Wave Height Stability in Wave Soldering The wave in a wave soldering machine is a standing shape that the pump produces, and its height has to be stable for the joint to be repeatable. The height is affected by the pump, by the alloy level in the pot and by…

Surface Finish Shelf Life and Solderability Monitoring A surface finish has a shelf life, and the shelf life is a statement about solderability rather than about appearance. A board that looks unchanged after six months may have an oxide or an intermetallic layer that makes the joint unreliable, and the…

Thermal Relief Design Rules for Plane Connections A pad connected directly to a copper plane is thermally welded to it. That is excellent for current capacity and for heat spreading, and it is a problem for soldering, because the plane draws energy away from the joint faster than any soldering…

Product Changeover Verification Changeover is the period when a line stops being tooled for one product and starts building another, and it is statistically the most dangerous time in the shift. Parts from the previous product, settings from the previous recipe and assumptions from the previous build all persist for…

Supplier Scorecard and Review A supplier scorecard is a small set of measures that describes how a supplier is performing, and a review meeting is where those measures are discussed with the supplier. Done well, the pair changes behaviour, because the supplier can see the trend, understands how it is…

Incoming Inspection: Incoming Material Inspection Planning Incoming inspection exists to catch problems before they enter the production line, and it works best when it is designed around risk rather than around a habit of checking everything. No factory can inspect every characteristic of every part it buys, and attempting to…

Depanelising and Routing Quality Depanelising is the last mechanical operation before a board becomes a product, and it is one of the few remaining processes where a good board can be destroyed by technique. Routers, v-score breakers, tab cutters and laser systems all separate panels, and each of them introduces…

Paste Flux Residue Removal Materials and Methods Guide Flux residue removal is a decision that is made by the product rather than by preference. A consumer board inside a sealed enclosure may tolerate a no clean residue for its whole life, while a board that will be conformally coated, operated…

Stencil Aperture Design for Mixed Technology Boards A mixed technology board carries a fine pitch surface mount population and a set of through hole parts, and the two need different paste volumes from the same stencil. Meeting both on one sheet of metal is the problem the stencil design has…

Board Level Shielding Design With Cans and Fences A board level shield is a metal enclosure soldered over a circuit to keep electromagnetic energy in or out. It is a mechanical part, a thermal part and an electrical part at the same time, and the design has to satisfy all…