Impact of moisture/reflow induced delaminations on integrated circuit thermal performance

Ambient moisture uptake in plastic surface mount IC packages can cause delamination of critical internal surfaces within the package during reflow assembly. Delaminations can result in reduced thermal cycling life performance or provide for a pathway for the ingress of chemicals and contaminates. The effects that moisture/reflow induced delaminations can have on the thermal performance of plastic packaged ICs are not entirely understood. In this paper, the thermal performance of moisture/reflow delaminated ICs is reported. The effective sensitivity of the thermal performance as a result of the moisture/reflow induced delaminations was measured by experimental thermal resistance measurements (θ_JA) and compared to theoretical calculations based on Finite Element Analysis (FEA). Both 3-D and 2-D FEA models were developed for predictive responses which gave excellent correlation to the experimental measurements. The results showed that interfacial delaminations can cause a measurable increase in θ_JA. The magnitude of the increase is found to be proportional to the power consumption of the device and dependent on the delamination gap thickness. Expected reliability degradation as a result of die temperature rise from the interfacial delaminations is most significant for plastic packaged devices of power ratings greater than about 1 W