# Patent

## Title
Heatplates for heatsink attachment for semiconductor chips

## Abstract

An apparatus for heatsink attachment. The apparatus includes a substrate, a semiconductor chip on top of and physically attached to the substrate, and a lid on top of the substrate. The lid includes a first thermally conductive material. The apparatus further includes a heatsink on top of the lid. The heatsink includes a second thermally conductive material. The semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip. The lid is disposed between the substrate and the heatsink. The lid includes a first protruding member. The first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction.

## Background
FIELD OF THE INVENTION
The present invention relates generally to semiconductor chips and more particularly to heatplates for heatsink attachment for semiconductor chips.
BACKGROUND OF THE INVENTION
In the prior art, after a semiconductor chip is attached to a printed circuit board, a heatsink is conventionally placed on top of the chip via a heatplate so as to absorb the heat generated from the chip during the chip operation. To hold the heatsink in place, clips are conventionally used to hold the heatsink to the printed circuit board. In other words, areas of the printed circuit board must be used for the clips to hold the heatsink in place. Therefore, there is a need for an apparatus (and a method for forming the same) in which the heatsink is held in place without utilizing areas of the printed circuit board.
SUMMARY OF THE INVENTION
The present invention provides a structure, comprising (a) a substrate; (b) a semiconductor chip on top of and physically attached to the substrate; (c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and (d) a heatsink on top of the lid, wherein the heatsink comprises a second thermally conductive material, wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip, wherein the lid is disposed between the substrate and the heatsink, wherein the lid comprises a first protruding member, and wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction.
The present invention also provides a structure formation method, comprising providing a structure which includes (a) a substrate;(b) a semiconductor chip on top of and physically attached to the substrate, wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip; and (c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and placing a heatsink on top of the substrate, wherein the heatsink comprises a second thermally conductive material, wherein the lid is disposed between the substrate and the heatsink, wherein the lid comprises a first protruding member, and wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction.
The present invention provides an apparatus (and a method for operating the same) in which the heatsink is held in place without utilizing areas of the printed circuit board.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A shows a cross-section view of a structure, in accordance with embodiments of the present invention.
FIG. 1Ai shows a perspective view of the structure of FIG. 1A along a line 1Ai-1Ai of FIG. 1A.
FIGS. 1B-1Biv illustrate a process for forming a lid of FIG. 1A, in accordance with embodiments of the present invention.
FIG. 1C shows a top-down view of the lid of FIG. 1Biv.
FIG. 2A shows a cross-section view of a structure, in accordance with embodiments of the present invention.
FIG. 2B shows a top-down view of a lid of FIG. 2A.
FIG. 3A shows a cross-section view of a structure, in accordance with embodiments of the present invention.
FIGS. 3B-4 illustrates a process for forming a lid of FIG. 3A, in accordance with embodiments of the present invention.
FIG. 5A shows a cross-section view of a structure, in accordance with embodiments of the present invention.
FIG. 5B shows a perspective view of the structure of FIG. 5A along a line 5B-5B of FIG. 5A.
FIG. 6 shows a cross-section view of a structure, in accordance with embodiments of the present invention.
FIG. 7 shows a cross-section view of a structure, in accordance with embodiments of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A shows a cross-section view of a structure 100, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 100 comprises an organic substrate 120 and a chip 140 which is attached to the organic substrate 120. Illustratively, the chip 140 comprises solder balls 112 which electrically connect devices (not shown) of the chip 140 to substrate pads (not shown) of the organic substrate 120. In one embodiment, the organic substrate 120 comprises substrate balls 110 which are electrically connected to the solder balls 112. Illustratively, the structure 100 further comprises an underfill layer 114 which physically holds the chip 140 tightly to the organic substrate 120.
