Board level reliability of Chip scale packages

As portable devices have become smaller, thinner, lighter and more powerful in the recent years, the request of chip scale packages has become extremely high. However since the packages have the characteristics of small and thin outline, fine pitch and high density, the standoff of the solder interconnects becomes lower, thus the compliance of the solder joints degrades. As a result, the second level reliability of chip scale packages becomes a major concern of adopting the packages into products. Assurance of board level reliability of a package is essential for applying it into products. This paper presents board level reliability data of several chip scale packages under thermal cyclic test. The packages are TFBGA, Film BGA, μBGA and BCC. A small PBGA (15x15mm) will be tested as a benchmark. Both Film BGA and TFBGA (thin and fine pitch) packages are developed by ASE and have a die-up, wire-bonded and over-molded configuration. Between them, TFBGA uses a BT substrate, while Film BGA uses a polyimide substrate. The μBGA and BCC (Bump Chip Carrier) were originally developed by Tessera and Fujitsu, respectively, and are currently under improvement by ASE. In this work, the board level reliability of the packages will be reported and compared Failure analyses of solder interconnects of the packages are performed and discussed Improvements of the thermal fatigue life of the solder joints are also suggested As ofthe date this paper is prepared (July 6 th , 99), all parts remain on test.

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