PCB Design Key Points: Routing, Ground and Decoupling Most of the problems that appear in a finished board trace back to a small number of pcb design decisions taken early: how the signal flows, where the ground reference is, how the supply is decoupled and how much space the routing…

Hand Soldering A QFN: Step By Step A QFN package has no leads to solder. Its connections are flat pads on the underside of the body, arranged around the perimeter, with a large exposed pad in the centre that serves as both the thermal path and, usually, the ground connection.…

Via in Pad Design and Paste Escape for Thermal Pads Via in pad means placing a plated hole directly inside a surface mount land so that the pad serves both as a solder site and as a vertical connection, and it is the standard way to move heat out of…

In-Circuit Test Fixture Design: Probes, Access and Maintenance A bed of nails fixture connects every net on a board to the tester through a spring probe. The design of that fixture determines whether the test is reliable, maintainable and worth the cost of building it. What the Fixture Must Do…

Pcb Design Software: Preparation, Placement and Process Control Choosing a pcb design software package is a decision that outlives the project it is made for. The tool holds the library, the constraints and the fabrication output, and changing it later means migrating all three. What matters is not the length…

Laser Welding for Server Liquid Cooling Plates A liquid cooling plate for a server has to do three things at once: conduct heat from a cold plate or a die into the coolant, contain that coolant at pressure for the life of the machine, and do it with an internal…

Isolation Amplifier Current Sensing Design Measuring current in a motor drive, a battery system or a mains connected converter means placing a sensing element at a potential that would destroy the controller connected to it. An isolation amplifier solves that problem by transferring the measurement across a barrier, and the…

Fine Pitch SMT Production: Six Problems That Appear At Volume Fine pitch surface mount parts pass every sample build and then fail in volume. The reason is that a sample is assembled with attention and a small number of pieces, while a production run is assembled with the process settings…

Current Loop Transmitter Circuit Design A current loop carries a measurement as a current rather than a voltage, which is why it survives long cables, contact resistance and electrical noise that would ruin a voltage signal. The transmitter at the sensor end converts the measurement into a current between four…

Double Sided and Sandwich Metal Core Board Construction A metal core board conducts heat from a component through a thin dielectric into an aluminium base, and the base spreads it sideways into a heatsink or a chassis. The limitation of the simplest construction is that the circuit is on one…