A method, apparatus, and assembly for thermally connecting layers with thermal interface materials comprising rigid particles

Abstract

Thermally bonding a die of a circuit component to a top layer of the circuit component involves coating the die with a thermal interface material (TIM) positioned between the die and the top layer. The TIM comprises a colloid consisting of liquid metal droplets, rigid microparticles, and an uncured polymer. The method further includes pressing the circuit component to deform the liquid metal droplets and form an adhesive layer distance between the die and the top layer, the adhesive layer distance being 90% to 110% of the average particle size of the rigid microparticles. Before coating with the TIM, the average particle size of the liquid metal droplets is larger than the average particle size of the rigid microparticles. The TIM is then cured to form the circuit component.

Description

[Technical Field]

[0001] The present invention relates to a method, apparatus and components for thermally bonding two layers using a thermal interface material comprising rigid microparticles. [Previous Technology]

[0002] Thermal interface materials (TIMs) can be used to thermally bond two or more layers together. For example, in CPU packaging, TIMs are often used to thermally bond the CPU die to the integrated heat spreader (IHS) of the CPU package. Although a variety of TIMs are available, TIMs are currently facing challenges. [Summary of the Invention]

[0003] In a general embodiment, the present invention relates to a method for thermally bonding a die and a top layer. The method includes coating a thermal interface material onto a die of a circuit assembly such that the thermal interface material is located between the die and the top layer of the circuit assembly. In various examples, the circuit assembly may be a processor, an ASIC, or a system-on-a-chip (SoC). In some examples, the top layer may be an integrated heat sink, a heatsink, or a package. The thermal interface material coated onto the die comprises a colloid consisting of liquid metal droplets, rigid microparticles, and an uncured polymer. The liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C. The method includes pressing the circuit assembly to deform the liquid metal droplets and form an adhesive layer distance between the die and the top layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles. Prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles. The method further includes curing the thermal interface material to form the circuit assembly.

[0004] In another general embodiment, the present invention relates to a circuit assembly comprising a grain, a top layer, and a thermal interface material configured to contact the grain layer and the top layer. The thermal interface material comprises a polymer, liquid metal droplets, and rigid microparticles dispersed in the polymer. Furthermore, an adhesive layer distance is formed between the grain and the top layer, the size of which is 95% to 125% of the average particle size of the rigid microparticles. The liquid metal droplets have a first aspect ratio, and the rigid spheres have a second aspect ratio, wherein the first aspect ratio is greater than the second aspect ratio. The liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C.

[0005] In another general embodiment, the present invention relates to an apparatus for thermally bonding a die and a top layer, comprising a container defining a recess and an colloid located within the recess. The colloid comprises liquid metal droplets, rigid microparticles, and an uncured polymer, wherein the container is configured to coat the colloid onto a die of a circuit component. The average particle size of the liquid metal droplets is larger than the average particle size of the rigid microparticles. The liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C.

[0006] In another general embodiment, the present invention relates to a method for thermally bonding two or more layers, comprising: coating a thermal interface material onto a first layer such that the thermal interface material is located between a first layer and a second layer of an assembly. The thermal interface material comprises a colloid consisting of liquid metal droplets, rigid microparticles, and an uncured polymer. The liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C. The method includes: pressing the assembly to deform the liquid metal droplets; and forming an adhesive layer distance between the grains and the top layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles. Prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles. The method further includes curing the thermal interface material to form the assembly.

[0007] This invention provides both low contact resistance at the material interface and low thermal resistance throughout the material. Low contact resistance can be achieved by coating an uncured polymer, allowing the polymer and liquid metal droplets to adhere to the surface of the layer to achieve the desired contact resistance. Low overall thermal resistance of the material can be achieved through the liquid metal droplets, including the size and / or shape of the droplets and / or the size of the rigid particles. Furthermore, compared to other methods, the method described herein does not require high pressure during installation because the polymer is coated in an uncured state, and the method described herein can be installed at room temperature (e.g., 23 °C + / - 3 °C) because the polymer is coated in an uncured state and the liquid metal droplets are in a liquid phase at room temperature. Moreover, curing the polymer can suppress the outflow of the liquid metal droplets. Furthermore, the rigid microparticles allow for effective control of the adhesive layer distance, and the application of the rigid microparticles followed by the colloid composed of polymer and liquid metal droplets further enables effective control of the adhesive layer distance. The feasibility and other benefits of various embodiments of the present invention will become clear from the following description.

Implementation Method

[0017] Certain exemplary embodiments of the present invention will now be described to provide a comprehensive understanding of the principles of the components, functions, manufacture, use of the components, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the components, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and the scope of the various embodiments of the present invention is defined only within the scope of the claims. Features illustrated or described in connection with a particular exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

[0018] Coating a material onto a die of a circuit component such that the material is located between the die and an integrated heat sink (IHS) may require balancing the overall thermal resistance of the material with the contact resistance at the material interface. For example, a polymer material may have low contact resistance at the material interface but high overall thermal resistance. A solid metal may have low overall thermal resistance but high contact resistance at the material interface. Furthermore, some solid materials (polymers or metals) may require high pressure during mounting to achieve the desired contact resistance. Moreover, achieving the required adhesive layer distance between the die and the integrated heat sink is challenging when using a thermal interface material containing liquid metal droplets.

[0019] Therefore, in various embodiments, the present invention provides a thermal interface material (TIM), an assembly for thermally bonding two layers, and a circuit assembly. The circuit assembly is capable of providing both a low contact resistance at the material interface and a low thermal resistance throughout the material, while simultaneously achieving the desired adhesive layer thickness. Furthermore, compared to other solid materials, the thermal interface material may not require high pressure for installation. For example, the thermal interface material may require only a pressure of less than or equal to 50 pounds per square inch for installation (e.g., compression). According to the present invention, the thermal interface material may comprise a polymer, liquid metal droplets, and rigid microparticles. The liquid metal droplets may be dispersed in the polymer, and / or the rigid microparticles may be dispersed in the polymer.

[0020] As used in this specification, the terms "polymer" and "polymeric polymer" refer to both prepolymers, oligomers, homopolymers, and copolymers. As used in this specification, "prepolymer" refers to a polymer precursor that can react or polymerize with one or more reactive groups to form a higher molecular weight or cross-linked state.

[0021] The polymer can be a thermosetting polymer, a thermoplastic polymer, or a combination thereof. As used herein, the term "thermosetting" refers to a polymer that is irreversibly fixed once cured or crosslinked, wherein the polymeric chains of the polymeric components are covalently bonded, typically induced, for example, by heat or radiation. In various instances, the curing or crosslinking reaction can occur under ambient conditions. Once cured or crosslinked, a thermosetting polymer may not melt upon heating and is insoluble in conventional solvents. As used herein, the term "thermoplastic" refers to a polymeric component in which the constructed polymeric chains are not covalently bonded (e.g., crosslinked), and thus the polymer is capable of liquid flow upon heating and is soluble in conventional solvents. In some embodiments, the polymer can be elastomer (e.g., rubber-like, soft, elastic) or rigid (e.g., glass-like). For example, the polymer can be an elastomer.

[0022] The thermosetting polymer may include a crosslinking agent, which may include (for example): amino plastics, polyisocyanates (including terminal isocyanates), polyepoxides, β-hydroxyalkylamides, polymeric acids, acid anhydrides, organometallic acid functional materials, polyamines, polyamides, or combinations thereof. The polymer may have functional groups that are reactive to the crosslinking agent.

[0023] The polymers used in the thermal interface materials described herein can be selected from a variety of polymers well known in the art. For example, the thermosetting polymer may include: acrylic polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers (e.g., poly(dimethylsiloxane)), fluoropolymers, polyisoprene polymers (e.g., rubber), and copolymers thereof (e.g., styrene-ethylene-butene-styrene), or combinations thereof. The functional groups on the thermosetting polymer may be selected from any variety of reactive functional groups, including (e.g.) carboxylic acid groups, amino groups, epoxy groups, hydroxyl groups, mercapto groups, carbamate groups, amide groups, urea groups, isocyanate groups (including terminal isocyanate groups), thiol groups, and combinations thereof.

[0024] The thermoplastic polymer may include propylene-ethylene copolymer, styrene-butadiene-styrene, styrene-ethylene-butene-styrene, or combinations thereof. The melting point of the polymer may be at least 100°C, such as (for example) at least 120°C, at least 150°C, or at least 200°C.

