Silver-based multi-component near-eutectic medium-temperature vacuum brazing filler and preparation method thereof

Abstract

The present application relates to a kind of silver-based multielement near-eutectic medium-temperature vacuum brazing filler metal and its preparation method, belong to non-ferrous metal brazing field.The brazing filler metal includes: Cu 19.5~21.0wt%, In 9.0~10.0wt%, Ge 4.5~5.5wt%, Sn 4.2~4.8wt%, Ni 1.8~2.2wt%, Si 1.7~2.0wt%, Co 0.05~0.2wt%, Ag is remainder by weight percentage calculation.Its preparation method includes intermediate alloy preparation, vacuum medium-frequency induction melting, centrifugal speed cooling casting, vacuum heat treatment regulation, hot rolling breakdown, surface treatment, precision cold rolling.The alloy melting point is low, and the required vacuum brazing temperature is low, and it has excellent wetting characteristics for stainless steel, and the joint strength is high after brazing, satisfies the vacuum electronic device 316L stainless steel substrate medium-temperature vacuum brazing packaging, gradient brazing and repair welding needs.

Description

TECHNICAL FIELD

[0001] The present application relates to a silver-based multi-element near-eutectic medium-temperature solder and a preparation method thereof, and mainly solves the problem of medium-temperature vacuum brazing of 316L stainless steel base material in a vacuum electronic device, and belongs to the field of non-ferrous metal brazing. BACKGROUND

[0002] A vacuum electronic device is a device for transmitting and converting optical or electrical signals (energy), and has a wide range of applications in key fields such as national defense industry, power grid energy, medical science, etc. The vacuum electronic device is a component connected by welding of many metal and non-metal materials. Since the internal ultra-high vacuum needs to be ensured for a long time during the operation of the device, the physical properties of the brazing and packaging materials have high standard requirements. Silver solder has high thermal and electrical conductivity and excellent brazing performance, and has been the main packaging material in the field of vacuum electronic device manufacturing. The common silver solder is mainly Ag-28Cu eutectic alloy, which has good brazing properties for copper, nickel and other metals, and the solid-liquid phase temperature is 779℃. With the complexity of the shape of the device and the diversification of the application environment, some materials such as Kovar and stainless steel are required for the structure of the vacuum electronic device, and the structure needs to be brazed in stages, which involves silver-based solder with different melting points and brazing temperatures. At present, the mature silver-based solder mainly includes AgCuPd series (810-900℃), AgCuNi series (780-830℃), AgCuIn series (600-710℃), AgCuSn series (630-720℃), etc. The mature products of silver-based medium-temperature solder with a melting point lower than 600℃ and a brazing temperature lower than 630℃ are basically blank.

[0003] 316L stainless steel has excellent corrosion resistance, and is widely used in aerospace, radar electronics, new energy and other fields. 316L stainless steel has become the preferred material for key parts of vacuum electronic devices, but it contains a high content of Cr (16.00-18.00wt%), a small amount of Mo (2.00-3.00wt%) and a small amount of Ti element, and has a complex oxide film (TiOx, Cr2O3, MoO) on the surface. When vacuum brazing with silver-based filler metal, the temperature often needs to exceed 900°C. Commonly used AgCuIn28-10, AgCuSn30-10, AgCuInSn22-13-7 and other silver-based medium-temperature filler metals cannot wet 316L stainless steel at a temperature lower than 700°C in a vacuum environment, resulting in metallurgical results. Although the AgCuInSnNi series filler metal reported in the literature can wet 316L stainless steel at 700°C, the metallurgical bonding is weak, and the strength of the brazed joint is less than 80MPa. AgCuGeSnNi24-25-4-0.1 filler metal can braze 316L stainless steel at 680°C in a vacuum environment, but the material is difficult to process into foil and strip due to its poor plasticity, and the joint strength is also less than 100MPa due to the presence of a large amount of Ge. The material has a high vapor pressure and cannot meet the requirements of vacuum electronic devices. Other silver-based medium-temperature filler metals such as AgCuZn cannot be used in a vacuum environment.

[0004] Based on the above analysis of the surface of 316L stainless steel, the main oxidation film contains Cr, Mo and Ti, and the metallurgical mechanism is basically to break the oxidation film on the surface of 316L stainless steel and form a metallurgical reaction with basic Fe, Ni and Cr elements to generate a bonding layer. First of all, considering the application scenario and cost of vacuum electronic devices, as well as the solid phase temperature of the upper level filler metal of the vacuum electronic device, which is 680°C, the brazing temperature of the designed filler metal is required to be lower than 650°C. Secondly, the vacuum electronic device needs to be baked at 500°C for a long time, and the melting point of the filler metal needs to be higher than 530°C, so the melting point of the filler metal needs to be designed between 550-600°C, preferably eutectic solder. SUMMARY

[0005] Therefore, in order to solve the above technical problems, the present application designs and develops a medium-temperature high-strength silver-based alloy vacuum solder with a melting point of 550-600°C and a brazing temperature of about 630°C, which has good metallurgical effect for medium-temperature vacuum brazing of 316L stainless steel, and can meet the requirements of high reliability, high strength, good airtightness and long-term baking service of vacuum electronic device connection.

