Today’s technology requires a new level of electronics that are smaller, and more sensitive than ever to thermal cycling, moisture, dust, vibrations, and other environmental factors. Selection of the wrong type of potting material can actually damage the electronics they are intended to protect. EFI Polymers excels in not only formulating urethane and epoxy materials that will work in your electronic devices, but also in identifying the keys necessary to develop a successful potting process.
As temperatures fluctuate, materials expand and contract. This is measured by a material’s Coefficient of Thermal Expansion, or CTE. In almost all cases, the CTE of a potting material will be higher than the CTE of the electronic device it is intended to protect. If your device will be seeing a wide range of temperatures, especially in situations where the temperature changes rapidly, the potting material will expand and contract much more rapidly than the electronic device, and can damage the device it was intended to protect, by shearing components off the circuit board, or by severing solder joints.
There are a few ways of solving this issue. One method is to use a material that has an extremely low CTE. However, materials with a low CTE are often highly filled and present other problems, such as very high viscosity, shelf-life issues, loss of RF transparency, and can be abrasive on meter mix dispense machines.
Another way to solve the issue is to pot the electronic device with a material that will be soft enough, or have enough flexural modulus to absorb the shock and stress of thermal cycling. This can be accomplished by using a material that has an extremely low glass transition temperature, or Tg. When a material is below its Tg, it is in a colder, hard, and rigid state. When above the Tg, it is in a warmer, soft and rubbery state. EFI Polymers has many polybutadiene urethane materials with a Tg below -40⁰C, ensuring your material is protected.