Graphite evaporation boat and method of making the same

Abstract

The application discloses a graphite evaporation boat and a preparation method thereof. A coating structure is formed on an evaporation side of the evaporation boat. The coating structure comprises the following components by mass fraction: 60-80% of a base filler; 10-15% of silicon; 1-5% of a nickel-aluminum composite powder; 10-15% of a heat-conducting filler; and 0.5-2% of a glue adhesive. The coating structure is formed through heat pressure sintering at an increasing temperature in batches. The application is based on a multi-component coating. Through heat pressure sintering treatment at different temperatures for multiple times, the components are easy to form melt diffusion of different components, and the internal crystal components are subjected to multiphase melting and reaction in the sintering process, so that a dense composite ceramic coating is gradually formed, and the corrosion resistance of the graphite evaporation boat is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of evaporation boat, in particular to a graphite evaporation boat and a preparation method thereof. BACKGROUND

[0002] Vacuum evaporation of aluminum has a very wide application, such as evaporation of aluminum on substrate material, as a conductive film or composite current collector, wherein the evaporation boat is the most important consumable part, and the service life thereof is directly related to the production efficiency and cost of enterprises. At present, the evaporation boat material is mainly a composite ceramic base, but the cost is relatively high.

[0003] And for the graphite material evaporation boat, the main reason for its elimination is still easy to be corroded by aluminum liquid, resulting in low service life, which is not conducive to continuous production and seriously affects the production efficiency.

[0004] In the prior art, in order to increase the service life of the graphite evaporation boat, a coating is generally formed on the evaporation side of the evaporation boat to isolate the aluminum liquid corrosion. Generally, the deposition method is used, which has limited deposition thickness on the one hand, and greatly increases the processing cost on the other hand. At the same time, the coating formed by the above-mentioned method is easy to fall off during later use.

[0005] Therefore, further improvement is needed. SUMMARY

[0006] The present application aims to at least solve one of the problems in the related art. To this end, one object of the present application is to provide a graphite evaporation boat, which forms a protective coating on the evaporation side of the boat body based on multiple heat pressing treatments at different temperatures, thereby increasing the service life of the evaporation boat.

[0007] The technical solution of the present application is as follows:

[0008] A graphite evaporation boat, which forms a coating structure on the evaporation side, the coating structure comprising the following components by mass fraction:

[0009] Base filler 60%-80%;

[0010] Silicon 10-15%;

[0011] Nickel-aluminum composite powder, 1-5%;

[0012] Thermal conductive filler, 10-15%;

[0013] Adhesive 0.5-2%;

[0014] The coating structure is formed by multiple heat pressing sintering treatments at different temperatures.

[0015] Further, the coating base material is any one or combination of aluminum oxide, silicon carbide and silicon nitride.

[0016] Further, the heat-conducting filler is hexagonal boron nitride and / or aluminum nitride.

[0017] Further, the adhesive is an organic resin adhesive.

[0018] Further, the particle size of the powder material is 20-50 μm.

[0019] The sintering preparation method of the graphite evaporation boat comprises the following steps:

[0020] A graphite matrix blank is provided;

[0021] A coating slurry is configured and coated;

[0022] First temperature rising, the solvent in the coating is removed, the temperature is raised to the solidification temperature in gradient and kept, the matrix coating is formed;

[0023] Second temperature rising, the temperature is rapidly raised to the first sintering temperature in vacuum environment, the first sintering temperature is controlled above the melting point temperature of aluminum and below the melting point temperature of nickel, the expansion is inhibited by low applied pressure and the temperature is rapidly released after the preliminary compaction, and the pressure is applied after the furnace cooling;

[0024] Third temperature rising, the protective gas is introduced, the temperature is slowly raised to the second sintering temperature, the non-metallic substance is allowed to participate in the reaction, the compaction is performed by high applied pressure, and the furnace cooling is performed after the sufficient heat preservation and pressure preservation;

[0025] The block-shaped material after the forming is cut and processed as required to obtain the evaporation boat.

[0026] Further, the powder is added into the solvent according to the proportion to obtain the slurry with a solid content of 30-40%, and the slurry is wet mixed and coated.

