Polymer Thick Films

Polymer thick films (PTF's) are a class of solvent born printed circuit board coatings that from - as the name implies - thick films. PTF's can be conductive or non-conductive.

In the case of polymer thick films, the binder and the filler are both part of the finished product. PTF's can be as much as 50% filler by weight. The metal filled cunductive PTF's are often used as 'jumpers' on printed circuit boards instead of solder, especially when the substrate or electronic devices are heat sensitive. Conductive PTF's are also used for 'through hole' applications - connecting one side of a PCB to the other - instead of solder or electroplating. The non-conducting PTF's are used as dielectric coatings on printed circuit boards. The filler in non-conducting PTF's is usually glass.

PTF's are usually made of polyesters and acrylics. However, carbon loaded phenolics find use in potentiometers (variable resistors) due to the good durability and abrasion resistance of the phenolic resin to the 'brush' in the potentiometer. Polyester/silver PTF's are used as electrical traces on flexible polyester film keypads.