[0006] The main purpose of the present application is to provide a silver-based multi-element near-eutectic medium-temperature vacuum solder, the eutectic melting point of which is 552-562 DEG C, and the recommended soldering temperature is 630 DEG C (316L stainless steel), which mainly solves the medium-temperature vacuum soldering packaging of 316L stainless steel in vacuum electronic devices, and has the advantages of high strength after welding, low vapor pressure, good airtightness, and excellent wettability on Cu, Ni, Kovar alloy and other stainless steel substrates.

[0007] Another purpose of the present application is to provide a preparation method of the silver-based multi-element near-eutectic medium-temperature vacuum solder. The preparation method and process flow are used to solve the difficult problem of forming brittle materials of silver-based medium-temperature alloys, and can prepare very thin foil strip materials meeting the industrial needs, and the prepared foil strip alloy has uniform composition, consistent grain orientation, small IMC, clean surface, high material yield, and can be processed into any preformed products, meeting the multi-level packaging requirements of vacuum electronic devices for vacuum solder.

[0008] To achieve the above purpose, the present application adopts the following design scheme:

[0009] A silver-based multi-element near-eutectic medium-temperature vacuum solder, which comprises, by weight percentage: Cu 19.5-21.0wt%, In 9.0-10.0wt%, Ge 4.5-5.5wt%, Sn 4.2-4.8wt%, Ni 1.8-2.2wt%, Si 1.7-2.0wt%, Co 0.05-0.2wt%, and Ag is the balance.

[0010] The silver-based multi-element near-eutectic medium-temperature vacuum solder has a near-eutectic melting point of 552-562 DEG C.

[0011] The main innovation of the present application is to design a kind of middle-low temperature high-strength silver-based alloy vacuum solder for 316L stainless steel vacuum brazing at medium temperature, the main design idea is based on Ag-28Cu eutectic, by eliminating high vapor pressure elements: Zn, Cd, Ga, etc., selecting to add In, Sn, Ge, etc., by studying AgCuInSn, AgCuGeSnNi, etc., it is found that the alloy will appear 480-490 DEG C low melting point phase when the content of In element is more than 10%, therefore, the content of In is controlled within 10%, and the addition of In is beneficial to increase the wetting power of the solder in vacuum; The design of adding Ge element not only has the effect of reducing melting, but also is beneficial to the breaking of the oxide film on the surface of 316L stainless steel in vacuum environment, but the solid solubility of Ge in Cu element is limited, and more than 10%, a large amount of intermetallic compounds will be precipitated, which will affect the plasticity of the alloy, further experiments show that when the content of Ge element is 4.5-5.5wt%, it can ensure the existence of Cu solid solution and the effective film breaking effect in the brazing process. The design of adding Sn element can further reduce the melting point of the alloy, in order to avoid the large amount of CuSn intermetallic compounds and low melting point phase, the content of Sn element needs to be controlled within 5.0wt%; In order to realize better metallurgical effect on 316L stainless steel and avoid the large production of CuTi intermetallic compounds at the reaction interface, Ni element is designed to be added, which can not only participate in the metallurgical reaction first and generate Ni-based solid solution at the interface, but also can refine the grain. Si element is used as a reducing element of self-fluxing agent, a small amount of Si element can reduce Cr2O3, and the vapor pressure of Si element is less than that of Li element, in order to improve the brazing activity and wettability of the alloy (to stainless steel), and form Ni3Si strengthening phase during brazing process to improve the strength of the solder, the content of Si element needs to be 1.7-2.0wt%; Considering that the strength of the solder itself determines the strength of the middle layer of the weld, through screening, a small amount of Co element is designed to be added, which can further refine the grain and improve the high temperature service performance of the solder, so as to ensure that the performance of the alloy does not decrease during long time baking, but the addition of Co element will cause the melting point to rise, therefore, the content of Co element needs to be controlled within 0.05-0.2wt%. It is also found that when the content of Cu element is high, the diffusion of Cu element to 316L base material during brazing process will cause intergranular corrosion problem, and when the content of Cu element is low, the metallurgical effect will decrease, therefore, the content of Cu element also needs to be strictly controlled within 19.5-21.0wt%, so as to ensure the existence of solid solution in the alloy and avoid the generation of intermetallic compounds.

[0012] A preparation method of a silver-based multi-element near-eutectic medium-temperature vacuum solder material, the method comprises the following steps:

[0013] (1) Selection of raw materials and preparation of intermediate alloy

[0014] According to the composition of the silver-based multi-element near-eutectic medium-temperature vacuum filler metal, Ag, Cu, In, Ge, Sn, Ni, Si and Co are used as raw materials;

[0015] The Ag-In intermediate alloy, the Cu-Sn intermediate alloy, the Cu-Ge intermediate alloy, the Cu-Ni intermediate alloy, the Cu-Si intermediate alloy and the Cu-Co intermediate alloy are prepared by vacuum medium-frequency induction melting.

[0016] (2) Vacuum medium-frequency induction melting

[0017] The intermediate alloy prepared in step (1) is weighed according to the weight percentage of each element of the silver-based multi-element near-eutectic medium-temperature vacuum filler metal; pure Ag, pure Cu and the intermediate alloy are put into an alumina crucible, the crucible is covered, and the furnace is vacuumized; heating is started, and high-purity argon is filled when the initial liquid phase is observed; the power is reduced for refining after the whole is in a molten state.

