Case Study 6 - Dielectric Properties of FR4
The client was a start-up company engaged in the design of a new range of RF power amplifiers, operating at frequencies up to 2GHz. They had manufactured a number of prototypes but the projected unit cost was too high. They identified that the use of high quality PTFE based PCB substrates was a significant contributor to the unit cost and replacing them with low cost FR4 would yield a substantial cost reduction. However, they were concerned about the RF dielectric performance of FR4 and how to control it.
Wireless Solutions were engaged to provide the client with a technical white paper which explained, in detail, the dielectric characteristics of FR4 including dielectric constant, loss tangent, variability with frequency, temperature and moisture and the resultant effects on microstrip structures. The importance of the glass fibre to epoxy ratio was described and it was explained how to specify an FR4 based substrate to achieve low cost but relatively well controlled dielectric characteristics. The client used the technical white paper as the basis for replacing many of their PTFE substrate PCBs with lower cost FR4, making a significant contribution to reducing the unit cost of their products.