The process development and reliability study of low cost Area Array QFN packaging technology

In this paper, the fabrication process of Area Array Quad Flat No-lead (AA QFN) packages was developed The developed AAQFN128L, AAQFN256L, and AAQFN441L packages were presented in the paper with the pin counts of 128, 256 and 441, and the package size was 10×10, 15×15 and 13×13mm respectively. The reliability of AAQFN was studied extensively. And at the same time, the comparison of the mechanical, thermal properties and the cost of BGA and AAQFN packages were made with the same pin counts of 256. It was found that the AAQFN packages have better warpage compared with BGA. The warpage value of AAQFN is 48.6μm which is smaller than that of BGA with a warpage value of 130.6μm However, the thermal property of AAQFN was not good The adding of solder balls on the high temperature area was proposed to achieve the similar thermal performance with BGA package. The developed AAQFN packages have excellent reliability. It can easily pass the MSL3 reliability tests.