Underfill And Low Temperature Cure Adhesives A module that combines a sensor, a flex circuit and a mechanical frame has joints that a solder alloy alone cannot protect. The components are small, the substrates expand at different rates, and some of the parts are sensitive to heat. An adhesive performs…

Copper Pour: Islands, Minimum Width and Stitching A copper pour fills the empty area of a layer with copper connected to a net. It is usually added for thermal or shielding reasons, and a pour that is drawn without rules produces islands, slivers and thermal problems. What a Pour Is…

Antipad Design: Clearance, Ring and Plane Integrity Every via in a plane requires a clearance hole around it, called an antipad, which removes copper from the plane. The size of that hole determines whether the design works and whether the plane still does its job. What the Antipad Must Guarantee…

Schottky Diode Package Selection For Power Paths A Schottky diode is chosen for two properties that a ordinary silicon rectifier cannot match: a low forward voltage drop at moderate current, and a junction that stores almost no charge when it switches. Those properties come from the metal semiconductor junction itself,…

PCB EMC Design: Suppress, Divert, Protect Electromagnetic compatibility is usually treated as a test that happens at the end of a project. It is better understood as three problems that can be solved in the layout: a source that radiates, a path that couples, and a victim that is sensitive.…

Microcontroller Output Modes: Open Drain and Push Pull A microcontroller pin is not a switch. It is a driver with a defined output stage, and whether that stage can pull the line high, sink it low or only do one of the two decides how the net is wired, how…

Rigid Flex PCB Development: Where the Two Boards Meet A rigid flex board is not a flexible circuit with a stiffener glued on. It is a stack in which rigid and flexible layers are laminated together in one construction, so that a single part can carry connectors and processors in…

PCBA BOM and the Materials Behind a Circuit Board A bill of materials for an assembled board lists more than the components that will be visible on it. Behind every finished panel there is a second list of materials consumed by the fabricator, and understanding that list is what turns…

Flex Circuit Push Test Method And Criteria A flex circuit is thin, compliant and difficult to grip, which makes the strength of its solder joints harder to assess than on a rigid board. A pull test on a component can distort the circuit before the joint fails, and a bend…

Qualification of a New Fabricator: Audit, Samples and First Article Adding a fabricator or an assembler to the supply base is a project with a beginning and an end. Doing it properly costs a few weeks and prevents the months of problems that follow an unqualified supplier. What Qualification Establishes…