A solder, a solder paste, a magnetron cathode assembly and a method of making the same

Abstract

The application discloses a kind of solder, solder slurry, magnetron cathode assembly and preparation method thereof, it is related to magnetron cathode assembly field.Therein, solder is obtained by 15-40wt% tungsten, 30-60wt% molybdenum and 15-40wt% nickel mixed ball milling.Solder slurry includes organic carrier, solvent and solder, organic carrier is 5-15% of the weight of the solder, solvent is 5-20% of the weight of the solder.Lamp filament and molybdenum end cap in magnetron cathode assembly are brazed using the above-mentioned solder, specific operation method is that solder slurry is coated on molybdenum end cap, sintering forms solder layer, then again heating melts solder layer to weld and fix lamp filament and molybdenum end cap.The solder in the present application has the advantages of low cost, low brazing temperature and wide range, low vapor pressure, can improve the welding effect of lamp filament and molybdenum end cap while reducing the bubbling probability of molybdenum end cap, so as to improve the qualified rate of finished product of magnetron cathode assembly.

Description

Technical Field

[0001] This invention relates to the field of magnetron cathode assemblies, and in particular to a solder, solder slurry, magnetron cathode assembly, and a method for preparing the same. Background Technology

[0002] The core of a magnetron is the cathode, which mainly consists of a thorium-tungsten filament, an upper molybdenum end cap, a lower molybdenum end cap, and a molybdenum support rod. During magnetron production, when the thorium-tungsten filament and the molybdenum end caps (the molybdenum end caps being a collective term for the upper and lower molybdenum end caps) are brazed with solder, a high-frequency induction heating method is commonly used. Under the influence of high-frequency induction, the molybdenum end caps generate heat due to the skin effect, and then transfer this heat to the solder, melting the solder and thus achieving the brazing and fixing of the thorium-tungsten filament and the molybdenum end caps.

[0003] Among them, the magnetron, as the heating element for microwave emission, has the highest temperature. However, the melting points of the thorium-tungsten filament, the upper molybdenum end cap, and the lower molybdenum end cap all exceed 2600℃. Currently, there is no process to directly weld them together; a closed-circuit bond must be achieved through brazing with intermediate solder.

[0004] Currently, the mainstream solder systems used in magnetron production are the ruthenium-molybdenum-nickel ternary system and the ruthenium-molybdenum binary system. However, both the ruthenium-molybdenum-nickel ternary system and the ruthenium-molybdenum binary system contain the rare and precious metal ruthenium, resulting in high production costs. To reduce solder costs, related technologies have gradually developed solder systems that do not contain the rare and precious metal ruthenium, such as the silicon-molybdenum binary system, the silicon-molybdenum-nickel ternary system, and the silicon-molybdenum-boron ternary system.

[0005] Among them, the brazing temperature of silicon-molybdenum binary system solder is high, exceeding the sintering temperature of the molybdenum end cap and approaching the melting point of molybdenum. During high-frequency brazing, the molybdenum end cap is prone to melting and blistering. Therefore, in the production of magnetron cathode modules, in order to reduce the probability of molybdenum end cap blistering, the temperature range of high-frequency induction heating control is often controlled within 2000-2100℃. The controllable range is small, meaning that the brazing process control requirements for silicon-molybdenum binary system solder are very high. When the brazing temperature is below this range, poor welding is likely to occur, while when the brazing temperature is above this range, the molybdenum end cap is prone to melting, resulting in a large fluctuation in the yield of magnetron cathode module finished products.

[0006] However, silicon-molybdenum-nickel ternary solders and silicon-molybdenum-boron ternary solders contain low-melting-point silicon-boron non-metallic elements, which have high vapor pressures, making them unfavorable for electron emission from cathode components.

[0007] Therefore, it is of great research significance to provide a solder with low cost, low and wide brazing temperature, low welding defect rate, low molybdenum end cap bubbling rate and low vapor pressure. Summary of the Invention

[0008] In order to improve the problems of high solder cost, high and narrow brazing temperature range, and low finished product qualification rate in related technologies, this application provides a solder, solder slurry, magnetron cathode assembly and its preparation method.

[0009] Firstly, the solder provided in this application adopts the following technical solution:

[0010] A solder is prepared from 15-40 wt% tungsten, 30-60 wt% molybdenum and 15-40 wt% nickel; wherein the tungsten has a particle size range of 0.5 μm-25 μm, the molybdenum has a particle size range of 2 μm-40 μm and the nickel has a particle size range of 2-100 μm.

[0011] By adopting the above technical solution, the solder is a tungsten-molybdenum-nickel ternary system composed of tungsten, molybdenum, and nickel, without the addition of the rare and precious metal ruthenium. Compared with the traditional ruthenium-molybdenum-nickel ternary system and ruthenium-molybdenum binary system, it has the advantage of lower cost.

[0012] Secondly, the molybdenum end caps are produced using powder metallurgy. The closer the temperature is to the melting point of molybdenum, the more prone the end caps are to melting and blistering. The solder obtained in this application, composed of a specific ratio of tungsten, molybdenum, and nickel, has a brazing temperature between 1200-1600℃, while the brazing temperature of the silicon-molybdenum binary system solder is between 2000-2100℃. Therefore, compared to the silicon-molybdenum binary system solder, the tungsten-molybdenum-nickel ternary system solder of this application has the advantages of lower brazing temperature, a wider operating temperature range, and stronger controllability. In particular, the lower brazing temperature of the solder in this application effectively improves the problem of molybdenum end cap blistering caused by excessively high brazing temperatures. This significantly improves the blistering rate of molybdenum end caps in magnetron cathode assemblies and increases the finished product qualification rate of magnetron cathode assemblies, while also reducing the power requirements of the high-frequency induction heating equipment. Furthermore, the wider brazing temperature range reduces the control requirements during the production process of magnetron cathode assemblies, lowers production difficulty, and helps improve the product stability of magnetron cathode assemblies.

[0013] In addition, tungsten, molybdenum and nickel have low vapor pressures, so long-term use will not affect the vacuum level of the magnetron and will not have an adverse effect on the lifespan of the magnetron.

[0014] Preferably, it is prepared from 20-30 wt% tungsten, 40-50 wt% molybdenum and the balance nickel; the tungsten has a particle size range of 10 μm-20 μm, the molybdenum has a particle size range of 10 μm-20 μm and the nickel has a particle size range of 40-50 μm.

[0015] By adopting the above technical solution, when the weight ratio of tungsten, molybdenum and nickel in the solder is within the above range, the welding defect rate can be further reduced. At the same time, the brazing effect between the filament and the molybdenum end cap is good, the circuit resistance after the filament and the molybdenum end cap are welded is low, and the conductivity is better.

[0016] In addition, the particle size of tungsten, molybdenum and nickel is within the above range, which can promote the mutual fusion between tungsten, molybdenum and nickel, and promote the realization of tungsten, molybdenum and nickel ternary alloying, which is conducive to obtaining uniform solder with low melting point.

