Paste Tack: Why Deposits Lose Hold Before Reflow Paste tack is the adhesion that a printed deposit offers to a component lead or body before reflow. It is what holds a chip capacitor in place while the board travels to the oven, and it is the reason a placement machine…

Entry Material and Backup Board: 6 PCB Drill Stack Choices Entry material sits on top of the drill stack and backup board sits underneath it, and together they decide much of the quality of a drilled hole. Both are consumables that are chosen in seconds and then influence burr height,…

Flux Solids Content: What the Datasheet Tells You Flux solids content is the mass fraction of a liquid flux that is not solvent: the resin, the activators, the inhibitors and the additives that do the work at the joint. A flux listed at 35 percent solids carries 35 grams of…

Resin Recession: 5 Causes at the Drilled Hole Wall Resin recession is the retreat of the resin away from the drilled hole wall, which leaves a gap between the laminate and the plated copper barrel. It is found in microsection rather than on the surface, and it is often only…

Copper Wrap Plating: 5 Rules for PCB Edges Copper wrap plating is the copper that runs from the surface of a board, around the profiled edge and onto the opposite side or onto an internal plane. It is used where the edge of the board has to carry current, where…

Compressed Air Quality in SMT: 6 Checks for Clean Air Compressed air quality is usually treated as a facility matter until a nozzle clogs or a cylinder sticks. The air that reaches a placement head passes through the same lines as the assembly equipment, and whatever it carries ends up…

Nozzle Contamination: 5 Cleaning Rules for SMT Nozzle contamination is the build-up of flux, paste, adhesive and airborne dust on the tip of a placement nozzle. It arrives slowly and it displays itself as an increase in pickup errors, a drifting placement offset or a part that is dropped somewhere…

AOI False Calls: 7 Ways to Cut Them Without Missing Defects AOI false calls are the flagged images that turn out to be acceptable when a person looks at them. They slow the line, consume the attention of the review station and, in the worst case, train operators to pass…

ESD Control on a PCBA Line: 7 Points Auditors Check First ESD control is the set of measures that stops a static discharge from damaging components during handling, assembly and test. The discharges that cause most of the damage are far below the threshold a person can feel, so the…

Brown Oxide Before Lamination: Control Points That Matter Brown oxide is the conversion coating grown on inner layer copper before lamination so that the resin has something to grip. Bare copper bonds weakly to prepreg, while an oxide layer with a needle like crystal structure gives the resin a mechanical…