[0018] (3) Centrifugal rapid cooling casting

[0019] The molten alloy melt obtained in step (2) is filled into a horizontal graphite casting mold by rotating centrifugal force through centrifugal rapid cooling casting to obtain an alloy slab with uniform composition.

[0020] (4) Vacuum heat treatment for controlling crystal orientation

[0021] The alloy slab obtained in step (3) is subjected to crystal orientation control in a high-vacuum heat treatment furnace to obtain an alloy ingot with consistent grain orientation.

[0022] (5) Precision rolling

[0023] The alloy ingot prepared in step (4) is subjected to rough rolling by a hot rolling mill to obtain a strip, which is coiled; the strip is polished and ground on both sides to a silver bright color; the strip is subjected to multi-pass cold rolling by a cold rolling mill until a foil is obtained, which is coiled.

[0024] In step (1), the raw materials Ag, Cu, In, Ge, Sn, Ni, Si and Co are all high-purity, and the purity is 99.999% (wt. %).

[0025] In step (1), Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy and Cu-10Co intermediate alloy are prepared by vacuum medium frequency induction melting, wherein the content of In in Ag-In intermediate alloy is 20wt%, the rest is Ag; the content of Sn in Cu-Sn intermediate alloy is 50wt%, the rest is Cu; the content of Ge in Cu-Ge intermediate alloy is 40wt%, the rest is Sb; the content of Ni in Cu-Ni intermediate alloy is 20wt%, the rest is Cu; the content of Si in Cu-Si intermediate alloy is 20wt%, the rest is Cu; the content of Co in Cu-Co intermediate alloy is 10wt%, the rest is Cu.

[0026] In step (2), the melting method is vacuum medium frequency induction melting, the refining temperature is 650-700℃, and the refining time is 5-10min. When vacuum melting, the vacuum in the furnace is 10 -2 Pa or below, the heating power is 20-30kw, and after high-purity argon is filled, the vacuum in the furnace is 0.8MPa.

[0027] In step (3), the casting form is centrifugal pressure quick cooling casting, the centrifugal casting temperature is 650-700℃, and the centrifugal speed is 500-1000n / min. The thickness of the alloy slab is 10-15mm, and the width is 80-250mm.

[0028] In step (4), vacuum heat treatment is used to regulate the crystal orientation, the vacuum degree is <5.0x10 -3 Pa, the temperature is 520-530℃, and the holding time is 12-16h.

[0029] In step (5), the hot rolling machine is a 250 two-high reversible hot rolling machine, the rolling mill roller temperature is 420-450℃, and the hot rolling pass processing rate is 5%-10%; the cold rolling machine is a 50 type four-high reversible cold rolling machine, the intermediate vacuum annealing temperature is 480-500℃, the vacuum degree is 10 -2 Pa or below, the cold rolling pass processing rate is 15%-30% between annealing, and the tension size is 0-10kN.

[0030] In step (5), the thickness of the strip is 0.8-1.0mm, and the width is 80-250mm; the thickness of the foil is 0.05-0.1mm, and the width is 80-250mm.

[0031] The alloy composition of the solder and the silver-based multi-element near-eutectic medium-temperature vacuum solder foil prepared by the preparation method have the following advantages: the solder alloy has a near-eutectic melting point of 552-562 DEG C, and the recommended brazing temperature is 630 DEG C (316L stainless steel). The main problem solved by the silver-based multi-element near-eutectic medium-temperature vacuum solder foil is the brazing packaging of 316L stainless steel in a vacuum electronic device, and the brazing packaging has the advantages of high strength after brazing, low vapor pressure, good air tightness, excellent wettability on Cu, Ni, Kovar alloy and other stainless steel substrates, and the like. The silver-based multi-element near-eutectic medium-temperature vacuum solder foil meets the multi-level packaging requirements of a complex mechanism of a vacuum electronic device. The preparation method is "intermediate alloy preparation + vacuum medium-frequency induction melting + centrifugal pressure rapid cooling casting + vacuum heat treatment for regulating crystal orientation + hot rolling breakdown + surface polishing + precise cold rolling", which solves the problems of macroscopic composition segregation, coarse grains and inconsistent crystal orientation of the silver-based multi-element alloy, and inhibits the growth of brittle compounds and controls the consistent grain orientation during phase nucleation, thereby being suitable for batch stable production. The silver-based multi-element near-eutectic medium-temperature vacuum solder foil obtained by the preparation method has the advantages of uniform alloy composition, consistent grain orientation, small IMC, clean surface, high material yield and the like, and can be processed into any preformed product, thereby meeting the multi-level packaging requirements of a vacuum electronic device for a vacuum solder.

[0032] Advantages of the present application:

[0033] 1. The silver-based multi-element near-eutectic medium-temperature vacuum solder manufactured by the method solves the problem of brazing packaging of 316L stainless steel in a vacuum electronic device, and has the advantages of high strength after brazing, low vapor pressure, good air tightness and the like.

[0034] 2. The silver-based multi-element near-eutectic medium-temperature vacuum solder manufactured by the method has a low melting point of 552-562 DEG C, a short melting range and a near-eutectic melting point.