In one embodiment, the structure 100 further comprises a stiffener 130, a lid (also called heatplate) 180, and a heatsink 190. Illustratively, the stiffener 130 and the lid 180 comprise nickel plated copper. In one embodiment, the heatsink 190 comprises aluminum. Illustratively, the stiffener 130 is attached to the organic substrate 120 by an adhesive layer 122. In one embodiment, the lid 180 is attached to the bottom surface 142 of the chip 140 by a thermal adhesive layer 150. Illustratively, the thermal adhesive layer 150 comprises a thermally conductive material. In one embodiment, the lid 180 is also attached to the stiffener 130 by an adhesive layer 160. Illustratively, the heatsink 190 is pressed down by holders 185a and 185b of the lid 180 against a top surface 182 of the lid 180 via a thermal grease layer 170. In one embodiment, the thermal grease layer 170 comprises a thermally conductive material. Illustratively, the structure 100 of FIG. 1A can be electrically coupled to a circuit board (not shown) using the substrate balls 110.
In one embodiment, with reference to FIG. 1A, the structure 100 can be formed as follows. Illustratively, after being fabricated, the chip 140 is flipped up side down and then is attached to the organic substrate 120 using the solder balls 112 of the chip 140 and the underfill layer 114. Next, in one embodiment, the stiffener 130 is physically attached to the organic substrate 120 using the adhesive layer 122. Next, in one embodiment, the lid 180 is (i) physically attached to the stiffener 130 using the adhesive layer 160 and (ii) thermally and physically coupled to the bottom 142 of the chip 140 via the thermal adhesive layer 150. Then, in one embodiment, the thermal grease layer 170 is applied to the top surface 182 of the lid 180. Next, in one embodiment, the heatsink 190 is slid into place in a direction perpendicular to the page. In one embodiment, the heatsink 190 is held in place by the holders 185a and 185b that press the heatsink 190 down against the top surface 182 of the lid 180.
FIG. 1Ai shows a perspective view of the structure 100 along a line 1Ai-1Ai of FIG. 1A.
FIGS. 1B-1Biv illustrate a process for forming the lid 180 of FIG. 1A, in accordance with embodiments of the present invention. More specifically, in one embodiment, the process for forming the lid 180 starts with the lid 180 of FIG. 1B (top-down view). FIG. 1Bi shows a cross-section view of the lid 180 of FIG. 1B along a line 1Bi-1Bi.
Next, in one embodiment, with reference to FIGS. 1B and 1Bi, the lid 180 is bent in directions 182a′ and 182b′ along lines 182a and 182b, respectively, resulting in the lid 180 of FIG. 1Bii. Next, in one embodiment, the lid 180 of FIG. 1Bii is bent in directions 184a′ and 184b′ along lines 184a and 184b, respectively, resulting in the lid 180 of FIG. 1Biii. Then, in one embodiment, the lid 180 of FIG. 3Biii is bent in directions 186a′ and 186b′ along lines 186a and 186b, respectively, resulting in the lid 180 of FIG. 1Biv.
FIG. 1C shows a top-down view of the lid 180 of FIG. 1Biv.
FIG. 2A shows a cross-section view of a structure 200, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 200 is similar to the structure 100 of FIG. 1A except that the structure 200 does not have the stiffener 130 and that a lid 280 of the structure 200 is different from the lid 180 of the structure 100 (FIG. 1A). More specifically, in one embodiment, the lid 280 is similar to the lid 180 of FIG. 1A except that the lid 280 has an opening 282 (not shown in FIG. 2A but shown in FIG. 2B) that allows for closer thermal contact of the heatsink 190 to the bottom surface 142 of the chip 140 via the thermal grease layer 170 (FIG. 2A). Illustratively, the lid 280 is attached to the organic substrate 120 by an adhesive layer 260, whereas the heatsink 190 is pressed down against the bottom surface 142 of the chip 140 by the holders 185a and 185b of the lid 280 via the thermal grease layer 170.