[0025] The liquid metal used in the thermal interface material may include gallium, gallium alloys, indium, indium alloys, tin, tin alloys, mercury, mercury alloys, or combinations thereof. The liquid metal may be in a liquid phase at a temperature of at least -20°C (e.g., in a bulk form, the melting point may be below -20°C), such as (e.g.) at least -19°C, at least -10°C, at least 0°C, at least 5°C, at least 10°C, at least 15°C, at least 20°C, or at least 25°C. The liquid metal may be in a liquid phase at a temperature not greater than 30°C (e.g., in a bulk form, the melting point may be below 30°C), such as (e.g.) not greater than 25°C, not greater than 20°C, not greater than 15°C, not greater than 10°C, not greater than 5°C, not greater than 0°C, or not greater than -10°C. The liquid metal may be in a liquid phase at least within a temperature range of -20°C to 30°C (e.g., in a bulk form, the melting point may be below a temperature in the range of -20°C to 30°C), such as (e.g.) between -19°C to 30°C, -19°C to 25°C, or -19°C to 20°C. Determining whether the liquid phase reaches the corresponding temperature can be done at atmospheric absolute pressure. In some embodiments, the thermal interface material may include gallium-indium-tin (e.g., gallium-indium-tin alloy (Galinstan)) with a melting point of -19°C.

[0026] The rigid microparticles may include iron, iron alloys (e.g., steel, stainless steel), vanadium, vanadium alloys, niobium, niobium alloys, titanium, titanium alloys, copper, copper alloys (e.g., bronze), rigid polymers, glass, ceramics, or combinations thereof. The rigid microparticles are resistant to deformation and / or erosion by the liquid metal droplets. For example, the Young's modulus of the rigid microparticles may be at least 100 MPa (megapascals), such as (e.g.) at least 110 MPa, at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 500 MPa, at least 750 MPa, at least 1 GPa (gigapascals), or at least 2 GPa. The Young's modulus may be measured in accordance with ASTM E111-17.

[0027] The thermal interface material can be prepared by means of a colloid composed of the polymer, the liquid metal and the rigid particles, such that the liquid metal droplets and the rigid particles are substantially dispersed in the polymer. For example, the polymer, liquid metal droplets and rigid particles can be mixed using a high-shear mixer, a centrifugal mixer, shaking in a container, a mortar and pestle, ultrasonic vibration or a combination thereof. Further illustrative methods for preparing the colloid are detailed in (1) PCT Publication No. WO / 2019 / 136252, entitled "Method of Synthesizing a Thermally Conductive and Stretchable Polymer Composite", (2) U.S. Patent Application Publication No. 2017 / 0218167, entitled "Polymer Composite with Liquid Phase Metal Inclusions", and (3) U.S. Patent No. 10,777,483, entitled "Method, apparatus, and assembly for thermally connecting layers", the entire contents of which are incorporated herein by reference. In various embodiments, the thermal interface material may be prepared by forming a layer of rigid microparticles and then coating the rigid microparticle layer with a colloid composed of the polymer and the liquid metal.

[0028] The composition and / or mixing techniques can be selected to make the viscosity of the thermal interface material colloid below 850,000 cP (percent poise) in its uncured state, such as (for example) below 750,000 cP, below 500,000 cP, below 250,000 cP, 200,000 cP, below 150,000 cP, below 100,000 cP, below 50,000 cP, below 15,000 cP, below 14,000 cP, below 13,000 cP, below 12,000 cP, below 11,000 cP, or below 10,000 cP. The viscosity of the thermal interface material colloid can be measured at room temperature using a rotational viscometer or a cone-plate viscometer. The viscosity measurement can be performed at a selected frequency suitable for producing static viscosity (e.g., because the material is a non-Newtonian fluid).

[0029] The thermal interface material may include at least 7% by volume of polymer (based on the total volume of the thermal interface material), such as (for example) at least 10% by volume, at least 15% by volume, at least 20% by volume, at least 25% by volume, at least 30% by volume, at least 35% by volume, at least 40% by volume, at least 45% by volume, or at least 50% by volume, all based on the total volume of the thermal interface material. The thermal interface material may include no more than 70% by volume of polymer (based on the total volume of the thermal interface material), such as (for example) no more than 65% by volume, no more than 60% by volume, no more than 55% by volume, no more than 50% by volume, no more than 45% by volume, or no more than 40% by volume, all based on the total volume of the thermal interface material. The thermal interface material may include a polymer in the range of 7% to 70% by volume (based on the total volume of the thermal interface material), such as (for example) 20% to 50% by volume, 30% to 50% by volume, 30% to 60% by volume, 40% to 60% by volume, or 40% to 70% by volume, all based on the total volume of the thermal interface material.

[0030] The thermal interface material may include at least 1% by volume of liquid metal droplets (based on the total volume of the thermal interface material), such as (for example) at least 5% by volume of liquid metal droplets, at least 10% by volume of liquid metal droplets, at least 20% by volume of liquid metal droplets, at least 30% by volume of liquid metal droplets, at least 40% by volume of liquid metal droplets, at least 50% by volume of liquid metal droplets, or at least 60% by volume of liquid metal droplets, all based on the total volume of the liquid metal droplets. The thermal interface material may include no more than 92% by volume of liquid metal droplets (based on the total volume of the thermal interface material), such as (for example) no more than 90% by volume of liquid metal droplets, no more than 80% by volume of liquid metal droplets, no more than 70% by volume of liquid metal droplets, no more than 60% by volume of liquid metal droplets, no more than 50% by volume of liquid metal droplets, no more than 40% by volume of liquid metal droplets, no more than 30% by volume of liquid metal droplets, no more than 20% by volume of liquid metal droplets, or no more than 10% by volume of liquid metal droplets, all based on the total volume of the thermal interface material. The thermal interface material may include liquid metal droplets ranging from 1 vol% to 92 vol% (based on the total volume of the thermal interface material), such as (for example) 1 vol% to 90 vol% liquid metal droplets, 5 vol% to 50 vol% liquid metal droplets, 40 vol% to 60 vol% liquid metal droplets, 5 vol% to 90 vol% liquid metal droplets, or 30 vol% to 50 vol% liquid metal droplets, all based on the total volume of the thermal interface material. The content of the liquid metal droplets affects the morphology and thermal conductivity of the thermal interface material.

[0031] The thermal interface material may include at least 0.1% by volume of rigid particles (based on the total volume of the thermal interface material), such as (for example) at least 1% by volume of rigid particles (based on the total volume of the thermal interface material), at least 5% by volume of rigid particles, at least 10% by volume of rigid particles, or at least 20% by volume of rigid particles, all based on the total volume of the liquid metal droplet. The thermal interface material may include no more than 30% by volume of rigid particles (based on the total volume of the thermal interface material), such as (for example) no more than 25% by volume of rigid particles, no more than 20% by volume of rigid particles, no more than 10% by volume of rigid particles, no more than 5% by volume of rigid particles, or no more than 1% by volume of rigid particles, all based on the total volume of the thermal interface material. The thermal interface material may include rigid microparticles ranging from 0.1 vol% to 30 vol% (based on the total volume of the thermal interface material), such as (for example) 0.1 vol% to 10 vol% rigid microparticles, 0.1 vol% to 5 vol% rigid microparticles, 1 vol% to 10 vol% rigid microparticles, or 1 vol% to 5 vol% rigid microparticles, all based on the total volume of the thermal interface material. The content of these rigid microparticles affects the morphology of the thermal interface material, the thermal conductivity of the thermal interface material, and the control of the adhesive layer thickness of the thermal interface material. For example, insufficient rigid microparticles can lead to a lack of control over the adhesive layer thickness of the thermal interface material, while excessive rigid microparticles can lead to undesirable changes in the morphology and / or thermal conductivity of the thermal interface material.

[0032] The composition and / or mixing technique can be selected to achieve the desired average particle size of the liquid metal droplets in the thermal interface material. The average particle size of the liquid metal droplets can be at least 1 micrometer, such as (e.g.) at least 5 micrometers, at least 10 micrometers, at least 20 micrometers, at least 30 micrometers, at least 35 micrometers, at least 40 micrometers, at least 50 micrometers, at least 60 micrometers, at least 70 micrometers, at least 80 micrometers, at least 90 micrometers, at least 100 micrometers, at least 120 micrometers, or at least 150 micrometers. The average particle size of the liquid metal droplets can be no greater than 200 micrometers, such as (e.g.) no greater than 150 micrometers, no greater than 120 micrometers, no greater than 100 micrometers, no greater than 90 micrometers, no greater than 80 micrometers, no greater than 70 micrometers, no greater than 60 micrometers, no greater than 50 micrometers, no greater than 40 micrometers, no greater than 35 micrometers, no greater than 30 micrometers, no greater than 20 micrometers, no greater than 10 micrometers, or no greater than 5 micrometers. For example, the average particle size of the liquid metal droplets can be in the range of 1 micrometer to 200 micrometers, such as (e.g.) 5 micrometers to 150 micrometers, 15 to 150 micrometers, 35 micrometers to 150 micrometers, 35 micrometers to 70 micrometers, or 5 micrometers to 100 micrometers. In various embodiments, the composition and / or mixing technology can be selected to achieve an average particle size of the liquid metal droplets in the thermal interface material that is larger than the average particle size of the rigid microparticles, such as (e.g.) at least 1%, at least 2%, at least 5%, at least 10%, or at least 20% larger than the average particle size of the rigid microparticles.

