Challenging Application Requirements
To simplify operations, manufacturers are seeking TIM platforms that offer greater versatility and options across application categories. Could, for example, a material be formulated to deliver both high thermal performance and long-term reliability, or even compressibility combined with high thermal performance and long-term reliability? The answer rests in the design flexibility – or form and function – of their molecular structures, which are explored below.
Key TIM Solutions: Form and Function
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Most PCMs contain wax-based polymers, transforming from a solid state to a softened or gel state as the temperature reaches its phase change or melt temperature. The melting process, which is reversible, occurs when temperatures exceed the melt temperature – typically in the 45°C to 70°C range.
Figure 1 shows the transition from a solid to liquid state and the impact of temperature on viscosity. Increasing temperatures result in low viscosity, which enables high wetting properties, thin bond lines and low contact resistance for improved TI.
In addition, as the temperature decreases, the PCM solidifies, maintaining the polymer matrix integrity and thus long-term reliability. As with most TIMs, PCMs include a filler material, usually a metal or ceramic powder, responsible for conducting heat. Filler loading also affects viscosity and flowability, and fillers are chosen to provide the best balance. Available in film form factor and in a paste format, PCMs are easy to apply. Recent technology advances will likely make them available in a gap pad format too, to meet specific needs for compression.
