Pin in Paste Through Hole Reflow Pin in paste allows a through hole connector to be soldered in the same reflow pass as the surface mount parts, which removes a wave or selective soldering step from the line. The idea is simple: print enough paste into and around the hole,…

Flux Residue Qualification for No Clean Processes A no clean process leaves flux residue on the board by design. The decision to leave it is a qualification decision, and it has to be supported by evidence that the residue is harmless for that product in that environment. The evidence comes…

Prototype to Volume Transition A prototype build proves that a design can work. A volume build has to prove that it works repeatedly, at a rate and a cost that the business can sustain, with documentation that other people can follow. The transition between the two is where many products…

Alternate Source Qualification Process An alternate source exists so that a supply interruption does not stop production, and it only delivers that benefit if the alternate is genuinely equivalent. Qualifying one is therefore an engineering exercise rather than a purchasing one: the parts have to be compared on the characteristics…

Engineering Change Impact Assessment An engineering change is never only the change that was requested. A component replacement alters the bill of materials, the placement program, the kit, the test limits and possibly the stock that is already on the shelf. A revision to a drawing alters the operator instruction,…

Laser Drilling vs Mechanical Drilling Almost every hole in a circuit board is made by one of two processes. Mechanical drilling uses a rotating bit to cut through the stack, and laser drilling uses a focused beam to remove material by ablation. They are not interchangeable: each has a range…

Incoming Solder Alloy Verification and Pot Additions Solder arrives as bars, wire or paste with a certificate that states its composition. The certificate is a claim, and the alloy in the pot is what actually forms the joints. Where a nonconforming bar reaches a wave pot, the effect is spread…

Board Edge Clearance and Panel Tooling The panel edge carries the tooling that locates the panel in every machine it passes through, and the copper is kept back from that edge so that nothing touches a conductor. The width of the pullback is a fixed cost per panel and a…

Inline Cleaning Machines for PCB Assembly When an assembly needs to be clean, the cleaning machine is the process step that decides whether it is. A washer is not a single operation but a sequence of stages, each with its own chemistry, temperature and time, and a fault in any…

Test Point Placement Rules for In Circuit Test Fixtures Test points are the interface between a finished board and the machine that proves it works. Designers often scatter them at the end of layout, under whatever space is left, and the consequence is a fixture that costs more, probes less…