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SAC Microvoids

Idea/Definition Information
Actual Project Stage: 
Completed
Project Category: 
Lead-Free
Project Leader Company: 
Sun
Problem: 

 

•Measure the effects of bath parameters and other treatments upon the intermetallic compound layer and the root cause of brittle fractures in SAC Alloys-Microvoids
 
•Support Electronic Industry efforts to improve the Reliability of SAC Alloys
 
•Obtain quantitative results that will provide corrective action guidance to industry to mitigate the occurrence of brittle failures in drop or shock; for example cell phones
 
•Develop fracture mechanics models that account for the effect of microvoids and intermetallic compounds material properties in simulated loads

 

Approach: 

 

•Quantify the effect of copper plating bath parameters and other treatment of the copper plated layer on the formation of microvoids in SAC and SnPb solder joints. The effects of feature edges and feature sizes will also be investigated.
 
•Use Hull Cell technique to quickly create many samples with several input variables.
 
•Evaluate the plated Hull Cell panels with respect to voids, shock test, resistance, and other output parameters.
 
•Submit a symposium paper
 
•NOTE: Immersion silver coating will be used to maximise the effects. Method of micro-etch will be documented.
 
•Used Hull Cell technique (next slide) to quickly create a lot of samples with many input variables.
 
•Hull cell panels were created from single-sided PCB material.
 
•The copper was not patterned in order to optimize current distribution.
 
•Features created on the panel using soldermask served as both plating mask and solder mask.
 
•We made 375 of these panels from 15 PCB panels.
 
•Board (panel) material was single layer copper clad FR-4, low Tg with immersion silver
 
•The plated Hull Cell panel was screen printed with solder and used as a PCB in SMT assembly of components.
 

 

Key Participants: 

 

Sun Microsystems, Alcatel-Lucent, Purdue, Alcatel-Lucent, NSC, Delphi, MacDermid