Soldering tips operating with Pb-free alloys show less durability than those operating with conventional SnPb solder. This is exacerbated by the higher temperature, higher tin content (tin readily erodes iron plating) and more aggressive flux in Pb-free soldering. Since the implementation of the RoHS directive, many companies have adopted SAC 405. Hence, for this study, SAC 405 solder wire was chosen as the natural rework solder for the investigation on the durability performance of solder tips from various suppliers. One of the known concerns of SAC 405 is the higher copper dissolution rate, which sometimes causes increased defect rates, especially in multiple PTH reworks. Another concern is the relative higher price of the alloy because of the silver content. In this paper, an alternative Sn-Cu Ni is proposed to determine the effect of alloy on solder tip life when compared with SAC 405 base alloy. (SMTA Pan Pacific Symposium, January 2008)Abstract: This paper outlines options available to analyze a specific lot of failed assemblies and steps that can be taken to prevent ECM failures on future lots. J-STD-001 is used as a guideline in preparing a customized test procedure. Exact procedures that may be used to assess working assemblies for ECM potential are outlined. Case studies are included. As a general procedure, monitoring points connected to the area of concern are isolated, often by removing components or cutting other traces, while wires are soldered. The assemblies are placed in a temperature/humidity chamber and a bias is applied across the suspect location. The resistance between these isolated points is monitored for sudden or slow drops indicative of leakage current development or dendritic growth. If ECM development is observed on these assemblies from the same lot, the entire lot should be considered at risk. (SMTA Pan Pacific Symposium, January 2008)Solder ReliabilityAuthor: Renee J. Michalkiewicz; rmichalkiewicz@tracelabs.com.

CIRCUITS ASSEMBLY provides abstracts of papers from recent industry conferences and company white papers. With the amount of information increasing, our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.

Lasers and High-Performance Cutting

When is a balloon not a balloon? When it�s a technical problem, a design challenge, and an inspiration for the development of new and more efficient cutting equipment.

www.ewt-inc.comPerformance and perforationThe following year, "back when 286s were the hot computers," Momany reminisces, he and colleagues at GrafikEdge helped develop Amiable Technologies sign-cutting software, and came very close to perfecting a swivel knife cutter of the sort that�s now widely used in the cutting business. "I didn�t trust the software engineers," he recalls this near-hit ruefully.Now with that trademark inventiveness and can-do attitude, Seattle-based EdgeWISE is pushing the limits of fabric cutting, in a system custom-designed to cut out the huge scientific balloons NASA plans to send to the very edge of Earth�s atmosphere."Ron and I discussed those 600-foot lobes, and I said, �Sure, we can do that,�" Momany says nonchalantly. "Our thinking has always been not-quite-mainstream, and that�s me. I�m a conceptualist; I have engineers to tell me what we can�t do." The enormity of the ultra long duration balloon poses huge manufacturing challenges. "The biggest problem was that NASA wanted the lobes to be cut to 600 feet plus or minus a quarter inch," Momany marvels. "These scientists are amazing. You get them in a room together and they have all these ideas, but they�re some-times not very realistic about manufacturing reality. We got them to agree to plus or minus three inches; that�s a .5 percent margin of error."Most cutting systems, Momany says, are driven by Hewlett Packard Graphical Language (HPGL), whose limitations render it unable to handle ULDB-sized projects. "With HPGL, you lose accuracy over long lengths of material�you run out of math; you run out of decimal points," he elaborates. EdgeWISE engineers have developed a new data processing technology that can achieve accuracy out to 16 or more decimal places."The limitation on most perforation operations is mechanical; it�s like they�re using a rotary pincushion, and the needles break all the time," Momany says. It�s not uncommon for needle breakage to occur several times a week, or even daily, resulting in four to eight hours of downtime each time. "The laser perforation could be used in manufacturing disposable diapers, band-aids, all kinds of geotextiles."EdgeWISE Tools founder Pat Momany � didn�t start out at the high-tech edge of the fabric cutting industry. Problems that need solving get his inventive juices flowing, and his penchant for saying, "Sure, we can do that," before figuring out how, add up to an enterprise that�s reinvented itself several times."We started focusing on designing and developing other laser tools, and were invited by Eastman Worldwide, an industrial fabric company, to exhibit in their booth at the 1997 Industrial Fabrics Association show in Nashville. That�s where I met Raven Industries� Ron Stevens, who was heading up the manufacturing end of NASA�s Ultra Long Duration Balloon Project," relates Momany.From boats to balloonsThe Ultra Long Duration Balloon Project (ULDB), profiled in our October 1999 issue, is NASA�s latest development in near-space scientific exploration. The project aims to develop balloon systems capable of supporting scientific observations above 99 percent of the Earth�s atmosphere, for durations of approximately 100 days. Innovations in materials and construction�the current design is 600 feet tall and pumpkin shaped, with lobes that increase its strength, and made of a one mil five-layer Mylar-polyethylene-polyester composite that provides a previously unavailable combination of gas barrier, tear resistance and strength�add up to a balloon that can take near-space extremes of temperature and sun exposure, and carry a couple thousand pounds of equipment.In the late �80s, Momany began teaching himself about lasers, and in 1990 sold GrafikEdge and started EdgeWISE Tools to develop, sell and service cutting tools and systems. EdgeWISE debuted a roll feed laser (RFL�) system at the International Sign Association show in 1992, and received a US patent in November of 1993. For a few years EdgeWISE licensed the technology to another company, but when this route failed to produce the desired growth, EdgeWISE began designing and selling its own RFL product line.As Momany explains the SDC�s advantages for the NASA application, he keeps bumping into his company�s own "cutting edge" issues: proprietary technologies, which he doesn�t dare explain in excessive detail. EdgeWISE is currently patenting the SDC system, with between 15 and 20 individual processes listed as claims on the application; this is one of four patent applications the company has going, and Momany expects to initiate another two sometime this year. (The tiny company, by the way, employs three full-time and two part-time workers, and uses five to seven contractors.)Reprinted with permission from Industrial Fabric Products Review April 2000. Copyright � 2000 by Industrial Fabrics Association International. Industrial Fabric Products ReviewWhile in Momany�s view it�s EdgeWISE�s small size and flexibility that enables it to take on these kinds of problem-solving challenges, he also admits that the aerospace client was originally nervous about the reliability of such a tiny supplier. The ULDB Project provided a needed dose of credibility. "When you say you�re working with NASA, that tends to get people�s attention," he concludes.The Single Direction Cutter (SDC) system was designed to provide precise beam delivery, material handling and motion control, developed to compensate for distortions due to material stretching.In addition to the advantage of taking up much less floor space than flatbed systems, the roll-feed SDC allows for faster throughput without increasing safety compliance issues or the need for training. "We try to make every machine using a Class One laser beam�as safe as your laser printer," Momany notes. By definition, Class One beams are totally enclosed. If, for example, the ULDB gores were to be cut with a laser moving over a flatbed, "to move 600 feet, it would have to be a Class Four beam�and everyone in the room would have to be laser-trained and wearing goggles," he explains.According to company literature, RFL technology offers significant advantages over traditional flatbed systems that cut with blades:

• the RFL takes only one-third to one-half the floor space of a flatbed;
• lasers use minimum heat, for less material distortion;
• lasers provide a high degree of accuracy, consistency, control and flexibility;
• the extremely small cut width allows for detailed work and close nesting of components, minimizing waste;
• lasers decrease the risk of injury, com-pared to many mechanical cutting methods.

