Molybdenum-copper composite strip for heat sink and preparation method thereof

Abstract

The application provides a molybdenum-copper composite coiled material for a heat sink and a preparation method thereof, and relates to the technical field of molybdenum-copper composite heat sink materials. The method adopts ammonium heptamolybdate for heat preservation in three temperature zones, which is beneficial to the growth of molybdenum trioxide, and generates coarse and loose molybdenum trioxide; the coarse and loose molybdenum trioxide is reduced to obtain very fine molybdenum powder; the ultra-fine molybdenum powder is mixed with a copper-containing solution to obtain a solid-liquid mixture, and then the solid-liquid mixture is reduced in hydrogen to obtain uniform molybdenum-copper powder, so that the material organization is more uniform; and the ultra-fine molybdenum powder is easier to sinter due to the larger surface activity, and can be sintered to be dense at a lower sintering temperature; the application also adopts polyformaldehyde, polyethylene, styrene-butadiene-styrene and other high molecular organic substances as binders, so that the obtained heat sink material has better fluidity when being pressed into a shape, is easy to be removed in the debinding stage, and almost has no residue, and can obtain molybdenum-copper heat sink material with better size precision and better density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molybdenum-copper composite heat sink material, in particular to a molybdenum-copper composite coiled material for heat sink and a preparation method thereof. BACKGROUND

[0002] The molybdenum-copper heat sink material is a composite material of molybdenum and copper, which is often combined with a chip in the electronic industry as a heat dissipation material. The material usually has high thermal conductivity and low thermal expansion. The material closed pores refer to some pores appearing in the sintering process of the powder compact, which are completely wrapped by the powder and isolated from the outside. Rolling is a kind of pressure processing method that reduces the material section and increases the length to the target thickness by passing the metal blank through the gap between a pair of rotating rollers and compressing it by the rollers.

[0003] The heat sink material is often referred to as a heat dissipation base plate material combined with a chip in the electronic packaging industry. The molybdenum-copper heat sink material is an important material currently applied to chip heat dissipation. It has the advantages of high thermal conductivity, thermal expansion coefficient matching with the chip, and high cost performance. On the one hand, at present, molybdenum skeletons are basically prepared by pressing and sintering, and then copper infiltration is carried out to produce molybdenum-copper composite materials. The material prepared by this infiltration method needs a large amount of material machining removal, and the material utilization rate is extremely low. The price of raw material powder for preparing the material is relatively high, resulting in high product cost, which is not conducive to the current market competition. On the other hand, in the process of sintering the molybdenum skeleton, material closed pores are easily formed, which leads to the problem of serious non-penetration of copper infiltration, resulting in high unqualified rate of the material.

[0004] The above prior art scheme mainly exists the following technical problems by first pressing and sintering to prepare a molybdenum skeleton, and then carrying out copper infiltration to produce a molybdenum-copper composite material:

[0005] 1. It is difficult to press out qualified thin materials, and a large amount of material removal is needed by machining the prepared thick blank, resulting in great material waste and increasing production cost;

[0006] 2. In the process of sintering the molybdenum skeleton, material closed pores are easily formed, which leads to the problem of non-penetration of copper infiltration;

[0007] 3. The shape of the produced material is sheet-shaped, and it is difficult to realize subsequent cutting and other machining automation.

[0008] Therefore, the present application designs a molybdenum-copper composite coiled material for heat sink and a preparation method thereof. SUMMARY

[0009] The application provides a molybdenum-copper composite coiled material for heat sink and a preparation method thereof.

