RU2140335C1 - Manufacture of particles and products with specified properties - Google Patents

Abstract

FIELD: coated materials. SUBSTANCE: invention relates to articles and coatings designed such as to provide specified heat conductivity values and temperature expansion factors matching the same characteristics of those materials to which said articles and said coatings are to be attached. Desired characteristics are imparted to particles by coating them, after which multitude of coated particles are joined by compacting, isostatic pressing, or injection formation. Coating for each particle is applied at specified coating-to-particle volume ratio so that heat conductivity value and/or temperature expansion factor of coated particle differ from those characteristics of particle material and coating separately. As particle material, graphite, diamond, tungsten, or nickel-42 are used and, as coating material, copper. Desired characteristics of coated particles are obtained for temperature range 25 to 400 C. EFFECT: increased reliability of parameters' reproducibility of articles to be manufactured. 14 cl, 12 dwg

Description

 The invention relates to the design of the internal properties of particles, products made by combining particles, and coatings formed from particles, and more particularly, to the production of products and coatings designed to have pre-selected specific thermal conductivities and thermal expansion coefficients consistent with the same characteristics those materials to which these products and coatings are attached.

 According to Lucke's Rule of Mixtures, the internal physical properties (for example, thermal conductivity, thermal expansion coefficient) of heterogeneous products composed of at least two carefully mixed materials tend to vary approximately linearly depending on the ratio of the volume of one of these materials to the volume of the other material. For example, it can be expected that a heterogeneous product made up of a 50-50 volumetric mixture of one material that has a low coefficient of thermal expansion, and another material that has a high coefficient of thermal expansion, will have a coefficient of thermal expansion, which is the average of thermal expansion coefficients of both materials.

 In the known method for the production of heterogeneous products, a mixture of two metal powders, which have different specific thermal conductivities and thermal expansion coefficients, is compacted and sintered to produce the product. This product has a projected coefficient of thermal expansion, which approximately corresponds to the coefficient of thermal expansion of the object to which the product is intended to be attached, and the projected thermal conductivity.

 A technical solution is known in which in order to impart to the particles the desired value of the internal property (specific heat and / or coefficient of thermal expansion), which differs from the initial value of this property, the particles are coated, which has a different value of the said internal property. The value of the internal property of the coated particles depends on the ratio of volume, coating to volume of particles (US patent N 5184662, CL B 22 D 19/00, 1993).

 A coated particle is known comprising a discrete core particle containing a first material, said core particle having a first value of at least one internal property and a coating containing a second material and formed on a surface of said core particle, said coating having a second value of said at least at least one internal property, said second value different from said first value, the volume of said coating is relative to the volume said core particle, wherein said coated particle exhibits a third value of said at least one internal property, wherein said first and second materials and said volume of said coating with respect to said volume of said core particle exhibits such that said coated particle exhibits said the value of said at least one intrinsic property, said third value of said at least one intrinsic property being is a function of said first and second values and said volume, said third value of said at least one internal property is different from said first and second values (US Pat. Nos. 4,711,814, cl. B 05 D 5/12, 1987, N 5184662, cl. B 22 D 19/00, 1993).

 There is also known a technical solution for manufacturing an article of manufacture, comprising preforming a plurality of particles containing a first material with a first value of at least one internal property, forming a coating containing a second material with a second value of said at least one internal property, combining said coated particles so that said particles are joined together to form said article with a selected density, and in which discrete coating layers on the particles are practical are stored so that the second material and the first material practically do not mix and do not fuse, the selection of said first and second materials, carried out so that said article exhibits a third value of said at least one internal property, and a choice of said density to control said internal property as a function of temperature (US patent N 4894293, CL C 22 C 9/00, 1990).

 It is also known to manufacture a layered product with different values of the selected property of each layer for attaching to each other two objects with different values of this internal property (US patent N 4602956, CL C 22 C 29/12, 1986).

 Known technical solutions that characterize the method of manufacturing heterogeneous products, coating particles, manufacturing coated particles with a discrete core particle, an article made of a plurality of coated particles, and also a layered product are the closest to this group of inventions in terms of technical nature and the achieved result with their use. Solving the tasks assigned to them, they nevertheless do not provide for the creation of products with given parameters of specific thermal conductivity and coefficient of thermal expansion in given ranges. In addition, the manufactured products do not provide stable reproducibility of the mentioned parameters from sample to sample.

 The problem to which this group of inventions is directed is to create particles, products with predetermined parameters of specific thermal conductivity and coefficient of thermal expansion, while providing higher reliability of the reproducibility of these parameters for the created products.

 The mentioned technical result is achieved due to the proposed technology and the parameters and modes that accompany the manufacturing process.

 In one aspect, the invention defines a coating of a particle made of the first material with a second material such that the ratio of the volume of this coating to the volume of the particle itself is almost equal to the selected volume ratio. The first and second materials and the volume ratio are selected so as to cause the coated particle to exhibit at least one selected internal property, which is a function of the internal properties of the first and second materials. The first material is, for example, tungsten, molybdenum, graphite, silicon carbide or diamond. The second material is, for example, copper.

 In another aspect, the invention defines the manufacture of an article of particles controlled in such a way as to make the article have a selected density. Particles, at least part of which contains the first material and has surfaces on which a coating containing the second material is formed, are combined to cause them to join together to form an article of a selected density. The first and second materials are selected so that the product exhibits the selected internal property, and the density is selected so that this internal property exhibits the projected behavior as a function of temperature. For example, the degree of linearity of the coefficient of thermal expansion of the product formed from the combined particles depends on the density of the product. By selecting and controlling the density of the product, the behavior of the coefficient of thermal expansion as a function of temperature is controlled, and, in the general case, the choice of coefficient of thermal expansion is further refined.