"And with HPGL, at 3,000 inches, the system would just stop, and you�d have to re-send the images�but it wouldn�t have any way of knowing where it had left off," Momany says, noting that 3,000 inches, or 250 feet, is less than one-half the length of a ULDB gore. "Our system can just keep on going."Momany suggests that the SDC system would be suitable for a variety of applications with simple cutting patterns requiring high volume throughput, such as automotive air bags. The RFL system is faster than a flatbed, and the SDC is faster yet, able to handle 350 or more linear feet of material per minute.It started with boats. " I was in the printing business in 1985, and met a lady who was putting vinyl names and logos on the sides of boats," Momany relates. "Gerber had released a 15-inch vinyl text cutter, but she was doing graphics and logos in addition to letters. I wondered if we could somehow melt the vinyl to cut it. We started out with a soldering iron attached to an X-Y plotter." After working through many "thermal issues," midway through 1986 Momany, in partnership with another company that later went out of business, introduced a 36-inch thermal cutter to the sign industry.As it turned out, EdgeWISE�s SDC system was able to come darn close to the original tolerance requirement, at +/- .3 inches; but, as NASA, Dimension Polyant and Raven Industries continue to tinker with the composition of the balloon fabric, new hurdles emerge. Simply cutting one lobe down the middle of the run of fabric results in 40 percent waste, so EdgeWISE designed the system to cut half lobes down each straight edge, to be sewn together afterward, cutting waste down to only 14 percent. This means the system must be able to detect the fabric edge, which was no problem with the earlier translucent material. The most recent version of fabric, however, is transparent, so edge detection becomes a bigger problem.Now, EdgeWISE is working on adapting laser cutting technology to perforation applications. "We can take 60-inch-wide material and perforate it with a quarter inch separating the holes in a row, and a quarter inch separating the rows, at 85 feet per minute�that�s a half-million holes a minute," Momany says, noting that one client, an aerospace company, uses the resulting perforated material to filter resin evenly onto parts that must be glued together.

Reprinted with permission from Industrial Fabric Products Review April 2000. Copyright � 2000 by Industrial Fabrics Association International. Industrial Fabric Products Review

Solder-It SolderPro 150 heat tool

Solder-It offers its multi-functional, cordless SolderPro 150 heat tool with automatic ignition and soldering iron and torch functionality. Features include:

Circle 58 on inquiry card or click "e-inquiry" at www.pten.com* Also available with an accessories kit.The review* Can hold enough fuel for up to 120 minutes of use.* Patented, refillable Liquid Energy Cell filter system eliminates clogging.* The torch can produce blue flames of up to 2,400 degrees F.* The soldering iron is equivalent to a power range of 30 watts to 125 watts."The SolderPro 150 is great for those small jobs. The kit includes all the accessories to perform a professional wiring repair. If your shop performs electrical and wiring harness work, consider the SolderPro 150."Joe Marconi, owner of Osceola Garage in Baldwin Place, N.Y., tested the SolderPro 150 for PTEN.

Circle 58 on inquiry card or click "e-inquiry" at www.pten.com

Preventing Pb-free solder pot contamination; Brittle joints are one common result of poor maintenance

Monitoring the composition of the alloy in the solder pot is critical to maintain a stable wave or selective soldering process. Deviation from the original composition of specified alloy results in physical property modification, such as melting behavior and intermetallics formation.

[FIGURE 1 OMITTED]Iron contamination is a major concern. The only source of iron is the soldering equipment itself. A large body of research is dedicated to understanding the behavior of various Pb-free alloys, as well as compatible materials to resist the corrosive properties of these alloys. This work found all alloys have some corrosive effect on incompatible materials. The rate of corrosion varies significantly, ranging from insoluble to very soluble. The effect of alloys that are extremely aggressive to selected metals or materials is to react with the iron of the solder pot and its internal parts to form Fe[Sn.sub.2] needles (Figure 2). These needles have a melting point of 510[degrees]C; once formed, they neither melt nor dissolve. The needles grow over time and deposit in the areas where the solder pot has a low or stagnant flow. In some instances, they can flow into the wave, forming brittle joints. Iron content of more than 0.02% can indicate a non-compatible wave/selective soldering machine. It has been observed that pot materials are more vulnerable where solder flow is at its highest, such as in wave formers and pumps.Users should schedule monitoring of a solder pot's elemental composition. In the beginning, they should monitor the pot on a regular basis until a clear equilibrium is achieved. Solder pot composition can be monitored by x-ray fluorescence (XRF), atomic absorption spectroscopy, inductive couple plasma, scanning electron microscope (SEM), and gas chromatography mass spectrometry. Many solder suppliers offer these types of services at no cost to customers.In the typical wave or selective soldering process, the main elements of concern for a Pb-free solder pot are copper, iron and lead. The copper percentage increases based on board and component types used. Copper levels above 1% potentially impact the stability of the process by affecting the melting point and encouraging [Cu.sub.6][Sn.sub.5] intermetallics formation. The risk of these intermetallics traveling in the flow of the wave and ending in the joint increases when the copper content is not kept below 1%. The potential result: brittle joints. To reduce the copper in a SnAgCu bath, feed the solder pot with pure bars of SnAg or remove the alloy and replace with an appropriate amount of a corrective alloy.Iron dissolution is a safety hazard that impacts equipment integrity and solder joint reliability. It is important that the solder pot and internal parts are compatible with Pb-free processing. They should be protected by materials such as titanium, cast iron or stainless steel with a chromium carbide finish. Once the pot is contaminated with iron, the bath should be discarded and solder pot cleaned, just as with lead contamination.Ursula Marquez de Tino is a process and research engineer at Vitronics Soltec, based in the Unovis SMT Lab (vitronics-soltec.com); umarquez@vsww.com.[FIGURE 2 OMITTED]

Ursula Marquez de Tino is a process and research engineer at Vitronics Soltec, based in the Unovis SMT Lab (vitronics-soltec.com); umarquez@vsww.com.

