Copper Surface Preparation Before Lamination Multilayer adhesion is created in a few metres of process line. Before the layers are pressed together, the copper surfaces that will form the internal interfaces are cleaned, textured and oxidised so that the resin has something to grip and something to bond to chemically.…

OSP Surface Finish Process Control and Storage Guide OSP, or organic solderability preservative, is a thin organic film that protects clean copper from oxidation without adding any metal to the surface. It is the cheapest of the common finishes, it is simple to apply, and it leaves the flattest possible…

Rework Station Selection for SMT and Through Hole Repair Rework is the part of the process where the strongest equipment and the least controlled method often meet. A technician with a hot air tool can replace a fine pitch package, but only if the tool delivers heat in a way…

Moisture Barrier Bag Sealing and Desiccant Control A moisture barrier bag protects a component from the humidity in the air until it is opened. Everything about the pack, the seal, the desiccant and the indicators, exists to make the storage life predictable rather than hoped for. What the Bag Has…

Wave Soldering: Wave Solder Defect Troubleshooting The wave process solders through hole joints by passing the board across a standing wave of molten alloy. It is fast and robust, and it has a narrow window: the flux must be applied correctly, the board must arrive at the right temperature, and…

Through Hole Solder Fill Requirements for Barrel Joints A through hole joint is judged by how much of the barrel it fills and how well the alloy wets the walls. Those two properties determine whether the joint can carry current reliably, whether it survives thermal cycling and whether it will…

Four Wire Resistance Measurement of Solder Joints A solder joint that is failing often behaves normally until the moment it opens, and the early indication is a small increase in resistance. Measuring that increase requires a technique that does not drown it in lead resistance. Why Two Wire Is Not…

Fuse Selection: Fuse and Protection Device Selection on PCB A fuse is the simplest protection device on a board and the one most often chosen by habit. It sits in series with the supply, carries the normal current indefinitely and opens when the current exceeds its rating for long enough.…

Underfill Dispensing and Capillary Flow Control Underfill is a filled polymer that flows into the gap under a package and surrounds the solder joints, so that the thermal expansion mismatch between the package and the board is shared rather than concentrated at the joints. It is applied after reflow and…

SPI Data and Print Process Feedback An inspection system that measures the paste deposit is only useful if the measurement changes something upstream. The volume figures it produces describe the printer, the stencil and the paste, and the value of the data comes from how quickly that description reaches the…