Hot Bar Reflow Soldering Guide Hot bar soldering joins a flexible circuit, a flat cable or a fine pitch connector to a board by pressing a heated bar against the joint. The heat is conducted through the joint itself rather than applied to the whole assembly, so the process suits…

Visual Inspection Criteria for Solder Joints in Assembly Visual inspection is the oldest and the cheapest check on a solder joint, and it remains the first line of defence on most assembly lines. It is also the check that varies most between operators, because it depends on eyesight, on lighting…

Solder Preform: Preparation, Placement and Process Control A solder preform is a piece of solder that has been cast or stamped into a shape and placed in a joint before heating. Its purpose is to deliver a defined volume of alloy to a joint that paste or wire cannot fill,…

Laser Soldering Guide for Selective Joints Laser soldering uses a focused beam to heat a single joint. The energy is delivered to a spot a fraction of a millimetre across, and the heat reaches the joint through the solder and the pad rather than through the whole board. It is…

Pin in Paste Process Guide Pin in paste, also called through hole reflow, prints solder paste into the plated holes and onto the pads of a through hole component and then reflows it in the same pass as the surface mount parts. The process removes a second soldering step, and…

Reflow Oven Zone Balancing for Uniform Board Heating A reflow oven is described by its zones, and each zone holds a temperature. What the board experiences is not those setpoints but the result of the heat they deliver, the speed at which the board passes through them and the mass…

Solder Joint Void Acceptance Criteria Explained A void is a gap left inside a solder joint where flux volatiles or entrapped air prevented the metal from filling the volume. Voids are present in almost every joint to some degree, so the question is never whether they exist but whether the…

Press Fit Connector Design and Assembly A press fit connector is held in the board by the elastic deformation of a compliant pin in a plated hole. There is no solder, so the joint depends entirely on the mechanical interference between the pin and the barrel, and the reliability of…

Solder Ball Defect Analysis On Assembled Boards A solder ball is a small sphere of solder that has separated from the joint and remains on the board surface, usually beside a pad or trapped under a component. Balls range from harmless specks to a real risk of a short between…

Impedance Coupon: Preparation, Placement and Process Control A controlled impedance board is only as good as the evidence that it meets the requirement. That evidence is normally a coupon built on the same panel with the same stackup, carrying traces whose geometry is known, so that a measurement can be…