[0027] Further, the temperature is kept for 2-5 min after the first temperature rising, and the coating with a thickness of 0.5-3 mm is formed after the preliminary solidification.

[0028] Further, the second temperature rising rate is 100-150 °C, and the first sintering temperature is 660-800 °C.

[0029] Further, the pressure applied during the second temperature rising is 3-8 MPa, and the heat preservation and pressure preservation are performed for 3-5 min.

[0030] Further, the third temperature rising rate is 5-10 °C / min, and the second sintering temperature is 1600-1800 °C.

[0031] Further, the pressure applied during the third temperature rising is 25-30 MPa, and the heat preservation and pressure preservation are performed for 90-120 min.

[0032] The beneficial effects in the application: based on the multi-component coating, the components are easy to form melt diffusion of different components through multiple different temperature hot-pressing sintering processes, the internal crystal components are multiphase molten and reacted during the sintering process to gradually form a densified composite ceramic coating, which can improve the corrosion resistance of the graphite evaporation boat. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the contents in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application.

[0034] A graphite evaporation boat, which is formed with a coating structure on the evaporation side, the coating structure comprises the following components with the mass fraction:

[0035] The base filler 60%-80%, such as alumina, silicon carbide, silicon nitride, etc., can be mixed in any ratio, has good corrosion resistance and mechanical strength;

[0036] Silicon 10-15%, as an interface connection reinforcing material, improves the wettability during sintering, and also has good thermal conductivity;

[0037] Nickel-aluminum composite powder, 1-5%, the mass fraction of nickel is preferably 70-90%; plays a role in reducing the corrosion of aluminum, and acts as a sintering process melt to promote sintering, and forms strengthening (Al-Si solid solution strengthening, nickel-aluminum solid solution strengthening-reaction, etc.) with other components during subsequent heating process, and increases the coating performance;

[0038] Hexagonal boron nitride and / or aluminum nitride, 10-15%, as a thermal conductive filler, can be mixed in any ratio, and other components of thermal conductive ceramic materials can also be used;

[0039] Adhesive 0.5-2%, preferably organic adhesive, such as phenolic resin, epoxy resin, etc., as a preliminary binder for each component, and finally sintered and carbonized;

[0040] After ball milling and screening, the particle size of the above-mentioned powder is about 20-50 μm;

[0041] The coating structure is formed through multiple hot-pressing sintering processes.

[0042] The sintering preparation method of the above-mentioned graphite evaporation boat comprises the following steps:

[0043] Providing a graphite base blank; the graphite base blank is prepared from high-purity fine-crystal graphite;

[0044] The coating slurry is configured and coated; the powder is added into a solvent (such as water or alcohol) according to the proportion to prepare a slurry with a solid content of 30-40%, and the slurry is coated after wet mixing. The coating method can be selected from conventional coating methods such as spraying and screen coating.

[0045] First temperature rise, remove the solvent in the coating, gradient heating to 120-150℃ (based on the curing temperature of the resin, set reasonably), heat preservation for 2-5min, form the base coating, if necessary, can be dried under low vacuum environment and multiple spraying to get the desired coating thickness; preferably the coating thickness after drying is 0.5-3mm, too thick coating thickness will affect the heat conduction, too thin coating is not easy to process, and the protection effect is limited;

[0046] Second temperature rise, 100-150℃ / min rapid heating to 660-800℃, provide 5-10Pa low vacuum environment, and apply pressure 3-8MPa, heat preservation for 3-5min, stop applying pressure after cooling in the furnace; due to the rapid temperature rise, relatively low temperature and short action time, promote the melting of metal filler (Al), the formed melt fills and distributes to the pores of the material, to a certain extent, improve the density of the coating, which is beneficial to subsequent processing; aluminum is easy to react with nickel to form intermetallic compounds when it melts, and basically does not react with other components; the related adhesive melts and distributes to the gap between the coatings after heating and pressing, and is initially carbonized, and the exhaust gas is discharged; applying a relatively low pressure can prevent the lattice from expanding due to excessive heating;

