Electrochemical Migration and Corrosion on PCB Assemblies A board that works in the lab and fails in the field after a few months of humidity is usually the victim of an electrochemical process rather than a defective component. The damage is slow, invisible at first, and driven by the combination…

Radiation Detector Circuit Design With a Geiger Tube A radiation detector built around a Geiger tube is a small system with three difficult parts: generating a stable high voltage from a battery, shaping a very small pulse without losing it in noise, and converting a count rate into a dose…

High Speed BLDC Motor Control in a Handheld Product A handheld dryer with a motor spinning at a hundred thousand revolutions per minute is a power electronics problem in a small plastic case. The inverter, the bus, the sensing and the thermal path all have to fit into a handle.…

Cable Assembly to PCB: Crimp, Strain Relief and Retention A cable assembly is where a board meets the outside world, and it is where most of the field failures that are blamed on the board actually happen. The crimp, the strain relief and the connector retention each have a defined…

Industrial Oscillator Design Notes For Gateways An industrial gateway is expected to run in a cabinet that may be warm in summer and cold in winter, to start reliably after a power interruption, and to keep its network link up for years without a clock related error. The oscillator that…

Non Inductive Micro Thick Film Resistor Selection A resistor that has to fit into a space of a few square millimetres, survive a wide temperature range and behave predictably at high frequency is a different component from the chip resistor that sits beside it on the same board. The thick…

Panelisation: PCB Panel Design and Material Utilisation A production panel exists to make handling and processing efficient, but every panel carries material that becomes waste. The way the boards are arranged on the panel decides both the material cost and the process quality, and it is usually settled late. Why…

Manufacturability Review Before the Data Is Released A design review that happens after the data is released is an inspection, not a review. The manufacturability review is the step where the drawing, the process and the volume are compared while a change still costs a revision rather than a batch.…

LVPECL Differential Oscillator Design Notes A differential oscillator drives a clock as a pair of complementary signals rather than as a single ended logic level. The receiver looks at the difference, so any noise that couples equally into both conductors cancels instead of appearing as timing error. That property is…

Low Skew Clock Buffer Fanout And Output Termination A backplane that carries several cards, each with its own processor and its own reference clock, needs a distribution device that can drive many differential pairs with almost no difference in delay between them. The buffer is chosen on three figures: how…