Electronics Assembly Knowledge, Vision & Wisdom
Rework of High I/O Column Grid Arrays
Rework of High I/O Column Grid Arrays
Off-the-shelf column grid arrays are now being considered for use in a number of NASA systems. This paper presents rework and re-column attachment data.
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Authored By:
Reza Ghaffarian, Ph.D.
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA USA

Summary
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.

Conclusions
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.



Initially Published in the IPC Proceedings

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