Minerva M. Cruz and Russell T. Winslow
Six Sigma
Milpitas, CA, USA
This study focuses on identifying the residues found on the surface of high temperature co-fired ceramic packages after prolonged exposure to moisture. Using a "farming method", enough residue was created to facilitate a thorough analysis. Tests using SEM-EDS, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, and X-ray Diffraction have identified these residues as primarily -Ni(OH)2 and -Ni(OH)2. Traces of tungsten oxide and a silicate compound were also detected.
The findings of this study should help process engineers resolve package-related problems when nickel-gold finishes are utilized. It may also help explain why pure gold finishes fail solderability testing after steam-conditioning -- a test they should otherwise pass with ease.
In this study, the residues found on the surface of goldplated HTCC substrates, after prolonged exposure to moisture, have been identified. These residues are a mixture consisting primarily of -Ni(OH)2 and -Ni(OH)2. Other constituents, which appear to be tungsten oxide and a silicate compound, were also found.
These -Ni(OH)2 and -Ni(OH)2 corrosion residues may help explain some issues found in integrated circuit manufacturing and packaging, such as:
- solderability failures
- die attach voids
- variation in wire bond strengths
- lid seal voids
Six Sigma has found that these corrosion residues need to be removed in order to promote good wetting, and hence, maximize board-level reliability.
