Prepreg and Laminate Storage Conditions for PCB Shops Prepreg is a partially cured resin system on a glass carrier, and it is designed to react when heat and pressure are applied. Long before that, it is reacting slowly with whatever moisture is in the air around it. Storage conditions determine…

PCB CAD Layer Colour Setup for Faster, Safer Layout Layout tools display a dozen layer types at once, and the eye can only separate them if the colours do the work. A deliberate layer colour scheme is a design aid rather than a preference, because it decides which mistakes are…

Solder Paste Powder Size And Flux Activity Solder paste is a suspension rather than a single material. It consists of small spheres of solder alloy held in a flux vehicle, and the two halves of that mixture have separate jobs. The powder melts and forms the joint, while the flux…

PCB Design Efficiency Through Early Schematic Verification Most of the time in a board project is spent looking for mistakes rather than drawing copper. Improving design efficiency therefore means removing error sources before layout starts, rather than routing faster once it has. Where the Time Actually Goes A typical flow…

Time of Flight Sensor Interface Design A time of flight sensor measures the delay between a light pulse leaving an emitter and its return to a detector, and converts that delay into a distance. The delay for a metre is about six and a half nanoseconds, so the whole design…

Schematic and Layout Cross Selection Without Dragging Nets Cross selection is the link that lets a block be chosen in the schematic and then found, moved or inspected in the layout. It saves a great deal of time, and it produces a familiar annoyance when the wrong objects come along…

Copper Balance and Panel Distortion Control in Lamination A multilayer board is a stack of materials with different expansion and shrinkage behaviour, pressed together under heat and pressure. If the copper distribution is uneven, the layers move by different amounts and the panel comes out of the press wanting to…

Solder Wetting And Dewetting Defects Wetting is the process by which molten solder spreads across a metal surface and forms a continuous metallic bond at the interface. It is not simply solder sitting on a pad. A properly wetted joint shows a small contact angle, a smooth concave fillet that…

Capacitive Sensing Electrode Design A capacitive control panel measures the change in capacitance produced by a finger near an electrode. The change is a fraction of a picofarad against a background of several picofarads, so the electrode geometry, the routing and the surrounding ground all matter as much as the…

Color Sensor Interface Circuit Design A color sensor measures the intensity of light in a few wavelength bands and reports the result as numbers. Turning those numbers into a colour that matches what a person sees requires an understanding of the light source, the filtering and the way the readings…