In one embodiment, with reference to FIG. 2A, the structure 200 can be formed as follows. Illustratively, after being fabricated, the chip 140 is flipped up side down and then is attached to the organic substrate 120 using the solder balls 112 of the chip 140 and the underfill layer 114. Next, in one embodiment, the lid 280 is physically attached to the organic substrate 120 using the adhesive layer 260 such that the chip 140 fits in the opening 282 (FIG. 2B). Then, in one embodiment, the thermal grease layer 170 is applied to the bottom surface 142 of the chip 140. Next, in one embodiment, the heatsink 190 is slid into place in a direction perpendicular to the page. In one embodiment, the heatsink 190 is held in place by the holders 185a and 185b that press the heatsink 190 down against the bottom surface 142 of the chip 140 via the thermal grease layer 170.
FIG. 2B shows a top-down view of the lid 280 of FIG. 2A. As can be seen in FIG. 2B, the lid 280 is similar to the lid 180 of FIG. 1C except that the lid 280 has an opening 282. In one embodiment, the formation of the lid 280 is similar to the formation of the lid 180 of FIG. 1Biv.
FIG. 3A shows a cross-section view of a structure 300, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 300 is similar to the structure 100 of FIG. 1A except that the structure 300 does not have the stiffener 130 and that a lid 380 of the structure 300 is different from the lid 180 of the structure 100. More specifically, the lid 380 is similar to the lid 180 of FIG. 1A except that a bottom member 381 of the lid 380 concaves up to create space for the chip 140. In one embodiment, the lid 380 is attached to the organic substrate 120 by an adhesive layer 360.
In one embodiment, with reference to FIG. 3A, the structure 300 can be formed as follows. Illustratively, after being fabricated, the chip 140 is flipped up side down and then is attached to the organic substrate 120 using the solder balls 112 of the chip 140 and the underfill layer 114. Next, in one embodiment, the lid 380 is (i) physically attached to the organic substrate 120 using the adhesive layer 360 and (ii) thermally and physically coupled to the bottom 142 of the chip 140 via the thermal adhesive layer 150. Then, in one embodiment, the thermal grease layer 170 is applied to the top surface 382 of the lid 380. Next, in one embodiment, the heatsink 190 is slid into place in a direction perpendicular to the page. In one embodiment, the heatsink 190 is held in place by the holders 185a and 185b that press the heatsink 190 down against the top surface 382 of the lid 380 via the thermal grease 170.
FIGS. 3B-4 illustrates a process for forming the lid 380 of FIG. 3A, in accordance with embodiments of the present invention. More specifically, in one embodiment, the process for forming the lid 380 starts with the lid 380 of FIG. 3B (top-down view). FIG. 3Bi shows a cross-section view of the lid 380 of FIG. 3B along a line 3Bi-3Bi.
Next, in one embodiment, with reference to FIG. 3Bi, the lid 380 is bent along lines 382a and 382b and then is bent along lines 384a and 384b resulting in the lid 380 of FIG. 3Bii. Next, in one embodiment, with reference to FIG. 3Bii, the lid 380 (i) is bent along lines 386a and 386b, then (ii) is bent along lines 388a and 388b, and then (iii) is bent along lines 390a and 390b resulting in the lid 380 of FIG. 4.
In summary, with reference to FIGS. 1A, 2A, and 3A, the holders 185a and 185b help hold the heatsink 190 in place by pressing the heatsink 190 down against the top surface 182 of the lid 180 (FIG. 1A), or the bottom surface 142 of the chip 140 (FIG. 2A), or the top surface 382 of the lid 380 (FIG. 3A).
FIG. 5A shows a cross-section view of a structure 500, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 500 is similar to the structure 100 of FIG. 1A except that the structure 500 comprises springs 510a and 510b and that a lid 580 of the structure 500 is different from the lid 180 of FIG. 1A. Illustratively, the springs 510a and 510b are elastic structures. An elastic structure is a structure that tends to change its shape when being applied a force and tends to change back to its original shape when the force is removed. In one embodiment, the springs 510a and 510b can have any size and shape provided that the springs 510a and 510b maintain pressure against overhangs 584a and 584b of the lid 580 and horizontal members 192a and 192b of the heatsink 190, respectively. Illustratively, the lid 580 is similar to the lid 180 (FIG. 1A) except that the lid 50 does not have holders (like the holders 185a and 185b of FIG. 1A). Instead, the overhangs 584a and 584b keep the springs 510a and 510b pressing the horizontal members 192a and 192b down, respectively, resulting in the heatsink 190 being pressed down against the top surface 582 of the lid 580 via the thermal grease layer 170.
