A method for preparing vacuum brazing activation material based on fluorinated alkanes

Abstract

This invention discloses a method for preparing a vacuum brazing activation material based on fluorinated alkanes, relating to the field of semiconductor vacuum brazing materials technology. The method involves loading fluorinated alkanes onto a porous inorganic carrier to form a fluorine-containing core, and then forming a continuous synergistic release layer on the outer surface of the core. The material is then dried, shaped, and encapsulated with inorganic fibers for breathability to obtain the vacuum brazing activation material. The activation material achieves gas-phase activation of the alumina film, nickel oxide, and copper oxide composite film before the aluminum-silicon brazing filler metal melts, by first preventing carbon black release through a first release peak and then releasing fluorine-containing small molecule gases through a second release peak. This reduces the contact angle of the brazing filler metal, increases the brazing filler metal spreading area, reduces weld porosity, improves joint shear strength and weld interface continuity, reduces post-weld carbon and fluoride ion residues, and achieves low-pollution vacuum brazing connections that do not rely on magnesium vapor-sealed cavities and do not introduce ordinary organic flux.

Description

Technical Field

[0001] This invention relates to the field of semiconductor brazing technology, specifically to a method for preparing a vacuum brazing activation material based on fluorinated alkanes. Background Technology

[0002] Vacuum brazing is commonly used in semiconductor packaging, power device heat dissipation structures, metallized substrate connections, and vacuum-sealed housing manufacturing processes to achieve highly reliable connections between chip carriers, heat dissipation base plates, cooling plates, stainless steel frames, and metallized connection layers. The quality of brazing depends not only on the melting and spreading state of the brazing filler metal itself, but also on the oxide film on the surface of the metal to be soldered, the cleanliness of the brazing atmosphere, the volatilization residue of activating materials, and the control of contamination in the weld area.

[0003] In traditional semiconductor vacuum brazing scenarios, aluminum alloy cold plates, stainless steel packaging frames, nickel-plated copper heat sinks, and metallized ceramic substrates are prone to forming aluminum oxide, chromium oxide, or composite metal oxide films. These oxide films are difficult to remove completely under normal vacuum and low brazing temperatures, making it difficult for the solder to continuously wet the surface to be soldered. Existing processes typically rely on increasing the brazing temperature, increasing the vacuum level, using magnesium vapor to break the film, setting an active metal layer, or using flux-containing solder paste to improve the connection effect. However, increasing the temperature can easily cause solder to spread and increase the heat-affected zone. The magnesium vapor route has high requirements for cavity sealing and solder morphology. The active metal layer can easily change the interface reaction structure, and ordinary flux is difficult to meet the common requirements of high-temperature vacuum brazing and clean semiconductor connection. Summary of the Invention

[0004] This invention provides a method for preparing vacuum brazing activation materials based on fluorinated alkanes, which solves the problems mentioned in the background art.

[0005] A method for preparing a vacuum brazing activation material based on fluoroalkane includes the following steps: S1. A porous inorganic support with a pore size of 1μm-100μm is desorbed at 120℃-300℃ for 1h-4h. After cooling to 30℃-60℃, it is added to a sealed impregnation container with fluoroalkanes with a boiling point of 40℃-220℃ and a fluorine mass fraction of 30%-80% at a mass ratio of 40-80:10-40. The container is then impregnated at a temperature 10℃-40℃ lower than the boiling point of the fluoroalkanes for 30min-180min, so that the fluoroalkanes enter the pores of the porous inorganic support to obtain a fluorine-loaded core. S2. Nitrocellulose, aluminum hydroxide, silica sol-coated ammonium bicarbonate and silica sol are mixed in a mass ratio of 1-10:1-15:1-15:5-25 and stirred at 20℃-50℃ for 20min-90min to obtain a carbon black synergistic slurry. The carbon black synergistic slurry is coated on the outer surface of the fluorine-containing loaded core to form a continuous synergistic release layer on the outer surface of the fluorine-containing loaded core, thus obtaining a core-outer layer composite. S3. The core-outer layer composite is dried at 20℃-80℃, the drying temperature is 20℃-60℃ lower than the boiling point of the fluoroalkane, and the drying endpoint is when the mass change rate of two consecutive weighings is less than 0.5%. Then, it is pressed into tablets to obtain the dried composite molded body. S4. The dried composite molded body is placed into an inorganic fiber breathable constraint packaging material and sealed to obtain a vacuum brazing activated material. The vacuum brazing activated material is subjected to a vacuum degree of 10. -4 Under the detection conditions of thermogravimetric-mass spectrometry (TGS-MS) at Pa-10 Pa and heating rates of 5℃ / min-20℃ / min, the system exhibits a first release peak formed by the continuous synergistic release layer and a second release peak formed by the fluorine-containing loaded core. The temperature range of the first release peak is 180℃-350℃, the starting temperature range of the second release peak is 350℃-450℃, the termination temperature of the second release peak is 20℃-80℃ lower than the solidus temperature of the solder to be used, the starting temperature of the second release peak is lower than the termination temperature of the second release peak, and the first release peak is formed before the second release peak.

