Immersion Silver PCB Finish: Solderability and Tarnish Immersion silver deposits a thin layer of silver onto the copper by a displacement reaction, the same principle that puts gold on an electroless nickel layer. The result is a flat, solderable finish with excellent electrical properties and a cost between the organic…

Glass Core PCB versus Metal Core PCB: How to Choose Two board constructions are used when an ordinary laminate cannot carry the heat or hold the dimensions demanded by the application. A metal core PCB puts an aluminium or copper base under an organic dielectric, while a glass core PCB…

PCB Manufacturing Process: From Gerber to Finished Board A circuit board passes through dozens of controlled steps between the design file and the finished panel, and most of them cannot be verified by inspecting the final product. Understanding the sequence helps a designer see which of their decisions are easy…

Copper Pour on Outer Layers: When It Helps and When It Hurts Pouring copper over the empty area of an outer layer is one of those steps that is usually recommended and rarely explained. Done well it improves shielding, spreads heat and helps the board survive reflow. Done badly it…

Hybrid Stackup Design: Mixing High Frequency and FR4 An all high frequency board solves every electrical problem and creates a cost problem, because the material alone can be many times the price of an ordinary laminate. A hybrid stackup takes the opposite approach: it uses the expensive dielectric only where…

Capacitor Polarity on a PCB: Markings, Mistakes and Consequences Reversing a polarized capacitor is one of the rare assembly errors that damages the board as well as the component, and it is also one of the easiest to prevent. The marking conventions are consistent once they are understood, and the…

PCB Design File Checks Before You Order Most delays on a prototype order come from questions the fabricator has to ask before the data can be processed. The board is quoted from the design files once they are converted into production data, and the fabricator never sees the schematic, so…

Any Layer HDI PCB: Stackups, Microvias and Build Sequence Any layer HDI removes a constraint that older high density designs accepted as a rule. In a conventional HDI stack the microvias connect only the outer layers to the next one, so a signal that has to reach an inner layer…

PCB Thermal Deformation: Tg, CTE and Z-Axis Expansion A circuit board changes shape when it is heated, and the change is not uniform. The laminate expands more in the thickness direction than in the plane, the copper expands less than the resin, and above a certain temperature the resin softens…

Custom Shape PCB: Outline Design and Milling Tolerance Not every board is a rectangle, and once the outline stops being a rectangle it becomes a manufactured feature with tolerances rather than a boundary. A custom shape PCB is used when the enclosure, the mounting arrangement or the optical path dictates…