UTILIZATION OF DIE ATTACH ADHESIVES IN WAFER LEVEL ASSEMBLY OF CAVITY PACKAGES FOR IMAGE SENSORS
Authors: G Humpston and M Nystrom, S Kanagavel, M Previti a Company: Tessera Inc. and Cookson Electronics Inc. Date Published: 1/1/2007
Abstract: High performance image sensors require encapsulation to provide protection from the environment. Preferably, the packaging is done at the wafer level in order to exploit the low cost and high yield of this method of assembly. Each device package must provide an air space between the front face of the semiconductor die and the underside of the package lid because the sensor array is covered with micro lenses, which are provided to maximise the low light sensitivity of the camera. One scheme for providing a stand-off distance between these components is to apply a picture frame of adhesive around each device on the wafer and then attach the lid wafer. This paper describes the materials attributes required of the adhesive and demonstrates how film and screen-print die attach adhesives can be adapted and used outside of their normal process bounds to achieve joints of satisfactory quality for this application.
Key words: Wafer level package, die attach adhesive