Solder crack caused by die attach paste

In accordance with recent trends on LSI packaging, thinnerization and surface mounting, the reliability requirement has become severer and severer. Above all, package cracking failure during IR reflow soldering process has become one of the most important reliability items. The relationship between soldering compounds for encapsulation and solder cracking resistance has been discussed and studied widely. This report shows how die attach pastes influence package cracking mode. The package cracking had been considered mainly due to the delamination under flag side of die pad and vapor explosion. However, some cases of cracking from die attach layer to inner lead were observed. This is due to recent package trends, especially for memory device, with a narrower space between inner leads and die pad and thinner thickness of package. In order to observe various cracking modes, we did solder cracking experiments to be varied with package types and silver die attach grades. As a result, the cracking property and its cracking mode proved to be largely effected by die attach paste properties. Furthermore, our experiments testified that the improvement of silver die attach epoxy adhesion will not solve the die attach paste interfaces delamination. In other words, the improvement of its adhesion will cause extra stress during IR reflow soldering process to the rest of package areas. And the crack occurrence modes are different by package types. In studying antisolder cracking, we proved that it is necessary to consider the other packaging materials and package designs further.<
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