Size and PCB layout design are instrumental to whether it is possible to over mold directly over the PCB. The heat and pressures associated with the over molding process can be a detriment to certain through-hole and surface-mount components. While the temperatures of the injected polymers do not typically cause reflow of the solder, the mechanical forces present in the injection process can cause damage to either the components or their electrical integrity to the PCB.

Depending on the PCB layout and volume, there are many material choices when developing direct over molding solutions that may affect the final choice. Thermoplastic materials and some injectable epoxy resins are the most common. In general, small compact PCB designs with all surface-mount components are good initial candidates for direct over molding.