[0010] In order to achieve the above-mentioned purpose, the embodiment of the application provides a molybdenum-copper composite coiled material for heat sink and a preparation method thereof. 24 The method adopts ammonium heptamolybdate (chemical formula: (NH4)6Mo7O 24 ) for heat preservation in three temperature zones, which is beneficial to the growth of molybdenum trioxide and the generation of coarse and loose molybdenum trioxide (MoO3), and the coarse and loose molybdenum trioxide (MoO3) is reduced to obtain very fine molybdenum powder; the ultra-fine molybdenum powder with a particle size of less than 0.5 um is mixed with a copper-containing solution to obtain a solid-liquid mixture, and the solid-liquid mixture is reduced in hydrogen with a flow rate of greater than 10 L / min; the molybdenum-copper powder obtained by mixing and reducing the copper-containing solution is uniform, so that the material structure is more uniform; and the ultra-fine molybdenum powder is easier to sinter due to the larger surface activity, and can be sintered to be dense at a lower sintering temperature; the application also adopts polyformaldehyde, polyethylene, styrene-butadiene-styrene and other high molecular organic substances as the binder, so that the heat sink material has better fluidity when being pressed into a shape, is easy to be removed in the debinding stage, and almost no residue is left, so that the molybdenum-copper heat sink material with better size accuracy and better density can be obtained.

[0011] The embodiment of the application provides a preparation method of a molybdenum-copper composite coiled material for heat sink, which comprises the following steps.

[0012] S1: reducing ammonium heptamolybdate by a multi-temperature zone reduction furnace to obtain molybdenum powder;

[0013] S2: calculating the amount of copper according to a target molybdenum-copper alloy to configure a copper-containing solution, and mixing and stirring the molybdenum powder and the copper-containing solution in proportion to obtain a solid-liquid mixture; an automatic stirrer is used for stirring;

[0014] S3: reducing the solid-liquid mixture in the multi-temperature zone reduction furnace to obtain a molybdenum-copper mixture;

[0015] S4: performing granulation and screening treatment on the molybdenum-copper mixture to obtain a molybdenum-copper binder powder;

[0016] S5: mixing the molybdenum-copper binder powder and a high molecular organic substance in proportion, and performing pressing, degumming, rolling and material collection to obtain a molybdenum-copper composite coiled material for heat sink.

[0017] Preferably, the multi-temperature zone in step S1 is specifically as follows: the temperature of the first temperature zone is 100-200 DEG C, the heat preservation time is 1-2 h; the temperature of the second temperature zone is 200-400 DEG C, the heat preservation time is 1-2 h; and the temperature of the third temperature zone is 400-800 DEG C, the heat preservation time is 1-2 h.

[0018] Preferably, the reduced gas in step S1 is hydrogen with purity higher than 99% and flow rate greater than 10 L / min; the particle size of the molybdenum powder is less than or equal to 0.5 μm.

[0019] Preferably, the copper-containing solution in step S2 is copper sulfate or copper nitrate solution; and the target molybdenum-copper alloy is any one of Mo60Cu, Mo65Cu, Mo70Cu, Mo75Cu, Mo80Cu, Mo85Cu, Mo90Cu and Mo95Cu.

[0020] Preferably, the multi-temperature zones in step S3 are 150-200℃, 200-300℃ and 300-600℃ in sequence, and the holding time is 1h±10min, 2h±10min and 1h±10min in sequence.

[0021] Preferably, the loading height of the solid-liquid mixture in step S3 is less than or equal to 1.0 cm; the reduced gas is hydrogen with flow rate greater than or equal to 10 L / min and purity greater than 99%.

[0022] Preferably, the molybdenum-copper mixture in step S4 is granulated and screened under the protection of nitrogen.

[0023] Preferably, the pressing, degumming, rolling and collecting process in step S5 is specifically as follows: a press, a degumming furnace, a rolling mill and an automatic coiling machine are connected and matched to automatically press the heat sink molybdenum-copper composite coiled material.

[0024] Preferably, the three temperature zones in the degumming furnace in step S5 are 200-400℃, 400-600℃ and 600-800℃ in sequence; and the high-molecular organic matter is at least one of polyoxymethylene, polyethylene and styrene-butadiene-styrene.

