Method and apparatus for solder bumping of printed circuit boards
AssigneeHewlett-Packard Company
InventorStephen J. Gschwend
Life of this patent
Estimating the term…
Abstract
A method and apparatus for preparing printed circuit boards having flattened solder bumps for the mounting of surface mount components is provided. Using well-known techniques, solder paste is screen-printed onto printed circuit boards and reflowed and cleaned to form discrete solder bumps. Using roller machines, the peaks of the solder bumps are flattened and adhesive solder flux is applied to the flattened tops of the solder bumps. The adhesive solder flux holds the surface mount components in position after placement and during vapor phase reflow.
Claims7
A method of forming coated solder bumps on contact areas of a printed circuit board, said method comprising the steps of:
- forming a plurality of solder bumps in a predetermined pattern on said contact areas of said printed circuit board;
- flattening said plurality of solder bumps to form a plurality of flattened solder bumps, each of said flattened solder bumps having a flat top surface at a predetermined height above the surface of said printed circuit board;
- positioning said printed circuit board on a feed table means;
- feeding said printed circuit board between said feed table means and a pair of rollers, said pair of rollers comprising a primary roller and a secondary roller, said primary roller and said secondary roller disposed in parallel spaced relationship adjacent each other, said primary roller and said secondary roller each having opposite directions of rotation such that said primary roller and secondary roller rotate towards each other and the primary roller rotates opposite to the feeding direction of the circuit board forming a flux reservoir in the nip therebetween, said primary roller being coated with a uniform layer of flux by the compressive action of said secondary roller rotating towards said primary roller, the height above said feed table means of said primary roller being adjusted such that at least some of said plurality of flattened solder bumps are in contact with said primary roller, said flux being transferred to said flattened solder bumps in contact with said primary roller by said contact.
Apparatus for applying a coating of adhesive solder flux to a plurality of flattened solder bumps comprising:
- a feed table moveable in a feed direction;
- a primary roller and a secondary roller disposed in parallel relationship adjacent each other in a plane parallel to and above the plane of the feed table;
- and
- rotating means for rotating said primary roller in a first direction opposite the feed direction and for rotating said secondary roller in a second direction opposite to said first direction such that said primary roller and said secondary roller rotate towards each other forming a flux reservoir in the nip therebetween, said primary roller being coated with a uniform layer of said adhesive solder flux by the compressive action of said secondary roller rotating towards said primary roller.
Dependencies are inferred from the claim text.