Solder Grain Structure And Cooling Rate A solder joint does not freeze at a single temperature. The alloy solidifies over a range, during which crystals grow from the cooling surface into the liquid, and the size and shape of the resulting grains depend on how quickly the joint was cooled.…

Solder Sleeve Splices and Heat Shrink Termination Methods Where a wire has to be joined permanently and then survive vibration, moisture and repeated handling, a solder sleeve is often the most reliable answer. It combines a measured ring of solder, a thermoplastic sealing insert and a heat shrink outer tube…

Rigid Flex Stackup Design Guide A rigid flex board carries the electronics on rigid sections and connects them with a flexible region that folds in three dimensions. It removes connectors and cables from a product, and it brings a set of mechanical rules that a conventional board does not have.…

Stencil Step Regions for Paste Volume Control A stencil is a metering device, and a step is what lets one foil meter two different volumes across the same board. Where a panel carries both a 0.5 mm pitch device and a power pad that needs a heavy deposit, a single…

Bare Board Test: Electrical Methods Compared A bare board is tested electrically before any component is mounted, and the test looks for two conditions: a net that should be continuous but is broken, and an isolation failure between two nets that should not touch. The test is performed on every…

PCB Substrate Color Selection and Its Engineering Effects Board color is one of the first things a customer notices and one of the last things engineers think about, yet the choice touches solder mask chemistry, inspection contrast, curing behavior and occasionally thermal performance. PCB substrate color is really two decisions…

Common PCB Design Mistakes That Delay Projects Most boards that miss their schedule are not defeated by difficult technology. They are delayed by a handful of avoidable errors that were present in the data when it was released. Cataloguing common PCB design mistakes is therefore not an academic exercise: each…

Component Tape and Reel Standards for SMT Feeders Every component that arrives on a reel is presented to the placement machine by the packaging rather than by its own body. The tape positions the part, the pocket protects it and the sprocket holes let the feeder index it, so a…

Embedded Processor Selection Guide for New Products Choosing the processor is the decision that constrains everything else in an embedded product: the board stackup, the power tree, the software effort and the production cost for years to come. Embedded processor selection is often driven by a single impressive number, such…

Constraint Driven PCB Layout in Modern Design Tools Modern layout tools no longer rely on the designer remembering every rule. Instead, rules are captured as reusable constraints that the editor enforces while routing and that a verification pass checks at the end. Constraint driven PCB layout changes the workflow from…