Thermal Via Array Design for Power Devices A surface mount power device dissipates heat into a pad that is only a few square millimetres. Without a path through the board, that heat has nowhere to go except laterally through thin copper and down through still air. A thermal via array…

Pad Cratering and Laminate Damage in Assembly Pad cratering is a crack in the laminate resin under a pad, usually caused by the mechanical load applied when a component is pulled from a board. The pad may remain attached, the copper may be intact and the joint may look undamaged,…

Desmear and Hole Wall Preparation for Reliable Plating When a hole is drilled through glass reinforced laminate, the bit does not cut cleanly through the resin. It tears it, and the heat of the drill softens the material so that a thin film of resin is smeared across the copper…

Material Flow Labelling in SMT Labelling looks like an administrative task until the wrong part is placed, and then it becomes the most important process on the line. The label on a reel is the only link between a component and its identity, and it is the last line of…

PCB Conveyor Environment: Where It Happens Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This article explains PCB conveyor…

PCB Conveyor Timing: How Long It Takes Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This article explains PCB…

Rigid Flex: Preparation, Placement and Process Control A rigid flex board is rigid where components are mounted and flexible where the assembly has to fold. The region between the two is the transition zone, and it is where most rigid flex failures originate. The rules that govern it are not…

Moisture Sensitive Device Floor Life Tracking in Assembly Moisture sensitivity is one of the few assembly risks that is entirely invisible until it becomes a crack. A package that has absorbed water from the air looks identical to a dry one, yet a single reflow pass can turn that moisture…

Solder Mask Opening Tolerance and Registration Every solder mask opening is placed relative to copper that was patterned in a different process, and the two never align perfectly. The misalignment is small, usually tens of micrometres, but on a fine pitch board those tens of micrometres decide whether a pad…

Solder Mask Bleed and Its Effect on Assembly Mask bleed is the flow of solder mask beyond the intended opening, onto the pad or into the area where a joint has to form. It is a small dimensional error that has a large effect, because the solderable area is reduced…