Water Spot Defect: 5 Causes After the Final Rinse A water spot defect is one of the few cosmetic faults that customers reject without argument, because a marked surface suggests a process that is not under control. The spot itself is usually harmless chemistry left behind when a drop of…

Pump Seal Leak: 5 Checks That Stop Bath Loss A pump seal leak is one of the quietest faults on a plating line, because a few drops an hour disappear into a drain tray or evaporate from a warm pump body. The bath level falls, make-up water is added, and…

Microetch Control: 5 Rules for a Bondable Copper Surface Microetch control prepares copper for the next layer by removing oxide and a thin film of metal at the same time. The etch is deliberately small, and that is exactly why it is easy to neglect, because a bath that has…

Barrel Plating Control: 5 Rules for Small Parts and Pins Barrel plating control matters wherever small parts are plated in bulk, from press-fit pins to connector shells and shield cans. The parts tumble against each other, so the current path, the contact and the load size all change constantly during…

No-Clean Residue: Setting a Defensible Allowance A no-clean process deliberately leaves flux residue on the assembly and relies on that residue being benign for the life of the product. The term describes the process rather than the material, and it does not mean the residue is absent or that its…

Underfill Flow Control: Filling the Gap Under a Package Underfill is a filled polymer dispensed along the edge of a package and drawn into the gap beneath it by capillary action, where it cures and couples the package, the solder joints and the board into one structure. Its purpose is…

Vapor Phase Reflow: Heat Transfer and Profile Control Vapor phase reflow heats a board by condensing a boiling liquid onto it, so the surface of the assembly is held at the boiling point of that liquid while the whole mass catches up to the same temperature. The mechanism differs from…

Etching Factor Control: Getting Straight Copper Sidewalls The etching factor is a number describing how close an etched conductor comes to a rectangular cross section, and it is one of the few figures that ties imaging, plating and etching together in a single measurement. A high factor means a sidewall…

Component Floor Life: Managing Moisture Sensitivity A plastic package absorbs moisture from the air, and the absorbed water turns to steam when the package is heated to reflow temperature. The pressure that develops can crack the package, delaminate the die attach or lift the bond wires, and much of that…

Squeegee Durometer and Wear: Holding the Print Window The squeegee is the part of the printing process that turns a reservoir of solder paste into a defined deposit, and its condition changes the result before any other variable is touched. A blade that has worn or hardened no longer rolls…