[0047] Third temperature rise, 5-10℃ / min heating to 1600-1800℃, at this time the non-metallic materials participate in the reaction, and the protective gas (nitrogen) is introduced, the pressure is increased to 25-30MPa, heat preservation and pressure for 90-120min, and the composite bonding phase is formed with the blank, and the furnace is cooled;

[0048] After further heating, nickel and silicon are dissolved to provide enough melt components to fill into the pores of the coating, promote the migration and diffusion of substances in the system, and the metal substances, silicon, boron nitride, etc. in the system participate in the reaction, such as reacting with the graphite interface and the carbonized adhesive to produce silicon carbide, nickel carbide, etc., and reacting with nitrogen to produce silicon nitride, etc. A small amount of remaining aluminum will react with boron nitride to form various dense and orderly arranged crystals. At the same time, alumina, silicon and aluminum nitride / silicon nitride will also form a sialon solid solution, increasing the mechanical properties and corrosion resistance of the coating. At the same time, the metal phase is easy to form a solid solution with other substances (such as silicon) to strengthen and improve the strength and corrosion resistance.

[0049] The use of multiple hot pressing methods can avoid the initial intense heat release during the reaction of nickel and aluminum, which affects the structure of the ceramic materials in the system, and can also initially improve the density of the coating, promote the coating material to form initial diffusion with the melt, and facilitate the reaction of the components in the coating structure to form ceramic crystals or alloying, thereby increasing the corrosion resistance of the coating.

[0050] The block-shaped material after molding is cut and machined as needed to obtain the evaporation boat.

[0051] Example 1

[0052] A graphite evaporation boat, the coating structure of which comprises the following components by mass fraction:

[0053] Aluminum oxide 65%; silicon 15%; nickel-aluminum composite powder (80%-20%) 3%; hexagonal boron nitride 15%; phenolic resin (powder) 2%;

[0054] After the ceramic components are ball-milled, dried and sieved, the powder particle size is controlled at about 50 μm.

[0055] The sintering method is as follows:

[0056] S1 provides a graphite matrix blank;

[0057] S2 configures a coating slurry with a solid content of 30%, and the resin is dissolved in ethanol and then added to the slurry, and after 5h stirring, the wet mixing is performed, and then the slurry is sprayed and coated;

[0058] S3 is heated to 120℃ at a gradient, and after 4min of heat preservation, the coating thickness is about 0.8mm after drying;

[0059] S4 is rapidly heated to 680℃ at a rate of 100℃ / min, a low vacuum environment of 5-10Pa is provided, and a pressure of 3MPa is applied, heat preservation is performed for 5min, and after cooling in the furnace, the pressure is stopped;

[0060] S5 is heated to 1600℃ at a rate of 5℃ / min, and a protective gas (nitrogen) is introduced, the hot-pressing pressure is 30MPa, and after heat preservation and pressure preservation for 120min, the furnace is cooled;

[0061] S6 is cut and machined as needed after the block-shaped material is molded.

[0062] Example 2

[0063] A graphite evaporation boat, the coating structure of which comprises the following components by mass fraction:

[0064] Silicon carbide 70%; silicon 10%; nickel-aluminum composite powder (80%-20%) 3.5%; aluminum nitride 15%; phenolic resin 1.5%;

[0065] After the ceramic components are ball-milled, dried and sieved, the powder particle size is controlled at about 50 μm.

[0066] The sintering method is as follows:

[0067] S1 provides a graphite matrix blank;

[0068] S2 configure the coating slurry with solid content of 35%, the resin is dissolved in ethanol and then added into the slurry, and the wet mixing is stirred for 5 hours before spraying coating;

[0069] S3 gradient heating to 120℃, holding for 5min, drying to form a coating with a thickness of about 1.5mm;

[0070] S4 rapid heating to 700℃ at 100℃ / min, providing a low vacuum environment of 5-10Pa, and applying a pressure of 5MPa, holding for 3min, stopping the pressure after cooling in the furnace;

[0071] S5 heating to 1700℃ at 5℃ / min, and passing protective gas (nitrogen), hot-pressing pressure of 25MPa, holding and pressure for 100min, and cooling in the furnace;

[0072] S6 cutting and processing the block-shaped material as needed after forming.

