Process Audit of a PCB Supplier: What the Floor Shows A process audit of a printed circuit supplier is not a document review. The documents describe an intention, and the audit exists to establish what actually happens: whether the coupons are real, whether the measurements are taken as written, and…

Drill Bit Inventory: Managing a Consumable That Fails Silently A drill bit is a consumable that degrades gradually, and its failure mode is a slow change in the hole rather than a sudden break. That is what makes drill bit inventory control a quality function rather than a purchasing one:…

Tool Presetting in the Drill Room: Length, Runout and Records Before a drill bit reaches a spindle it is set into a collet to a defined length. That operation, tool presetting, fixes how far the drill protrudes from the holder and how well it is centred, and those two quantities…

Roller Coating Solder Mask: Thickness and Coverage Control Roller coating applies a liquid photoimageable solder mask to a panel by passing it between rollers, in the same way that a printing press applies ink to paper. The process is fast and it wastes little material, and it deposits a film…

Fiber Protrusion on the Hole Wall: Cause, Effect and Detection Fiber protrusion is the condition where glass fibers stand out from the resin at the wall of a drilled hole. The fibers are not removed by drilling or by desmear, and the copper that is plated over them follows their…

Weibull Analysis for PCB Reliability Data: Reading the Slope A reliability test produces a set of failure times, and reducing them to an average throws away the information that the test was run to obtain. Weibull analysis describes the failures as a distribution with a shape and a scale, and…

Resin Bleed on PCB Surfaces: Causes and Control Resin bleed is a thin film of resin that spreads from the laminate onto the copper surface during drilling, lamination or a thermal process. It is rarely visible without magnification, and it is often present over an area much larger than the…

Hot Air Drying After Cleaning: Water Spots and Residue Cleaning a printed circuit assembly ends with drying, and the drying step decides what the cleaning leaves behind. Water that evaporates from a surface deposits whatever was dissolved in it as a ring of residue in the same place. If the…

Laser Via Drilling: Energy Density and Taper Control Laser via drilling makes the small holes that connect the layers of a high density board. The beam removes dielectric by vaporising it, and the process stops on the copper of the target layer, which acts as a natural etch stop. That…

Hole Wall Voids: Causes and Plating Coverage Control A hole wall void is a break in the plated copper that covers the barrel of a drilled hole. The break may expose the laminate underneath or it may be a thin spot where the plating is discontinuous. Either way the barrel…