Since the electronics industry moved to lead-free solders that typically have a tin content of more than 95% there has been
concern about the possibility of circuit malfunctions due to whisker growth. It is now generally accepted that whisker growth is a response to compressive stress within the tin crystal and the challenge is to identify and eliminate or at least minimize the
processes that can generate such stress. Corrosion has been identified as one source of that stress and in this paper the
authors report a study directed at identifying the relationship between the extent of corrosion and the concomitant whisker
growth. Printed circuit coupons with an OSP finish were soldered with SAC305 solder using wave,reflow,and hand soldering methods with flux formulations typical of current commercial practice. These coupons,soldered but without components,were exposed to three environments for up to 3000 hours: 40°C/95%RH,60°C/90%RH and 85°C/85%RH. As well as recording the location of whiskers,their density,and length as a function of time,the extent of corrosion of the solder after 1000,2000 and 3000 hours was measured by cross-sectioning. The ultimate determinant of whether or not whiskers appeared was the environment to which the test pieces were exposed. The highest incidence (whiskers per unit area),fastest growth rate,and greatest length occurred on test pieces exposed to 85°C/85% RH. Whiskers occurred later,at a lower
incidence,and grew more slowly at 60°C/95% RH but even after 3000 hours no whiskers were detected on test pieces exposed to 40°C/95% RH. The incidence and growth rate of whiskers was found to vary with the soldering method and the type of flux. Whisker growth occurred earliest on the test pieces that had been wave soldered. Geometry was found to have an effect with the concavity created on the edges of traces by the etching process apparently acting to focus the compressive stress and accelerate whisker growth in that area. The authors relate these trends in whisker growth to observations of the concurrent corrosion of the solder which in turn is related to the type of flux used. A preliminary conclusion is that the likelihood of whisker growth occurring on lead-free assemblies soldered using no-clean technologies can be significantly reduced by using a flux which does not promote the sort of corrosion that can generate compressive stress in the solder.

The objective of this study is to evaluate conformal coatings for mitigation of tin whisker growth. The conformal coatings chosen for the experiment are acrylic,polyurethane and parylene. The coatings were applied in thicknesses ranging from 0.5 to 3.0 mils on 198 bright tin plated coupons with a base metal of either Copper C110 or Alloy 42. Prior to coating,light scratches were applied to a portion of the coupons,and a second fraction of the coupons were bent at 45° angles to provide sources of stress thought to be a possible initiating factor in tin whisker growth. The coupons have been subjected to an environment of 50°C with 50% relative humidity for over five years. Throughout the trial period,the samples were inspected by both optical and scanning electron microscopy for tin whisker formation and penetration out of the coatings by tin whiskers. Tin whiskers were observed on each coupon included in the test,with stressed regions of the bent samples demonstrating significantly higher tin whisker densities. In addition,the Alloy 42 base metal samples showed greater tin
whisker densities than the Copper C110 base metal samples. There were no observable instances of tin whisker penetration out of the coatings or tenting of the conformal coat materials for any of the non-stressed test coupons. The stressed coupons demonstrated tin whisker protrusion of the 1.0mil thick acrylic and polyurethane coatings for the Alloy 42 base metal samples. The greater thickness coatings (minimum of 2.0mils) did not demonstrate tenting or tin whisker protrusion. This paper will also include materials properties of the conformal coatings examined along with appropriate processing techniques in order to better understand the role of the coatings in tin whisker mitigation.

Counterfeiting is clearly a growing problem in many industries,including electronics,around the world. As the financial impact of counterfeiting has grown over the years,so has the attention that has been devoted to it by everyone from packaging,assembly,and test engineers to procurement and quality personnel. Today,many feel that counterfeiting is the number one issue that threatens the electronics supply chain.

•Background information
•Scope of the problem
–Anecdotal
–Study by International Chamber of Commerce
–Recent study US Dept of Commerce
•What to do about it ?
–“Findings” and “Best Practices”
•Types of strategies

Wave soldering is a mature manufacturing process that metallurgically joins component and PWB termination features by
passing them together across the flowing surface of a molten solder reservoir. During this exposure,copper from through holes,surface mount lands,and component leads,continually dissolves into the molten solder. Unless the solder in the reservoir is Regularly changed,the dissolved copper eventually reaches a point of saturation,and orthorhombic Cu6Sn5 crystals begin to precipitate out of the molten solder,causing it to become gritty and sluggish. Solder drawn from such a saturated wave solder pot can solidify into joints whose surface finish exhibits many needle like metallic protrusions. These protrusions are in fact orthorhombic Cu6Sn5 crystals. Recently,BAE Systems has determined that this same phenomenon is responsible for the formation of nearly invisible intermetallic microbridges between fine pitch surface mount component leads. They form when a solder bridge from a surface mount paste reflow operation is hand reworked with a soldering iron and copper desoldering braid. This paper documents several short circuit failures caused by this phenomenon,the investigation that identified the root cause of the problem,and the rework techniques that can be used to prevent its
occurrence.

