A Study Of The Bonding Reliability For The Anisotropic Conductive Adhesive Film

The anisotropic conductive adhesive film (ACF) is one kind of green andenvironmental protective interconnected materials. It is significance for applicationin the field of Micro-Electro-Mechanical System to investigate the bonding strengthand the failure mechanism. The effects of different bonding parameters such astemperature, pressure, curing time, bonding temperature ramp and post processingcondition in relation to the electrical performance and the adhesive strengths of ACFinterconnection were investigated. The results of test show that the contactresistance changes slightly, but the adhesive strengths increase with the bondingtemperature increased. The longer curing time could improve the adhesive strengthsof ACF joints to resist the absorption moisture damage. The contact resistanceincreases with the bonding pressure increased. It is shown that the contact resistanceand adhesive strengths both become deteriorated with the Teflon film thicknessincreased. The specimen stored in high temperature condition to eliminate residualstress, had the best performance of the ACF interconnection. The environmentalexperiments of the thermal cycling and the high temperature/humidity aging wereused to evaluate the reliability of these specimens with different bonding parameters.The optimum bonding parameters of ACF joints were given according to the testresult both considerations of the electrical properties and adhesive strengths.The experiment discovered that the glass change temperature (Tg) did notchange with curing degree and curing time of ACF. ACF's ability of moistureabsorption varied with the temperature and humidity, and water ingress in the ACFhad the property both reversible and irreversible. A novel thermal cycle equipmentbased on the semiconductor cooling technique was set up. It has the advantage ofincreasing temperature and thermal exchang quickly. The optical microscope is usedto observe the evolution of interfacial bubbling and delamination of the ACFbonding. The failure occurs in the interfacial bubbling where is the residual stressconcentrated region. Interfacial delamination results from the coupling of thermaland humidity attack for long time.The interfacial stresses analysis of ACF bonding has been done under thermalloading and humidity loading. Beam theory model has been used to derive theintegral equation of stresses and strains through the beam element analysis of film.The ACF bonding interfacial relation of stresses and strains is derived by theboundary condition and equilibrium equation. The shear stresses and normal stressesof interface can be solved by the integral equations. The results of ANSYSsimulation and calculation of the model were the same.90o peeling force-displacement curves of the ACF bonding samples can becalculated by the interface constitutive model. The constitutive equation for theinterface was modified by the damage factor χ that consideration environmenteffects. The thermal damage factor and humidity damage factor can be derived fromthe experiment data. The interfacial model with damage factor can characterize theACF bonding strengths after environment test. The calculated result of theinterfacial constitutive model with damage factor accorded well to the 90o peelingtests.