Dry Packing and Component Storage Why Storage Is a Process Components are sensitive to moisture long before they reach the reflow oven. Plastic packages absorb water from the air, and when they are heated quickly that water turns to steam inside the body. The result is internal stress, delamination, wire…

Counterfeit Components: Detection and Avoidance What Makes a Part Counterfeit A counterfeit part is one that is misrepresented: a recycled device sold as new, a lower grade sold as a higher one, a different manufacturer relabelled, or a device that was never made by the brand printed on it. The…

BOM Sourcing and Part Substitution Why the BOM Decides the Project A bill of materials looks like a list, but it behaves like a schedule. Every line carries a part number, a package, a tolerance, a temperature grade and a supplier, and any one of those fields can stop a…

Masking Methods for Coating and Plating What Masking Does Masking protects parts of an assembly from a process that is applied to the whole board, and it is used for conformal coating, for plating and finishing, for potting and for any operation that must not reach a connector, a contact…

Ionic Contamination Testing and Cleanliness Why Cleanliness Is Measured The failure mechanisms that cleanliness testing guards against all need an electrolyte, and the electrolyte is almost always the ionic residue left on the board by the assembly process or by the environment. If the residue is below a threshold, the…

No-Clean Flux Residue and Its Risks What No-Clean Means A no-clean flux is formulated so that its residue can be left on the assembly without causing a reliability problem, and the process is designed around that assumption. In practice the term describes a chemistry rather than a guarantee: the residue…

Solder Preforms and Pin-in-Paste Assembly The Problem A through-hole joint needs a fillet on both sides of the board to be mechanically sound, and the volume of solder that requires is far more than the paste that can be printed onto a pad at a normal stencil thickness. In a…

Shield Can Assembly: Footprint and Solder The Can as an Assembly A shield can is a mechanical part that is also an electrical one, and getting it onto a board reliably is an assembly problem rather than a layout problem alone. The can is a large, thin, flat metal part…

Humidity and Condensation Testing Why Humidity Is Tested Moisture is involved in a large share of field failures that are not mechanical: it accelerates corrosion, it enables electrochemical migration and conductive anodic filament growth, it changes the dielectric properties of the laminate, it degrades the adhesion between the materials, and…

Thermal Cycling Tests for Assemblies What Cycling Tests A thermal cycling test exposes an assembly to repeated changes in temperature and measures how long it survives. The mechanism it targets is the difference in expansion between the materials: the laminate, the copper, the solder and the component package all expand…