Improved IC reliability with TAB packaging

Micronas test chip MAS 7812 has been used to assess the reliability of a number of different packages, associated materials, and chip passivations as well as some assembly housings. The test device was earlier found to give sufficient coverage of the most important failure mechanisms in plastic-encapsulated and wire-bonded ICs. The reliability of Finlux TAB package was evaluated in environmental tests. The encapsulated devices were subjected after aging to 100 temperature cycles between -55°C and +125°C. Pressure-cooker tests followed at 125°C and 85% RH. The shapes of the pad openings in final passivation were studied. Four different pad opening structures were selected for this work; the bump size and type were also varied. The bump layers were Ti-W(N,O)/Au. Much attention was given to the design of the final passivation and pad areas to improve the reliability. The test results are presented and discussed