[0035] 3. The silver-based multi-element near-eutectic medium-temperature vacuum solder manufactured by the method has excellent brazing process performance, good wettability, high strength, excellent wettability on Cu, Ni, Kovar alloy and stainless steel substrates and the like.

[0036] 4. The silver-based multi-element near-eutectic medium-temperature vacuum solder manufactured by the method realizes interfacial metallurgical bonding with 316L stainless steel at a low brazing temperature, has a dense reaction layer and high strength after brazing, and has more practical application value than gold-based and aluminum-based solders at the same temperature range.

[0037] 5. The manufacturing process of the method is novel, and fundamentally solves the problems of macroscopic composition segregation, coarse grains and inconsistent crystal orientation in multi-element alloys, inhibits the growth of brittle compounds and controls the consistent grain orientation during phase nucleation, thereby being suitable for batch stable production.

[0038] 6, The preparation method is adopted to obtain foil strip alloy component uniformity, grain orientation consistency, IMC smallness, surface cleanliness, high material yield, and any preformed product processing, and meets the multi-stage packaging requirements of vacuum electronic devices on vacuum brazing filler.

[0039] The silver-based multi-component near-eutectic medium-temperature vacuum brazing filler is designed scientifically, the preparation process is reasonable, is a low-silver hard brazing material, the alloy melting point is 552-562 DEG C, and the recommended brazing temperature is 630 DEG C (316L stainless steel).

[0040] The brazing filler can be suitable for medium-temperature packaging of vacuum electronic devices. The brazing filler is a multi-component eutectic alloy, has moderate melting temperature, has excellent wettability on Cu, Ni, Kovar alloy and stainless steel base materials, and meets the medium-temperature vacuum brazing packaging requirements of 316L stainless steel materials in vacuum electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The differential thermal analysis spectrum of the silver-based multi-component near-eutectic medium-temperature vacuum brazing filler prepared in embodiment 1 of the application;

[0042] Figure 2 The joint microstructure electron microscope photo of the silver-based multi-component near-eutectic medium-temperature vacuum brazing filler prepared in embodiment 1 of the application brazing (6030 DEG C) 316L stainless steel base plate. DETAILED DESCRIPTION

[0043] The silver-based multi-component near-eutectic medium-temperature vacuum brazing filler and the preparation method thereof will be further described below by combining with the embodiment of specific ingredient calculation.

[0044] The silver-based multi-component near-eutectic medium-temperature vacuum brazing filler is composed of the following components in percentage by weight: Cu 19.5-21.0 wt%, In 9.0-10.0 wt%, Ge 4.5-5.5 wt%, Sn 4.2-4.8 wt%, Ni 1.8-2.2 wt%, Si 1.7-2.0 wt%, Co 0.05-0.2 wt%, and Ag is the balance, and the total amount of the above components is 100%.

[0045] The preparation method of the eutectic medium-temperature solder foil strip is obtained through intermediate alloy preparation, non-vacuum medium-frequency refining, fast cooling horizontal casting, isothermal rolling and the like, and comprises the following specific steps:

[0046] (1) Raw material selection and intermediate alloy preparation: the raw materials of Ag, Cu, In, Ge, Sn, Ni, Si and Co are all 99.999%. The vacuum medium-frequency induction melting mode is adopted to prepare Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy and Cu-10Co intermediate alloy respectively;

[0047] (2) Vacuum medium frequency induction melting: the intermediate alloy prepared in step (1) is weighed according to the weight percentage of each element in the silver-based multi-element near-eutectic medium-temperature vacuum solder, and the weight of each element and the weight of the intermediate alloy are calculated; the vacuum induction melting furnace is used to put the weighed pure Ag, pure Cu and intermediate alloy into the alumina crucible, cover it, and the vacuum in the furnace is extracted to 10 -2 Pa below; start heating, the heating power is 20-30 kw, and the initial liquid phase is observed from the observation port; high-purity argon is filled until the vacuum in the furnace is 0.8 MPa, and heating is continued until it is all molten liquid; the power is reduced, the refining temperature is controlled to be 650-700 ℃, and the temperature is maintained for 5-10 min.

[0048] (3) Centrifugal rapid cooling casting: the molten alloy melt obtained in step (2) is filled into a horizontal graphite casting mold by rotating centrifugal force through centrifugal rapid cooling casting, the centrifugal casting temperature is 650-700 ℃, the centrifugal speed is 500-1000 n / min, and an alloy slab with a thickness of 10-15 mm, a width of 80-250 mm and uniform composition is obtained.

[0049] (4) Vacuum heat treatment to control crystal orientation: the alloy slab obtained in step (3) is subjected to crystal orientation control in a high-vacuum heat treatment furnace, the vacuum degree is <5.0x10 -3 Pa, the temperature is 530 ℃, and the holding time is 12-16 h, and a grain-oriented alloy ingot is obtained.

[0050] (5) Precision rolling: the alloy ingot prepared in step (4) is subjected to blooming rough rolling by using a 250 two-high reversible hot rolling mill, the rolling mill roll temperature is 420-450 ℃, the hot rolling pass reduction is 5%-10%, a strip with a thickness of 0.8-1.0 mm and a width of 80-250 mm is obtained, and the strip is coiled; the strip is double-side polished and ground to silver color; a 50 four-high reversible cold rolling mill is used, the intermediate vacuum annealing temperature is 480-500 ℃, the vacuum degree is <10 -2 Pa, the cold rolling pass reduction is 15%-30% per annealing interval, the tension size is 0-10 kN, and multiple-pass cold rolling is performed until a foil with a thickness of 0.05-0.1 mm and a width of 80-250 mm is obtained, and the foil is coiled.

