Keypad and Membrane Switch Interface Design A keypad interface looks simple: a user presses a button and a contact closes. In practice the interface combines a mechanical actuator, an electrical contact, and an environmental seal, and the reliability of the product often depends on getting all three right. This article…

Condensation and Dew Point Protection for Electronic Assemblies Water on a circuit board is usually blamed on rain or a spill, but the more common cause is a change in temperature. A board that cools below the dew point of the air around it collects condensation from that air, and…

Layout Simulation: Why It Belongs in PCB Design Layout simulation has been a practical option for years, yet many boards are still released without it. The reasons are usually the same three: the tools look complicated, the models are incomplete and the licence costs money. Each of those objections has…

Tape and Reel Packaging Standards for SMT Components A reel of components is a precision delivery system, not a box. The carrier tape holds each part at a known position, the cover tape keeps it there, and the sprocket holes let a feeder advance the strip by exactly one pitch…

Fabrication Drawing Checklist for PCB Production A fabrication drawing is the document that turns a set of Gerber files into a defined product. The data describes where copper goes; the drawing describes how thick, how flat, how clean and how it is to be verified. When the drawing is incomplete,…

Busbar Design for High Current PCB Assemblies At some point a copper trace becomes an impractical way to carry current. The width needed to keep the temperature rise acceptable exceeds the space available, the voltage drop becomes significant, and the layer count required to share the current makes the board…

RF Connector Plating, Sealing And Corrosion An RF connector is a mechanical interface that must also be an electrical one, and the two requirements conflict. Good contact needs pressure and hardness; good weather resistance needs a sealed joint; low loss needs a smooth plated surface. Where a product is used…

Soft Gold PCB Finish: Cost, Thickness and Applications A soft gold PCB finish is chosen when the board has to be wire bonded, stored for a long time, or assembled with very fine pitch components. It costs more than the finishes used on ordinary boards, and the reason is not…

Leak Testing For Sealed And Coated Assemblies Where a product must survive water, dust or a cleaning process, the enclosure is expected to keep the environment out. The board inside contributes to that expectation: a coating, a potting compound or a sealed housing all form part of the barrier, and…

Thermocouple Attachment for Reflow Profile Measurement A reflow profiler measures two things: the temperature of the air in the oven and the temperature of the board. The first is easy and the second depends entirely on how the sensor is attached. A thermocouple that is taped to the surface reads…