(A) study on the interconnection of embedded chip and metal trace substrates using solder anisotropic conductive films (ACFs)

Abstract

Due to the development of mobile communication technology, demand for the multi-functional products development is increasing. In substrate technology, embedded chip substratesare the one of the key technologies for the development of multi-functional products, therefore lots of studies are doing. For the chip interconnection, laser drilling via interconnection technology wasusually usedto make embedded chip substrates. Laser drilling via technology wassimple and reliable process, however as the pattern was formed after chip embedding, there were structural limitation. For these reasons, in this study we are going to investigate on the ACFs flip chip interconnection technologyfor the embedded chip substrates implementation in order to improve structural limitation by using laser drilling technology, To verify the ACFs materials properties, four kinds of ACFs were used. For the thermosetting resin, epoxy was used because epoxy has thermal stability and for increasing the epoxy curing rate, anhydride and anion curing agent were added.As the conductive particle, SnBi and SAC305 lead free solder was used because solder has low contact resistance by metallurgical contact. To find the reliable ACF, thermal stress was applied after chip bonding.As the analysis methods, the chain resistance difference was measured after thermal stress and the solder joint was observed to find the abnormality using SEM. Using reliable ACFs, bonding condition optimization tests were conducted by varying temperature, time, and pressure.Moreover the electrode design optimization test was performed to increase adhesion between ACFs and electrodes. Consequently, the embedded chip substrates were successfully fabricated using previous bonding and design optimization tests results. For the embedded chip substrates characterization, in-situ insulation resistance was measured by applying bias and in order to verify the stability about thermal stress, pressure cooker test, temperature cycling, and multiple reflow tests were performed.