[0051] Example 1:

[0052] Step 1: Preparation of raw materials and intermediate alloy

[0053] According to the alloy composition of Example 1 in Table 1, prepare raw materials and weigh according to the designed component ratio, the total feeding amount of a single furnace is 100 kg, and Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy and Cu-10Co intermediate alloy are respectively prepared by using vacuum medium-frequency induction melting method;

[0054] Step (2) vacuum medium-frequency induction melting

[0055] According to the weight percentage of each element of the silver-based multi-element near-eutectic medium-temperature vacuum solder in step (1), the feeding weight of each element and the feeding weight of the intermediate alloy are calculated, as shown in Table 2; the vacuum induction melting furnace is used, the weighed pure Ag, pure Cu and intermediate alloy are all put into the alumina crucible, the cover is closed, the vacuum in the furnace is extracted to 10 -2 Pa or less; the heating is started, the heating power is 25 kw, and the initial liquid phase is observed from the observation port; high-purity argon is filled until the vacuum in the furnace is 0.8 MPa, and the heating is continued until all are molten liquid; the power is reduced, the refining temperature is controlled to be 680℃, and the maintaining is performed for 8 min.

[0056] Step (3) centrifugal rapid cooling casting

[0057] The molten alloy melt obtained in step (2) is used for centrifugal rapid cooling casting, the melt is filled into a horizontal graphite casting mold through the rotating centrifugal force, the centrifugal casting temperature is 680℃, the centrifugal speed is 800n / min, and the alloy slab with a thickness of 12 mm, a width of 150 mm and uniform composition is obtained.

[0058] Step (4) vacuum heat treatment for controlling crystal orientation

[0059] The alloy slab obtained in step (3) is subjected to crystal orientation organization control in a high vacuum heat treatment furnace, the vacuum degree is <5.0×10 -3 Pa, the temperature is 530℃, the maintaining time is 14 h, and the alloy ingot with consistent grain orientation is obtained.

[0060] Step (5) precision rolling

[0061] The alloy ingot prepared in step (4) is subjected to blooming rough rolling by using a 250 two-high reversible hot rolling mill, the rolling mill roll temperature is 430℃, the hot rolling pass reduction is 10%, the strip with a thickness of 1.0 mm and a width of 150 mm is obtained, and the strip is coiled; the strip is treated by double-side polishing and grinding to silver bright color; the 50 four-high reversible cold rolling mill is used, the intermediate vacuum annealing temperature is 490℃, the vacuum degree is 10 -2Pa and below, the cold rolling pass processing rate is 20%, the tension size is 5 kN, and multiple cold rolling passes are performed until a foil with a thickness of 0.05 mm and a width of 150 mm is obtained, which is coiled.

[0062] Example 2:

[0063] Step 1: Preparation of raw materials and intermediate alloy

[0064] According to the alloy composition of Example 2 in Table 1, the raw materials are prepared and weighed according to the designed component ratio. The total amount of raw materials for each furnace is 100 kg. Vacuum medium-frequency induction melting is used to prepare Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy, and Cu-10Co intermediate alloy, respectively.

[0065] Step (2) Vacuum medium-frequency induction melting

[0066] The intermediate alloy prepared in step (1) is weighed according to the weight percentage of each element in the silver-based multi-element near-eutectic medium-temperature vacuum solder. The weight of each element and the weight of the intermediate alloy are calculated and shown in Table 2. Pure Ag and pure Cu, as well as the intermediate alloy, are placed in an alumina crucible, covered, and the vacuum in the furnace is extracted to 10 -2 Pa and below; turn on the heating, the heating power is 30 kw, wait to see the initial liquid phase from the observation port, fill in high-purity argon gas, the vacuum in the furnace is 0.8 MPa, continue to heat to all molten liquid, reduce the power, control the refining temperature to 700℃, keep for 5 min.

[0067] Step (3) Centrifugal rapid cooling casting

[0068] The molten alloy melt obtained in step (2) is cast by centrifugal rapid cooling. The melt is filled into a horizontal graphite casting mold by rotating centrifugal force. The centrifugal casting temperature is 700℃, and the centrifugal speed is 500 n / min. An alloy slab with a thickness of 10 mm and a width of 80 mm and uniform composition is obtained.

[0069] Step (4) Vacuum heat treatment to control crystal orientation

[0070] The alloy slab obtained in step (3) is subjected to crystal orientation control in a high vacuum heat treatment furnace. The vacuum degree is <5.0×10 -3 Pa, the temperature is 530℃, and the holding time is 12 h. A grain-oriented alloy ingot is obtained.

