Particle Specification
Fine spherical metal alloy granules measuring between 15 and 25 microns regulate the deposition performance during high density printed circuit board assembly. The industry designates type 5 solder powder for applications where aperture dimensions fall below 200 microns. Uniformity in size distribution minimizes the risk of solder balling while ensuring sufficient flux activation across the landing area.
Consistent spherical geometry promotes even flow during the reflow heating cycle.
Application Constraint
Precision requirements dictate the use of this material for fine pitch components such as 0.3 millimeter ball grid arrays or micro-leadframe devices. Standard stencil printers struggle to release coarser pastes through openings sized for these miniaturized connections. Depositing paste with larger granules creates physical bridges that obstruct the paste through the stencil apertures, leading to insufficient volume or voids in the resulting joint.
Manufacturers balance the smaller particle size against the heightened oxidation rate occurring during storage due to the greater total surface area of the finer metal.
Inspection Parameter
Automated optical systems and X-ray stations verify the presence of solder deposits following the print process to detect clogging or bridging caused by the fine metal structure. Technicians monitor the rheology of the carrier vehicle to ensure the paste maintains stable viscosity when subjected to the high shear forces of the squeegee blade. Poor suspension stability results in particles settling within the paste during high-speed production runs, causing shifts in the metallurgical composition at the site of the joint.
Controlled cooling rates after reflow prevent the formation of dendritic growth or micro-cracks in the brittle solder matrix.
