Dried Paste: 5 Rules for Stencil Life on the Line Dried paste is the change that happens to solder paste after it has been on the stencil for too long, and it is one of the quietest causes of a yield loss on an SMT line. The paste still looks…
Plating Bath Temperature: 5 Checks That Hold the Window Plating bath temperature is one of the few parameters that changes almost everything at once. It moves the deposition rate, the deposit grain structure, the consumption of the additives, the solubility of the chemistry and the behaviour of the anode, so…
Lifted Pad: 5 Rules for Rework Without Damage A lifted pad is a copper land that has separated from the laminate, taking the adhesive bond with it. The copper is still there, often still soldered to a component lead, but it is no longer attached to the board. Once a…
Type 4 Paste: 6 Rules for Fine Pitch Printing Type 4 paste is a solder paste classification that describes the powder size inside it, and the number is printed on the jar because it decides what the paste can print. A type 4 powder has particles small enough to pass…
Resist Stripping After Plating: 5 Checks for Clean Boards Resist stripping is the step that removes the photoresist after it has done its job, and it is judged by what it leaves behind rather than by what it removes. A panel that leaves the tank with a clean copper surface…
Anti-Tarnish Protection: 5 Checks for Bare Copper Anti-tarnish protection is the thin organic coating applied to bare copper so that the surface is still solderable when the board is finally used. Without it, copper oxidises within days in a warm shop and within hours in a humid one, and the…
Laminate Void: 5 Rules for Press Cycle Control A laminate void is a pocket of air, moisture or trapped volatile sealed inside the cured stack, usually where two plies of prepreg meet or where the resin failed to fill the space beside a copper feature. It is invisible from the…
Support Pin: 5 Rules for Board Support in Printing A support pin is one of the small posts that hold the panel flat on the printer table while the stencil printing stroke runs across the top. Support is easy to overlook because it is invisible in the finished product, yet…
Foam Flux: 5 Rules for Uniform Wave Soldering A foam flux is the layer of flux that a wave solder machine applies to the underside of the board before it reaches the wave. Air is pumped through a porous stone in the flux reservoir, the flux becomes a foam, and…
Excess Solder: 5 Rules for Fillet Size Control Excess solder is a joint that carries more alloy than the design intended, and it shows as a fillet that bulges above the pad or that swallows the lead. It is rarely called out on a drawing, yet it causes real problems.…