 In another aspect, the invention defines the manufacture of an article of particles, wherein the article has two or more parts having different internal properties. The first plurality of particles contains at least one material, and the second plurality of particles contains at least one other material. The first plurality of particles and the second plurality of particles are combined to connect the first plurality of particles to each other to form a first part (eg, a layer) of an article, and the second plurality of particles are joined together to form a second part of an article; particles located near the interface between the first and second parts of the product are connected together. The first and second parts of the product exhibit different selected internal properties according to the compositions (and volume ratio) of the particles.

 For example, the first and second parts can have different coefficients of thermal expansion, and the product can be included directly between two objects with different coefficients of thermal expansion, which correspond to the coefficients of thermal expansion of these two parts. There is only one boundary (located on the interface between the two parts of the product) at which the thermal expansion coefficients do not coincide, and not a series of such boundaries located between successive layers of dissimilar products. The boundaries between the particles tend to absorb stress from thermal expansion, and therefore, cracking or delamination at the joint between the two parts is prevented.

 Numerous features, objects, and advantages of the invention will become clearer from the following detailed description and from the claims.

 FIG. 1 shows a cross section of a coated particle of the invention.

 FIG. 2 illustrates the combination of coated particles of FIG. 1 through compaction.

 FIG. 3 shows a layer of coated particles of FIG. 1, applied to the surface of the product.

 FIG. 4 illustrates an electronics enclosure that includes a combination of structural, thermal, and ground plates made of coated particles of FIG. 1, and lead frames made of the coated particles of FIG. 1.

 FIG. 5 is a diagram illustrating product expansion as a function of temperature at densities of 90%, 95%, and 100%.

 FIG. 6 illustrates the combination of two separate layers of coated particles of FIG. 1 through compaction.

 FIG. 7 depicts a hybrid electronics housing used to accommodate integrated circuits in it, which is made of coated particles of FIG. 1.

 FIG. 8 shows an electronics housing with a low-temperature ceramic substrate that is calcined when it supports a pre-sintered combination of structural, thermal, and ground plates made of coated particles of FIG. 1.

 FIG. 9 shows a high-power semiconductor compression module comprising a semiconductor device that is pressed under pressure to a heat sink formed from coated particles of FIG. 1.

 FIG. 10 shows a cross section of a coated particle according to the invention, the particle having a thin boundary precoating.

 FIG. 11 shows the coated particles of FIG. 10 electrolytically deposited on the product together with the matrix material.

 FIG. 12 shows precoated particles electrolytically deposited onto an article in conjunction with matrix material.

 In the drawings, and more specifically in FIG. 1, particle 12, which may have only a few microns in diameter and which includes elemental metal, metal alloy or non-metal, is coated with a coating of 14 of elemental metal, metal alloy or non-metal to form coated particle 10. Coated particle 10 exhibits projected internal physical properties (e.g. thermal conductivity or coefficient of thermal expansion) and / or internal mechanical properties (e.g. tensile strength). The intrinsic physical properties (but not intrinsic mechanical properties) of the coated particle 10 tend to behave in accordance with the rule of Lucke mixtures, according to which the intrinsic physical properties vary approximately linearly with the ratio of the coating volume 14 to the particle volume 12. The mechanical properties vary non-linearly with the ratio of the coating volume 14 to the particle volume 12.

 The coating 14 is adhered to the particle 12 by, for example, deposition by chemical reduction (the method discussed below). The internal properties of the coated particle 10 are designed by controlling the ratio of the coating volume 14 to the volume of the particle 12, which can be achieved in two ways: 1) controlling the size of the particle 12, or 2) controlling the thickness of the coating 14.

Particle 12 includes, for example, elemental tungsten, coating 14 includes elemental copper, and the ratio of the volumes of copper to tungsten is 27: 73%. Copper has a high thermal conductivity of approximately 391 W / m • deg K (watts per meter and Kelvin) and a relatively high coefficient of thermal expansion of approximately 17.5 mil. parts / deg C (ppm per degree Celsius) in the temperature range of 25 to 400 ^° C., while tungsten has a relatively low thermal conductivity of approximately 164 W / m • deg K and a relatively low coefficient of thermal expansion of approximately 4.5 mil. / deg C in the range from 25 to 400 ^o C. The coated copper tungsten particle 10 has a thermal conductivity of approximately 226 W / m • ° K at 25 ^o C (intermediate between the high thermal conductivity of copper and the lower thermal conductivity of tungsten) and zaproekt Rowan thermal expansion coefficient of about 8.2 mil.chastey / deg K (intermediate between the low coefficient of thermal expansion of tungsten and the higher coefficient of thermal expansion of copper) in the range from 25 to 400 ^o C.

 In FIG. 2 shows a stamping device 16 comprising a punch 18 and a mold 20 that is used to combine coated particles 10 into article 22 by sealing (wherein coated particles 10 have the designed properties as described in connection with FIG. 1). The densified article 22 is sintered in the solid state (sintered at a temperature below the melting point of the particles and the melting point of the coatings of these particles) or, alternatively, sintered in the liquid phase (sintered at a temperature above the melting point of the coatings, but below the melting point of the particles). Melting causes the formation of boundaries between particles to obtain a heterogeneous product. Coating the particles thus serves as a “matrix material” (a material that holds the particles together to form an article).

 The article 22 has projected internal physical properties (for example, thermal conductivity and / or coefficient of thermal expansion) and / or internal mechanical properties (for example, tensile strength) corresponding to the properties of the coated particles 10 of which the product is made. The designed internal properties of the coated particles 10 are manifested with a high degree of uniformity and isotropy throughout the product 22 because each particle 10 has a uniform coating, and because there is no inherent randomness in the distribution of different materials or separation between different materials within the product 22. Thus, the internal the properties of the article 22 are designed at the "particle level", and not at the "product level". Product 22 is, for example, a thermal and structural plate for an electronics housing, wherein the thermal and structural plate is designed to have a coefficient of thermal expansion that matches the same coefficient of the object to which it is attached, and is designed to have high thermal conductivity, as described below in connection with FIG. 4.

