Throughout the electronics industry, both design engineers and manufacturing personnel are looking for ways to make products lighter, smaller, less expensive and at the same time faster, more powerful, reliable, user-friendly, and functional. A partial list of today's "shrinking" products would include cellular phones, personal and sub-notebook computers, pagers and palmtop organizers. For the first time in 25 years, packaging technology is one of the greatest single factors limiting the electronics industry. Current and future innovations in packaging adhesives will be critical to miniaturizing of electronic products. This paper will focus on the application of anisotropic conductive adhesive (ACA) as an interconnect material for Chip-On-Flex technology, In phase I, a methodology of characterizing the ACA is introduced. Thermal analysis and morphological study are carried out using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and image analyzer. In phase 2, ACAs are cured under the recommended conditions and subjected to accelerated life testing at 85 degrees C/85%RH for 500 h. Their physical and thermal properties are determined during the test using DSC, TGA and thermomechanical analysis. The combined measured properties in phases 1 and 2 can be used to assess the performance of ACA, which can subsequently be correlated to the overall performance of the package using ACA as the interconnection material. In phase 3, flip chip bonding on the flex substrate is performed using reliable ACAs that were evaluated during phases 1 and 2. This is followed by an electrical test to determine their functionality after undergoing accelerated life testing. Besides this, cross-sectional views of the package are used to demonstrate the quality of the interconnection. (C) 1999 Elsevier Science S.A. All rights reserved.
