The move to lead free (Pb-free) electronics by the commercial industry has resulted in an increasing number of ball grid array components (BGAs) which are only available with Pb-free solder balls. The reliability of these devices is not well established when assembled using a standard tin-lead (SnPb) solder paste and reflow profile,known as a backward compatible process. Previous studies in processing mixed alloy solder joints have demonstrated the importance of using a reflow temperature high enough to achieve complete mixing of the SnPb solder paste with the Pb-free solder ball. Research has indicated that complete mixing can occur below the melting point of the Pb-free alloy and is dependent on a number of factors including solder ball composition,solder ball to solder paste ratio,and peak reflow times and temperatures. Increasing the lead content in the system enables full mixing of the solder joint with a reduced peak reflow temperature,however,previous research is conflicting regarding the effect that lead percentage has on solder joint reliability in this mixed alloy solder joint.
Previous work by the authors established a protocol for soldering Pb-free BGAs with SnPb solder paste based on solder ball size and target lead content in the final solder joint. The units from that testing were subjected to thermal cycling between -55°C and 125°C and compared to a SnPb baseline assembly. Results showed that mixed alloy joints performed as well as or better than standard SnPb joints under these conditions.
This study continues the previous work with evaluation of reliability in a production design. Functional assemblies were built using Pb-free BGAs in a SnPb solder process and subjected to life testing including accelerated aging and highly accelerated life testing (HALT). Results from this testing are compared to SnPb baseline units and previous product development test results.

Low melting 57Bi42Sn1Ag (BiSnAg) was explored for replacing SAC solders as a low-cost solution. In this study,BGAs with SAC105,SAC305,and BiSnAg balls were assembled with SAC105,SAC305 or 57Bi42Sn1Ag solder paste. Joint mechanical strength,drop test performance,and voiding performance were evaluated against the reflow profile. SnPb was included as a control. The findings are as follows: (1) The microstructure of solder joints showed that,among all of the combinations,only BiSnAg-105 LT and BiSnAg-305 LT exhibited well-distinguishable alloy regions. For SAC-BiSnAg systems,Sn-dendrites were noticeable at LT,while Ag3Sn needles developed at HT. The joints were homogeneous for the rest of the combinations. (2) In the shear test,combinations involving BiSnAg solder were brittle,regardless of the Bi alloy
location and reflow profile,as evidenced by stress-strain curves and morphology of the ruptured surface. The strong influence of Bi on the rupture site may have been caused by the stiffening effect of solder due to the homogenized presence of Bi in the
joint. With the stiffened solder,the brittle IMC interface became the weakest link upon shearing,although the brittle BiSn crystalline structure also contributed to the rupture. (3) In the drop test,all Bi-containing solder joints performed poorly compared with Bi-free systems,which was consistent with shear test results. Drop numbers increased with increasing elongation at break of solder bumps as measured in the shear test. (4) Voiding was affected by flux chemistry and reduced by low alloy homogenization temperatures and solid top factors,but was increased by low surface tension factor,melting sequence factor,overheating factor and wide pasty range factor. Compared to SAC or SnPb systems,the BiSnAg system is low in voiding if reflowed at LT. In this study,voiding had an insignificant effect on shear strength and drop test performance.

This paper is the second of two papers discussing the companies Lower Melt Alloy program. The first paper was presented at IPC APEX2013. The program explores the manufacturability and reliability of three Pb-free Bi-containing alloys in comparison with conventional SAC305 and SnPb assemblies. The first alloy included in the study is a Sn-based alloy with 3.4%Ag and 4.8%Bi,which showed promising results in the National Center for Manufacturing Sciences (NCMS) and German Joint (GJP) projects. The other two alloy variations have reduced Ag content,with and without Cu.
BGA and leaded components were assembled on medium complexity test vehicles using these alloys,as well as SAC305 and SnPb as base line alloys for comparison. Test vehicles were manufactured using two board materials,170°C glass transition temperature (Tg) and 155°C Tg,with three surface finishes: ENIG,ENEPIG,and OSP. The ATC testing was done at -55°C to 125°C with 30 minute dwells and 10°C/min ramps,and vibration testing at two G-Force test conditions with resistance failure monitoring was performed on the daisy chained components.
In this paper,the results of 3000 ATC cycles are discussed. The paper gives a detailed description of the technique for the vibration testing using 2 and 5 G harmonic dwells. In addition,the results of vibration testing and some preliminary data analysis are discussed. These results provide data for further statistical analysis leading to the choice of proper combinations of the solder alloys,board materials,and surface finishes for high reliability applications.

