Back to results
US 6,583,515 B1Granted
Ball grid array package for enhanced stress tolerance
AssigneeTexas Instruments Incorporated
InventorsRichard D. James, Leslie E. Stark
Life of this patent
Estimating the term…
Abstract
The thermomechanical stress sensitivity of ball grid array (BGA) solder connections is significantly reduced, when the solder connections solidify in column-like contours after the reflow process—a result achieved by using the solder material in tapered openings of a thick sheet-like elastic polymer adhered to the BGA substrate and selected for its characteristics of non-wettability to solder and volumetric shrinkage greater than solder.
Claims19
An interconnection substrate for use in semiconductor assembly, comprising:
- a support of electrically insulating material having a plurality of contact pads disposed on the surface of said support, said pads having a composition suitable for solder attachment;
- said support surface covered by an adherent, sheet-like elastic polymer tape, said polymer tape being non-wettable by solder and having a coefficient of volumetric shrinkage greater than solder;
- and
- said polymer tape having openings exposing each of said contact pads, whereby the walls of said openings become tapered towards said pads after solder attachment.
1 more element
A semiconductor assembly comprising:
- a substrate comprising a support of electrically insulating material having a first and a second surface;
- a plurality of electrically conductive routing strips integral with said substrate;
- a plurality of contact pads disposed in a pattern on said first surface and connected to said routing strips, said pads having a composition suitable for solder attachment;
- said first surface covered by an adherent, sheet-like elastic polymer, said polymer being non-wettable by solder and having a coefficient of volumetric shrinkage greater than solder;
- said sheet-like polymer having openings exposing each of said contact pads, the walls of said openings tapering towards said pads;
- an integrated circuit chip attached to said second substrate surface;
- solder connections reflowed onto said contact pads such that said solder connections, upon cooling, are shaped in column-like contours and separated from said walls by a gap, whereby each said column-like connection has sufficient length after board attach to act as a stress-distributing joint.
4 more elements
A packaged integrated circuit, comprising:
- a substrate having top and bottom opposing surfaces, said top surface including conductive routing strips and said bottom surface including contact pads;
- an integrated circuit chip mounted on said top surface of said substrate and connected to said conductive routing strips;
- an adherent, elastic polymer sheet covering said bottom surface of said substrate, said sheet including openings aligned with said contact pads, said openings having walls;
- solder connections on said contact pads, said solder connections separated from said walls by a gap.
1 more element
Dependencies are inferred from the claim text.