[0017] Secondly, the solder preparation method provided in this application adopts the following technical solution:

[0018] A method for preparing solder includes the following steps:

[0019] Tungsten, molybdenum and nickel are mixed and ball-milled in an inert gas environment with a ball-to-material ratio of (5-15):1, a ball-milling speed of 1500rpm-1800rpm, and a ball-milling time of 10h-40h.

[0020] After ball milling, the metal powder is sieved out under vacuum or inert gas protection to obtain solder.

[0021] Ball milling tungsten, molybdenum, and nickel at specific speeds facilitates ternary alloying of these materials, allowing the solder to melt within a lower and wider range during subsequent brazing. This further reduces the probability of bubbling at the molybdenum end cap and decreases the welding defect rate between the filament and the molybdenum end cap, thereby improving the finished product qualification rate of the magnetron cathode assembly.

[0022] Thirdly, the method for preparing solder slurry provided in this application adopts the following technical solution:

[0023] A solder slurry comprising an organic carrier, a solvent, and a solder as described in any one of the above, wherein the weight of the organic carrier is 5-15% of the weight of the solder, and the weight of the solvent is 5-20% of the weight of the solder.

[0024] By adopting the above technical solution, the main function of the organic carrier is to disperse the solder and adhere it to the molybdenum end cap, so that the molybdenum end cap can be welded and fixed to the filament by the solder. In this application, the solvent dissolves and disperses the organic carrier, so that the solder is uniformly dispersed in the solder slurry. This allows the solder to be adhered and fixed to the molybdenum end cap by the adhesive effect of the organic carrier in the subsequent coating step, preventing the solder from falling off the molybdenum end cap and facilitating the integration of the solder and the molybdenum end cap.

[0025] Optionally, the organic carrier includes epoxy resin, epoxy resin diluent, and rheology modifier, wherein the weight ratio of epoxy resin, epoxy resin diluent, and rheology modifier is (60-90):(5-15):(35-65).

[0026] By adopting the above technical solution, epoxy resin provides adhesive properties, the addition of epoxy resin diluent is used to adjust the curing speed of epoxy resin, and rheology modifier has lubricating properties to improve the dispersibility of solder in organic carrier and improve the coating properties of solder slurry.

[0027] The epoxy resin diluent is selected from reactive diluents, such as any one or a combination of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0028] The rheology modifier is selected from any one or a combination of two of polyamide wax or polyethylene wax.

[0029] Because polyamide wax and polyethylene wax have lubricating properties, the addition of rheology modifiers can improve both the dispersibility and the coatability of the solder slurry.

[0030] The solvent is selected from any one or a combination of two of butyl acetate and xylene. Preferably, it is a combination of butyl acetate and xylene, with a weight ratio of butyl acetate to xylene of 1:(1-1.5).

[0031] By adopting the above technical solution, butyl acetate, with its lipophilic properties, facilitates the dispersion of epoxy resin and improves the fluidity of the solder slurry. However, butyl acetate has poor volatility, and when used alone as a solvent, the solder slurry tends to cure slowly. Conversely, using xylene alone, which has high volatility, can lead to excessively fast curing. Both excessively fast and slow curing speeds can negatively impact the adhesion stability between the solder slurry and the molybdenum end cap. Combining butyl acetate, with its good lipophilic properties, with xylene, a solvent with good volatility, promotes both uniform dispersion of the epoxy resin and a solder slurry with a moderate curing speed, further enhancing the adhesion stability between the solder slurry and the molybdenum end cap.

[0032] Preferably, the epoxy resin is a modified epoxy resin, which comprises the following raw materials in parts by weight:

[0033] Epoxy resin: 500 parts;

[0034] Polydimethylsiloxane with active group-terminated end: 40-60 parts;

[0035] Diepoxy-terminated ether monomers: 70-80 parts;

[0036] Catalyst: 0.01-0.03 parts;

[0037] Rosin solution with a mass concentration of 3-5 wt%: 20-30 parts;

[0038] Wherein, the active group in the polydimethylsiloxane with the active group end capping is hydroxyl or amino, and the ether monomer with the diepoxy group end capping is selected from any one or a combination of several of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0039] Optionally, the preparation method of the modified epoxy resin includes the following steps:

[0040] Under nitrogen protection, epoxy resin, polydimethylsiloxane with active group end capping, ether monomer with diepoxy group end capping and catalyst are uniformly mixed, and then the temperature is raised to 130-140℃ and reacted for 1-2 hours to obtain intermediate product.

[0041] Dissolve 3-5 parts by weight of rosin in 100 parts by weight of xylene to obtain a rosin solution with a mass concentration of 3-5 wt%.

[0042] Add a rosin solution with a mass concentration of 3-5 wt% to the intermediate product, control the temperature at 90-100℃, and react for 2-3 hours to obtain the modified epoxy resin.

[0043] By adopting the above technical solution, the active group-terminated polydimethylsiloxane, the diepoxy group-terminated ether monomer, and rosin have a synergistic effect on improving the adhesion strength between the modified epoxy resin and the molybdenum end cap. The modified epoxy resin obtained by the joint modification of the three has a strong penetrating effect on molybdenum, and has a strong affinity and high adhesion strength to molybdenum. It can effectively improve the stability of the solder layer in the molybdenum end cap, while also having excellent flexibility and being able to be processed in low-temperature environments.

[0044] Optionally, the solder slurry further includes a defoamer, the weight of which is 0.1-1% of the weight of the solder.

[0045] By adopting the above technical solution, if air bubbles are generated during the preparation of solder slurry, adding defoamer can eliminate the air bubbles in the solder slurry, which is beneficial to improving the adhesion between the solder slurry and the molybdenum end cap.

[0046] Among them, the defoamer is preferably an organosilicon defoamer, and more preferably a dimethylsilane-modified defoamer emulsion with good dispersibility in epoxy resin system.

[0047] Fourthly, the magnetron cathode assembly provided in this application adopts the following technical solution:

[0048] A magnetron cathode assembly, comprising:

[0049] The upper molybdenum end cap has a first solder layer, which is obtained by sintering the solder slurry described in any one of the above-mentioned items; the lower molybdenum end cap has a second solder layer, which is obtained by sintering the solder slurry described in any one of the above-mentioned items; and a molybdenum support rod is used to connect the upper molybdenum end cap and the lower molybdenum end cap.

[0050] The filament is fixed at one end to the upper molybdenum end cap by brazing through the first solder layer, and at the other end to the lower molybdenum end cap by brazing through the second solder layer.

[0051] By adopting the above technical solution, when the first solder layer and the second solder layer are selected from any of the solder slurries mentioned above in this application, the brazing temperature of the first brazing layer and the second brazing layer is low and has a wide range, which can effectively reduce the probability of bubbling of the molybdenum end cap during the brazing process and improve the brazing quality, resulting in a high finished product qualification rate of the magnetron cathode assembly.

