Developing A 7mmx7mm QFN Package Using Liquid Crystal Polymer

Abstract

Quad Flat No-Lead (QFN) packages are one of the most widely used and popular packages in the industry. The QFN packages gained popularity in the last decade because of its excellent electrical/thermal characteristics and lower costs. QFN packages are widely used in automotive, defense, handheld devices where space is a constraint and high current circuits require the package is mounted on thick printed circuit boards. This work makes an attempt to develop an economical 7mm*7mm QFN package using Liquid Crystal Polymer (LCP).The first challenge in this work investigate the different grades of LCP to match the electrical as well as mechanical properties for the package. Different materials were investigated before the LCP with the desired mechanical/ electrical properties was found. Once the organic material was selected the next challenge was to investigate a cost effective fabrication process that can be used for mass production in the industry. Process such as injection molding, hot embossing, roll to roll bonding produce shrinkage in the final package. So these conventional process were avoided. The two step process, lamination and laser ablation, is tested in this study. First multi-layer lamination technique is used to laminate 3 sheets of LCP through the bondply. Then this structure is attached to the array of lead frames. Then laser ablation technique is used to generate 7mm*7mm square holes.