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|Processing, Reliability and Corrosion Resistance of Lead-Free BiAgX(TM) Solder Paste|
|Keywords: Lead Free, Die Attach, BiAgX|
|The BiAgX(TM) paste, designed for die attach application, composed of the majority of BiAg powders (melting point >260oC) and the minority of additive powders. The additive powders are dominating the interfacial reaction to improve the wetting on various commonly-used surface finish materials. Upon reflow, the voiding for both high Ag and low Ag BiAgX(TM) can be lower than 5% with the optimized reflow peak temperature and the suitable paste volume. After reflow, the joint shows the above 260oC remelting temperature. The average bond shear strength of BiAgX(TM) joint between SiC die and AMBC-SiN substrate linearly decreases from 54MPa to 16MPa with increasing temperature from RT to 250oC . Upon thermal storage at 200oC or 230oC for 1500hrs, the bond shear strength decreases from 54MPa to 40MPa and 21MPa, respectively. Upon thermal cycling from -55oC to 125oC for 2000cycles and thermal shocking from -55oC to 150oC for 2000cycles (Si die on bare Cu), BiAgX(TM) outperforms Pb5Sn2.5Sn. BiAgX(TM) also show the better corrosion resistance than SAC305 and Pb5Sn2.5Ag through salt water spray (SWS) and the combined SWS + thermal cycling tests.|
|Hongwen Zhang (Ph.D.), Research Metallurgist