[0052] Fifthly, the method for fabricating a magnetron cathode assembly provided in this application adopts the following technical solution:

[0053] The solder slurry described in any one of the above is applied to the upper molybdenum end cap and the lower molybdenum end cap by an automatic coating method. The upper molybdenum end cap and the lower molybdenum end cap coated with solder slurry are pre-sintered in a reducing atmosphere. The pre-sintering temperature is 500-850℃ and the pre-sintering time is 1-6h.

[0054] The pre-sintered upper molybdenum end cap and lower molybdenum end cap are sintered at high temperature. The high temperature sintering temperature is 1400-1600℃ and the sintering time is 0.1-3.5h, so that the first solder layer is formed on the upper molybdenum end cap and the second solder layer is formed on the lower molybdenum end cap.

[0055] The molybdenum support rod is resistance welded to the upper and lower molybdenum end caps to form a support assembly.

[0056] The filament is placed between the upper molybdenum end cap and the lower molybdenum end cap. One end of the filament is fixed to the upper molybdenum end cap by brazing with the first solder layer, and the other end of the filament is fixed to the lower molybdenum end cap by brazing with the second solder layer, thus obtaining the magnetron cathode assembly. During the brazing process, the temperature is controlled at 1200-1600℃ and the time is controlled at 2-10s.

[0057] By adopting the above technical solution, the solder slurry is coated. After the solder slurry forms a solder colloid, the upper and lower molybdenum end caps are pre-fired. The purpose of pre-firing is to remove organic additives from the solder colloid. If the solder colloid is not pre-fired, the organic additives will decompose and volatilize during the subsequent high-temperature sintering process to integrate the solder and molybdenum end caps. This can easily cause uneven porosity in the first and second solder layers, resulting in poor bonding stability between the first solder layer and the upper molybdenum end cap, or between the second solder layer and the lower molybdenum end cap. Furthermore, the atmosphere generated by the decomposition of organic additives will affect the quality of the first and second solder layers, leading to an increase in their melting points. During the subsequent brazing process between the filament and the molybdenum end cap, the brazing temperature increases, making the molybdenum end cap prone to blistering.

[0058] Therefore, adding a pre-burning operation can prevent the problem of poor connection stability between the solder layer and the molybdenum end cap during the production of magnetron cathode assemblies, and further reduce the problem of easy bubbling of the molybdenum end cap, which is conducive to improving the finished product qualification rate of magnetron cathode assemblies.

[0059] Optionally, during the brazing process, the temperature is controlled at 1300-1500℃ and the time is controlled at 3-6 seconds.

[0060] By adopting the above technical solution, when the temperature is controlled at 1300-1500℃ during the brazing process of the filament and the molybdenum end cap, the melting speed of the first solder layer and the second solder layer is fast and the brazing time is short. This can further improve the brazing efficiency of the filament and the molybdenum end cap while effectively reducing the bubbling problem of the molybdenum end cap.

[0061] In summary, the technical solution of this application has at least the following beneficial effects:

[0062] 1. The tungsten-molybdenum-nickel ternary solder of this application does not contain the rare and precious metal ruthenium, resulting in lower cost. Furthermore, this solder has a low melting point, allowing brazing within the range of 1200-1600℃, providing wide applicability to brazing temperatures. The lower brazing temperature effectively mitigates the problem of blistering of the molybdenum end cap during brazing. In addition, the tungsten-molybdenum-nickel ternary solder has a low vapor pressure, ensuring that long-term use will not affect the vacuum level of the magnetron or adversely impact its lifespan.

[0063] 2. By modifying the epoxy resin used as the organic carrier in the solder slurry with polydimethylsiloxane with active group end-capping, ether monomer with diepoxy group end-capping, and rosin, the adhesion stability of the solder colloid to the molybdenum end cap is effectively improved, the probability of the solder colloid falling off the molybdenum end cap is greatly reduced, the rework rate is effectively reduced, and the production efficiency of the magnetron cathode assembly is improved. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the structure of a magnetron cathode assembly.

[0065] Explanation of reference numerals in the attached figures:

[0066] 1. Upper molybdenum end cap; 11. First groove; 2. First solder layer; 3. Lower molybdenum end cap; 31. Second groove; 4. Second solder layer; 5. Molybdenum support rod; 6. Filament. Detailed Implementation

[0067] The following provides a further detailed description of this application.

[0068] In a first aspect, this application provides a solder made of 15-40 wt% tungsten, 30-60 wt% molybdenum, and 15-40 wt% nickel. The tungsten may have a particle size range of 0.5 μm-25 μm, the molybdenum a particle size range of 2 μm-40 μm, and the nickel a particle size range of 2-100 μm.

[0069] Preferably, the solder is made of 20-30 wt% tungsten, 40-50 wt% molybdenum, and the balance nickel. The preferred particle size range for tungsten is 10 μm-20 μm, for molybdenum it is 10 μm-20 μm, and for nickel it is 40-50 μm.

[0070] The solder is further preferred to contain tungsten in the range of 24-28 wt%, molybdenum in the range of 42-45 wt%, and nickel in the range of 30-31 wt%.

[0071] The above-mentioned method for preparing solder includes the following steps:

[0072] Tungsten, molybdenum and nickel are mixed and ball-milled in an inert gas environment with a ball-to-material ratio of (5-15):1, a ball-milling speed of 1500rpm-1800rpm, and a ball-milling time of 10h-40h.

[0073] After ball milling, the metal powder is sieved out under vacuum or inert gas protection to obtain solder.

[0074] The ball milling of tungsten, molybdenum and nickel is carried out in a planetary ball mill. The ball milling speed is controlled at 1500rpm-1800rpm, which is conducive to the ternary alloying of tungsten, molybdenum and nickel. This allows the solder to melt in a lower and wider range during the subsequent brazing process, which can further effectively reduce the proportion of defective welds.

[0075] Secondly, this application provides a solder slurry, comprising an organic carrier, a solvent, and the solder disclosed in the first aspect. The organic carrier comprises 5-15% of the weight of the solder, and the solvent comprises 5-20% of the weight of the solder.

[0076] In some preferred embodiments of the solder slurry, the organic carrier is preferably 8-12% of the solder weight, for example: 8%, 9%, 10%, 11%, 12%, etc. The solvent is preferably 15-20% of the solder weight, for example: 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0077] The main function of the organic carrier is to disperse the solder and adhere it to the molybdenum end cap, facilitating the welding and fixing of the end cap to the filament. Considering the uniform dispersion of the solder and the adhesion stability between the solder slurry and the molybdenum end cap, the organic carrier in this application includes epoxy resin, epoxy resin diluent, and rheology modifier, with a weight ratio of (60-90):(5-15):(35-65).

[0078] The epoxy resin is selected from any one or a combination of several of bisphenol A epoxy resin, bisphenol S epoxy resin, and bisphenol F epoxy resin.