 Copper-coated tungsten particles, for example, having a ratio of copper to tungsten volumes of 27: 73%, are compacted in press 16 at a force of 200 tons per square inch of surface area to achieve full density (above a density of approximately 90%), and the densified coated particles are sintered into solid state in a hydrogen atmosphere at 1950 degrees Fahrenheit for about half an hour.

 Coated particles 10 can be combined not only as described above, but these coated particles can also be applied to objects as coatings. In FIG. 3 shows a coating 28 of coated particles 10 with the designed properties. Coating 28 is applied to the surface of a product 30 of metal, metal alloy or non-metal through a mask 29 for coating. Product 30 may alternatively be a product that is itself formed from coated particles by any of the methods discussed above. During the application process, coated particles, for example, copper-coated tungsten particles with a ratio of copper to tungsten volumes of 27: 73%, are placed in a liquid and the coating is formed from particles, for example, beryllium oxide, using one of the application methods described in detail below. Thus, it is possible to create a coating directly on the product without having to apply a connection between the coating and the product.

 Coating 28 has projected internal physical properties (e.g., thermal conductivity, coefficient of thermal expansion) and / or internal mechanical properties (e.g., tensile strength) that match the properties of the coated particles of which these coatings are made. The designed internal properties of the coated particles are manifested with a high degree of uniformity and isotropy throughout the coating 28 because each particle is coated uniformly, and because there is no inherent randomness in the distribution of different materials or separation between different materials within the coating 28. Thus, the internal properties of the coating 28 are designed at the “particle level” rather than the “coating level”. Note, however, that the application method described above can also be implemented when coating 28 does not contain coated particles, but instead consists of a mixture of different particles selected from two different materials in a suitable volume ratio.

 In FIG. 4 shows an electronics housing 32 that includes semiconductor devices 34 mounted on a substrate 35, which substrate 35 is supported by a combined structural, thermal, and ground plate 36 formed from coated particles. Semiconductor devices 34 are, for example, high-power solid-state switching devices (such as those that can be included in the circuit of a vehicle with an electric motor) and generate significant amounts of heat during operation. The substrate 35, to which the semiconductor devices 34 are attached by adhesive bonding, diffusion bonding, hard or soft solder or soldering, is formed from a material selected so that its coefficient of thermal expansion approximately matches the same coefficient of semiconductor devices 34, as is known from the level techniques to facilitate the attachment of semiconductor devices 34 to the substrate 35. The structural plate 36 is made according to the present invention from coated particles. The particle material, the coating material, and the ratio of the volumes of the coating material to the particle material are selected so that the structural plate 36 has a high thermal conductivity (to enable it to work as a heat sink and a thermal plate) and at the same time has a coefficient of thermal expansion that practically coincides with the coefficient of thermal substrate expansion 35. Both the thermal conductivity and the coefficient of thermal expansion are highly uniform and isotropic throughout the structural plate 36.

The substrate 35 is formed, for example, of aluminum nitride with a coefficient of thermal expansion of approximately 4.4 mil.parts / deg ^o C in the range from 25 to 400 ^o C. The structural plate 36 is made of copper-coated graphite particles with a ratio of copper to graphite 24 : 76%. This volume ratio provides a thermal conductivity of approximately 325 W / m • deg K and a thermal expansion coefficient of approximately 4.3 ppm / deg C (25 to 400 ^° C), which exactly matches this coefficient for the aluminum nitride substrate 35. The copper matrix material provides high tensile strength (internal mechanical property) in the structural plate 36. Alternatively, the structural plate 36 is made of copper coated diamond particles with a ratio of 20: 80% copper to diamond. This volume ratio provides a thermal conductivity of approximately 781 W / m • deg K and a thermal expansion coefficient of approximately 4.8 mil. parts / city C (25 to 400 ^o C).

Alternatively, the substrate 35 is formed from beryllium oxide (BeO) with a coefficient of thermal expansion of approximately 7.6 ppm / deg C (25 to 400 ^° C). Structural plate 36 is made of copper-coated graphite particles with a ratio of copper to graphite volumes of 42: 58%. This volume ratio provides a thermal conductivity of approximately 380 W / m • deg K and a coefficient of thermal expansion of approximately 7.6 ppm / deg C (25 to 400 ^° C.), which exactly matches the same coefficient of the beryllium oxide substrate 35. Alternatively, the structural plate 36 is made of copper coated diamond particles with a ratio of copper to diamond volume of 37: 63%. This volume ratio provides a thermal conductivity of approximately 698 V / m • deg K and a thermal expansion coefficient of approximately 7.6 mil. parts / city C (25 to 400 ^o C). Alternatively, the structural plate 36 is made of copper-coated tungsten particles with a ratio of copper to tungsten volumes of approximately 27: 73%. This volume ratio provides a thermal conductivity of approximately 226 W / m • deg K and a coefficient of thermal expansion of approximately 8.2 ppm / deg C (25 to 400 ^° C.).

 The structural plate 36 is attached to the substrate 35 as follows. A thin layer of coated particles is first deposited on the lower surface of the substrate 35, as shown in FIG. 3, in accordance with the method described below. Then, the structural plate 36, which is sealed (as described above for FIG. 2) but not yet sintered, is brought into contact with the deposition surface of the substrate 35. This structure is then sintered to force the substrate 35 and the structural plate 36 to join together into a single construction. Alternatively, the structural plate 36 is bonded to the substrate 35 by soldering, hard or soft solder, diffusion or adhesive bonding.

