Leak Testing For Sealed And Coated Assemblies Where a product must survive water, dust or a cleaning process, the enclosure is expected to keep the environment out. The board inside contributes to that expectation: a coating, a potting compound or a sealed housing all form part of the barrier, and…

Soft Gold PCB Finish: Cost, Thickness and Applications A soft gold PCB finish is chosen when the board has to be wire bonded, stored for a long time, or assembled with very fine pitch components. It costs more than the finishes used on ordinary boards, and the reason is not…

Via Plugging and Filling for Via-in-Pad PCB Designs Routing density in modern designs pushes vias into the pads they serve, and that creates a surface problem: a hole under a solder land traps flux, wicks alloy away from the joint, and leaves a void right where the thermal path should…

Flying Probe Versus Bed of Nails Testing on PCB Assemblies Electrical test is the last chance to catch a defect before a board reaches assembly, and the two dominant methods take opposite approaches. Bed of nails presses a dedicated fixture onto the board and tests everything at once; flying probe…

Amplifier PCB Design: Gain, Noise and Thermal Control An amplifier pcb is built around a simple task, which is to make a small signal larger without changing it in any other way. Everything difficult about the design follows from the second half of that sentence. Gain is easy to obtain;…

Lost Steps: Preparation, Placement and Process Control A machine tool cutting an irregular arc, a depth of cut that varies from pass to pass, and edges that look rough rather than machined: the symptoms point at the motion control system, and the first response is usually to replace the driver…

Bring-Up Procedure: Design Rules and Process Limits Bring-up is the process of turning a newly assembled board into a known-good unit, and the difference between a smooth bring-up and a difficult one is almost entirely decided by the layout. The provisions that make it smooth are cheap and they are…

Conductive Foam Gasket: Preparation, Placement and Process Control A conductive foam gasket is specified from a datasheet that quotes a shielding effectiveness of eighty decibels or more, and after assembly the product measures ten decibels worse. The natural reaction is to suspect the material and to look for a better…

Implantable Pcb: Design Rules and Process Limits An implantable PCB is a different class of product from the boards used in consumer electronics. It works inside the human body, often for a decade or more, and it cannot be serviced after it is implanted. That combination of requirements drives every…

Vapour Phase and Vacuum Reflow Soldering Explained Convection reflow through a multi-zone oven is the default for most assemblies, but it has limits where voiding must be controlled or where the thermal mass across a board is uneven. Vapour phase and vacuum reflow address those problems with different physics rather…