Controlling High Copper Roughness for Enhancing Immersion Metal Surface Finish PerformanceAuthors: Lenora Toscano, Aaron Karoly, Ernest Long, Ph.D.
Date Published: 9/28/2014 Conference: SMTA International
The surface preparation for soldermask application involves a chemical process that modifies the copper topography, creating a high roughness and high surface area structure which anchors the soldermask to the copper for superior adhesion. Unfortunately, very high copper roughness can lead to performance challenges related to the surface finish including difficulty in achieving surface cleanliness and degraded solderability. This is especially true for those finishes that are designed to produce thin deposits such as immersion metal plating.
This paper addresses the issue of high copper roughness in conjunction with thin surface finish plating such as immersion silver and immersion tin performance. It will propose a microetch chemistry to reduce the real surface area roughness associated with traditional heavy soldermask adhesion promoters. It will show how this newly developed etch chemistry then enhances the performance characteristics of the final finish which had been degraded by high copper roughness.
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