Solder Wicking Defects in Through-Hole and Cable Joints Solder is supposed to stay where the joint is, and most of the time it does. Occasionally it does the opposite: it climbs up a pin, up a wire or into a stranded conductor, away from the connection that needed it. The…

Workmanship Standards, Training and Inspector Qualification Workmanship standards define what an acceptable assembly looks like, and training is what makes them mean something. Without both, the standard is a document that is quoted after a defect rather than a set of habits that prevents it. Why a Written Standard Matters…

Solder Joint Acceptance Criteria and What They Measure A solder joint is a small structure that has to carry current, transfer heat and survive movement, and it is formed in a few seconds. The inspection criteria exist to decide whether the joint that was formed can do those things for…

BGA Rework Process Control Reworking a ball grid array is the most demanding repair operation in electronics assembly. The joints are underneath the package and cannot be seen, the package is thermally fragile, and the board around it carries components that must not be disturbed. A successful rework is the…

Edge Plating And Castellated Holes A module that is soldered onto a mother board as if it were a component needs its connections on the edge or at the edge, so that the solder joint is accessible to the reflow process. Two techniques provide that: plating along the edge of…

Contamination and Cleanliness Measurement on Assemblies Contamination on an assembly is not only a cosmetic problem. It changes the surface insulation resistance, it provides the ions for electrochemical migration, and it can block a connector or a coating. The question is how much is acceptable and how it is measured.…

Hall Current Sensor Circuit Design A Hall current sensor measures the magnetic field that a current produces and reports the current without inserting a shunt in the path. That isolation from the measured circuit is the reason it appears in motor drives, battery management and power supplies, and it is…

Busbar: Design Rules and Process Limits There is a current above which a copper trace stops being a practical conductor. The trace width needed to keep the temperature rise acceptable grows faster than the current, and the board area that the conductor consumes becomes larger than the circuit it feeds.…

Thermal Relief Design For Plane Connections A pad that is connected directly to a copper plane is thermally part of that plane, and that is exactly the problem during soldering. The plane conducts heat away from the joint as fast as the iron or the wave can supply it, so…

Microsection Sample Preparation and Reading Quality A microsection is the only way to see inside a plated hole, and it is also one of the easiest places to produce a false result. The section that is examined is a slice a few micrometres thick, and what it shows depends on…