Thermal Interface Material Resistance Measurement Apparatus

It is well known that as the size of microprocessors decreases with respect to Moore\´s law, cooling issues have become more predominant and critical for the electronics industry. One source of thermal resistance requiring more characterization is thermal interface materials, TIMs. Thermal interface materials, such as greases, elastomeric pads, thermal tapes, phase change materials, gels, thermally conductive adhesives and solder, are used in a variety of electronic and microelectronic engineering applications. Currently in industry, TIM testers are modeled after ASTM D 5470, "standard test method for steady-state thermal transmission properties of thermally conductive solid electrical insulation material". ASTM D 5470 uses two metal blocks, one heated and one cooled, between which a TIM is placed. Temperature sensors are placed within the metal blocks. Since the temperature distribution is linear, the temperature of surface of the metal blocks in contact with the specimen can be calculated using the sensor-given temperatures and the distance between the sensors. A thermal model was also developed to ensure the placement of the thermocouples within uniform heat flow; this is especially critical for the thermocouple placed closest to the heater. A CPU cooling unit is used as a cooling mechanism and constant uniform pressure is maintained through the use of a pneumatic cylinder. Calibration and verification is done through the use of steel films. Phenolic and balsa wood insulate the copper rods ensuring one dimensional heat conduction