Board Level Thermal Testing Methods A thermal measurement on a finished assembly is the only way to know whether the design removes heat as intended, and it is usually done with a thermocouple, an infrared camera or both. The measurement is simple and the interpretation is where the care is…

PCB Drill and Hole Quality A drilled hole is the foundation of every plated connection, and its quality determines whether the plating adheres and whether the barrel survives thermal cycling. The defects are small and the consequences are large. The process variables are the drill condition, the entry and exit…

Laser Marking and Traceability on PCB Assemblies A mark on a board is useful only if it can be read. A laser mark that is applied to the surface has to survive every process step that follows it, and the reading has to work at the stations where it is…

Reflow Cooling Rate Effects on Joints The cooling part of the reflow profile is treated as a detail, and it is not. The rate at which a joint passes from liquid to solid determines the grain structure of the alloy, the growth of the intermetallic layer and the stress that…

Hand Soldering Rework Process and Control Hand soldering survives in production because some joints cannot be reached by a machine, and it is judged by the same criteria as every other joint. An iron is a heat source with a control loop, and the quality of the result comes from…

Press-Fit Connector Installation and Plated Through Hole Tolerance A press-fit connector is held in a board by deformation, not by alloy. The pin is pressed into a plated through hole and the elastic and plastic deflection of the pin body creates a gas tight contact against the barrel wall. No…

Solder Paste Print Speed and Pressure Settings Print speed, squeegee pressure and separation speed are the three printer settings that operators adjust most often and understand least. Each of them changes the way the paste behaves in the aperture, and the three interact. A setting that works for one aperture…

Electroless Nickel Bath Maintenance and Control Guide Electroless nickel is the underlayer that most high reliability surface finishes are built on, and the bath that produces it is one of the most temperamental chemistries in the plating shop. It deposits without current, so it coats every wetted surface evenly, including…

AOI Programming, False Calls and Escape Rate Automatic optical inspection finds what its program has been taught to find, and it reports what its rules have been set to report. The escaped defect and the false call are therefore both consequences of the same decisions, and a program is judged…

Copper Roughness and High Frequency Insertion Loss At high frequency the current no longer flows through the whole conductor. It crowds towards the surface, and the roughness of that surface becomes part of the electrical path rather than a mechanical detail. Copper that was specified for its thickness is then…