[0079] More preferably, the epoxy resin is selected from the following modified epoxy resins:

[0080] The modified epoxy resin comprises the following raw materials in parts by weight:

[0081] Bisphenol A epoxy resin: 500 parts;

[0082] Polydimethylsiloxane with active group-terminated end: 40-60 parts;

[0083] Diepoxy-terminated ether monomers: 70-80 parts;

[0084] Catalyst: 0.01-0.03 parts;

[0085] Rosin solution with a mass concentration of 3-5 wt%: 20-30 parts;

[0086] Wherein, the active group in the polydimethylsiloxane capped with the active group is a hydroxyl or an amino group. Preferably, the polydimethylsiloxane capped with the active group is a polydimethylsiloxane capped with two active groups, such as hydroxyl-terminated polydimethylsiloxane, bis-aminopropyl polydimethylsiloxane, etc.

[0087] Optionally, the ether monomer with the diepoxy group terminus may be selected from any one or a combination of several of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0088] Preferably, the ether monomer with the diepoxy group terminus is a composition of 1,4-butanediol diglycidyl ether and polypropylene glycol diglycidyl ether, wherein the weight ratio of 1,4-butanediol diglycidyl ether to polypropylene glycol diglycidyl ether is (3-4):1.

[0089] Preferably, the ether monomer with the diepoxy group terminus is a combination of ethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether, wherein the weight ratio of ethylene glycol diglycidyl ether to polypropylene glycol diglycidyl ether is (3-4):1.

[0090] When the preferred combination of ether monomers with diepoxy groups is selected, the solder slurry exhibits moderate fluidity and a moderate curing speed. This mitigates the problems of poor solder adhesion and easy detachment caused by excessively slow curing speed, and the issues of poor solder adhesion and easy detachment caused by excessively fast curing speed, where the solder slurry solidifies before fully wetting the molybdenum end cap. Furthermore, moderate fluidity of the solder slurry facilitates uniform coating and ensures sufficient wetting of the molybdenum end cap, thereby improving the adhesion between the solder and the end cap.

[0091] Preferably, the catalyst is tetramethylammonium chloride.

[0092] The preparation method of the above-mentioned modified epoxy resin includes the following steps:

[0093] a. Under nitrogen protection, epoxy resin, polydimethylsiloxane with active group end capping, ether monomer with diepoxy group end capping, and catalyst are uniformly mixed, and then the temperature is raised to 130-140℃ and reacted for 1-2 hours to obtain an intermediate product; the epoxy resin is selected from any one or a combination of several of bisphenol A epoxy resin, bisphenol S epoxy resin, and bisphenol F epoxy resin.

[0094] b. Dissolve 3-5 parts by weight of rosin in 100 parts by weight of xylene to obtain a rosin solution with a mass concentration of 3-5 wt%; c. Add the rosin solution with a mass concentration of 3-5 wt% to the intermediate product, control the temperature at 90-100℃, and react for 2-3 hours to obtain the modified epoxy resin.

[0095] When the above-mentioned modified epoxy resin is selected as the epoxy resin, the preferred organic carrier is as follows: the weight ratio of modified epoxy resin, epoxy resin diluent and rheology modifier is (75-85):(10-15):(55-65).

[0096] The epoxy resin diluent is a reactive diluent, such as any one or a combination of several of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0097] The rheology modifier is selected from any one or a combination of two of polyamide wax or polyethylene wax.

[0098] The solvent is selected from any one or a combination of two of butyl acetate and xylene. Preferably, the solvent is a combination of butyl acetate and xylene. More preferably, the weight ratio of butyl acetate to xylene is 1:(1-1.5).

[0099] Thirdly, this application discloses a method for preparing the aforementioned solder slurry, comprising the following steps:

[0100] Preparation of the organic carrier: Mix epoxy resin or modified epoxy resin with epoxy resin diluent according to the specified ratio, and stir mechanically for 5 min-30 min at a stirring speed of 200 r / min-3000 r / min to ensure thorough mixing of the epoxy resin and epoxy resin diluent; then add rheology modifier according to the specified ratio, and stir mechanically for 5 min-30 min at a stirring speed of 200 r / min-3000 r / min to form the organic carrier;

[0101] Preparation of solder slurry: Weigh 5%-15% of the solder weight of organic carrier and add it to the solder, then add 5%-20% of the solder weight of solvent and stir; the stirring speed is 100r / min-4000r / min, and the stirring time is 5min-30min. If bubbles appear during stirring, add 0.1%-1% of the solder weight of defoamer during stirring or at the beginning of stirring to defoam.

[0102] Fourthly, this application provides a magnetron cathode assembly, referring to... Figure 1 ,include:

[0103] The upper molybdenum end cap 1 has a first groove 11, and a first solder layer 2 is provided in the first groove 11. The first solder layer 2 is obtained by applying the solder slurry in the second aspect above into the first groove 11 and then sintering it.

[0104] The lower molybdenum end cap 3 has a second groove 31, and a second solder layer 4 is provided in the second groove 31. The second solder layer 4 is obtained by applying the solder slurry in the second aspect above into the first groove 11 and then sintering it.

[0105] Molybdenum support rod 5 is located between upper molybdenum end cap 1 and lower molybdenum end cap 3, and is used to connect upper molybdenum end cap 1 and lower molybdenum end cap 3; wherein, upper molybdenum end cap 1 and molybdenum support rod 5, and lower molybdenum end cap 3 and molybdenum support rod 5 are connected by resistance welding.

[0106] The filament 6 is located between the upper molybdenum end cap 1 and the lower molybdenum end cap 3. The end of the filament 6 near the upper molybdenum end cap 1 is brazed to the upper molybdenum end cap 1 through a first solder layer 2, and the end of the filament 6 near the lower molybdenum end cap 3 is brazed to the lower molybdenum end cap 3 through a second solder layer 4. The filament 6 is preferably a thorium-tungsten filament 6.

[0107] The method for preparing the above-mentioned magnetron cathode assembly includes the following steps:

[0108] S1. The solder slurry disclosed in the second aspect is applied to the first groove 11 of the upper molybdenum end cap 1 and the second groove 31 of the lower molybdenum end cap 3. Then, the end caps coated with solder slurry are pre-sintered in a reducing atmosphere. The pre-sintering temperature is 500-850℃ and the pre-sintering time is 1-6h. The solder slurry in the first groove 11 and the second groove 31 is controlled at 5mg-15mg. The reducing atmosphere is preferably a hydrogen atmosphere, and the hydrogen flow rate is controlled at 1Nm3 / h-5Nm3 / h.

[0109] S2. The pre-sintered upper molybdenum end cap 1 and lower molybdenum end cap 3 are subjected to high-temperature sintering at a temperature of 1400-1600℃ and a sintering time of 0.1-3.5h, thereby forming a first solder layer 2 in the first groove 11 of the upper molybdenum end cap 1 and a second solder layer 4 in the second groove 31 of the lower molybdenum end cap 3.

[0110] S3. Place the molybdenum support rod 5 between the upper molybdenum end cap 1 and the lower molybdenum end cap 3. The end of the molybdenum support rod 5 near the upper molybdenum end cap 1 is fixed to the upper molybdenum end cap 1 by resistance welding, and the end of the molybdenum support rod 5 near the lower molybdenum end cap 3 is fixed to the lower molybdenum end cap 3 by resistance welding to form a support assembly.

