Thick film resistors are SMD (surface mount device) resistors which are made up of a conductor material, typically made of metal, encased in a polymeric coating that has been “fired” onto the surface of a substrate, such as an FR4 printed circuit board. This firing helps to make the resistor a permanent part of the board and also provides electrical insulation. Thick film resistors are more stable and reliable than their wirewound counterparts, making them an excellent choice for use in high-frequency and high-heat applications. The thicker the polymeric coating, the more durable the resistor will be. They also have a wide temperature range and provide excellent noise suppression and shielding. In addition, thick film resistors have a wide tolerance range and are available in a variety of case sizes and footprints.