[0006] Preferably, the porous inorganic carrier is one of calcium fluoride porous particles, alumina porous particles, boron nitride porous particles, and magnesium fluoride porous particles. The porous inorganic carrier has a specific surface area of ​​20 m² / g-200 m² / g, and the moisture content of the porous inorganic carrier after the desorption treatment is less than 0.5%.

[0007] Preferably, the fluoroalkane is one of perfluorohexane, perfluoroheptane, perfluorooctane, and 1H,1H,2H,2H-perfluorooctane; The fluoroalkane has an acid value of less than 0.05 mg KOH / g and a moisture content of less than 500 ppm.

[0008] Preferably, the loading amount of the fluorinated alkane in the fluorinated loaded core is 12%-35% of the mass of the fluorinated loaded core; The mass loss rate of the fluorine-containing loaded core after being sealed at 25°C for 24 hours, based on its initial mass, is less than 2%.

[0009] Preferably, the thickness of the continuous synergistic release layer is 50μm-500μm; The mass of the continuous synergistic release layer is 5%-30% of the mass of the fluorine-containing loaded core; The continuous synergistic release layer covers 90%-100% of the outer surface of the fluorine-containing loaded core.

[0010] Preferably, the nitrogen content of the nitrocellulose is 10%-13.5%; The particle size D50 of the aluminum hydroxide is 0.5μm-20μm; The silica sol-coated ammonium bicarbonate comprises an ammonium bicarbonate core material and a silica sol-cured layer coated on the outer surface of the ammonium bicarbonate core material, wherein the mass of the silica sol-cured layer is 5%-25% of the mass of the ammonium bicarbonate core material.

[0011] Preferably, the pressure for tablet compression is 5MPa-30MPa; The thickness of the dried composite molded body is 0.5mm-5mm; The porosity of the dried composite molded body is 10%-45%.

[0012] Preferably, the inorganic fiber breathable restraint packaging material is one of quartz fiber cloth, alumina fiber paper, and boron nitride fiber felt; The average pore size of the inorganic fiber breathable restraint packaging material is 5μm-100μm; The inorganic fiber breathable restraint packaging material has a mass loss rate of less than 1% after being kept in a vacuum environment at 900℃ for 30 minutes.

[0013] Preferably, under the thermogravimetric-mass spectrometry detection conditions; The first release peak includes a channel peak at m / z=18 and a channel peak at m / z=44; The second release peak includes a channel peak at m / z=19 and a channel peak at m / z=69.

[0014] Preferably, the semiconductor workpiece to be soldered that is compatible with the vacuum brazing activation material is one of the following: aluminum alloy cold plate, stainless steel packaging frame, nickel-plated copper heat sink, and metallized ceramic substrate. The solder to be used is one of aluminum-silicon solder, silver-copper solder, and copper-based solder, and the solidus temperature of the solder to be used is 550℃-900℃.