In one embodiment, with reference to FIG. 5A, the structure 500 can be formed as follows. Illustratively, after being fabricated, the chip 140 is flipped up side down and then is attached to the organic substrate 120 using the solder balls 112 of the chip 140 and the underfill layer 114. Next, in one embodiment, the stiffener 130 is physically attached to the organic substrate 120 using the adhesive layer 122. Next, in one embodiment, the lid 580 is (i) physically attached to the stiffener 130 using the adhesive layer 160 and (ii) thermally and physically coupled to the bottom 142 of the chip 140 via the thermal adhesive layer 150. Then, in one embodiment, the thermal grease layer 170 is applied to the top surface 582 of the lid 580. Next, in one embodiment, the heatsink 190 is slid into place in a direction perpendicular to the page.
Next, in one embodiment, the spring 510a is slid into place between the overhang 584a and the horizontal member 192a of the heatsink 190. Similarly, the spring 510b is slid into place between the overhang 584b and the horizontal member 192b of the heatsink 190. As a result, the heatsink 190 is held in place by the springs 510a and 510b that press the heatsink 190 down against the top surface 582 of the lid 580 via the thermal grease layer 170.
FIG. 5B shows a perspective view of the structure 500 along a line 5B-5B of FIG. 5A. It should be noted that a spring 510b′ of FIG. 5B is an alternative embodiment of the spring 510b of FIG. 5A.
FIG. 6 shows a cross-section view of a structure 600, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 600 is similar to the structure 200 of FIG. 2A except that the structure 600 comprises the springs 510a and 510b and that a lid 680 of the structure 600 is different from the lid 280 of FIG. 2A. Illustratively, the lid 680 is similar to the lid 280 (FIG. 2A) except that the lid 680 does not have holders (like the holders 185a and 185b of FIG. 2A). Instead, overhangs 684a and 684b keep the springs 510a and 510b pressing the horizontal members 192a and 192b down, respectively, resulting in the heatsink 190 being pressed down against the bottom surface 142 of the chip 140 via the thermal grease layer 170.
FIG. 7 shows a cross-section view of a structure 700, in accordance with embodiments of the present invention. More specifically, in one embodiment, the structure 700 is similar to the structure 300 of FIG. 3A except that the structure 700 comprises the springs 510a and 510b and that a lid 780 of the structure 700 is different from the lid 380 of FIG. 3A. Illustratively, the lid 780 is similar to the lid 380 (FIG. 3A) except that the lid 780 does not have holders (like the holders 185a and 185b of FIG. 3A). Instead, overhangs 784a and 784b keep the springs 510a and 510b pressing the horizontal members 192a and 192b down, respectively, resulting in the heatsink 190 being pressed down against the top surface 782 of the lid 780 via the thermal grease layer 170.
In summary, with reference to FIGS. 5A, 6, and 7, the springs 510a and 510b help hold the heatsink 190 in place by pressing the heatsink 190 down against the top surface 582 of the lid 580 (FIG. 5A), or the bottom surface 142 of the chip 140 (FIG. 6), or the top surface 782 of the lid 780 (FIG. 7).
With reference to FIGS. 1A and 5A, in one embodiment, the lids 180 and 580 comprise protruding members. More specifically, the lid 180 comprises protruding members 189a and 189b and the lid 580 comprises protruding members 589a and 589b. In one embodiment, the protruding members 189a and 189b comprise overhangs 187a and 187b, respectively, and the protruding members 589a and 589b comprise the overhangs 584a and 584b, respectively. Illustratively, the overhangs 187a and 187b comprise the holders 185a and 185b, respectively. It should be noted that the protruding members 189a and 189b apply forces using the holders 185a and 185b to the heatsink 190 resulting in the heatsink 190 being pressed towards the substrate 120. It should also be noted that the protruding members 589a and 589b apply forces via the springs 510a and 510b to the heatsink 190 resulting in the heatsink 190 being pressed towards the substrate 120.
While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.

