PCB Assembly Services - Screaming Circuits: High frequency pcb


High frequency pcb

One of the advantages of rapid electronic prototyping is the ability to look at layout dependent issues early in the design cycle. This becomes even more critical with high current or high frequency designs.

It's not just the layout. Things like copper trace thickness and board material composition also impact circuit operation and reliability. Your layout can be perfectly sound, but in some application may still not work without the proper board material.

Pretty much every electrical engineer should know that since a capacitor is essentially two metal layers with a non-conductive material in between, a pcb can also be a capacitor of sorts. Any pcb with more than one layer is essentially two metal layers with a non-conductive material in between. Yes; that's a serious over-simplification, but you get the idea. In most cases, the capacitance involved is so small the it effectively doesn't have an impact in the design. As the circuit operates at higher frequencies, it does become an issue. First, a designer will need to look at isolated areas of the circuit and tweak the layout.

Up in the range of 500 MHz and above, the capacitance of the pcb becomes a large enough of an issue that standard pcb laminate materials may be completely unsuitable for a design. Enter Rogers Corporation, up in Vancouver, Washington. They make a number of specialized materials, including high-frequency pcb laminates that can be used in a manner very similar to FR4. Rogers materials allow very tight control of board capacitance as well as thermal and other important properties. The materials can be used in both leaded and lead-free board fab processes.

If you have high frequency applications, ask your board fab house about Rogers' materials for your pc board fab.

Duane Benson


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