Integrated heat spreader with downset edge, and method of making same
A downset edge integrated heat spreader is disclosed. The downset edge can be formed to an industrially accepted flatness with a single stamping operation. The downset edge can provide a surface for fastening the downset edge integrated heat spreader to a mounting substrate. The downset edge can also provide a component recess for mounting a component near a processor, but on the mounting substrate. The downset edge can also provide a warp and bend resistant structure during ordinary field use.
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This application is a divisional of U.S. patent application Ser. No. 10/405,055, filed on Mar. 31, 2003, which is incorporated herein by reference.
TECHNICAL FIELDDisclosed embodiments relate to an integrated heat spreader with a downset edge. More particularly, disclosed embodiments relate to an integrated heat spreader with a minimum deviation from planarity. Disclosed embodiments also include a process of forming the integrated heat spreader by a single-stamping process.
BACKGROUND INFORMATIONDescription of Related Art
An integrated circuit (IC) die is often fabricated into a microelectronic device such as a processor. The increasing power consumption of processors results in tighter thermal budgets for a thermal solution design when the processor is employed in the field. Accordingly, a thermal interface is often needed to allow the die to reject heat more efficiently.
Various techniques have been employed to transfer heat away from a die. These techniques include passive and active configurations. One passive configuration involves a conductive material in thermal contact with the backside of a packaged die. This conductive material is often a slug, a heat spreader, or an integrated heat spreader (IHS).
A heat spreader is employed to spread and dissipate the heat generated by a die, which minimizes concentrated high-heat locations within the die. A heat spreader is attached proximate the back side of a microelectronic die with a thermally conductive material, such as a thermal interface material (TIM). A TIM can include, for example, thermally conductive gels, thermal greases, or solders. Heat spreaders include materials such as aluminum, copper, copper alloy, or ceramic, among others.
With conventional technology, a packaged microelectronic device includes a die which is bonded from the back side to an integrated heat spreader (IHS). An IHS adhesive layer acts as a TIM to bond the die to the IHS. The conventional IHS includes a lip portion that is formed by a bending process which gives rise to less than complete filling into the corner of the bend. Additionally to form the lip portion of the HIS from a rectangular blank, several stamping processes are required to achieve a sufficiently flat upper and lower surfaces to achieve quality bonds with other structures such as heat sinks and dies, respectively. These stamping processes result in a relatively low yield range in the production of heat spreaders, due, at least in part, to the processes used for forming heat spreaders. Additionally, the stamping processes result in a significant variation in flatness of the top surface of the IHS, as well as the bottom surface. The variation in flatness can detrimentally affect adhesion to either side of the IHS.
The current IHS, typically manufactured from a high purity copper alloy, is difficult to form with existing stamping equipment limitations, especially with respect to maintaining high raw material yield metrics & fully-filled corner geometries that are achieved with the stamping process. In order to completely fill the corner locations of the IHS, typical industry raw material yields range as low as 35%, yet utilize multi-stage manufacturing with high-tonnage machinery.
BRIEF DESCRIPTION OF THE DRAWINGSIn order to understand the manner in which embodiments are obtained, a more particular description of various embodiments briefly described above will be rendered by reference to the appended drawings. Understanding that these drawings depict only typical embodiments that are not necessarily drawn to scale and are not therefore to be considered to be limiting of its scope, some embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The following description includes terms, such as upper, lower, first, second, etc. that are used for descriptive purposes only and are not to be construed as limiting. The embodiments of a device or article described herein can be manufactured, used, or shipped in a number of positions and orientations.
Reference will now be made to the drawings wherein like structures will be provided with like reference designations. In order to show the structures of embodiments most clearly, the drawings included herein are diagrammatic representations of inventive articles. Thus, the actual appearance of the fabricated structures, for example in a photomicrograph, may appear different while still incorporating the essential structures of embodiments. Moreover, the drawings show only the structures necessary to understand the embodiments. Additional structures known in the art have not been included to maintain the clarity of the drawings.