ASK A GEEK

DO MY CHARGERS STILL SUCK POWER WHEN MY GAD GETS AREN'T CHARGING?

Granted, your use may be relatively little, but there are steps you can take to limit the amount of power your chargers waste. Start just by touching a plugged charger-if it's warm, it's using electricity. It's ideal to unplug adapters right after devices are fully charged; set an alarm for a few hours after you plug in to remind yourself to check on them. And if you're charging multiple devices at once, use a power strip so you can cut the power to all of them at once after charging.AN EARBUD TAPE MEASURE*Afraid so. Chargers and power adapters, which convert AC power to lower-voltage DC current for gadgets like cellphones, often still use some energy after they've completed charging. In fact, "vampire energy"-power consumed by electronics left in standby mode-accounts for 5 to 10 percent of all U.S. household electricity consumption.HAVE A 5-MINUTE project idea? Send it to us at h20@bonniercorp.com.MARIELA MOON is a technology reporter for goodcleantech.comHOW 2.0THE 5 minute PROJECTWhy: So you'll almost always have a tape measure handyDIY: 1. Hold the earbud cord next to a ruler and make inch markings. 2. Heat the cord gently with a soldering iron or other heat source so the ink doesn't smear. 3. Measure stuff.Got a question? Send it to us at h20@bonniercorp.com.

Adapters can also suck power even when they're plugged in but not connected to a device, so you may want to upgrade to Energy Star-certified ones (check the list of chargers for various devices at energystar.gov), which on average are 30 percent more efficient than others. Nokia's high-efficiency chargers, for example, use only 0.03 watt of so-called no-load energy. That won't save the planet by itself, but it easily beats the 0.5-watt maximum consumption that Energy Star requires and the average 1 watt that old block cell chargers use.

Beauty and the Geek

WOMEN IN ENGINEERING

The show's based on the Tufts University student club formed in 2000 by Karen Panetta, professor of electrical and computer engineering, which has since gone "viral" with the website www.nerdgirls.com, featuring a community forum, blog and curriculum site. The TV producers, who hope their program will attract more girls to engineering, scoff at the notion that their high-heeled glam nerds send an antifeminist message. As Panetta told Newsweek, "It's cool to be a nerd, and the girls are just embracing that."- TG

The show's based on the Tufts University student club formed in 2000 by Karen Panetta, professor of electrical and computer engineering, which has since gone "viral" with the website www.nerdgirls.com, featuring a community forum, blog and curriculum site. The TV producers, who hope their program will attract more girls to engineering, scoff at the notion that their high-heeled glam nerds send an antifeminist message. As Panetta told Newsweek, "It's cool to be a nerd, and the girls are just embracing that."- TG

Hand Soldering for Terminals Report Discusses the Importance of Soldering for Inspectability

DUBLIN, Ireland -- Research and Markets (http://www.researchandmarkets.com/research/960dfc/hand_soldering_for) has announced the addition of the "Hand Soldering for Terminals" report to their offering.

Train an unlimited number of students at your facility (Site License) or train throughout all your company facilities - even international sites (Global License). Includes Leader's Guide and Student Workbook.This package includes a training certificate, which is an ideal way to train and verify competency in key subject areas, like ESD Control, Lead Free Soldering, Component ID, Safety, and Acceptance Standards. These multi-media based resources include everything a trainer needs to instruct, test and certify that their operators have completed a course successfully. All students with a grade of 70% or better on the final examinations qualify for IPC Training Certification. Please see the sample certificate (.pdf) which allows for user-customization of student name, instructor, and date of completion. There is no expiration / renewal date for any Training Certification program, and they may be administered by anyone in your company.IPC's award-winning media training programs are produced by an in-house staff with over 25 years of industry experience - dedicated to the advancement of the electronics industry. Production costs are shared by IPC members within a not-for-profit environment. Cooperative development provides a low-cost option for in-house training - with world-class results.As an operator-level credential, Training Certification demonstrates mastery of the specific theory and knowledge contained in the course, as evidence of competency for ISO training requirements through an industry-developed training program. Training Certification does not qualify instructors or students to teach or interpret IPC specifications, or assure proficiency in the physical skills required to create products to the requirements of IPC specifications.Now you can purchase an online training tool especially designed to visually explain the tinning of soldering iron tips, stripping of insulated wire, as well as tinning the wire and cleaning the tip. Also demonstrates the proper method of attaching and soldering wires to turret terminals, cup terminals, bifurcated terminals, hook terminals, and pierced terminals. Discusses the importance of soldering for inspectability. Provides acceptance criteria for preferred solder joints, and demonstrates minimum / maximum conditions.Like all IPC Video / DVD, OVT and Computer-Based (CD) training programs, Training Certification is available for unlimited students per the particular licensing structure chosen. These media-based training solutions are created in cooperation with volunteer industry experts - to ensure technical accuracy - and are free from commercial bias.For more information visit http://www.researchandmarkets.com/research/960dfc/hand_soldering_for

For more information visit http://www.researchandmarkets.com/research/960dfc/hand_soldering_for

Repair

"Impact of PCB Pad Site Dress Methods on Pad Array Damage"

Authors: Laurence A. Harvilchuck, Brian Roggeman, Raiyo F. Aspandiar, James M. Wade and Gaurav Godbole; harvilch@uic.com.

Abstract: The thermal profile experienced by the pad array can have a profound impact on latent PCB damage, including the presence or absence of pad cratering. In this exercise, pad array damage is evaluated as a function of assembly preheating, pad site dress method, and applied desoldering temperature to offer insight when choosing between simple wick-and-iron solder removal and the more sophisticated vacuum-assisted solder scavenging methods. High-resolution 16-channel thermal profiles were obtained of both the wick-and-iron and vacuum scavenging operations across a single 34 mm square pad array of variable pitch on a 0.060" thick Pb-free ATX motherboard, revealing the nature of the thermal profile at the pad surface and through the board section to the cores. The shortcomings of current repair thermometry methods are also documented in the context of the impact of thermocouple placement on profile accuracy. Process variations inherent in the primarily manual wick-and-iron solder removal methods are readily apparent in the thermal profiles experienced by the pad array, while significantly reduced in the thermal profile generated by the vacuum scavenger. Wick-and-iron scavenging operations can subject the pad array to ramp rates approaching 200[degrees]C/sec. during the brief excursion above solder liquidus, while vacuum scavenging of the same site exhibited a maximum ramp rate nearly a full order of magnitude less, but of much greater times above liquidus. The impact of the thermal profile on the pad array was characterized by bump pull, pad fatigue and dye-and-pry techniques. Results from the present study showed no solder mask damage in the vicinity of the pad array resulted from any of the scavenging processes. Damage to innerlayer circuit board structures (per IPC-A-610) beneath the pad array was also absent in all cases under study. Use of substrate preheating during solder scavenging has a definite impact on reducing the substrate damage that can result from the repair of lead-free laminates. For both the wick-and-iron and vacuum methods, higher applied desoldering temperatures resulted in weaker pad adhesion than the corresponding solder removal operations at lower applied desoldering temperatures. Further pad fatigue testing of the same samples indicated this change in pad adhesion strength may be related to a change in the ductility of the laminate directly beneath the pad. The laminate choice also can have a significant impact. (SMTA Pan Pac Microelectronics Symposium, February 2009)