[0015] This invention provides a method for preparing a vacuum brazing activation material based on fluoroalkane, which has the following beneficial effects: 1. The vacuum brazing activation material prevents the release of carbon black through the first release peak and the release of fluorine-containing small molecule gases through the second release peak, so that the alumina film, nickel oxide and copper oxide composite film are activated in the gas phase before the aluminum-silicon brazing filler metal melts; it reduces the contact angle of the brazing filler metal, expands the brazing filler metal spreading area, reduces the weld porosity, improves the joint shear strength and weld interface continuity; reduces post-weld carbon residue and post-weld fluoride ion residue; and achieves low-pollution vacuum brazing connection without relying on magnesium vapor closed cavity and without introducing ordinary organic flux.

[0016] 2. Vacuum brazing activation material loads low-boiling-point fluoroalkanes through a porous inorganic carrier and stabilizes the release sequence through a continuous synergistic release layer; it reduces the risk of premature volatilization loss, release peak drift, and insufficient activation concentration of low-boiling-point fluoroalkanes; and, in conjunction with the porous structure of the dried composite molded body and the inorganic fiber breathable constraint packaging material, it improves storage stability, batch preparation consistency, and activity retention before furnace loading.

[0017] 3. Vacuum brazing activation materials, through drying endpoint control, sheet forming, and inorganic fiber permeable constraint packaging, ensure structural integrity and maintain gas escape channels during high-temperature vacuum brazing; reduce powder shedding, cracking, release lag, and solid residue migration; and improve the anti-powdering ability, high-temperature constraint ability, and large-area interface gas phase activation ability in high-temperature semiconductor heat dissipation connections. Attached Figure Description

[0018] Figure 1 A schematic diagram of the preparation process for vacuum brazing activation materials; Figure 2 This is a schematic diagram of non-contact activation application and release timing. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1 In this embodiment, the vacuum brazing activation material is applied to the vacuum brazing scenario of the heat dissipation structure of a semiconductor power module, specifically for surface activation before brazing between an aluminum alloy cold plate and a nickel-plated copper heat sink. The surface of the aluminum alloy cold plate has a dense aluminum oxide film, and the surface of the nickel-plated copper heat sink has a composite film of nickel oxide and copper oxide. Under conventional vacuum brazing conditions, the above oxide film is difficult to remove sufficiently before the solder melts, which easily leads to insufficient aluminum-silicon brazing filler metal spreading, increased weld porosity, and decreased interface bonding strength. In this embodiment, by preparing an activation material that can be placed non-contactly in the semiconductor vacuum brazing area, it first releases anti-carbon black gas before the solder melts and then releases fluorine-containing small molecule gas to achieve gas-phase activation of the oxide film and suppression of carbon residue.

