Dae-Gon Kim

Analysis of Failure Mechanism in Anisotropic Conductive and Non-Conductive Film Interconnections

Failure behaviors of anisotropic conductive film (ACF) and non-conductive film (NCF) interconnects were investigated by measuring the connection resistance. The four-point probe method was used to measure the connection resistance of the adhesive joints constructed with Au bump on Si chip and Cu pad on flexible printed circuit. The interconnection reliability was evaluated by multiple reflow process. The connection resistance of the ACF joints was markedly higher than that of NCF joints, mainly due to the constriction of the current flow and the intrinsic resistance of the conductive particles in ACF joints. The connection resistances of both interconnections decreased with increasing bonding force, and subsequently converged to about 10 and 1 mOmega at a bonding force of 70 and 80 N, for the ACF and NCF joints, respectively. During the reflow process, two different conduction behaviors were observed: increased connection resistance and the termination of Ohmic behavior. The former was due to the decreased contact area caused by z-directional swelling of the adhesives, whereas the latter was caused by either contact opening in the adhesive joints or interface cracking.

Mechanical strength test method for solder ball joint in BGA package

Ball shear tests were investigated in terms of effects of test parameters, i.e. shear height and shear speed, with an experimental and non-linear finite element analysis in order to evaluate the solder joint integrity of area array packages. The substrate was a common SMD type with solder bond pad openings of 460 μm in diameter. Microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. It was observed that increasing shear height, at fixed shear speed, results in decreasing shear force, while the shear force increased with increasing shear speed at fixed shear height. Excessive shear height could cause some detrimental effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball surface. Low shear height conditions are favorable for screening the type of brittle interfacial fractures or degraded layers in the interfaces.

Interfacial reactions and- intermetallic compound growth between indium and copper

The growth kinetics of intermetallic compound layers formed between pure indium solder and bare Cu substrate by solid-state isothermal aging were examined at temperatures between 343 and 393 K for 0–4×106 s. A quantitative analysis of the intermetallic compound layer thickness as a function of time and temperature was performed. Experimental results showed that the Cu11In9 intermetallic compound was observed for bare copper substrate. Additionally, the thickness of the Cu11In9 intermetallic compound was increased with the aging temperature and time. The layer growth of the intermetallic compound in the couple of the In/Cu system followed a parabolic law over the given temperature range. As a whole, because the values of time exponent (n) were approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by a diffusion mechanism over the temperature range studied. The apparent activation energy of Cu11In9 intermetallic compound in the couple of the In/Cu was 34.16 kJ mol−1.