Rheologically controlled metal amalgam comprising non-refractory filler particles

Abstract

The invention relates to a rheologically controlled metal amalgam comprising non-refractory filler particles. Specifically, the present invention discloses an exemplary method of rheology control of metal amalgam as a thermal interface material by including non-refractory filler particles (e.g., non-refractory metal filler particles, etc.) for processing and reliability enhancement. An exemplary method may include rheology control of a metal amalgam containing filler particles (e.g., non-refractory metal filler particles, etc.) for use as a thermal interface material and without sacrificing thermal conductivity while maintaining rheology and diffusion control (e.g., limiting or preventing material migration, etc.) when pressed between two substrates. The rheologically controlled metal amalgam may be used as a thermal interface material between a heat source of an electronic device and another component.

Description

Technical Field

[0001] The present disclosure generally relates to controlling the rheology of metal amalgams, such as thermal interface materials (TIMs), by including non-refractory filler particles (eg, non-refractory filler particles, etc.) for processing and reliability enhancement. Background Art

[0002] This section provides background information related to the present disclosure which is not necessarily prior art.

[0003] Electronic components such as semiconductors, integrated circuit packages, and transistors typically have a pre-designed temperature at which they operate optimally. Ideally, this pre-designed temperature is close to the temperature of the surrounding air. However, the operation of electronic components generates heat. If this heat is not removed, the electronic components may operate at temperatures significantly higher than their normal or desired operating temperature. This excessively high temperature can adversely affect the operating characteristics of the electronic components and the operation of the associated electronic equipment.

[0004] To avoid or at least reduce adverse operating characteristics due to heat generation, heat should be removed, for example, by conducting the heat from the operating electronic component to a heat sink. The heat sink can then be cooled by conventional convection and / or radiation techniques. During conduction, heat can be transferred from the operating electronic component to the heat sink through direct surface contact between the electronic component and the heat sink and / or through contact between the electronic component and the heat sink surface via an intermediate medium or thermal interface material. Thermal interface materials can be used to fill gaps between heat transfer surfaces to improve heat transfer efficiency compared to filling the gaps with air, which is a relatively poor thermal conductor. Summary of the Invention

[0005] The present invention provides a method for rheological control of a metal amalgam, the method comprising including non-refractory filler particles in the metal amalgam, the non-refractory filler particles providing enhanced processing and reliability of the metal amalgam for use as a thermal interface material without sacrificing thermal conductivity while maintaining rheological and diffusion control and / or limiting or preventing material migration.

[0006] The present invention also provides a thermal interface material comprising a metal amalgam comprising non-refractory filler particles for rheological control of the metal amalgam without sacrificing thermal conductivity while maintaining rheological and diffusion control and / or limiting or preventing material migration. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0008] Figure 1 and Figure 2 A comparison is shown between conventional unfilled liquid metal without any nickel and copper fillers and filled liquid metal (FLM) according to exemplary embodiments disclosed herein. The filled liquid metal (FLM) after being filled or loaded with (e.g., from about 1 wt % to about 10 wt %, etc.) nickel and copper has enhanced or increased viscosity, comparable thermal properties, enhanced diffusion control (isotropy) (e.g., limited, reduced, or no material migration, etc.) when pressed between two substrates or sheets, compared to conventional unfilled liquid metal without any nickel and copper fillers. Figure 2 As shown, in thermal reliability tests (e.g. Figure 2 The filled liquid metal (FLM) showed no seepage / pumping / creeping / migration when thermally cycled (e.g., during vertical reliability testing with 1000 cycles in thermal shock from -40°C to 150°C, etc.). This provides a major benefit for handling liquid metal and keeping the material in place (e.g., no material migration, seepage, pumping, or creep, etc.) during application operation in electronic devices. DETAILED DESCRIPTION

[0009] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0010] As recognized herein, conventional rheology-controlled liquid metal systems sacrifice thermal performance because the rheology and diffusion properties are controlled. For example, conventional rheology-controlled materials include liquid metals containing silicone and / or polymer components, which limit the thermal conductivity and thermal resistance of the material. Figure 1 As shown in Figure 1, conventional liquid metals spread unevenly (anisotropically) when pressed between two substrates or sheets (e.g., glass, etc.), which causes problems when processing the material into devices for thermal interface material applications. Conventional liquid metals spread (also known as creep, pumping out, or migration) during thermal reliability testing, as shown in Figure 1. Figure 2 shown.

[0011] After recognizing the above-mentioned shortcomings of conventional rheology-controlled liquid metal systems, exemplary embodiments have been developed and / or disclosed herein for controlling the rheology of metal amalgams (e.g., liquid metals, low-melting alloys, gallium-based liquid metal alloys, etc.) by including, introducing, or using non-refractory metal fillers (e.g., nickel and copper, etc.). When the non-refractory fillers (nickel and copper) are added, the viscosity of the metal amalgam increases without sacrificing the thermal properties of the metal amalgam. The metal fillers remain suspended in the metal amalgam.

