The effect of die attach layer delamination on the thermal performance of plastic packages

Plastic semiconductor packages uptake moisture under ambient conditions. This can cause delamination at various interfaces within the package during the reflow process for board mounting. Delamination in the die attach region is known to increase the thermal resistance of that interface, leading to increased die temperatures and reduced reliability. This paper investigates the effect of die attach layer delamination on the thermal performance of standard and heatslug MQFP package designs by means of measurement and thermal simulation. A series of severe temperature/moisture conditions was used to produce delamination in these packages. A thermal model for the delaminated interface was validated experimentally. It is shown that the maximum acceptable % of delamination is highly dependent on the power in the application and the degree to which the power is evenly dissipated over the surface of the die. The larger power levels made possible by the use of heatslug packages and external heat sinks lead to a lower tolerance for delamination than would be indicated in lower power applications.