Multi-layer printed circuit board. 4 Layer Bare Board made of FR-4 Material with Green Solder Mask and White Silkscreen. Custom made printed circuit boards are available. In the RF industry, many printed circuit boards are made of specialty materials. One well-known RF Industry Supplier for specialty materials is Rogers. Rogers material is used in many circuit boards that go into products supporting the RF Industry. High-Frequency wireless applications that use circuit boards.