parker chomerics
- April 15, 2020
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Website and was written by Jarrod Cohen, marketing communications manager, Chomerics Divison.
Electrically conductive elastomers are elastomeric polymers filled with metal particles. They can be grouped by filler type and elastomer type. Then within each of these classes, there are standard materials and specialty materials.
Parker Chomerics manufacturers electrically conductive elastomers in gasket form, also known as EMI elastomer gaskets, under the CHO-SEAL brand. We won't get so much into gasket configurations and dimensions here, we'll just stick to classes of materials. So what is available? Let’s find out.
Conductive elastomers are metallic particle filled elastomeric polymers, the particles giving the shielding performance and the polymer making them “rubber." There are many materials within this generic material type, but we'll focus on the below.
Particle fillers
Setting up the grades of conductive elastomers by filler types involves six different particles:
Three types of elastomer material
- Silicone
A polymer that has a large temperature range especially on the low end down to -55F. It is a very soft material with a low compression set. - Fluorosilicone
Close to silicone, but will not swell and degrade when exposed to solvents, fuels hydraulic fluids and other organic fluids. Although slightly harder than silicone, it is still relatively soft with low compression set properties. - Ethylene propylene diene monomer (EPDM)
Does not have the temperature range nor the softness of silicone, but is resistant to highly chlorinated solvents used for compliance with NBC decontamination and is only used for applications with those needs.
All of these materials are cured or cross linked when the gasket is made. The cure either happens with heat or atmospheric moisture.
- Silicone
- January 08, 2019
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.
The Difference Between Thermal Conductivity and Thermal Impedance
Thermal Interface Materials (TIMs) are useful for thermal management in electronic components, as they enhance heat transfer from a heat-generating component to a heat dissipater, or heat sink. One important aspect when selecting a TIM for your application is knowing the material’s ability to transfer heat, which is often given by way of thermal conductivity and/or thermal impedance.
Across the industry, manufacturers often publish thermal conductivity in units of Watts / meter-Kelvin as well as thermal impedance in units of °C – inches2 / Watt on their datasheets. So, what is the difference between these two, and how should you consider them when selecting a TIM?
Thermal conductivity is a material property and describes the ability of the given material to conduct heat. Therefore, when a material’s thermal conductivity is high, the material is a better thermal conductor. This property is independent of material size, shape or orientation in a homogeneous material, and because of this, thermal conductivity is an idealized value.
To understand thermal impedance, we must first understand thermal resistance and thermal contact resistance.