Surface Finish Selection for Fine-Pitch Assembly The surface finish protects the copper before assembly and then becomes the surface the solder wets, which means it has to satisfy two different requirements with one layer. On fine pitch the choice narrows further, because flatness and a controlled thickness matter more than…

AQL Sampling Plans for Final PCB Inspection A sampling plan is a statistical agreement about how much defect is tolerable in a lot, and it is often applied to electronics as if it were a checklist. The AQL value defines the quality level that will be accepted most of the…

Placement Vision Centering: What the Camera Sees Placement vision exists to answer one question quickly: where is the part relative to the nozzle that is holding it? A machine that answers correctly places within a few tens of microns; one that answers approximately places acceptably on coarse parts and fails…

Wave Solder Flux Residue: Cleaning Under Components Wave soldering applies flux to the whole underside of the board, and the solder wave then heats everything on that side, including the flux that ran under the components before the board arrived. The flux residue that results is trapped in the least…

Conveyor Speed: Reflow Conveyor and Rail Maintenance: Holding the Profile A reflow oven is calibrated as a system, and the profile it delivers depends on the conveyor speed being what the profile assumes. Rails wear, drive belts slip and edge supports bend, and the resulting change is a slow drift…

Inspection Gauge R&R: Proving an Inspection Method Works An inspection method is a measurement system, and like any measurement system it has variation. Gauge R&R separates the variation that comes from the parts being measured from the variation that comes from the inspectors and from repeatability, and in assembly work…

Laser Depaneling: Cutting Thin Boards Without Damage Laser depaneling separates boards without touching them, which is why it suits thin board assemblies where a router would flex the panel and a punch would shock the components. The trade is that the cut is a thermal process, and the heat affected…

Stencil Aperture Wall Quality and Laser Cut Finish The aperture wall is the surface the paste touches on its way to the pad, and its condition decides whether the deposit leaves the stencil or stays behind. Two stencils cut from the same foil with the same geometry can release very…

Wave Height and Nozzle Control in Wave Soldering Wave height sets how deeply the board touches the molten solder, and the contact depth that results decides whether holes fill and whether bridges form. It is a mechanical setting with a chemical consequence, and the nozzle that produces the wave is…

SMT Floor Humidity Control: Paste, Floor Life and ESD Humidity is the one process variable that affects printing, assembly and static control at the same time, and it is usually the last one to be instrumented. A floor that drifts above its range shows up as solder balling and short…