Solder ball bumper SB/sup 2/-a flexible manufacturing tool for 3-dimensional sensor and microsystem packages

Abstract

A novel high speed solder deposition system for microelectronic devices has been developed by Pac Tech GmbH. With this fully automatic system, the high speed solder ball bumper (SB/sup 2/), preformed solder balls are placed at pre-programmed bond positions and are reflowed by a laser pulse in a single step. The use of flux or second reflow is not necessary. The system design fits a broad range of applications. Due to the low heat input during solder deposition, and the fact that additional component heating is not required, this method is especially interesting for temperature sensitive devices. Besides bumping processes on single dice or at wafer level, solder balls for IC packages such as /spl mu/-BGAs, BGAs and chip size packages can be placed and reflowed. Other applications include solder deposition for PCBs and interconnection of 3D automotive sensor chip packages. With small modifications, the SB/sup 2/ can process solder balls with diameters from 100 /spl mu/m up to 1 mm. A singulation unit separates the balls from the bulk by means of a rotating cavity disk. Using a pneumatic pulse, the ball is transported from the cavity down to the capillary tip. The solder ball reflow is performed with a laser beam that passes through a glass fiber into the capillary directly above the placed ball. During laser pulsing, nitrogen prevents oxidation of the liquid solder. The SB/sup 2/ also provides great flexibility for microelectronic device repair. The system can be used to realise a repair station attached to the normal process flow. It allows a selective removal of defective solder bumps and renewed solder attach to the contact pads.