[0073] Example Three

[0074] A graphite evaporation boat, the coating structure of which comprises the following components by mass fraction:

[0075] Silicon nitride 75%; silicon 10%; nickel-aluminum composite powder (80%-20%) 3.5%; aluminum nitride 10%; phenolic resin 1.5%;

[0076] The ceramic components are dried and sieved after ball milling, and the powder particle size is controlled at about 30μm.

[0077] The sintering method is as follows:

[0078] S1 providing a graphite base blank;

[0079] S2 configure the coating slurry with solid content of 40%, the resin is dissolved in ethanol and then added into the slurry, and the wet mixing is stirred for 4 hours before spraying coating;

[0080] S3 gradient heating to 140℃, holding for 3min, drying to form a coating with a thickness of about 2mm;

[0081] S4 rapid heating to 750℃ at 120℃ / min, providing a low vacuum environment of 5-10Pa, and applying a pressure of 5MPa, holding for 3min, stopping the pressure after cooling in the furnace;

[0082] S5 heating to 1800℃ at 10℃ / min, and passing protective gas (nitrogen), hot-pressing pressure of 25MPa, holding and pressure for 90min, and cooling in the furnace;

[0083] S6 cutting and processing the block-shaped material as needed after forming.

[0084] Example Four

[0085] A graphite evaporation boat, the coating structure of which comprises the following components by mass fraction:

[0086] Silicon carbide and aluminum oxide 70%, mass ratio 3:2; silicon 10%; nickel-aluminum composite powder (80%-20%), 4%; aluminum nitride 15%; phenolic resin 1%;

[0087] After the ceramic components are ball milled, dried and sieved, the powder particle size is controlled at about 30 μm.

[0088] The sintering method is as follows:

[0089] S1 provides a graphite matrix blank;

[0090] S2 configures a coating slurry with a solid content of 30%, the resin is dissolved in ethanol and then added to the slurry, and after wet mixing for 5 h of stirring, spraying coating is performed;

[0091] S3 gradient heating to 150℃, holding for 2 min, drying to form a coating thickness of about 2.8 mm;

[0092] S4 rapid heating to 800℃ at 150℃ / min, providing a low vacuum environment of 5-10 Pa, and applying a pressure of 5 MPa, holding for 3 min, and stopping the pressure after furnace cooling;

[0093] S5 heating to 1700℃ at 8℃ / min, and introducing a protective gas (nitrogen), hot pressing pressure 28 MPa, holding and pressure maintaining for 100 min, and furnace cooling;

[0094] S6 cutting and processing the formed blocky material as needed.

[0095] Example Five

[0096] A graphite evaporation boat, the coating structure of which comprises the following components by mass fraction:

[0097] Silicon carbide and aluminum oxide 65%, mass ratio 2:3; silicon 15%; nickel-aluminum composite powder (80%-20%), 4.5%; aluminum nitride 15%; phenolic resin 0.5%;

[0098] After the ceramic components are ball milled, dried and sieved, the powder particle size is controlled at about 20 μm.

[0099] The sintering method is as follows:

[0100] S1 provides a graphite matrix blank;

[0101] S2 configures a coating slurry with a solid content of 40%, the resin is dissolved in ethanol and then added to the slurry, and after wet mixing for 3 h of stirring, spraying coating is performed;

[0102] S3 Gradient temperature rising to 150℃, holding for 3min, drying, coating thickness about 1mm;

[0103] S4 Fast rising to 700℃ at 100℃ / min, providing 5-10Pa low vacuum environment, and applying pressure 5MPa, holding for 3min, stopping applying pressure after cooling down with furnace;

[0104] S5 Rising to 1800℃ at 10℃ / min, and inputting protective gas (nitrogen), hot-pressing pressure 28MPa, holding and pressure-keeping for 120min, and cooling down with furnace;

[0105] S6 Cutting and processing the block material after molding according to needs.