[0033] As used herein, "average particle size" refers to the median average size (i.e., D50) measured using microscopic techniques (e.g., optical microscopy or electron microscopy). This size can be the diameter of a spherical particle or along the length of its maximum size (if the particle is elliptical or otherwise irregularly shaped). As used herein, "D10" of a particle refers to a particle diameter in which 10% of all particles have a diameter smaller than this particle diameter. As used herein, "D90" of a particle refers to a particle diameter in which 90% of all particles in a powder have a diameter smaller than this particle diameter.

[0034] The degree of polymerization distribution of the liquid metal droplet can be unimodal or multimodal (e.g., bimodal, trimodal). Utilizing a multimodal, multi-particle-size distribution can increase the packing density of the liquid metal droplet in the thermal interface material. In some embodiments where the degree of polymerization distribution is unimodal, the degree of polymerization distribution of the liquid metal droplet in the polymer can be in the range of 0.3 to 0.4.

[0035] The average particle size of the rigid microparticles in the thermal interface material can be selected to achieve the desired adhesive layer distance in the component. The average particle size of the rigid microparticles can be at least 1 micrometer, such as (for example) at least 5 micrometers, at least 10 micrometers, at least 20 micrometers, at least 30 micrometers, at least 35 micrometers, at least 40 micrometers, at least 50 micrometers, at least 60 micrometers, at least 70 micrometers, at least 80 micrometers, at least 90 micrometers, at least 100 micrometers, at least 120 micrometers, or at least 125 micrometers. The average particle size of the rigid microparticles can be no greater than 150 micrometers, such as (for example) no greater than 125 micrometers, no greater than 120 micrometers, no greater than 100 micrometers, no greater than 90 micrometers, no greater than 80 micrometers, no greater than 70 micrometers, no greater than 60 micrometers, no greater than 50 micrometers, no greater than 40 micrometers, no greater than 35 micrometers, no greater than 30 micrometers, no greater than 20 micrometers, no greater than 10 micrometers, or no greater than 5 micrometers. For example, the average particle size of the rigid microparticle can be in the range of 1 micrometer to 150 micrometers, such as (for example) 15 to 150 micrometers, 5 micrometers to 125 micrometers, 35 micrometers to 125 micrometers, 35 micrometers to 70 micrometers, or 50 micrometers to 70 micrometers.

[0036] Before use, the thermal interface material may be stored in a container 100, as shown in FIG1. ​​For example, the container may include a plurality of walls 102 defining a recess, and the thermal interface material colloid 104 may be stored in the recess. The thermal interface material 104 may be in an uncured state in the container 100. Storing the thermal interface material 104 in the container 100 may inhibit the curing of the thermal interface material 104. The container 100 may be a pillow bag, syringe, beaker, jar, bottle, bucket, or a combination thereof. In various examples, the container 100 may be a ready-to-use dispensing device, such as, for example, a pillow bag or syringe. In other examples, the thermal interface material 104 may not necessarily need to be stored and may be used after being made into a colloid without storage.

[0037] As used in this specification, the terms "cured" and "hardened" refer to the chemical cross-linking of components in a colloid or material coated on a substrate, or the increase in viscosity of components in a colloid or material coated on a substrate. Therefore, the terms "cured" and "hardened" do not merely encompass the physical drying of a colloid or material through the evaporation of a solvent or carrier. In this respect, as used in examples including thermosetting polymers, the term "cured" refers to a state of a colloid or material in which components have been chemically reacted to form new covalent bonds (e.g., new covalent bonds between the adhesive resin and the curing agent). As used in examples including thermoplastic polymers, the term "cured" refers to a state of a colloid or material in which the temperature of the thermoplastic polymer is lowered below its melting point, causing an increase in viscosity. In examples that include both thermosetting polymers and thermoplastic polymers, the term "cured" refers to one or both of these polymers being cured, as described below.

[0038] Curing of the thermosetting polymer can be achieved by applying a temperature of at least -20°C to the thermal interface material 104, such as (e.g.) at least 10°C, at least 50°C, at least 100°C, or at least 150°C. Curing can be achieved by applying a temperature not exceeding 300°C to the thermal interface material 104, such as (e.g.) not exceeding 250°C, not exceeding 200°C, not exceeding 150°C, not exceeding 100°C, or not exceeding 50°C. Curing can be achieved by applying a temperature in the range of -20°C to 300°C to the thermal interface material 104, such as (e.g.) 10°C to 200°C, or 50°C to 150°C. For example, curing may include thermally baking the thermal interface material. The time period for which the temperature is applied may be greater than 1 minute, such as (e.g.) greater than 5 minutes, greater than 30 minutes, greater than 1 hour, or greater than 2 hours.

[0039] The thermal interface material 104 can be dispensed from the container 100 and coated onto a layer in an uncured state. In various examples, the thermal interface material 104 does not include the rigid microparticles in the container 100, and the rigid microparticles are coated as a microparticle layer, and the thermal interface material 104 without the rigid microparticles is coated on the microparticle layer. Subsequently, the thermal interface material 104 can be cured to form a cured thermal interface material 104. Curing the thermal interface material 104 may include: heating the thermal interface material 104 (e.g., in examples including thermosetting polymers); adding a catalyst to the thermal interface material 104; exposing the thermal interface material 104 to air; cooling the thermal interface material 104 (e.g., in examples having thermoplastic polymers); applying pressure to the thermal interface material 104; or combinations thereof. Curing the thermal interface material 104 can increase the viscosity of the thermal interface material colloid to greater than 15,000 cP, such as (for example) greater than 20,000 cP, greater than 30,000 cP, greater than 50,000 cP, greater than 100,000 cP, greater than 150,000 cP, greater than 200,000 cP, greater than 250,000 cP, greater than 500,000 cP, greater than 750,000 cP, or greater than 850,000 cP. For example, the polymer in the thermal interface material 104 can be cured. In various instances, the thermal interface material 104 can be an adhesive. The polymer in the thermal interface material 104 can be selected to reduce gas release during curing.

[0040] The thermal interface material according to the invention can be coated onto a first layer such that the thermal interface material is located between two layers of an assembly comprising the first layer and a second layer. The thermal interface material can be coated in a single step or at least two steps. For example, the rigid microparticles can be coated onto the first layer in a microparticle layer. The mixture of the rigid microparticles and a solvent can be coated onto the first layer through, for example, a glass pipette, and thereafter the solvent can be removed, leaving the rigid microparticles in the first layer. The flash point of the solvent allows the solvent to be removed from the first layer at room temperature. For example, the solvent may include acetone or the like. Depending on the average particle size and type of rigid microparticles used, coating the rigid microparticles before coating a colloid composed of the polymer and liquid metal droplets can reduce the aggregation of the rigid microparticles, which may lead to improper control of the adhesive layer thickness and / or otherwise cause problems related to the coating of the thermal interface material (e.g., syringe blockage during coating).

[0041] The first layer may be a heat-generating electronic component (e.g., integrated circuit, circuit assembly), and the second layer may be a thermally conductive top layer. For example, the top layer may be a heat sink, a heat fin, or a package. The assembly may then be compressed to deform the liquid metal droplets in the thermal interface material to form an adhesive layer distance between the first and second layers, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles. The thermal interface material may be cured to form the assembly. Applying the thermal interface material 104 in its uncured state achieves the desired contact resistance and allows the assembly to be compressed under lower pressure. The use of rigid microparticles allows for more effective control of the adhesive layer distance because, as the distance between the first and second layers approaches the average particle size of the rigid microparticles, the rigid microparticles can prevent further reduction in the distance between the first and second layers. For example, the rigid particles can contact the first layer and / or the second layer, greatly increasing the pressure required to further reduce the distance between the first layer and the second layer. The thermal interface material can be coated onto various layers and devices, and circuit components are described below with reference to Figures 2A-2B, but are not limited to only one circuit component.

[0042] Referring to FIG2A, a thermal interface material 204 may be coated onto a die 206 of a circuit assembly 208, such that the thermal interface material 204 may be located between the die 206 and a top layer 210 of the circuit assembly 200. The coating of the thermal interface material 204 may occur in one step or at least two steps, as described above. Coating the thermal interface material 204 onto the die 206 may include spraying, spin coating, dip coating, roll coating, curtain coating, film coating, brush coating, extrusion, dispensing, or a combination thereof. The thermal interface material 204 may be coated in an uncured state, such that the thermal interface material uniformly covers the surfaces of the die 206 and the top layer 210, thereby achieving the desired level of surface contact between them. In various examples, the thermal interface material 204 may be directly coated onto the die 206, and subsequently the top layer 210 may be directly coated onto the thermal interface material 204. In various other examples, the thermal interface material 204 can be directly coated onto the top layer 210, and subsequently, the grain 206 can be directly coated onto the thermal interface material 204. In various examples, after coating, the thermal interface material 204 can directly contact the grain 206 and the top layer 210. In some embodiments, the coating of the thermal interface material 204 can be limited to the surface of the grain 206, so that the thermal interface material 204 can be effectively utilized.

