Engineered thermal interface material

The power dissipation and device junction temperature control in high end processors, stacked and hybrid packages, test and burn-in systems, LED devices, etc. present challenges in cooling. Many types of consumer devices and sensors are proliferating. All these applications require an ongoing improvement in thermal management. A key aspect of electronic package cooling is the thermal interface material used between the heat generating component and the heat spreader or heat sink. High performance thermal interface materials enable Tj reduction, device performance improvement and/or lower power operation. Organic laminate packages are especially vulnerable to package failures driven by CTE mis-match driven stresses and strains. Choice of TIM is therefore critical in addressing not only the thermal challenges, but also the mechanical weaknesses of a laminate package. Often a polymeric TIM with adequate compliance to address the mechanical issues and yet having a high thermal performance is desired. The properties of the TIM, such as the modulus, elongation, adhesion to both surfaces and thermal impedance, have to be carefully selected for optimum performance in a package. In this paper, we report the development of an industry leading, high performance thermal interface material. The project involved engineering the matrix polymer properties to systematically vary the composite modulus and die shear strength and meet the desired TIM property objectives. Methodical material property characterizations were carried out for feedback and formulation improvement. A few formulations were developed with TIM1 impedance in the range of 0.04-0.07 cm²C/W. The thermal performance was measured on thermal test vehicles. Material and process parameters were investigated to minimize voiding. Material characterization and thermal performance results are presented in this paper.