THE SNAGCU SOLDER JOINT INTEGRITY OF GREEN WLCSP IN LEAD FREE SMTAuthor: Jeffrey C.B. Lee et al.
Company: Advanced Semiconductor Engrng.
Date Published: 2/25/2005 Conference: Pan Pacific Symposium
In this report, the interfacial metallurgical reactions of solder joint of the combination of 0.3mm SnAgCu solder ball and different melting point solder pastes such as Sn37Pb and Sn3.0Ag0.5Cu will be investigated in the wafer level CSP package with 0.5mm ball pitch.
After appropriate SMT process at low, medium and high reflow temperature respectively on NSMD FR4 PCB with Cu-OSP surface finish, the sample is subject to TCT (-40~125?) 500 and 1000 cycle, then are followed by solder joint cross-section observation with SEM/EDX. The diverse failure mode on the metallurgical evolution in the interface and solder bulk itself is recorded to illustrate the solder joint integrity.
The relationship among the fracture morphology and solder paste type is concluded as well. Furthermore, one new technology with polymer collar structure around the solder ball is integrated to discuss the whole SnAgCu solder joint integrity enhancement during the TCT test. A mature wafer level CSP with Sn37Pb solder ball will be used for comparison as well.
Key words: ROHS, wafer level CSP, SnAgCu, solder joint, polymer collar.
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