[0043] As used in this specification, particularly with respect to layers, films, or materials, the terms "on top of," "on to," "above," and variations thereof (e.g., "coated on," "formed on," "deposited on," "provided on," "located on," and the like) refer to coating, forming, depositing, providing, or otherwise applying to the surface of a substrate, but not necessarily in contact with that substrate surface. For example, a thermal interface material "coated" "on" a substrate does not exclude the presence of another layer or other layers having the same or different composition between the coated thermal interface material and the substrate. Similarly, a second layer "coated" on a first layer does not exclude the presence of another layer or other layers having the same or different composition between the coated second layer and the coated thermal interface material.

[0044] The circuit assembly 200 can be compressed. For example, referring to the detailed views of FIG3A-3B, the grain 206 and the top layer 210 can be forced together such that a first distance d1 can be reduced to a second adhesive layer distance dbl. Before coating and / or before a compression process, the average particle size of the liquid metal droplets 312 in the thermal interface material 204 can be selected to be greater than a desired adhesive layer distance dbl formed between the grain 206 and the top layer 210. For example, prior to coating and / or prior to a pressing process, the average particle size of the liquid metal droplets 312 may be larger than the adhesive layer distance dbl, such as (for example) 1%, 2%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, or 75% larger than the adhesive layer distance dbl. Before coating and / or before a pressing process, the average particle size of the liquid metal droplets 312 may be no more than 100% larger than the adhesive layer distance dbl, such as (for example) no more than 75%, no more than 50%, no more than 40%, no more than 30%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, or no more than 2%. Before coating and / or before a pressing process, the average particle size of the liquid metal droplets 312 may be in the range of 1% to 100% larger than the adhesive layer distance dbl, such as (for example) 1% to 50% larger than the adhesive layer distance dbl, 1% to 30% larger than the adhesive layer distance dbl, 2% to 30% larger than the adhesive layer distance dbl, or 5% to 20% larger than the adhesive layer distance dbl.

[0045] The average particle size of the rigid microparticles 316 in the thermal interface material 204 can be selected according to the desired adhesive layer distance dbl, and is formed between the grain 206 and the top layer 210, such that further reduction of the adhesive layer distance dbl can be limited by the rigid microparticles 316. For example, the adhesive layer distance dbl can be at least 95% of the average particle size of the rigid microparticles 316, such as (for example) at least 96%, at least 97%, at least 98%, at least 99%, at least 100%, or at least 101% of the average particle size of the rigid microparticles 316. The adhesive layer distance dbl can be no greater than 125% of the average particle size of the rigid microparticles 316, such as (for example) no greater than 120%, no greater than 115%, no greater than 110%, or no greater than 105% of the average particle size of the rigid microparticles 316. For example, the adhesive layer distance dbl can be in the range of 95% to 125% of the average particle size of the rigid microparticles 316, such as (for example) 95% to 120%, 95% to 110%, 100% to 120%, 100% to 110%, or 101% to 110% of the average particle size of the rigid microparticles 316.

[0046] Before coating and / or before a pressing process, the average particle size of the liquid metal droplets 312 may be larger than the average particle size of the rigid microparticles 316, such as (for example) at least 5%, at least 10%, at least 20%, or at least 25% larger than the average particle size of the rigid microparticles 316.

[0047] The circuit assembly 200 can be compressed by applying a compressive force to the thermal interface material 204, which can deform the liquid metal droplet 312 and disperse it in the polymer 314 of the thermal interface material 204. Because the thermal interface material 204 is in an uncured state, the polymer 314 is still uniformly covered and movable, allowing the compressive force to deform the liquid metal droplet 312 to the size of the rigid particle 316. The liquid metal droplet 312 can be in a liquid phase during deformation, so that the required deformation effect can be achieved with a relatively low pressure for compression. During compression, when the reduction of the first distance dl reaches the average particle size of the rigid particle 316, the pressure required for compression will increase significantly, thereby indicating that the required adhesive layer distance dbl has been achieved and / or inhibiting the further reduction of the first distance dl. In various examples, coating the rigid microparticles 316 before coating the colloid composed of the polymer 314 and the liquid metal droplets 312 can reduce the aggregation of the rigid microparticles 316, which could interfere with the control of the desired adhesive layer distance dbl. Therefore, the rigid microparticles 316 enable effective control of the adhesive layer distance dbl.

[0048] The clamping force can be in the range of 1 PSI to 50 PSI, such as (for example) 2 PSI to 45 PSI, 10 PSI to 45 PSI, 15 PSI to 45 PSI, 15 PSI to 30 PSI, or 20 PSI to 40 PSI.

[0049] The liquid metal droplet 312 may be generally spherical, as shown in FIG3A, and subsequently may be generally elliptical, as shown in FIG3B. In various examples, the liquid metal droplet 312 may have a first average aspect ratio before compression, and the liquid metal droplet 312 may have a second average aspect ratio after compression. The second average aspect ratio may differ from the first average aspect ratio. For example, the second average aspect ratio may be greater than the first average aspect ratio. The average aspect ratio may be an average of the ratio of the width of the liquid metal droplet 312 to the height of the liquid metal droplet 312. In various examples, the first aspect ratio may be 1, and the second aspect ratio may be greater than 1. In some embodiments, the first aspect ratio may be in the range of 1 to 1.5. In some embodiments, the second aspect ratio may be at least 0.5 larger than the first aspect ratio, such as (e.g.) at least 1 larger, at least 2 larger, or at least 5 larger. The width of the liquid metal droplet 312 may be substantially aligned with the longitudinal plane of the thermal interface material 204 in the circuit assembly 200, and the height of the liquid metal droplet 312 may be substantially aligned with the thickness (e.g., distance d1) of the thermal interface material 204. Once the circuit assembly 200 is pressed, the width of the liquid metal droplet 312 increases. For example, in some embodiments, the radius of the spherical liquid metal droplet may be 100 micrometers before pressing (e.g., a first aspect ratio of 1), and after pressing, it may reach an adhesive layer thickness of 20 micrometers, and the liquid metal droplet may deform into an elliptical shape with a width of 316 micrometers (e.g., a second aspect ratio of 15.6).

[0050] The rigid particle 316 may be generally spherical, as shown in FIG3A, and may substantially maintain its sphericity thereafter, as shown in FIG3B. In various examples, the rigid particle 316 may have a third average aspect ratio before compression, and the rigid particle 316 may substantially maintain the third average aspect ratio after compression. In various examples, the third average aspect ratio may be in the range of 0.9 to 1.1, such as (for example) the third average aspect ratio may be 1. The second average aspect ratio of the liquid metal droplet 312 shown in FIG3B may be greater than the third average aspect ratio of the rigid particle shown in FIG3B, such as (for example) at least 0.1 greater than the third aspect ratio, such as (for example) at least 0.5 greater than the third aspect ratio, at least 1 greater than the third aspect ratio, at least 2 greater than the third aspect ratio, or at least 5 greater than the third aspect ratio.

[0051] In various embodiments, the average sphericity of the rigid microparticles 316 may be at least 0.9, such as (e.g.) at least 0.95, at least 0.96, at least 0.97, at least 0.98, or at least 0.99. The rigid microparticles 316 may be substantially uniform in size. For example, the D90 of the rigid microparticles 316 may not be greater than 125% of the D50 of the rigid microparticles 316, such as (e.g.) not greater than 120%, not greater than 115%, or not greater than 110%, or not greater than 125% of the D50 of the rigid microparticles 316. The D90 of the rigid microparticles 316 may be at least the D50 of the rigid microparticles 316, such as (e.g.) at least 101%, at least 105%, or at least 110%, and not greater than 125% of the D50 of the rigid microparticles 316. For example, the D90 of the rigid particle 316 is in the range of at least 125% of the D50 of the rigid particle 316, such as (for example) 101% to 120%, 101% to 115%, 101% to 110%, 101% to 105%, or 100% to 105% of the D50 of the rigid particle 316. The D10 of the rigid particle 316 may be at least 90% of the D50 of the rigid particle 316, such as (for example) at least 95%, at least 98%, or at least 99% of the D50 of the rigid particle 316. The D10 of the rigid particle 316 may not be greater than the D50 of the rigid particle 316, such as (for example) not greater than 99%, not greater than 98%, or not greater than 95% of the D50 of the rigid particle 316. For example, the D10 of the rigid microparticle 316 can be within the range of 90% to D50 of the rigid microparticle 316, such as (for example) 90% to 99%, 95% to 99%, 95% to 100%, 98% to 100%, or 99% to 100% of D50 of the rigid microparticle 316. Therefore, due to the uniformity and shape of the rigid microparticle 316, the orientation of the rigid microparticle 316 may not affect the adhesive layer distance dbl.

[0052] In various examples, the liquid metal droplet 312 and the rigid microparticle 316 may include an average height ranging from 85% to 100% of the adhesive layer distance dbl (measured in the direction from the grain 206 to the top layer 210), such as (for example) 90% to 100%, 90% to 99%, 95% to 99%, 95% to 100%, 98% to 100%, or 99% to 100% of the adhesive layer distance dbl.

