Selective Solder Process Windows for Plated through Hole Components
Selective solder process windows require matching top-side preheat above 110C with precise 3-second pin dwell times to achieve 75 percent Class 3 barrel fill.
Non Wetting Nozzle
Flow Director
A selective soldering nozzle manufactured with a surface that molten solder cannot adhere to provides a stable, directional flow of liquid alloy. This component, known as a non wetting nozzle, is typically made from stainless steel with a specialized surface treatment or ceramic coating. It allows the molten solder to emerge from the center and flow downward over the outer edges without wetting the nozzle walls.
Fluid Dynamics
Wetting nozzles require constant maintenance to ensure even coating, whereas the untreated or ceramic surfaces of non-wetting alternatives prevent the solder from clinging to any one side. This resistance to wetting ensures a highly symmetrical solder wave that does not drift during operation. Consistent wave height and shape are achieved because the fluid flow depends entirely on the pump speed and nozzle geometry rather than the surface chemistry of the metal tip.
Spatter is minimized because there is no solder buildup to detach randomly during the process.
Maintenance Requirement
Regular mechanical cleaning is not required to maintain the flow profile of these tips, reducing operator intervention. Daily inspections are still necessary to detect any micro-cracks or wear in the protective coating that could allow solder to wet the surface. Replacing the nozzle becomes necessary when the non-wetting properties degrade.