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|Reliability of Lead-Free BiAgX Solder Paste for Die Attach application|
|Keywords: Die attach, lead-free solder, Paste|
|The current work reports the reliability of a lead-free BiAgX solder paste, designed for die attach application. The BiAgX paste composed of the majority of the high melting BiAg powders (>260oC) and the minority of additive powders. The additive powders are dominating the interfacial reaction to improve the wetting of the majority powder-BiAg on various commonly-used surface finish materials. After reflow, the joint shows the above 260oC remelting temperature. The average bond shear strength of BiAgX joint between SiC die and AMBC-SiN substrate linearly decreases from 54MPa to 16MPa with increasing temperature from RT to 250oC. It is about 2.5times of the bond shear strength required in IEC standard. Upon thermal storage at 200oC or 230oC for 1500hrs, the bond shear strength decreases to 40MPa and 21MPa, respectively. Thermal cycling from -55oC to 125oC for 2000cycles and thermal shocking from -55oC to 150oC for 2000cycles show the similar trend on the joint strength drop. However, the average bond shear strength for Si/BiAgX/Cu joint (>20MPa) is 30% higher than the comparison Si/Pb5Sn2.5Ag/Cu joint (~15MPa). The microstructure observation shows that creep-fatigue-associated crack initiation and propagation account for the drop of the bond shear strength for both BiAgX and Pb5Sn2.5Ag joints.|
|Dr. Hongwen Zhang, Research Metallurgist
Indium Corporation of America