[0053] In some instances, the liquid metal droplets 312 and rigid particles 316, after being compressed, can be aligned with a substantial monolayer, as shown in FIG3B. This monolayer can be achieved by selecting the average particle size of the liquid metal droplets 312, the average particle size of the rigid particles 316, and the adhesive layer distance dbl. Arranging the liquid metal droplets 312 and rigid particles 316 in a monolayer can reduce the thermal resistance of the thermal interface material 204.

[0054] The thermal interface material 204 can be cured to form the circuit assembly 200. Curing the thermal interface material 204 can increase the viscosity of the polymer 314 and harden the polymer 314. For example, the polymer 314 can become a solid. In various instances, the polymer 314 is an elastomer after curing. Curing the polymer 314 can suppress the outflow of the liquid metal droplets 312 during the thermal cycling of the circuit assembly 200 and can provide mechanical bonding between the grains 206 and the top layer 210.

[0055] The component 200 may include an adhesive layer distance dbl formed between the grain 206 and the top layer 210 in the cured component, and is not greater than 150 micrometers, such as (for example) not greater than 145 micrometers, not greater than 140 micrometers, not greater than 120 micrometers, not greater than 100 micrometers, not greater than 80 micrometers, not greater than 70 micrometers, not greater than 50 micrometers, not greater than 40 micrometers, not greater than 35 micrometers, or not greater than 30 micrometers. The component 200 may include an adhesive layer distance dbl formed between the grain 206 and the top layer 210 in the cured component, and is at least 15 micrometers, such as (for example) at least 30 micrometers, at least 35 micrometers, at least 40 micrometers, at least 50 micrometers, at least 70 micrometers, at least 80 micrometers, at least 100 micrometers, at least 120 micrometers, at least 140 micrometers, or at least 145 micrometers. The component 200 may include an adhesive layer distance dbl formed between the grain 206 and the top layer 210 in the cured component, and in the range of 15 micrometers to 150 micrometers, such as (for example) 15 micrometers to 90 micrometers, 15 micrometers to 70 micrometers, 30 micrometers to 70 micrometers, 35 micrometers to 70 micrometers, or 15 micrometers to 100 micrometers.

[0056] The curing process may occur during a first time period, and the compaction process may occur during a second time period. The first time period may occur after or at least partially overlap with the second time period. For example, the liquid metal droplet 312 may be deformed before the polymer 314 is substantially cured, such that the deformation of the liquid metal droplet 312 can be performed with a lower compaction force.

[0057] The average particle size of the liquid metal droplet 314, the average particle size of the rigid microparticle 316, and the deformation of the liquid metal droplet 312 can improve the thermal resistance of the thermal interface material 204. For example, the thermal resistance of the thermal interface material 204 after curing may not exceed 30 (°K*mm2) / W, such as (for example) not exceeding 20 (°K*mm2) / W, not exceeding 15 (°K*mm2) / W, not exceeding 10 (°K*mm2) / W, not exceeding 9 (°K*mm2) / W, not exceeding 8 (°K*mm2) / W, not exceeding 7 (°K*mm2) / W, or not exceeding 5 (°K*mm2) / W. The thermal resistance of the thermal interface material 204 after curing can be at least 0.5 (°K*mm2) / W, such as (for example) at least 1 (°K*mm2) / W, at least 2 (°K*mm2) / W, at least 3 (°K*mm2) / W, at least 5 (°K*mm2) / W, or at least 10 (°K*mm2) / W. The thermal resistance of the cured thermal interface material 204 can range from 0.5 (°K*mm²) / W to 30 (°K*mm²) / W, such as (for example) 0.5 (°K*mm²) / W to 20 (°K*mm²) / W, 0.5 (°K*mm²) / W to 15 (°K*mm²) / W, 1 (°K*mm²) / W to 10 (°K*mm²) / W, 2 (°K*mm²) / W to 10 (°K*mm²) / W, or 2 (°K*mm²) / W to 8 (°K*mm²) / W. This thermal resistance can be measured using a DynTIM-S instrument (available from Siemens in Munich, Germany), a TIMA instrument (from NanoTest GmbH, Germany), and / or a LongWin LW 9389 (Taiwan).

[0058] The die 206 may include, for example, an integrated circuit, such as a processor, an ASIC, or a system-on-a-chip (SoC). The top layer 210 may be an integrated heat sink. The thermal interface material 204 may be directly coated between the processor and the integrated heat sink. For example, the thermal interface material 204 may be TIM1, TIM1.5, or a combination thereof. TIM1 may be used in a covered package to thermally bond a die to an integrated heat sink. TIM1.5 may be used in a bare die package to thermally bond a die to a heat sink.

[0059] In various other examples, referring to FIG2B, thermal interface material 216 may be applied between the top layer 210 (e.g., an integrated heat sink) and a different top layer 218. The top layer 218 may include a heat sink. For example, the thermal interface material 216 may be a TIM2.

[0060] In various other instances, the thermal interface material according to the invention can be used in a systematic package. For example, a single horizontal thermal interface material layer may be in contact with multiple dies on one side (e.g., the integrated circuit may include multiple dies, or multiple integrated circuits may be in contact with the same side of the thermal interface material) and with one or more top layers on the other side.

[0061] Example

[0062] The invention will be more fully understood by referring to the illustrative and non-limiting embodiments provided below. It should be understood that the inventions described herein are not necessarily limited to the embodiments set forth in this section.

[0063] The control of the adhesive layer distance in a component is based on the test of three different thermal interface material formulations according to Table 1 below.

[0064] Table 1: Example formulations Example formulation Poly(dimethylsiloxane) polymer (volume %) Galinstan liquid metal droplets (volume %) Rigid glass particles (volume %) Rigid glass particles (D) 50 ) Comparative object 1 35 65 0 2 34.9 65 0.1 20-30 μm 3 32.4 65 2.6 8-12 μm

[0065] Each thermal interface material formulation is coated onto a first layer of an assembly, and a second layer of the assembly is coated on top of the thermal interface material formulation. The assembly is then compressed using a clamping force of 15 PSI or 29 PSI. This pressure is continuously applied until the thermal interface material formulation can no longer be compressed under pressure, and after compression is complete, the thickness of the resulting adhesive layer is measured. This procedure is repeated multiple times in each formulation.

[0066] Comparative formulation 1 was observed to have low control over the adhesive layer thickness at a clamping force of either 15 PSI or 29 PSI, resulting in a minimum distance between the first and second layers. Compared to Comparative formulation 1, Comparative formulation 2 was observed to have favorable control over the adhesive layer thickness at both clamping forces of 15 PSI and 29 PSI, resulting in an average adhesive layer thickness similar to the median particle size of the glass rigid microparticles. Compared to Comparative formulation 1, Comparative formulation 3 was observed to have favorable control over the adhesive layer thickness at both clamping forces of 15 PSI and 29 PSI, resulting in an average adhesive layer thickness similar to the median particle size of the glass rigid microparticles. Furthermore, a clamping force of 29 PSI was observed to achieve a more uniform adhesive layer thickness in both Comparative formulations 2 and 3.

[0067] The morphology of Example Comparison 1 is shown in Figure 4A, while the morphology of Example Comparison 2 is shown in Figure 4B. Compared to Example Comparison 1, the morphology of Example Comparison 2 was observed to be substantially unaffected by the addition of the glass rigid microparticles.

[0068] Various forms of the present invention include (but are not limited to) the forms listed below.

[0069] 1. A method comprising: coating a thermal interface material onto a die of a circuit assembly such that the thermal interface material is located between the die and a top layer of the circuit assembly, wherein the thermal interface material coated onto the die comprises a colloid consisting of liquid metal droplets, an uncured polymer, and rigid microparticles, wherein the liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C; pressing the circuit assembly to deform the liquid metal droplets and form an adhesive layer distance between the die and the top layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles, wherein prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles; and curing the thermal interface material to form a cured assembly.

[0070] 2. A method comprising: coating rigid microparticles onto a grain of a circuit assembly; coating a colloid composed of an uncured polymer and liquid metal droplets onto the grain of the circuit assembly coated with rigid microparticles to form a thermal interface material between the grain and a top layer of the circuit assembly, wherein the liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C; pressing the circuit assembly to deform the liquid metal droplets and form an adhesive layer distance between the grain and the top layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles, wherein prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles; and curing the thermal interface material to form a cured assembly.

[0071] 3. The method as described in any one of clauses 1-2, wherein the die includes a processor.

[0072] 4. The method as described in any one of items 1-3, wherein the top layer includes an integrated heat sink for the processor.

[0073] 5. The method as described in any one of clauses 1-4, wherein the top layer includes a heat sink, an integrated heat sink, or a package.

[0074] 6. The method as described in any one of clauses 1-5, wherein in the curing assembly, the distance between the grain and the top layer forming an adhesive layer is not greater than 150 micrometers.

[0075] 7. The method as described in any one of clauses 1-6, wherein in the curing assembly, the distance between the grain and the top layer forming an adhesive layer is not greater than 100 micrometers.