[0021] This invention provides a method for preparing a vacuum brazing activation material based on fluorinated alkanes. Please refer to [link to relevant documentation]. Figure 1 and Figure 2 This includes the following steps: S1. Select calcium fluoride porous particles with a pore size of 30 μm as a porous inorganic support. Place 60 g of the calcium fluoride porous particles in a vacuum drying oven and desorb them at 200 °C for 2 h. After desorption, cool to 45 °C to obtain the desorbed porous inorganic support. Select 1H,1H,2H,2H-perfluorooctane with a boiling point of 142 °C and a fluorine mass fraction of 68% as a fluoroalkane. Add 25 g of the 1H,1H,2H,2H-perfluorooctane and 60 g of the desorbed porous inorganic support into a sealed impregnation container and impregnate at 110 °C for 90 min to allow the 1H,1H,2H,2H-perfluorooctane to enter the pores of the calcium fluoride porous particles, thus obtaining a fluorine-loaded core. S2. Take 5g of nitrocellulose, 8g of aluminum hydroxide, 8g of silica sol-coated ammonium bicarbonate, and 14g of silica sol and mix them. Stir at 35℃ for 60min to obtain a carbon black synergistic slurry. The silica sol-coated ammonium bicarbonate consists of an ammonium bicarbonate core material and a silica sol curing layer coated on the outer surface of the ammonium bicarbonate core material. The mass of the silica sol curing layer is 15% of the mass of the ammonium bicarbonate core material. The carbon black synergistic slurry is uniformly coated on the outer surface of the fluorine-containing loaded core material to form a continuous synergistic release layer on the outer surface of the fluorine-containing loaded core material, thus obtaining a core-outer layer composite. S3. Place the core-outer layer composite in a vacuum drying oven and dry it at 60°C, where the 60°C is lower than the boiling point of 1H,1H,2H,2H-perfluorooctane (82°C). Weigh the composite every 30 minutes. When the mass change rate of two consecutive weighings is 0.3%, the drying process is stopped. Then, the composite is pressed into a sheet under a pressure of 15 MPa to obtain a dried composite with a thickness of 2 mm. S4. The dried composite molded body is packed into a quartz fiber cloth packaging material with an average air permeability of 30 μm and sealed to obtain a vacuum brazing activated material; the vacuum brazing activated material is subjected to thermogravimetric-mass spectrometry (TGA) for detection, and the vacuum degree is 10. -2 Pa, heating rate of 10℃ / min, the test results show that the vacuum brazing activation material has a first release peak formed by the continuous synergistic release layer and a second release peak formed by the fluorine-containing loaded core. The temperature range of the first release peak is 220℃-310℃, the starting temperature of the second release peak is 380℃, the ending temperature of the second release peak is 520℃, and the first release peak is formed before the second release peak. In brazing applications, the vacuum brazing activation material is placed 30mm outside the area to be brazed between the aluminum alloy cold plate and the nickel-plated copper heat sink. The vacuum brazing activation material does not directly contact the aluminum-silicon brazing filler metal, the aluminum alloy cold plate, and the nickel-plated copper heat sink. The solidus temperature of the aluminum-silicon brazing filler metal is 577°C, and the termination temperature of the second release peak of 520°C is lower than the solidus temperature of the aluminum-silicon brazing filler metal of 57°C. Therefore, the vacuum brazing activation material can complete the anti-carbon black synergistic release and the release of fluorine-containing small molecule gases before the aluminum-silicon brazing filler metal melts.

[0022] This embodiment takes the vacuum brazing of aluminum alloy cold plate and nickel-plated copper heat sink in the heat dissipation structure of semiconductor power module as the verification object, and uses aluminum-silicon brazing filler metal as the solder to be used. The solidus temperature of the aluminum-silicon brazing filler metal is 577°C. The surface of the aluminum alloy cold plate has a dense oxide film mainly composed of aluminum oxide, and the surface of the nickel-plated copper heat sink has a composite film of nickel oxide and copper oxide. The vacuum brazing activation material is used to perform vapor-phase activation on the alumina film, the nickel oxide and the copper oxide composite film before the aluminum-silicon brazing filler metal melts, and to prevent solid residues of the activation material from entering the weld area in a non-contact manner. The aluminum alloy cold plate is ultrasonically cleaned with acetone for 10 minutes, rinsed with anhydrous ethanol for 5 minutes, and dried at 60°C for 30 minutes before being put into use. The nickel-copper heat sink is ultrasonically cleaned with acetone for 10 minutes, rinsed with anhydrous ethanol for 5 minutes, and dried at 60°C for 30 minutes before use. The above cleaning steps are used to remove oil and loose contaminants from the surface to be welded, but not to remove the dense oxide film on the surface to be welded, so as to ensure that subsequent comparative tests can reflect the gas-phase activation effect of the vacuum brazing activation material on the metal oxide film.

