Sn-8Zn-3Bi 솔더의 Ni/Au 표면처리 PCB 기판에 대한 퍼짐성 연구 = A Study on the Spreadability of Sn-8mass%Zn-3mass%Bi Solder with Au Plating Thickness

다국어 초록 (Multilingual Abstract)

The spreadability of Sn-8wt%Zn-3wt%Bi solder on the Ni/Au pad of PCB was investigated. The thickness of Au-layer was varied from 0.03 ㎛to 0.5 ㎛. The solder paste was printed on the pad using a stencil with a gap size of 6.5mm x 6.5mm. The printed paste was reflowed at 225℃ using a commertial reflow soldering machine. As experimental results, when the Au-thickness was in the range between 0.0 3㎛and 0.2 ㎛, the spreading ratio showed 9~10% above the original solder area the Au-thickness was 0.3 ㎛, 0.4 ㎛and 0.5 ㎛the spreading ratio became +4.7%, -15.7%, and -22.5%, respectively. The intermetallic compounds of Au-Zn was produced between the Sn-8Zn-3Bi solder and Ni/Au-pad. With increasing Au-thickness from 0.03 ㎛to 0.2 ㎛, the Au-Zn IMCs moved from the bonded interface to the solder by spalling phenomenon. Accordingly, the cause of spreadability reduction was believed to be the spalling of Au-Zn IMCs, and the optimal Au-thickness was below 0.2 ㎛.