## Claims

1. A structure, comprising:
substrate;
a semiconductor chip on top of and physically attached to the substrate;
a lid on top of the substrate,
wherein the lid comprises a first thermally conductive material; and

a heatsink on top of the lid,
wherein the heatsink comprises a second thermally conductive material,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member,
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction,
wherein the first protruding member comprises a first overhang, and
wherein the first overhang overlaps the heatsink in the reference direction such that there exists an imaginary straight line that is parallel to the reference direction and intersects both the first overhang and the heatsink.

2. The structure of claim 1,
wherein the first overhang comprises a first holder, and
wherein the first holder is in direct physical contact with the heatsink.

3. The structure of claim 2,
wherein the lid further comprises an opening,
wherein the semiconductor chip fits in the opening, and
wherein the lid is not disposed between the semiconductor chip and the heatsink.

4. The structure of claim 2, wherein the lid is physically attached to the substrate via a stiffener.

5. The structure of claim 2,
wherein the lid is physically attached to the substrate via an adhesive layer,
wherein a bottom member of the lid is oriented upward in the reference direction to create space for the semiconductor chip, and
wherein the semiconductor chip is sandwiched between the substrate and the bottom member of the lid.

6. A structure, comprising:
substrate;
a semiconductor chip on top of and physically attached to the substrate;
a lid on top of the substrate,
wherein the lid comprises a first thermally conductive material;

a heatsink on top of the lid,
wherein the heatsink comprises a second thermally conductive material,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member, and
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction; and

a first spring,
wherein the first spring is in direct physical contact with the first protruding member and the heatsink, and
wherein the first spring is farther away from the substrate than a portion of the heatsink in the reference direction.

7. The structure of claim 6,
wherein the lid further comprises an opening,
wherein the semiconductor chip fits in the opening, and
wherein the lid is not disposed between the semiconductor chip and the heatsink.

8. The structure of claim 6, wherein the lid is physically attached to the substrate via a stiffener.

9. The structure of claim 6,
wherein the lid is physically attached to the substrate via an adhesive layer,
wherein a bottom member of the lid is oriented upward in the reference direction to create space for the semiconductor chip, and
wherein the semiconductor chip is sandwiched between the substrate and the bottom member of the lid.

10. A structure formation method, comprising:
providing a structure which includes
(a) a substrate;
(b) a semiconductor chip on top of and physically attached to the substrate,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip; and

(c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and

placing a heatsink on top of the substrate,
wherein the heatsink comprises a second thermally conductive material,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member,
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction,
wherein the first protruding member comprises a first overhang, and
wherein the first overhang overlaps the heatsink in the reference direction such that there exists an imaginary straight line that is parallel to the reference direction and intersects both the first overhang and the heatsink.

11. The method of claim 10,
wherein the first overhang comprises a first holder, and
wherein the first holder is in direct physical contact with the heatsink.

12. A structure formation method, comprising:
providing a structure which includes
(a) a substrate;
(b) a semiconductor chip on top of and physically attached to the substrate,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip; and

(c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and

placing a heatsink on top of the substrate,
wherein the heatsink comprises a second thermally conductive material,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member,
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction,
wherein said placing the heatsink comprises placing a first spring between the first protruding member and the heatsink such that the first spring is in direct physical contact with the first protruding member and the heatsink, and
wherein the first spring is farther away from the substrate than a portion of the heatsink in the reference direction.

13. A structure formation method, comprising:
providing a structure which includes
(a) a substrate;
(b) a semiconductor chip on top of and physically attached to the substrate,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip; and

(c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and

placing a heatsink on top of the substrate,
wherein the heatsink comprises a second thermally conductive material,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member,
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction,
wherein the lid further comprises an opening,
wherein the semiconductor chip fits in the opening, and
wherein the lid is not disposed between the semiconductor chip and the heatsink.

14. A structure formation method, comprising:
providing a structure which includes
(a) a substrate;
(b) a semiconductor chip on top of and physically attached to the substrate,
wherein the semiconductor chip and the substrate share a common interface surface that defines a reference direction perpendicular to the common interface surface and pointing from the substrate towards the semiconductor chip; and

(c) a lid on top of the substrate, wherein the lid comprises a first thermally conductive material; and

placing a heatsink on top of the substrate,
wherein the heatsink comprises a second thermally conductive material,
wherein the lid is disposed between the substrate and the heatsink,
wherein the lid comprises a first protruding member,
wherein the first protruding member of the lid is farther away from the substrate than a portion of the heatsink in the reference direction, and
wherein the lid is physically attached to the substrate via a stiffener.