[0012] In an exemplary embodiment, a thermal interface material (TIM) includes a non-refractory (non-corrosion resistant) metal filler incorporated into a metal amalgam (e.g., liquid metal, low melting point alloy, etc.) such that a stable metal amalgam suspension is obtained with viscosity control based on the total filler loading without sacrificing thermal performance for the TIM application. In such exemplary embodiments, the thermal reliability of the TIM is tested in a thermal reliability test (e.g., Figure 2 The metal amalgam remains in place (e.g., does not migrate, ooze, pump out, or creep, etc.) during vertical reliability testing (e.g., during 1000 cycles of thermal shock from -40°C to 150°C, as shown). Furthermore, the metal amalgam can be processed onto a substrate in a controlled manner because the rheological control allows the material to diffuse isotropically when pressed between two substrates or sheets, as shown. Figure 1 When a TIM is pressed between two substrates or sheets, isotropic diffusion control occurs (e.g., limited, reduced, or no material migration, etc.), which is a processing advantage in the TIM field because materials will be trapped in applications and the surface coverage of the TIM is important. Conventional liquid metal diffusion anisotropy makes it difficult to process.

[0013] In an exemplary embodiment, a metal alloy (e.g., a low-viscosity gallium-indium-tin liquid metal alloy, etc.) is filled with non-refractory copper and nickel particles. This allows for a stable, homogeneous amalgam suspension, resulting in increased viscosity, rheological control based on the total filler loading, diffusion control during processing for robust wetting of various surfaces, and reliability. While these properties are enhanced, the thermal properties of the material are not sacrificed after the copper and nickel particles are mixed into the metal alloy. The material can appear as a lustrous, shiny silver compound with a custard-like consistency.

[0014] Figure 1 and Figure 2 A comparison is shown between conventional unfilled liquid metal without any nickel and copper fillers and filled liquid metal (FLM) according to exemplary embodiments disclosed herein. The filled liquid metal (FLM) after being filled or loaded with (e.g., from about 1 wt % to about 10 wt %, etc.) nickel and copper has enhanced or increased viscosity, comparable thermal properties, enhanced diffusion control (isotropy) (e.g., limited, reduced, or no material migration, etc.) when pressed between two substrates or sheets, compared to conventional unfilled liquid metal without any nickel and copper fillers. Figure 2 As shown, in thermal reliability tests (e.g. Figure 2The filled liquid metal (FLM) showed no seepage / pumping / creeping / migration when thermally cycled during vertical reliability testing (e.g., 1000 cycles in thermal shock from -40°C to 150°C) as shown. This provides a major benefit for handling liquid metal and keeping the material in place (e.g., the material does not migrate, seep, pump out, creep, etc.) during application operation in electronic devices.

[0015] Metal amalgams (e.g., liquid metals, low melting point alloys, gallium-indium-tin liquid metal alloys, etc.) have been observed to have enhanced or increased viscosity after being filled or loaded with nickel and copper in an amount of about 1% to about 10% by weight (e.g., about 6% by weight, etc.). For example, a low-viscosity liquid consistency was observed for conventional unfilled liquid metal alloys without any nickel and copper fillers. In contrast, a custard-like consistency was observed for metal amalgams containing about 6% by weight (wt%) nickel and copper.

[0016] It has also been observed that metal amalgams (e.g., liquid metals, low melting point alloys, gallium-indium-tin liquid metal alloys, etc.) after being filled or loaded with about 1 wt % to about 10 wt % (e.g., about 6 wt %) of nickel and copper maintain thermal properties comparable to those of conventional unfilled liquid metal alloys without any nickel and copper fillers (e.g., greater than 15 W / mK, etc.). For example, a metal amalgam comprising about 6 wt % of nickel and copper was observed to have a thermal conductivity of 28 to 30 W / mK.

[0017] like Figure 1 As shown in FIG, it is observed that the filled liquid metal after being filled or loaded with (e.g., about 1 wt % to about 10 wt %, etc.) nickel and copper has enhanced diffusion control (isotropy) (e.g., limited, reduced or no material migration, etc.) when pressed between two substrates or sheets (e.g., glass, etc.). In contrast, the conventional unfilled liquid metal without any nickel and copper fillers diffuses unevenly (anisotropically) when pressed between two substrates or sheets, as also shown in FIG. Figure 1 shown.

[0018] like Figure 2 As shown in FIG. 1 , it was observed that the filled liquid metal after being filled or loaded with (e.g., about 1 wt % to about 10 wt %, etc.) nickel and copper did not ooze / pump out / creep / migrate during thermal cycling (e.g., during vertical reliability testing with 1000 cycles of thermal shock from -40°C to 150°C, etc.). In contrast, conventional unfilled liquid metal without any nickel and copper fillers did ooze / pump out / creep / migrate during thermal cycling, as also shown in FIG. Figure 2 shown.