Processes for SnCuNi solder paste

The SnCuNi alloy (SCN) has been used in wave soldering applications because of its applicability in achieving acceptable soldering results and its lower rates of reaction with copper (used in PCBs and components) and iron (used as a based material in wave soldering equipment). The lack of precious metals like silver makes it less expensive, and the cosmetic appearance of the final joints is similar to that of SnPb joints; but these benefits are offset by its higher melting point temperature of 227[degrees]C in reflow applications. The higher melting point may necessitate reflow profiles with higher peak temperatures and/or longer time above liquidus (TAL) than that of SAC 305 to obtain complete and homogenous mixing of the paste deposits with the component lead/bump. Concerns such as possible damage of heat-sensitive components and joint reliability arise.

The test vehicle was a 0.062" thick, four-layer FR-4 PWB with Cu-OSP surface finish and non-solder mask-defined pads. Each board was populated with 16 256 I/O BGA-CSP components. The design of experiments included different peak temperatures (238[degrees]C and 248[degrees]C) and TAL (50 and 75 sec.). The corresponded TAL above 227[degrees]C was 30 and 50 sec., respectively. Levels for each factor were based on the current SAC 305 process window and recommendations from the SCN solder paste supplier. All boards were reflowed in air, and a small batch of pure SCN joints were reflowed in nitrogen (<100 ppm).An x-ray automatic program was used to inspect voiding. All solder joints from 12 boards with 16 components each were tested. The percentage of the single largest and overall voiding per solder ball was recorded. Results showed pure SCN shows fewer and smaller voids than the other two metal systems. However, the overall sizes of voids were insignificant. The overall sizes were on average less than 3.5% for the SAC and mixed systems and less than 1.2% for SCN systems. The size of these voids passed IPC-A-610D, which sets acceptance criteria for Class 1, 2 and 3 at a maximum 25% of the ball x-ray image area.ReferenceResults showed SAC, SCN, and mixed assemblies performed similarly in each group. The lowest cycles to fail were observed in groups 1 and 2, followed by groups 3 and 4. Further testing is planned to compare alloys in drop testing where the strain rate and stress levels are much higher.

Thermal cycling was performed with temperature ranges from 0[degrees] to 100[degrees]C, with a dwell time of 10 minutes and ramp rate of 10[degrees]C/s. The test was stopped at 1,686 cycles, when more than 50% failures were observed for each board. Table 1 shows the characteristic life (N63) and early failures (N01) for each case. It can be observed that SAC systems had on average better characteristic life followed by SCN (150 fewer cycles) and mixed (191 fewer cycles) systems. The data favor 238[degrees]C peak temperature, and there was not a significant difference between TAL.SCN shows promise as a replacement for SAC alloys for some reflow applications. SCN shows comparable performance in mechanical and thermal testing to SAC systems. Thermal cycling results suggest that the appropriate process window for the SCN system should have a peak temperature of 238[degrees]C and TAL of 50 sec. Thus, a typical SAC profile can be used to assemble pure SCN. At this temperature, heat-sensitive material suitable for Pb-free applications can be used without any problem. The use of a single alloy in wave and reflow processes will benefit the end-user by reducing complexity and cost.Early failures, which correspond to 1% of the failure data, showed a different trend. In this case, SAC systems had higher numbers of cycles-to-failed, followed by mixed (90 fewer cycles) and SCN (204 fewer cycles) systems. An improvement in early failures was observed when nitrogen was used in SCN joints, resulting in similar behavior to SAC systems.Good solder joint formation and collapse was observed on SCN and mixed assemblies when reflowed at 238[degrees]C and TAL of 75 sec. Microstructure analysis showed the main difference between these two systems was the presence of [Ag.sub.3]Sn intermetallic in the mixed joints. Another difference was the thickness of the intermetallic between the PCB and joint. A 60% thicker intermetallic was observed in the mixed system. This might be an indication that the nickel content inhibits the growth of CuSn intermetallic. (1)(1.) F. Song, J. Lo, J. Lam, T. Jiang and S.W.R. Lee, "A Comprehensive Parallel Study on the Board Level Reliability of SAC, SACX, and SCN Solders," Electronic Components and Technology Conference, May 2008.Vibration testing was performed on 12 boards reflowed in air. The goal was to excite the first resonance (bending movement) at relatively low amplitude to induce high cycle fatigue failures. The boards were mounted with standoffs at the four corners to an electrodynamic shaker. Failure data were divided into four groups depending on component location on the board because they experienced different stress levels. Figure 1 shows a schematic of the board with its groups. Two failure modes were observed: pad cratering (groups 1 and 2) and solder fatigue (groups 3 and 4).Ursula Marquez de Tion is a process and research engineer at Vitronics Soltec, based in the Unovis SMT Lab (vitronics-soltec.com); umarquez@vsww.com.Mixed assemblies, which are mainly SAC alloy (ratio sphere/paste = 3.18), were affected by the content of silver and nickel, which results in a decrease in the characteristic life when compared to pure SAC, but were comparable to SCN assemblies. In general, all three systems performed similarly within an appropriate process window, but more experiments are needed to support this conclusion.[FIGURE 1 OMITTED]

Ursula Marquez de Tion is a process and research engineer at Vitronics Soltec, based in the Unovis SMT Lab (vitronics-soltec.com); umarquez@vsww.com.