[0076] 8. The method as described in any one of clauses 1-7, wherein in the cured component, the distance between the grain and the adhesive layer formed between the grain and the top layer is not greater than 70 micrometers.

[0077] 9. The method as described in any one of clauses 1-8, wherein in the curing assembly, the distance between the grain and the top layer forming an adhesive layer is in the range of 15 micrometers to 90 micrometers.

[0078] 10. The method of any one of clauses 1-9, wherein prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is greater than the distance between the grain and the top layer formed in the curing assembly.

[0079] 11. The method as described in any one of clauses 1-10, wherein prior to deposition, the average size of the liquid metal droplets in the thermal interface material is greater than the distance between the grain and the top layer of the curing assembly by 1% to 100%.

[0080] 12. The method as described in any one of clauses 1-11, wherein the liquid metal droplet comprises gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or a combination thereof.

[0081] 13. The method as described in any one of clauses 1-12, wherein the thermal resistance of the thermal interface material after curing is not greater than 30 (°K*mm2) / W.

[0082] 14. The method described in any one of clauses 1-13, wherein the thermal resistance of the thermal interface material after curing is not greater than 10 (°K*mm2) / W.

[0083] 15. The method as described in any one of clauses 1-14, wherein the liquid metal droplet constitutes a single-peak multi-size distribution.

[0084] 16. The method as described in any one of clauses 1-14, wherein the liquid metal droplets constitute a multi-peak, multi-size distribution.

[0085] 17. The method as described in any one of clauses 1-16, wherein the polymer comprises a thermosetting polymer.

[0086] 18. The method as described in any one of clauses 1-17, wherein the polymer comprises a thermoplastic polymer.

[0087] 19. The method as described in any one of clauses 1-18, wherein the viscosity of the colloid is less than 850,000 cP prior to curing.

[0088] 20. The method as described in any one of clauses 1-19, wherein the liquid metal droplet is generally spherical before deposition and generally elliptical after the assembly is pressed.

[0089] 21. The method as described in any one of clauses 1-20, wherein after the component is compressed, the liquid metal droplet and the rigid microparticle each include an average height ranging from 85% to 100% of the adhesive layer distance.

[0090] 22. The method as described in any one of clauses 1-21, wherein the thermal interface material comprises 30 vol% to 92 vol% of liquid metal droplets, 0.1 vol% to 5 vol% of rigid microparticles, and 7 vol% to 70 vol% of polymer.

[0091] 23. The method as described in any one of clauses 1-22, wherein the curing occurs in a first time period and the compaction occurs in a second time period, wherein the first time period occurs after the second time period or at least partially overlaps with the second time period.

[0092] 24. The method as described in any one of clauses 1-23, wherein the average particle size of the rigid microparticle is in the range of 1 micrometer to 150 micrometers.

[0093] 25. The method as described in any one of clauses 1-24, wherein the distance between the grain and the top layer of the adhesive layer is 100% to 110% of the average particle size of the rigid microparticles.

[0094] 26. The method as described in any one of clauses 1-25, wherein the sphericity of the rigid microparticle is at least 0.9.

[0095] 27. The method as described in any one of clauses 1-26, wherein the rigid microparticles include iron, ferroalloys, vanadium, vanadium alloys, niobium, niobium alloys, titanium, titanium alloys, copper, copper alloys, rigid polymers, glass, ceramics, or combinations thereof.

[0096] 28. The method as described in any one of clauses 1-27, wherein the liquid metal droplet comprises gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or a combination thereof.

[0097] 29. The method as described in any one of clauses 1-28, wherein the Young's modulus of the rigid microparticle is at least 100 MPa.

[0098] 30. The method as described in any one of clauses 1-29, wherein the D90 of the rigid particle is not greater than 125% of the D50 of the rigid particle.

[0099] 31. The method as described in any one of clauses 1-30, wherein the rigid particles are generally spherical before deposition and after the assembly is compacted.

[0100] 32. A circuit assembly manufactured by the method described in any one of clauses 1-31.

[0101] 33. A component comprising: a grain; a top layer; and a thermal interface material configured to contact the grain layer and the top layer, wherein the thermal interface material comprises a polymer, a liquid metal droplet, and rigid microparticles, an adhesive layer formed between the grain and the top layer is 95% to 125% of the average particle size of the rigid microparticles, the liquid metal droplet has a first aspect ratio, and the rigid microparticles have a second aspect ratio, the first aspect ratio being greater than the second aspect ratio, and the liquid metal droplet being in a liquid phase at least in a temperature range of -20°C to 30°C.

[0102] 34. The component as described in clause 33, wherein the die includes a processor.

[0103] 35. The component as described in any of clauses 33-34, wherein the top layer includes a heat sink, an integrated heat sink, or a package.

[0104] 36. The component as described in any one of clauses 33-35, wherein in the component, the distance between the grain and the adhesive layer formed between the grain and the top layer is not greater than 150 micrometers.

[0105] 37. The component as described in any one of clauses 33-36, wherein in the component, the distance between the grain and the adhesive layer formed between the grain and the top layer is not greater than 100 micrometers.

[0106] 38. The component as described in any one of clauses 33-37, wherein in the component, the distance between the grain and the adhesive layer formed between the grain and the top layer is not greater than 70 micrometers.

[0107] 39. The component as described in any one of clauses 33-38, wherein in the component, the distance between the grain and the top layer forming an adhesive layer is in the range of 15 micrometers to 90 micrometers.

[0108] 40. The component as described in any one of clauses 33-39, wherein the liquid metal droplet comprises gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or a combination thereof; and / or the rigid microparticle comprises iron, iron alloy, vanadium, vanadium alloy, niobium, niobium alloy, titanium, titanium alloy, copper, copper alloy, polymer, glass, ceramic, or a combination thereof.

[0109] 41. The component as described in any one of clauses 33-40, wherein the liquid metal droplets and rigid microparticles are dispersed in the polymer.

[0110] 42. The component as described in any one of clauses 33-41, wherein the thermal interface material comprises 30 vol% to 92 vol% of liquid metal droplets, 0.1 vol% to 5 vol% of rigid microparticles, and 7 vol% to 70 vol% of polymer.

[0111] 43. The component as described in any one of clauses 33-42, wherein the thermal resistance of the thermal interface material is not greater than 30 (°K*mm2) / W.

[0112] 44. The component as described in any one of clauses 33-43, wherein the thermal resistance of the thermal interface material is greater than 10 (°K*mm2) / W.

[0113] 45. The component as described in any one of clauses 33-44, wherein the liquid metal droplets constitute a single-peak multi-size distribution.

[0114] 46. The component as described in any one of clauses 33-44, wherein the liquid metal droplets constitute a multi-peak, multi-size distribution.

[0115] 47. The component as described in any one of clauses 33-46, wherein the polymer comprises a thermosetting polymer.

[0116] 48. The component as described in any one of clauses 33-47, wherein the polymer comprises a thermoplastic polymer.

[0117] 49. The component as described in any one of clauses 33-48, wherein the liquid metal droplet is generally elliptical and the rigid particle is generally spherical.

[0118] 50. The component as described in any one of clauses 33-49, wherein the Young's modulus of the rigid microparticle is at least 100 MPa.

[0119] 51. The component as described in any one of clauses 33-50, wherein the average particle size of the rigid microparticles is in the range of 1 micrometer to 150 micrometers.

[0120] 52. The component as described in any one of clauses 33-51, wherein the adhesive layer distance between the grain and the top layer is 100% to 110% of the average particle size of the rigid microparticles.

[0121] 53. The component as described in any one of clauses 33-52, wherein the sphericity of the rigid microparticle is at least 0.9.

[0122] 54. The component as described in any one of clauses 33-53, wherein the rigid microparticles include iron, iron alloy, vanadium, vanadium alloy, niobium, niobium alloy, titanium, titanium alloy, copper, copper alloy, rigid polymer, glass, ceramic, or a combination thereof.

[0123] 55. The component as described in any one of clauses 33-54, wherein the D90 of the rigid particle is not greater than 125% of the D50 of the rigid particle.

[0124] 56. The component as described in any one of clauses 33-55, wherein the rigid microparticles are generally spherical before deposition and after compaction of the component.

[0125] 57. An apparatus for thermally bonding a die and a top layer, comprising: a container defining a recess; and a colloid located in the recess, wherein the colloid comprises liquid metal droplets, rigid microparticles, and an uncured polymer, wherein the container is configured to coat the colloid onto a die of a circuit component, wherein the average particle size of the liquid metal droplets is larger than the average particle size of the rigid microparticles, and the liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C.

[0126] 58. A system for thermally bonding a grain and a top layer, comprising: a first container defining a first recess, and a second container defining a second recess; the first container comprising a colloid located within the first recess, wherein the colloid comprises liquid metal droplets and an uncured polymer, and wherein the first container is configured to coat the colloid onto a grain of a circuit assembly, wherein the liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C, the second container comprising a mixture of rigid microparticles and a solvent, wherein the second container is configured to coat the mixture onto the grain of the circuit assembly, and wherein the average particle size of the liquid metal droplets is larger than the average particle size of the rigid microparticles.