[0023] In the specific preparation, calcium fluoride porous particles with a pore size of 30 μm were selected as porous inorganic carriers. 60 g of the calcium fluoride porous particles were placed in a vacuum drying oven and desorbed at 200 °C for 2 h. Then, the temperature was cooled to 45 °C to obtain the desorbed porous inorganic carrier. The porous calcium fluoride particles are characterized by vacuum and high temperature resistance, low moisture absorption and low reactivity. The pore size of 30 μm can balance the wetting efficiency of fluoroalkanes entering the pores and the delayed release effect during the subsequent heating process. If the pore size is too small, fluorinated alkanes will have difficulty entering the pores, reducing the loading of the fluorine-loaded core and easily leading to excessive lag of the second release peak. If the pore size is too large, the porous inorganic carrier will have a reduced ability to retain fluorinated alkanes, and the fluorinated alkanes will be easily lost in the early stage of vacuuming, resulting in insufficient release of fluorine-containing small molecule gases before the solder melts. The 200℃ desorption treatment is used to remove adsorbed water and low-boiling impurities from the pores. If the desorption temperature is too low, there will be a lot of residual water in the pores, which can easily interfere with the stability of the subsequent fluorine-containing load. If the desorption temperature is too high, it will increase energy consumption and may affect the pore structure stability of the porous inorganic carrier.

[0024] In this embodiment, 1H,1H,2H,2H-perfluorooctane with a boiling point of 142°C and a fluorine mass fraction of 68% was selected as a fluoroalkane. 25g of the 1H,1H,2H,2H-perfluorooctane and 60g of the desorbed calcium fluoride porous particles were added to a sealed impregnation container and impregnated at 110°C for 90 minutes to allow the 1H,1H,2H,2H-perfluorooctane to enter the pores of the calcium fluoride porous particles, thus obtaining a fluorine-loaded core. The 110°C is lower than the boiling point of 1H,1H,2H,2H-perfluorooctane, which is 32°C. This temperature can improve the wetting ability of fluoroalkanes on the pores of porous inorganic carriers, and can also prevent the fluoroalkanes from volatilizing in large quantities during the impregnation stage. The impregnation time of 90 minutes is selected to stabilize the pore adsorption. Too short a time will result in insufficient load, while too long a time will have limited effect on increasing the load and increase the risk of volatilization loss. The fluorine-containing loaded core is the structural basis for the formation of the second release peak. It is not used as a weld filler, but as an activation source for the release of fluorine-containing small molecule gases with the furnace.

[0025] Subsequently, 5g of nitrocellulose, 8g of aluminum hydroxide, 8g of silica sol-coated ammonium bicarbonate and 14g of silica sol were taken and stirred at 35℃ for 60min to obtain a carbon black synergistic slurry. The nitrocellulose is used to decompose and release oxygen source gas at lower temperatures to suppress carbon deposition generated during the cracking of fluorine-containing organic components. The aluminum hydroxide is used to release water vapor during heating to promote the conversion of carbonaceous deposits into gaseous products; The silica sol coating of ammonium bicarbonate is used to delay the release of bulky gas and form a gas escape channel; The silica sol is used to form an inorganic bonding skeleton after drying to ensure that the outer layer maintains continuity during handling, pressing and encapsulation. The silica sol-coated ammonium bicarbonate consists of an ammonium bicarbonate core material and a silica sol-cured layer covering the outer surface of the ammonium bicarbonate core material, wherein the mass of the silica sol-cured layer is 15% of the mass of the ammonium bicarbonate core material. The purpose of using a silica sol curing layer to coat ammonium bicarbonate is to prevent the ammonium bicarbonate from decomposing prematurely during the low-temperature stirring and drying stages, and at the same time to enable it to form loose channels in the continuous synergistic release layer when releasing gas during the subsequent heating stage.

[0026] The carbon black synergistic slurry is uniformly coated on the outer surface of the fluorine-containing loaded core, so that a continuous synergistic release layer is formed on the outer surface of the fluorine-containing loaded core, resulting in a core-outer layer composite. The continuous synergistic release layer is disposed on the outside of the fluorine-containing load core, so that it first comes into contact with the external vacuum environment and releases when heated, thereby first forming an oxygen release, water release and gas release environment, and then the fluorine-containing load core releases fluorine-containing small molecule gas. This spatial order can prevent the direct cracking of fluorine-containing components to form a dense carbon black layer, and can also pre-establish gas escape channels before the formation of the second release peak; If the continuous synergistic release layer is not provided, carbonaceous residue is easily formed in the fluorine-containing load core during the high-temperature release process. After the carbonaceous residue covers the area around the weld, it will weaken the wetting effect of the brazing filler metal and increase the risk of weld porosity and inclusions.

