Footprint Library: Lessons From the Last Product: A Design Review Input The cheapest improvement available to most hardware programs is a short review of the previous product, and it is the one most often skipped because the schedule has already started. The findings are consistent, and they fall into a…

Edge Plating Process Window: Design and Quality Control Edge plating turns the outside wall of a circuit board into part of the electrical and mechanical design. Instead of stopping at the copper layers, the plating wraps around the routed edge and connects the top, bottom and inner planes into one…

Optocoupler CTR Degradation and Design An optocoupler is often chosen as a fit and forget isolation device, but its transfer efficiency falls steadily from the day it is first powered. A design that works perfectly on the bench can fail in the field after a few years because the current…

Flexible Printed Circuits in Electric Vehicle Harnesses A modern vehicle contains more copper than most people expect, and a growing share of it is not round wire. A flexible printed circuit replaces a bundle of individual wires with a flat laminated conductor pattern that follows the shape of the space…

Laser Solder Ball Bonding for Flex Circuit Assembly Soldering a flex circuit with a conventional iron or with a hot air nozzle is a compromise. The iron contacts the joint and conducts heat into the polyimide, and the air nozzle heats everything within reach. Both methods put more energy into…

Controlled Impedance Through Cables And Connectors Impedance is a property of a transmission line, not of the metal in it. The energy that carries a signal at radio frequency travels in the field between the two conductors, guided by the dielectric that separates them, and it is the geometry of…

Why The Board Came Back At The Wrong Characteristic Impedance A designer calculates a trace width for fifty ohms, sends the Gerber files out, and receives boards that measure a few ohms away from the target. Nothing in the design changed, and yet the number moved. The reason is that…

PCB Layout Workflow: From Schematic to Release A layout that is completed out of order costs time twice: once when the work has to be redone, and again when the board fails for a reason nobody anticipated. The sequence below is the one that consistently produces a releasable design, and…

Designing FPC Display Cables for Handheld Products A display cable inside a handheld product is one of the most constrained pieces of interconnect in the device. It has to fit into a gap a few millimetres wide, fold twice on its way from the main board to the panel, carry…

High Precision PCB Base Material: What HDI Really Needs A high precision pcb is defined by its geometry rather than by their marketing: fine lines and spaces, small microvias and a construction that can support them. The base material is what makes that geometry possible, and the parameters that matter…