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|Heat Sink Effect of a Gold Wire Bond Next to Hot Spots on a Microchip|
|Keywords: wirebond, microsensor, heat sink|
|In microelectronics, heat removal from transistors and interconnects is vital in order to prolong the life of a device. As a result, it is useful to quantify the degree to which the wires bonded to chip act as heat sinks. A microchip containing an aluminum test bonding pad with integrated microheaters and resistance temperature detectors is used for thermal testing. Two 30 µm × 70 µm polysilicon microheaters are placed 110 µm from each other. These microheaters generate heat based on Joule heating and thereby act as hot spots which simulate active components of an integrated circuit (IC). A pair of 5.1 mm long, 25 µm diameter gold wires are bonded to the test pad in the middle between the hot spots and connected to the metallization on the ceramic package. A significant heat sink effect of these double wire bonds is found. The presence of such heat sink wires (HSWs) reduces the temperature of the hot spots operating at constant power P by ΔTH = P•k, where k = 25.4 °C/W. For example, the hot spot temperature is TH = 80 °C for P = 0.2 W without the HSW. With HSW, TH reduces to 74.2 °C. When adding HSWs, the power consumed by the hot spots can be increased while maintaining a constant temperature at the hot spots. For example, if the hot spots are kept at 80 °C, the heating powers required are 0.206 W and 0.222 W for the cases without and with HSWs, respectively. The demonstrated heat sink effect of wire bonds can be further enhanced in the future by adding several sets of HSWs to the vicinity of or directly above hot spots.|
|Michael McCracken, Masters Student
University of Waterloo - Microjoining Laboratory, Centre of Advanced Materials Joining
Toronto, Ontario M9P3E3