[0127] 59. The device as described in clause 57, wherein the container is a syringe, or the system 58 as described in clause 58, wherein at least one of the first container and the second container is a syringe.

[0128] 60. The device as described in clause 57, wherein the container is a pillow bag, or the system as described in clause 58, wherein at least one of the first container and the second container is a pillow bag.

[0129] 61. The device as described in any of clauses 57 and 59-60, or the system as described in any of clauses 58 and 59-60, wherein the die includes a processor.

[0130] 62. The device as described in any of clauses 57 and 59-61, or the system as described in any of clauses 58 and 59-61, wherein the top layer includes a heat sink, an integrated heat sink, or a package.

[0131] 63. The device as described in any of clauses 57 and 59-62, or the system as described in any of clauses 58 and 59-62, wherein the average particle size of the liquid metal droplets in the colloid is greater than the distance between the grains of the circuit component and the top layer of the adhesive layer.

[0132] 64. The device as described in any one of clauses 57 and 59-63, or the system as described in any one of clauses 58 and 59-63, wherein the liquid metal droplet comprises gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or a combination thereof.

[0133] 65. The apparatus as described in any one of clauses 57 and 59-63, or the system as described in any one of clauses 58 and 59-63, wherein the liquid metal droplet is in a liquid phase at least in the temperature range of -20°C to 30°C.

[0134] 66. The apparatus as described in any one of clauses 57 and 59-65, or the system as described in any one of clauses 58 and 59-65, wherein the liquid metal droplets constitute a single-peak multi-size distribution.

[0135] 67. The apparatus as described in any one of clauses 57 and 59-65, or the system as described in any one of clauses 58 and 59-65, wherein the liquid metal droplets constitute a multi-peak, multi-size distribution.

[0136] 68. The apparatus as described in any of clauses 57 and 59-67, or the system as described in any of clauses 58 and 59-67, wherein the polymer comprises a thermosetting polymer.

[0137] 69. The apparatus as described in any one of clauses 57 and 59-68, or the system as described in any one of clauses 58 and 59-68, wherein the viscosity of the colloid is less than 250,000 cP prior to curing.

[0138] 70. The apparatus as described in any of clauses 57 and 59-69, or the system as described in any of clauses 58 and 59-69, wherein the liquid metal droplet is generally spherical.

[0139] 71. The device as described in any of clauses 57 and 59-70, or the system as described in any of clauses 58 and 59-70, wherein the average particle size of the rigid microparticles is in the range of 1 micrometer to 150 micrometers.

[0140] 72. The device as described in any of clauses 57 and 59-71, or the system as described in any of clauses 58 and 59-71, wherein the adhesive layer distance between the grain and the top layer is 100% to 110% of the average particle size of the rigid microparticle.

[0141] 73. The device as described in any of clauses 57 and 59-72, or the system as described in any of clauses 58 and 59-72, wherein the sphericity of the rigid microparticle is at least 0.9.

[0142] 74. The device as described in any one of clauses 57 and 59-73, or the system as described in any one of clauses 58 and 59-73, wherein the rigid microparticles include iron, iron alloys, vanadium, vanadium alloys, niobium, niobium alloys, titanium, titanium alloys, copper, copper alloys, rigid polymers, glass, ceramics, or combinations thereof.

[0143] 75. The device as described in any of clauses 57 and 59-74, or the system as described in any of clauses 58 and 59-74, wherein the Young's modulus of the rigid particles is at least 100 MPa.

[0144] 76. The device as described in any of clauses 57 and 59-75, or the system as described in any of clauses 58 and 59-75, wherein the D90 of the rigid particle is not greater than 125% of the D50 of the rigid particle.

[0145] 77. The device as described in any of clauses 57 and 59-76, or the system as described in any of clauses 58 and 59-76, wherein the rigid particles are generally spherical.

[0146] 78. The device as described in any of clauses 57 and 59-77, or the system as described in any of clauses 58 and 59-77, wherein after the component is clamped, the liquid metal droplet and the rigid microparticle each have an average height ranging from 85% to 100% of the adhesive layer distance.

[0147] 79. An assembly includes: a first layer (e.g., a grain); a second layer (e.g., a top layer); and a thermal interface material disposed between the first layer and the second layer. The thermal interface material comprises a polymer, liquid metal droplets, and rigid microparticles. The liquid metal droplets have a first aspect ratio, and the rigid microparticles have a second aspect ratio. The first aspect ratio is greater than the second aspect ratio, for example, at least 0.1, at least 0.5, at least 1, at least 2, or at least 5 greater. The liquid metal droplets are in a liquid phase at least in a temperature range of -20°C to 30°C. An adhesive layer between the first and second layers has a distance of 95% to 125% of the average particle size of the rigid microparticles. Optionally, the thermal interface material comprises 30% to 92% by volume of liquid metal droplets, 0.1% to 5% by volume of rigid microparticles, and 7% to 70% by volume of polymer. Optionally, the Young's modulus of the rigid microparticles is at least 100. MPa, for example: at least 110 MPa, at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 500 MPa, at least 750 MPa, at least 1 GPa, or at least 2 GPa. Optionally, the liquid metal droplet includes gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or combinations thereof, and the rigid particles include iron, iron alloy (e.g., stainless steel), vanadium, vanadium alloy, niobium, niobium alloy, titanium, titanium alloy, copper, copper alloy, polymer, glass, ceramic, or combinations thereof. Optionally, the liquid metal droplet and the rigid particles are dispersed in the polymer. Optionally, the average particle size of the rigid particles can be in the range of 1 micrometer to 150 micrometers.

[0148] 80. A method of manufacturing the component described in claim 79, the method comprising: coating the thermal interface material onto the first layer such that the thermal interface material is located between the first layer and the second layer, optionally wherein coating the thermal interface material comprises coating rigid microparticles onto the first layer and coating a colloid composed of an uncured polymer and liquid metal droplets onto the first layer coated with the rigid microparticles to form a first thermal interface material between the first layer and the second layer; coating a colloid composed of the polymer, liquid metal droplets and rigid microparticles onto the first layer, or a combination thereof; pressing the circuit component to deform the liquid metal droplets and form an adhesive layer distance between the first layer and the second layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles, wherein prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles; and curing the thermal interface material to form a cured component.

[0149] Those skilled in the art will recognize that the components, articles, methods, and accompanying discussions described herein are examples for the sake of clarity of concept, and that modifications of various forms have been considered. Therefore, as used herein, the specific examples presented and their accompanying discussions are intended to represent a more general category. In general, the use of any specific example is intended to represent its category, and the omission of specific elements (e.g., operations), devices, and articles should not be considered as a limitation.

[0150] Regarding the appended claims, those skilled in the art will understand that the operations described herein can be performed in virtually any order. Furthermore, although the various operational processes are presented in a sequential manner, it should be understood that the various operations can be performed in other orders than those described, or simultaneously. Examples of these alternative orders may include overlapping, interleaved, interrupted, reordered, additional, preparatory, complementary, simultaneous, reversible, or other varied orders, unless the context otherwise requires. Moreover, the use of terms such as "corresponding to," "about," or other past tense adjectives generally does not intend to exclude such variations, unless the context otherwise requires.

[0151] Although various examples have been detailed herein, those skilled in the art will conceive of and implement numerous modifications, variations, substitutions, alterations, and equivalents of those examples. Furthermore, the materials disclosed for certain elements may be substituted with other materials. Therefore, it is understood that the preceding specification and the accompanying claims are intended to cover all such modifications or variations and to fall within the scope of the disclosed examples. The subsequent claims are intended to cover all such modifications or variations.

[0152] This specification sets forth various features and characteristics to provide an understanding of the composition, structure, manufacture, use, and operation of the invention, including the disclosed compositions, coatings, and methods. It is understood that the various features and characteristics of the invention described herein can be combined in any suitable manner, whether or not such combinations are explicitly detailed in this specification. The inventors and applicant expressly intend that such combinations of features and characteristics be included within the scope of the invention described herein. Thus, the claims can be modified in any combination to define any feature and characteristic explicitly or substantially described, or otherwise explicitly or substantially supported, in this specification. Furthermore, the applicant reserves the right to amend the scope of the claims to affirmatively deny features and characteristics that may exist in the prior art, even if such features and characteristics are not explicitly described in this specification. Therefore, any such amendment will not add new substance to the specification or claims and will comply with the requirements of written record, sufficient disclosure, and supplementary substance.

[0153] Any numerical range described in this specification refers to all sub-ranges containing the same numerical precision (i.e., specific numbers having the same value) within the range. For example, the range "1.0 to 10.0" refers to all sub-ranges containing the minimum value 1.0 and the maximum value 10.0 (inclusive), such as (for example) the range "2.4 to 7.6", even though the range "2.4 to 7.6" is not explicitly stated in the text of the specification. Therefore, the applicant reserves the right to amend this specification (including the claims) to explicitly describe any identical numerical precision covered within the ranges described in this specification. Since all such ranges are inherently described in this specification, any modification to any such sub-range will comply with the requirements of written record, sufficient disclosure, and additional substance.

