Stress analysis for the optimization of a new plastic package for optical sensors

摘要

Sensor packaging has become a critical element of a competitive sensor industry, being determinant of sensor performance and cost. In the recent past we worked on a new packaging concept that enabled the development of a low-cost open window plastic package. A first product was developed for an optical sensor. This new development behaved very well on all reliability tests, except for the solder dip reflow test. During this test the package fails because of the stress induced inside the package by the high temperature and air pressure inside the package cavity. This paper presents some new possible developments we analyzed in order to find a new solution that will solve the failure problem arisen in the first development of the open quad flat pack (OQFP). In order to get to the appropriate solution we had to analyze the stress levels in critical points within the package. The finite element analysis was applied on the initial version of the OQFP, as well as on the new possible solutions. It enabled us to compare stress levels within each new possible development with those within the first OQFP and to choose the one that seemed to be the most appropriate. From stress analysis results we were able to decide on the optimal choice for a reliable, low-cost product. This newly found solution is being now tested.