[0019] In an exemplary embodiment, the metal amalgam (e.g., liquid metal, low melting point alloy, etc.) includes nickel and copper such that the weight percentage of nickel and copper is about 1:1 to about 5:1. For example, in an exemplary embodiment, the ratio of nickel to copper can be maintained at 2:1, which achieves a stable, uniform metal amalgam suspension. In an exemplary embodiment, the metal amalgam is loaded or filled with nickel and copper such that the total loading of nickel and copper ranges from about 1 wt % to about 10 wt % (e.g., 4 wt %, 6 wt %, 8 wt %, etc.). In such exemplary embodiments, the filled metal amalgam can have a thermal conductivity greater than 15 W / mK (e.g., 28 W / mK to 30 W / mK, etc.), a thermal conductivity less than about 4 mm², and a strength of less than about 100 W / mK. 2 K / W but not less than about 1mm 2 K / W thermal resistance, and a viscosity of not more than 2800 Pascal·second at a shear rate of 0.5 / s and not more than 75 Pascal·second at a shear rate of 5 / s.

[0020] By way of example only, one exemplary embodiment of a filled metal amalgam comprises a gallium-indium-tin liquid metal alloy filled or loaded with about 6 wt % nickel and copper. In this example, the filled metal amalgam has a thermal conductivity of about 28 W / mK to about 30 W / mK, a thickness of less than about 4 mm, and a thickness of less than about 10 mm. 2 The contact thermal resistance of 1000 psi (K / W), a viscosity of about 28 to about 33 Pascal seconds at a shear rate of 5 s (in air), and a viscosity of about 407 Pascal seconds at a shear rate of 0.5 s (in air). The filled metal amalgam has a custard-like appearance as compared to the consistency observed. The specific alloys, 6 wt% loading, thermal conductivity, thermal resistance, and viscosity provided in this paragraph and elsewhere are merely examples, as other exemplary embodiments can be configured differently, for example, with different metal alloys (e.g., another low-melting alloy with a melting point below 160°C, etc.), different liquid metals, higher or lower weight percent loadings, higher or lower thermal conductivities, higher or lower thermal resistances, and / or higher or lower viscosities, etc.

[0021] By way of further example only, another exemplary embodiment of a filled metal amalgam comprises a gallium-indium-tin liquid metal alloy filled or loaded with about 8 wt % nickel and copper. In this example, the filled metal amalgam has a thermal conductivity of about 28 W / mK to about 30 W / mK, a thickness of less than about 4 mm, and a thickness of less than about 10 mm. 2The contact thermal resistance of 1000 psi (K / W), a viscosity of about 60 to about 65 Pascal seconds at a shear rate of 5 / s (in air), and a viscosity of about 1997 Pascal seconds at a shear rate of 0.5 / s (in air). From a comparison of the consistency, the filled metal amalgam has a custard-like consistency. The specific alloys, 8 weight percent loading, thermal conductivity, thermal resistance, and viscosity provided in this paragraph and elsewhere are merely examples, as other exemplary embodiments can be configured differently, for example, with different metal alloys (e.g., another low-melting alloy with a melting point below 160°C, etc.), different liquid metals, higher or lower weight percent loadings, higher or lower thermal conductivities, higher or lower thermal resistances, and / or higher or lower viscosities, etc.

[0022] By way of further example only, another exemplary embodiment of a filled metal amalgam comprises a gallium-indium-tin liquid metal alloy filled or loaded with about 10 wt % nickel and copper. In this example, the filled metal amalgam has a thermal conductivity of about 28 W / mK to about 30 W / mK, a thickness of less than about 4 mm, and a thickness of less than about 10 mm. 2 K / W contact thermal resistance, a viscosity of about 60 to about 65 Pascal seconds at a shear rate of 5 / s (in air), and a viscosity of about 2595 Pascal seconds at a shear rate of 0.5 / s (in air). From a comparison of consistency observations, the filled metal amalgam has the consistency of a spreadable thick paste. The specific alloys, 10 weight percent loadings, thermal conductivities, thermal resistances, and viscosities provided in this paragraph and elsewhere are merely examples, as other exemplary embodiments can be configured differently, for example, different metal alloys (e.g., another low melting point alloy with a melting point below 160°C, etc.), different liquid metals, higher or lower weight percent loadings, higher or lower thermal conductivities, higher or lower thermal resistances, and / or higher or lower viscosities, etc.

[0023] By comparing with the above three examples with 6 wt %, 8 wt % and 10 wt % nickel and copper loading, a conventional unfilled liquid metal without any nickel and copper filler (filler loading wt % is 0) can have a thermal conductivity of about 28 W / mK to about 30 W / mK, a thermal conductivity of less than about 4 mm 2 K / W contact thermal resistance, a viscosity of about 13 to about 16 Pascal seconds at a shear rate of 5 / s (in air), and a viscosity of about 180 Pascal seconds at a shear rate of 0.5 / s (in air). From a comparison of consistency observations, conventional unfilled liquid metal without any nickel or copper fillers has the consistency of a low viscosity liquid.

[0024] As shown in the above examples, the final consistency of the metal amalgam loaded with non-refractory filler particles is based on the total loading of the metal filler. In an exemplary embodiment, the ratio of nickel and copper by weight is from about 1:1 to about 5:1. For example, a nickel-copper ratio of about 2:1 can be maintained in the filled metal amalgam, which achieves a stable uniform metal amalgam suspension. Even if the consistency of the metal amalgam changes according to the metal filler loading, the thermal properties remain the same, for example, a thermal conductivity greater than 15W / mK (e.g., from about 28W / mK to about 30W / mK, etc.), a thermal resistance less than about 4mm 2 K / W but not less than about 1mm 2 K / W.

