Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-08-07
2001-09-18
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C029S832000, C165S185000, C257S706000
Reexamination Certificate
active
06292369
ABSTRACT:
BACKGROUND OF THE INVENTION
For packaging of integrated circuit chips (especially high power chips), the ability to dissipate heat effectively away from the chip and out of the packaging module is very important. The ability of the module to dissipate heat generated by the chip(s) is generally a function of the quality of the primary heat dissipation path from the chip to the external surface of the module.
In module designs such as those described in U.S. Pat. 5,396,403, thermal paste or some other thermally conductive compliant material is used at a point in the primary heat dissipation path from the chip to the external surface of the module. Interfaces (where heat has to cross from one material to another) are generally the weakest link in the heat dissipation path (i.e., they have significantly lower thermal conductivity than other components of the heat dissipation path), even when they are filled with thermally conductive compliant materials.
Some of the advantages of module designs utilizing thermally conductive compliant materials are that the materials have the ability to accommodate statistical variations in thickness of chips to be housed in the module, height of the solder connections (in the case of flip chips packaging), lid cavity depth, thickness of the seal, substrate camber, etc. The ability to control variations in the various component dimensions is difficult, especially where the components may come from different manufacturers or where reworking or modification of components may be required. This problem is especially apparent where large scale commercial production is involved (i.e., a high throughput of modules).
Thus, there is a desire to further improve the thermal performance of electronic package modules in an economical way.
SUMMARY OF THE INVENTION
The invention provides lid structures and packaging modules having improved heat dissipation performance. The lid structures and modules of the invention are characterized by a customized lid understructure which enables a reduction in the amount of thermally conductive compliant (non-rigid) material in the primary heat dissipation path. The invention also encompasses methods for making the lid structures and modules of the invention wherein the lid understructure is customized for the chip(s) to be housed. The methods of the invention enable the reduction of the amount of low thermal conductivity material in the primary heat dissipation path (from the chip through the lid in modules).
In one aspect, the invention encompasses a lid structure for an electronic module containing an integrated circuit chip, the lid structure comprising:
(a) a lid member adapted to be sealed to the module,
(b) a primary heat dissipation path from a chip contained in the module to the lid member, the heat dissipation path comprising:
(i) a solid customized understructure extending from the lid member toward a chip contained in the module, and
(ii) a thermally conductive compliant material between the customized understructure and the chip.
In another aspect, the invention encompasses an electronic module housing one or more integrated circuit chips, the module comprising:
(a) a substrate,
(b) an integrated circuit chip mounted on the substrate,
(c) a lid member adapted to be sealed to the substrate, the lid and the substrate defining a space for containing the integrated circuit chip, and
(d) a primary heat dissipation path from the chip contained in the space to the lid member, the heat dissipation path comprising:
(i) a solid customized understructure extending from the lid member toward a chip contained in the module, and
(ii) a thermally conductive compliant material between the customized understructure and the chip.
The customized understructure preferably comprises a material selected from the group consisting of solder, thermally conductive thermosetting resin, thermally conductive thermoplastic resin or other material which can be easily deformed at a temperature compatible with the integrity of the module components and chip(s), but not undergoing substantial plastic deformation in the operating temperature range of the module or the temperature at which the lid structure is to be sealed to the chip-carrying substrate. The thermally conductive compliant material is preferably compliant in the operating temperature range and sealing temperature range of the module.
The lid structures and modules may further contain one or more heat spreader members in the primary heat dissipation path. If desired, the lid structures and modules of the invention may be adapted for housing a plurality of chips.
In another aspect, the invention encompasses a method of making an electronic module for containing at least one integrated circuit chip, the method comprising:
(a) providing a substrate having an integrated circuit chip mounted thereon,
(b) providing a lid structure adapted to be sealed to the substrate,
(c) providing a shim and a customizable understructure material, the customizable understructure material being positioned between the shim and the lid member and the shim being positioned between the customizable understructure material and the chip,
(d) moving the lid member toward the substrate, whereby the customizable understructure material is deformed,
(e) allowing the deformed understructure material to become substantially rigid, the deformed understructure material being adhered to the lid member,
(f) moving the lid member and deformed understructure away from the substrate,
(g) removing the shim from between the deformed understructure and the chip,
(h) applying thermally conductive, compliant material between the chip and the deformed understructure,
(i) sealing the lid member to the substrate to provide a primary heat dissipation path from the chip through the thermally conductive, compliant material and the deformed understructure to the lid member.
The customizable understructure preferably comprises a material selected from the group consisting of solder, thermally conductive thermosetting resin, thermally conductive thermoplastic resin or other material which can be easily deformed at a temperature compatible with the integrity of the module components and chip(s), but not undergoing substantial plastic deformation in the operating temperature range of the module or the temperature at which the lid structure is to be sealed to the chip-carrying substrate. The thermally conductive compliant material is preferably compliant in the operating temperature range and sealing temperature range of the module.
Where the customizable understructure is thermoplastic or a solder-material, the methods of the invention preferably comprise heating the customizable understructure to facilitate the deformation in step (d). In such case, step (e) would comprise cooling (letting cool) the customized material. Where the customizable understructure is thermosetting, then step (d) may be performed at a temperature where the thermosetting material either does not cure or cures at a slow enough rate to allow the desired deformation to take place. In such case, step (e) may comprise elevating the temperature of the deformed thermosetting material to cause or accelerate curing.
If desired, a removable shim may be provided at the periphery of lid member in step (c) to provide a preset spacing for a desired sealing configuration or to allow use of a thicker shim between the customizable understructure and the chip without increasing the effective gap for the compliant material. Also, a heat spreader member may be provided in step (c) between the shim and the deformable understructure component whereby the spreader remains in the primary thermal dissipation path between the chip and the lid member.
In an alternative embodiment, step (c) comprises placing a shim only about the periphery of the lid member where a thick sealing member (i.e., a seal ring or other thick section sealing means is used) in step (i). The gap for compliant material would then be defined by the differential thickness of the shim compared to the sealing member. In a
Daves Glenn G.
Edwards David L.
Capella Steven
International Business Machines - Corporation
Tolin Gerald
LandOfFree
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