The lead frames 38 to which the semiconductor devices 34 are attached via wire connections 40 that transmit power, ground, input and output signals to and from the semiconductor devices 34 are also made of coated particles according to the present invention in order to have a coefficient of thermal expansion substantially coinciding with thermal expansion coefficient of the substrate 35. The substrate 35 is formed, for example, of beryllium oxide (BeO) with a thermal expansion coefficient of approximately 7.6 mils. parts / degree C (from 25 to 400 ^o C), and the output frame 38 is made of copper-coated nickel particles 42 (nickel 42 is an iron-nickel alloy) with a ratio of copper to nickel 42 in 20: 80%, thermal conductivity of approximately 86.78 W / m • deg K and a coefficient of thermal expansion of approximately 8.1 mil.parts / deg C (25 to 400 ^o C). Note that the copper-coated nickel 42 should not have such a high thermal conductivity as the copper-coated graphite used in the structural plate 36, because the lead frames 38 are not designed to perform the functions of heat removal. Alternatively, however, the lead frames 38 may be made of the same coated particles from which the structural plate 36 is made. The lead frames 38 are applied via a coating mask directly to the upper surface of the substrate 35 according to the method described above in connection with FIG. 3. In one embodiment, the lead frames 38 are sintered to ensure that the lead frames reach the desired density.

 Even with given large power levels, thermal densities and operating frequencies that are characteristic of new powerful electronic equipment, and with large and rapid changes in temperature that usually occur during operation of semiconductor devices 34, it is unlikely that cracks and delaminations will appear in connections of the substrate 35 and the output frames 38 and between the substrate 35 and the structural plate 36, due to the practical coincidence of the coefficients of thermal expansion in the connection and due to uniformity and isotropy, by which the thermal conductivity and thermal expansion coefficients appear in the entire structural plate 36 and in all the output frames 38. As a result, the entire housing structure 32 has a long service life.

 The designed internal properties of the product manufactured according to the method described above are not only a function of the materials selected for particles and particle coatings and a function of the ratio of the volumes of the coating material to the material from which these particles are formed, but, in addition, on the behavior of these internal the properties of such products depending on temperature (for example, the degree of linearity of the coefficient of thermal expansion depending on temperature) affect the density of the product. Thus, by controlling the density of such a product, it is possible to approximate the behavior of the coefficient of thermal expansion of the product depending on temperature to the coefficient of thermal expansion of ceramics (which behaves non-linearly depending on temperature) in the critical temperature ranges of processing.

FIG. 5 is a graph of thermal expansion in parts per million as a function of temperature for articles formed from copper-coated tungsten particles with a ratio of copper to tungsten volumes of 27: 73% (15% copper to 85% tungsten by weight) at densities of about 100% (theoretical density) , 95% and 90%, and for two ceramic materials (BeO and Al ₂ O ₃ ), with which the nature of the expansion of the product can approximately coincide in the critical temperature ranges of processing by choosing the appropriate density. Note that the degree to which the product expands (i.e., the coefficient of thermal expansion) decreases with decreasing density. Thus, it is possible to choose the behavior of the coefficient of thermal expansion (or the behavior of other properties, such as thermal conductivity) depending on the temperature, and in general, it is thereby possible to further refine the physical properties by choosing the density at which the product is manufactured. Note that the properties of products made from uncoated particles can also be controlled by selecting the densities at which these products are made.

Coating Methods
We turn first to the methods of coating the particles themselves. Then, we consider methods of applying coatings of coated particles to articles.

 In FIG. 1, coating 14 is applied to particle 12 using an appropriate chemical reduction (autocatalytic deposition) deposition process. Particles to be coated are placed in a chemical reduction bath, which contains an aqueous solution of metal ions, one or more chemical reducing agents, a catalyst, one or more complexing agents and one or more bath anticoagulants. Metal ions are autocatalytically or chemically reduced to metal using a reducing agent or reducing agents, while the reducing agent or reducing agents act as electron donors, and metal ions act as electron acceptors. The catalyst accelerates the chemical reduction reaction. The complexing reagent or reagents are used to control the pH of the solution and to control the amount of “free” metal ions available for dissolution. Anticoagulants act as catalytic inhibitors to inhibit the possible spontaneous decomposition of the bath. In one embodiment, for example, the particles to be applied are particles of graphite, diamond or silicon carbide, copper ions are supplied with aqueous copper sulfate, the reducing agent is formaldehyde, the catalyst is palladium, the complexing reagent is one or more of the group consisting of: Rochelle salt, ethylene diamine tartrate (EDTA), ammonium hydroxide, pyridin-3-sulfonic acid and / or potassium tartrate, and the anticoagulant is one or more of the group consisting of thiodiglycolic acid, MBT, thiourea, sodium cyanide th and / or vanadium oxide.

 Precipitation by chemical reduction creates either a mechanical bond or a chemical bond between coating 14 and particle 12. This bond, as a rule (but not always), will be mechanical if either coating 14 or particle 12 is non-metal, and will usually be chemical, if both coating 14 and particle 12 are metals.

 Alternative methods for coating particles include electrolytic deposition, sputtering from a gaseous medium, and sputtering from a liquid medium.

