Ultra-thin and crack-free bottom leaded plastic (BLP) package design

Abstract

An ultra-thin, crack-free, and bottom leaded package (BLP) has been developed. Its manufacturability and reliability have been tested for mass production purposes. The design advantage of size comes from the removal of the outer leads from the conventional lead frame configuration. Therefore, the encapsulated chip conducts electrical signals through the bottom side of the package. With the help of the this new design concept, the thickness of the package has been reduced to as little as 0.82 mm. Since the outer leads do not occupy any mounting board, the projected area of the package on the board is only 65% of conventional thin packages, such as thin-small-outline packages (TSOP). The high reliability of the package comes from the lead frame geometry and the package bottom pad locations. The reliability has been tested by the resistance to infrared (IR) reflow test conditions. No cracks were observed by visual and ultrasonic inspection as well as cross-sectional examinations.