[0025] The above examples illustrate an exemplary range of compositions where enhanced effects are observed due to the presence of non-refractory fillers (nickel and copper). When pressed between two substrates, these example compositions exhibited increased viscosity and enhanced diffusion control (e.g., limited, reduced, or no material migration, etc.), but no changes in thermal properties were observed. This is beneficial in the art, as other systems involving rheologically controlled liquid metals sacrifice thermal performance in order to control rheological and diffusion properties.

[0026] Therefore, exemplary embodiments disclosed herein can provide one or more (but not necessarily any or all) of the following advantages. For example, other conventional materials on the market with rheological properties and diffusion control with liquid metal contain silicone and / or polymer components, which limit the thermal conductivity and thermal resistance of the material. In contrast, exemplary embodiments disclosed herein can not sacrifice thermal conductivity and thermal resistance while still maintaining rheological properties and diffusion control (e.g., limiting or preventing material migration, etc.). Exemplary embodiments disclosed herein do not require any solder preforms or surface treatments to keep the material in place and / or wet the surface, because the metal amalgam (e.g., liquid metal, low melting point alloy, etc.) loaded with non-refractory filler particles (e.g., non-refractory metal filler particles, etc.) can wet the surface as it is. Exemplary embodiments disclosed herein do not contain any organic solvents and / or compounds that reduce wetting and / or create voids due to degassing during thermal cycling. For conventional filled liquid metal all-metal amalgam systems, maintaining stable suspension of particles in liquid metal is a key challenge. In exemplary embodiments disclosed herein, after the particles are mixed into a metal amalgam (eg, liquid metal, low melting point alloy, etc.), the metal amalgam remains a stable suspension. This stability is typically not achievable with non-refractory metals.

[0027] Disclosed are exemplary methods for rheologically controlling a metal amalgam as a thermal interface material by including non-refractory filler particles (e.g., non-refractory metal filler particles, etc.) for processing and reliability enhancement. The exemplary methods may include rheologically controlling a metal amalgam including filler particles (e.g., non-refractory metal filler particles, etc.) for use as a thermal interface material without sacrificing thermal conductivity while maintaining rheological and diffusion control (e.g., limiting or preventing material migration, etc.) when pressed between two substrates. The exemplary methods may include using non-refractory (non-corrosion resistant) filler particles (e.g., non-refractory metal filler particles, etc.) to achieve a stable, uniform metal amalgam suspension having viscosity control based on total filler particle loading without sacrificing thermal performance of the thermal interface material application. The rheologically controlled metal amalgam can be used as a thermal interface material between a heat source and another component of an electronic device.

[0028] In an exemplary embodiment, the method includes rheologically controlling a metal amalgam comprising non-refractory filler particles (e.g., non-refractory metal filler particles, etc.), thereby allowing the metal amalgam comprising non-refractory filler particles therein to be processed onto a substrate in a controlled manner, because the rheological control allows the liquid metal comprising the non-refractory filler particles therein to diffuse isotropically when pressed between two substrates.

[0029] In an exemplary embodiment, the method includes rheologically controlling a metal amalgam having non-refractory filler particles (e.g., non-refractory metal filler particles, etc.) therein, thereby allowing the metal amalgam to remain in place (e.g., without material migration, seepage, pumping, oozing, etc.) during thermal reliability testing.

[0030] In an exemplary embodiment, the method includes loading non-refractory filler particles to obtain a stable homogeneous metal amalgam suspension such that the viscosity of the metal amalgam increases.

[0031] In an exemplary embodiment, the method includes loading non-refractory filler particles to obtain rheological control based on total filler particle loading, robust wetting of various surfaces, diffusion control during processing (e.g., limiting or preventing material migration, etc.), and reliability, without sacrificing thermal performance after mixing the non-refractory filler particles into the metal amalgam.

[0032] In an exemplary embodiment, the method includes loading a low-viscosity gallium-indium-tin liquid metal alloy with copper particles and nickel particles to obtain a stable uniform metal amalgam suspension, such that the viscosity of the low-viscosity gallium-indium-tin liquid metal alloy increases.

[0033] In an exemplary embodiment, the method includes loading a low viscosity gallium-indium-tin liquid metal alloy with copper particles and nickel particles to achieve rheological control based on the total metal filler particle loading, robust wetting of various surfaces, diffusion control during processing (e.g., limiting or preventing material migration, etc.), and reliability, without sacrificing thermal performance after mixing the copper particles and nickel particles into the low viscosity gallium-indium-tin liquid metal alloy.

[0034] In an exemplary embodiment, the method includes using a metal amalgam including non-refractory filler particles as a thermal interface material without using or requiring any solder preform or surface treatment to hold the thermal interface material in place and / or wet the surface.

