Application Trend of Gold Tin Solder Paste to Fine Pitch Device
Masayoshi Kihinata, Sohei Nonaka, Hideaki Yoshida,
In a radio frequency and optoelectoronic device packaging, Gold-Tin (Au-20 wt% Sn eutectic) solder is
used widely due to the excellent electrical and thermal conductivity, high strength, and negligible creep
characteristic under repetitive thermal cycling. With the recent lead-free movement, Gold-Tin solder is
recognized as an alternative material for high temperature Lead-Tin solder. Generally, Gold-Tin solder is
supplied in the forms such as ribbons, pellets, and ring frames. However, these forms must be set-up accurately
on the joint area to press chips in bonding, therefore, it is difficult for these forms to satisfy the recent
requirements for the down sizing in the connection areas.
On the other hand, Au-20 wt% Sn solder paste can be applied flexibly to various supplying methods, such as
printing, dispensing system and pin transcript. These methods also make it possible to reduce the production
cost. However, in the case of using the solder paste, the void issue is one of the most undesirable problems. The
void causes the degradation of the characteristics such as the bond strength, electrical characteristic and thermal
conductivity. We have been intensifying the development of the void free paste, and have achieved void
reduction by optimizing the powder size, the flux composition and the reflow condition.