Soldering Process Research of Large Size FC with Tin Based Bump and Ceramic Substrate

The soldering technology of flip chip has become one of the mainstream technologies. Both the mass reflow flip chip attach process and the thermosonic flip chip (TSFC) bonding process was used widely to achieve flip chip soldering. Traditional SnPb alloy has been widely used. For environment and health concerns, SnAg alloy systems were regarded as the substitute for the SnPb solder alloys. So it is necessary to find an suitable flip chip soldering technology for large size FC with SnAg bump to achieve mass production. In this work, we found the reflow soldering were more suitable to a large size FC with tin-based bump and a ceramic substrate. An Sn-Ni IMC layer was formed with a thickness of 3 um in the interface. The metallurgical reaction between bump and pad provided a strong strength for the interface. More than 95% of the solder joints after reflow were fractured inside the solder joint. Therefore, a well bond formed by reflow soldering.