Reflow Conveyor Speed Calibration and Belt Maintenance The profile that was qualified on a machine describes the product only while the conveyor delivers it at the speed the profile assumed. Belt wear, rail alignment and drive calibration all change that speed, and none of them announces itself with an alarm.…

Gold Finger Chamfer and Bevel Requirements for Edge Connectors An edge connector meets its mating socket at an angle, and the chamfer on the leading edge is what allows it to enter without lifting the contacts or scraping them. The feature is small, it is produced after plating, and it…

Drill Bit Life Management: Hit Count and Regrinding A drill bit wears gradually, so the defect it causes appears as a trend rather than as a reject, and by the time the trend is visible the holes have already been produced. The control that works is a hit count established…

Counterfeit Component Control: Incoming Inspection and Traceability Counterfeit components are a supply chain problem that is solved on the receiving dock rather than in the assembly area, because once a part is on a reel and in a feeder, nothing downstream will distinguish it from a genuine one. The controls…

Incoming Inspection: Design Rules and Process Limits Laminate and prepreg carry the properties that decide impedance, thermal behaviour and press cycle, and they arrive with a certificate rather than with a guarantee. Incoming inspection exists to confirm that the delivery matches the certificate, that the material has been stored as…

Fine Pitch Stencil Aperture Design at 0.4 mm At a fine pitch the printing process stops being a way of applying paste and starts being a contest between two surfaces. Each deposit is a fraction of a cubic millimetre, and whether it ends up on the pad or stays on…

SMT Changeover and First Article Verification A changeover replaces the stencil, the feeders, the programme, the support tooling and often the paste itself, and every one of those is a variable that can move the process. Treated as a single event, the changeover hides mistakes; treated as a list of…

Annular Ring and Breakout: Design and Registration Limits The annular ring is the copper that remains around a hole after drilling and etching, and it does two jobs at once: it carries the connection from the barrel to the trace, and it absorbs the registration error of the process that…

PCB Storage and Shelf Life Before Assembly A finished board that sits in a warehouse does not stay the same. The surface finish oxidises, the laminate absorbs moisture from the air, and the mask continues to cure slowly, and all three change how the board behaves when it reaches the…

Work Instruction Content for PCB Assembly A work instruction is the document that tells a qualified operator how to perform one operation and how to know that it has been performed correctly. It is written for the person at the machine, not for the customer or the auditor, and it…