As is also known in the art, it is sometimes desirable, and necessary, to provide RFI/EMI shielding to electrical components.

Summary of the Invention With this background of the invention in mind, it is therefore an object of this invention to provide an improved thermal management system. It is also an object of the invention to provide an improved RFI/EMI shielding system.

It is another object of the invention to provide an improved digital computer thermal management system. It is still a further object of the invention to provide an improved thermal management system for portable computers.

It is another object of the invention to provide an improved digital computer RFI/EMI shielding system.

It is still a further object of the invention to provide an improved thermal management system for portable computers.

These and other objects of the invention are attained by providing a thermal management system adapted to provide RFI/EMI shielding. In accordance with one feature of the invention a thermal management system is thermally coupled to, and provides RFI/EMI shielding for, an electrical component.

In accordance with another feature of the invention, a thermal management system is provided for use with a portable computer, such system being adapted to operate with, extract heat from, and provide RFI/EMI shielding to, electrical components used in portable computers.

In accordance with still another feature of the invention, a portable computer is provided having a thermally conductive sheet disposed in the computer in thermal contact with a package for an electrical component, or other heat generating source, used in such computer. The thermally conductive sheet is flexible and has an electrically insulating material disposed on

selected outer surface portions thereof. The computer includes at least one heat radiating surface. A first end of the thermally conductive sheet is in thermal contact with the electrical component, or heat generating source, and a second end is in thermal contact with the radiating surface. The heat radiating surface includes a keyboard mounting plate, a display mounting plate, and the computer case.

In accordance with another feature of the invention, the first end is configured to provided

RFI/EMI shielding the to electrical component in thermal contact therewith.

In accordance with another feature of the invention, a printed circuit board assembly is provided in order in enable upgrading of the computer for use with later developed electrical components, such as later developed microprocessors. The printed circuit board assembly is a daughter-board adapted for connection to a mother-board. The daughter-board has disposed thereon the later developed microprocessor and is adapted to replace a daughter-board having the presently used microprocessor. The printed circuit board assembly includes a multilevel printed circuit board. The multilevel printed circuit board has a thermally conductive layer, or heat conduit, disposed on a lower level. A first heat conductive via is provide having an end portion disposed on a first surface region of the multilevel printed circuit board; more particularly, disposed under, and in thermal contact with, the package for the microprocessor, or other upgradeable, or replaceable, electrical component. The first via passes from such first surface region through an underlying portion of the multilevel printed circuit board to, and in thermal contact with, a first end portion of the heat conduit. A second heat conductive via is provided. The

second via has an end portion disposed on a second surface region of the multilevel printed circuit board laterally displaced from the first surface region. The second via passes from such second surface region through an underlying portion of the multilevel printed circuit board to, and in thermal contact with, a second, laterally displaced end portion of the heat conduit. The thermal management system includes a connector, disposed on the second surface portion of the multilevel printed circuit board. The connector is thermally connected to the end portion of the second via and adapted to mate with, and thermally coupled to, the thermally conductive sheet. With such arrangement, heat generated by the upgradeable, or replaceable electrical component passes successively through the first via, the conduit, the second via, the connector, and the heat conductive sheet to the heat radiating surface of the computer. Brief Description of the Drawings For a more complete understanding of the concepts of the invention, reference is now made to the following drawing, in which:

FIG. l is an isometric, partially broken away, exploded drawing of a portable computer having a thermal management system and RFI/EMI shielding system according to the invention;

FIGS. 2-4 are somewhat simplified, diagrammatical, cross sectional elevation views showing the thermal connection between flexible thermally conductive sheets used in the thermal management system of FIG. 1 to extract heat from, and provide RFI/EMI shielding to, a microprocessor of the computer of FIG. 1; such thermally conductive sheets transferring such heat to heat radiating surfaces of the computer, here the keyboard mounting plate of the computer, shown in FIG. 2, a side of the case of the computer, shown in FIG. 3; and, the

portion of the computer case disposed behind the display of the computer, shown in FIG. 3; FIG. 4 being exploded in the region of the microprocessor package to show the relationship between the flexible thermally conductive sheets and the microprocessor package;

FIG. 5 is a somewhat simplified, diagrammatical, cross-sectional, exploded elevation view of a printed circuit board assembly adapted to enable upgrading of the computer of FIG. 1 for use with later developed microprocessors; FIG. 5A being a cross-sectional view of a portion of FIG. 5;

FIG. 6 is an exploded cross-sectional elevation view of a thermal management system according to an alternative embodiment of the invention; and FIG. 7 is an exploded cross-sectional elevation view of a thermal management system according to another alternative embodiment of the invention.

