Thermomechanical assessment of plastic coated TAB chips

A bending beam technique was used to classify different plastic coating films by the shear stress exerted on the Si substrate. Tape-automated-bonded (TAB) test chips coated with the plastic materials were exposed to temperature cycling. By means of IR microscopy the extent of mechanical degradation of the inner lead bonds (cratering) was quantified. This degradation turned out to be clearly correlated with the deflection of the beam, which is a measure of the shear stress exerted by the plastic coating. Thus, the bending beam technique allows the assessment of the component´s quality with respect to the thermal cycling stress