[0111] S4. Place the filament 6 between the upper molybdenum end cap 1 and the lower molybdenum end cap 3 of the support assembly. One end of the filament 6 is brazed to the upper molybdenum end cap 1 through the first solder layer 2, and the other end of the filament 6 is brazed to the lower molybdenum end cap 3 through the second solder layer 4, thus obtaining the magnetron cathode assembly. During the brazing process, the temperature is controlled at 1200-1600℃ and the time is controlled at 2-10s; preferably, the temperature is controlled at 1300-1500℃ and the time is controlled at 3-6s.

[0112] The following section provides further explanation of this application in conjunction with specific experiments.

[0113] Preparation Example

[0114]

Preparation Example 1

[0115] A modified epoxy resin, the preparation method of which includes the following steps:

[0116] a. Under nitrogen protection, 500 kg of bisphenol A epoxy resin E44, 125 kg of hydroxyl-terminated polydimethylsiloxane, and 0.02 kg of tetramethylammonium chloride were uniformly mixed, and then the mixture was heated to 135 °C and reacted for 1.5 h to obtain intermediate product I.

[0117] b. Dissolve 4 kg of rosin in 100 kg of xylene to obtain a rosin solution;

[0118] c. Add 20 kg of rosin solution to intermediate product I, control the temperature at 95 °C, and react for 2.5 h to obtain modified epoxy resin.

[0119] The viscosity of the double-hydroxyl-terminated polydimethylsiloxane is 30 cs.

[0120] Rosin has a melting point of 74℃.

[0121]

Preparation Example 2

[0122] A modified epoxy resin, the preparation method of which includes the following steps:

[0123] a. Under nitrogen protection, 500 kg of bisphenol A epoxy resin E44, 125 kg of polypropylene glycol diglycidyl ether, and 0.02 kg of tetramethylammonium chloride were mixed evenly, and then the temperature was raised to 135°C and reacted for 1.5 h to obtain intermediate product II.

[0124] b. Dissolve 4 kg of rosin in 100 kg of xylene to obtain a rosin solution;

[0125] c. Add 20 kg of rosin solution to intermediate product II, control the temperature at 95 °C, and react for 2.5 h to obtain modified epoxy resin.

[0126] Among them, polypropylene glycol diglycidyl ether is a product of Greenview Biotechnology with the model number CB2311.

[0127] Rosin has a melting point of 74℃.

[0128]

Preparation Example 3

[0129] A modified epoxy resin, the preparation method includes the following steps:

[0130] a. Under nitrogen protection, 500 kg of bisphenol A epoxy resin E44, 50 kg of hydroxyl-terminated polydimethylsiloxane, 75 kg of polypropylene glycol diglycidyl ether, and 0.02 kg of tetramethylammonium chloride were mixed evenly, and then the mixture was heated to 135 °C and reacted for 1.5 h to obtain intermediate product III.

[0131] b. Add 20 kg of monoacid to intermediate product III, control the temperature at 95℃, and react for 2.5 h to obtain modified epoxy resin.

[0132] The viscosity of the double-hydroxyl-terminated polydimethylsiloxane is 30 cs.

[0133] Polypropylene glycol diglycidyl ether is a product of Greenview Biotechnology, model number CB2311.

[0134]

Preparation Example 4

[0135] A modified epoxy resin, the preparation method includes the following steps:

[0136] a. Under nitrogen protection, 500 kg of bisphenol A epoxy resin E44, 50 kg of hydroxyl-terminated polydimethylsiloxane, 75 kg of polypropylene glycol diglycidyl ether, and 0.02 kg of tetramethylammonium chloride were mixed evenly, and then the mixture was heated to 135 °C and reacted for 1.5 h to obtain the intermediate product.

[0137] b. Dissolve 4 kg of rosin in 100 kg of xylene to obtain a rosin solution;

[0138] c. Add 20 kg of rosin solution to the intermediate product, control the temperature at 95 °C, and react for 2.5 h to obtain the modified epoxy resin.

[0139] The viscosity of the double-hydroxyl-terminated polydimethylsiloxane is 30 cs.

[0140] Polypropylene glycol diglycidyl ether is a product of Greenview Biotechnology, model number CB2311.

[0141] Rosin has a melting point of 74℃.

[0142]

Preparation Example 5

[0143] A modified epoxy resin, which differs from [Preparation Example 4] in that:

[0144] Polypropylene glycol diglycidyl ether was replaced by an equal amount of 1,4-butanediol diglycidyl ether.

[0145]

Preparation Example 6

[0146] A modified epoxy resin differs from [Preparation Example 4] in that 75 kg of polypropylene glycol diglycidyl ether is replaced by 10 kg of 1,4-butanediol diglycidyl ether and 65 kg of polypropylene glycol diglycidyl ether.

[0147]

Preparation Example 7

[0148] A modified epoxy resin differs from [Preparation Example 4] in that 75 kg of polypropylene glycol diglycidyl ether is replaced by 60 kg of 1,4-butanediol diglycidyl ether and 15 kg of polypropylene glycol diglycidyl ether.

[0149] Example

[0150] [Examples 1-5]

[0151] A solder is prepared from tungsten, molybdenum, and nickel. The proportions of the solder in Examples 1-5 are shown in Table 1 below.

[0152] Table 1. Solder proportions in Examples 1-5

[0153]

[0154] The preparation methods of the solder in Examples 1-5 are as follows:

[0155] (1) First, the planetary ball mill is evacuated to remove the air inside, and then Ar is introduced for 3 minutes to replace it.

[0156] (2) Tungsten, molybdenum and nickel were added to a planetary ball mill and mixed and milled under Ar protection according to the specified ratio. The ball-to-material ratio was 10:1, the ball milling speed was 1650 rpm, and the ball milling time was 10 h.

[0157] (3) After ball milling, the solder is obtained by passing it through a 10,000-mesh sieve under vacuum or inert gas protection.

[0158]

Examples 6-21

[0159]

Example 6

[0160] A solder paste comprising the following raw materials:

[0161] Solder: 100kg; wherein, the solder is specifically the solder prepared in [Example 1].

[0162] Organic carrier: 5 kg; wherein, the organic carrier is made from 60 kg of bisphenol A epoxy resin E44, 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether and 35 kg of rheology modifier polyamide wax.

[0163] Solvent: 5 kg; wherein the solvent is prepared by 8 kg of butyl acetate and 2 kg of xylene.

[0164] In this embodiment, the method for preparing the solder slurry includes the following steps:

[0165] Preparation of the organic carrier: Bisphenol A epoxy resin E44 and epoxy resin diluent 1,4-butanediol diglycidyl ether were mixed according to the specified ratio. The mixture was stirred mechanically for 15 minutes at a speed of 500 rpm to ensure thorough mixing. Then, rheology modulator polyamide wax was added in proportion, and the mixture was stirred mechanically for 15 minutes at a speed of 500 rpm to form the organic carrier.

