Ionic Contamination and Cleaning Verification Flux residue is not inert. The activators that make a flux work are ionic, and if they remain on the board in the presence of moisture they will carry current between conductors, corrode the metal and eventually produce a failure that appears long after the…

Analog Front End Calibration Guide Every analog front end has errors, and calibration is how a design that is built from ordinary components achieves an accuracy that no single component could deliver. The work is to know which errors are worth calibrating and which are better removed by the circuit.…

Thermal Interface Material Selection Guide Heat leaves a device through a chain of materials, and every joint in that chain is a pair of surfaces pressed together. Two nominally flat surfaces touch only at the tops of their roughness peaks, so most of the apparent contact area is filled with…

Sensor Signal Chain Calibration From the sensing element to the digital value there are several stages, and each of them adds an error. Calibrating the signal chain means measuring the error of the whole path and correcting it, rather than assuming that the sum of the component tolerances is acceptable.…

Reflow and Wave Solder Carrier Design A carrier holds a board or a panel through a process. It is often added when a board is too thin to run, and it is rarely designed with the same care as the board it carries. Why a Carrier Is Used A thin…

IP Camera Board Design Around a Video System on Chip A network camera is a small computer with a lens attached, and most of it now fits in one device. Designing an ip camera board means providing the sensor interface, the memory, the network link and the power for a…

Shielding Cans, Grounding and Board Level EMC A shielding can is a metal box soldered over a circuit that would otherwise radiate or receive. It works by providing a conductive enclosure around the source, and its performance depends on how well that enclosure is completed: a can that is soldered…

ESD Packaging And Handling For PCB Assembly An electrostatic discharge is a short, high current event that begins when two objects at different potentials touch. The energies involved are small, which is why a discharge is often invisible, but the voltages are not: a person walking across a synthetic carpet…

Aluminium Substrate PCB Design for LED Strip Boards Lighting boards are the clearest case where the board is part of the thermal design. An aluminium substrate carries the light emitting devices, spreads their heat and often forms part of the fixture itself. Why LED Strips Use a Metal Board A…

Flying Probe or In-Circuit Test: Choosing for the Build Every board that is tested electrically needs a way to reach the nets. The two established answers are a bed of nails fixture that contacts everything at once, and a flying probe machine that moves a small number of heads from…