 As shown in FIG. 10, in some embodiments, in which the coating 14 would form only a mechanical bond with the particle 12, if the coating 14 were applied directly to the particle by deposition by chemical reduction, the particle 12 is pre-coated with an ultrathin layer 68 (in the drawings, the thickness is increased) of the pre-coating material, and then a coating 14. A pre-coating (boundary coating) 68 is firmly bonded to the particle 12 and the coating 14, creating a strong, fracture-resistant chemically bonded coated particle 10. For example, if the particle 12 is graphite or diamond, and coating 14 is copper, coating 14 would form a mechanical bond with graphite or diamond if coating 14 were applied directly to graphite or diamond. Instead, particle 12 is first coated with a pre-coating 68 of a metal such as chromium or a cobalt-tungsten alloy with a thickness ranging from 200 to several thousand angstroms, with the pre-coating 68 forming a cohesive composition with a particle 12 at the interface between the pre-coating 68 and particle 12. Then, the coating 14 is applied to the chrome or cobalt-tungsten pre-coating 68, while the pre-coating 68 forms a metallurgical bond with the coating 14. The pre-coating is practical It does not affect the thermal conductivity or coefficient of thermal expansion of the coated particle 10, because this preliminary coating is ultrafine. In one embodiment, a small controlled quantity of a palladium or boron catalyst is deposited together with a cobalt-tungsten pre-coating material, this catalyst serving to accelerate a chemical reduction reaction by which a copper coating 14 is deposited on a cobalt-tungsten pre-coating 68.

 The precoating is also used when the coating 14 reacts with the particle 12, is corroded by it or is destroyed from it in some other way, or vice versa. For example, if particle 12 is graphite or diamond, and coating 14 is aluminum, then highly reagent aluminum would dissolve graphite or diamond if coating 14 were applied directly to particle 12. Instead, a thin layer of metal 68 was first deposited on particle 12, such like chromium or cobalt-tungsten, and then a pre-coating 68 is coated 14 to form a coated particle 10. This pre-coating 68 forms a cohesive bond with a graphite or diamond particle 12, thereby protecting particle 12 from an aluminum matrix Nogo material. Thus, pre-coating 68 allows the release of articles from coated particles when the particles and their coatings would otherwise seek to react with each other.

 Pre-coating 68 also makes it possible to mix particles coated with a thin layer of pre-coating (but without coating 14) into the molten alloy, where the particles and alloy would otherwise tend to react with each other. For example, graphite particles coated with a thin layer of cobalt-tungsten pre-coating are added to an aluminum alloy in vacuum, and this alloy containing particles is cast under pressure or extruded into a mesh (or approximately mesh) product, which is used as one thermal management product for electronics (e.g. heat sink and heat plate). The cobalt-tungsten precoat forms a cohesive bond with graphite particles and forms a metallurgical bond with an aluminum alloy. The ratio of the volumes of particles in the alloy material (particles are up to about 50% by volume) is selected so as to induce physical properties in the resulting product for the designed properties, such as thermal conductivity or coefficient of thermal expansion. Alternatively, pre-coated particles are added to the alloy to mechanically harden the resulting article or affect its weight.

 Let us now consider the methods of applying coatings of coated particles to articles. Turning again to FIG. 3, where the article 30 is coated with 28 of the coated particles 10 (the article 30 is, for example, a substrate on which the coating 28 forms, for example, an exit frame). If the article 30 is metallic or from a metal alloy, then the coating 28 is electrolytically deposited directly onto the article 30 by the method described below. If the article 30 is non-conductive (eg, ceramic), then the article 30 is first coated with a thin coating of a conductive material, such as a matrix material, with which the coated particles 10 are coated, by deposition by chemical reduction (autocatalytic reduction). A chemical reduction bath contains an aqueous solution containing metal ions, one or more chemical reducing agents, a catalyst, one or more complexing agents, and one or more bath coagulators, as described above. Metal ions are autocatalytically and chemically reduced using a reducing agent or reducing agents that cause the metal to deposit on the article 30. Alternatively, particles (uncoated, precoated or coated) are placed in an aqueous solution and the particles are coated with metal and simultaneously coated with metal, the particles are deposited on article 30. Due to the fact that deposition by chemical reduction is slower than electrolytic deposition, coated particles 10 are electrolytically deposited on a thin conducting layer (using the method described below) as soon as this thin conductive layer is formed, thereby forming a coating 28.

 According to FIG. 11, coating 28 is applied to a conductive article 30 (or a non-conductive article metallized with a thin conductive layer, as described above) by using electrolytic co-deposition of coated particles 10 and matrix material (the material from which coatings 14 of coated particles 10 are formed) onto article 10 As coated particles 10 (for example, graphite particles 12 coated with a thin intermediate pre-coating 68 of chromium or cobalt-tungsten, on which a copper coating 14 is applied) are deposited on the product 30, matrix material is simultaneously deposited around the coated particles to fill the gaps between the coated particles, forming a coating 28.

 As shown in FIG. 12, in an alternative electroplating method, the matrix material and particles 12 (which are coated with a precoat 68, as described above, but which are not yet coated with a matrix material) are deposited together on the article 30. As particles 12 are deposited on the article 30, these the particles are simultaneously coated with a matrix material. To form a coating 28. For example, particles 12 are graphite, the matrix material is copper, and the pre-coating material is a metal such as chromium or cobalt-tungsten.

 Alternatively, a coating 28 is formed on the article 30 by sputtering from the gaseous phase or by spraying from the liquid phase the coated particles 10 onto the article. Coating 28 is then sintered, after which coating 28 exhibits its selected internal property or selected internal properties.

Other accomplishments
Graphite or diamond are good materials from which particles 12 are formed when the manufactured product or coating must have a low coefficient of thermal expansion and high thermal conductivity, because these materials not only have a low coefficient of thermal expansion (like tungsten or molybdenum), but also have a relatively high thermal conductivity (unlike tungsten and molybdenum). Therefore, these materials have the advantage that they have no harmful side effect of reducing the thermal conductivity of the coated particles, as well as products and coatings formed from these coated particles.

 When a manufactured product or coating must have a coefficient of thermal expansion that matches the coefficient of a silicon semiconductor or integrated device to which this product or coating is directly attached (silicon has a coefficient of thermal expansion of approximately 4.2 ppm / degree C), this product or the coating contains, for example, copper-coated diamond particles with a ratio of copper to diamond volumes of approximately 20: 80% or copper-coated graphite particles with a ratio of copper to diamond volumes um, about 24: 76%.

