THE IPC-B-52 SIR TEST VEHICLE: A DISCUSSION OF THE CURRENT TEST VEHICLE DESIGN AND POSSIBLE MODIFICATIONS FOR THE FUTURE

摘要

For many decades now, electronic hardware manufacturers have desired soldering chemistries that provide reliable interconnects. While the use of flux is essential to create proper solder joints, it is well known that residues left behind can have a negative impact on reliability caused by either electrochemical migration or by corrosion failure mechanisms. As assembly complexity has increased, it is common to have multiple flux chemistries on the same assembly. These fluxes often come from multiple manufacturers and in many instances they come into contact with one another resulting in flux mixtures. The IPC-B-24 coupon has traditionally been the electronics industry's primary test vehicle (TV) for evaluating flux chemistries and surface insulation resistance (SIR) as it provides a quick and easy way to evaluate individual fluxes as well as mixing effects. Although useful, this design is not an ideal test vehicle for assembly manufacturers to evaluate fluxes using actual production equipment and assembly processes, as it consists of only single sided surface traces, without surface mounted or wave soldered components. This shortcoming, over the years, has driven the development of various company unique SIR test vehicles. Recognizing that the IPC-B-24 coupon was not ideal for all reliability evaluations, the IPC-B-52 test vehicle was designed. It is much more capable of assessing SIR concerns with flux chemistry that result from the presence of components. As the industry continues to migrate to lead free soldering for higher complexity hardware assemblies, and new flux chemistries are introduced, it is projected that the adoption and usage of the new IPC-B-52 coupon will continue to rise. The intent of this paper is to share IBM's latest experience and recommendations when using the IPC-B-52 design helping to drive a common SIR test vehicle that can be adopted for widespread implementation, reducing the need for company specific designs, and minimizing replicate testing resources. This paper discusses the following: 1. A list of lessons learned that would be helpful to those who are considering using the IPC-B-52 design 2. Further enhancements, including component additions and card design features, that would further enhance the test vehicle's ability to address the challenges of today's complex assemblies