Vapor Phase Reflow and Its Heat Transfer Behaviour Vapor phase reflow heats a board by condensing a boiling liquid onto it. The heat transfer is far more efficient than convection, the atmosphere is free of oxygen and no fan blows across the assembly. Those properties solve problems that convection ovens…

No-Clean Residue Acceptance and Its Limits A no-clean process leaves the residue on the board deliberately. Whether that is acceptable depends on the residue, on the environment the product will see and on the voltage present, and the three have to be considered together. What the Classification Means A no-clean…

Power Cycling Solder Fatigue in Power Electronics A power device can be cycled thousands of times an hour while the heatsink stays cool. The board does not change temperature much, the ambient does not change at all, and yet the solder joints under the die crack and eventually fail. Power…

ESD Auditing and Verification in Assembly An ESD programme is a set of measurements rather than a set of signs. Everything in it can be tested, and the testing is what shows whether the protection is actually in place. What Is Measured Wrist straps, heel grounders, bench mats, flooring, ionisers,…

Etchant Regeneration and Copper Recovery in PCB Shops An etch line consumes chemistry continuously and produces a copper bearing solution that has to be dealt with. Etchant regeneration and copper recovery turn that waste stream into a controlled part of the process, and they are what make an etch line…

Printed Electronics on Flexible Substrates Printed electronics deposits a conductive ink onto a substrate and sinters it, rather than etching copper away. The process is additive, it works on flexible films and on paper, and its resolution and conductivity are set by the ink and the sintering rather than by…

Combined AOI and X-ray Inspection Strategy Optical inspection and X-ray see different things, and a line that uses both is not duplicating effort. The optical system sees the surface, the X-ray sees the interior, and the defects that matter are distributed between the two. What Each Method Can Prove An…

Assembly Line Start-Up and Shutdown Routines The first boards of a shift are built on a machine that has been idle, and an idle machine is not the same as a running one. The start-up routine exists to close the difference before product is made. What Changes Overnight The oven…

Lead Coplanarity and Placement for Fine Pitch Components A fine pitch package relies on every lead touching its pad at the moment the alloy melts. If one lead sits higher than the others, it may still form a joint by reaching down into the paste, or it may float on…

Thawing: Solder Paste Conditioning on the Line Paste is a suspension that behaves differently at different temperatures and after different amounts of working. Conditioning is the practice of bringing it to a known state before it is printed. Thawing Frozen or refrigerated paste has to reach room temperature before the…