A Peelable solder mask is a type of solder mask that can be peeled off the surface of a printed circuit board. This type of solder mask is used to protect specific areas of a PCB during reflow soldering, wave soldering, or surface finish process. It is applied over the pads or plated through holes prior to the PCB assembly process and prevents the accumulation of excess solder on empty pads during the soldering process. It also protects gold plated contacts which can dissolve in molten solder. Peelable solder mask is easier to remove than regular solder masks.
Peelable solder masks are also used in selective surface finish processes such as soft gold PCB surface finish or Hard gold PCB surface finish. This type of solder mask ensures that the correct finish is only applied to the desired areas of the PCB. The surface finish is a coating on the bare copper area of the PCB to provide a solderable surface and to protect the exposed copper circuitry.
A peelable solder mask is also necessary for the parts that will be manually installed after the automated assembly process.
Peelable solder masks are usually applied by screen-printing and are removed after processing at the contracted PCB assembly house. The PCB fabricator can apply the mask in any design or shape on one or several sections per side at a time.