Wave Solder Flux Selection and Control in Production Wave solder flux does three jobs in a fraction of a second: it removes the oxide from the metal surfaces, it shields those surfaces from further oxidation while they are hot, and it helps the molten solder to wet them. The chemistry…

Board Handling and ESD Control on the SMT Line Most damage on an SMT line is not caused by the machine. It is caused by what happens between machines: a board pulled out of a magazine at an angle, a stack that is set down on a bench edge, a…

Solder Wick and Desoldering Practice Solder wick is a braid of fine copper strands that draws molten solder away from a joint by capillary action. It is simple, and it damages more pads than any other hand tool when it is used at the wrong temperature or for too long.…

Panel Utilization and Array Layout for PCB Cost Two designs with the same circuit can differ by thirty percent in bare board cost because of how the boards are arranged on the production panel. Panel utilization is not a fabrication detail that the supplier should optimise alone, and it is…

Laser Marking: Design Rules and Process Limits A board that can be identified can be controlled. Traceability turns a shipment into a set of individual units that can be linked to a panel, a lot, a process recipe and a test result, which is what makes containment possible when something…

Placement Offset Control and Vision Correction A placement offset is a systematic displacement of every component, or of one component, from where it should be. A systematic offset is corrected once and a random one is investigated, and the two look similar in a single image. Where the Offset Comes…

Reflow Profile Measurement and Thermocouple Placement A reflow profile is only as good as the measurement behind it, and the measurement depends on where the thermocouples are attached and how well they are attached. A profile taken on a bare board does not describe the board in production. Where the…

Designing Paste Volume for Pin in Paste Reflow Joints Pin in paste is the technique of printing solder paste into the through holes of a mixed technology board so that the through hole parts are soldered in the same reflow cycle as the surface mount parts. It removes a wave…

Nitrogen: Design Rules and Process Limits Air contains oxygen, and at reflow temperature oxygen oxidises the surfaces that the alloy has to wet. Nitrogen displaces the air, reduces the oxide that forms and widens the process window. The question is whether the improvement is worth the gas, and the answer…

Castellated: Design Rules and Process Limits A castellated hole is a plated half hole on the edge of the board, and it exists so that a module can be soldered onto a carrier by its edge. The plating has to be continuous from the barrel through the cut face to…