[0035] In an exemplary embodiment, the non-refractory filler particles include non-refractory metal filler particles.And, the method includes mixing the non-refractory metal filler particles into the metal amalgam, thereby providing an all-metal amalgam system, wherein a stable suspension of the non-refractory metal filler particles is maintained in the metal amalgam.

[0036] In an exemplary embodiment, the method includes, after rheologically controlling the metal amalgam including non-refractory filler particles, dispensing or applying the metal amalgam including non-refractory filler particles onto a surface of a heat source, another component, or an electronic device.

[0037] In an exemplary embodiment, the method includes forming a thermal joint between a heat source of an electronic device and another component of the electronic device using a metal amalgam including non-refractory filler particles therein.

[0038] Also disclosed are exemplary embodiments of thermal interface materials (TIMs) comprising metal amalgams containing non-refractory filler particles (e.g., non-refractory metal filler particles, etc.). The thermal interface materials can be used to establish a thermal path for conducting heat from a heat source of an electronic device. During operation of the electronic device, heat can flow from the heat source through the thermal path, thereby reducing the temperature of the heat source.

[0039] In an exemplary embodiment, the metal amalgam comprises non-refractory filler particles (e.g., non-refractory metal filler particles, etc.) that are rheologically controlled without sacrificing thermal conductivity while maintaining the rheology and diffusion control of the thermal interface material (e.g., limiting or preventing material migration, etc.).

[0040] In an exemplary embodiment, a stable homogeneous metal amalgam suspension is achieved through viscosity control based on total filler particle loading without sacrificing thermal properties of the thermal interface material.

[0041] In an exemplary embodiment, the rheology of the metal amalgam containing non-refractory filler particles is controlled, thereby allowing the metal amalgam containing non-refractory filler particles to be processed onto a substrate in a controlled manner. This is because the rheology control allows the metal amalgam containing non-refractory filler particles to spread isotropically and uniformly when pressed between two substrates.

[0042] In an exemplary embodiment, the metal amalgam including non-refractory filler particles is rheologically controlled to allow the metal amalgam to remain in place (eg, not migrate, ooze, pump out, creep, etc.) during thermal reliability testing.

[0043] In an exemplary embodiment, the metal amalgam is loaded with non-refractory filler particles to obtain a stable homogeneous metal amalgam suspension such that the viscosity of the metal amalgam is increased.

[0044] In an exemplary embodiment, the metal amalgam is loaded with non-refractory filler particles to provide rheological control based on the total filler particle loading, robust wetting of various surfaces, diffusion control during processing (e.g., limiting or preventing material migration, etc.), and reliability, without sacrificing thermal performance after the non-refractory filler particles are mixed into the metal amalgam.

[0045] In an exemplary embodiment, the metal amalgam includes a low melting point alloy having a melting point of 160° C. or less.

[0046] In an exemplary embodiment, the non-refractory filler particles comprise copper and nickel. The metal amalgam is loaded with about 1% to about 10% nickel and copper, with a nickel to copper ratio of about 1:1 to about 5:1. Furthermore, the metal amalgam comprising nickel and copper has a thermal conductivity greater than 15 W / mK, a thermal conductivity less than about 4 mm 2 K / W but not less than about 1mm 2 K / W thermal resistance, and a viscosity of not more than 2800 Pascal · second at a shear rate of 0.5 / s and not more than 75 Pascal · second at a shear rate of 5 / s.

[0047] In an exemplary embodiment, the metal amalgam includes a gallium-based liquid metal (eg, a low-viscosity gallium-indium-tin liquid metal alloy, other low-viscosity liquid metals, etc.), and the non-refractory filler particles include copper particles and nickel particles.

[0048] In an exemplary embodiment, the thermal interface material comprises a low viscosity gallium-indium-tin liquid metal alloy loaded with copper particles and nickel particles to obtain a stable uniform metal amalgam suspension such that the viscosity of the low viscosity gallium-indium-tin liquid metal alloy increases.

[0049] In an exemplary embodiment, a thermal interface material comprises a low viscosity gallium-indium-tin liquid metal alloy loaded with copper and nickel particles, thereby achieving rheological control based on the total metal filler particle loading, robust wetting of various surfaces, diffusion control during processing (e.g., limiting or preventing material migration, etc.), and reliability, without sacrificing thermal performance after mixing the copper and nickel particles into the low viscosity gallium-indium-tin liquid metal alloy.

[0050] In exemplary embodiments, the metal amalgam including non-refractory filler particles therein does not contain any organic solvents and / or organic compounds that would otherwise reduce wettability and / or cause voids due to outgassing during thermal cycling.

[0051] In an exemplary embodiment, the metal amalgam in which the non-refractory filler particles are included does not contain any silicone and / or any polymer components that would otherwise reduce thermal conductivity.

[0052] In an exemplary embodiment, the metal amalgam in which the non-refractory filler particles are included consists solely of metal.

[0053] In an exemplary embodiment, the non-refractory filler particles comprise copper and nickel, and the metal amalgam comprises nickel and copper in a ratio of about 1:1 to about 5:1 by weight % and / or by volume %.

