Connector Selection for Assembly and Reliability A connector is the part of the assembly that the user touches, and it is also the part that carries the mechanical load of every cable that is plugged into it. Electrical ratings are easy to compare between two candidates, while the mechanical and…

PCB Milling Design Guide PCB milling removes copper with a rotating cutter instead of dissolving it with chemistry. The process is fast for a prototype, it needs no etchant and no phototool, and it can produce a board in an hour. It also has rules of its own, and a…

Plating Bath Chemistry Control and Analysis Methods A plating bath is a chemical reactor that is expected to deliver the same result every day for months. Copper thickness, hole wall coverage and surface appearance all come from the balance of a small number of components, and that balance shifts continuously…

Die Attach Materials and Void Control in Package Assembly Inside a package, the die is held in place and cooled by a layer that is often only tens of micrometres thick. That layer has to conduct heat, survive thermal cycling, keep out moisture and stay mechanically stable for the life…

Solder Paste Rheology And Viscosity Control Solder paste is not a liquid that flows in the ordinary sense. It is a suspension of metal particles in a flux vehicle, and its viscosity changes with the rate at which it is sheared and with the time that has passed since it…

Via Tenting: Preparation, Placement and Process Control Via tenting is one of the cheapest decisions on a printed circuit board, and it is also one of the most misunderstood. A tented via is simply a via whose pad and hole are both covered by solder mask, so the mask bridges…

Desmear And Hole Wall Quality In PCB Drilling Drilling a hole in a laminated board generates heat, and the heat softens the resin at the wall of the hole. The softened resin is smeared along the wall by the rotating drill, and a thin film of it is deposited over…

AOI and X-ray Inspection Coverage Compared Automatic optical inspection and X-ray inspection are often described as alternatives, and they are not. Each one detects a different class of defect, and a line that relies on only one of them carries a blind spot that is predictable in advance. Optical inspection…

Copper Foil Peel Strength and Laminate Bond Testing Copper that lifts from a laminate ruins a board, and the failure usually appears late: at reflow, during assembly, or in the field after thermal cycling. Peel strength is the measurement that predicts whether that will happen. It quantifies how strongly the…

Solder Paste Viscosity Measurement and Control Viscosity is the property of solder paste that everyone quotes and almost nobody measures under the conditions the printer actually uses. A single figure on a certificate tells you that the batch is within a range, not that it will roll, release and slump…