Description of the Preferred Embodiments Referring now to FIGs. l, 2, 3, and 4, a portable computer 10, here a notebook computer, is shown. The computer 10 includes a plurality of heat radiating surfaces, here a keyboard mounting plate 12 and the computer case 14. The display panel 15 is adapted, in a conventional manner, to fold between an upright position, as shown, and a closed position, via hinges 16. The outer cover 18 of the display panel 15 provides a portion of the computer case 14 when in the closed position. A thermal management system 20 is provided for removing heat generated by an electrical component, here a microprocessor 22. It should be noted that the thermal management system 29 may be used to remove heat from another heat generating source, such as a battery, not shown, disposed in the computer case. The thermal management system 20 includes a plurality of, here three, flexible thermally conductive sheets 24, 26, 28 disposed

in the computer 10. Each one of the sheets 24, 26, 28 has first ends 30, 32, 34, respectively, in thermal contact with the microprocessor 22 and second ends 36, 38, 40 in thermal contact with a display panel 15 mounting plate 42, a side portion 44 of case 14, and, mounting plate 46 for keyboard 48. An electrically insulating material 50 is disposed on portions of the conductive thermally conductive sheets 24, 26, 28 which may be subject unwanted electrical contact with other electrical circuits or wires, for example. The electrically insulating material 50 is used to prevent unwanted electrical contact.

Here, such conductive sheets 24, 26, 28 are stamped copper sheets having a thickness of here 0.010 inches. The electrically insulating material 50 is here aluminum oxide filed epoxy paint.

As shown, first ends 30, 32, 34 of the flexible thermally conductive sheets 24, 26, 28, respectively, are thermally coupled to the microprocessor 22. Here, the first end 30 of flexible conductive sheet 24 is bonded by a low melting point solder to the ceramic case, or package, of the microprocessor 22. After bonding the first end 30 to the ceramic case, the first end 32 is bonded to the top of the first end 30 of conductive sheet 30 using the low melting point ceramic epoxy. It should be noted that the first end 32 is stamped with two opposing ear-like portions 54, 56, which protrude outwardly from the edges of the first end 32. The ear¬ like portions 54, 56 are, after being stamped as one piece with the other portions of the conductive sheet 32, folded at right angles to the surface of the first end 32. The length, L, of the ear-like portions 54, 56 are approximately the same as the height, H, of the vertically extending edges 33, 35 of case of the microprocessor 22. The ear-like portions 54, 56 are in

thermal contact with, here bonded to, the opposing vertically extending edges of the case using the low melting point solder.

After bonding the first end 32, the first end 34 of sheet 28 is bonded the top of the first end 32 of conductive sheet 26 using the low melting point ceramic epoxy. It should be noted that the first end 34 of conductive sheet 28 is stamped with two opposing ear-like portions 58, 60 which protrude outwardly from the edges of the first end 34 similar to ear-like portions 54, 56. Thus, the ear-like portions 58, 60 are stamped as one piece with the other portions of the conductive sheet 34, are folded at right angles to the surface of the first end 34. The length of the ear-like portions 58, 60 has two opposing end portion. More particularly, the end portions 58, 60 are approximately the same as the height of the vertically extending edges 61, 63 of case of the microprocessor 22. Here, however, ear-like portion 58 has a slot 62. Slot 62 is adapted to receive the proximal end portion 64 of first end portion 32. The ear-like portions 58, 60 are in thermal contact with, here bonded to the opposing vertically extending edges 61, 63 of the case using the low melting point solder. Thus, all four vertical edges 33, 35, 61, 63, as well as the top surface of the case of the microprocessor 22 are covered with an electrically conductive sheet to provide RFI/EMI shielding to the microprocessor 22.

The second end 36 of conductive sheet 24 is in thermal contact with, here bonded to, the mounting plate 42 of the display panel 18 with the low melting point solder. The second end 38 of sheet 26 is in thermal contact with, here fastened to, the side panel 44 of the notebook computer 10 case 12 with a mechanical screw. The second end 40 of conductive sheet 28 is in thermal

contact with, here bonded to, the panel 46 for keyboard 48, with the low melting point solder.