[0166] Preparation of solder slurry: Add the organic carrier to the solder according to the specified ratio, then add solvent and stir; the stirring speed is 1000 r / min and the stirring time is 15 min to obtain the solder slurry. At the beginning of stirring, add 0.1% by weight of dimethylsilane modified defoamer emulsion of the solder to defoam.

[0167]

Example 7

[0168] A solder paste comprising the following raw materials:

[0169] Solder: 100kg; wherein, the solder is specifically the solder prepared in [Example 1].

[0170] Organic carrier: 10 kg; wherein, the organic carrier is made from 60 kg of bisphenol A epoxy resin E44, 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether and 35 kg of rheology modifier polyamide wax.

[0171] Solvent: 18 kg; wherein the solvent is prepared by 8 kg of butyl acetate and 2 kg of xylene.

[0172] In this embodiment, the preparation method of the solder slurry is the same as that in [Example 6].

[0173]

Example 8

[0174] A solder paste comprising the following raw materials:

[0175] Solder: 100kg; wherein, the solder is specifically the solder prepared in [Example 1].

[0176] Organic carrier: 15 kg; wherein, the organic carrier is made from 60 kg of bisphenol A epoxy resin E44, 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether and 35 kg of rheology modifier polyamide wax.

[0177] Solvent: 20 kg; wherein the solvent is prepared by 8 kg of butyl acetate and 2 kg of xylene.

[0178] In this embodiment, the preparation method of the solder slurry is the same as that in [Example 6].

[0179]

Example 9

[0180] A solder paste, which differs from [Example 7] in that:

[0181] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 1], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0182]

Example 10

[0183] A solder paste, which differs from [Example 7] in that:

[0184] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 2], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0185]

Example 11

[0186] A solder paste, which differs from [Example 7] in that:

[0187] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 3], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0188]

Example 12

[0189] A solder paste, which differs from [Example 7] in that:

[0190] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 4], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0191]

Example 13

[0192] A solder paste, which differs from [Example 7] in that:

[0193] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 5], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0194]

Example 14

[0195] A solder paste, which differs from [Example 7] in that:

[0196] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 6], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0197]

Example 15

[0198] A solder paste, which differs from [Example 7] in that:

[0199] The organic carrier was prepared from 60 kg of the modified epoxy resin obtained in [Preparation Example 7], 5 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 35 kg of rheology modifier polyamide wax.

[0200]

Example 16

[0201] A solder paste, which differs from [Example 15] in that:

[0202] The organic carrier was prepared from 80 kg of the modified epoxy resin obtained in [Preparation Example 7], 12 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 60 kg of rheology modifier polyamide wax.

[0203]

Example 17

[0204] A solder paste, which differs from [Example 15] in that:

[0205] The organic carrier was prepared from 90 kg of the modified epoxy resin obtained in [Preparation Example 7], 15 kg of epoxy resin diluent 1,4-butanediol diglycidyl ether, and 65 kg of rheology modifier polyamide wax.

[0206]

Examples 18-21

[0207] A solder slurry differs from that in [Example 16] in that the solder is different. The solders used in Examples 18-21 are shown in Table 2 below.

[0208] Table 2. Solder corresponding to Examples 18-21

[0209] Example Example 18 Example 19 Example 20 Example 21 solder Example 2 Example 3 Example 4 Example 5

[0210] Comparative Example

[0211] Comparative Example 1

[0212] One type of solder differs from Example 1 in that its raw material composition is different.

[0213] In this comparative example, tungsten weighed 18 kg, molybdenum weighed 72 kg, and nickel weighed 10 kg.

[0214] Comparative Example 2

[0215] One type of solder differs from Example 1 in that its raw material composition is different.

[0216] In this comparative example, tungsten weighs 45 kg, molybdenum weighs 45 kg, and nickel weighs 10 kg.

[0217] Comparative Example 3

[0218] A solder paste, which differs from [Example 6] in that:

[0219] The solder is specifically the solder prepared in [Comparative Example 1].

[0220] Comparative Example 4

[0221] A solder paste, which differs from [Example 6] in that:

[0222] The solder is specifically the solder prepared in [Comparative Example 2].

[0223] Application examples

[0224]

Application Example 1

[0225] A magnetron cathode assembly, the preparation method of which includes the following steps:

[0226] S1. The solder slurry of [Example 6] is applied to the first groove 11 of the upper molybdenum end cap 1 and the second groove 31 of the lower molybdenum end cap 3 using an automatic coating method. After the solder slurry is cured, the end caps coated with solder slurry are pre-sintered in a reducing atmosphere. The pre-sintering temperature is 650°C and the pre-sintering time is 2 hours. The amount of solder slurry in the first groove 11 and the second groove 31 is controlled at 10 mg. The reducing atmosphere is preferably a hydrogen atmosphere, and the hydrogen flow rate is controlled at 2.5 Nm3 / h.

[0227] S2. The pre-sintered upper molybdenum end cap 1 and lower molybdenum end cap 3 are subjected to high-temperature sintering at a temperature of 1500℃ and a sintering time of 1.5h, thereby forming a first solder layer 2 in the first groove 11 of the upper molybdenum end cap 1 and a second solder layer 4 in the second groove 31 of the lower molybdenum end cap 3.

[0228] S3. Place the molybdenum support rod 5 between the upper molybdenum end cap 1 and the lower molybdenum end cap 3. The end of the molybdenum support rod 5 near the upper molybdenum end cap 1 is fixed to the upper molybdenum end cap 1 by resistance welding, and the end of the molybdenum support rod 5 near the lower molybdenum end cap 3 is fixed to the lower molybdenum end cap 3 by resistance welding to form a support assembly.

[0229] S4. Place the thorium-tungsten filament 6 between the upper molybdenum end cap 1 and the lower molybdenum end cap 3 of the support assembly. The end of the thorium-tungsten filament 6 near the upper molybdenum end cap 1 is brazed to the upper molybdenum end cap 1 through the first solder layer 2. The end of the thorium-tungsten filament 6 near the lower molybdenum end cap 3 is brazed to the lower molybdenum end cap 3 through the second solder layer 4, thus obtaining the magnetron cathode assembly. During the brazing process, the temperature is controlled at 1200℃ and the time is controlled at 10s.

[0230]

Application Example 2

[0231] A magnetron cathode assembly differs from [Application Example 1] in that the parameters for the brazing process are different.

[0232] In this application example, the temperature is controlled at 1600℃ and the time is controlled at 2s during the brazing process.

[0233]

Application Example 3

[0234] A magnetron cathode assembly differs from [Application Example 1] in that:

[0235] The solder slurry used in step S1 is the solder slurry prepared in [Example 7].

[0236]

Application Example 4

[0237] A magnetron cathode assembly differs from [Application Example 1] in that:

[0238] The solder slurry used in step S1 is the solder slurry prepared in [Example 8].

