Process and characterization of ultra-thin film packages

Abstract

Flexible electronic system package technology was developed to meet the needs of flexible application. Because of the flexible characteristic, the package can be attached to a flat, curve surface and even a dynamic surface. It is important to provide protection of ultra-thin semiconductor chip and integrate these chips with flexible substrate. The aim of this paper is to develop an ultra-thin film package (UTFP) which can be bended easily. This technology which has highly potential for miniaturization of the electronic system can be realized by means of embedding ultra-thin components into flexible materials. Successful embedding of ultra-thin chips with 18um thickness and testing results are shown. To use a 3um Cu layer with 18um carrier film as a base, solder balls were formed on a laser-hatched Cu layer which has better wettability than other area without laser hatching. By flip-chip method, ultra-thin chips can be directly assembled. It is necessary to do dry plasma treatment to enhance the chips' strength for ultra-thin chip manufacturing. Subsequently, chips were embedded into flexible organic material. With proper embedded material chose, it can make this UTFP bendable and provide functions of support and protection. After carrier film was removed and metallization process was done, an ultra-thin and highly flexible package with embedded chip was carried out. The electrical path were connected together to form daisy chain structure for electrical measurement. The total thickness of this package is less then 100um and it can be easily bended to 10mm bending curvature radius without any cracks. Not only the UTFP process was developed, but also some testing methods were executed to examine the reliability of package, such as TCT (Thermal cycling test) and THST (thermal & humidity storage test). Good flexible property of single UTFP has been verified in our previous study. Furthermore, the ultra-thin chip package is assembled on a flexible substrate with ACP (Anisotropic Conductive Paste) and some bending tests were performed. This package with flexible substrate connected has passed the static bending test for 200 hours and dynamic bending test for 1000 cycles under 10mm bending curvature radius. The process details on each core technique will be disclosed, and some test results will be presented in the paper.