Copper Trace Width Tolerance and Etching Control on PCBs Trace width is one of the first dimensions a designer specifies and one of the last to be measured properly. The number on the drawing is a target, and what arrives on the board depends on the imaging, the etching, the…

PCB Document Control Guide Document control is the discipline that makes sure the version of a document being used is the version that the shop intends. In a board shop that means the drawing, the stackup, the drill program, the work instruction, the setup sheet and the inspection criteria all…

PCB Gauge Calibration Guide Gauge calibration is the evidence that the instruments a shop uses to accept or reject product are themselves trustworthy. It is easy to treat as paperwork, and it becomes important the moment a customer asks how a thickness figure was obtained. A calibration system has three…

Copper Balance And Thieving On PCB Layers Copper balance is the degree to which the copper on a layer is distributed evenly across the panel. It affects two things that matter after the board is finished: the uniformity of the plating that is deposited in the holes, and the flatness…

Annular Ring: Key Checks Before Release The annular ring is the band of copper that surrounds a drilled hole on a pad. It has to be wide enough that the hole can be drilled off centre by the full tolerance of the process and still leave copper all the way…

PCB Measurement System Analysis Guide Every number a board shop uses to control a process comes from a measurement, and every measurement carries its own variation. Measurement system analysis is the work of finding out how much of the variation in a set of readings comes from the gauge and…

Solder Mask Adhesion Testing And Cure Solder mask adhesion is the bond between the cured ink and the surface beneath it, and it is what keeps the mask in place through reflow, through handling and through the thermal cycling of the product’s life. When the bond is weak the mask…

Impedance Test Coupon: Preparation, Placement and Process Control A controlled impedance board is only as good as the evidence that its traces have the impedance the design intended. That evidence comes from a coupon built on the same panel, with the same stackup and the same etch process, whose traces…

PCB Operator Training Program Guide Operator training decides how much of the shop’s process capability actually reaches the product. A process can be specified correctly, measured correctly and still produce scrap because the person running it was shown the task once, on a different machine, by someone who was also…

Solder Paste Open Time and Stencil Dwell Control on SMT Lines Solder paste is a suspension of metal powder in flux, and it begins to change as soon as it is exposed to air. Solvent evaporates, the flux thickens and the powder begins to oxidise, so a deposit that prints…