Bruker Elemental Announces Q2 ION Ultra-Compact Best-in-Class Spark-OES Metals Analyzer with Unique Analytical Capabilities

BILLERICA, Mass. -- Bruker Elemental today announces the launch of the all-new Q2 ION™, an ultra-compact spark optical emission spectrometer (OES) for metals analysis. The Q2 ION is a true multi-matrix system for comprehensive incoming material inspection and quality assurance of metal alloys. Its primary applications and metal matrices include copper, aluminum and iron analysis at smaller foundries, inspection companies, metal recycling and metal fabricators.

The addition of the Q2 ION expands Bruker Elemental’s range of metal analysis systems even further. Mr. Andreas Kunz, Sales Director for Bruker Elemental, commented: “We can now offer an even wider selection of metal analysis solutions to our customers. We believe the Q2 ION represents a breakthrough in best-in-class performance and analytical capabilities for an ultra-compact system with a very attractive price/performance ratio.”For information about Bruker AXS - Elemental and Bruker Corporation (NASDAQ: BRKR), please visit www.bruker.comFor More Information:For more information on Q2 ION, please visit www.bruker-elemental.comHigh quality ultraviolet (UV) OES analysis in a compact system is an innovative feature that represents important progress for ultra-compact spark-OES systems. UV-OES enables Q2 ION customers to analyze metals for important additional elements, such as carbon, phosphorus, sulfur and even nitrogen for duplex steels. Other key features like high analytical stability through patented active ambient compensation, standard-less calibration, proprietary ClearSpectrum™ algorithms, low argon consumption and minimal maintenance give Q2 ION users additional confidence in its reliable analytical results at very low operating costs.The small benchtop Q2 ION system incorporates numerous proprietary innovations. It was designed for simplified operation, minimized maintenance and short analysis times while achieving best-in-class analytical performance. The Q2 ION’s compact size and rapid start-up routine even allows the unit to be portable, making it complementary to Bruker Elemental handheld XRF systems.Photos/Multimedia Gallery Available: http://www.businesswire.com/cgi-bin/mmg.cgi?eid=6196805&lang=en

Photos/Multimedia Gallery Available: http://www.businesswire.com/cgi-bin/mmg.cgi?eid=6196805&lang=en

Tomb 100 at Cabezo Lucero: new light on goldworking in fourth-century BC Iberia

Introduction

[FIGURE 2 OMITTED]Two other key objects take the form of hollow, bronze cones of 100mm and 180mm in length, each with a tine hole in the end (Figure 5). These have been identified as drawing plates for the manufacture of threads (Uroz Rodriguez 2006: 43-44, fig. 16). Computed Tomography images generated as part of our study have revealed that the original section drawings of these tools are incorrect (Figure 6). The walls of the cones are thinner than shown in the original diagrams, and the small hole at the end was approached via an interior step. This complex internal design, along with the shape and material of these two objects (drawing plates are usually flat, iron objects) does not correspond to the production of threads. Rather, these cones would have been used to produce a high pressure stream of air. Air would have been introduced at the wider end and have escaped at a greater pressure through the tine hole. Similar blowpipes are still used by some jewellers today. Modern blowpipes have the same configuration as those found in Tomb 100, the only difference being that the end of modern brass cones are bent at 90[degrees] to provide the jeweller a better view of the work area (Untracht 1987:410-11). It seems highly likely that these two objects are blowpipes for brazing gold.Shaping. once weighed and cut, the raw material was melted in a crucible. The ingot obtained was then beaten with a hammer until a sheet of the desired thickness was obtained. This stage is represented by the larger tools found, including iron tongs for the handling of crucibles, and two anvils. One of the latter, made of iron, is poorly preserved; the other, in bronze, has a circular work surface 47mm in diameter that shows signs of deformation owing to prolonged use (Figure 2b). This group of tools also includes a bronze socketed hammer (Figure 2c), the head of which measures 104 x 128mm. It is poorly preserved having been found within an encrusted mass of highly oxidised iron objects. Finally, there is a small saw that may have been used in some way for the transformation of the raw material.The goldwork of Iberia in the first millennium BC is justly famous (Figure 1). It is characterised by brazing, filigree and granulation--the 'Mediterranean trio.' These techniques can be traced back to 2500 BC in the Middle East (Wolters 1983), but reached technical and iconographic excellence during the Iron Age of Mediterranean Europe. Brazing is the permanent metallurgical joining of metals to form a single more complex, more voluminous or hollow object, using high temperatures and a filler alloy (solder). This method lies at the heart of filigree and granulation, two of the oldest jewellery-making techniques, which involve the use of tine threads and tiny gold drops respectively, brazed to a laminar base to form ornamental patterns. The grave goods from Tomb 100 at the Iberian necropolis of Cabezo Lucero throw new light on goldworking processes in the mid fourth century BC.The materials found in Tomb 100 reflect ali of the stages of jewellery production, from procuring the raw material, to its shaping, ornamentation, and finally joining.[FIGURE 4 OMITTED]A goldsmith's toolkitThe necropolis of Cabezo Lucero (Guardamar de Segura, Alicante), lies in the lower valley of the River Segura, 6km from its current mouth. The corresponding fortified settlement is approximately 200m to the north and, so far, has not yet been fully excavated. The necropolis covers an area of approximately 4200[m.sup.2] and dates from the early fifth century to the early fourth century BC. Tomb 100 contained the remains of an adult warrior. In addition to his standard military equipment the tomb contained a complete goldsmith's toolkit including some 50 specialised instruments. This exceptional find was recovered during excavation in 1986 but has remained unstudied until the present. Some of the instruments went on public display in 1992 as part of a small exhibition at the Museo Arqueologico de Alicante (Llobregat 1992), and at an exhibition (The Iberians) held at the Grand Palais de Paris (Aranegui-Gasco et al. 1997: nos. 69-78). Recently, 31 bronze dies--part of the set of tools discovered--were the subject of a monograph focusing on their iconography (Uroz Rodriguez 2006) and an article reflecting on the status of artisans in Iberian society (Graells 2007). Some of the grave goods found in Tomb 100 are currently on display at the new Museo Arqueologico de Alicante.A mouth blowpipe has a double purpose: first, to raise the temperature of a heat source; and second, to direct that heat towards a desired point. The heat source could be a simple oil or animal fat lamp, the flames of which can reach around 1000[degrees]C. Blowing air across the flame allows even higher temperatures to be reached while channelling that heat in a specific direction. Depending on the intensity of the airflow and the combustion zone, either an oxidising or a reducing flame can be directed at the desired point--the latter is required for brazing in jewellery-making. The heated metal changes in colour depending on the temperature reached, from dark red to orange to white, facilitating the visual calculation of the temperature attained. In this way the melting point of part of a small metallic mass can be reached without affecting the surrounding area, allowing a filling gold alloy to melt in between the two pieces effectively fusing them together. The phase diagrams of the AuAg-Cu system (Prince 1988), which show the melting points of the different combinations possible (ranging from 800[degrees]C for alloys with the lowest melting points to 1064[degrees]C for pure gold), indicate there to be ample margin for the efficient use of mouth blowpipes in jewellery manufacture. In addition, the control gained over the metal's temperature obtained by observing the change in colour is better than that possible when placing the entire object in a furnace.Procurement: two balance plates have been identified; both are now highly deteriorated and fragmented (Figure 2a). One, about 40mm in diameter, is not perforated; the other, 72mm in diameter, has a central perforation. This weighing system also includes a disc-shaped weight with an unusual perforation and four incised points (Figure 2a). Its current weight is 9.36g.The joins made by brazing performed with a mouth blowpipe cannot be distinguished from those involving brazing performed in a furnace and, until now, mouth blowpipes have never been identified as such in the archaeological record. Apart from the shape of the objects themselves, is there any evidence that could support the proposed interpretation of the two bronze cones from Tomb 100 as mouth blowpipes?Our purpose here is to describe this remarkable assemblage and demonstrate its contribution towards understanding the techniques and context of goldworking in the Mediterranean Iron Age.[FIGURE 1 OMITTED][FIGURE 3 OMITTED]Use of the brazing blowpipesJoining: complex jewellery was made by putting together independently manufactured pieces, or decorating them by affixing filigree (tine wire) or granules (gold droplets). Brazing was required to fix the different elements together. Tools connected with these operations are rare but can be identified within the assemblage. One of the grave goods was a pair of bronze tweezers originally classified as belonging to the warrior's personal effects (Uroz Rodriguez 2006: 41) (Figure 4c). However, Iberian men's tweezers had straight ends, appropriate for looking after the beard, but the tweezers of Tomb 100 have pointed ends. It is therefore proposed that rather than being a masculine status symbol, these tweezers are a tool for holding and arranging threads of filigree and granulation spheres on the surface of a worked sheet.

