Attaching heat sinks to integrated circuits

[0002] This invention relates generally to heat sinks for integrated circuits.

[0003] Because of the heat generated by some integrated circuits, an integrated circuit may be intimately associated with a heat transfer device that removes heat from an integrated circuit die. An integrated circuit die may be packaged and the package may be coupled to a heat transfer device. Alternatively, the die may be exposed for direct contact by the heat transfer device. A heat transfer device, such as a heat sink, has a high heat transfer coefficient.

[0004] Processors may become excessively hot during operation. This heat may ultimately result in damage to the processor and may adversely affect the speed of its operation. Thus, it is desirable to contact the processor with a heat transfer device that removes heat.

[0005] Heat transfer devices may be active or passive. An active heat transfer device normally includes a fan which forces air over the integrated circuit to increase its rate of heat transfer. A passive heat transfer device is generally a heat sink with desirable heat transfer characteristics. Combinations of active and passive heat transfer devices are commonly utilized.

[0006] Attaching the heat transfer device over an integrated circuit on a circuit board can become a relatively complex operation. Generally, it is desirable to enable the removal of the integrated circuit device from the heat transfer device. This facilitates assembly and repair of the heat transfer device and testing of the integrated circuit.

[0007] In many cases, the heat transfer device is relatively bulky. It is generally desirable to contact the integrated circuit device with the heat transfer device. Commonly, an integrated circuit electrically couples to a variety of contacts on a circuit board, for example using pins that engage slots in a socket or other carrier. Thus, the integrated circuit may be attached to the circuit board and the heat transfer device may be attached over the integrated circuit in a removable, electrically contacting engagement. Therefore, the connection of the integrated circuit to the circuit board and the association of the heat transfer device with the integrated circuit may become complex.

[0008] For example, in connection with some designs, the attachment of the various components may require the use of tools. The use of tools generally results in longer assembly time. The assembler must assemble components and then grab a tool to secure the components together.

[0009] It would be desirable to enable the connection of the heat transfer device to the integrated circuit holder without requiring the use of any tools. Moreover, it would be desirable to have a way to readily and easily associate these components with one another.

[0010] FIG. 1 is a perspective view of one embodiment of the present invention showing the placement of the integrated circuit;

[0011] FIG. 2 is a perspective view of the embodiment of FIG. 1 after placement of the integrated circuit;

[0012] FIG. 3 is a perspective view of the embodiment shown in FIG. 1 after the heat transfer device has been pivoted over the integrated circuit;

[0013] FIG. 4 is a perspective view of the embodiment of FIG. 3 showing the process of securing a heat transfer device to the integrated circuit;

[0014] FIG. 5 is a partial, enlarged cross-sectional view taken generally along the line 5—5 of FIG. 2;

[0015] FIG. 6 is a partial, enlarged cross-sectional view corresponding to FIG. 5 but taken generally along the line 6—6 in FIG. 3;

[0016] FIG. 7 is a partial, enlarged cross-sectional view taken generally along the line 6—6 in FIG. 3;

[0017] FIG. 8 is a partial, enlarged cross-sectional view corresponding to FIG. 7 but taken along the line 8—8 in FIG. 4;

[0018] FIG. 9 is a partial enlarged cross-sectional view taken generally along the line 8—8 in FIG. 4 after rotation of the heat transfer device to secure the heat sink to the integrated circuit;

[0019] FIG. 10 is an exploded view of the heat transfer device in accordance with one embodiment of the present invention; and

[0020] FIG. 11 is a side elevational view of the heat sink shown in FIG. 10.

[0021] Referring to FIG. 1, an electronic device 10 may include an integrated circuit 22 secured within a holder 14 in turn secured to a circuit board 12. A heat transfer device 35 may be secured to the holder 14 for pivotal movement around one of the edges of the holder 14. The holder 14, in one embodiment of the present invention, includes four sides 15 that define a frame around the integrated circuit 22. Each corner of the holder 14 may be secured by a threaded fastener 16 to the circuit board 12. In one embodiment of the present invention, the device 10 is a motherboard and the integrated circuit 22 is a processor.

[0022] In one embodiment of the present invention, the integrated circuit 22 includes an organic layer grid array (OLGA) package. However, other packaging techniques may be utilized. In the illustrated package, the integrated circuit die 24 is exposed. The integrated circuit 22 may be secured to a socket 20 within the frame 14. The socket 20 may be secured directly to the circuit board 12 in one embodiment of the present invention. The socket 20 may include contacts (not shown) which mate with contacts (not shown) on the integrated circuit 22. In one embodiment of the present invention, the socket 20 may include pins that engage slots in the integrated circuit 22. However, any type of integrated circuit connection technique may be utilized.

[0023] The heat transfer device 35 may include a threaded heat sink member 38, a heat sink mount 30, an active heat transfer device 36, an electrical connector 32 to supply power to the device 36, and a heat sink 34. In some embodiments, the active heat transfer device 36, which may include a fan 44, may not be included. While the heat sink 34 is shown as a pin type heat sink, any other heat sink design may be utilized including, for example, those that include fins.

[0024] As shown in FIG. 2, the integrated circuit 22 may be placed on the socket 20 within the holder 14 with the die 24 facing upwardly. The heat transfer device 35 may rest in the overcenter position shown in FIG. 2. Interference between the holder 14 and the mount 30 may prevent further clockwise rotation from the position shown in FIG. 2.