Referring now to FIG. 5, a printed circuit board assembly 70 is provided in order in enable upgrading of the computer 10 for use with later developed microprocessors, or other upgradeable, or replaceable, electrical component. The printed circuit board assembly 70 is a so-called "daughter-board" adapted for connection to a so-called "mother-board" (not shown) within the computer 10. Thus, the daughter-board 72 has disposed thereon the later developed microprocessor 22' and is adapted to replace a "daughter-board" having the presently used microprocessor 22. The printed circuit board assembly 72 includes a multilevel printed circuit board 72. The multilevel printed circuit board 72 has a thermally conductive layer, or heat conduit 74 disposed on a lower level of the multilevel printed circuit board 72. A plurality of first heat conductive vias 76 is provided having end portions 78 disposed on a first surface region 80 of the multilevel printed circuit board 72. The first plurality of vias 76 pass from such first surface region 80 through an underlying portions of the multilevel printed circuit board 72 to, and in thermal contact with, a first end region 82 of the heat conduit 74. A second, elongated, heat conductive via 84 is provided. The second via 84 has an end portion 86 disposed on, here disposed in, an elongated pocket 90 formed in the printed circuit board 72. Thus, the bottom and side walls of the pocket 90 have a thermally conductive material, here copper. The thermally conductive material is in thermal contact with the top portion of the second via 84. Alternatively, the conductive material on the side walls and bottom of the pocket 90 may be deposited as the conductive vias 84 is formed. The second via 84 passes from the pocket 90,

through an underlying portion of the multilevel printed circuit board 72 to, and in thermal contact with, the second end of the underlying heat conduit 74.

The upgraded microprocessor package 22' is disposed on, and in thermal contact with, the end portions 78 of the plurality first vias 76.

Referring now also to FIG. 5A, the thermal management system includes a connector 91. Connector 91 includes a first connector portion 92, of a thermally conductive material, here copper, disposed in, here thermally coupled to, the conductive side walls and bottom of pocket 90. Here, the first conductor portion 80 is bonded to the pocket 90 with a low melting point epoxy. The first connector portion 92 has an elongated slot 94 adapted to receive a second conductive portion, here a thermally conductive, here copper, rod 94. The slot 94 has an included surface portion 96 and the rod 94 has a matching included surface 98. The surface portions 94, 98 are here at 45 degree angles with respect to the pale of the printed circuit board 72. An upper surface portion 100 is provided with a plurality of drilled and tapped holes 102. The holes 102 pass through the underlying portion of the rod 92 and through the inclined surface 96, as shown. The holes 102 are adapted to receive screws 104.

A first end 106 of a flexible, thermally conductive sheet 108, here copper, is inserted into a region 110 formed between inner surface 112 forming slot 94 and outer surface 114. After region 110 receives the first end 106, screws 104 are screwed into holes 102 until ends 116 engage included surface 98 and thereby cause rod 114 to slide laterally towards the region 110 and thereby firmly wedge, and force, the first end 106 between surface 114 and surface 112. Therefore, first end 112 is thus thermally coupled to via 84 through the

conductive material on the side walls and bottom of pocket 90, rod 114 and member 92. The first and second members 92, 98 form a connector adapted to latch and provide firm physically locking connection to the flexible conductive sheet 108. This ensures that not only will the connector remain locked when the computer 10 experiences mechanical vibration, but also that there is good thermal transfer between the connector and the thermally connective sheet 108. A flexible, thermally conductive sheet is again provided. The flexible thermally conductive sheet 119 again has electrically insulating material 50 disposed on selected portions thereof to prevent electrical short circuits. The other exposed thermal conductive end, not shown, is in thermal contact with the one, or more than one, of the heat radiating surfaces, i.e., the keyboard mounting plate 46, the display panel mounting plate 18, or the side 44 of the case 12, as described above in connection with FIGs. 1-4. The locking mechanism enables the removal of the conductive sheet from the connector to thereby enable removal of the multilevel printed circuit board 72 and the present microprocessor attached thereto. A new board with the new microprocessor can then be attached to the second end 106 of flexible, thermally conductive sheet 108, the other end being connected to the computer case, keyboard mounting plate or display panel mounting plate.

Referring now to FIG. 6, a thermal management system 20' is shown adapted to provide RFI/EMI shielding. Here, however, instead of the first ends 30, 32, 34 of the flexible thermally conductive sheets 24, 26, 28, respectively, providing the RFI/EMI shielding for microprocessor 22', as described above in connection with FIGs. 1-4, a separate RFI/EMI shielding cover 100 is used. Thus, cover 200 is an electrically conductive material, here, for example, aluminum. The

