Make-Up Water: Design Rules and Process Limits Make-up water is the water used to build a new plating bath or to bring an existing one back to volume, and its purity is part of the formulation whether or not the process sheet says so. A bath made with clean water…

Plating Ampere-Hour Tracking: Charge and Bath Life An ampere-hour is one amp flowing for one hour, and on a plating line the total charge passed through a tank is the best available measure of how much work the bath has done. It is independent of the product mix, it can…

Acid Pickling Before Plating: Strength, Time and Rinse Acid pickling is the short acid dip that precedes plating, and its job is to remove the oxide, the scale and the smut that stand between the copper surface and a sound deposit. It is a cleaning step, but it is also…

Silane Treatment Before Lamination: Adhesion Control Silane treatment is the adhesion promotion step applied to inner layer copper when a conventional oxide is not wanted, and it replaces a thick brittle oxide with a thin coupling layer. The surface still has to bond to the prepreg, and it has to…

Plating Bath Level: Evaporation, Top-Up and Water Balance Bath level is one of the simplest numbers on a plating line and one of the most informative, because it moves whenever the tank gains or loses water. Evaporation, drag-out and the top-up water added to replace them all appear as a…

Plating Drag-Out: Carryover, Recovery and Rinse Load Plating drag-out is the film of process solution that leaves a tank on the panel, the rack or the barrel and is carried into the next stage. It is the largest uncontrolled loss on most plating lines, and it is also the main…

Interconnect Stress Test: Method and Acceptance Limits The interconnect stress test, usually shortened to IST, is a reliability method that heats a plated through hole with direct current and measures its resistance cycle by cycle. The coupon is its own heater and its own sensor, which is what makes the…

Daisy Chain Continuity Coupons for Assembly Reliability A daisy chain coupon is a test vehicle in which the joints of interest are wired in series so that the whole set can be monitored as a single electrical net. Instead of measuring thousands of joints individually, the test watches one resistance…

Microvia Plating Reliability: Filling and Cracking A microvia is a small hole, typically 100 micrometres or less in diameter, formed by laser and plated to connect adjacent layers. Its reliability depends on how completely it is filled and how well the plating adheres to the wall and to the target…

3D AOI Versus 2D AOI: What Each Method Measures A 3D AOI system projects structured light or a laser line onto the board and reconstructs a height map of every joint, while a 2D AOI system records an image and judges contrast, colour and shape. The distinction sounds technical but…