PCB Array Design and Depanelling for Efficient SMT Assembly A PCB array is a group of identical boards laid out on a single panel so that the assembly line can handle them as one unit, and the depanelling step is what separates them again afterwards. The array is a design…

Wave Solder Thermal Profiling and Preheat Control A wave solder process has a profile in the same sense that a reflow process has one, and it is measured less often. The board passes through flux, preheat, the wave and the cooling, and each of the four decides what the joint…

Soldering Iron Tip Selection For PCB Rework The soldering iron tip is the interface between the tool and the joint, and its shape and size decide how quickly heat reaches the solder. A tip that is too small for the joint forces the operator to hold the iron in place,…

Immersion Tin and Immersion Silver Finish Selection Immersion tin and immersion silver are the two flat, lead free finishes that sit between the organic coating at the low cost end and the nickel based finishes at the high reliability end. Both are thin, both are deposited by a chemical displacement…

Cleaning Machine: Design Rules and Process Limits Cleaning removes the residue that the soldering process leaves behind, and whether it is needed depends on the residue and on what the assembly will face. The decision is a product decision, and the machine is chosen after it. What the Residue Is…

Board Support and Pallet Design for Double Sided Assembly A board on a conveyor is supported at its edges only, so it sags under its own weight and under the weight of the components. The sag changes the print gap and, on a thin board, it can move the board…

AOI Programming and False Call Control An automated optical inspection station compares what it sees with what it expects, and its value depends entirely on how well the expectation was built. A program with loose thresholds misses defects and one with tight thresholds buries the line in false calls. Building…

ENEPIG Finish: Electroless Palladium Immersion Gold Electroless nickel electroless palladium immersion gold adds a palladium layer between the nickel and the gold, and that single layer changes the behaviour of the finish in several useful ways. It blocks the corrosion path that causes black pad, it allows a thinner gold…

Hand Soldering Temperature Control Hand soldering is used for the joints that the machine cannot make: a wire, a connector that will not survive reflow, a repair or a prototype. The process is manual but it is not uncontrolled, and the iron temperature is the parameter that governs both the…

Production Yield Ramp Planning A new product does not start at its mature yield, and the difference between the first week and the tenth is the ramp. Planning the yield ramp means knowing what the expected curve looks like, what will be learned at each stage and what the customer…