[0025] Based on the general concept of the application, the embodiments of the application also provide a heat sink molybdenum-copper composite coiled material prepared by the preparation method.

[0026] Reaction mechanism:

[0027] Ammonium heptamolybdate is an inorganic compound with chemical formula (NH4)6Mo7O 24 , which is a colorless crystalline solid and belongs to the same polyacid compound.

[0028] Ammonium heptamolybdate (chemical formula: (NH4)6Mo7O 24 ) is reduced to prepare molybdenum powder, and the chemical reaction formula is as follows:

[0029] (NH4)6Mo7O 24 → NH3 + MoO3 + H2O

[0030] MoO3+3H2= Mo+3H2O

[0031] The solid-liquid mixture is reduced in a multi-temperature zone reduction furnace to obtain a molybdenum-copper mixture, and the chemical reaction formula is as follows:

[0032] CuSO4 → CuO + SO3(gas)

[0033] CuO+H2= Cu +H2O

[0034] The above scheme of the present application has the following beneficial effects:

[0035] 1. The present application adopts ammonium heptamolybdate (chemical formula: (NH4)6Mo7O 24 ) for heat preservation in three temperature zones, which is beneficial to the growth of molybdenum trioxide, and generates coarse and loose molybdenum trioxide (MoO3), which is reduced to obtain very fine molybdenum powder;

[0036] 2. Compared with the prior art of directly pressing and sintering molybdenum to obtain a molybdenum skeleton, and then melting and infiltrating copper in the molybdenum skeleton, which leads to uneven infiltration, the present application fully mixes ultra-fine molybdenum (0.5um or less) with a copper-containing solution to obtain a solid-liquid mixture, and then reduces the solid-liquid mixture in hydrogen gas with a flow rate greater than 10L / min, which uniformly mixes and reduces the molybdenum-copper powder, making the material structure more uniform; and the ultra-fine molybdenum powder is easier to sinter due to its larger surface activity, and can be sintered to be dense at a lower sintering temperature;

[0037] 3. The present application uses polyformaldehyde, polyethylene, styrene-butadiene-styrene, etc. as a binder, and the heat sink material obtained has better flowability when pressed into shape, is easy to remove during the debinding stage, and has almost no residue, so that a molybdenum-copper heat sink material with better size accuracy and better density can be obtained;

[0038] 4. The present application connects and cooperates the pressing machine with the degreasing furnace, rolling mill and material collecting machine, which can greatly improve the material utilization rate and realize semi-automatic production of molybdenum-copper composite coiled material.

[0039] 5. The present application solves the problem of material closed pores in the sintering process of the molybdenum-copper material prepared by the infiltration method, which leads to impermeable problem, and solves the problem of high material waste rate and high production cost, and the prepared coiled material is more convenient for subsequent automatic processing. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0041] Figure 1 is a process flow chart of the molybdenum copper heat sink material coil preparation method of the embodiment of the present application.

[0042] Figure 2 is a pressing and collecting schematic diagram in the molybdenum copper heat sink material coil preparation method of the embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and advantages of the present application more clear, the following will be described in detail in combination with the drawings and specific embodiments.

[0044] Unless otherwise defined, all the professional terms used in the following have the same meaning as generally understood by those skilled in the art. The professional terms used in this paper are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0045] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0046] The present application provides a molybdenum copper composite coil for heat sink and a preparation method thereof aiming at the existing problems, and the process flow is as shown in Figure 1 ; wherein the pressing and collecting schematic diagram is as shown in Figure 2 .

[0047] Embodiment 1

[0048] A preparation method of a molybdenum copper composite coil for heat sink, comprising the following steps:

[0049] Step 1: Preparation of molybdenum powder: reduce ammonium heptamolybdate (chemical formula: (NH4)6Mo7O 24 ) by a multi-temperature zone reduction furnace to prepare molybdenum powder. The first temperature zone is set to 100℃, the second temperature zone is set to 200℃, and the third temperature zone is set to 400℃, and the reduction gas is hydrogen, and the hydrogen purity is required to be higher than 99%, the hydrogen flow is greater than 10L / min, the mixture boat height is not greater than 1cm, and the ultra-fine particle size (0.5μm below) molybdenum powder is obtained.

