Reza Ghaffarian, Ph.D.
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA USA
Commercial-off-the-shelf column grid array packaging technologies in high reliability versions are now being considered for use in a number of National Aeronautics and Space Administration (NASA) electronic systems.
Understanding the process and quality assurance indicators for reliability are important for low-risk insertion of these advanced electronic packages. This paper presents rework and re-column attachment of two high input/output (I/O) CCGA (CGA) packages.
Subsequent to re-column attachment and isothermal aging, the integrity of tin-lead solder-column attachment was determined and presented. In addition, the process-control parameters for assembly of re-columned CGA packages using either vapor-phase or rework stations were established for both package types/sizes.
Details of these process control parameters solder paste-print uniformity as well as quality assurance indicators based on visual inspection before and during thermal cycling tests are presented.
Qualification guidelines generated based on these and additional optical photomicrographs, X-rays, SEMs, and destructive cross-sectioning of thermally cycled, reworked, re-columned, and re-assembled test vehicles of these CGAs are presented in detail.
Key findings based on column attachment and re-assembly of CGA packages onto PCBs which were subjected to a number of thermal cycles are as follows:
- The Cu-spiral re-column version of the CGA560 package without its original ceramic interposer layer exhibited good attachment interconnection strength as re-columned and after exposure to isothermal aging at 125°C up to 500 hours.
- Based on only a few test samples subjected to thermal cycling and visual inspection, it appears that re-columned CGA60 package with no interposer is a viable rework solution from an assembly perspective only. Further work is required to substantiate these test results for an active-die version.
- All CGA1144 assemblies with re-columned packages passed 200 severe thermal cycles (-120°/85°C) with no apparent visual damage or daisy chain failures.
- Based on limited thermal cycle test results and visual inspection during thermal cycling, it appears that re-columning of CGA1144 is a viable option from a solder attachment perspective only.
