Impedance Controlled Connector Launch Design for High Speed A high speed link is usually designed as a clean transmission line, and then it has to pass through a connector. The launch, meaning the transition from the board traces into the connector footprint and out again, is where most of the…

Copper to Board Edge Clearance Rules in PCB Layout A board is cut out of a panel by a router or a punch, and both operations are less precise than the imaging that created the copper. Keeping copper away from the outline is what prevents a routed trace from shorting…

Depanelization Stress And Component Cracking The moment a board is broken out of its panel is the moment it sees the largest mechanical load of its life. The laminate is bent to shear the tabs or to snap the scored web, and that bend travels through the board to every…

Via Barrel Fatigue Design Guide A via barrel is a copper tube inside a laminate, and the laminate expands about five times as much as the copper in the thickness direction. Every temperature cycle therefore pushes and pulls the barrel, and after enough cycles a crack starts at the corner…

PCB Data Package Requirements Guide A PCB data package is the set of files and drawings that a fabricator needs to build the board. It is easy to send too little and it is expensive to send too much in the wrong form. A package that leaves a question open…

Via Fencing and Stitching for Effective PCB Shielding A ground plane looks like a solid reference until a signal changes layer next to it. Where a trace drops through a via, the return current has to move from one plane to another, and if there is no nearby path it…

Test Point Design For In Circuit Test Fixtures In circuit test works by pressing a bed of nails against the underside of the board and measuring each net. The nails are spring loaded probes, and each one has to land on a surface that is flat, clean, of a known…

Microvia Reliability Design Guide A microvia is a small hole, usually below 0.15 mm in diameter, that connects two adjacent layers in a high density board. It is drilled with a laser rather than with a mechanical bit, and it is the feature that allows a fine pitch device to…

Fiducial: Key Checks Before Release Every automated machine on an assembly line finds the board before it does anything else. The fiducial is the mark it finds, and the accuracy of the whole operation depends on how well that mark is made. A printer, a placer, an optical inspection system…

Silkscreen Legibility Rules Guide Silkscreen legibility is the difference between a board that can be assembled and repaired by anyone and one that requires the layout file to be opened. The markings carry reference designators, polarity marks, pin one indicators and version numbers, and every one of them is printed…