Mechanical shock testing was conducted by Boeing Research and Technology (Seattle) for the NASA-DoD Lead-Free Electronics Solder Project. This project is follow-on to the Joint Council on Aging Aircraft/Joint Group on Pollution Prevention (JCAA/JG-PP) Lead-Free Solder Project which was the first group to test the reliability of lead-free solder joints against the requirements of the aerospace/military community.
Twenty one test vehicles were subjected to the shock test conditions (in four batches). The Shock Response Spectrum (SRS)
input was increased during the test after every 100 shock pulses in an effort to fail as many components as possible within the
time allotted for the test.
The solder joints on the components were electrically monitored using event detectors and any solder joint failures were recorded on a Lab view-based data collection system. The number of shocks required to fail a given component attached with SnPb solder was then compared to the number of shocks required to fail the same component attached with lead-free solder.
A complete modal analysis was conducted on one test vehicle using a laser vibrometer system which measured velocities,accelerations,and displacements at one hundred points. The laser vibrometer data was used to determine the frequencies of the major modes of the test vehicle and the shapes of the modes. In addition,laser vibrometer data collected during the mechanical shock test was used to calculate the strains generated (using custom software).
After completion of the testing,all of the test vehicles were visually inspected and cross sections were made. Broken component leads and other unwanted failure modes were documented.

This paper is an examination of the process feasibility,solder joint reliability,and materials/process compatibility of a dippable solder paste material for an area array component rework/repair process. The Ball Grid Array (BGA) components in this investigation were reworked according to typical production procedures and a new dipping procedure using the AirVac Onyx 29 BGA rework machine. The components were tested for thermal cycle solder joint reliability and flux process compatibility. The thermal cycle and flux process compatibility test results demonstrated that the dippable solder paste material and BGA rework process were acceptable for IPC Class 3 High Performance products.

This paper details a break-through technology for automatic test equipment (ATE) fixtures. These new fixtures address the current market needs of - "faster,cheaper,and smaller". The new fixture design decreases typical fixture turn times to between 2 and 4 days on average. Fixture prices are also significantly reduced by approximately 50% to 60%. And,the technology also provides improved pointing accuracy,for testing targets down to 0.015" diameter targets on a 0.5 mm pitch. This paper will detail how these advances were achieved and discuss the technology in detail.

The electronics assembly industry has long wished for and made great advancements toward developing a true,closed-loop automatic print verification and process monitoring technology. While significant progress has been made,many hurdles remain to be overcome. Recent developments in on-board inspection technology,however,have pushed the “lights-out” printing concept even closer to becoming reality.
This paper will present data on a novel print verification technology that uses a series of sensors to capture the full board image,analyze the data and accept or reject the print – all in real time. The system compares the actual print to that of the PCB?s Gerber data to assess accuracy and paste presence/absence,among other print components,and can be integrated with additional machine performance tools to make the printing platform even more intuitive. By enabling the print and inspection processes to run concurrently and deliver 100% verification at full line speed,production rates can be maintained and throughput is exponentially improved. The technology can have a profound impact on cost reduction,as faulty boards are isolated and removed from the line at the printing phase instead of traveling fully downstream to final assembly. Additionally,integrating such high-speed and powerful inspection technology onto the printing system eliminates the requirement for a dedicated,in-line SPI machine,and saves even more resource including training and floor space.
The inspection component of this next-generation technology can also be combined with verification and traceability tools to confirm all print inputs and outputs and trace materials,boards and processes to origination. This is a requirement for many high-value applications such as medical,defense and aerospace and has tremendous benefit for traditional EMS and OEM assembly operations as well.
These details along with future closed-loop printing platform developments will be presented.

Accuracy in solder balls and joint void detection is very important. If voids are incorrectly identified,board yield will be affected by incorrect scrapping and rework. Voids are difficult to detect using manual inspection alone. One current solution to make voids visible involves the use of a 2D x-ray system to image the boards. Some existing x-ray inspection systems have void detection algorithms that require the use of intensive,time consuming,fine tuning operations. These algorithms typically use two different global thresholds to segment the balls or joints and the voids using operator trial and error. However,using global thresholding over the entire image is invalidated due to varying image brightness. Existing methods also eliminate balls or joints that are partially occluded by other components due to difficulties in segmentation. The results are that many voids that can be easily observed by the human eye are missed by the existing automated methods.
In this paper,a robust,accurate,and automatic void detection algorithm is proposed. The method is applicable to either Pre SMT solder balls or post SMT solder joints. For simplicity,the term balls will be used throughout the document. The proposed method is able to detect voids with different sizes inside the solder balls,including the ones that are occluded by board components and under different brightness conditions. The proposed method consists of segmenting individual balls,extracting occluded balls,and segmenting voids inside the solder balls. The segmentation of the individual balls is achieved by using the proposed histogram and morphological based segmentation method. A voting procedure is used to segment the occluded balls where the pixels inside the occluded area are checked to obtain candidate pixels representing the occluded joint’s or ball’s centroids. An independent edge detection procedure is used to get candidate voids inside individual balls. Mathematical morphology operations are used to locate all possible valid voids and remove non-void areas. The proposed algorithm was applied to 3 different Intel products. The results of the proposed method were compared to the results obtained by an automated algorithm in an existing state-of-the-art 2D x-ray inspection system,the results obtained by trained operators from 2D x-ray images,and the results obtained by trained operators from 3D CT scan images. The results (pre SMT solder balls) show that the proposed method is capable of successfully locating all possible visible voids inside the solder ball even the ones that were missed by using other methods as well as those that are hard to see by the human eye. The results also
show a high correlation with ground-truth data obtained from 3D CT scan and experienced operators. The algorithm is fully
automated,benefits the manufacturing process by reducing operator effort and provides a cost effective solution to improve
output quality.