Why the zero-ohm resistor?

November 28, 2016 // By Bill Schweber
Bill Schweber considers use cases for the zero-ohm resistor.

Passive components – resistors, capacitors, inductors, and connectors – usually don’t get a lot of consideration until late in the design, but they are vital elements of a functioning circuit, especially in the analog and sensor world. Despite all the attention we give to ICs or discrete semiconductors, passive-component vendors still see interesting opportunities for new products and introduce new ones at a fast pace.

Being a curious fellow, I am always interested in the latest updates to what are incorrectly considered "mundane" components. A recent one I saw was a zero-ohm resistor from TT Electronics.

Such "resistors" are not a new development: I first ran into them many years ago working a summer job repairing small electronic gadgets. This was in the days before larger-scale integration, and one circuit board was populated with many single-function ICs, passives, and connectors (all through-hole), plus about half- dozen wire jumpers, some of which were fairly long.

When I asked the manager (an electronic engineer) about this, he explained to me that using these jumpers allowed the manufacturer to "get away" with using low-cost, single-sided PC boards, and they were cheap phenolic material with punched holes rather than a more-expensive FR4 substrate and its more-costly drilled holes. These 0-Ω components functioned as crossovers which allowed for a much-cheaper product, even though they had to be installed by hand (as were the other components, I am fairly sure).

Years later, I again encountered these 0-Ω resistors on a major project, one which was almost entirely surface mount and did use multilayer FR-4 boards. I was somewhat mystified. I looked at the schematic and they were shown called out, and on the BOM, but I saw no electronic reason for them.