[0050] Step 2 precursor mixture: according to the composition of the molybdenum-copper alloy produced, the copper content required is calculated. Then mix the appropriate proportion of copper sulfate solution into the appropriate proportion of molybdenum powder, and stir for more than 20h by automatic stirrer, so that the two are fully and uniformly mixed and a solid-liquid mixture is obtained.

[0051] Step 3 mixture reduction: the solid-liquid mixture of step 2 is reduced in a multi-temperature zone reduction furnace. The first temperature zone is set to 170°C for 1h, the second temperature zone is set to 250°C for 2h, and the third temperature zone is set to 400°C for 1h. The reduction gas is hydrogen. In order to ensure that the molybdenum-copper powder obtained by reduction has a small particle size, the purity of hydrogen is required to be higher than 99%, the hydrogen flow is required to be greater than 10L / min, and the height of the mixture in the boat cannot be greater than 1cm.

[0052] Step 4 granulation and screening: since the molybdenum-copper powder produced in step 3 has a small particle size, which is not conducive to the flow of the mixture, it is necessary to perform granulation treatment on the molybdenum-copper powder. Add SBS forming agent to the stirrer at a ratio of 100mL per 1kg of mixed powder, use nitrogen as a protective atmosphere to avoid oxidation, stir for 5h, then bake in an oven for 1h, and then pass through a sieve with ultrasonic screening.

[0053] Step 5 pressing / rolling / debinding / material collection: use polyethylene, styrene-butadiene-styrene, etc. as a binder, mix it with the binder powder according to a certain ratio to form a solid-liquid fluid mixture. Through pressing and combining with a 100x100mmx2mm mold, molybdenum-copper composite materials are prepared, and through a three-temperature zone mesh belt automatic debinding furnace, the pressed strip is debound at 400°C for 0.5h, at 600°C for 0.5h, and at 800°C for 1h. Then through rolling, the target thickness of the strip can be obtained as 1.5mm, 1.0, 0.8, 0.5mm. Through the rolling force, the pressed strip is taken out and collected by the automatic coiled material collector connected together to produce a coiled material of molybdenum-copper composite material with a thickness of 1.5mm, 1.0, 0.8, 0.5mm.

[0054] Example 2

[0055] A method for preparing a molybdenum-copper composite coiled material for heat sink, comprising the following steps:

[0056] Step 1: preparation of molybdenum powder: ammonium heptamolybdate ((NH4)6Mo7O 24) to prepare molybdenum powder. The first temperature zone is set to 100°C for 1 h, the second temperature zone is set to 200°C for 2 h, and the third temperature zone is set to 400°C for 1 h. The reducing gas is hydrogen, which requires a purity of more than 99% and a flow rate of more than 10 L / min. The mixture loading height should not be more than 1 cm. The obtained molybdenum powder has a super-fine particle size (less than 0.5 μm).

[0057] Step 2: Precursor mixing: The copper content is calculated according to the composition of the molybdenum-copper alloy to be produced. Then, a copper sulfate solution of appropriate proportion is mixed with molybdenum powder of appropriate proportion, and the mixture is stirred for more than 20 h by an automatic stirrer to ensure that the two components are fully and uniformly mixed to obtain a solid-liquid mixture.

[0058] Step 3: Reduction of the mixture: The solid-liquid mixture of Step 2 is reduced in a multi-zone reduction furnace. The first temperature zone is set to 150°C for 1 h, the second temperature zone is set to 200°C for 2 h, and the third temperature zone is set to 300°C for 1 h. The reducing gas is hydrogen, which requires a purity of more than 99% and a flow rate of more than 10 L / min. The mixture loading height should not be more than 1 cm.

