PET is also called Polyesters, or Polyethylene Terephthalate. It has good flexibility that can be bent to fit constricted spaces, so it is ideal material for manufacturing flexible PCBs. Besides, PET also has high chemical and moisture resistance.
PET is generally 25-125 microns thick, which means it owns small size and light weight.
Note: PET has poor heat resistance, and the temperature mentioned in the table refers to a short-term exposure. In practice, it can typically withstand around 100 degrees Celsius, so soldering is usually not recommended. However, at PCBWay, when a customer selects PET as the substrate and places an assembly order, we will recommend using PET material that can withstand up to 180 degrees. Additionally, we will use low-temperature solder paste during the reflow process to ensure normal assembly service when PET is used as the substrate.
Adhesive Polymide (PI) and Adhesiveless Polymide (PI) are also common substrate used for flexible circuit board.
Check this link to place a PET board order: https://www.pcbway.com/flexible.aspx.