[0027] The core-outer layer composite was placed in a vacuum drying oven and dried at 60°C. It was weighed every 30 minutes. The drying was stopped when the mass change rate of two consecutive weighings was 0.3%. Then it was pressed into a sheet under a pressure of 15 MPa to obtain a dried composite molded body with a thickness of 2 mm. The 60°C is lower than the boiling point of 1H,1H,2H,2H-perfluorooctane (82°C), which can reduce the loss of fluoroalkanes while removing free solvents from the slurry and improving the stability of the outer layer structure. Using the mass change rate of two consecutive weighings as the drying endpoint can avoid insufficient drying leading to excessive water content in the coating layer and abnormal gas release during welding, and can also avoid excessive drying leading to cracking of the coating layer and loss of fluorine-loaded core active components. A tableting pressure of 15 MPa is selected to ensure that the dried composite molded body has sufficient mechanical integrity and pore connectivity. Too low a pressure will cause the molded body to shed powder, while too high a pressure will reduce the porosity and hinder the release of gas.

[0028] The dried composite molded body is packed into a quartz fiber cloth packaging material with an average air permeability of 30 μm and sealed to obtain a vacuum brazing activated material. The quartz fiber cloth covering is used to form an inorganic fiber breathable constraint structure. Its average breathable pore size allows the released gas to pass through while restricting solid powder, debris and inorganic residues from entering the semiconductor vacuum brazing area. The vacuum brazing activation material can act on the surface to be brazed in a non-contact manner and reduce the impact of particulate contamination, solid inclusions and localized corrosion residues on the reliability of semiconductor packaging. In brazing applications, the vacuum brazing activation material is placed 30mm outside the area to be brazed between the aluminum alloy cold plate and the nickel-plated copper heat sink. The vacuum brazing activation material does not come into direct contact with the aluminum-silicon brazing filler metal, the aluminum alloy cold plate and the nickel-plated copper heat sink. This 30mm distance allows fluorine-containing small molecule gases to diffuse to the surface to be welded and participate in the gas phase activation of the oxide film, while also preventing the thermal decomposition residues of the activated material from falling directly into the weld.

[0029] To verify the technical effect of this embodiment, the following were compared: Example 1 fluorinated alkane activated material, Comparative Example 1 vacuum brazing without activated material, Comparative Example 2 ordinary rosin flux, Comparative Example 3 fluorine-loaded particles without carbon black outer layer, and Comparative Example 4 magnesium vapor-assisted aluminum-silicon brazing. All test objects used the same specifications of aluminum alloy cold plate, nickel-plated copper heat sink and aluminum-silicon brazing filler metal, and the solidus temperature of the aluminum-silicon brazing filler metal was 577℃. All test objects were brazed under the same vacuum furnace, the same fixture, the same heating rate and the same heat preservation regime to eliminate the influence of differences in substrate size, solder amount, clamping pressure and thermal cycle on the test results; Comparative Example 1, without the addition of any activating material, was used to characterize the welding state when the oxide film was difficult to remove under conventional vacuum brazing conditions. Comparative Example 2: Common rosin-based flux was added to the weld area to characterize the residue and wetting improvement effect of traditional organic flux system in semiconductor vacuum brazing scenario. Comparative Example 3 uses the same fluorine-containing loaded core, the same tableting conditions and the same quartz fiber cloth packaging as Example 1, but without the continuous synergistic release layer, to verify the effect of the anti-carbon black synergistic structure on reducing carbon residue and improving weld quality. Comparative Example 4 uses magnesium vapor-assisted aluminum-silicon brazing to characterize the effect of conventional aluminum vacuum brazing film-breaking pathways.

