Wireless Charging: Design Rules and Process Limits Wireless charging transfers power through a pair of coils that are only loosely coupled, and the circuit design is mostly about compensating for that looseness. The coil geometry, the resonant capacitor and the shielding together determine how much power reaches the receiver and…

PCB Glass Fabric Damage: Broken Strands at the Hole 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…

Microvia Reliability And Failure Modes A microvia is a small hole, usually no more than a hundred and fifty micrometres across, that connects two adjacent layers in a high density board. It is formed by a laser rather than by a drill, and its geometry is measured in tenths of…

PCB Copper Wicking Control: Resin Moving Into the Strands Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB copper wicking control from the perspective of a PCBA factory…

Solder Ball Contamination on Assembled Circuit Boards Small spheres of solder sitting on the surface of an assembled board are one of the most common cosmetic defects in SMT. They are also one of the most misdiagnosed, because the mechanism that produced them determines whether they are harmless or represent…

Solder Paste Inspection And Print Quality Control Solder paste printing is the step that determines most of the defects in a surface mount line, and the deposit is the one thing that can be measured before the components are placed. Solder paste inspection does exactly that: it scans the board…

Conformal Coating Thickness And Coverage Verification A conformal coating is a thin polymer film that is applied after assembly to protect the board from moisture, ionic contamination, and the occasional mechanical insult. It is not a paint, and its performance depends on three properties that can each be measured: the…

High Power LED Thermal Design A high power LED converts a large fraction of its input into heat, and that heat leaves through the back of the package. The optical design is what most people notice, and the thermal path is what determines whether the light output and the colour…

MOSFET Gate Charge Drive Circuit Design The gate of a power MOSFET looks like a capacitor, and the datasheet figure that matters is not that capacitance but the charge that has to be moved to take the device from off to on. Sizing the driver from the gate charge and…

Panel Rails, Tooling Holes And Breakaway Tabs A panel exists because most assembly equipment cannot handle a small, irregular board. The individual circuits are laid out on a frame that carries them through the printer, the placement machine, the reflow oven, and the test fixtures, and the frame is made…