A mouth blowpipe has a double purpose: first, to raise the temperature of a heat source; and second, to direct that heat towards a desired point. The heat source could be a simple oil or animal fat lamp, the flames of which can reach around 1000[degrees]C. Blowing air across the flame allows even higher temperatures to be reached while channelling that heat in a specific direction. Depending on the intensity of the airflow and the combustion zone, either an oxidising or a reducing flame can be directed at the desired point--the latter is required for brazing in jewellery-making. The heated metal changes in colour depending on the temperature reached, from dark red to orange to white, facilitating the visual calculation of the temperature attained. In this way the melting point of part of a small metallic mass can be reached without affecting the surrounding area, allowing a filling gold alloy to melt in between the two pieces effectively fusing them together. The phase diagrams of the AuAg-Cu system (Prince 1988), which show the melting points of the different combinations possible (ranging from 800[degrees]C for alloys with the lowest melting points to 1064[degrees]C for pure gold), indicate there to be ample margin for the efficient use of mouth blowpipes in jewellery manufacture. In addition, the control gained over the metal's temperature obtained by observing the change in colour is better than that possible when placing the entire object in a furnace.

Automated solder paste inspection: a new look at stencils: what has driven stencil verification to the brink of extinction?

With all the focus on stencil printing to reduce defects and improve profits, electronics assemblers continually invest in custom tooling, new and improved stencil manufacturing methods or materials, high-capability printers, super accurate inspection machines, fancy statistical software and expert training. Ironically, many of the same high-tech assemblers that pour money into ensuring the robustness of their print processes actually skip the simple step of stencil verification, upon receipt.

Au.: SPI systems can be used for a variety of other stencil-related tasks, including vendor qualification, aperture design guideline assessment, and foil material evaluation.Why has stencil verification become optional and what drove it to the brink of extinction? Likely a combination of efficiency and economics. Basic stencil verification procedures use a negative image of the stencil pattern, a light source and a human to verify the presence of all desired apertures and measure a few of them. As aperture counts increase and sizes decrease, the efficacy of human inspection techniques becomes questionable, and coordinate measurement machines (CMMs) are needed to meet measurement speed and accuracy requirements.Ray Whittier of Vicor (vicr.com) demonstrates how he uses his white light SPI system to verify new stencils before putting them into production: The official ISO 9001 documented procedure involves printing two dummy boards and inspecting them with the SPI machine. If the machine passes the two prints, the data are exported for further analysis. If the machine fails either print, the stencil is inspected for manufacturing defects. If no obvious defects are found, the machine setups are checked and two more dummy prints are run. If the prints pass on the second try, the data are exported for analysis. If they fail on the second try, the process is stopped and the stencil is held for further review.[FIGURE 1 OMITTED]The machines that laser-cut SMT stencils use gantries and motion controls similar to those in pick-and-place machines. Moving parts wear, and machines drift out of spec if they are not regularly maintained and calibrated. The opportunity to create apertures that are out of position, incompletely cut, or obstructed with slag happens every day. And while electro-formed foils might eliminate the stencil cutter as a variable, they introduce other factors: their size and positional accuracy are only as good as the artwork used to form them, which depends on the artwork's photoplotter - another machine full of moving parts. Additionally, the nature of the plating process subjects these foils to regular variations in thickness that introduce error into area ratio estimates.What's the probability of getting a stencil with apertures out of spec? Assume the stencil vendor has the highly touted Six Sigma quality in his process. Most are in the sub 5-Sigma range, assuming Six Sigma makes for conservative estimates and easy math. Allowing for the 1.5[SIGMA], shift, the supplier creates 3.4 defects per million opportunities. Consider stencils with 10,000 apertures: 100 stencils represent 1,000,000 opportunities. Even at a Six Sigma level, between 3 and 4 of each 100 stencils will have a manufacturing defect. Think about how many stencils are regularly used in production. How many defects are out there right now, waiting to get installed in an assembly printing process?The process is flow-charted in FIGURE 2. The data analysis involves sampling volume readings from the more difficult to print devices, such as SOT883s, SOD882s and [mu]BGAs, as well as for two passive devices, usually 0201s and 0402s. For each component type, Cpks are calculated using control limits of [ or -]50% of theoretical volumes or slightly tighter. All Cpks must be greater than 1.33 for the stencil to be acceptable for production use. If any of the Cpks fall short of the 4-Sigma mark, the machine setups are checked and two more test prints are run. If they again fail to meet the mark, the stencil is held for further review. If the print quality is acceptable, the data are archived and the stencil placed into production.CHRYS SHEA is founder of Shea Engineering Services (sheaengineering.com); chrys@sheaengineering.com.[FIGURE 2 OMITTED]It takes about 10 min. on the assembly line to get the data, and another 10 min. to crunch the numbers. In addition to being faster and easier than measuring apertures, the SPI method captures process outputs instead of inputs. Where industry used to be limited to measuring the size and position of the aperture and using it as an indicator of a stencil's performance, we can now measure what really matters: the characteristics of the individual deposits on the PWB. That's where the rubber meets the road, or, specifically, where the solder paste meets the board.Many assemblers have foisted responsibility for automated inspection and verification onto the stencil vendors, referring to them as "qualified" or "certified" suppliers. In essence, they have placed the fox in charge of the henhouse on a portion of their most critical SMT process. While this practice might look good on paper, it's rife with potential to backfire and ultimately costs the assembler more money than it saves.