[0106] Destructive experiment

[0107] Test method, the evaporation boat blank is processed according to size 130*35*10, the boat body to be tested is clamped at different electrode parts of the same evaporation equipment, and the same evaporation conditions are controlled, that is, the voltage, wire feeding speed are the same, the voltage is gradually increased in advance according to the gradient pressure-increasing mode, the power is controlled at about 3KW when the evaporation is stable, the vacuum degree is controlled at 10 -2 mba above, the continuous evaporation is carried out when the stable wire feeding speed is controlled at 400mm / min, the aluminum wire diameter is 1.8mm, and the failure time is recorded; the evaporation boat failure is determined as follows: after increasing the evaporation power, the boat body cannot be lighted, the aluminum wire cannot be melted or evaporated, the aluminum accumulation is caused, or the serious violent boiling situation is caused on the boat surface, the wire feeding is stopped, and the failure time is recorded.

[0108] Based on the components and preparation process in example three; the failure time is about 8.5h, the corrosion resistance can be greatly improved compared with the traditional graphite evaporation boat, and the preparation cost is relatively low;

[0109] Comparative example one only forms a 0.2mm boron nitride coating on the surface of the graphite boat body by CVD deposition, the failure time is about 6.4h, the setting of the coating can greatly improve the corrosion resistance, but the boron nitride will also react with the aluminum liquid at high temperature, especially under the mechanical impact of the aluminum wire feeding, the coating corrosion will be accelerated, after the coating failure, the aluminum liquid invades the graphite component, and the corrosion of the boat body occurs soon, causing failure, but the corrosion degree is better than that of the conventional graphite evaporation boat.

[0110] Comparative example two is a conventional graphite evaporation boat (domestic), the failure time is about 3.2h, mainly because of the mechanical impact of the molten aluminum liquid, which soon causes large corrosion holes of the evaporation boat, causing failure.

[0111] In the present application, the structures and connection relationships not described in detail are prior art, and the structures and principles are well-known technology, which will not be described here.

[0112] In this application, unless otherwise clearly indicated and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integrated; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0113] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a graphite evaporation boat, comprising the following steps: providing a graphite base blank; configuring a coating slurry, and coating; first temperature rising, removing the solvent in the coating, gradient temperature rising to a solidification temperature and holding, forming a base coating; second temperature rising, rapidly rising to a first sintering temperature under vacuum, the first sintering temperature being controlled above the melting point of aluminum and below the melting point of nickel, preliminary compaction under low applied pressure, inhibiting expansion, and rapid pressure and temperature release, stopping the pressure application after furnace cooling; third temperature rising, slowly rising to a second sintering temperature under a protective gas, so that the non-metallic substances participate in the reaction, compaction under high applied pressure, sufficient holding and pressure maintaining, and furnace cooling to form a coating structure on the evaporation side of the graphite base; cutting and surface processing the formed block material as needed to obtain the evaporation boat; wherein the coating raw material for forming the coating structure comprises the following components by mass fraction: base filler 60-80%; silicon 10-15%; nickel-aluminum composite powder 1-5%; heat-conducting filler 10-15%; adhesive 0.5-2%.

2. The method of claim 1, wherein the base filler is any one or combination of aluminum oxide, silicon carbide and silicon nitride.

3. The method of claim 1, wherein the heat-conducting filler is hexagonal boron nitride and / or aluminum nitride.

4. The method of claim 1, wherein the adhesive is an organic resin adhesive.

5. The method of claim 1, wherein the raw material for forming the coating structure is added to a solvent according to the ratio to obtain a slurry with a solid content of 30-40%, and the wet mixing is followed by coating.

6. The method of claim 1, wherein the holding time after the first temperature rising is 2-5 min, and the coating formed after the preliminary solidification has a thickness of 0.5-3 mm.

7. The method of claim 1, wherein the second temperature rising rate is 100-150℃, and the first sintering temperature is 660-800℃; the applied pressure is 3-8 MPa, and the holding and pressure maintaining time is 3-5 min.

8. The method of claim 1, wherein the third temperature rising rate is 5-10℃ / min, and the second sintering temperature is 1600-1800℃; the applied pressure is 25-30 MPa, and the holding and pressure maintaining time is 90-120 min. ​ ​ ​ ​ ​ ​ ​ ​ ​