The downset edge IHS 112 includes a heat spreader body 122 and downset edges 124 and 126. The downset edges appear as feet 124, 126 portions of the downset edge IHS 112. Because the microelectronic package 100 is depicted in orthogonal cross section, the downset edges 124 and 126 are depicted as two separate downset edges. The downset edge walls 125, 127 of the downset edges 124 and 126, respectively, form a perimeter for the entire downset edge IHS 112. In one embodiment, the perimeter, delineated at the downset edge walls 125 and 127, concentrically surrounds the heat spreader body 122 as it also delineates the entire perimeter of the downset edge IHS 112. The downset edges 124 and 126 are downset from the heat spreader body bottom surface 128 by a foot height 130. The foot height 130 forms a container recess 132 between the one or more downset edges 124, 126 and the bottom surface 128 of the downset edge IHS 112. The dimension of the container recess 132 is approximately as deep as the thickness of the die 110, the IS adhesive layer 116, the electrical bump 118, and the bond pad 120, if present.
The die 110 includes an active surface 134 and a backside surface 136. The adhesive layer 116 forms a bond line thickness (BLT) 138 between the backside surface 136 of the die 110 and the bottom surface 128 of the downset edge IHS 112.
In a die-referenced process of assembling the microelectronic package 100, the BLT 138 must take into account any particulates in the adhesive layer 116. In one embodiment, the adhesive layer 116 includes a polymer. In one embodiment, the adhesive layer 116 includes a polymer with heat transfer particulates disposed therein. In one embodiment, the adhesive layer 116 includes a solder. In one embodiment, the adhesive layer 116 includes a solder with heat transfer particulates disposed therein. In one embodiment, the adhesive layer 116 includes a polymer-solder hybrid (PSH). In one embodiment, the adhesive layer 116 includes a PSH with heat transfer particulates disposed therein. In one embodiment the heat transfer particulates include graphite flakes and/or filaments. In one embodiment the heat transfer particulates include diamond solids. In one embodiment the heat transfer particulates include metals with a higher coefficient of thermal conductivity than the bulk of the adhesive layer 116.
In one embodiment, the downset edge IHS 112 is attached to the mounting substrate 114 by an attachment material 140, such as a polymer or the like or another conventional sealant. In one embodiment the attachment material 140 is applied to at least a portion of the downset edges 124 or 126. Attachment of the downset edge IHS 112 to the mounting substrate 114 may be by any number of methods, including but not limited to pressing, application of epoxy, soldering, or any suitable method known in the art. Additionally, mechanical attachment devices, such as a fastener 142 may be used to attach the downset edge IHS 112 to the mounting substrate. In one embodiment, the fastener 142 is a screw. In one embodiment, the fastener 142 is a nut and bolt assembly. In one embodiment, the fastener 142 is a staple. In one embodiment, the fastener 142 is a rivet. In one embodiment, the fastener 142 is a snap. In one embodiment, the fastener 142 is a press-fit taper pin. In one embodiment, the fastener 142 is a press pin. In one embodiment, the fastener is a clip (see
In one embodiment when the downset edge IHS 112 is attached to the mounting substrate 114, the downset edge walls 125, 127 form an intermittent lip around the die 110 (see
As will be discussed in this disclosure, a notch 148 appears in the downset edge IHS 112. In one embodiment, the notch 148 represents a displacement of the downset edges 124 and 126 away from the heat spreader body 122, due to a stamping process or other process as will be set forth in this disclosure. In one embodiment, the notch 148 represents slip-shear of the downset edges 124 and 126 away from the heat spreader body 122. By a slip-shear action, corner structures as illustrated in
In one embodiment, the top surface 144 of the downset edge IHS 112 is substantially planar. By “substantially planar” it is understood that a deviation from planarity is minimized. Planarity is defined as a measure of the difference between the highest and lowest vertical points found along the top surface 144, divided by the length 146 of the heat spreader body 122. In one embodiment, the deviation from planarity is in a range from about 0.1 percent to about 0.5 percent. In one embodiment the length 146 of the heat spreader body 122 is in a range from about 5 millimeter (mm) to about 75 mm. In one embodiment the length 146 of the heat spreader body 122 is in a range from about 10 mm to about 50 mm. In one embodiment the length 146 of the heat spreader body 122 is in a range from about 20 mm to about 40 mm. In one embodiment the length 146 of the heat spreader body 122 is about 27 mm. In one embodiment the length 146 of the heat spreader body 122 is about 38.5 mm. In one embodiment the length 146 of the heat spreader body 122 is about 45 mm.
The downset edge IHS 112 as shown in
There are pluralities of methods which may be used to form a downset edge IHS as claimed and described. These methods include, for example, stamping, machining, progressive manufacturing, laser cutting, injection molding, powder metal casting and others. One such method of forming a downset edge IHS includes starting with a mass of material, or slug, and cutting or machining it to a set of dimensions. Thereafter, one or more stamping processes are employed to form the downset edges 124 and 126. In one embodiment, the process includes a single stamping event. In one embodiment, the process includes a plurality of stamping events.
After cladding the downset edge IHS 212, a single stamping process is carried out to form the downset edges 224 and 226. The downset edge IHS 212 depicted in
Where the downset edge IHS 212 is clad, such as with at least one of the lower cladding layer 211 and the upper cladding layer 213, the cladding material is selected to provide adequate adhesion to the IHS material under ordinary test and field usages. In one embodiment, the cladding material includes nickel or a nickel alloy. In one embodiment, the cladding material includes gold or a gold alloy. In one embodiment, the cladding material includes silver or a silver alloy. Other materials for the IHS and the cladding material can be selected according to specific applications.
During ordinary usage of a die such as the die 110 depicted in
The downset edge IHS 414 includes a heat spreader body 422 and downset edges 424 and 426. The downset edges appear as feet 424, 426 portions of the downset edge IHS 412. Because the microelectronic package 400 is depicted in orthogonal cross section, the downset edges 424 and 426 are depicted as two separate downset edges. The downset edge walls 425, 427 of the downset edges 424 and 426, respectively, form a perimeter. In one embodiment, the perimeter, delineated at the downset edge walls 425 and 427, concentrically surrounds the heat spreader body 422 and it also delineates the entire perimeter of the downset edge IHS 412.
In this embodiment, a top surface 444 of the downset edge IHS 412 is set above a downset edge surface 450. Further in this embodiment, the downset edge surface 450 extends substantially to the edge 413 of the mounting substrate 414. Where the downset edge IHS 412 is substantially stiffer than the mounting substrate 414, the portion of the downset edge IHS 412 that includes the downset edges 424 and 426, provides substantial resistance to warping and bending of the microelectronic package 400 during ordinary field use. Further because most of the downset edges 424 and 426 are remote from the die 410 where heat is generated, thermal expansion is minimized at the downset edges 424 and 426. This minimization of thermal expansions of the downset edges 424 and 426 also results in less warping and bending of the mounting substrate 414.
In one embodiment, the fastener 442 is a screw. In one embodiment, the fastener 442 is a nut and bolt assembly. In one embodiment, the fastener 442 is a staple. In one embodiment, the fastener 442 is a rivet. In one embodiment, the fastener 442 is a snap. In one embodiment, the fastener 442 is a press-fit taper pin. In one embodiment, the fastener 442 is a press pin. In one embodiment, the fastener is a clip (see
The downset edge IHS 412 also exhibits two metrics regarding the exposed amount of horizontal upper 444 and lower 450 surfaces. As an aspect ratio, the length 446 of the heat spreader body 422, can be divided by the length 447 of the downset edge 424 or 426. In one embodiment, the aspect ratio is in a range from about 100:1 to about 0.2:1. This aspect ratio range can also encompass the embodiments depicted in
The downset edge IHS 414 includes a heat spreader body 422 and downset edges 424 and 426. The downset edges appear as feet 424, 426 portions of the downset edge IHS 411. Because the microelectronic package 400 is depicted in orthogonal cross section, the downset edges 424 and 426 are depicted as two separate downset edges. The downset edge walls 425, 427 of the downset edges 424 and 426, respectively, form a perimeter. In one embodiment, the perimeter, delineated at the downset edge walls 425 and 427, concentrically surrounds the heat spreader body 422 and it also delineates the entire perimeter of the downset edge IHS 412.
In one embodiment, the downset edge IHS 411 is attached to the mounting substrate 414 by an attachment material 441, such as a polymer or other sealant. In one embodiment the attachment material 441 is applied to at least a portion of the downset edges 424 or 426.
In one embodiment, the attachment material 441 fills a recess in the downset edges 424 and 426. In one embodiment, the attachment material 441 overflows onto the downset edge surface 450. In one embodiment the recess has substantially tapered sidewalls, which form a locking structure when filled with the attachment material. In one embodiment the recess has substantially vertical sidewalls (not pictured).
Attachment of the downset edge IHS 411 to the mounting substrate 414 may be by any number of methods, including but not limited to pressing, application of epoxy, soldering, or any suitable method known in the art.
Additionally, mechanical attachment devices, such as a fasteners 443 may be used to attach the downset edge IHS 411 to the mounting substrate. In one embodiment, the fastener 443 is a screw. In one embodiment, the fastener 443 is a nut and bolt assembly. In one embodiment, the fastener 443 is a staple. In one embodiment, the fastener 443 is a rivet. In one embodiment, the fastener 443 is a snap. In one embodiment, the fastener 443 is a press-fit taper pin. In one embodiment, the fastener 443 is a press pin. In one embodiment, the fastener is a clip (see
Referring again to
Other component recesses 560, 562, and 564 are depicted in arbitrary numbers and locations along the downset edge IHS 512. In one embodiment, at least one of the component recesses 560, 562, and 564 communicates through the downset edge 524. By the occurrence of at least one of the channel recess 528 and component recesses 560 and 562 the intermittent lip 525 is present in the downset edge IHS 512 because each breaks the perimeter of the downset edge wall 525. By the occurrence of the component recess 564, the mounting substrate 514 is exposed, but the downset edge wall 525 is continuous in the region of the component recess 564 and the perimeter of the downset edge wall 525 is not broken at this location. In one embodiment, the presence of a recess such as one of the recesses 528, 560, 562, and 564 allows for articles such as electronic components and/or leads to be mounted upon the mounting substrate 514. In one embodiment, a decoupling capacitor (not pictured) is disposed in a recess upon the mounting substrate 514. Other components known in the art can be disposed in a recess as described and claimed.
Corresponding to the respective recesses 560, 562, and 564, clips 561, 563, and 565 are depicted as being mounted upon the mounting substrate 514 at a sub-lower level, and simultaneously mounted upon the lower level 550 which is the downset edge 424, 426 (see
In one embodiment, a clip 659 is fixed into position during pick-and-place fabrication of the microelectronic package 600. In one embodiment, the clip 659 is fixed into position by a snap according to conventional technique. In one embodiment, a fastener is used such as the fasteners 542 depicted in
It can now be appreciated that, although only one part of the downset edge 623 is depicted as substantially asymmetrical with respect to the heat spreader body 622, more than one part of the downset edge 623 can be substantially asymmetrical. Further with respect to the channel and component recesses depicted in
At 710, a downset edge IHS is formed. At 712, the downset edge IHS is formed by single-stamping a metal blank according any of the various embodiments set forth in this disclosure. At 714, the downset edge IHS is formed by multiple-stamping a metal blank according any of the various embodiments set forth in this disclosure. At 716, the downset edge IHS is formed by casting a metal blank according any of the various embodiments set forth in this disclosure. At 718, the downset edge IHS is formed by injection molding a metal blank according any of the various embodiments set forth in this disclosure. At 720, the downset edge IHS is formed by any other conventional forming technique according any of the various embodiments set forth in this disclosure. It can be appreciated that cladding the metal blank can precede, follow, or coincide with formation of the downset edge IHS 710. At 711, one process embodiment is completed.
At 730, a die is placed upon a mounting substrate. At 731, one method embodiment is completed.
At 740, a downset edge IHS is placed over the die, and also upon the mounting substrate. At 741, one method embodiment is completed.
The several embodiments set forth in this disclosure are described primarily in the context of utilization with an integrated circuit flip-chip configuration, packaged with a substrate and heat spreader as shown in the accompanying figures. Other embodiments, however, can be employed that are not limited to just this particular configuration, and the claimed subject matter is applicable to other types of microelectronic packages. For example, microelectronic packages in accordance with the claimed subject matter may include packages with varying form factors, such as, for example, pin grid array, ball grid array, ball grid array with pinned interposers and wire bonding.
It is emphasized that the Abstract is provided to comply with 37 C.F.R. §1.72(b) requiring an Abstract that will allow the reader to quickly ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.
In the foregoing Detailed Description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate preferred embodiment.
It will be readily understood to those skilled in the art that various other changes in the details, material, and arrangements of the parts and method stages which have been described and illustrated in order to explain the nature of this invention may be made without departing from the principles and scope of the invention as expressed in the subjoined claims.
Claims
1-16. (canceled)
17. A process comprising:
- forming an integrated heat spreader, including a heat spreader body including a first surface; and
- forming a downset edge, including a downset edge wall and a downset edge surface which substantially surrounds the integrated heat spreader body, wherein the downset edge includes a second surface which is lower than the first surface.