[0059] Step 4: Granulation and screening: The molybdenum-copper powder prepared in Step 3 has a fine particle size, which is not conducive to the flow of the mixture. Therefore, the molybdenum-copper powder needs to be granulated. The mixed powder is added to a stirrer, and SBS forming agent is added at a ratio of 100 mL per 1 kg of mixed powder. Nitrogen is used as a protective atmosphere to prevent oxidation. The mixture is stirred for 5 h and then baked in an oven for 1 h. The mixture is then sieved using an ultrasonic powder sifter.

[0060] Step 5: Pressing / rolling / delamination / rolling-up: Polyethylene, styrene-butadiene-styrene, and other high-molecular organic substances are used as binders to mix with the binder powder to prepare a solid-liquid fluid mixture. The molybdenum-copper composite material is prepared by pressing and using a 100 x 100 mm x 2 mm mold. The pressed strip is delaminated by a three-zone mesh belt automatic delamination furnace at 400°C for 0.5 h, at 600°C for 0.5 h, and at 800°C for 1 h. The target thickness of the strip can be 1.5 mm, 1.0 mm, 0.8 mm, or 0.5 mm by rolling. The pressed strip is brought out by the rolling force, and the delaminated strip is rolled up by a connecting automatic rolling-up machine to obtain a molybdenum-copper composite material with a thickness of 1.5 mm, 1.0 mm, 0.8 mm, or 0.5 mm.

[0061] Example 3

[0062] A method for preparing a molybdenum-copper composite material for heat sinks, comprising the following steps:

[0063] Step 1 Preparation of molybdenum powder: The ammonium heptamolybdate (chemical formula: (NH4)6Mo7O 24 ) is reduced by a multi-zone reduction furnace to prepare molybdenum powder. The first temperature zone is set to 100°C for 1h, the second temperature zone is set to 200°C for 2h, and the third temperature zone is set to 400°C for 1h. The reducing gas is hydrogen, which requires a purity of more than 99% and a flow rate of more than 10L / min. The mixture loading height should not exceed 1cm. The resulting ultra-fine particle size (0.5μm or less) molybdenum powder is obtained.

[0064] Step 2 Precursor mixing: The copper content required for the production of the molybdenum-copper alloy composition is calculated. The appropriate proportion of copper sulfate solution is then mixed with the molybdenum powder in the appropriate proportion, and the mixture is stirred for more than 20h using an automatic stirrer to ensure that the two components are thoroughly and uniformly mixed to form a solid-liquid mixture.

[0065] Step 3 Reduction of the mixture: The solid-liquid mixture from Step 2 is reduced in a multi-zone reduction furnace. The first temperature zone is set to 200°C for 1h, the second temperature zone is set to 300°C for 2h, and the third temperature zone is set to 600°C for 1h. The reducing gas is hydrogen, which requires a purity of more than 99% and a flow rate of more than 10L / min. The mixture loading height should not exceed 1cm.

[0066] Step 4 Granulation and screening: The molybdenum-copper powder produced in Step 3 has a fine particle size, which makes it difficult to flow. Therefore, the molybdenum-copper powder needs to be granulated. The mixed powder is added to a stirrer, and SBS forming agent is added at a ratio of 100mL per 1kg of mixed powder. Nitrogen gas is used as a protective atmosphere to prevent oxidation. The mixture is stirred for 5h and then baked in an oven for 1h. The powder is then sieved using an ultrasonic powder sieve.

