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.

The effectiveness of cleaning stencils and misprinted/dirty printed circuit boards can be effectively monitored. This can be done by washing known clean circuit boards and then checking to see if they have stayed clean as a result of the washing process. The monitoring can be done with conductivity equipment. Control limits can be set once enough initial data is collected. Correlations between machine maintenance and the volume of boards washed could be determined.

While most cleaning processes in the global electronics manufacturing industry still rely on cleaning with DI-water only (for OA flux removal),recent studies suggest that water is beginning to reach its cleaning limitation,favoring the use of chemically assisted cleaning processes. The increased use of water-soluble lead-free solder requires more activators and higher soldering temperatures,which result in more burnt-in fluxes and produce water insoluble contamination. DI-water alone has a limited to no ability to solubilize non-ionic residues on the board’s surface.
These findings coincide with the use of smaller,more densely packed components which further limit the effectiveness of pure DI-water. Due to its high surface tension of over 70 dynes/cm,water cannot effectively penetrate underneath low standoff components. Chemistry assisted cleaning processes,however,can reduce the surface tension to 30 dynes/cm and below and therefore eliminate penetration problems.
This technical case study complements the authors’ initial in-house findings by comparing them to actual production assemblies and conditions. The lead engineering team at a participating customer site designed this comprehensive blind study to determine removability with DI-water versus various chemistry supported systems. The findings revealed significant experimental data,which shed much needed light on this emerging industry challenge.

Cleaning flux residues post soldering has been a high reliability criterion practiced by assemblers of military,aerospace,automotive,medical devices and other value offerings. Highly dense advanced packages reduce spacing between I/Os and
standoff heights. The complexity of removing flux residue increases,while elevating the risk of white residue under low
standoff (gap) components. To address this concern,many electronic assemblers use water soluble solder paste and clean
post soldering. The purpose of this factorial designed experiment is to evaluate multiple water soluble flux materials and cleaning chemistries,including DI water only,to determine the best chemical properties for removing lead-free water soluble flux residues. The optimal process parameters will be defined with data findings analyzed and presented using statistical analysis and models.

The present work describes the use of additives in formaldehyde-free copper solutions to improve the start reaction of
electroless copper deposition.
Conventional electroless copper plating solutions contain a copper salt,one or several complexing agents,a reducing agent,a pH adjusting agent as well as stabilizers and other additives.
At the present time formaldehyde is the established reducing agent in electroless copper metallization of plated throughholes.
Because of its environmental impact,there is a need to replace formaldehyde. Many alternatives have been suggested but some of them pose a greater health and safety threat than formaldehyde does and some alternatives are not economically viable.
In this investigation,the more environmentally friendly glyoxylic acid is used as an autocatalytic reducing agent. However glyoxylic acid is more expensive and causes undesirable side reactions. Consequently,it leads to a rise in the price of the copper plating process. In order to keep process costs under control,the concentration of glyoxylic acid in the copper bath should be reduced without affecting the quality of the copper deposits.
Therefore,additives are introduced which can compensate for the lower reducing agent concentration,and thus the lack of essential electrons for the copper deposition. On palladium-activated base material,the additives react with the palladium and generate additional electrons in the initial phase of the deposition. Thus,the adequate supply of electrons from two sources permits the deposition of a homogeneous and compact copper layer.