Solder plate reflow method for forming a solder bump on a circuit trace intersection

A method for manufacturing a printed circuit board comprising a solder-bumped copper circuit trace, said trace comprising a first linear section and a second linear section disposed to intersect said first section at an intersection so as to form an angle between the sections that is between about 45 degrees and 135 degrees, said method comprising

• applying a metallic copper plate having a uniform thickness onto a dielectric substrate, said plate including the trace and extending to a region adjacent the trace,
• applying a removable mask onto the copper plate such that the mask covers the adjacent region and defines an opening whereat the trace is exposed,
• immersing the masked copper plate into an electroplating bath containing dissolved tin and lead ions, and cathodically biasing the plate to codeposit metallic tin and metallic lead onto the exposed trace to form an outer plate of tin-lead solder alloy, whereby the mask prevents deposition onto the adjacent region,
• removing the mask from the copper plate to expose the adjacent region,
• etching the copper to remove the adjacent region, whereby the solder plate protects the underlying copper from etching to define the circuit trace, and
• heating to reflow the solder alloy, whereupon molten solder alloy is drawn onto the intersection from the adjacent sections to form a solder bump.