Under-Stencil Cleaning and Solder Paste Print Quality Print quality is decided in the few milliseconds when the stencil separates from the board, and the condition of the stencil underside decides a large part of it. Paste that sticks to the bottom of the stencil instead of transferring to the pad…

PCB Design Review Order: Checking the Expensive Items First Every design review finds something, and the value of the exercise depends on the order in which the items are checked. Reviewing the silkscreen before the stack-up wastes the meeting, because a change to the stack invalidates half of what was…

Pin-In-Paste: Design Rules and Process Limits Through-hole connectors are mechanically robust and electrically reliable, and they are also the reason many assemblies need a second, slower soldering process. Pin-in-paste, sometimes called intrusive reflow, removes that step by printing enough solder paste into and around the holes so that the joints…

Salt Spray Testing for PCB Corrosion Resistance Coastal installations, vehicle underbody modules, and outdoor equipment all expose electronics to chloride, and chloride attacks metal faster than almost anything else. A salt spray test reproduces that exposure in a chamber and compresses months of service into days. The test is easy…

Laser Direct Imaging for Fine Line PCB Fabrication Imaging is where a circuit pattern is transferred from data into photoresist, and for decades that meant a film and a lamp. Laser direct imaging replaces the film with a scanned beam, removing a whole class of distortion problems and making fine-line…

Peak Pre-Scan Passed but the Quasi-Peak Detector Failed A pre-scan with a peak detector shows a point above the limit line, and the conclusion that the product has failed follows immediately. It is often the wrong conclusion. The peak detector is a fast and deliberately conservative screening tool, and the…

Laser Drilling Versus Mechanical Drilling on PCBs Laser drilling and mechanical drilling solve the same problem in completely different ways, and choosing between them is not a matter of one being newer. A mechanical bit removes material by cutting, while a laser removes it by ablation, and the difference shows…

Designing PCBs for Harsh Environments: Conformal Coating and Protection A product that has to survive outdoors, on a factory floor or inside a vehicle is subjected to conditions that a laboratory prototype never sees, and those conditions attack the board through several routes at once. Designing for them is a…

Aluminum PCB Cost for LED Lighting: Metal Core Board Pricing An aluminum board exists to move heat, and every cost decision on it follows from that purpose. The metal core is the heatsink, the dielectric layer is the thermal interface and the copper is the circuit, and the three have…

When Noise Crosses a Common Mode Choke Through Its Windings A common mode choke is placed on a power input to block common mode noise, and at low frequency it does exactly that: the specified inductance is large and the impedance it presents to common mode current matches the datasheet…