[0239]

Application Example 5

[0240] A magnetron cathode assembly differs from [Application Example 1] in that:

[0241] The solder slurry used in step S1 is the solder slurry prepared in [Example 9].

[0242]

Application Example 6

[0243] A magnetron cathode assembly differs from [Application Example 1] in that:

[0244] The solder slurry used in step S1 is the solder slurry prepared in [Example 10].

[0245]

Application Example 7

[0246] A magnetron cathode assembly differs from [Application Example 1] in that:

[0247] The solder slurry used in step S1 is the solder slurry prepared in [Example 11].

[0248]

Application Example 8

[0249] A magnetron cathode assembly differs from [Application Example 1] in that:

[0250] The solder slurry used in step S1 is the solder slurry prepared in [Example 12].

[0251]

Application Example 9

[0252] A magnetron cathode assembly differs from [Application Example 1] in that:

[0253] The solder slurry used in step S1 is the solder slurry prepared in [Example 13].

[0254]

Application Example 10

[0255] A magnetron cathode assembly differs from [Application Example 1] in that:

[0256] The solder slurry used in step S1 is the solder slurry prepared in [Example 14].

[0257]

Application Example 11

[0258] A magnetron cathode assembly differs from [Application Example 1] in that:

[0259] The solder slurry used in step S1 is the solder slurry prepared in [Example 15].

[0260]

Application Example 12

[0261] A magnetron cathode assembly differs from [Application Example 1] in that:

[0262] The solder slurry used in step S1 is the solder slurry prepared in [Example 16].

[0263]

Application Example 13

[0264] A magnetron cathode assembly differs from [Application Example 1] in that:

[0265] The solder slurry used in step S1 is the solder slurry prepared in [Example 17].

[0266]

Application Example 14

[0267] A magnetron cathode assembly differs from [Application Example 1] in that:

[0268] The solder slurry used in step S1 is the solder slurry prepared in [Example 18].

[0269]

Application Example 15

[0270] A magnetron cathode assembly differs from [Application Example 1] in that:

[0271] The solder slurry used in step S1 is the solder slurry prepared in [Example 19].

[0272]

Application Example 16

[0273] A magnetron cathode assembly differs from [Application Example 1] in that:

[0274] The solder slurry used in step S1 is the solder slurry prepared in [Example 20].

[0275]

Application Example 17

[0276] A magnetron cathode assembly differs from [Application Example 1] in that:

[0277] The solder slurry used in step S1 is the solder slurry prepared in [Example 21].

[0278] Comparative Application Examples

[0279]

Comparative Application Example 1

[0280] A magnetron cathode assembly differs from [Application Example 2] in that:

[0281] The solder slurry used in step S1 is the same solder slurry prepared in [Comparative Example 1].

[0282]

Comparative Application Example 2

[0283] A magnetron cathode assembly differs from [Application Example 2] in that:

[0284] The solder slurry used in step S1 is the same solder slurry prepared in [Comparative Example 2].

[0285]

Comparative Application Example 3

[0286] A magnetron cathode assembly differs from [Comparative Application Example 1] in that:

[0287] In this application example, the temperature is controlled at 2100℃ and the time is controlled at 2s during the brazing process.

[0288] Performance testing

[0289] 1. Solder Retention Rate in Molybdenum End Caps: 200 upper and 200 lower molybdenum end caps (before pre-firing) with cured solder colloid were randomly selected from Application Examples 1-17 and Comparative Application Examples 1-3. The solder layer in the upper and lower molybdenum end caps was tested for detachment. The percentage of upper molybdenum end caps with detached first solder layer and the percentage of upper molybdenum end caps with detached second solder layer in the total sample of lower molybdenum end caps were recorded. Each application example and comparative application example was sampled three times, and the average results are recorded in Table 3 below.

[0290] Average retention rate of top molybdenum end cap solder = 100 - average number of top molybdenum end caps with solder layer detachment / 200 * 100;

[0291] Average retention rate of lower molybdenum end cap solder = 100 - average number of lower molybdenum end caps with solder layer detachment / 200 * 100.

[0292] 2. Magnetron Cathode Assembly Welding Defect Rate: 1000 magnetron cathode assemblies were randomly selected from Application Examples 1-17 and Comparative Application Examples 1-3 to check for issues such as incomplete soldering and detachment. Incomplete soldering and detachment were considered defective products. Three samples were taken from each application example and comparative application example, from different batches. The average welding defect rate of the magnetron cathode assemblies from the three measurements was calculated and recorded in Table 3 below. Average Welding Defect Rate = (Average Number of Incomplete Solderings + Average Number of Defective Solderings) / 1000 * 100.

[0293] 3. Bubbling Rate of Molybdenum End Caps in Magnetron Cathode Components: 1000 magnetron cathode components were randomly selected from Application Examples 1-17 and Comparative Application Examples 1-3. The molybdenum end caps of the magnetron cathode components were checked for bubbling issues. If even one molybdenum end cap in a magnetron cathode component showed bubbling, it was included in the bubbling list. The average bubbling rate of molybdenum end caps for the magnetron cathode components obtained from different application examples and comparative application examples is recorded in Table 3 below. Average bubbling rate of molybdenum end caps = Average number of molybdenum end cap bubbles / 1000 * 100.

[0294] Table 3

[0295]

[0296]

[0297]

[0298] The difference between Comparative Application Examples 1-2 and Application Example 2 lies in the different proportions of tungsten, molybdenum, and nickel in the solder. Specifically, the molybdenum to nickel ratio in Comparative Application Example 1 is outside the scope of protection claimed in this application, as is the tungsten to nickel ratio in Comparative Application Example 2. Based on the data in Table 3, it can be seen that the solder retention rate in the molybdenum end cap in Comparative Application Examples 1-2 is not significantly different from that in Application Example 2, nor is the blistering rate of the molybdenum end cap. However, the welding defect rate of the magnetron cathode assembly is significantly increased. This indicates that at a brazing temperature of 1600℃, the molybdenum end cap is less prone to blistering. However, when the solder layer prepared using the solder and organic carrier from Comparative Application Examples 1-2 is used to braze the filament and molybdenum end cap at this temperature, the brazing quality is poor. The reason is that the solder in Comparative Application Example 1 and Comparative Application Example 2 has a high melting point, which makes it impossible to achieve rapid melting of the solder at 1600℃, resulting in poor brazing quality between the filament and the molybdenum end cap.

[0299] The difference between Comparative Application Example 1 and Comparative Application Example 3 is that the brazing temperature of the filament and molybdenum end cap in Comparative Application Example 3 was adjusted to 2100℃. According to the data in Table 3, increasing the brazing temperature significantly reduced the welding defect rate between the filament and molybdenum end cap. However, the increased brazing temperature also significantly increased the bubbling rate of the molybdenum end cap, which is detrimental to improving the finished product yield of the magnetron cathode assembly.

