*The marks followed by an asterisk (*) are trademarks of Momentive Performance Materials Inc.
Why Thermal Interface Materials
As devices are getting smaller, more powerful & more efficient, operating temperatures are increasing. The higher energy density directly translates into more heat.
Therefore the entire electronics market is looking for better ways to cool and control temperatures of their electronic devices. This trend can be seen across many market segments; ranging from Automotive to Consumer & Lighting, to Industrial Automation and Aviation & Aerospace.
Key Drivers:
- Miniaturisation & System Integration
- Higher energy density – More electronics in the same or less space
- New Chip Technologies (GaN & SiC), will influence TIM1 & TIM2 temperature
- Higher Performance & more efficient & higher reliability
- Smaller and lighter weight – form factor
IR Thermographic Image of a High Brightness LED module, mounted to water cooling system
- Left with 0.5W/mK TIM and
- Right with 4W/mK TIM
Thermal Interface Material Factors
Purpose of Thermal Interface Material (TIM)
Heat generated by high power semiconductors has to flow through a number of different material layers and interfaces before it reaches the heat sink or coolant. Each of these materials has a property defined by:
Thermal conductivity, λ: A measure of a material’s ability to conduct heat as measured in Watts per meter-Kelvin [W/mK]
Due to surface roughness and manufacturing processes the microscopic level of the substrate and heat sink will reveal many voids in each of the contacting materials. These voids are basically air gaps which will have very poor thermal conductivity (λAir ≈ 0.03W/mK).
The purpose of a thermal interface material is to displace these air gaps with a material with higher thermal conductivity while maintaining metal-to-metal contact where possible
Paste thickness vs. thermal resistance
While thermal conductivity describes the characteristic of the material, the overall performance of the interface is defined as a thermal resistance (Rth) between junction and heat sink.
The thermal resistance is determined by more than the thermal conductivity of the paste alone. The following affect the final Rth value:
- Surface finish of heat sink (wetting capability)
- Applied thickness of thermal interface material (Bond Line Thickness)
- Mounting pressure (contact resistance)
- Thermal cycles after mounting
Thermal Measurements & Methods
Bulk Thermal Conductivity
Hot Wire Method:
Hot wire is a transient technique that involves inserting an electrically heated wire into TIM material. The heat flows out radially from the wire into the sample and the temperature of the wire is measured. The plot of the wire temperature versus the logarithm of time is used to calculate thermal conductivity.
Thermal Resistance
Laser Flash Method:
Laser flash involves applying a short pulse of heat to the front of a specimen using a laser flash, and measuring the temperature change of the back with an IR detector. The resulting temperature rise of the other face of the test specimen is monitored as a function of time and used, with the sample thickness, to determine thermal diffusivity.
Overview Addition Cure Adhesives
Typical Applications:
- 48V Powerpacks
- BSG & iBSG *
- OBC
- BMS
- DC/DC & AC/DC converter *
- Inverter *
Powermodule to heatsink Attach: * DBC to heatsink or module to heatsink
Overview Liquid Dispense Gapfillers
Gapfillers are soft, thermally conductive silicone materials that are designed to dissipate heat from electronic devices. Our Gapfillers can be used as liquid dispensed alternative to pre-fabricated Thermal Pads.
SilCool TIA241GF – Bolt Adhesion Test Results: Internal test procedure: Al bolt to FR4 vertical adhesion test
Thermally Conductive Range from Silicone Solutions
Maintaining the functionality and appearance of a surface requires a coating that can deliver protection from high temperatures, harsh weather and abrasive chemicals. Momentive’s extensive portfolio of silicone-based coatings can offer this line of defence for an array of weatherstrip, release, hard coat and electrode applications. Momentive coatings can provide excellent solvent, thermal, abrasion and chemical resistance, as well as improved adhesion to substrates for applications from sensitive electronic components and tapes and labels to automotive trim, glazing and headlights and trim. Momentive electrode coatings can help in the protection of sensitive electronic circuits and electronic components used in electronic display panels from harmful moisture and corrosion elements which can help add to the reliability and longevity of electronic systems.
To see the complete range of products available from Silicone Solutions click here
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