PCB Cleaning: Flux Residue, Ionic Contamination and Test Cleaning is the least visible process in electronics assembly and one of the most consequential. Residue left on a board after soldering can be electrically harmless for years and then cause a failure when the humidity rises, an effect that appears in…

Eight Circuit Design Misconceptions and What They Cost Most circuit design misconceptions are not errors of knowledge, they are errors of habit. A rule that was true on one project gets carried to the next one, where the conditions that justified it no longer exist. The eight listed below all…

Microcontroller vs Microcomputer: Architecture Differences The terms microcontroller and microcomputer are often used interchangeably, which hides a real architectural difference that has consequences for the schematic, the layout and the software. One device is a complete small computer on a single die; the other is a computer assembled from separate…

PCB Impedance Matching and Buildup Process Explained When a signal leaves a driver it should arrive at the receiver with as little loss and as little reflection as possible. That happens only when the impedance of the trace equals the impedance of the source, which is what impedance matching means…

Infrared Thermometer PCB Design and Thermopile Sensors An infrared thermometer is a small system with an unusually demanding analog front end. The detector produces a signal in the microvolt range, the ambient temperature drifts over tens of degrees, and the whole measurement has to complete in about a second. The…

High Tg Copper Clad Laminate: Properties and Selection Laminate selection is one of the few design decisions that cannot be corrected by changing a component or a trace. A high Tg copper clad laminate costs more than the standard material, and the question of whether that cost is justified is…

Audio Adapter Board PCB: Noise, Grounding and Layout An audio adapter board converts one interface into another: a digital link into an analogue jack, a balanced signal into an unbalanced one, or a microphone input into a stream of samples. The circuit is small and the components are cheap, yet…

High-Speed PCB Design Rules and the Reasons Behind Them High-speed design rules are usually presented as a list of things not to do, which makes them easy to memorise and easy to ignore. Almost every rule on the list exists for one of three reasons: controlling the area enclosed by…

Op-Amp Circuit Design: Considerations That Prevent Oscillation An operational amplifier looks like the simplest component on the schematic and behaves like one of the most temperamental. The external network is a handful of resistors and capacitors, yet the same topology can be stable on one board and oscillate on the…

400G and 800G Optical Module PCB: Loss, Vias and Heat An optical module is one of the densest mixed signal assemblies in production. A pluggable 400G or 800G module contains a digital signal processor, several analogue front ends, a driver for each optical lane, a microcontroller and a thermal path…