In this study various printed circuit board surface finishes were evaluated,including: organic solderability preservative (OSP),plasma finish (PF),immersion silver (IAg),electroless nickel / immersion silver (ENIS),electroless nickel / immersion gold hi-phosphorus (ENIG Hi-P),and electroless nickel / electroless palladium / immersion gold (ENEPIG). To verify the performance of PF as a post-treatment option,it was added to IAg,ENIG Hi-P,and ENEPIG to compare with non-treated. A total of nine groups of PCB were evaluated. Each group contains 30 boards,with the exception on ENIS where only 8 boards were available.
The PCBs were subjected to various pre-conditioning to simulate different conditions of the surface finish. After pre-conditioning,the PCB was printed with lead-free SAC305 solder paste and SMT components placed. The PCB was reflowed using a typical reflow profile for a lead-free process.
After reflow,each surface finish under various pre-conditioning was rated for solder spread on pad,voiding performance of BGA and QFN devices,followed with cross sectional analysis. The results were tabulated by each pre-conditioning group and a summary table was provided. A summary was provided to rate each surface finish for use under three conditions: 1) fresh condition,2) three times reflow,3) storage simulation.

The drive towards fine pitch technology also affects the soldering processes. Selective soldering is a reliable soldering process for THT (through hole) connectors and offers a wide process window for designers. THT connectors can be soldered on the top and bottom side of boards,board in board,PCBs to metal shields or housing out of plastic or aluminum are today’s state of the art. The materials that are used to make the solder connections require higher temperatures. Due to the introduction of lead-free alloys,the boards need more heat to get the barrels filled with solder. This not only affects the properties of the flux and components,but the operation temperatures of solder machines become higher. A nitrogen tunnel wave solder machine requires a temperature control in the tunnel to prevent overheating. Advanced systems are available that insert cold nitrogen. The closed tunnel wave soldering process has a wide process window and is not sensitive to small changes in environmental conditions. The same counts for wave solder machines that have nitrogen blanket systems over the wave. Improved preheaters will bring sufficient heat in the assembly and exhaust systems are adequate enough to maintain required process conditions. The nitrogen will improve the soldering and minimize dross amounts at these elevated solder temperatures.
Selective soldering is a different process. Compared to wave soldering there are additional process parameters that are affected by the higher temperatures. Solder joints have to be made close to SMD pads or components. An off-set of 0.5 mm may result in solder skips or re-melting SMD components. The higher temperature may cause warpage of the board,which also affects the position accuracy of the solder nozzle. All materials will expand at higher temperatures,but not all expansion coefficients of the materials used are equal. This not only introduces stress,but also may create off-sets.

One of the more notable trends in the data on electronics manufacturing over the past several years has been a return to regionalization. Defined as building in region for region,this trend is evident in all major geographies in which the electronics manufacturing industry operates. This presentation will consider the causes of this trend,the implications for the current industry,and examples of how it is being adopted by EMS and OEMs alike.

Since the late 1990s,the globalization of the electronics industry has put North American and European manufacturers in competition with manufacturers in China and other low-labor-cost areas. Unable to compete on price,many western manufacturers set up operations or began tapping sources of supply in the low-cost regions. High-volume products requiring low-tech electronics were the first to move from west to east. Later,as Chinese manufacturers gradually caught up to their western competitors in quality and advanced manufacturing capabilities,production continued to move east.

The movement of domestic operations overseas in search of lower costs has slowed in recent years,as most high-volume production has already left the west. The impact of some economic trends,such as rapidly rising wages in China and rising fuel costs,have contributed to the slowdown in movement of operations overseas. At the same time,manufacturers were discovering that the actual cost differential was lower than expected. In response,another trend began to emerge: on-shoring.

IPC undertook its first on-shoring study in 2012 in an effort to confirm the trend and measure its impact. Until that time,on-shoring had been the subject of speculation based on anecdotal evidence and many questioned whether the trend was real. IPC’s 2012 study found that 11 percent of the 229 reporting companies had moved some part of their operations from overseas back to North America from the beginning of 2009 through the middle of 2012. It also discovered that 19 percent of these companies had set up new operations in North America during the same period after considering overseas locations.

In 2013,a follow-up study showed that 16 percent of the 92 reporting manufacturers had moved some operations from overseas to North America from the beginning of 2012 to mid-2013,and 14 percent were planning new operations in North America through the end of 2014. The top drivers of these decisions,as reported by the survey participants,were the cost of transportation,management costs,the need to be close to customers and quality control.