 It is possible to design many internal properties other than specific thermal conductivity or coefficient of thermal expansion. For example, you can design the electrical conductivity of the product in combination with the design of other internal properties. Thus, in one embodiment, the choice between using graphite particles (which are electrically conductive) and diamond particles (which are electrical insulators) is based on the desired electrical conductivity of the article.

 As shown in FIG. 2, particles 10 do not need to consist entirely of coated particles. Alternatively, a mixture of coated particles combined with other particles (for example, copper coated tungsten particles can be combined with copper particles) can be thoroughly mixed and then densified to form article 22 with internal properties that are a function of volume ratios of all materials in the mixture, moreover article 22 exhibits intrinsic properties isotropically. Alternatively, coated particles are combined with materials that exhibit one or more internal properties anisotropically, which, in turn, causes the product to exhibit one or more internal properties anisotropically. For example, coated particles are mixed with crystalline materials having properties that are different in different directions, and these crystalline materials are mixed with coated particles so that the crystalline materials tend to orient in the general direction. In another example, coated particles are mixed with carbon fibers, and these carbon fibers tend to orient in a general direction. Carbon fibers provide tensile strength that varies with direction.

 Alternative methods for manufacturing coated particle products include metal injection molding, hipping, cipping, isostatic forging, hot or cold forging, and hot or cold rolling compaction (which compacts the coated coated particles ) and pressure pressing.

 If the coated particles 22 are densified to a density approaching “full density” (the density at which the densified coated particles have a “level 2” or “level 3” or “non-interconnected” porosity, that is, a porosity that does not provide interconnect passages, passing from one side of the product to the other), the sintering process does not increase the density and does not change the size of the product. The density of the product, and thus the final dimensions of the product can be precisely controlled during compaction. It is especially advisable to compact to full density when the particles contain certain non-metals, such as graphite, because, for example, copper-coated graphite particles can be compacted to full density at a relatively low pressure of 60 to 80 tons per square inch. When the particles are formed from metal or a metal alloy (whether the particles are coated with metal or not coated), pressures of 80 to 200 tons per square inch are usually required to compact the particles to full density.

 In FIG. 6, an injection molding apparatus 16 is shown including a punch 18 and a mold 20 that is used to combine two different layers of particles 24 and 26 by compaction to obtain an article 25 with internal properties that vary from layer to layer. Layers 24 and 26 are composed of particles composed of different materials or having different ratios of volumes of materials from which these particles are formed. The particles are optionally coated particles. Particles are introduced into mold 20 in layers 24 and 26, compacted to a selected density to give temperature-dependent internal properties (e.g., thermal conductivity or coefficient of thermal expansion), as discussed above in connection with FIG. 5, and sinter in a hydrogen atmosphere for about half an hour. This sintering causes the particles of the layers 24 and 26 to bond at the interface between the two layers to obtain a single layered product.

 For example, layer 24 contains copper-coated tungsten particles with a ratio of copper to tungsten volumes of 27: 73%, and layer 26 contains elemental copper particles. Layer 24 after compaction has a thermal conductivity of approximately 225.78 W / m • deg K and a thermal expansion coefficient of approximately 8.28 ppm / deg C. Layer 26 after compaction has a thermal conductivity of approximately 390 W / m • deg K and thermal coefficient an expansion of approximately 18.04 ppm / deg C. A laminated article 25 is inserted directly between two objects with different thermal expansion coefficients that match the thermal expansion coefficients of layers 24 and 26. For example, layer 24 is attached to erillium ceramics, and layer 26 diffusely binds to a copper heat sink.

Alternatively, layer 24 includes copper-coated diamond with a ratio of copper to diamond volumes of 20: 80%, and layer 26 consists of copper-coated graphite with a ratio of copper to graphite volumes of 24: 76%. After compaction, the silicon crystal is attached to the side of the product 25, which corresponds to layer 26, and the aluminum nitride substrate is attached to the other side of the product 25, which corresponds to layer 24. Layer 24 has a thermal conductivity of approximately 781 W / m • deg K and thermal expansion coefficient approximately 4.8 ppm / degree C (25 to 400 ^° C.), which practically coincides with the thermal expansion coefficient of the aluminum nitride substrate. Layer 26 has a thermal conductivity of approximately 379 W / m • deg K and a coefficient of thermal expansion of approximately 4.3 mil. parts / degree C (from 25 to 400 ^o C), which practically coincides with the coefficient of thermal expansion of the silicon crystal. Layer 24 is alternatively designed to adhere to a beryllium oxide substrate, with layer 24 having a copper to diamond volume ratio of 37: 63%, thermal conductivity of approximately 698 W / m · deg K, and thermal expansion coefficient of approximately 7.6 ppm. / city C (from 25 to 400 ^o C), which practically coincides with the coefficient of thermal expansion of the substrate of beryllium oxide.

 Thus, the laminated product 25 is included directly between two objects with different coefficients of thermal expansion. The boundary between the different coefficients of thermal expansion is obtained inside the laminated product 25, and not at one or more interfaces between the surfaces of the product and other devices. In addition, there is only one boundary (located between two layers inside the layered, separate product 25), on which there is a mismatch of the thermal expansion coefficients, and not a series of such boundaries located between successive layers of dissimilar products. Since copper bonds between particles are capable of being deformed in a cold state, these copper bonds tend to absorb thermal expansion stress and, as a result, there is no cracking or delamination in the connection between the two layers. In addition, since the bonds are malleable and since all bonds are formed from the same material (all bonds are copper to copper), these bonds tend to absorb stresses in the same way, as a result of which the product does not tend to bend in an arcuate or wave-like fashion with large changes in temperature. In an alternative embodiment, the article 25 has more than two layers, and therefore there is more than one inner boundary at which the thermal expansion coefficients do not match. This mismatch on each boundary is less than the mismatch that occurs on a single border within the laminate 25.

