PCB Quote and Cost Drivers Explained A board price is the sum of a small number of large factors and a large number of small ones, and only some of them are visible in the quotation. Understanding which factors drive the price allows a design to be changed before the…

Package Warpage and Solder Ball Coplanarity Risk Control A package that is perfectly flat at room temperature can be significantly warped at reflow temperature, and that is the moment that matters. Warpage changes the gap between the ball and the pad, which changes how the joint forms, and the result…

Pin in Paste and Through Hole Reflow Soldering Pin in paste prints solder into the through hole pads and relies on the reflow oven to fill the barrels, which removes a wave soldering step. The saving is real, and the process is less forgiving than wave soldering because there is…

Drilling Stack Up and Entry Material Selection Rules Every drilled hole is produced through a sandwich of materials that includes the panel and two consumables: an entry material on top and a backup material underneath. Both are cheap, both are usually treated as an afterthought, and both have a direct…

Reading an X-Ray Image of a BGA Solder Joint An X-ray image of a ball grid array shows the joints as overlapping circles, and the judgement is made from the shape, the brightness and the uniformity of each one. The technique is powerful and it has limits that should be…

Vapour Phase Reflow Compared with Convection Vapour phase soldering heats a board by condensing a saturated vapour onto it, and forced convection heats it by moving hot gas past it. The two transfer heat in different ways, and the difference shows up on boards that carry components of very different…

Cleaning Equipment and Chemistry Selection Cleaning equipment is chosen from the residue that has to be removed and from the geometry that has to be reached, and not from a general preference for one technology. Aqueous, semi aqueous and solvent systems each suit a different combination of flux and assembly.…

Supplier Qualification for PCB Fabrication Qualifying a fabrication supplier is an assessment of capability, not of price or of certificates. A certificate shows that a system exists, while capability shows that the supplier can build the specific board being quoted. The assessment should be made against the features that make…

Through Hole Rework Practice Rework of a through hole joint is harder than rework of a surface mount joint, because the heat has to travel through the board and the alloy is inside a hole. The operation is routine, and the damage it can cause is not. The damage is…

Inspection Lighting and Microscope Setup Inspection is a comparison between what a feature looks like and what the standard requires, and the comparison is only as good as the image. Lighting and magnification decide whether a defect is visible at all, well before the operator’s judgement is involved. The same…