[0030] The release behavior of each test subject was detected using thermogravimetric-mass spectrometry (TGA) at a detection vacuum of 10. -2 Pa, with a heating rate of 10℃ / min, and the temperature range of the first release peak and the termination temperature of the second release peak are recorded accordingly; The activation margin before the solidus line of the solder is calculated based on the difference between the solidus line temperature of the aluminum-silicon solder and the termination temperature of the main activation action. The main activation termination temperature in Examples 1 and 3 was the second release peak termination temperature, while the main activation termination temperature in Comparative Example 4 was the effective film-breaking temperature of magnesium vapor. Comparative Example 1 did not produce a detectable activation release peak, and Comparative Example 2 did not produce a fluorine-containing gas phase film rupture release peak. Therefore, the activation margin before the solder solidus line for both examples was recorded as 0. After brazing, the contact angle of the brazing filler metal on the aluminum alloy surface is measured using a wetting angle measuring instrument; The brazing filler metal spreading area was measured using image area analysis. X-ray non-destructive testing was used to statistically analyze the weld porosity. The shear strength of the joint was tested using a shear testing machine; The percentage of carbon residue area after welding was statistically analyzed using the microscopic image thresholding method. The residual fluoride ions after welding were detected by ion chromatography. Metallographic cross-sectional images were used to analyze the continuity of the weld interface. The specific experimental results are summarized in Table 1; Table 1: Comparison of the effects of Example 1 and Comparative Examples 1-4; First release peak temperature range / ℃ 220-310 none 180-260 none none Termination temperature of the second release peak / °C 520 none none 535 none Solder activation margin before solidus line / °C 57 0 0 42 35 Aluminum alloy surface solder contact angle / ° 23 86 62 48 31 Brazing filler metal spread area / mm² 184 72 96 121 158 Weld porosity / % 1.8 12.6 9.4 7.8 4.6 Joint shear strength / MPa 68.5 31.2 39.6 46.8 59.4 Percentage of carbon residue area after welding / % 0.7 0.4 6.8 9.5 0.9 Residual fluoride ions after welding / μg / cm² 0.18 0 0 0.52 0 Weld interface continuity rate / % 96.4 68.5 74.2 82.1 91.3 As can be seen from Table 1, the first release peak temperature range is used to characterize the early release behavior of the anti-carbon black synergistic release layer. It is obtained by thermogravimetric-mass spectrometry and the main release temperature ranges corresponding to the m / z=18 channel peak and the m / z=44 channel peak are used as the judgment criteria. The first release peak temperature range of Example 1 is 220℃-310℃, indicating that the continuous synergistic release layer can generate water release, gas release and gas phase environment related to carbonaceous deposition inhibition before the large-scale release of the fluorine-containing load core. Comparative Examples 1 and 4 did not have a continuous coordinated release layer, therefore the first release peak was not detected; Although ordinary rosin-based flux in Comparative Example 2 has an organic volatile release range of 180℃-260℃, this release range mainly corresponds to the volatilization and thermal decomposition of organic flux components, and cannot form a preliminary carbon black release prevention system that works in conjunction with the fluorine-loaded core. Comparative Example 3 only has a fluorine-containing loaded core and does not have a continuous co-release layer, so there is no first release peak. This shows that the first release peak of Example 1 comes from the continuous co-release layer, rather than from the volatilization of ordinary organic matter or the release of the fluorine-containing loaded core itself.

[0031] The second release peak termination temperature is used to characterize the termination point of the release of fluorine-containing small molecule gas from the fluorine-containing load core. It is obtained by thermogravimetric-mass spectrometry and the main release termination temperatures corresponding to the m / z=19 channel peak and the m / z=69 channel peak are used as the basis for judgment. The second release peak termination temperature in Example 1 was 520°C, and the second release peak termination temperature in Comparative Example 3 was 535°C, indicating that both could release fluorine-containing small molecule gas before the aluminum-silicon brazing filler metal melted. However, in Example 1, due to the setting of a continuous synergistic release layer, the termination temperature of the second release peak was 15°C earlier than that of Comparative Example 3, indicating that the loose channels formed by the continuous synergistic release layer are conducive to the orderly dispersion of fluorine-containing small molecule gases. Comparative Examples 1 and 2 do not contain fluorine-loaded cores, therefore no second release peak is observed; Comparative Example 4 relied on magnesium vapor for membrane rupture and was not activated by fluorine-containing small molecule gases, therefore it also had no second release peak.

