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Void Minimization in Solder Joints by Substrate Surface Modifications

IP.com Disclosure Number: IPCOM000100309D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Chen, PC: AUTHOR [+5]

Abstract

Multiple small voids (MSVs) occur during controlled collapse chip connection (C4) chip joining process due presumably to entrapped organic materials or flux in metalization voids (Cr/Cu/Cr). Scanning electron microscope (SEM) analysis on C4 structures has suggested that the metalization voids on the substrate are responsible for MSVs. It was observed that the voids in C4 solder are connected to the metalization voids of the substrate. The metalization void is related to the surface texture (roughness and geometry) of the substrate. It follows that the MSV level can be changed by ceramic surface modification which can be accomplished with screen printing of the glass/alumina mixture.

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Void Minimization in Solder Joints by Substrate Surface Modifications

       Multiple small voids (MSVs) occur during controlled
collapse chip connection (C4) chip joining process due presumably to
entrapped organic materials or flux in metalization voids (Cr/Cu/Cr).
 Scanning electron microscope (SEM) analysis on C4 structures has
suggested that the metalization voids on the substrate are
responsible for MSVs.  It was observed that the voids in C4 solder
are connected to the metalization voids of the substrate.  The
metalization void is related to the surface texture (roughness and
geometry) of the substrate.  It follows that the MSV level can be
changed by ceramic surface modification which can be accomplished
with screen printing of the glass/alumina mixture.

      The alumina surface was modified by screen printing a glass/
alumina mixture as a coating on the aluminum substrate.  This
modification resulted in a change in the surface roughness of the
substrate (Fig. 1) and a change in the amount of metalization voids
after the Cr/Cu/Cr evaporation (Fig. 2).  These metalization voids
extend from the substrate coating surface all the way up to the
Cr/Cu/Cr top layer.

      Repeated experiments have shown that changing the glass content
of the mixture from 60 vol% to 67 vol% has dramatically reduced the
metalization voids and reduced the MSVs (Fig. 3).