[0071] Step (5) Precision rolling

[0072] The alloy ingot prepared in step (4) is subjected to roughing by using a 250 two-high reversing hot rolling mill, the roller temperature of the rolling mill is 450 DEG C, the hot rolling pass processing rate is 5%, a strip with a thickness of 0.8 mm and a width of 80 mm is obtained, and the strip is coiled; the strip is treated by double-side polishing and grinding to a silver bright color; a 50 four-high reversing cold rolling mill is used, the intermediate vacuum annealing temperature is 500 DEG C, the vacuum degree is 10 -2 Pa, the cold rolling pass processing rate is 15% per annealing interval, the tension size is 0 kN, and multiple passes of cold rolling are performed until a foil with a thickness of 0.1 mm and a width of 80 mm is obtained, and the foil is coiled.

[0073] Example 3

[0074] Step 1: Preparation of raw materials and preparation of intermediate alloy

[0075] According to the alloy composition of Example 3 in Table 1, the raw materials are prepared and weighed according to the designed component ratio, the total amount of raw materials for a single furnace is 100 kg, and the vacuum intermediate frequency induction melting method is used to prepare Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy, and Cu-10Co intermediate alloy, respectively;

[0076] Step (2) Vacuum intermediate frequency induction melting

[0077] The intermediate alloy prepared in step (1) is weighed according to the weight percentage of each element of the silver-based multi-element near-eutectic medium-temperature vacuum solder, and the weight of each element and the weight of the intermediate alloy are calculated, as shown in Table 2; the vacuum induction melting furnace is used, the weighed pure Ag, pure Cu and intermediate alloy are put into the alumina crucible, the cover is closed, the vacuum in the furnace is extracted to 10 -2 Pa or less; the heating is started, the heating power is 20 kw, the initial liquid phase is observed from the observation port, high-purity argon is filled to 0.8 MPa vacuum in the furnace, heating is continued until all is in molten state, the power is reduced, the refining temperature is controlled at 650 DEG C for 10 min.

[0078] Step (3) Centrifugal rapid cooling casting

[0079] The molten alloy melt obtained in step (2) is cast by using a centrifugal rapid cooling casting method, the melt is filled into a horizontal graphite casting mold by rotating centrifugal force, the centrifugal casting temperature is 650 DEG C, the centrifugal speed is 1000 n / min, and an alloy slab with a thickness of 15 mm, a width of 250 mm and uniform composition is obtained.

[0080] Step (4) Vacuum heat treatment for controlling crystal orientation

[0081] The alloy slab obtained in step (3) is subjected to crystal orientation organization control in a high vacuum heat treatment furnace, the vacuum degree is <5.0x10-3 Pa, temperature 520℃, holding time 16h, to obtain a grain-oriented alloy ingot.

[0082] Step (5) precision rolling

[0083] The alloy ingot prepared in step (4) is subjected to roughing by using a 250 two-high reversing hot rolling mill, the rolling mill roller temperature is 420℃, the hot rolling pass processing rate is 10%, to obtain a strip with a thickness of 1.0mm and a width of 250mm, which is coiled; the strip is treated by double-side polishing and grinding to a silver bright color; a 50 four-high reversing cold rolling mill is used, the intermediate vacuum annealing temperature is 480℃, the vacuum degree is 10 -2 Pa, the cold rolling pass processing rate is 30% per annealing interval, the tension size is 10kN, multiple pass cold rolling is performed until a foil with a thickness of 0.05mm and a width of 250mm is obtained, which is coiled.

[0084] Example 4:

[0085] Step 1: preparation of raw materials and intermediate alloy

[0086] According to the alloy composition of Example 4 in Table 1, the raw materials are prepared and weighed according to the designed component proportion, the total feeding amount of each furnace is 100kg, and vacuum intermediate frequency induction melting method is respectively selected to prepare Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy and Cu-10Co intermediate alloy;

[0087] Step (2) vacuum intermediate frequency induction melting

[0088] The intermediate alloy prepared in step (1) is calculated according to the weight percentage of each element of the silver-based multi-element near-eutectic medium-temperature vacuum solder, and the weight of each element and the weight of the intermediate alloy are calculated, as shown in Table 2; the vacuum induction melting furnace is used, the weighed pure Ag, pure Cu and intermediate alloy are put into the alumina crucible, covered, the vacuum in the furnace is extracted to 10 -2 Pa; the heating is started, the heating power is 20kw, the initial liquid phase is observed from the observation port, high-purity argon is filled, the vacuum in the furnace is 0.8MPa, the heating is continued until it is all in molten state, the power is reduced, the refining temperature is controlled at 700℃, and the temperature is maintained for 10min.

[0089] Step (3) centrifugal rapid cooling casting

[0090] The molten alloy melt obtained in step (2) is cast by using centrifugal rapid cooling casting method, the melt is filled into a horizontal graphite casting mold by rotating centrifugal force, the centrifugal casting temperature is 700℃, the centrifugal speed is 1000n / min, an alloy slab with a thickness of 10mm and a width of 200mm and uniform composition is obtained.

[0091] Step (4) Vacuum heat treatment to control crystal orientation

[0092] The alloy slab obtained in step (3) is subjected to crystal orientation control in a high-vacuum heat treatment furnace, with a vacuum degree of <5.0x10 -3 Pa, a temperature of 530°C, and a holding time of 12h, to obtain an alloy ingot with consistent grain orientation.

