Titotial For How To Choose Substrate for PCB design

(1) Different working frequencies of signals have different requirements for plates.

(2) PCB working below 1GHz can choose FR4, low cost, multi-layer pressing plate technology is mature. If the signal input and output impedance is low (50 ohm), the transmission line characteristic impedance and the coupling between lines need to be strictly considered during wiring. The disadvantages are that the FR4 plates produced by different manufacturers and different batches have different doping, different dielectric constants (4.2-5.4) and instability.

(3) For optical fiber communication products working above 622Mb/s and small signal microwave transceivers working above 1G and below 3GHz, modified epoxy resin materials such as S1139 can be selected, because its dielectric constant is relatively stable at 10GHz, the cost is low, and the multi-layer pressing board process is the same as FR4.

Such as 622Mb/s data multiplexing branching, clock extraction, small signal amplification, optical transceiver and other recommended to use such plates, in order to facilitate the production of multilayer plates and plate costs slightly higher than FR4 (about 4 minutes /cm2), the disadvantage is that the thickness of the substrate is not as complete as FR4 varieties.

Or, the use of RO4000 series such as RO4350, but the current domestic general use is RO4350 double panel.

The disadvantage is that the number of different thickness of the two plates is not complete, because of the thickness of the plate size requirements, it is not convenient for the production of multi-layer printed board. Such as RO4350, the specifications of the plate manufacturers have 10mil/20mil/30mil/60mil and other four kinds of plate thickness, and the current domestic imported varieties are less, so it limits the laminate design.

(4) For large signal microwave circuits below 3GHz, such as power amplifiers and low noise amplifiers, double-sided panels similar to RO4350 are recommended. RO4350 has quite stable dielectric constant, low loss factor, good heat resistance, and the processing technology is equivalent to FR4. Its plate cost is slightly higher than FR4 (about 6 cents higher /cm2).

(5) Microwave circuits above 10GHz, such as power amplifiers, low noise amplifiers, up and down frequency converters, have higher requirements on boards. It is recommended to adopt double-sided boards with performance equivalent to F4.

(6) Multilayer PCB board for wireless mobile phones requires low dielectric constant stability, low loss factor, low cost and high dielectric shielding requirements. It is recommended to choose the plate with similar performance to PTFE (American/European etc.), or FR4 and high frequency board combination bonding to form a low-cost and high-performance laminate.