IR laser flip-chip bonding

A flip-chip bonding process using an IR laser was developed. A focused laser beam can be irradiated on solder balls directly through a silicon wafer using a laser beam of 1064 nm. The focused diameter of a laser beam is around 200 mum which is compatible with the solder ball pitch. A laser scanning system was used for scanning multi-solder-balls with a pre-programmed path. The laser flip-chip bonding process shows its strength on fast bonding, minimized thermal effects on the substrates, and superior bonding quality. A few second bonding time can be achieved for the IR flip-chip bonding process. Moreover, bonding for fine-pitch solder-balls can be achieved with a precision control of laser photonic energy. A DPSS Nd:Yag laser is used as a IR laser source and a power density is around 28 kW/cm². Bonded flip-chips are presented and its characteristics are discussed.