 In FIG. 7 shows a hybrid electronics case 72 with sides 48, a base 46, and a cover 50, which is used as a case for semiconductor integrated circuits and other electronic devices. Hybrid electronics housings are generally made of an iron-nickel alloy known as KOVAR having a coefficient of thermal expansion that is approximately equal to the same coefficient of glass insulators used to isolate the outlet holes 44 from the conductive housing of KOVAR. The application of the invention to the manufacture of hybrid housing 72 depends on whether conventional glass insulation is used to insulate the outlet openings 44, or whether other insulation is used.

If conventional glass insulation is used, then the goal is to produce a hybrid casing with a coefficient of thermal expansion that practically coincides with the same coefficient for KOVAR, but with a higher thermal conductivity than KOVAR. For example, a hybrid housing can be made of iron-coated graphite particles with a ratio of iron to graphite volumes of 26: 74% and a thermal expansion coefficient of approximately 3.2 mils. parts / deg C (from 25 to 400 ^o C), almost coinciding with the same coefficient in KOVAR, and the specific thermal conductivity of approximately 295 W / m • deg K, which is much higher than the thermal conductivity of KOVAR (approximately 11 W / m • deg TO).

If the glass for insulating the outlet openings 44 is replaced by low-temperature glass ceramics, then the hybrid housing 72 is made, for example, of copper-coated graphite particles with a ratio of copper to graphite volumes of 39: 61%. This volume ratio provides a high thermal conductivity of approximately 379 W / m • deg K and a coefficient of thermal expansion of approximately 6.9 mil. Parts / deg C (25 - 400 ^o C), which is designed to practically coincide with the coefficient of thermal expansion of glass ceramic material used to isolate the outlet openings 44.

 The coefficient of thermal expansion in the entire hybrid housing 72 of the electronics is highly uniform. Since the base 46 and the sides 48 of the hybrid electronics case 72 can be fabricated together as a single unit (whereas in the KOVAR case, the base 46 and sides 48 are usually processed separately from whole pieces of KOVAR material), the case 72 can be manufactured without cost due to the cost of the machine processing or soldering the base 46 and the sides 48, although the cover 50 should be attached to the sides 48 by soldering after the integrated circuit is placed inside the case.

In FIG. 8 shows an electronics case 52 with a set of integrated circuits 54 mounted on a substrate 56 of low-temperature glass ceramics supported by a combined structural, thermal and grounding plate 58. The structural plate 58 is made of copper-coated graphite particles with a ratio of copper to graphite volumes of 39: 61%. This volume ratio provides a high thermal conductivity of approximately 379 W / m • deg K, high tensile strength and a coefficient of thermal expansion of approximately 6.9 ppm / deg C (25 to 400 ^o C), which practically coincides with the coefficient of thermal expansion ceramic substrate 56. This coefficient of thermal expansion is highly uniform and isotropic throughout the structural plate 58. The copper-coated graphite particles of which the structural plate 58 is made are compacted to a density selected so that the expansion pattern of the structural plate 58 practically coincides with the nonlinear expansion pattern of the ceramic substrate 56. Then, the coated particles are sintered. The immature ceramic substrate 56 (the ceramic substrate that has not yet been calcined) is then laminated onto the structural plate 58, after which the immature ceramic substrate 56 is calcined. The ceramic substrate 56 has a calcination temperature below the temperature at which the structural plate 58 is sintered in the solid state. As a result, when the ceramic substrate 56 is calcined when installed on the structural plate 58, the particle coatings in the structural plate do not melt. The pre-sintered structural plate 58 provides high production yields by obtaining a structural platform on which it is possible to work with thin brittle layers of ceramic and / or glass without breakage during the entire production cycle.

In FIG. 9 shows a high-power semiconductor compression module 60, which includes a silicon semiconductor device 62, for example, a silicon switch about half a dollar or a silver dollar in size and having a thermal expansion coefficient of about 4.3. The semiconductor device 62 is pressed with a force of approximately 5,000 pounds to the heat sink 64 formed from the copper-coated graphite particles according to the invention. The semiconductor device 62 has a molybdenum back surface with a low coefficient of thermal expansion, which is adjacent to the rear of the aluminum heat sink 66 (which is not made of particles). A heat sink 64, having a ratio of copper to graphite volumes of 24: 76%, is designed to have a high thermal conductivity of 379 W / m • deg K and a thermal expansion coefficient of 4.3 mil parts / deg C (25 to 400 ^o C), which practically coincides with the coefficient of thermal expansion of semiconductor device 62, and this coefficient of thermal expansion is highly uniform throughout the heat sink 64. Designing the coefficient of thermal expansion of heat sink 64 extends the life of the semiconductor device 62 by preventing scratches on the semiconductor device 62 due to pressing interacting with the heat sink 64, which can cause a short circuit.

 New and improved device and methods for designing the internal properties of products manufactured by combining particles are considered. Obviously, those skilled in the art can now make numerous uses and modifications of the specific applications described herein and departing from them without departing from the inventive concept. For example, the principles of the invention can be applied in other fields, such as firearms and military equipment, to ensure that shells and shells have the same coefficients of thermal expansion as the guns from which they are fired, which can be coated from the inside with ceramic material . Therefore, the invention should be construed as encompassing each and every new feature and new combination of features presented or contained in the device and methods discussed herein, and limited solely by the spirit and scope of the attached claims.

