Counterfeit: Key Checks Before Release A counterfeit part rarely announces itself. It arrives on a reel that looks correct, with a label that scans, and it usually works, at least on the bench. Screening is therefore a process of collecting small inconsistencies until the evidence outweighs the convenience of using…

Squeegee Pressure and Print Stroke: Setting the Print Window Squeegee pressure is the setting operators reach for first when a print looks wrong, and it is the one that most often makes a marginal process worse. Pressure interacts with blade type, print speed and separation, and the target is a…

Solder Mask Registration: Design Rules and Process Limits Solder mask registration is the offset between where the mask opening was drawn and where it lands on the copper, and it is the reason a drawing that looks comfortable can still produce exposed copper on one side of a pad and…

Thermocouple Attachment: Getting an Honest Reflow Profile A thermal profile is only as good as the joint between the thermocouple and the board. Attach the bead badly and the curve still looks plausible, still peaks in range, and still misleads: it reports the temperature of the adhesive rather than of…

First Article Inspection for PCB Assembly: What to Measure A first article inspection exists to answer one question before a production run begins: does the assembled board match the assembly drawing and the process that was qualified? If that question is answered honestly, the run follows; if it is answered…

Placement Nozzle Wear: Vacuum Level and Pickup Reliability A pick-and-place machine reports a missed pickup as a count, not as a cause, and the cause is usually in the nozzle tip: a worn face, a partial blockage, or a vacuum level that no longer matches the part being placed. None…

Aqueous Cleaning: Saponifier Concentration and Rinse Quality Aqueous cleaning is the most effective way to remove activated flux, and it is also the easiest way to leave a board wetter and dirtier than it started. The outcome depends on three variables that have to be controlled together: the saponifier concentration,…

Castellated Holes: Key Checks Before Release A module that solders down like a component depends on castellated holes that are drilled, plated and then cut in half, leaving a plated channel on the board edge. The whole process is a study in working at a boundary: every parameter has to…

Impedance Control Verification: TDR Coupons and Trace Width A board can be etched perfectly and still fail its impedance control requirement, because impedance is set by the dielectric thickness and the dielectric constant as much as by the trace width. Verification therefore belongs on a coupon that shares the production…

Via Tenting and Solder Mask Plugging: Parameters That Hold A via tenting decision looks trivial on a fabrication drawing and causes some of the most expensive rework in assembly, because a tent that survives HASL and storage may still rupture in the reflow oven. The mask film over a via…