[0054] In an exemplary embodiment, the non-refractory filler particles comprise copper and nickel, and the metal amalgam is loaded with about 1% to about 10% nickel and copper.

[0055] In an exemplary embodiment, the non-refractory filler particles comprise copper and nickel, and the metal amalgam comprises nickel and copper in a ratio of about 2:1 by weight % and / or by volume %.

[0056] In an exemplary embodiment, the metal amalgam comprises a gallium-indium-tin liquid metal alloy, and the non-refractory filler particles comprise copper and nickel, such that the gallium-indium-tin liquid metal alloy comprises nickel and copper in a ratio of about 1:1 to about 5:1 by weight % and / or by volume %.

[0057] In an exemplary embodiment, the non-refractory filler particles comprise copper and nickel. Furthermore, the metal amalgam comprises about 5% nickel by volume and about 2.5% copper by volume. In other exemplary embodiments, the metal amalgam is loaded with about 4% nickel and copper by volume.

[0058] In an exemplary embodiment, a thermal interface material comprising a metal amalgam containing non-refractory filler particles can be used to establish a thermal path for conducting heat from a heat source of an electronic device without the use or need for any solder preform or surface treatment to hold the thermal interface material in place (e.g., without migrating, oozing, pumping out, or creeping material, etc.) and / or wetting the surface during thermal reliability testing.

[0059] In an exemplary embodiment, the non-refractory filler particles comprise non-refractory metal filler particles mixed into a metal amalgam, thereby providing an all-metal amalgam system wherein a stable suspension of the non-refractory metal filler particles is maintained in the metal amalgam.

[0060] In an exemplary embodiment, a thermal interface material comprising a metal amalgam containing non-refractory filler particles may be dispensed over a thermal component or another component of an electronic device.

[0061] In an exemplary embodiment, an electronic device includes a heat source, another component, and a thermal interface material as disclosed herein. The thermal interface material is positioned between the heat source and the other component, thereby establishing a thermal path through which heat can flow from the heat source during operation of the electronic device, thereby reducing the temperature of the heat source.

[0062] Exemplary embodiments are provided so that this disclosure will be thorough and will fully convey its scope to those skilled in the art. Many specific details, such as examples of specific components, electronic devices, and methods, are set forth to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that the exemplary embodiments may be embodied in many different forms, and that they should not be construed as limiting the scope of the present disclosure. In some exemplary embodiments, well-known processes, well-known electronic device structures, and well-known technologies are not described in detail. In addition, the advantages and improvements that may be achieved with one or more exemplary embodiments of the present disclosure are provided for illustrative purposes only and do not limit the scope of the present disclosure, as the exemplary embodiments disclosed herein may provide all or none of the above-mentioned advantages and improvements and still fall within the scope of the present disclosure.

[0063] The specific size disclosed herein, specific material and / or specific shape are exemplary in nature and do not limit the scope of the present disclosure. The disclosure of the specific value and specific value range of a given parameter herein does not exclude other values and value ranges that can be used for one or more examples disclosed herein. In addition, it is envisioned that any two specific values of a specific parameter described herein can define the endpoints (that is, the disclosure of the first value and the second value of a given parameter can be interpreted as disclosing any value between the first value and the second value and can also be used for a given parameter) of the value range applicable to the given parameter. For example, if parameter X is exemplified as having value A and also exemplified as having value Z in this article, it is envisioned that parameter X can have the scope of the value from about A to about Z. Similarly, it is envisioned that the disclosure of two or more scopes of the value of a parameter (no matter such scope is nested, overlapping or different) includes all possible combinations of the scope of the value that may be required using the endpoint of the disclosed range. For example, if parameter X is illustrated herein as having values in the range of 1-10, or 2-9, or 3-8, it is also contemplated that parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9.

[0064] The terms used herein are only used to describe the purpose of specific exemplary embodiments and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may also be intended to include plural forms unless the context clearly indicates otherwise. The terms "comprise", "include", "contain", and "have" are inclusive and therefore specify the presence of the features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof. The method steps, processes and operations described herein should not be interpreted as necessarily requiring them to be performed in the particular order discussed or shown, unless explicitly identified as an execution order. It should also be understood that additional or alternative steps may be adopted.

[0065] When an element or layer is referred to as being "on," "engaged to," "connected to," or "coupled to," it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. Conversely, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0066] When applied to a value, the term "about" means that the calculation or measurement allows for some slight imprecision in the value (some accuracy in the value is close; close or reasonably close to the value; close). If for some reason the imprecision provided by "about" is not understood in this ordinary sense in the art, then "about" as used herein at least indicates variations that may be caused by ordinary methods of measuring or using such parameters. For example, the terms "generally", "about" and "substantially" can be used herein to indicate within manufacturing tolerances. Or, for example, when modifying the amount or use of an ingredient or reactant of the present invention, the term "about" as used herein refers to variations in the numerical amount that may occur through typical measurement and processing procedures used, for example, when preparing a concentrate or solution in the real world through unintentional errors in these procedures; through differences in the manufacture, source or purity of the ingredients used to prepare the composition or implement the method; and so on. The term "about" also encompasses amounts that differ due to different equilibrium conditions of the composition resulting from a particular initial mixture. Claims include equivalents to the amounts, whether or not modified by the term "about".

