International Business Machines Corporation

Krishna Darbha

David V Caletka

Sanjeev Balwant Sathe

Donald W Henderson

George Henry Thiel

Lawrence P Lehman

Charles Gerard Woychik

Eric A Johnson

Miguel Angel Jimarez

William Infantolino

Varaprasad Venkata Calmidi

Matthew M Reiss

David James Alcoe

Jamil A Wakil

Solder balls, such as, low melt C4 solder balls undergo volume expansion during reflow. Where the solder balls are encapsulated, expansion pressure can cause damage to device integrity. A volume expansion region in the semiconductor chip substrate beneath each of the solder balls accommodates volume expansion. Air-cushioned diaphgrams, deformable materials and non-wettable surfaces may be used to permit return of the solder during cooling to its original site. A porous medium with voids sufficient to accommodate expansion may also be used.

Method to accommodate increase in volume expansion during solder reflow

Solder balls such as, low melt C4 solder balls, undergo volume expansion during reflow, such as may occur during attachment of chip modules to a PCB. Where the solder balls are encapsulated, expansion pressure can cause damage to device integrity. A volume expansion region in the semiconductor chip substrate beneath each of the solder balls accommodated this volume expansion. Air-cushioned diaphgrams, deformable materials and non-wettable surfaces may be used to permit return of the solder during cooling to its original site. A porous medium with voids sufficient to accommodate expansion may also be used.

Method of accommodating in volume expansion during solder reflow

A method and structure to electrically couple a semiconductor device to a substrate that is divided into a plurality of segments. Alternatively, a semiconductor device may be divided into a plurality of segments and the plurality of segments are electrically coupled to a single substrate.

Stress reduction in flip-chip PBGA packaging by utilizing segmented chips and/or chip carriers

A flexible chip carrier with contact pads on its upper surface matching those of the chip with said pads conductively connected to land grid array (LGA) pads on its lower surface matching the those of a card or PCB. The chip carrier is provided with a stiffening layer at the LGA interface. The stiffening layer is mechanically attached to the lower surface of the chip carrier. Holes are formed in the stiffening layer to expose the LGA pads. The holes are then filled with a conductive adhesive material. Compliant LGA bumps are applied to the uncured conductive adhesive material which material is then cured.

Land grid array stiffener for use with flexible chip carriers

Structure to accommodate increase in volume expansion during solder reflow

An electronic package is provided including a substrate, a device mounted on the substrate, and a solder member electrically coupling the device to the substrate. The package includes a dielectric material positioned substantially around the solder member which forms a physical connection between the substrate and the device. The volume of the solder member contracts during melting thereof to prevent failure of the physical connection and/or the electrical coupling between the substrate and the device.

Negative volume expansion lead-free electrical connection

Stress reduction in flip-chip PBGA packaging by utilizing segmented chip carries

A heat dissipating flexible or resilient standoff is mechanically clamped between an electronic module and substrate, such as, PCB. The clamping arrangement comprises a heat sink compressing a thermally conductive flexible interface pad over the upper surface of the electronic module by way of mechanical linkage to the PCB. The heat dissipating flexible standoff provides a force opposing the compression force to thereby reduce stress on solder ball connections between electronic module and PCB. Thermally conductive flexible standoffs in the form of spring arrangements, such as a wire mesh, act to provide heat dissipation by both thermal conduction and thermal convection. A thermally conductive flexible polymer pad and a layer of porous metal foam may also act as thermally conductive standoffs.

Electronic package with thermally conductive standoff

A heat sink structure is formed by stacking a plurality of heat sink layers. Each layer comprises an array of vertically disposed heat dissipating elements extending from a base plate. Cut outs are formed in each of the base plates to form openings so that when the layers are stacked, each of the ascending successive layers has a larger opening than the layer upon which it rests. Cooling may be by forced air or natural convection. With forced air, air impinges on the top of the stack and into the opening in the base plates. Because of diminishing size of the openings in the stack, a portion of the air is forced out the sides of each layer. With natural convection, air is drawn into the sides of each layer and the hot air at the center flows upwardly through the openings with increasing volume as it rises.

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Krishna Darbha