The comments offered by the survey participants,particularly in the 2013 survey,indicate that a new way of thinking about operational planning is taking hold. At many companies,siting of operations is no longer a tactical decision,but is now part of a larger regional strategy that takes into account everything that affects their bottom line. They look not only at direct costs,but also at things like the speed of product innovation,time to market and insight on customer needs.

New informational resources are available that help executives conduct a thorough impact assessment,such as those offered by the Reshoring Initiative and IPC’s new study Where in the World? A Regional Strategy Roadmap for Electronics Manufacturers.

This presentation will review the evidence of on-shoring and its impact on companies that have chosen that path. IPC plans to conduct another follow-up study in early 2014 about the actual impact of on-shoring,covering such issues as inventory reduction,quality,innovation turnaround time,intellectual property protection,the “green” impact,sources of supply and customer satisfaction. These new findings will be presented for the first time. The presentation will also summarize insights from the new Where in the World study about how regional strategies are taking shape and changing the global landscape of the electronics industry.

Mr. Craig Herndon & Mr. Roger Smith will be discussing the Navy’s assignment as the DoD Executive Agent for Printed Circuit Board (PrCB) Technology and its role in ensuring that viable military electronics interconnect technologies are maintained. Risks to this industrial base were first identified in the 2005 National Academy of Sciences study entitled “Linkages: Manufacturing Trends in Electronics Interconnect Technology.” In Fiscal Year (FY) 2011,the Senate Armed Services Committee (SASC) directed the Department of Defense (DoD) Executive Agent (EA) for Printed Circuit Board (PrCB) Technology to conduct an industrial capabilities assessment of the printed circuit board industrial sector (including the supply chain) relative to its ability to meet future DoD technology needs. In 2013 Congress authorized more significant funding to implement the Executive Agent for Printed Circuit Board Technology that was authorized in the 2009 National Defense Authorization Act (Section 256,PL 110-417). While many military applications use commercially available PrCB technologies,other applications have rigorous and unique military requirements that dictate uniquely designed Printed Circuit Boards. This presentation will discuss the goals of the PrCB Executive agent and the processes that will be developed to assess the vulnerabilities and trustworthiness of the electronics interconnection technology supply chains.

The purpose of this study is to investigate the effect of plasma surface modification to improve adhesion strength between polytetrafluoroethylene (PTFE) and directly plated electroless copper. PTFE is widely applied to many industries because of its unique electrical,thermal,and mechanical characteristics. However,because of its low surface energy,it is difficult to acquire enough adhesion strength between PTFE and other substances without surface modification. Plasma is well known as one of the surface modification techniques that improve adhesion strength. In this study,high-electron density microwave plasma with nitrogen (N2) and hydrogen (H2) gas was applied. N2+H2 microwave plasma can modify surface of PTFE by nitrogen functional group. Surface modification technique with nitrogen functional group is frequently applied to surface activation for medical devices. In this experiment,so as to understand effect of nitrogen functional group for plating on PTFE,microwave plasma treatment was conducted under various conditions in terms of mixture of N2/H2 and plasma treatment time. In all conditions,before N2+H2 microwave plasma treatment,pre-plasma treatment was conducted with argon (Ar) gas in order to activate surface of PTFE. In this experiment,surface energy of PTFE after plasma treatment was calculated from contact angle of water and diiodomethane (DIM). The results of surface energy measurement showed that N2+H2 microwave plasma treatment was preferable for activate surface of PTFE. In addition,scanning electron microscope (SEM),atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) measurements were conducted after microwave plasma treatment to characterize the modified PTFE surfaces physically and chemically. SEM and AFM measurements showed that there was no remarkable physical difference between before and after plasma treatment. Result of XPS measurement showed nitrogen functional group was generated on the surface of PTFE after plasma treatment. Intensity of nitrogen functional group was function of treatment time and mixture of N2/H2. After those measurements,electroless copper plating was conducted on the surface of modified PTFE directly. After the plating,adhesion strength was observed in order to understand correlation between adhesion strength and the results of chemical and physical measurements. The results showed that PTFE surface modified by microwave plasma under specific treatment condition of N2+H2 gas could improve adhesion strength between PTFE and direct copper plating.

As feature sizes are driven to be smaller,the cost of PCB fabrication is driven higher. In particular,sequential lamination of complex circuit boards is a time consuming and expensive process. However,industry expectations
are for smaller,faster,and cheaper products. In this paper,we present an alternative to sequential lamination for fabricating complex PCBs,where conductive paste is used as interconnect between cores. All costs associated with traditional methods and interconnect using conductive paste will be analyzed.