Claims (14)

1. The method of imparting to the particles the desired value of thermal conductivity and / or coefficient of thermal expansion (CTE) by coating them, which consists in the fact that each particle is coated in a certain volume relative to the volume of the particle so that the obtained values of thermal conductivity and / or KTP of the coated particle differed from the values of these properties for the materials of the particles and the coating, characterized in that the material of the coated particle is graphite, diamond, tungsten or and nickel-42, and copper as the coating material and when the percentage ratio of copper to graphite volumes is 24: 76, 39: 61 and 42: 58, the values of the thermal conductivity (W / (m • K)) and KTP in the temperature range of 25 - 400 ^o C (ppm / ^o C), respectively 325 and 4.3; 379 and 6.9; 380 and 7.6, or when the percentage ratio of copper to diamond volumes is 20: 80 and 37: 63, the specific thermal conductivity and KTE are obtained for the coated particles, respectively, 781 and 4.8, 698 and 7.6, or when the percentage ratio of copper to tungsten volumes 27: 73 for a coated particle, the thermal conductivity of 226 and KTP of 8.2 is obtained, or with a percentage ratio of copper to nickel-42 of 20: 80, the thermal conductivity of the coated particle is 86.78 and KTR of 8.1. 2. A coated particle containing a discrete core particle and a coating formed on its surface to give the particle the desired value of thermal conductivity and / or KTP, characterized in that the core particle is formed of graphite, diamond, tungsten or nickel-42, and the coating is made of copper and with a percentage ratio of copper to graphite volumes of 24: 76, 39: 61 and 42: 58, the coated particle has the values of specific thermal conductivity (W / (m • K)) and KTP in the temperature range of 25 - 400 ^o C (ppm / ^o C), respectively 325 and 4.3; 379 and 6.9; 380 and 7.6, or with a percentage ratio of copper to diamond volumes of 20: 80 and 37: 63, the coated particle has thermal conductivity and KTP of 781 and 4.8, 698 and 7.6, respectively, or with a percentage ratio of copper to tungsten volumes 27 : 73 coated particle has a thermal conductivity of 226 and KTP 8.2, or with a percentage ratio of copper to nickel-42 of 20: 80 the coated particle has a thermal conductivity of 86.78 and KTP 8.1.  3. The coated particle according to claim 2, characterized in that a thin preliminary coating is applied to the core of graphite or diamond, which does not affect the thermal expansion coefficient and thermal conductivity of the coated particle.  4. The coated particle according to claim 3, characterized in that chrome or cobalt-tungsten is used as the pre-coating material. 5. The product is made of many coated particles with the desired values of thermal conductivity and KTP, which are combined by compaction to the selected density followed by sintering in the solid phase, characterized in that the product is formed from copper-coated particles of graphite, diamond, tungsten or nickel at -42 and has a volume percentage of copper to graphite of 24: 76, 39: 61 and 42: 58 values of thermal conductivity (W / (m • K)) and the CTE over a temperature range of 25 - 400 ^o C (mln.chastey / ^o C), respectively 325 and 4.3, 379 and 6.9, 380 and 7.6, and whether at a percentage ratio of copper to diamond volumes of 20: 80 and 37: 63 the product has a specific thermal conductivity and KTP of 781 and 4.8, 698 and 7.6, respectively, or at a percentage ratio of copper to tungsten volume of 27: 73 the product has a specific thermal conductivity of 226 and KTP 8.2, or at a percentage of copper to nickel-42 volumes of 20: 80, the product has a thermal conductivity of 86.78 and KTP 8.1.  6. The product according to claim 5, characterized in that the particles are joined together by injection molding.  7. The product according to claim 5, characterized in that the combination of particles among themselves is carried out by isostatic pressing.  8. The product according to claim 5, characterized in that it is made in the form of a structural plate having the form for supporting the substrate on which at least one semiconductor device is mounted, wherein the KTP of the plate practically coincides with the KTP of the substrate.  9. The product according to claim 5, characterized in that it is made in the form of output frames mounted on the substrate, to which semiconductor devices are attached via wires that transmit power, ground, input and output signals to and from semiconductor devices, while KTP output The frame almost coincides with the KTP of the substrate.  10. The product according to claim 5, characterized in that it is made in the form of a housing designed to accommodate a predominantly integrated circuit, wherein the KTR of the housing coincides with the KTR of the material used to seal the outlet openings in the housing.  11. The product according to claim 5, characterized in that it is made in the form of a heat sink having the form for pressing against a semiconductor device, while the KTR of the heat sink practically coincides with the KTR of the device. 12. A layered product in which the layers are made of coated particles with different KTP values for each layer, designed primarily to connect two objects with different KTP to each other, characterized in that the product is designed to connect a silicon crystal and a substrate, the layer designed for attachment to a silicon crystal, contains copper-coated graphite particles with a percentage ratio of copper to graphite volumes of 24: 76 and has a specific thermal conductivity of 325 W / (m • K) and a CTE of 4.3 million parts / ^o C (25 - 400 ^o C), which coincides with the CTE of the silicon crystal, and the other layer intended for attachment to the substrate contains copper coated diamond particles and has a CTE that coincides with the CTE of the substrate. 13. The layered product according to item 12, characterized in that the layer intended for attachment to the substrate contains copper coated diamond particles with a percentage ratio of copper to diamond volumes of 20: 80, has a specific thermal conductivity of 781 W / (m • K) and KTP 4.8 million parts / ^o C (25 - 400 ^o C), which practically coincides with the CTE of the substrate of aluminum nitride. 14. The layered product according to item 12, characterized in that the layer intended for attachment to the substrate contains copper coated diamond particles with a percentage ratio of copper to diamond 37: 63, has a thermal conductivity of 698 W / (m • K) and KTP 7.6 million parts / ^o C (25 - 400 ^o C), which practically coincides with the CTE of the beryllium oxide substrate.

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