microprocessor 22', disposed on one side of, here the underside of, a substrate, here a printed circuit board 201. Interfaces 202, 204, of thermally conductive, yieldable material, here silicon with boron nitride, are on the upper and lower surfaces of the package for microprocessor 22', as shown. Interface 202 is sandwitched between one surface, here the upper surface of, microprocessor 22' and first, here lower, ends of a plurality of vias 206 formed through the portion of the printed circuit board 201 aligned with, here disposed over, the microprocessor 22', as shown. Interface 204 is disposed between the lower surface of microprocessor 22' and an underlying portion of the inside of the cover 200, as shown. It is noted that interface 202 is larger than interface 204. These interfaces 202, 204 have a low degree of hardness (i.e., provide a low durometer reading) and are thermally conductive. Thus, when the cover 200 is affixed under the, here lower surface of, and four sides of, microprocessor 22' by screws 207, washers 208, and locking nut 209, the interfaces 202, 204 squeeze against the upper and lower surfaces of package for microprocessor 22' to firmly secure the microprocessor 22' within the cover 200. Further, the interfaces 202, 204 eliminate any air gaps which may develop between the upper surface of the microprocessor 22' and the vias 206 and between the lower surface of microprocessor 22' and the aligned inside portion of cover 200. In this way, good thermal contact is provided between the microprocessor 22' and the vias 206 and cover 200. Cover 200, in addition to providing RFI/EMI shielding, provides a thermal transfer structure to radiate heat extracted from the microprocessor 22' as such heat passes from the microprocessor 22' to cover 200 through interface 202, or, transfer such extracted heat to secondary heat sink 210, as shown. In such later

case, an additional thermally conductive, yieldable interface 212 is disposed between the outer surface of cover 200 and the heat sink 210, as shown. Cover 200, preferably, is thermally matched to interface 202, and/or printed circuit board 201, in order to reduce mechanical stresses between the cover 210 and board 201, and/or interface 202. Thus, a system, here including cover 200 and interface 202, extracts heat from, and provides RFI/EMI shielding for, the microprocessor 22'. As noted above, the plurality of thermally conductive vias 206 is formed through the printed circuit board 201 in a region aligned with, here above, the microprocessor 22' and interface 204. Another interface 212 of thermally conductive, yieldable material is disposed between the upper ends of vias 206 and a pedestal portion of a thermally conductive plate 218, here aluminum. If desired, one or more flexible thermally sheets, such as sheets 24, 26, 28 as discussed above in connection with FIG. 1-4 may be used. In such case, the first ends of the flexible thermally conductive sheets 24, 26, 28 would be disposed, in overlaying relationship, between plate 218 and a second thermally conductive plate 220, here aluminum. A thermally conductive grease 222, 224, as shown. The thermally conductive grease is disposed on the inner surfaces of the plates 218, 220, as shown, to provide good thermal conduction (i.e., no air gaps) between the contacted, thermally conductive ends of the thermally conductive sheets 24, 26 28 and the plates 218, 220. Here, the grease 222, 224 is zinc oxide or graphite filled with a synthetic diester. It is noted that here plate 220 is formed with cooling fins 221 to provide an additional primary heat sink. As shown, holes 228, 230, 232, 234 and 238 are formed through the heat sink 210, cover 200, printed circuit board 201, plate 218, and plate 220,

respectively, as shown to receive bolts 207. Nuts and washers, 209, 208 are used for affixation, as indicated.

It should be understood that if the flexible thermally conductive sheets 24, 26, 28 are used, the second ends thereof, not shown in FIG. 6, would be thermally coupled to radiating surfaces of the computer as shown and described above in connection with FIGs. 1- 4. Thus, the thermal management system 20' of FIG. 6 extracts heat from an electrical component, or other heat generating source, here microprocessor 22' and provides RFI/EMI shielding.

Referring now to FIG. 7, a thermal management system similar to that described above in connection with FIG. 6, is shown. Here, a pair of electrical components 22a", 22b" are electrically connected to electrical conductors, not shown, on printed circuit board 201'. More particularly, the electrical connection is here by ball grid arrays 250, 252, as shown. A pair of covers 200a', 200b' is used, one for each one of the electrical component 22a", 22b", respectively, as shown. Here again, at least one flexible, thermally conductive sheet, here a single sheet Sa, Sb, one for each of the components, 22a", 22b", may be used to extract heat from components 22a", 22b", respectively, as indicated. The other ends, not shown, of sheets Sa, Sb would be thermally connected to radiating surfaces of a computer, not shown, as described above in connection with FIGs. 1- 4. Interfaces, not shown, similar to those described above in connection with FIG. 6, would also be included. Having described a preferred embodiment of the invention it will now be apparent to one of skill in the art that other embodiments incorporating its concepts may be used. For example, while three flexible thermally conductive sheets have been used, more, or less, may be used as required. Furthermore, other heat radiating

surfaces of the computer may be used than the surfaces described above. It is felt, therefore, that the invention should not be restricted to the disclosed embodiment but rather should be limited only by the spirit and scope of the appended claims. What is claimed is: