US20100319898A1

US20100319898A1 - Thermal interconnect and integrated interface systems, methods of production and uses thereof

Info

Publication number: US20100319898A1
Application number: US12/666,004
Authority: US
Inventors: Patrick K. Underwood; Arthur Falk; Paul Silinger
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2008-03-13
Filing date: 2009-03-05
Publication date: 2010-12-23
Also published as: WO2009114372A2; TW200949185A; WO2009114372A3

Abstract

Heat spreader assemblies are disclosed that include a heat spreader component, at least one coupling layer, and at least one thermally conductive layer, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer. In some instances, heat spreader assemblies include an aluminum-based heat spreader component, at least one coupling layer, wherein the coupling layer comprises zinc, a zinc-based material, tin, a tin-based material or a combination thereof, and at least one thermally conductive layer comprising nickel, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer. Methods of forming heat spreader assemblies are also disclosed that include providing a heat spreader component, wherein the heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material; providing at least one coupling material, wherein the coupling material is directly deposited onto the bottom surface of the heat spreader component; and depositing, applying or coating at least one thermally conductive coating, film or layer on at least part of the bottom surface of the heat spreader component. In several embodiments, heat spreader component comprises a native oxide layer, an oxide barrier layer or a combination thereof that is removed before application of the at least one coupling material.

Description

This application filed under the Patent Cooperation Treaty (PCT) claims priority to U.S. Provisional Application Ser. No. 61/036,397 filed on Mar. 13, 2008, which is commonly-owned and incorporated herein in its entirety by reference.

BACKGROUND

Electronic components are used in ever increasing numbers in consumer and commercial electronic products. Examples of some of these consumer and commercial products are televisions, personal computers, Internet servers, cell phones, pagers, palm-type organizers, portable radios, car stereos, or remote controls. As the demand for these consumer and commercial electronics increases, there is also a demand for those same products to become smaller, more functional, and more portable for consumers and businesses.
As a result of the size decrease in these products, the components that comprise the products must also become smaller. Examples of some of those components that need to be reduced in size or scaled down are printed circuit or wiring boards, resistors, wiring, keyboards, touch pads, and chip packaging. Products and components also need to be prepackaged, such that the product and/or component can perform several related or unrelated functions and tasks. Examples of some of these “total solution” components and products comprise layered materials, mother boards, cellular and wireless phones and telecommunications devices and other components and products, such as those found in US patent and PCT Application Ser. Nos. 60/396,294 filed Jul. 15, 2002, 60/294,433 filed May 30, 2001 and PCT/US02/17331 filed May 30, 2002, which are all commonly owned and incorporated herein in their entirety.
Components, therefore, are being broken down and investigated to determine if there are better building materials and methods that will allow them to be scaled down and/or combined to accommodate the demands for smaller electronic components. In layered components, one goal appears to be decreasing the number of the layers while at the same time increasing the functionality and durability of the remaining layers. This task can be difficult, however, given that several of the layers and components of the layers should generally be present in order to operate the device.
The packaging field is under a great deal of competing pressures. First, cost pressures force the industry to search for lower cost raw materials. Second, as electronic devices become smaller and operate at higher speeds, energy emitted in the form of heat increases dramatically. The technical requirements for heat dissipation are also increasing. With the advent of dual and quad core processors, IC manufacturers have decreased the need for higher thermal conductivity materials, but have not found a material with both low cost and intermediate thermal properties. In the past, anodized aluminum has been used, but the thermal resistance of the oxide barrier layer degrades the bulk thermal properties of the aluminum to the point where it cannot be used in today's packages.
Thus, there is a continuing need to: a) design and produce thermal interconnects and integrated interface materials, layered materials, components and products that meet customer specifications while minimizing the size of the device and number of layers; b) produce more efficient and better designed materials, products and/or components with respect to the compatibility requirements of the material, component or finished product; c) develop reliable methods of producing desired thermal interconnect materials, integrated interface materials and layered materials and components/products comprising contemplated integrated interface and layered materials; d) develop materials that possess a high thermal conductivity and a high mechanical compliance; and e) effectively reduce the number of production steps necessary for a package assembly, which in turn results in a lower cost of ownership over other conventional layered materials and processes.

SUMMARY OF THE SUBJECT MATTER

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a side view of a contemplated heat spreader assembly.

FIG. 2 shows a contemplated method of forming layered thermal interface materials, heat spreader assemblies and thermal transfer materials.

Table 1 shows thermal performance of a contemplated heat spreader assembly.

DETAILED DESCRIPTION

A suitable interface material or component should conform to the mating surfaces (“wets” the surface), possess a low bulk thermal resistance and possess a low contact resistance. Bulk thermal resistance can be expressed as a function of the material's or component's thickness, thermal conductivity and area. Contact resistance is a measure of how well a material or component is able to make contact with a mating surface, layer or substrate. The thermal resistance of an interface material or component can be shown as follows:
Θ interface=t/kA+2Θ_contact Equation 1

- where
  - Θ is the thermal resistance,
  - t is the material thickness,
  - k is the thermal conductivity of the material
  - A is the area of the interface

The term “t/kA” represents the thermal resistance of the bulk material and “2Θ_contact” represents the thermal contact resistance at the two surfaces. A suitable interface material or component should have a low bulk resistance and a low contact resistance, i.e. at the mating surface.
Many electronic and semiconductor applications require that the interface material or component accommodate deviations from surface flatness resulting from manufacturing and/or warpage of components because of coefficient of thermal expansion (CTE) mismatches.
A material with a low value for k, such as thermal grease, performs well if the interface is thin, i.e. the “t” value is low. If the interface thickness increases by as little as 0.002 inches, the thermal performance can drop dramatically. Also, for such applications, differences in CTE between the mating components causes the gap to expand and contract with each temperature or power cycle. This variation of the interface thickness can cause pumping of fluid interface materials (such as grease) away from the interface.
Interfaces with a larger area are more prone to deviations from surface planarity as manufactured. To optimize thermal performance, the interface material should be able to conform to non-planar surfaces and thereby lower contact resistance. As used herein, the term “interface” means a couple or bond that forms the common boundary between two parts of matter or space, such as between two molecules, two backbones, a backbone and a network, two networks, etc. An interface may comprise a physical attachment of two parts of matter or components or a physical attraction between two parts of matter or components, including bond forces such as covalent and ionic bonding, and non-bond forces such as Van der Waals, diffusion bonding, electrostatic, coulombic, hydrogen bonding and/or magnetic attraction. Contemplated interfaces include those interfaces that are formed with bond forces, such as covalent bonds; however, it should be understood that any suitable adhesive attraction or attachment between the two parts of matter or components is contemplated.
Optimal interface materials and/or components possess a high thermal conductivity and a high mechanical compliance. High thermal conductivity reduces the first term of Equation 1 while high mechanical compliance reduces the second term. The layered interface materials and the individual components of the layered interface materials described herein accomplish these goals. When properly produced, the thermal interface component described herein will span the distance between the mating surface of the heat spreader material and the silicon die component thereby allowing a continuous high conductivity path from one surface to the other surface.
In order to address the goals in the background section, while at the same time addressing the inherent difficulties in utilizing heat spreaders that form oxide layers or oxide barrier layers, it has been discovered that the oxide layer or layers formed can be removed and replaced with a higher thermal conductivity coating through the use of at least one coupling layer. In a specific embodiment, aluminum oxide layers formed on aluminum heat spreaders can be removed and replaced with a higher thermal conductivity coating through the use of at least one coupling layer. What makes this process particularly difficult when utilizing aluminum as the heat spreader material, as mentioned in the background section, is that aluminum almost instantly forms an oxide layer, which is thermally and electrically nonconductive. This layer must be removed in order to plate metals on the surface that have sufficient adhesion to the surface and in order to have a useful layered material.
The layered interface materials and the individual components of the layered interface materials described herein accomplish these goals. When properly produced, the heat spreader component described herein will span the distance between the mating surfaces of the thermal interface material and the heat spreader component, thereby allowing a continuous high conductivity path from one surface to the other surface.
In contemplated embodiments, a heat spreader assembly can be produced that comprises: a) a heat spreader component, b) at least one coupling layer, and c) at least one thermally conductive layer, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer. In some instances, heat spreader assemblies include an aluminum-based heat spreader component, at least one coupling layer, wherein the coupling layer comprises zinc, a zinc-based material, tin, a tin-based material or a combination thereof, and at least one thermally conductive layer comprising nickel, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer.
Contemplated heat spreader assemblies may comprise any suitable heat spreader material or component, especially those materials that develop oxide barrier layers or a native oxide layer. In some embodiments, a contemplated heat spreader material comprises aluminum or an aluminum-based material. The heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material.
Heat spreader components or heat spreading components (heat spreader and heat spreading are used herein interchangeably and have the same common meaning) generally comprise a metal, a metal-based base material, a high-conductivity non-metal or combinations thereof, such as nickel, aluminum, copper, copper-tungsten, CuSiC, diamond, silicon carbide, graphite, composite materials such as copper composites, carbon composites and diamond composites or AlSiC and/or other suitable high-conductivity materials that may not comprise metal. Any suitable metal or metal-based base material can be used herein as a heat spreader, as long as the metal or metal-based base material can dissipate some or all of the heat generated by the electronic component.
As used herein, the term “metal” means those elements that are in the d-block and f-block of the Periodic Chart of the Elements, along with those elements that have metal-like properties, such as silicon and germanium. As used herein, the phrase “d-block” means those elements that have electrons filling the 3d, 4d, 5d, and 6d orbitals surrounding the nucleus of the element. As used herein, the phrase “f-block” means those elements that have electrons filling the 4f and 5f orbitals surrounding the nucleus of the element, including the lanthanides and the actinides. Preferred metals include indium, silver, copper, aluminum, tin, bismuth, lead, gallium and alloys thereof, silver coated copper, and silver coated aluminum. The term “metal” also includes alloys, metal/metal composites, metal ceramic composites, metal polymer composites, as well as other metal composites. As used herein, the term “compound” means a substance with constant composition that can be broken down into elements by chemical processes. As used herein, the phrase “metal-based” refers to any coating, film, composition or compound that comprises at least one metal.
Heat spreader components can be laid down or formed in any suitable thickness, depending on the needs of the electronic component, the vendor and as long as the heat spreader component is able to sufficiently perform the task of dissipating some or all of the heat generated from the surrounding electronic component. Contemplated thicknesses comprise thicknesses in the range of about 0.25 mm to about 6 mm. In some embodiments, contemplated thicknesses of heat spreader components are within the range of about 0.5 mm to about 5 mm. In other embodiments, contemplated thicknesses of heat spreader components are within the range of about 1 mm to about 4 mm.
When using a metallic thermal interface material, like solder, which has a high elastic modulus compared to most polymer systems, it may be necessary to reduce coefficient of thermal expansion mismatch generated mechanical stresses transferred to the semiconductor die in order to prevent cracking of the die. This stress transfer can be minimized by increasing the bondline of the metallic thermal interface material, reducing the coefficient of thermal expansion of the heat spreader, or change the geometry of the heat spreader to minimize stress transfer. Examples of lower coefficient of thermal expansion (CTE) materials are AlSiC, CuSiC, copper-graphite composites, carbon-carbon composites, diamond, CuMoCu laminates, etc. Examples of geometric changes are adding a partial or through slot to the spreader to decrease spreader thickness and forming a truncated, square based, inverted pyramid shape to lower stress and stiffness by having the spreader cross-section be lower near the semiconductor die.
In contemplated heat spreader assemblies, at least one thermally conductive layer is laid down on the heat spreader once at least one coupling layer has been applied to the heat spreader. The at least one coupling layer is applied after any oxide barrier layer or native oxide layer has been removed. These coupling layers are designed to increase the strength of the interface bond between the heat spreader and the at least one thermally conductive layer, while at the same time minimizing or negating any additional oxide layer development on the spreader. In some embodiments, the at least one coupling layer comprises zinc, zinc-based materials and/or alloys, tin, tin-based materials and/or alloys or combinations thereof. In contemplated embodiments, the at least one coupling layer may be applied by any suitable process, including direct plating, high speed plating or another method. The at least one coupling layer may also be laid down in any suitable solid layer or pattern and also any suitable thickness.
As mentioned, the at least one heat spreader component may be coupled with a metal-based coating, layer and/or film. As used herein, the term “coupled” means that the surface and coating, layer and/or film are physically attached to one another or there's a physical attraction between two parts of matter or components, including bond forces such as covalent and ionic bonding, and non-bond forces such as Van der Waals, diffusion bonding, electrostatic, coulombic, hydrogen bonding and/or magnetic attraction. Also, as used herein, the term coupled is meant to encompass a situation where the heat spreader component and the at least one thermally conductive layer, coating and/or film are directly attached to one another, but the term is also meant to encompass the situation where the heat spreader component and the at least one thermally conductive layer, coating and/or film are coupled to one another indirectly—such as the case where there's an adhesion promoter layer between the heat spreader component and the at least one thermally conductive layer, coating and/or film or where there's another layer altogether between the heat spreader component and the at least one thermally conductive layer, coating and/or film.
Once the at least one coupling layer is applied, the at least one thermally conductive layer may be applied. The at least one thermally conductive layer may be directly deposited onto at least part of at least one of the surfaces of the heat spreader component with the use of at least one coupling material or layer that is laid down onto the heat spreader component before the at least one thermally conductive layer or coating is applied. Again, this layer or layers may be applied by any suitable method or device. The at least one thermally conductive layer may comprise nickel, gold, indium, palladium, silver, tin, bismuth, ruthenium or a combination thereof.
The at least one thermally conductive coating, layer and/or film is deposited or applied to at least one of the surfaces of the heat spreader component. The at least one thermally conductive coating, layer and/or film may also be coated onto at least one of the surfaces of the heat spreader component. The terms coating, applied and deposited are used to show that the at least one thermally conductive coating, film and/or layer can be coated as a liquid or melt, can be applied as a strip, layer or film or can be deposited by vapor deposition, plating or electroplating and any other suitable deposition method.
These at least one thermally conductive coating layers are generally laid down by any method capable of producing a uniform layer with a minimum of pores or voids and can further lay down the layer with a relatively high deposition rate. Many suitable methods and apparatus are available to lay down layers or ultra thin layers of this type. One contemplated method is spot plating, pulse plating, reverse pulse plating or a combination thereof, which are described in U.S. Pat. No. 7,378,730, U.S. application Ser. No. 11/961,067 and PCT Application No. PCT/US04/04272, which are commonly-owned and incorporated herein by reference in their entirety. Pulse plating (which is intermittent plating as opposed to direct current plating) can lay down layers that are free or virtually free of pores and/or voids.
Another method of laying down thin layers or ultra thin layers is the pulse periodic reverse method or “PPR”. The pulse periodic reverse method goes one step beyond the pulse plating method by actually “reversing” or depleting the film at the cathode surface. A typical cycle for pulse periodic reverse might be 10 ms at 5 amps cathodic followed by 0.5 ms at 10 amps anodic followed by a 2 ms off time. There are several advantages of PPR. First, by “stripping” or deplating a small amount of film during each cycle, PPR forces new nucleation sites for each successive cycle resulting in further reductions in porosity. Second, cycles can be tailored to provide very uniform films by selectively stripping the thick film areas during the “deplating” or anodic portion of the cycle. PPR does not work well for some metal deposition, such as gold deposition, because gold plating is normally done in systems with no free cyanide. Hence gold will plate from a cyanide complex (chelate) during the plate cycle but cannot “strip” during the deplate cycle as there is no cyanide to allow the gold to re-dissolve.
The at least one thermally conductive coating, layer and/or film for use in the subject matter described herein should be able to be laid down in a thin or ultra thin continuous layer or pattern. The pattern may be produced by the use of a mask or the pattern may be produced by a device capable of laying down a desired pattern. Contemplated patterns include any arrangement of points or dots, whether isolated or combined to form lines, filled-in spaces and so forth. Thus, contemplated patterns include straight and curved lines, intersections of lines, lines with widened or narrowed areas, ribbons, overlapping lines. Contemplated thin layers and ultra thin coating layers may range from less than about 1 μm down to about one Angstrom or even down to the size of a single atomic layer of material. Specifically, some contemplated thin layers are less than about 1 μm thick. In other embodiments, contemplated thin layers are less than about 500 nm thick. In some embodiments, contemplated ultra thin layers are less than about 100 nm thick. In yet other embodiments, contemplated ultra thin layers are less than about 10 nm thick.
In some specific embodiments, nickel can be plated on an aluminum heat spreader, stiffener and/or integrated heat spreader with the aid of at least one coupling material, such as zinc, to meet the thermal needs of mid-range CPUs.
In other embodiments, the thermal transfer materials may also comprise protective layers or protective coatings. In contemplated embodiments, the protective layer is designed to transfer a smooth surface to the at least one thermally conductive layer or coating. Contemplated protective layers comprise stiff plastic, such as PVC or polyethylene.
In some embodiments, a plating process has been devised and is disclosed herein that assists in producing contemplated heat spreader assemblies and layered materials. Contemplated plating processes can fit on conventional equipment that is then set for high speed plating of at least one thermally conductive layer on a heat spreader material or component, such as nickel on aluminum. This process will provide, in some embodiments, a nickel-plated surface that can be additionally treated after plating. For example, the plated surface can be LASER marked and/or treated much like the conventional nickel-plated surface on copper surfaces.
In one embodiment, a piece of aluminum is formed into any standard or non-standard shape for a heat spreader. A soap or cleaning bath is used to remove any forming or punching oils on the surface of the aluminum. An etching process then removes the native oxide layer of the aluminum substrate, and then a thin layer of zinc, tin, copper or combinations and alloys thereof is deposited onto the substrate. Once the zinc, tin, copper or combinations and alloys thereof layer is in place, a at least one thermally conductive coating, such as nickel, gold, indium, palladium, silver, tin, bismuth, ruthenium or a combination or alloy thereof can be plated and/or applied onto the surface.
In contemplated embodiments, a thermal interface material may be directly deposited onto at least one of the sides of the heat spreader component, such as the bottom side, the top side or both, after the at least one coupling layer and at least one thermally conductive layer is applied. In some contemplated embodiments, a solder material may be silk screened or dispensed directly onto the heat spreader by methods such as jetting, thermal spray, liquid molding or powder spray. In yet other contemplated embodiments, a film of thermal interface material is deposited and combined with other methods of building adequate thermal interface material thickness, including direct attachment of a preform or silk screening of a thermal interface material paste.
FIG. 1 shows a side view of a contemplated heat spreader assembly 100 comprising a heat sink 110, a first thermal interface material 120, a second thermal interface material 140, wherein the first and second thermal interface materials sandwich a contemplated heat spreader assembly 130. The heat spreader assembly 130 is blown up in this figure, where it includes a heat spreader component 132, at least one coupling layer 134 and at least one thermally conductive layer 136, wherein the heat spreader is coupled to the at least one thermally conductive layer through the at least one coupling layer. A die heater 150 is also included in this embodiment. In one embodiment, the thermal interface materials may comprise one of the “PCM” materials manufactured by Honeywell International Inc., which include PCM45, PCM45F, along with others. The thickness of the first thermal interface material may be from about 2.5 to 3 mil. The thickness of the second thermal interface material may be suitable for the assembly, including what is referred to as “no-shim”.
The thermal performance of this type of contemplated heat spreader assembly is shown in Table 1. Sample to sample variations are caused by the first thermal interface material thickness differences. An estimated aluminum spreader Theta_d-s with a 2.68 mil first thermal interface material should be approximately 0.52° C./W, then the aluminum spreaders' thermal performance should be at least 30% lower than the copper ones.
Methods of forming layered thermal interface materials, heat spreader assemblies and thermal transfer materials 200 are shown in FIG. 2 and include: a) providing a heat spreader component, wherein the heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material 210; b) providing at least one coupling material, wherein the coupling material is directly deposited onto the bottom surface of the heat spreader component 220; c) depositing, applying or coating at least one thermally conductive coating, film or layer on at least part of the bottom surface of the heat spreader component 230; and d) depositing, applying or coating the at least one thermal interface material or another material onto at least part of at least one of the surfaces of the heat spreader component or assembly 240. Contemplated methods also comprise cleaning the heat spreader component prior to depositing the at least one coupling material 250. In addition, some embodiments comprise removing the native oxide layer or material, the oxide barrier layer or material or the combination thereof by an etching process 260. In other embodiments, contemplated methods further comprise depositing, applying or coating the at least one thermal interface material or another material or component onto at least part of at least one of the surfaces of the heat spreader component or onto at least part of at least one of the surfaces of the heat spreader assembly 270.
Once deposited, applied or coated, the thermal interface material layer comprises a portion that is directly coupled to the thermally conductive coating or layer and a portion that is exposed to the atmosphere, or covered by a protective layer or film that can be removed just prior to installation of the heat spreader component. Additional methods include providing at least one adhesive component and coupling the at least one adhesive component to at least part of at least one of the surfaces of the at least one heat spreader material and/or to or in at least part of the thermal interface material. At least one additional layer, including a substrate layer, can be coupled to the layered interface material.
As described herein, optimal interface materials and/or components possess a high thermal conductivity and a high mechanical compliance, e.g. will yield elastically when force is applied. High thermal conductivity reduces the first term of Equation 1 while high mechanical compliance reduces the second term. The layered interface materials and the individual components of the layered interface materials described herein accomplish these goals. When properly produced, the heat spreader component described herein will span the distance between the mating surfaces of the thermal interface material and the heat spreader component thereby allowing a continuous high conductivity path from one surface to the other surface. Suitable thermal interface components comprise those materials that can conform to the mating surfaces (“wets” the surface), possess a low bulk thermal resistance and possess a low contact resistance.
A suitable interface material can also be produced/prepared that comprises a solder material. The solder material may comprise any suitable solder material or metal, such as indium, silver, copper, aluminum, tin, bismuth, lead, gallium and alloys thereof, silver coated copper, and silver coated aluminum, but it is preferred that the solder material comprise indium or indium-based alloys. Suitable interface materials may comprise a conductive filler, a metallic material, a solder alloy and combinations thereof.
The solder-based interface materials, as described herein, have several advantages directly related to use and component engineering, such as: a) high bulk thermal conductivity, b) metallic bonds may be formed at the joining surfaces, lower contact resistance c) the interface solder material can be easily incorporated into micro components, components used for satellites, and small electronic components.
An additional component, such as a low modulus metal coated polymer sphere or microspheres may be added to the solder material to decrease the bulk elastic modulus of the solder. An additional component may also be added to the solder to promote wetting to the die and/or heat spreader surface. These additions are contemplated to be silicide formers, or elements that have a higher affinity for oxygen or nitrogen than does silicon. The additions can be one element that satisfies all requirements, or multiple elements each of which has one advantage. Additionally, alloying elements may be added which increase the solubility of the dopant elements in the indium or solder matrix.
Thermal filler particles may be dispersed in the thermal interface component or mixture should advantageously have a high thermal conductivity. Suitable filler materials include metals, such as silver, copper, aluminum, and alloys thereof; and other compounds, such as boron nitride, aluminum nitride, silver coated copper, silver-coated aluminum, conductive polymers and carbon fibers. Combinations of boron nitride and silver or boron nitride and silver/copper also provide enhanced thermal conductivity. Boron nitride in amounts of at least 20 wt % and silver in amounts of at least about 60 wt % are particularly useful. Preferably, fillers with a thermal conductivity of greater than about 20 and most preferably at least about 40 W/m° C. can be used. Optimally, it is desired to have a filler of not less than about 80 W/m° C. thermal conductivity.
Another contemplated and suitable thermal interface material can be produced/prepared that comprises a resin mixture and at least one solder material. The resin material may comprise any suitable resin material, but it is preferred that the resin material be silicone-based comprising one or more compounds such as vinyl silicone, vinyl Q resin, hydride functional siloxane and platinum-vinylsiloxane. The solder material may comprise any suitable solder material or metal, such as indium, silver, copper, aluminum, tin, bismuth, lead, gallium and alloys thereof, silver coated copper, and silver coated aluminum, but it is preferred that the solder material comprise indium or indium-based alloys.
The solder-based interface materials, such a polymer solder materials, polymer solder hybrid materials and other solder-based interface materials, as described herein, have several advantages directly related to use and component engineering, such as: a) the interface material/polymer solder material can be used to fill small gaps on the order of 2 millimeters or smaller, b) the interface material/polymer solder material can efficiently dissipate heat in those very small gaps as well as larger gaps, unlike most conventional solder materials, and c) the interface material/polymer solder material can be easily incorporated into micro components, components used for satellites, and small electronic components.
Resin-containing interface materials and solder materials, especially those comprising silicone resins, that may also have appropriate thermal fillers can exhibit a thermal capability of less than 0.5° C.-cm²/W. Unlike thermal grease, thermal performance of the material will not degrade after thermal cycling or flow cycling in IC devices because liquid silicone resins will cross link to form a soft gel upon heat activation.
Solder materials that are dispersed in the resin mixture are contemplated to be any suitable solder material for the desired application. Preferred solder materials are indium tin (InSn) alloys, indium silver (InAg) alloys, indium-bismuth (InBi) alloys, indium-based alloys, tin silver copper alloys (SnAgCu), tin bismuth and alloys (SnBi), and aluminum-based compounds and alloys. Especially preferred solder materials are those materials that comprise indium. The solder may or may not be doped with additional elements to promote wetting to the heat spreader or die backside surfaces.
As with the previously described thermal interface materials and components, thermal filler particles may be dispersed in the resin mixture. If thermal filler particles are present in the resin mixture, then those filler particles should advantageously have a high thermal conductivity. Suitable filler materials include silver, copper, aluminum, and alloys thereof; boron nitride, aluminum spheres, aluminum nitride, silver coated copper, silver coated aluminum, carbon fibers, and carbon fibers coated with metals, metal alloys, conductive polymers or other composite materials. Combinations of boron nitride and silver or boron nitride and silver/copper also provide enhanced thermal conductivity. Boron nitride in amounts of at least 20 wt. %, aluminum spheres in amounts of at least 70 wt. %, and silver in amounts of at least about 60 wt. % are particularly useful. These materials may also comprise metal flakes or sintered metal flakes.
Vapor grown carbon fibers, as previously described, and other fillers, such as substantially spherical filler particles may be incorporated. Additionally, substantially spherical shapes or the like will also provide some control of the thickness during compaction. Dispersion of filler particles can be facilitated by the addition of functional organo metallic coupling agents or wetting agents, such as organosilane, organotitanate, organozirconium, etc. The organo metallic coupling agents, especially organotitanate, may also be used to facilitate melting of the solder material during the application process.
These compounds may comprise at least some of the following: at least one silicone compound in 1 to 20 weight percent, organotitanate in 0-10 weight percent, at least one solder material in 5 to 95 weight percent. These compounds may include one or more of the optional additions, e.g., wetability enhancer. The amounts of such additions may vary but, generally, they may be usefully present in the following approximate amounts (in wt. %): filler up to 95% of total (filler plus resins); wetability enhancer 0.1 to 5% (of total); and adhesion promoters 0.01 to 1% (of total). It should be noted the addition at least about 0.5% carbon fiber significantly increases thermal conductivity. These compositions are described in U.S. Pat. No. 6,706,219, U.S. application Ser. No. 10/775,989 filed on Feb. 9, 2004 and PCT Serial No. PCT/US02/14613, which are all commonly owned and incorporated herein in their entirety by reference.
Contemplated solder compositions are as follows: InSn=52% In (by weight) and 48% Sn (by weight) with a melting point of 118° C.; InAg=97% In (by weight) and 3% Ag (by weight) with a melting point of 143° C.; In =100% indium (by weight) with a melting point of 157° C.; SnAgCu=94.5% tin (by weight), 3.5% silver (by weight) and 2% copper (by weight) with a melting point of 217° C.; SnBi=60% Tin (by weight) and 40% bismuth (by weight) with a melting point of 170° C. It should be appreciated that other compositions comprising different component percentages can be derived from the subject matter contained herein.
Phase-change materials that are contemplated herein comprise waxes, polymer waxes or mixtures thereof, such as paraffin wax. Paraffin waxes are a mixture of solid hydrocarbons having the general formula C_nH_2n+2and having melting points in the range of about 20° C. to 100° C. Examples of some contemplated melting points are about 45° C. and 60° C. Thermal interface components that have melting points in this range are PCM45 and PCM60HD —both manufactured by Honeywell International Inc. Polymer waxes are typically polyethylene waxes, polypropylene waxes, and have a range of melting points from about 40° C. to 160° C.
PCM45 comprises a thermal conductivity of about 3.0 W/mK, a thermal resistance of about 0.25° C.-cm²/W, is typically applied at a thickness of about 0.0015 inches (0.04 mm) and comprises a soft material, flowing easily under an applied pressure of about 5 to 30 psi. Typical characteristics of PCM45 are a) a super high packaging density—over 80%, b) a conductive filler, c) extremely low thermal resistance, and as mentioned earlier d) about a 45° C. phase change temperature. PCM60HD comprises a thermal conductivity of about 5.0 W/mK, a thermal resistance of about 0.17° C.-cm²/W, is typically applied at a thickness of about 0.0015 inches (0.04 mm) and comprises a soft material, flowing easily under an applied pressure of about 5 to 30 psi. Typical characteristics of PCM60HD are a) a super high packaging density—over 80%, b) a conductive filler, c) extremely low thermal resistance, and as mentioned earlier d) about a 60° C. phase change temperature. TM350 (a thermal interface component not comprising a phase change material and manufactured by Honeywell International Inc.) comprises a thermal conductivity of about 3.0 W/mK, a thermal resistance of about 0.25° C.-cm²/W, is typically applied at a thickness of about 0.0015 inches (0.04 mm) and comprises a paste that can be thermally cured to a soft gel. Typical characteristics of TM350 are a) a super high packaging density—over 80%, b) a conductive filler, c) extremely low thermal resistance, d) about a 125° C. curing temperature, and e) dispensable non-silicone-based thermal gel. PCM45F comprises a thermal conductivity of about 2.35 W/mK, a thermal resistance of about 0.20° C.-cm²/W, is typically applied at a thickness of about 0.002 mm and comprises a soft material, flowing easily under an applied pressure of about 5 to 40 psi. Typical characteristics of PCM45F are a) a super high packaging density—over 80%, b) a conductive filler, c) extremely low thermal resistance, and as mentioned earlier d) about a 45° C. phase change temperature.
Phase change materials are useful in thermal interface component applications because they are solid at room temperature and can easily be pre-applied to thermal management components. At operation temperatures above the phase change temperature, the material is liquid and behaves like a thermal grease. The phase change temperature is the melting temperature at which the heat absorption and rejection takes place.
Paraffin-based phase change materials, however, have several drawbacks. On their own, they can be very fragile and difficult to handle. They also tend to squeeze out of a gap from the device in which they are applied during thermal cycling, very much like grease. The rubber-resin modified paraffin polymer wax system described herein avoids these problems and provides significantly improved ease of handling, is capable of being produced in flexible tape or solid layer form, and does not pump out or exude under pressure. Although the rubber-resin-wax mixtures may have the same or nearly the same temperature, their melt viscosity is much higher and they do not migrate easily. Moreover, the rubber-wax-resin mixture can be designed to be self-crosslinking, which ensures elimination of the pump-out problem in certain applications. Examples of contemplated phase change materials are malenized paraffin wax, polyethylene-maleic anhydride wax, and polypropylene-maleic anhydride wax. The rubber-resin-wax mixtures will functionally form at a temperature between about 50 to 150° C. to form a crosslinked rubber-resin network.
The contemplated thermal interface component can be provided as a dispensable liquid paste to be applied by dispensing methods (such as screen printing or stenciling) and then cured as desired. It can also be provided as a highly compliant, cured, elastomer film or sheet for pre-application on interface surfaces, such as heat sinks. It can further be provided and produced as a soft gel or liquid that can be applied to surfaces by any suitable dispensing method, such as screen-printing or ink jet printing. Even further, the thermal interface component can be provided as a tape that can be applied directly to interface surfaces or electronic components.
Pre-attached/pre-assembled thermal solutions and/or IC (interconnect) packages comprise one or more components of the thermal interface materials described herein and at least one adhesive component. These thermal interface materials exhibit low thermal resistance for a wide variety of interface conditions and demands. As used herein, the term “adhesive component” means any substance, inorganic or organic, natural or synthetic, that is capable of bonding other substances together by surface attachment. In some embodiments, the adhesive component may be added to or mixed with the thermal interface material, may actually be the thermal interface material or may be coupled, but not mixed, with the thermal interface material. Examples of some contemplated adhesive components comprise double-sided tape from SONY, such as SONY T4411, 3M F9460PC or SONY T4100D203. In other embodiments, the adhesive may serve the additional function of attaching the heat spreading component to the package substrate independent of the thermal interface material.
The thermal interface components, the crosslinkable thermal interface components and the heat spreader components can be individually prepared and provided by using the methods previously described herein. The two components are then physically coupled to produce a layered interface material. As used herein, the term “interface” means a couple or bond that forms the common boundary between two parts of matter or space. An interface may comprise a physical attachment or physical couple of two parts of matter or components or a physical attraction between two parts of matter or components, including bond forces such as covalent and ionic bonding, and non-bond forces such as Van der Waals, electrostatic, coulombic, hydrogen bonding and/or magnetic attraction. The two components, as described herein, may also be physically coupled by the act of applying one component to the surface of the other component.
The layered interface material may then be applied to a substrate, another surface, or another layered material. The electronic component comprises a layered interface material, a substrate layer and an additional layer. The layered interface material comprises a heat spreader component and a thermal interface component. Substrates contemplated herein may comprise any desirable substantially solid material. Particularly desirable substrate layers would comprise films, glass, ceramic, plastic, metal or coated metal, or composite material. In preferred embodiments, the substrate comprises a silicon or germanium arsenide die or wafer surface, a packaging surface such as found in a copper, silver, nickel or gold plated leadframe, a copper surface such as found in a circuit board or package interconnect trace, a via-wall or stiffener interface (“copper” includes considerations of bare copper and it's oxides), a polymer-based packaging or board interface such as found in a polyimide-based flex package, lead or other metal alloy solder ball surface, glass and polymers such as polymimide. The “substrate” may even be defined as another polymer material when considering cohesive interfaces. In more preferred embodiments, the substrate comprises a material common in the packaging and circuit board industries such as silicon, copper, glass, and another polymer.
Additional layers of material may be coupled to the layered interface materials in order to continue building a layered component or printed circuit board. It is contemplated that the additional layers will comprise materials similar to those already described herein, including metals, metal alloys, composite materials, polymers, monomers, organic compounds, inorganic compounds, organometallic compounds, resins, adhesives and optical wave-guide materials.
Several methods and many thermal interface materials can be utilized to form these pre-attached/pre-assembled thermal solution components. A method for forming the thermal solution/package and/or IC package includes: a) providing the thermal transfer material described herein; b) providing at least one adhesive component; c) providing at least one surface or substrate; d) coupling the at least one thermal transfer material and/or material with the at least one adhesive component to form an adhesive unit; e) coupling the adhesive unit to the at least one surface or substrate to form a thermal package; f) optionally coupling an additional layer or component to the thermal package.
Applications of the contemplated thermal solutions, IC Packages, thermal interface components, layered interface materials and heat spreader components described herein comprise incorporating the materials and/or components into another layered material, an electronic component or a finished electronic product. Electronic components, as contemplated herein, are generally thought to comprise any layered component that can be utilized in an electronic-based product. Contemplated electronic components comprise circuit boards, chip packaging, separator sheets, dielectric components of circuit boards, printed-wiring boards, and other components of circuit boards, such as capacitors, inductors, and resistors.
Thus, specific embodiments and applications of heat spreader assemblies, components and related materials, including their methods of production, have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the disclosure. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

Claims

1. A heat spreader assembly, comprising:

a heat spreader component,

at least one coupling layer, and

at least one thermally conductive layer, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer.

2. The heat spreader assembly of claim 1, wherein the heat spreader component comprises an oxide-producing material.

3. The heat spreader assembly of claim 2, wherein the oxide-producing material comprises aluminum.

4. The heat spreader assembly of claim 1, wherein the heat spreader component comprised an oxide layer, an oxide barrier layer or a combination thereof.

5. The heat spreader assembly of claim 1, wherein the at least one coupling layer comprises zinc, zinc-based materials, tin, tin-based materials or combinations thereof.

6. The heat spreader assembly of claim 5, wherein the at least one coupling layer comprises zinc or a zinc-based material.

7. The heat spreader assembly of claim 5, wherein the at least one coupling layer comprises tin or a tin-based material.

8. The heat spreader assembly of claim 1, wherein the at least one thermally conductive layer comprises nickel, gold, indium, palladium, silver, tin, bismuth, ruthenium or a combination thereof.

9. The heat spreader assembly of claim 8, wherein the at least one thermally conductive layer comprises nickel.

10. The heat spreader assembly of claim 1, further comprising at least one additional layer.

11. The heat spreader assembly of claim 10, wherein the at least one additional layer comprises at least one thermal interface material.

12. A method of forming a heat spreader assembly, comprising:

providing a heat spreader component, wherein the heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material;

providing at least one coupling material, wherein the coupling material is directly deposited onto the bottom surface of the heat spreader component; and

depositing, applying or coating at least one thermally conductive coating, film or layer on at least part of the bottom surface of the heat spreader component.

13. The method of claim 12, further comprising cleaning the heat spreader component prior to depositing the at least one coupling material.

14. The method of claim 12, wherein the heat spreader component comprises a native oxide layer, an oxide barrier layer or a combination thereof.

15. The method of claim 14, further comprising removing the native oxide layer, the oxide barrier layer or the combination thereof by an etching process.

16. The method of claim 12, wherein the at least one thermally conductive coating, film or layer is LASER marked or treated after coating.

17. The method of claim 12, further comprising depositing, applying or coating an at least one thermal interface material or another material onto at least part of at least one of the surfaces of the heat spreader component or heat spreader assembly.

18. The method of claim 12, further comprising depositing or applying at least one additional component onto at least part of at least one of the surfaces of the heat spreader component or heat spreader assembly.

19. The method of claim 18, wherein the at least one additional component comprises a die heater, a heat sink or a combination thereof.

20. A heat spreader assembly, comprising:

an aluminum-based heat spreader component,

at least one coupling layer, wherein the coupling layer comprises zinc, a zinc-based material, tin, a tin-based material or a combination thereof, and

at least one thermally conductive layer comprising nickel, wherein the heat spreader component is coupled to the at least one thermally conductive layer through the at least one coupling layer.