[0154] Furthermore, unless otherwise specified or required by the context, any numerical parameter described in this specification (such as, for example, expressed values, ranges, quantities, ratios, and the like) may be interpreted as being preceded by the word "approximately," even if the word "approximately" does not explicitly appear before a number. In addition, the numerical parameters described in this specification should be interpreted based on the number of significant figures reported, numerical precision, and by applying common rounding techniques. It should also be understood that the numerical parameters described in this specification will necessarily possess the inherent variability of the underlying measurement techniques used to determine the values ​​of such parameters.

[0155] Although the numerical ranges and parameters describing the broad scope of the present invention are rough estimates, the values ​​described in specific examples are recorded as precisely as possible. However, any numerical value will inherently include some errors, which will necessarily be caused by the standard deviation found in the corresponding test measurements.

[0156] Throughout this specification, the terms "various examples," "certain examples," "an example," "an instance," or similar expressions refer to a specific feature, structure, or characteristic described in relation to that example being included in an example. Therefore, the use of phrases such as "various examples," "certain examples," "an example," "an instance," or similar expressions throughout this specification does not necessarily refer to the same example. Furthermore, such specific features, structures, or characteristics can be combined in any suitable manner in one or more examples. Therefore, a specific feature, structure, or characteristic illustrated or described in relation to an example can be combined with features, structures, or characteristics of another example in a partially or wholly manner without limitation. Such modifications or variations are intended to be included within the scope of the invention.

[0157] Any patent, publication, or other document referenced herein is incorporated herein by reference in its entirety, unless otherwise stated, provided that the incorporated material does not conflict with any existing descriptions, definitions, statements, drawings, or other disclosures expressly set forth herein. Thus, to the extent necessary, the express disclosures set forth herein will supersede any conflicting material incorporated by reference. Any material or portion thereof incorporated herein that conflicts with any existing definitions, statements, or other disclosures set forth herein will only be incorporated to such an extent that the incorporated material does not conflict with existing inventive material. The applicant reserves the right to amend this specification to expressly reference any substance or portion thereof incorporated by reference. Amending this specification to include such incorporated substance will comply with the requirements of written record, sufficient disclosure, and supplementary substance.

[0158] Although specific examples of the present invention have been described above for illustrative purposes, those skilled in the art will readily conceive of various variations in the details of the present invention without departing from the present invention, as defined in the appended claims.

[0159] Although various specific embodiments of the invention are provided to illustrate its various forms and potential applications, it will be apparent to those skilled in the art that such variations and modifications will occur. Therefore, the invention described herein should be understood to be at least as broad as it is claimed, and not narrower than that defined by the specific illustrative embodiments provided herein.

[0160] It goes without saying that the invention described in this specification is not limited to the examples summarized in the description or embodiments. Various other forms are described and illustrated herein. [Simplified Explanation of the Diagram]

[0008] The features and advantages of various embodiments of the present invention, as well as their implementation, will become more apparent and better understood by referring to the following description of examples in conjunction with the accompanying drawings, wherein:

[0009] Figure 1 is a schematic diagram of a container including a thermal interface material colloid according to the present invention;

[0010] FIG2A is a side sectional view of a circuit assembly including a thermal interface material according to the present invention;

[0011] FIG2B is a side sectional view of a circuit assembly including a thermal interface material according to the present invention;

[0012] Figure 3A is a detailed view of region 3A of the circuit assembly in Figure 2 before the circuit assembly is pressed;

[0013] Figure 3B shows the circuit assembly of Figure 3A after the circuit assembly is pressed;

[0014] Figure 4A shows an image of the cured example formulation 1 after compression; and

[0015] Figure 4B shows the image of the cured example formulation 2 after compression.

[0016] The corresponding elements in all views are indicated by their corresponding labels. The examples presented herein are merely illustrative of certain instances and should not be construed in any way as limiting the scope of such instances.

Claims

1. A die-mounted assembly, comprising: One grain; One top floor; The material includes a thermal interface material configured to contact the grain layer and the top layer, wherein the thermal interface material comprises a polymer, liquid metal droplets, and rigid microparticles; an adhesive layer between the grains and the top layer is 95% to 125% of the average particle size of the rigid microparticles; the liquid metal droplets have a first aspect ratio, and the rigid microparticles have a second aspect ratio, wherein the first aspect ratio is greater than the second aspect ratio; and the liquid metal droplets are in a liquid phase at least in the temperature range of -20°C to 30°C.

2. The grain assembly as claimed in claim 1, wherein the liquid metal droplet comprises gallium, gallium alloy, indium, indium alloy, tin, tin alloy, mercury, mercury alloy, or combinations thereof, and the rigid microparticle comprises iron, iron alloy, vanadium, vanadium alloy, niobium, niobium alloy, titanium, titanium alloy, copper, copper alloy, polymer, glass, ceramic, or combinations thereof.

3. The grain assembly as claimed in claim 1, wherein the Young's modulus of the rigid microparticle is at least 100 MPa.

4. The grain assembly as claimed in claim 1, wherein the thermal interface material comprises 30 vol% to 92 vol% of liquid metal droplets, 0.1 vol% to 5 vol% of rigid microparticles, and 7 vol% to 70 vol% of polymer.

5. The grain assembly as claimed in claim 1, wherein the liquid metal droplet and the rigid microparticle each have an average height ranging from 85% to 100% of the adhesive layer distance.

6. A method for preparing a grain assembly, comprising: The process involves coating rigid microparticles onto a grain of a circuit assembly; coating a colloid composed of an uncured polymer and liquid metal droplets onto the grain of the circuit assembly coated with the rigid microparticles to form a thermal interface material between the grain and a top layer of the circuit assembly, wherein the liquid metal droplets are in a liquid phase at least in the temperature range of -20°C to 30°C; pressing the circuit assembly to deform the liquid metal droplets and form an adhesive layer distance between the grain and the top layer, the adhesive layer distance being 95% to 125% of the average particle size of the rigid microparticles, wherein, prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles; and curing the thermal interface material to form a cured assembly.

7. A method for preparing a grain-based assembly, comprising: A thermal interface material is coated onto a die of a circuit assembly, such that the thermal interface material is located between the die and the top layer of the circuit assembly. The thermal interface material coated onto the die comprises a colloid consisting of liquid metal droplets, uncured polymer, and rigid microparticles, wherein the liquid metal droplets are in a liquid phase at least within a temperature range of -20°C to 30°C. The circuit assembly is then pressed to deform the liquid metal droplets and form an adhesive layer distance between the die and the top layer. This adhesive layer distance is 95% to 125% of the average particle size of the rigid microparticles. Prior to coating, the average particle size of the liquid metal droplets in the thermal interface material is larger than the average particle size of the rigid microparticles. Finally, the thermal interface material is cured to form a cured assembly.

8. The method as described in claim 6 or 7, wherein the distance between the adhesive layer formed between the grain and the top layer in the curing assembly is not greater than 150 micrometers.

9. The method as described in claim 6 or 7, wherein the average particle size of the rigid microparticles is in the range of 1 micrometer to 150 micrometers.

10. The method as described in claim 6 or 7, wherein the distance of the adhesive layer between the grain and the top layer is 100% to 110% of the average particle size of the rigid microparticles.

11. The method as described in claim 6 or 7, wherein the sphericity of the rigid microparticle is at least 0.

9.

12. The method as claimed in claim 6 or 7, wherein the rigid microparticles comprise iron, iron alloys, vanadium, vanadium alloys, niobium, niobium alloys, titanium, titanium alloys, copper, copper alloys, rigid polymers, glass, ceramics, or combinations thereof, and wherein the liquid metal droplets comprise gallium, gallium alloys, indium, indium alloys, tin, tin alloys, mercury, mercury alloys, or combinations thereof.

13. The method as described in claim 6 or 7, wherein the Young's modulus of the rigid microparticle is at least 100 MPa.

14. The method as described in claim 6 or 7, wherein the D90 of the rigid particle is not greater than 125% of the D50 of the rigid particle.

15. The method as described in claim 6 or 7, wherein the die includes a processor, and wherein the top layer includes a heat sink, an integrated heat sink, or a package.

16. The method as described in claim 6 or 7, wherein the liquid metal droplet is generally spherical before deposition and generally elliptical after the assembly is pressed, and the rigid particle is generally spherical before deposition and after the assembly is pressed.

17. The method as described in claim 6 or 7, wherein the thermal interface material comprises 30 vol% to 92 vol% of liquid metal droplets, 0.1 vol% to 5 vol% of rigid microparticles, and 7 vol% to 70 vol% of polymer.

18. The method as described in claim 6 or 7, wherein the liquid metal droplet and the rigid microparticle each have an average height ranging from 85% to 100% of the adhesive layer distance.

19. A circuit assembly manufactured by the method described in claim 6 or 7.

Images