[0067] Although the terms first, second, third etc. can be used here to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or part from another region, layer or part. Terms such as "first", "second" and other numerical terms do not imply order or sequence when used in this article unless the context clearly indicates. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part, without departing from the teachings of exemplary embodiments.

[0068] Spatially relative terms, such as "inside," "outside," "below," "underside," "lower," "above," "upper," etc., may be used herein to describe the relationship of one element or feature to another element or feature, as illustrated in the figures. In addition to the orientations shown in the figures, spatially relative terms can include different orientations of the electronic device in use or operation. For example, if the electronic device in the figures is turned over, an element described as being "below" or the "lower element, component, region, layer or portion" of another element or feature will be oriented as being "above" the other element or feature. Thus, the exemplary term "below" can include both above and below orientations. The electronic device can be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0069] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to the particular embodiment described, but are interchangeable where applicable and can be used in a selected embodiment, even if not explicitly shown or described. They may also be varied in many ways. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims

1. A method for rheological control of a metal amalgam, the method comprising including non-refractory filler particles in the metal amalgam, the non-refractory filler particles providing enhanced processing and reliability of the metal amalgam for use as a thermal interface material without sacrificing thermal conductivity while maintaining rheological and diffusion control and / or limiting or preventing material migration.

2. The method of claim 1, wherein the non-refractory filler particles comprise non-refractory (non-corrosion resistant) metal filler particles.

3. The method of claim 2, wherein the method comprises using the non-refractory (non-corrosion resistant) metal filler particles to achieve a stable homogeneous metal amalgam suspension having viscosity control based on total metal filler particle loading without sacrificing thermal performance for thermal interface material applications.

4. The method of claim 1 , 2 or 3, wherein the method comprises controlling the rheology of the metal amalgam by including the non-refractory filler particles therein, thereby: allowing the metal amalgam comprising the non-refractory filler particles to be processed onto a substrate in a controlled manner, as the rheological control allows the metal amalgam comprising the non-refractory filler particles to diffuse isotropically when pressed between two substrates; and / or The metal amalgam is allowed to remain in place during thermal reliability testing with limited or no material migration.

5. The method of claim 1, wherein: The non-refractory filler particles include non-refractory metal filler particles; and The method includes loading the non-refractory metal filler particles to provide one or more of the following: A stable homogeneous metal amalgam suspension such that the viscosity of the metal amalgam increases; Rheological control based on total filler particle loading, robust wetting of various surfaces, limited or prevented material migration, diffusion control and reliability in processing, without sacrificing thermal performance after mixing the non-refractory filler particles into the metal amalgam; and / or An all-metal amalgam system in which a stable suspension of the non-refractory metal filler particles is maintained in the metal amalgam.

6. The method of claim 1, 2, 3, or 5, wherein the non-refractory filler particles comprise copper and nickel, and wherein: The metal amalgam is loaded with about 1% to about 10% nickel and copper, wherein: The ratio of nickel to copper is from about 1:1 to about 5:1 by weight % and / or volume %; or The ratio of nickel to copper is about 2:1 based on nickel:copper weight % and / or volume %; and / or The metal amalgam comprising nickel and copper has a thermal conductivity greater than 15 W / mK, a thermal conductivity less than about 4 mm 2 K / W but not less than about 1mm 2 K / W thermal resistance, and a viscosity of not more than 2800 Pascal · second at a shear rate of 0.5 / s and not more than 75 Pascal · second at a shear rate of 5 / s.

7. The method of claim 1, 2, 3 or 5, wherein: The metal amalgam comprises a gallium-based liquid metal; and The non-refractory filler particles include copper particles and nickel particles.

8. The method of claim 7, wherein: The gallium-based liquid metal comprises a low-viscosity gallium-indium-tin liquid metal alloy; and The method includes loading the low viscosity gallium-indium-tin liquid metal alloy with the copper particles and the nickel particles, thereby providing A stable homogeneous metal amalgam suspension, such that the viscosity of the low viscosity gallium-indium-tin liquid metal alloy increases; and / or Rheological control based on total filler particle loading, robust wetting of various surfaces, limited or prevented material migration, diffusion control and reliability during processing, without sacrificing thermal performance after mixing the copper particles and the nickel particles into the low viscosity gallium-indium-tin liquid metal alloy.

9. The method of claim 1 , 2, 3 or 5, wherein the method comprises using the metal amalgam including the non-refractory filler particles therein as a thermal interface material and does not use or require any solder preform or surface treatment to hold the thermal interface material in place with limited or no material migration and / or wetting of the surface.

10. The method of claim 1, 2, 3 or 5, wherein: wherein the metal amalgam comprising the non-refractory filler particles does not contain any organic solvents and / or organic compounds which would otherwise reduce wettability and / or cause voids due to outgassing during thermal cycling; and / or wherein the metal amalgam comprising the non-refractory filler particles does not contain any organosilicon and / or any polymer components which would otherwise reduce thermal conductivity; and / or wherein the metal amalgam comprising the non-refractory filler particles consists solely of metal; and / or The metal amalgam includes a low melting point alloy having a melting point of 160° C. or less.