CHRYS SHEA is founder of Shea Engineering Services (sheaengineering.com); chrys@sheaengineering.com.

Soldering iron tip care: pick the right tips, and don't overheat the joint

THE ABILITY TO efficiently manufacture a product has driven the electronics industry toward automated processes and streamlined production facilities. Despite this, the need for hand-soldering operations remains an integral part of most manufacturing processes. Whether it is the need to attach a large connector, conduct a field modification, or to rework a noncompliant item, hand-soldering operations require personnel with the proper skills to complete the job. The use of proper, well-maintained equipment is paramount to completing the task in a timely manner, while maintaining a high level of quality.

[FIGURE 1 OMITTED]* First, wipe the tip on a clean, slightly damp sponge to remove oxidation and excess solder. A coiled brass wire pad can also be used to remove excess solder.* Use only sulfur-free sponges intended for electronics applications.* First, select a tip that is the proper size and geometry for the connection to be soldered. (Match the width of the tip to the diameter of the pad.) While this may seem like common sense, it is frequently the most overlooked practice. It is not uncommon that a technician will choose a tip that is too small and try to compensate for poor heat transfer by increasing the iron temperature. The problem then becomes twofold because the area is insufficient for adequate heat transfer, and oxidation increases with the higher tip temperature. Use the correct tip size and temperature to yield better results.* Select the lowest tip temperature needed to facilitate solder reflow. The correct temperature depends on the type of solder alloy being used. Pb-free alloys have higher melting points than SnPb alloys, and often have a frosted or grainy appearance (in the final connection). A grainy appearance on a SnPb connection is a clear indication that the tip temperature is too high. If a connection is being made on a multilayer board with an internal ground plane, the ground plane acts as a heat sink. Auxiliary heating is needed to overcome the heat sink effects.ACI TECHNOLOGIES INC. (aciusa.org) is the National Center of Excellence in Electronics Manufacturing, specializing in manufacturing services, IPC standards and manufacturing training, failure analysis and other analytical services. This column appears monthly.* Replace sponges at regular intervals when they become dirty. Replacement sponges are inexpensive, and this simple practice will help avoid introducing contaminants.Proper maintenance of equipment is often the most overlooked problem in hand-soldering operations. A few easy and repeatable practices regarding soldering iron tip care can eliminate a wide variety of issues. Proper tip care will extend the life of the tip and cut down on the need to frequently replace oxidized or pitted tips that are no longer usable.* When soldering, do not apply downward pressure on the joint being soldered. Simply rest the tip of the iron on the joint to help establish a heat bridge. (A small bead of solder on the tip will also aid in forming a heat bridge.) Downward pressure will not aid in solder reflow. It will, however, cause undesired mechanical stress on the connection area and may result in lifting the pad.* Finally, always turn off equipment when not in use, and never use tips for purposes other than intended. Breaks or cracks in the plating that result from improper tip use will drastically reduce its lifespan, or at the very least, interfere with its heat transfer capabilities.* "Idle the tip!" This term refers to the practice of coating the tip with a thin film of solder before returning it to its holder. This thin film of solder will be oxidized instead of the surface of the tip, dramatically extending the life of the tip.* The solder should be fed to the connection, not to the tip. Once a heat bridge is established, the connection will melt the solder and the solder wire should be moved around the connection to ensure adequate coverage.The goal of any high-quality soldered joint is the formation of a good intermetallic bond (FIGURE 1) between the solder alloy and connection contact area (e.g., the wire or component lead, and the land, pad, or terminal). The following practices will help ensure acceptable soldered connections and prolong the life of the equipment used in common hand-soldering operations:

ACI TECHNOLOGIES INC. (aciusa.org) is the National Center of Excellence in Electronics Manufacturing, specializing in manufacturing services, IPC standards and manufacturing training, failure analysis and other analytical services. This column appears monthly.

Home Made Solar Panels Save Big Money

Over the last couple of years solar power generators have become more preferred due to our hard economical times. Thousands of solar energy systems are being installed domestically every day. Not only people lower their energy bills but solar panels are also safe for the environment. Read on if you have an interest in making your own home made solar panels that may significantly cut back your energy bills month after month.

Depending on the size of your home and how much energy you need, you might want to make more than one home made solar panel.Normally a ready to go solar cell costs up to some thousands and I'm sure not everybody wants to make such an investment. This is the reason why more folks are deciding to build their own solar cells right in their own backyard.No matter how many home made solar panels you need to make, building them on your own will drastically reduce the costs comparing to what you would pay for some pre-made ones. And if you're a bit lucky you might be able to get some of the materials at a local garage sale. You can save more than 80% on your energy bills each year by making your own solar panels.If you decide to begin building you own home made solar panels you want to have all the needed parts such as photovoltaic cells, copper wire, boards, glass and all the other needed tools including a soldering iron that heats up fast. You want take care as the markets are full of non-quality solar cells, the most cost-effective and best ones can be found online. Basically you won't be spending more than one hundred and fifty to two hundred dollars altogether. Imagine that a solar panel normally costs around $3000.Learn about http://www.homemadesolarpanelsreview.net/ and how to reduce your energy bills by 80% or more. Visit http://www.homemadesolarpanelsreview.net/ to learn more now!

Learn about http://www.homemadesolarpanelsreview.net/ and how to reduce your energy bills by 80% or more. Visit http://www.homemadesolarpanelsreview.net/ to learn more now!

AIM sets its targets: the world's unsung solder supplier is building a business for the ages

A few minutes before noon, the cafeteria starts to fill with dozens of workers, blue collar and white, some in business casual wear, others in their factory blues. The volume begins to rise, a cacophony of sounds and languages, English and French, spoken in an endless variety of flavors.