[0093] Step (5) Precision rolling

[0094] The alloy ingot prepared in step (4) is subjected to rough rolling by using a 250 two-high reversing hot rolling mill, with a rolling mill roller temperature of 450°C and a hot rolling pass processing rate of 5%, to obtain a strip with a thickness of 0.8mm and a width of 200mm, which is coiled; the strip is subjected to double-side polishing and grinding treatment to a silver-bright color; a 50 four-high reversing cold rolling mill is used, with an intermediate vacuum annealing temperature of 500°C and a vacuum degree of <10 -2 Pa, a cold rolling pass processing rate of 30% per annealing interval, a tension size of 10kN, and multiple pass cold rolling until a foil with a thickness of 0.08mm and a width of 200mm is obtained, which is coiled.

[0095] Example 5:

[0096] Step 1: Preparation of raw materials and intermediate alloy

[0097] According to the alloy composition of Example 5 in Table 1, raw materials are prepared and weighed according to the designed component proportions, with a total feeding amount of 100kg per furnace, and vacuum intermediate frequency induction melting is used to prepare Ag-20In intermediate alloy, Cu-50Sn intermediate alloy, Cu-40Ge intermediate alloy, Cu-20Ni intermediate alloy, Cu-20Si intermediate alloy, and Cu-10Co intermediate alloy, respectively;

[0098] Step (2) Vacuum intermediate frequency induction melting

[0099] The intermediate alloy prepared in step (1) is weighed according to the weight percentage of each element of the silver-based multi-element near-eutectic medium-temperature vacuum solder, and the weight of each element and the weight of the intermediate alloy are calculated, as shown in Table 2; the vacuum induction melting furnace is used to put the weighed pure Ag, pure Cu and intermediate alloy into the alumina crucible, cover it, and pump the vacuum in the furnace to <10 -2 Pa; the heating power is 30kw, and the initial liquid phase is observed from the observation port; high-purity argon is filled to 0.8MPa vacuum in the furnace, and the temperature is continuously heated to be completely molten; the power is reduced, and the refining temperature is controlled to be 650°C for 8min.

[0100] Step (3) Centrifugal rapid cooling casting

[0101] The melt of the molten alloy obtained in step (2) is filled into a horizontal graphite casting mold by a centrifugal rapid cooling casting method through a rotating centrifugal force, and an alloy slab with a thickness of 12 mm, a width of 100 mm and uniform composition is obtained at a centrifugal casting temperature of 680°C and a centrifugal speed of 750 n / min.

[0102] Step (4) vacuum heat treatment for regulating crystal orientation

[0103] The alloy slab obtained in step (3) is subjected to crystal orientation regulation in a high vacuum heat treatment furnace at a vacuum degree of <5.0 x 10 -3 Pa and a temperature of 520°C for 16 h to obtain an alloy ingot with uniform grain orientation.

[0104] Step (5) precision rolling

[0105] The alloy ingot prepared in step (4) is subjected to rough rolling by using a 250 two-high reversing hot rolling mill at a rolling mill roll temperature of 440°C and a hot rolling pass reduction of 8% to obtain a strip with a thickness of 1.0 mm and a width of 100 mm, which is coiled; the strip is subjected to double-side polishing and grinding treatment to a silver bright color; a 50 four-high reversing cold rolling mill is used, and vacuum annealing is performed at a temperature of 490°C and a vacuum degree of <10 -2 Pa, and the cold rolling pass reduction is 20% and the tension is 5 kN for each pass, and the strip is cold rolled in multiple passes until a foil with a thickness of 0.05 mm and a width of 100 mm is obtained, which is coiled.

[0106] Table 1: Proportions of each element in the alloys in Examples 1-5

[0107]

[0108] Table 2: Weights of each element and intermediate alloy in Examples 1-5

[0109]

[0110]

[0111] The silver-based multi-component near-eutectic medium-temperature vacuum brazing foil strip prepared in Examples 1-5 is respectively subjected to tests of melting point, specification size, wetting performance (316L), joint tensile strength, etc., and the test data are shown in Table 3.

[0112] Table 3: Properties of silver-based multi-component near-eutectic medium-temperature vacuum brazing foil strips in Examples 1-5

[0113]

[0114] For example, Figure 1As shown in the figure, the melting temperature of the AgCuInGeSnNiSiCo alloy obtained by using the alloy proportion and the preparation method designed in the application is 553.35-558.04 DEG C, the melting range is only 6 DEG C, and the endothermic peak and the exothermic peak curve are obvious, without low-melting-point phase precipitation and phase change.

[0115] As shown in the figure, the melting temperature of the AgCuInGeSnNiSiCo alloy obtained by using the alloy proportion and the preparation method designed in the application is 553.35-558.04 DEG C, the melting range is only 6 DEG C, and the endothermic peak and the exothermic peak curve are obvious, without low-melting-point phase precipitation and phase change. Figure 2 As shown in the figure, the melting temperature of the AgCuInGeSnNiSiCo alloy obtained by using the alloy proportion and the preparation method designed in the application is 553.35-558.04 DEG C, the melting range is only 6 DEG C, and the endothermic peak and the exothermic peak curve are obvious, without low-melting-point phase precipitation and phase change.

[0116] The eutectic medium-temperature solder has moderate melting temperature, has excellent wettability for Cu, Ni, Kovar alloy and stainless steel base materials, and meets the packaging requirements of 316L stainless steel materials in the vacuum electronic device.

