Conductive Adhesive Assembly in Electronics Manufacturing Conductive adhesive joins and conducts with a polymer rather than with a molten alloy. It is chosen when the temperature required for soldering is the problem: a component that cannot survive reflow, a substrate that is not solderable, a heat sensitive structure or a…

Conformal Coating Application Control Conformal coating protects a finished assembly from moisture, contamination and, in some products, from mechanical abrasion. It only does so where it is present, and the failure modes of coating are almost all coverage failures: a thin edge, a shadowed area between components, a connector that…

Solder Mask Thickness: Design Rules and Process Limits Solder mask is applied as a thin liquid coating, imaged and cured, and its thickness is one of the least examined parameters on a fabrication drawing. That is a mistake, because thickness decides how well the mask covers the copper it is…

Fiducial: Design Rules and Process Limits A placement machine does not know where the board is. It knows where it thinks the board is, based on the fiducials it can see, and every subsequent placement is referenced to that measurement. Poor fiducials therefore produce a systematic offset that affects every…

Press Plate Flatness and Lamination Quality Control The press plate is the tool that transfers pressure and heat from the platens to the stack, and a plate that is not flat will not distribute either of them evenly. The result is a panel that is thinner in one area than…

ESD Safe Rework and Tool Grounding Rework is the point at which a board that has already survived the assembly process is most exposed to static damage. A soldering iron that is not properly grounded can inject charge into the joint it touches, a bench that has lost its mat…

Adhesive Cure Verification on the Line An adhesive that looks cured may have reached a fraction of its strength. The cure is a chemical reaction that proceeds with time and temperature, and verifying it means measuring rather than touching. What the Schedule Controls The schedule sets the degree of cure,…

Support Tooling and Pallet Design in Assembly A board is a flexible sheet carrying rigid parts, and every process on the line applies a load to it. Printing presses the stencil against it, placement pushes components into paste, and the conveyor and the reflow oven apply heat and their own…

Flux Residue and Coating Adhesion Control Flux residue is what remains on the board after soldering, and it has to be either harmless or removable. Whether it is harmless depends on what is applied over it, and a coating that is applied to a residue-contaminated surface is the classic way…

Copper Filled Via Reliability in Multilayer Boards A filled via is a plated hole that has been plugged with a conductive or non conductive material so that the surface can be used as a pad. The technique is what makes via in pad possible, and it is used on every…