The ongoing trend for product miniaturisation – coupled with more modern, higher powered devices – has ensured that efficient thermal management is an essential part of both modern and future electronics design.
Newton’s law of cooling states that the rate of loss of heat is proportional to the temperature difference between the body and its surroundings. Therefore, as the temperature of the components increases, the rate of heat loss per second equates to the heat produced per second within the component; for some components the heat produced could lead to a significantly reduced working life or even complete failure.
Heat dissipating surfaces, such as heat sinks, are connected to components to allow the transfer of heat away from the PCB. The device and heat-sink are usually solid substrates which are mechanically bolted together. Ideally, the surfaces of these substrates should be perfectly smooth, but this is not usually possible. As a result, air gaps will be present at the interface of the device and the heat-sink, significantly reducing the efficiency of heat transfer.
Electrolube provide a range of thermal management interface solutions to greatly improve performance and extend the working life of devices:
Thermally Conductive Pastes – sometimes referred to as greases – do not cure; therefore, they offer the best solution when rework is important. A thin layer of paste should be applied between the device and the heat-sink to fill the air-gaps and improve the contact. The paste can be applied using a variety of methods e.g. stencil printing, screen printing, automatic dispensing equipment, or even using an aerosol spray product such as HTCA.
Electrolube offers both silicone and non-silicone thermal pastes. The silicone products tend to exhibit lower oil bleed and evaporation weight loss compared with their non-silicone counterparts, as well as offering a higher upper temperature limit in excess of 200°C. However, there are applications where silicones may be unsuitable; when devices are sensitive to silicone contamination, for example.
The silicone thermal pastes offered by Electrolube are called HTS and HTSP: HTS is the standard silicone thermal paste; HTSP is a higher conductivity version, and is useful where a high degree thermal transfer is critical.
The non-silicone thermal pastes, such as HTC and HTCP avoid concerns regarding silicone migration onto electrical contacts resulting in high contact resistance, arcing or mechanical wear. Similarly soldering problems caused by silicones will not be encountered.
Electrolube have also introduced a further two products to the non-silicone range; HTCX, lower viscosity for ease of use and HTCPX for gap filling applications. These ‘Xtra’ versions of HTC and HTCP provide increased thermal conductivity, lower oil-bleed, and lower evaporation weight loss, making them comparable or better than some silicone-based materials.
Thermally Conductive Adhesives, which cure to a solid form, may be required, exhibiting either high or low bond strength. High bond strength materials include those based on epoxy chemistry, such as Electrolube TBS; this adhesive contains small glass beads of controlled diameter, allowing for a set thickness to be achieved in order to provide optimal performance.
Electrolube’s neutral cure, silicone RTV products TCOR and TCER are another example of thermally conductive curing compounds. TCOR is an oxime cure RTV, and TCER is an ethanol cure version. TCER has the advantage that it is very low in viscosity and higher in thermal conductivity compared to TCOR; however, TCOR exhibits much higher bond-strength properties.
Thermally Conductive Encapsulation Resins are used where heat dissipation and protection from the environment are required. Electrolube produce epoxy, polyurethane and silicone encapsulation products, covering a vast array of application requirements:
ER2183 is a 2-part epoxy resin, offering excellent environmental protection whilst combining a high level of thermal conductivity (1.1 W/mK) with a manageable viscosity (5000 cPs).
UR5097 is a flexible polyurethane potting compound that offers very good thermal conductivity (0.65 W/mK), with the added benefit of UL94 V-0 certification for flame retardance.
SC2003 is a silicone potting compound with a high level of thermal conductivity (0.8 W/mK), suitable for use in high temperature applications (up to 200°C)
With applications requiring thermal management products on the increase, Electrolube continue to develop solutions for an array of industries, including the LED market. LEDs are replacing more traditional lighting methods in applications such as LCD TV backlights, electronic signs and displays and automotive lighting. The heat generated by the LEDs needs to be removed, just like a CPU, to ensure optimal performance.
Thermal management products are also offering solutions for greater efficiency in green energy development; photovoltaic inverters – which are known to be particularly sensitive to temperature; connections between the heat-pipe and water storage tank for solar-heating applications; hydrogen fuel cells; wind power generators, are just a few examples. Working alongside customers to develop optimum products, Electrolube offer thermal management solutions anywhere where heat dissipation is required.