[0300] The difference between Application Examples 5-8 and Application Example 3 lies in the selection of the epoxy resin in the organic carrier. As shown in Table 3, the modified epoxy resin used in the organic carrier, obtained by modifying bisphenol A epoxy resin with hydroxyl-terminated polydimethylsiloxane, polypropylene glycol diglycidyl ether, and rosin, effectively improves the solder retention rate in the molybdenum end cap, reduces the occurrence of end cap debonding, and plays an important role in reducing rework rates and improving production efficiency. The lack of any one of the following—polydimethylsiloxane with active group end capping, ether monomer with diepoxy group end capping, and rosin—prevents the solder retention rate of the molybdenum end cap from exceeding 80%. The inventors analyzed that the reason is that polydimethylsiloxane with active group end capping, ether monomer with diepoxy group end capping, and rosin have a synergistic effect on improving the adhesion strength between the modified epoxy resin and the molybdenum end cap. The three together improve the adhesion performance between the modified epoxy resin and the molybdenum end cap, making the solder colloid obtained after the solder slurry cures less likely to fall off the molybdenum end cap.

[0301] The difference in Application Examples 8-11 lies in the composition of the diepoxy-terminated ether monomers. Referring to the data in Table 3, it can be seen that when the diepoxy-terminated ether monomer is a combination of 1,4-butanediol diglycidyl ether and polypropylene glycol diglycidyl ether, and the weight ratio of 1,4-butanediol diglycidyl ether to polypropylene glycol diglycidyl ether is in the range of (3-4):1, the risk of solder detaching from the molybdenum end cap can be further reduced. This is because when the diepoxy-terminated ether monomer is selected in the above combination, the solder slurry has moderate fluidity and a moderate curing speed. This can improve the problem of poor solder adhesion and easy detachment caused by excessively slow curing speed, and also improve the problem of poor solder adhesion and easy detachment caused by excessively fast curing speed, where the solder slurry solidifies before fully wetting the molybdenum end cap.

[0302] The difference between Application Examples 12 and 14-17 lies in the raw materials and composition of the solder, but they are all within the scope of protection claimed in this application. They can achieve good brazing results at 1200℃ and effectively reduce the blistering rate of molybdenum end caps.

[0303] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A solder paste, characterized by: The solder is prepared by 20-30wt% tungsten, 40-50wt% molybdenum and the rest of nickel; the particle size of the tungsten is 10-20μm, the particle size of the molybdenum is 10-20μm, and the particle size of the nickel is 40-50μm. The organic carrier includes epoxy resin, epoxy resin diluent and rheological agent, and the weight ratio of the epoxy resin, the epoxy resin diluent and the rheological agent is (60-90):(5-15):(35-65); The epoxy resin is selected from modified epoxy resin, and the modified epoxy resin includes the following raw materials by weight: Bisphenol A epoxy resin: 500 parts; Active group terminated polydimethylsiloxane: 40-60 parts; Double epoxy group terminated ether monomer: 70-80 parts; Catalyst: 0.01-0.03 parts; Rosin solution with a mass concentration of 3-5wt%: 20-30 parts; The active group in the active group terminated polydimethylsiloxane is hydroxyl or amino; The double epoxy group terminated ether monomer is a combination of 1,4-butanediol diglycidyl ether and polypropylene glycol diglycidyl ether with a weight ratio of (3-4):1; The preparation method of the modified epoxy resin includes the following steps: Under the protection of nitrogen, the bisphenol A epoxy resin, the active group terminated polydimethylsiloxane, the double epoxy group terminated ether monomer and the catalyst are uniformly mixed, then the temperature is raised to 130-140℃, and the reaction is carried out for 1-2h to obtain an intermediate product; 3-5 parts of rosin is dissolved in 100 parts of dimethylbenzene to obtain a rosin solution with a mass concentration of 3-5wt%; The rosin solution with a mass concentration of 3-5wt% is added to the intermediate product, the temperature is controlled at 90-100℃, and the reaction is carried out for 2-3h to obtain the modified epoxy resin; The solder is prepared by 20-30wt% tungsten, 40-50wt% molybdenum and the rest of nickel; the particle size of the tungsten is 10-20μm, the particle size of the molybdenum is 10-20μm, and the particle size of the nickel is 40-50μm.

2. The solder paste of claim 1, wherein: The preparation method of the solder includes the following steps: Under the protection of inert gas, the tungsten, the molybdenum and the nickel are mixed and ball milled according to the proportion, wherein the ball material ratio is (5-15):1, the ball milling speed is 1500-1800rpm, and the ball milling time is 10-40h; After the ball milling is completed, the metal powder is sieved under vacuum or inert gas protection to obtain the solder.

3. A solder paste according to any one of claims 1-2, characterized in that: The solder paste further includes a defoaming agent, and the weight of the defoaming agent is 0.1-1% of the weight of the solder.

4. A magnetron cathode assembly characterized by: It includes: The upper molybdenum end cap (1) is provided with a first solder layer (2), and the first solder layer (2) is obtained by sintering the solder paste of any one of claims 1-3; The lower molybdenum end cap (3) is provided with a second solder layer (4), and the second solder layer (4) is obtained by sintering the solder paste of any one of claims 1-3; The molybdenum support rod (5) is used to connect the upper molybdenum end cap (1) and the lower molybdenum end cap (3); The filament (6) is fixed by brazing at one end through the first solder layer (2) of the upper molybdenum end cap (1), and is fixed by brazing at the other end through the second solder layer (4) of the lower molybdenum end cap (3).

5. The method for preparing a magnetron cathode assembly according to claim 4, characterized in that: It includes the following steps: The solder paste according to any one of claims 1-3 is coated on the upper molybdenum end cap (1) and the lower molybdenum end cap (3), and the upper molybdenum end cap (1) and the lower molybdenum end cap (3) coated with the solder paste are pre-sintered in a reducing atmosphere, the pre-sintering temperature is 500-850°C, and the pre-sintering time is 1-6h; The pre-sintered upper molybdenum end cap (1) and the lower molybdenum end cap (3) are high-temperature sintered, the high-temperature sintering temperature is 1400-1600°C, and the sintering time is 0.1-3.5h, so as to form the first solder layer (2) on the upper molybdenum end cap (1) and the second solder layer (4) on the lower molybdenum end cap (3); The molybdenum support rod (5) is resistance-welded with the upper molybdenum end cap (1) and the lower molybdenum end cap (3) to form a support assembly; The filament (6) is arranged between the upper molybdenum end cap (1) and the lower molybdenum end cap (3), one end of the filament (6) is fixed by brazing with the upper molybdenum end cap (1) through the first solder layer (2), and the other end of the filament (6) is fixed by brazing with the second solder layer (4) and the lower molybdenum end cap (3) through the second solder layer (4), so as to obtain a magnetron cathode assembly; wherein, during the brazing process, the temperature is controlled at 1200-1600°C, and the time is controlled at 2-10s.

6. A method of making a magnetron cathode assembly according to claim 5, wherein: During the brazing process, the temperature is controlled at 1300-1500°C, and the time is controlled at 3-6s.

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