An electronic heater is created by driving electric current through a resistive element. As the current is drawn through the element, some of the energy is expelled as heat. That heat can then be transferred to other surfaces with positive effects. It is a convenient way to keep components above damaging temperatures or to heat surfaces to a specified temperature and keep them there. Some of the first heaters were simple nickel-chromium wires attached to a power source and wrapped around a mass to transfer heat. This is effective, but not practical in all applications. Heaters that are designed on flexible material can be attached to flat surfaces, equipped with temperature sensing devices, and monitored constantly so that adjustments are possible as the ambient surroundings change. Two types of flexible heater material are common: silicon rubber and polyimide. This article will focus on flexible polyimide heaters.
Flexible heaters are used to keep components, typically microprocessors, at a consistent temperature in devices that are exposed to conditions that have varying temperatures. They are used to heat surfaces as well. For instance, the seat or steering wheel in your car. Biological samples are sometimes better analyzed at the typical body temperature for a human or animal. Batteries and electronics in aircraft that must operate normally at 30,000 feet above the earth are kept warm with flexible heaters.
Handheld electronics as well as ATMs that must operate accurately in cold climates will use flexible heaters to keep critical components in the specified temperature range. The uses are not trivial and one may say critical in many applications. No matter the product or what function it provides, flexible heaters are an important element in the electronics industry.
For a flexible heater to be designed accurately, we must first understand several things:
To read the full version of this article which appeared in the March 2017 issue of The PCB Magazine, click here.