11. The method of claim 1, 2, 3 or 5, wherein the method comprises: After the metal amalgam is rheologically controlled by including the non-refractory filler particles, the metal amalgam including the non-refractory filler particles is dispensed or applied to a surface of a heat source, another component, or an electronic device.

12. The method of claim 1, 2, 3 or 5, wherein: The metal amalgam comprises a gallium-indium-tin liquid metal alloy; and The non-refractory filler particles include copper and nickel such that the gallium-indium-tin liquid metal alloy includes nickel and copper in a ratio of about 1:1 to about 5:1 by weight % and / or by volume %.

13. The method of claim 1, 2, 3, or 5, wherein the method comprises using the metal amalgam including the non-refractory filler particles therein as a thermal interface material to form a thermal bond between a heat source of an electronic device and another component of the electronic device.

14. A thermal interface material comprising a metal amalgam comprising non-refractory filler particles for rheological control of the metal amalgam without sacrificing thermal conductivity while maintaining rheological and diffusion control and / or limiting or preventing material migration.

15. The thermal interface material of claim 14, wherein the non-refractory filler particles comprise non-refractory (non-corrosion resistant) metal filler particles.

16. The thermal interface material of claim 15 , wherein the thermal interface material comprising the metal amalgam is configured to achieve a stable homogeneous metal amalgam suspension comprising the non-refractory (non-corrosion resistant) metal filler particles, the stable homogeneous metal amalgam suspension having viscosity control based on total metal filler particle loading without sacrificing thermal performance of the thermal interface material.

17. The thermal interface material of claim 14, wherein: The non-refractory filler particles include non-refractory metal filler particles; and The metal amalgam is loaded with the non-refractory metal filler particles to provide one or more of the following: A stable homogeneous metal amalgam suspension such that the viscosity of the metal amalgam increases; Rheological control based on total filler particle loading, robust wetting of various surfaces, limited or prevented material migration, diffusion control and reliability in processing, without sacrificing thermal performance after mixing the non-refractory filler particles into the metal amalgam; and An all-metal amalgam system in which a stable suspension of the non-refractory metal filler particles is maintained in the metal amalgam.

18. The thermal interface material according to any one of claims 14 to 17, wherein: The metal amalgam comprises a gallium-based liquid metal; and The non-refractory filler particles include copper particles and nickel particles.

19. The thermal interface material of claim 18, wherein: The gallium-based liquid metal comprises a low-viscosity gallium-indium-tin liquid metal alloy; and The low viscosity gallium-indium-tin liquid metal alloy is loaded with the copper particles and the nickel particles, thereby providing: A stable homogeneous metal amalgam suspension such that the viscosity of the metal amalgam increases; Rheological control based on total metal filler particle loading, robust wetting of various surfaces, limited or prevented material migration, diffusion control and reliability during processing, without sacrificing thermal performance after mixing the copper particles and the nickel particles into the low viscosity gallium-indium-tin liquid metal alloy.

20. The thermal interface material according to any one of claims 14 to 17, wherein: The non-refractory filler particles comprise copper and nickel; The metal amalgam is loaded with about 1% to about 10% nickel and copper, and the ratio of nickel to copper is about 1:1 to about 5:1; and The metal amalgam comprising nickel and copper has a thermal conductivity greater than 15 W / mK, a thermal conductivity less than about 4 mm 2 K / W but not less than about 1mm 2 K / W thermal resistance, and a viscosity of not more than 2800 Pascal · second at a shear rate of 0.5 / s and not more than 75 Pascal · second at a shear rate of 5 / s.

21. The thermal interface material according to any one of claims 14 to 17, wherein: wherein the metal amalgam comprising the non-refractory filler particles does not contain any organic solvents and / or organic compounds which would otherwise reduce wettability and / or cause voids due to outgassing during thermal cycling; and / or wherein the metal amalgam comprising the non-refractory filler particles does not contain any organosilicon and / or any polymer components which would otherwise reduce thermal conductivity; and / or The metal amalgam in which the non-refractory filler particles are included consists solely of metal; and / or The metal amalgam includes a low melting point alloy having a melting point of 160° C. or less.

22. The thermal interface material of any one of claims 14 to 17, wherein the non-refractory filler particles comprise copper and nickel; and wherein: The metal amalgam comprises nickel and copper in a ratio of about 1:1 to about 5:1 by weight % and / or volume %; and / or The metal amalgam is loaded with about 1% to about 10% nickel and copper; and / or The metal amalgam comprises nickel and copper in a ratio of about 2:1 in weight % and / or volume %.

23. The thermal interface material of any one of claims 14 to 17, wherein: The metal amalgam comprises a gallium-indium-tin liquid metal alloy; and The non-refractory filler particles include copper and nickel such that the gallium-indium-tin liquid metal alloy includes nickel and copper in a ratio of about 1:1 to about 5:1 by weight % and / or by volume %.

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