Interfacial adhesion of anisotropic conductive adhesives on polyimide substrate

There has been steadily increasing interest in using electrically conductive adhesives as interconnecting materials in electronics manufacturing. Simple processing, low processing temperature and fine pitch capability are the major advantages of conducting adhesive technology. A new and innovative connection technology geared towards achieving increased functionality at a lower total system cost is anisotropic conductive adhesive (ACA) interconnection. ACAs, when used for flip chip assembly, provide electrical as well as mechanical interconnections for fine pitch applications. This work deals with adhesion issues between ACA on polyimide materials. The paper presents a reliability assessment of adhesive joints using ACA on polyimide substrate that was conducted by testing samples at various aging temperature, high humidity and high pressure enviromments. The effects of high temperature and high humidity on the bond strength of ACA joints were measured using 90 deg peel test as well as by microstructural examination. It was found that aging generally caused a decrease in peel strength, especially the results of scanning electronic microscopy showed that the pressure cooker test could most effectively reveal the adhesion behavior.