THERMOSONIC BONDING OF AN OPTICAL TRANSCEIVER BASED ORE AN 8X8 VERTICAL-CAVITY SURFACE-EMITTING LASER ARRAY

This paper reports the results of our thermosonic (T/S) flip-chip bond ing process development for the assembly of a smart pixel array (SPA) using an 8 x 8 vertical cavity surface emitting laser (VCSEL) array, T he introduction of ultrasonic energy into the flip chip bonding proces s increases the speed of the assembly process while at the same time l owering the physical stresses (temperature and assembly force) applied to bond the components, Many empirical studies hare shown that T/S hi p-chip bonding is feasible, but there is a lack of detailed understand ing of the effects of the ultrasonic energy on the bonding results, We are conducting experiments and developing models that will provide a sound understanding and a rational basis for T/S hip-chip bonding, In particular, we have addressed the problems of the impact of joint bump size, control of the assembly force, and the repeatability of the ult rasonic power, This report details our findings concerning the followi ng aspects important to the development of T/S flip-chip bonding techn ology: 1) Computer modeling to guide the! selection of design paramete rs and provide a basis to study the Effects of the interaction of the critical design and process parameters on process yield, 2) Design of a new end effector for accurately applying and monitoring small assemb ly force, 3) Monitoring and controlling; the impedance of the ultrason ic mechanical and electrical system in order to insure repeatable deli very of acoustic energy to the assembly.