R&D is performed in Montreal, Rhode Island and China, while tech support centers are based in India, Singapore, Philippines, Mexico, North America, Europe and China. In Montreal, AIM maintains separate labs for various types of paste, cored wire and testing, and each chemist has their own specialty. (Similar labs are set up in Mexico and China.) AIM also provides adhesives, but they are not big sellers.The ISO 9001 registered, ISO 17025 compliant Quality Assurance lab is bright and clean, with a new Thermo Fisher Quant x-ray and a Thermo Electron 3460 metals analyzer, among other gear. AIM performs arc-spark testing to check for all standard impurities, with tests run to IPC specifications and multiple others. More than 1,000 samples per month are analyzed. Montreal is one of three company labs; others are in China and Mexico.All paste is made to order. Inventories are kept low, with a few emergency stocks of common types. Prior to shipping, every package is scanned with an XRF to ensure it's the right formulation.The liquid flux is made in an explosion-free room. All flux chemistry is designed and made in Montreal. (Chemistry is the main expense in R&D; the cost to develop an alloy is relatively low. Changing it, however, is a long, drawn-out process, Selig allows.) We also see a small SMT epoxy room with a mill for different pigments.AIM uses standard blenders with automatic controls designed to be programmed, but that cannot be adjusted by operators. All paste is made to order, and alloys and formulas tend to be the outgrowth of face-to-face discussions between Seelig and AIM's marketing staff with OEMs and EMS firms. Inventories are kept low, with a few emergency stocks of common types.We pass the metal castings area, where three continuous casters labor in a humidity- and temperature-controlled room pressurized for fume extraction.The applications lab features a DEK printer, Quad placement machine, Heller 1500 reflow oven, CRT CRX-1000 x-ray and Koh Young 3020T SPI. Tests are conducted using electroform, lasercut and nanostencils.Founded in 1936 as American Iron and Metal, the company has its roots in metals recycling and reclaim. Now a subsidiary, AIM's solders business was formed 22 years ago, and was spun out in 2007. It maintains the same ownership as AIM, though each unit is a separate legal entity. Ricky Black, the 40-something grandson of the founder, heads AIM Metals and Alloys, which has manufacturing sites in Canada, China, the US, Mexico, Hong Kong, Spain, Italy and Australia.From there, we walk past several drums of butyl carbide to the lab where AIM makes its paste medium. Using dedicated mixers for water-soluble, cored wire and no-clean, operators weigh the bucket to get the precise weight; even a slight deviation could ruin a batch. The powder press is truly impressive: Molten metal pours into a dish; solder falls into the chamber, then onto a screen, then to the atomizer. It's a three-story process. An oxide "skin" forms; a thin skin is needed on every layer. Powder is exposed to atmosphere for about one hour, then vacuum packed with gas and labeled. Yields are about 70%, very high for electronics grade solders. Paste is made in a 45% RH dry room. Each lot is tested for corrosion, electromigration, thermal cycling and SIR, among others. "Everything has to be tested," Seelig notes. While AIM is a leading supplier of bar solder, many would be surprised at the volume of its paste business. Combined, the total revenues from the two segments easily place AIM among the five largest electronics solder suppliers in the world. "The ratio of bar to paste is lower than five years ago. The industry doesn't realize how much we do in paste. Maybe it goes with our understated personalities," deadpans Black.Supply Local, Supply GlobalThe channel plays a large role in the company's success, Black says. "You need to have the distributors to make sales. Customer orders tend to ebb and flow, and they need quick deliveries. [Solder] freight is high relative to the value and margin of the product, so it forces you to have local stock." AIM prefers distributors that are hands-on and seen as adding value with technical expertise. In Europe, South America and Asia, it tends to use a single distributor per country.The plant tour begins in the core wire area. There, workers start with 15mm or smaller wire, which is then reduced in diameter using an extrusion press (AIM has five on site). Core wire operations also take place in Mexico, China and Europe. (Because of the large volumes, AIM makes core wire in fewer places than other solder types.)Over the past 10 years, supplying solder has been a tricky business. The RoHS Directive permanently rerouted the industry direction, causing a disruption in pricing that is felt to this day. Solder is, of course, one of the lower items on the bill of materials totem pole. Unlike most raw material prices, precious metals are in a sustained period of inflation. Despite this - because of it, in fact - solder vendors do not capitalize. Indeed, most find the higher metal prices make their market more treacherous: Customers sometimes balk at paying more; vendors pay cash for raw metal, and it may take 100 days or more to turn that metal into solder and get paid by a customer, so the higher raw metal prices increase the supplier's risk and cost of doing business; the cost to reclaim dross increases.Within an hour, the room falls quiet again as the staff resumes its roles inside the vast manufacturing facility that doubles as the global headquarters of AIM.The Montreal headquarters is situated on a massive campus that stretches more than two miles from front to back, where a set of rail sidings slides right up to the door. While Montreal is considered home to the company's extensive bar, wire and solder paste operations, AIM also maintains mixing and blending operations in the US and Hong Kong.With 12 sites up and running, AIM doesn't see an end yet in sight. Black says he's "almost convinced" more facilities will be erected, although he doesn't yet know where. "It also depends on what the market wants to consume," Seelig adds, pointing to the logistics of the supply chain. "We can't ship alcohol-based or water-based flux or bar solder via air freight."The melting pot culture of AIM is probably the least well-known aspect of what might be the least well-known large solder supplier in the electronics industry today.Heading up the technology side is Karl Seelig, a 30-year veteran of electronics materials. Seelig came aboard in 1988 to help launch the electronics solders business. His imprint on the company's solder product lines can be seen everywhere, from the formulations to the equipment used to make the powders.AIM not only does a lot of "things" to the metal, it does those things in a lot of places. Perhaps owing to its aforementioned understated approach, AIM is considerably larger than most in the industry realize. Its breadth is a byproduct of its supply strategy, which assumes even larger accounts want local service. "If we didn't supply locally, we wouldn't be able to supply globally. It's a consumable product; people run out," Black explains. "The way to do that is to have your own facilities."Most customers look at particle distribution, so that's a standard item for the lab review. In-house software assesses some 45,000 particles, checking width, length, diameter and so on. Every tank is sampled multiple times; then a chemical analysis is performed to ensure the barrel is satisfactory. All electronics grade solder is made from virgin metal. Reclaimed material is reserved for industrial use only.

The channel plays a large role in the company's success, Black says. "You need to have the distributors to make sales. Customer orders tend to ebb and flow, and they need quick deliveries. [Solder] freight is high relative to the value and margin of the product, so it forces you to have local stock." AIM prefers distributors that are hands-on and seen as adding value with technical expertise. In Europe, South America and Asia, it tends to use a single distributor per country.