Power QFN Switch IC Packaging Process And Its Reliability Study

Freescale semiconductor developed Power QFN (Power Quad Flat No Lead) Switch IC which is mixing signal technology combine generally circuit, CMOS circuit and high power circuit based on QFN(Quad Flat No Lead) IC design, it can work in automotive environment. The present paper involved in a part of the whole development work of this new product, mainly focused on the selection of packaging materials, the optimization of the assembly process and the reliability test.Generally QFN's epoxy adhesive and molding compound epoxy will have induce the big stress impact in and could not meet Power QFN package requirement when after thermal time cycle reliability tests, the mainly problems as below:Firstly, the IC will have delamination caused by stress impact after temperature cycling; Secondly, Power QFN IC needed to transfer large of heat quickly in a short time. So need to evaluate the new attachment and molding compound and optimize the parameters, to reduce the stress and meet high temperature application requirement.According to design of experiment result, selected Indium 92.5PbSn5Ag2.5 solder paste and Sumitomo G700 molding compound, and optimized the solder paste oven process; optimized the wire bond parameter on the same time. Solve the Power QFN IC assembly issue. Secondly, test reliability after time cycle. The result show, the new assembly material and new process window solve the IC delamination issue and reduce the affect of flux residue. After the mechemical test, the new reflow oven profile and wire bond parameter could make Power QFN meet reliability request.