Thermal Chip Evaluation of IC Packaging

In order to experimentally evaluate the thermal effects of changes in integrated circuit (lC) packaging, a thermal chip was designed and tested. The thermal chip replaces a working chip in an lC package. It provides a method for measurement of temperatures on a chip where the heat input simulates that of a working chip. Temperature distribution can be obtained by making measurements at 16 locations on the chip. It further provides simulation of the distribution of heat input on a working chip by providing 16 locations for individually controlled heat input. (In fact, there are 32 transistors, grouped in 16 closely spaced pairs, each of which can be powered individually to act as either a "thermometer" or as a heat source thereby giving flexibility to match a working power array). An important feature of this design is the ability to obtain a chip temperature distribution when the chip is encapsulated or mounted facedown. Chip-to-substrata thermal resistances for filled and unfilled epoxy bonding materials were measured. Chip-to-coolant thermal resistances for face-mounted and beck-mounted multibond chips (with beam-type leads) are included. The thermal chip was found to be an effective tool for measuring the temperature distribution on a chip under different power, packaging, and cooling configurations.