Electric Toothbrush Circuit Design: Motor and Charger An electric toothbrush contains a motor, a battery, a radio and a charger inside a sealed handle about twenty millimetres across. The circuit is small, and every choice is dominated by the space and the sealing. What Fits Inside the Handle The board…

Thermal Via Fabrication and Conductive Fill Materials A thermal via is a hole through the board that is used to move heat rather than to carry a signal. It is one of the few features where the fabrication method decides the thermal performance directly, because a hole that is plated…

PCB Design Workflow: Planning Before Layout Most of the effort in a board design is spent before the first trace is drawn, in deciding what the board has to do and how the space will be divided. A clear plan makes the layout a matter of execution rather than of…

MEMS Microphone Interface Circuit Design A MEMS microphone is a silicon device with a movable diaphragm and a fixed backplate, packaged with an application specific circuit and sealed with a lid that has a small hole. It is smaller and more consistent than an electret capsule, but it is also…

Flex Cracking in Multilayer Ceramic Capacitor Assemblies Multilayer ceramic capacitors are among the most reliable components on a board and among the most easily damaged. They survive decades of electrical stress, yet a few tenths of a millimetre of board deflection during depaneling can start a fracture that opens later…

Travel Converter: Travel Voltage Converter Design With USB PD A travel converter accepts any mains supply in the world and produces a regulated output for a laptop, a phone or a small appliance. Its difficulty is not the power level but the input range and the space it has to…

Floating Lamp Circuit Design: Solar, Battery and Light A lamp that floats on a lake or a harbour basin has to generate its own power, store it, use it efficiently and survive years of immersion. The circuit design follows from those four requirements rather than from the lighting specification. What…

Reflow Profile: Reflow Oven Maintenance and Profile Verification A reflow oven drifts. Zones lose calibration, the conveyor speed changes slightly, and the thermal mass of a loaded oven is not the same as an empty one. The profile that was developed on the first article is only valid while the…

Squeegee Selection and Print Quality The squeegee is the part of the printer that touches the paste, and it is the part that is replaced most casually. Its material, its hardness and its edge condition decide how much paste is pushed into the aperture and how much is left behind.…

High Magnetic Permeability Sheets For EMI A specification that says thirty decibels of shielding sounds like a complete answer, and it rarely is. A material that achieves that figure in one band can do almost nothing in another, and the sheet that is chosen from a headline number is often…