US 6,293,456 B1 · Methods for forming solder balls on substrates

Abstract

A mask (110; see also 160, 210, 260, 310, 408, 500, 702, 802, 904) having a plurality of openings (cells) is disposed on, or nearly on, the surface of a substrate (102), the openings (112) of the mask being aligned over a corresponding plurality of pads (104) on the substrate. The openings in the mask are filled with solder material (114). A pressure plate (120) is disposed over the mask to capture the solder material in the cells. Heat is directed at the mask (through the pressure plate) to reflow the solder. This is done in an inverted or partially inverted orientation. The stackup (assembly) of substrate/mask/pressure plate may be un-inverted prior to cooling. Mask configurations, methods of mounting the masks, and solder material compositions are described. The methods are robust, and are well suited to fine pitch as well as coarse pitch ball bumping of substrates.

Claims21

Dependent claims

Method for forming solder balls on a substrate having a plurality of pads on a surface thereof, comprising:

disposing a mask on the surface of the substrate, said mask having a plurality of cells, said mask having a surface adjacent the substrate and an opposite surface;
filling the cells with solder material;
closing the cells;
with the substrate at least partially inverted, reflowing the solder material by contacting the opposite surface of the mask with a surface of a heater stage;
during reflow, fully inverting the substrate;
cooling the reflowed solder material;
and
removing the mask.

5 more elements

Dependencies are inferred from the claim text.

Methods for forming solder balls on substrates

Life of this patent

Methods for forming solder balls on substrates

Life of this patent

Abstract

Claims21