Loren Dean Durfee

Recent advances in silicone pressure-sensitive adhesives

Silicone pressure-sensitive adhesives (PSAs) are widely used in pressure-sensitive tapes and labels when application conditions or the nature of substrate surfaces surpass the performance boundaries of organic-based PSAs. Since the year 2000, there has been continuing interest in and pursuit of new uses for silicone PSAs, especially in applications such as medical and industrial tapes. Driven by needs for regulatory compliance and changing performance requirements, silicone PSAs based on new silicone chemistry and cure mechanisms have also emerged. This paper reviews significant advances that have occurred over the past decade in the field of silicone PSAs and describes the range of commercial uses where silicone PSAs are being used and exploited. These include industrial, electronics and medical applications.

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.