[0067] Step 5 Pressing / rolling / delamination / collecting: Polyethylene, styrene-butadiene-styrene, and other high-molecular organic substances are used as binders to mix with the binding powder at a certain ratio to form a solid-liquid fluid mixture. The molybdenum-copper composite material is prepared by pressing and combining with a 100x100mmx2mm mold. The pressed strip is delaminated by a three-zone mesh belt automatic delamination furnace at 400°C for 0.5h, 600°C for 0.5h, and 800°C for 1h. The target thickness of the strip can be obtained by rolling, such as 1.5mm, 1.0mm, 0.8mm, and 0.5mm. The pressed strip is brought out by the rolling force, and the material is collected by connecting the automatic coiling machine to produce a 1.5mm, 1.0mm, 0.8mm, or 0.5mm thick coiled molybdenum-copper composite material.

[0068] Through the above examples, different reduction temperatures are used, and the powder particle size data is as follows:

[0069]

[0070] From the above data, it can be seen that as the reduction temperature increases, the powder particle size also increases.

[0071] The above describes the preferred embodiments of the present application, it should be noted that for those skilled in the art, without departing from the principles described in the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for producing a molybdenum-copper composite strip for heat sinks, characterized by, The method comprises the following steps: S1: reducing ammonium heptamolybdate by a multi-temperature zone reduction furnace to obtain molybdenum powder; wherein the multi-temperature zone is as follows: the temperature of the first temperature zone is 100-200℃, the holding time is 1-2h; the temperature of the second temperature zone is 200-400℃, the holding time is 1-2h; the temperature of the third temperature zone is 400-800℃, the holding time is 1-2h; the particle size of the molybdenum powder is 0.5μm or less; S2: calculating the amount of copper according to a target molybdenum-copper alloy to prepare a copper-containing solution, and mixing the molybdenum powder and the copper-containing solution in proportion to obtain a solid-liquid mixture; S3: reducing the solid-liquid mixture in the multi-temperature zone reduction furnace to obtain a molybdenum-copper mixture; wherein the multi-temperature zone is 150-200℃, 200-300℃, and 300-600℃ in sequence, and the holding time is 1h±10min, 2h±10min, and 1h±10min in sequence; S4: performing granulation and screening treatment on the molybdenum-copper mixture to obtain a molybdenum-copper bonding powder; S5: mixing the molybdenum-copper bonding powder and a high-molecular organic substance in proportion, and performing pressing, degumming, rolling, and material collection to obtain a molybdenum-copper composite coil for heat sink; wherein the three temperature zones in the degumming furnace are 200-400℃, 400-600℃, and 600-800℃ in sequence; the high-molecular organic substance is at least one of polyformaldehyde, polyethylene, and styrene-butadiene-styrene; and the thickness of the molybdenum-copper composite coil for heat sink is 0.1-1.5mm.

2. The method for preparing molybdenum-copper composite roll for heat sink according to claim 1, characterized in that, The reducing gas in step S1 is hydrogen with a purity higher than 99% and a flow rate greater than 10L / min.

3. The method for preparing molybdenum-copper composite roll for heat sink according to claim 2, characterized in that, The copper-containing solution in step S2 is a copper sulfate or copper nitrate solution; and the target molybdenum-copper alloy is any one of Mo60Cu, Mo65Cu, Mo70Cu, Mo75Cu, Mo80Cu, Mo85Cu, Mo90Cu, and Mo95Cu.

4. The method for preparing molybdenum-copper composite roll for heat sink according to claim 1, characterized in that, The loading height of the solid-liquid mixture in step S3 is less than or equal to 1.0cm; the reducing gas is hydrogen with a flow rate greater than or equal to 10L / min and a purity greater than 99%.

5. The method for preparing molybdenum-copper composite roll for heat sink according to claim 4, characterized in that, The granulation and screening treatment on the molybdenum-copper mixture in step S4 is performed under the protection of nitrogen.

6. The method for preparing molybdenum-copper composite roll for heat sink according to claim 5, characterized in that, The pressing, degumming, rolling, and material collection process in step S5 is as follows: a press, a degumming furnace, a rolling mill, and an automatic material winding machine are connected and matched to automatically press the molybdenum-copper composite coil for heat sink.

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