Product Code Database
Thermal paste (also called thermal compound, thermal grease, thermal interface material ( TIM), thermal gel, heat paste, heat sink compound, heat sink paste or CPU grease) is a thermally conductive (but usually not electrically conductive) chemical compound, which is commonly used as an interface between and heat sources such as high-power semiconductor devices. The main role of thermal paste is to eliminate air gaps or spaces (which act as thermal insulation) from the interface area in order to maximize heat transfer and dissipation. Thermal paste is an example of a thermal interface material.
As opposed to thermal adhesive, thermal paste does not add mechanical strength to the bond between heat source and heat sink. It has to be coupled with a fastener such as screws to hold the heat sink in place and to apply pressure, spreading and thinning the thermal paste.
Silver thermal compounds may have a conductivity of 3 to 8 W/(m·K) or more, and consist of micronized silver particles suspended in a silicone/ceramic medium. However, metal-based thermal paste can be electrically conductive and capacitive; if some flows onto the circuits, it can lead to malfunction and damage.
The most effective (and most expensive) pastes consist almost entirely of liquid metal, usually a variation of the alloy galinstan, and have thermal conductivities in excess of 13 W/(m·K). These are difficult to apply evenly and have the greatest risk of causing malfunction due to spillage. Furthermore, these pastes contain gallium which is highly corrosive to aluminium and thus cannot be used on aluminium heat sinks.
Factory PCs and laptopsalthough seldom tablets or smartphonestypically incorporate thermal paste between the top of the CPU case and a heat sink for cooling. Thermal paste is sometimes also used between the CPU die and its Heat spreader, though solder is sometimes used instead.
When a CPU heat spreader is coupled to the die via thermal paste, performance enthusiasts such as Overclocking are able to, in a process known as "delidding", pry the heat spreader, or CPU "lid", from the die. This allows them to replace the thermal paste, which is usually of low quality, with a thermal paste having greater thermal conductivity. Generally, liquid metal thermal pastes are used in such instances.
Another issue with some compounds is the separation of the polymer and filler matrix components occurs under high temperatures. The loss of polymeric material can result in poor Wetting, leading to increased thermal resistance.
This softening allows the paste to flow back and partially undo pump-out. The result is an improved lifespan in terms of resistance to hot-cold cycles. They are originally used in thermally conductive pads to improve microscopic fit and therefore conduction. Phase-change thermal compounds require some time under heat to settle into place after applying. As it settles into place, the heat conduction (and hence cooling) improves.
|
|