[0025] Referring to FIG. 3, the heat transfer device 35 may pivot counterclockwise around the pivotal connection 37 so that the pivotally mounted heat sink mount 30 rests on top of the holder 14. The heat sink member 38 is then in direct contact with the die 24, in accordance with one embodiment of the present invention. However, other integrated circuits 22 may be utilized and it is not essential (although it may be advantageous) that the heat sink member 38 directly contact the die 24.

[0026] The pivotal connection 37 includes a slotted member 28, shown in FIG. 5, connected to, or integral with, the heat sink mount 30. An axle 46, associated with the holder 14, is journaled within an elliptical slot 47 inside the mount 30. Because the slot 47 is elongated, relative movement is possible between the member 28 and the axle 46. In other embodiments, the axle 46 may be included as part of the mount 30 and the member 28 may be a part of the holder 14. In any case, the arrangement of the axle 46, journaled within the member 28, allows pivotal motion of the heat transfer device 35 around the side 15bof the holder 14 (from the position shown in FIG. 2) until the device 35 contacts the holder 14 in face-to-face abutment, as shown in FIG. 3.

[0027] While a technique is described in which the mount 30, heat sink 34, and active heat transfer device 36 are pivoted as a unit, other techniques may also be used. For example, the mount 30 may be pivoted on its own, and other components may be thereafter secured to the mount 30.

[0028] The heat transfer device 35 assumes an “overbite” relationship with the holder 14, as shown in FIG. 3. Namely, a cantilevered latch 40 on one edge of the heat sink mount 30 extends over and beyond the side 43 of the holder 14 side 15a.

[0029] Referring to FIG. 7, the latch 40 is L-shaped and rests on a land 41 on a catch 42. The side 43 of the catch 42 is offset from the surface 49 of the catch 42, forming an effective land or stop 41. Because the latch 40 extends outwardly past the surface 43, the relationship between the heat transfer device 35 and the side 43 may be described as an overbite relationship. In addition, the engagement of the latch 40 horizontal portion 39 with the land 41 controls the extent of pivotal movement between the heat transfer device 35 and the holder 14. This further aligns the horizontal portion 39 with the catch 42 defined within the holder 14.

[0030] While an advantageous arrangement is shown in which the heat transfer device 35 pivots around a first side 15bof the holder 14 and latches on an opposed side 15aof the holder 14, other arrangements may be possible as well. For example, an intermediate latching mechanism may also be used.

[0031] Referring again to FIG. 3, the heat transfer device 35 may then be translated in the direction indicated by the arrow A relative to the holder 14. In the illustrated embodiment, the heat transfer device 35 is translated along a plane parallel to the circuit board 12. It is translated in a direction that causes the latch 40 to move towards the pivot axle 46 (FIG. 5) and the catch 42 (FIG. 7). As a result, the arrangement of the axle 46 relative to the member 28 changes from that shown in FIG. 5 to that shown in FIG. 6. That is, there is relative translating motion between the axle 46 within the slot 47 and the member 28.

[0032] At the same time, this translation causes the latch 40 and its horizontal portion 39 to fully engage the catch 42 and to abut against the rear surface 51 of the catch 42, as shown in FIG. 8. In this situation, the latch 40 may also abut against the surface 41 in one embodiment of the present invention. Thus, the latch 40 has now engaged the catch 42. However, the latch 40 is positioned at the bottom of the catch 42 relative to the heat transfer device 35.

[0033] Referring next to FIG. 4, the heat transfer device 35 may be rotated in the direction indicated by the arrows B in accordance with one embodiment of the present invention. This may be done by rotating the active heat transfer device 36 and/or the heat sink 34 relative to the heat sink mount 30. This rotation causes the heat sink member 38 to screw into the heat sink mount 30 and to extend further downwardly. The member 38 continues to thread downwardly, in response to the rotation indicated by the arrow B, until the heat sink member 38 comes into tight contact with the integrated circuit 22. Thus, the heat transfer device 35 may be threaded into the heat sink mount 30.

[0034] Upward motion of the heat transfer device 35 may be resisted by the engagement between the latch 40 and the catch 42. More particularly, as shown in FIG. 9, the latch 40 moves upwardly relative to the catch 42, in response to the rotation of heat transfer device 35, until the horizontal portion 39 engages the upper edge 53 of the catch 42 in the holder 14. In this position, the heat transfer device 35 is securely latched against motion relative to the holder 14. The force of the heat sink member 38 against the integrated circuit 22 and particularly the die 24 provides an upward force which secures the latch 40 to the holder 14 in one embodiment of the invention.

[0035] Referring to FIG. 10, the heat transfer device 35 includes the active heat transfer device 36, the heat sink 34 and the mount 30. In one embodiment of the present invention, the active heat transfer device 36 and the heat sink 34 may be secured by threaded fasteners which engage the interstices between the upstanding pins 60 of the heat sink 34.

[0036] The heat sink 34, shown in FIG. 11, includes a base plate 62 from which the pins 60 extend. In addition, the centrally located, downwardly depending threaded member 38 is connected to the plate 62. A wide variety of heat transfer devices may be used as the heat transfer device 35.

[0037] The member 38 threadedly engages a ring 64 centrally located within the mount 30. As a result, either or both of the active heat transfer device 36 and heat sink 34 may be rotated to cause the threaded member 38 to thread through the plate 30 and to engage the die 24.

[0038] The heat transfer device 35 may be easily and accurately secured onto the integrated circuit 22 without the use of tools in some embodiments. Through a simple pivot, translate and rotate motion, the necessary connections may be securely and advantageously made.

[0039] While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.