Sandwich Multilayer Printed Circuit Boards

High-frequency materials are specially developed polymers while FR-4 is made predominantly with more cost-effective raw materials. HF material is therefore, depending on the quality, one to two dimensions more expensive than FR-4. In order to keep the entire circuit board from being many times more expensive, many developers use a more reasonable but still functional mix of materials: The high frequency or critical signals are conducted on or in HF material while
FR-4 is used for power supply systems and uncritical lines. The result is a so-called sandwich, hybrid or mixed structure where FR-4 is combined with PTFE and other HF materials from Rogers, Arlon and others. The rigidity of FR-4 is one production and application advantage over the frequently soft high-frequency material, especially when Teflon is involved.

Sandwich Multilayer Sandwich Multilayer
Low-loss micro transponder for metal production parts
made of RT duroid 5880 from Rogers and FR-4
UMTS base station for transmission rates of approx. 2 GHz made of RO4350 and FR-4 with semi-concealed drill holes for double-sided dense SMD mounting