Capillary Displacement
Molten solder migration between adjacent copper features occurs when surface tension dynamics exceed the constraints of a solder mask bridge. This inter-tow flow often results in unintended electrical shorts during the reflow phase of printed circuit board assembly. Precise alignment of the deposition pattern relative to the pad geometry prevents this migration.
Small solder volumes reduce the pressure that drives liquid metal across the substrate surface.
Thermal Geometry
Controlled heating profiles manage the viscosity of the alloy to inhibit the movement of inter-tow flow. High ramp rates influence the speed at which the alloy transitions from a paste to a liquid state. Uniform heat distribution across the assembly reduces the localized gradients that pull the molten material toward neighboring conductors.
Extended soak periods provide the flux enough time to clear oxides before the metal liquefies. Careful optimization of these thermal parameters guarantees the integrity of the connection.
Inspection Protocol
Automated optical systems detect the presence of stray solder by comparing the actual footprint against the design file. Vision software identifies deviations where the inter-tow flow creates a physical bridge across the specified clearance gap. High magnification cameras capture images of the joints to confirm the absence of conductive pathways outside the pad boundaries.
Consistent application of these testing methods provides a reliable verification of the fabrication process. Final adherence to the clearance requirements ensures the performance of the electrical circuit.