18. The process according to claim 17, wherein forming the downset edge is selected from a single stamping event, a plurality of stamping events, casting, injection molding, and consolidating a metal powder.
19. The process according to claim 17, further including:
- forming a cladding upon the downset edge integrated heat spreader.
20. The process according to claim 17, further including:
- forming a cladding upon the downset edge integrated heat spreader, wherein forming a cladding proceeds from one of before, during, and after forming the downset edge.
21. A method comprising:
- assembling a downset edge integrated heat spreader with a microelectronic die.
22. The method according to claim 21, further including:
- assembling the downset edge integrated heat spreader with a mounting substrate.
23. The method according to claim 21, further including:
- assembling the downset edge integrated heat spreader with a mounting substrate; and
- affixing a fastener between the downset edge integrated heat spreader and the mounting substrate.
24-26. (canceled)
27. The process of claim 17, wherein forming includes stamping a notch by displacement of the downset edge away from the heat spreader body.
28. The process of claim 17, wherein forming includes stamping a notch by displacement of the downset edge away from the heat spreader body by slip-shear of the downset edge away from the heat spreader body.
29. The process of claim 17, wherein forming the downset edge is by molten casting.
30. The process of claim 17, wherein forming the downset edge is by injection molding.
31. The process of claim 17, wherein forming the downset edge is by dry casting a powdered metal composite.
32. The process of claim 17, wherein forming the downset edge is by dry casting a powdered metal composite including a process selected from pressing, sintering, and a combination thereof.
33. The process of claim 17, wherein forming includes stamping to form the downset edge surface downset from the heat spreader body bottom surface by a foot height, and wherein the foot height defines a container recess
34. The process of claim 17, wherein forming includes forming a downset region disposed between the heat spreader body and the downset edge, wherein the downset region includes an inner wall and an outer wall.
35. The process of claim 17, wherein forming includes:
- forming a downset region disposed between the heat spreader body and the downset edge, wherein the downset region includes an inner wall and an outer wall; and
- forming a channel in the downset edge wall which communicates between the inner wall and the outer wall.
36. The process of claim 17, wherein forming includes:
- machining a mass of material to a set of dimensions; followed by one or more stamping processes.
37. The process of claim 17, wherein forming includes forming at least one of a lower cladding layer and an upper cladding layer upon the integrated heat spreader body, selected from pressure cladding, electroplating, electroless plating, and combinations thereof.
38. The process of claim 17, wherein forming includes drawing an integrated heat spreader blank through a molten metal to form at least one of the lower cladding layer and an upper cladding layer upon the integrated heat spreader body.
39. The process of claim 17, wherein forming includes forming one part of the downset edge as substantially asymmetrical with respect to the integrated heat spreader body.
40. A process comprising:
- forming a copper integrated heat spreader, including a heat spreader body including a first surface; and
- forming a downset edge, including a downset edge wall and a downset edge surface which substantially surrounds the integrated heat spreader body, wherein the downset edge includes a second surface which is lower than the first surface.
41. The process of claim 40, wherein forming includes stamping a notch in the copper by displacement of the downset edge away from the heat spreader body by slip-shear of the downset edge away from the heat spreader body.
42. The process of claim 40, further including:
- forming a cladding upon the downset edge integrated heat spreader, wherein forming a cladding proceeds from one of before, during, and after forming the downset edge.
43. A process comprising:
- forming an integrated heat spreader, including a heat spreader body including a first surface, wherein forming includes stamping a notch in the copper by displacement of the downset edge away from the heat spreader body by slip-shear of the downset edge away from the heat spreader body; and
- forming a downset edge, including a downset edge wall and a downset edge surface which substantially surrounds the integrated heat spreader body, wherein the downset edge includes a second surface which is lower than the first surface, wherein forming includes forming one part of the downset edge as substantially asymmetrical with respect to the integrated heat spreader body.
44. The process of claim 43, further including:
- forming a cladding upon the downset edge integrated heat spreader, wherein forming a cladding proceeds from one of before, during, and after forming the downset edge.
45. The process of claim 43, wherein forming includes:
- machining a mass of material to a set of dimensions; followed by
- one or more of the stamping processes.
Type: Application
Filed: Apr 5, 2005
Publication Date: Sep 29, 2005
Applicant:
Inventors: Nick Labanok (Phoenix, AZ), Sabina Houle (Phoenix, AZ)
Application Number: 11/099,106