Solder Bar Purity: 5 Checks Before the Pot Solder bar purity is the freedom of the incoming alloy from elements that raise its melting range, thicken the dross layer or embrittle the joint. A bar can match its nominal composition and still carry enough copper, iron or antimony to change…

Immersion Tin Coating Thickness: 6 Process Controls That Matter Immersion tin is a thin metallic coating deposited by a displacement reaction, where tin from the bath replaces copper on the surface of the pad. It gives a flat, solderable finish at a modest cost, and it is popular for fine…

Solder Pot Temperature Uniformity: 6 Checks Before Production Solder pot temperature uniformity is the spread in temperature across a bath at the moment of soldering, and it matters more than the number on the controller. A pot reading 250 degrees at its thermocouple while one corner of the wave sits…

Dry Cabinet Storage: 5 Rules for MSL Parts A dry cabinet is a closed storage unit that holds relative humidity below the level at which a moisture sensitive component keeps absorbing water. It is not a convenient cupboard for open reels; it is process equipment with a set point, a…

Nitrogen Blanket: 5 Rules for Inert Soldering Atmospheres A nitrogen blanket is an inert atmosphere maintained over the solder joint while it is molten, and its purpose is to keep oxygen away from hot metal. Air contains about 209,000 parts per million of oxygen; a blanket aims for a few…

Selective Soldering Nozzle Choice: 6 Rules for Clean Joints Selective soldering uses a small pumped fountain of molten solder to join individual through-hole pins, one joint or one group at a time. The nozzle is the part that shapes the process: its diameter, its inner geometry and its height above…

Tab Count on a PCB Array: 5 Depaneling Rules Tab count is the number of bridges that hold each board inside its panel, and it decides how much the board can flex before the bridges are cut. The number is usually set by the layout designer and then confirmed by…

Microsection Sample Preparation: 7 Steps to a Trustworthy Cross Section A microsection is a polished slice through a plated hole or a pad, examined under a microscope to show plating thickness, barrel integrity and the interface between copper and laminate. It is the reference method behind most acceptance decisions on…

Wetting Force: Reading a Wetting Balance Curve Correctly Wetting force is the pull that molten solder exerts on a sample when it wets the surface, and measuring it turns solderability from an opinion into a number. The instrument that does it is a wetting balance, which lowers a sample into…

Paste Tack: Why Deposits Lose Hold Before Reflow Paste tack is the adhesion that a printed deposit offers to a component lead or body before reflow. It is what holds a chip capacitor in place while the board travels to the oven, and it is the reason a placement machine…