Board Labelling and Traceability Through Assembly A board that cannot be identified cannot be controlled. Traceability begins with a marking that survives the process, continues with a record that links the board to its build data, and ends with a system that can find every affected unit when something goes…

Wave Solder Bath: Design Rules and Process Limits A wave solder bath is a working alloy that accumulates everything the process brings into it. Copper dissolves from the boards, gold from the finishes, iron from the pot and the pump, and flux residues collect on the surface, so the alloy…

Connector Selection Design Guide Connector selection is usually done late, from a catalogue, by whoever has the fewest other tasks. That is the wrong order. The connector sets the pin count, the board outline, the panel height and the assembly method, and a connector chosen at the end of a…

Solder Mask Exposure And Registration Control Solder mask is applied as a liquid or a dry film over the whole board and then patterned by light. The exposure step decides where the mask stays and where it is removed, and the registration of that pattern to the copper underneath decides…

ESD Safe Handling of Boards and Assemblies Static damage is the defect that leaves no evidence behind. A device that has been exposed to a discharge may fail immediately, may drift slowly, or may pass every test and fail in the field after a month of use, and nothing about…

Copper Foil Roughness And High Frequency Loss At low frequencies the resistance of a trace is set by its cross section, and the surface of the copper can be rough or smooth without consequence. As the frequency rises, the current stops using the whole conductor and crowds into a thin…

Assembly Drawing and Notes for PCB Production An assembly drawing is the document that tells the factory what the designer intends. When it is complete, the operator never has to guess; when it is thin, every guess becomes a defect that someone has to explain later. Most assembly problems that…

SMT Adhesive Dispensing And Dot Profile Control Adhesive dispensing is the operation that places a bead of surface mount adhesive to hold components to the underside of a board so that they survive wave soldering, and sometimes so that they survive a second reflow on the other side. It is…

Sheet Metal Chassis Grounding Guide Chassis grounding is the connection between the electrical reference of a board and the metal structure around it. The connection is made for two reasons: to give the return current a large, quiet path and to hold the enclosure at a defined potential. It is…

Chip Component Crack Causes in SMT Assembly A cracked chip component is one of the most common defects on a mature assembly line, and it is also one of the least visible. The body may look intact while a fracture runs through the ceramic, and the part passes final test…