[0117] The silver-based multi-component near-eutectic medium-temperature vacuum solder and the preparation method mainly solve the problems of no reliable solder for vacuum brazing of 316L stainless steel medium-temperature base materials in the vacuum electronic device and the difficulty of vacuum brazing of 316L stainless steel. The multi-component alloy solder has a melting point of 552-562 DEG C and a melting range of less than 10 DEG C, and the recommended brazing temperature is 630 DEG C. The preparation method comprises intermediate alloy preparation, vacuum medium-frequency induction melting, centrifugal rapid cooling casting, vacuum heat treatment regulation and control, hot rolling, surface treatment and precision cold rolling. The alloy has low melting point, low required vacuum brazing temperature, excellent wettability for stainless steel, high joint strength after brazing, and meets the packaging, gradient brazing and repair welding requirements of 316L stainless steel base materials in the vacuum electronic device.

[0118] The above examples only show part of the embodiments of the silver-based multi-component near-eutectic medium-temperature vacuum solder, and in the technical solutions of the application: the content of the metal elements in the solder alloy can be freely selected within the specified range, which is not listed one by one here, so the technical solutions contained in the above description should be regarded as exemplary, rather than limiting the protection scope of the application.

Claims

1. A silver-based multi-element near-eutectic mid-temperature vacuum solder, characterized in that, By weight percentage, it contains: Cu 19.5–21.0 wt%, In 9.0–10.0 wt%, Ge 4.5–5.5 wt%, Sn 4.2–4.8 wt%, Ni 1.8–2.2 wt%, Si 1.7–2.0 wt%, Co 0.05–0.2 wt%, with Ag as the balance.

2. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 1, characterized in that, Includes the following steps: (1) Raw material selection and preparation of master alloy According to the composition of the silver-based multi-element near-eutectic medium-temperature vacuum solder, Ag, Cu, In, Ge, Sn, Ni, Si and Co are used as raw materials; Ag-In master alloy, Cu-Sn master alloy, Cu-Ge master alloy, Cu-Ni master alloy, Cu-Si master alloy and Cu-Co master alloy were prepared by vacuum medium frequency induction melting. (2) Vacuum medium-frequency induction melting The intermediate alloy obtained in step (1) is used to calculate the weight of each element and the weight of the intermediate alloy according to the weight percentage of each element in the silver-based multi-element near-eutectic medium-temperature vacuum brazing filler metal. Using a vacuum induction melting furnace, the weighed pure Ag, pure Cu and intermediate alloy are all placed into an alumina crucible, the lid is closed and the furnace is evacuated. Heating is turned on, and when the initial liquid phase is seen from the observation port, high-purity argon is introduced and heating is continued until all are in a molten liquid state. The power is then reduced and refining is carried out. (3) Centrifugal rapid cooling casting The molten alloy melt obtained in step (2) is centrifugally cooled and cast. By rotating the centrifugal force, the melt is filled into a horizontal graphite casting mold to obtain an alloy slab with uniform composition. (4) Vacuum heat treatment to control crystal orientation The alloy slab obtained in step (3) is subjected to crystal orientation control in a high vacuum heat treatment furnace to obtain an alloy ingot with consistent grain orientation. (5) Precision rolling The alloy ingot obtained in step (4) is rough rolled by a hot rolling mill to obtain strip and coil; the strip is polished on both sides until it is silvery; and then cold rolled in multiple passes by a cold rolling mill until foil is obtained and coil.

3. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The purity of the raw materials Ag, Cu, In, Ge, Sn, Ni, Si, and Co is all 99.999 wt.%.

4. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, Ag-20In master alloy, Cu-50Sn master alloy, Cu-40Ge master alloy, Cu-20Ni master alloy, Cu-20Si master alloy and Cu-10Co master alloy were prepared by vacuum medium frequency induction melting.

5. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The melting method is vacuum medium-frequency induction melting, with a refining temperature of 650–700℃ and a refining time of 5–10 minutes; during vacuum melting, the furnace is evacuated to a vacuum level of 10℃. -2 The pressure is below Pa; the heating power is 20-30 kW; after filling with high-purity argon, the vacuum inside the furnace is 0.8 MPa.

6. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 5, characterized in that, The casting method is centrifugal pressure rapid cooling casting, with a centrifugal casting temperature of 650-700℃ and a centrifugal speed of 500-1000n / min.

7. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The alloy slab has a thickness of 10-15 mm and a width of 80-250 mm.

8. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The microstructure and crystal orientation were controlled by vacuum heat treatment with a vacuum level of <5.0×10⁻⁶. -3 Pa, temperature 520-530℃, holding time 12-16h.

9. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The hot rolling mill is a 250-roll two-high reversible hot rolling mill, with a roll temperature of 420–450°C and a hot rolling pass rate of 5%–10%. The cold rolling mill is a 50-type four-high reversible cold rolling mill, with an intermediate vacuum annealing temperature of 480–500°C and a vacuum degree of 10. -2 For Pa below 1, the cold rolling pass rate per annealing interval is 15% to 30%, and the tension is 0 to 10 kN.

10. The method for preparing silver-based multi-element near-eutectic intermediate-temperature vacuum solder according to claim 2, characterized in that, The strip has a thickness of 0.8–1.0 mm and a width of 80–250 mm; the foil has a thickness of 0.05–0.1 mm and a width of 80–250 mm.

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