Experience in fabrication of multichip-modules for the ATLAS pixel detector
Abstract
About 1100 ATLAS bare modules will be assembled at Fraunhofer IZM. The bumping and assembly technology of these multichip-modules is described in this paper. Pixel contacts and lead-tin interconnection bumps are deposited by electroplating. A high yield manufacturing technology requires electrical test and optical inspection on wafer level as well as on chip level. In this paper, the result of optical inspection of more than 7600 readout chips is presented. Handling mistakes are the main reason for rejection of chips before flip chip assembly. A reliable process technology, the assembly of electrical Known Good Die (KGD), optical inspection after bumping and the development of a single chip repair technology result in 98% of good modules after flip chip assembly. The reliability of the bump interconnections was even checked by thermal cycling and accelerated thermal aging.
