Laser de-bonding process development of glass substrate for Fan-out wafer level packaging

Abstract

Due to the demand of consumer electronics products for portable and multi-function, the development of microelectronic packaging forced to reduce the size and costs, to raise high performance. The trend causes the traditional wafer level packaging (WLP) integration great challenges: (1) when the chip size continued to scaling and solder balls became large for back-end package; it does not fit it inside the chip area for Semiconductor technological progress. (2) The chips become strong and I/O numbers increased make more difficult for WLP integration. If I/O numbers and the solder ball size decreased, it can product the I/O numbers and solder ball inside the chip area. However, the limited of the design rules for PCB assembly which has not reached manufacturing specifications for the front-end IC chips. And the I/O numbers and solder ball size will increase additional assembly costs. In recent years, the industry has developed Fan-out WLP can solve the above traditional WLP integration challenges. For Infineon in 2006 proposed the Fan-out WLP Technology [1-3]. In the Fan-out WLP integration process, multichip temporary de-bonding is the most important key technology. In recent times, a lot of studies for the de-bonding process to make wafer release, including chemical dissolution, thermal release device and laser ablation technology. There exist a number of approaches to the de-bonding of thinned device wafers: they may be released by exposure to chemical solvents delivered through perforations in the handler, by mechanical peeling from an edge-initiated separation point, or by heating the adhesive to the point where the silicon device wafer may be removed by sheering or peeling [4]. The de-bonding process for Fan-out WLP needs low-temperature and zero-force de-bonding. Therefore, this paper used the UV laser ablation de-bonding technology which process can use a glass substrate and can be handled at low temperature. The UV laser de-bonding process has been successfully achieved to apply in Fan-out WLP.