A New process for Flip-chip Interconnections with Variable Stand-offs

This paper presents a new process to improve the reliability of solder connections of miniaturized flip-chips by creating a variable stand-off using jetting technology. This technology is used to generate precise solder volumes Thereby the solder is jetted directly on the printed circuit board. To increase the stand-off several solder bumps can be jetted on top of each other. The flip-chips are processed with no flow underfill to reduce process steps and to prevent short circuits between solder joints. The state of the a-is sholy presented and the function principle of the print head is explained. Measurements of the printed solder balls and solder columns are presented. The flip-chip alignment and the dispensing of the underfill are investigated. The interconnection between the chip and substrate is approved by daisy chain measurements and the enhanced stand-off is measured with laser triangulation.