Reflow Cooling Rate: 6 Rules for Strong Solder Joints Reflow cooling rate is the speed at which a board leaves the molten state, and it is the part of the profile that receives the least attention. The ramp up is watched closely because it protects components, while the ramp down…

Plating Bus Bar: 6 Rules for Even Current Distribution The plating bus bar is the conductor that carries current from the rectifier to the cathode rack, and it decides how evenly that current is shared between the panels hanging on the rack. It is heavy copper for a reason: the…

Drill Room Humidity: 6 Rules for Stable Drilling Drill room humidity is controlled because the laminate that arrives at the drilling machine is not a dry material. It absorbs water from the air, and the amount it holds changes with the season, the storage room and even the time of…

Ultrasonic Soldering for Fluxless PCB Joints: 7 Process Rules Ultrasonic soldering uses a vibrating tip to break up the oxide film on a metal surface while the molten alloy wets it. The vibration sets up cavitation in the liquid solder, and the collapsing bubbles scrub the surface clean at a…

Board Drying After Cleaning: 6 Rules for Dry Panels Board drying is the last operation in the cleaning line and the one most often treated as an afterthought. Water that stays on the surface carries dissolved material with it, and when the water finally leaves, that material stays behind as…

Compressed Air Dew Point Control for PCB Assembly: 7 Rules Compressed air touches the product more often than most process engineers expect. It sprays flux, it blows solder paste and debris off a panel, it actuates dispensers and clamps, it dries boards after cleaning and it feeds the ionisers that…

Resistance Soldering for Heavy PCB Joints: 6 Setup Rules Resistance soldering passes a low voltage, high current through a carbon electrode and the joint itself, so that the heat is generated by the electrical resistance of the parts being joined rather than by a heated tip. The joint reaches temperature…

Washer and Fastener Seating for PCB Hardware: 7 Rules A washer is a small part that decides how the load from a fastener is distributed into a printed circuit board. Used properly, it spreads the clamping force over an area large enough that the laminate is not crushed, protects the…

Halide-Free Flux: How Activation Works Without Halides A halide-free flux is one whose activator system contains no chloride or bromide compounds, or contains them below the limit defined by the applicable flux specification. The activators still have to remove metal oxide, so the formulator achieves that with organic acids and…

Four Point Bend Testing for Solder Joint Reliability Four point bend testing loads a populated board so that it curves between two inner supports while being pushed by two outer rollers. The arrangement produces a region of uniform bending moment between the inner supports, which means the joints inside that…