Barrel Crack: Preparation, Placement and Process Control A barrel crack is a fracture in the copper plating inside a plated through hole, usually running around the circumference or along the length of the barrel. It appears after thermal cycling rather than at manufacture, which is what makes it a reliability…

Thermocouple Wire: 6 Choices That Change a Profile Thermocouple wire decides what a reflow profile actually measures, and a poor choice turns a good oven into an unknown one. The wire carries the tiny voltage that represents temperature, and anything that distorts that voltage, from the alloy of the conductors…

Solder Paste Powder Size: 6 Rules for Choosing Type 4 or Type 5 Solder paste powder size is the classification that describes how large the alloy particles are, and it is written as a type number from 1 to 8. The number rises as the particles get smaller, so a…

Solder Mask Application: 5 Methods Compared Solder mask application is the step that covers the copper that must not be soldered, and the method chosen decides the thickness that ends up over a trace, in a via and along an edge. Screen printing, curtain coating and spray coating are the…

Component Lot Codes: 6 Controls for Traceability A lot code is the identifier that ties a unit of material to a batch, and it is the smallest piece of information that makes traceability work. Without a lot code, a quality alert from a supplier cannot be acted on, because there…

PCB First Pass Yield Risks: What Could Go Wrong Buyers and engineers often focus on the finished product and forget the production line behind it. In practice, most field failures can be traced back to process decisions made during assembly. Understanding PCB first pass yield risks gives you a practical…

Core Baking Before Lamination: 6 Rules for Dry Prepreg and Core Core baking is the drying step that removes absorbed moisture from inner layer cores and, where the process requires it, from prepreg before the stack goes into the press. It is a short operation with an outsized effect, because…

Self Alignment: How Reflow Pulls Components Into Place Self alignment is the tendency of a component to move into the centre of its pad pattern while the solder is molten. Molten solder forms a fillet with a defined surface area, and surface tension drives the system toward the shape with…

Mask Window Design: 5 Rules for Solder Mask Openings A mask window is the opening in the solder mask that exposes the copper pad, and its size decides how much bare metal the process leaves around the joint. Too small a window and solder cannot wet the full pad; too…

Immersion Heater Failure: 5 Signs in a Solder Pot An immersion heater is the element that melts and holds the alloy in a solder pot, usually housed in a tube of stainless steel that sits in the bath. Heat passes through the tube wall into the alloy, so the tube…