[0032] The activation margin before the solder solidus line is used to characterize the degree to which the activation process precedes the solder melting process. It is defined as the difference between the solidus temperature of the aluminum-silicon solder and the termination temperature of the main activation action. In Example 1, the solidus temperature of the aluminum-silicon solder is 577°C, and the termination temperature of the second release peak is 520°C. Therefore, the activation margin before the solidus of the solder is 57°C. The activation margin before the solidus line of the solder in Comparative Example 3 is 42°C, which is lower than that in Example 1. This indicates that its fluorine gas release is closer to the solder melting point, which can easily lead to insufficient gas phase activation or overlap with the solder melting process. The activation margin before the solidus line of the solder in Comparative Example 4 was 35°C, indicating that although magnesium vapor-assisted film breaking can occur earlier, the advance amount is less than that in Example 1. Comparative Examples 1 and 2 did not have any identifiable termination points for fluorine-containing gas phase film rupture, so they were recorded as 0. This parameter indicates that Example 1 can complete the vapor phase film breaking before the solder melts, avoiding the molten solder facing the oxide film that has not yet loosened.

[0033] The contact angle of the brazing filler metal on the surface of aluminum alloy is used to characterize the wetting ability of the brazing filler metal on the surface of the aluminum alloy cold plate. It is measured by a wetting angle measuring instrument at the spreading edge of the cooled sample after brazing. The smaller the value, the better the wettability. The contact angle of Example 1 was 23°, which was significantly lower than that of Comparative Example 1 (86°), Comparative Example 2 (62°), Comparative Example 3 (48°), and Comparative Example 4 (31°). The results show that without the addition of activating materials, the alumina film severely hinders the spread of the solder. Ordinary rosin-based fluxes are difficult to effectively break the dense oxide film in high-temperature vacuum brazing. Although the fluorine-containing loaded particles without the anti-carbon black outer layer have a certain film-breaking ability, the carbon residue weakens the wetting effect. Example 1 achieves the highest degree of surface activation in aluminum alloys by combining the initial prevention of carbon black release with subsequent fluorine-containing vapor phase film rupture, resulting in the lowest contact angle.

[0034] The brazing filler metal spreading area is used to characterize the ability of molten aluminum-silicon brazing filler metal to spread on the surface to be soldered. It is obtained by acquiring a top view image after soldering and using image area analysis. The larger the value, the more fully the brazing filler metal spreads. The spreading area of ​​Example 1 is 184 mm², which is higher than that of Comparative Example 1 (72 mm²), Comparative Example 2 (96 mm²), Comparative Example 3 (121 mm²), and Comparative Example 4 (158 mm²). The results are consistent with the trend of contact angle change, indicating that Example 1 not only improved the local wetting angle, but also improved the continuous spreading ability of the brazing filler metal in the actual welding area; The spreading area of ​​Comparative Example 3 was lower than that of Example 1, further illustrating that fluorine release alone is insufficient to obtain the best spreading effect, and the anti-carbon black synergistic release layer plays a key role in maintaining the wettability of the activated surface.

[0035] Weld porosity is used to characterize the degree of internal defects in welds. It is obtained by X-ray non-destructive testing and is expressed as the percentage of the projected area of ​​the porosity to the total projected area of ​​the weld. The lower the value, the better the weld compactness. The weld porosity of Example 1 was 1.8%, which was significantly lower than that of Comparative Example 1 (12.6%), Comparative Example 2 (9.4%), Comparative Example 3 (7.8%), and Comparative Example 4 (4.6%). Comparative Example 1 showed the highest porosity, indicating that when the oxide film was not effectively removed, the solder could not fill the interfacial micro-regions and was prone to forming unbonded voids. The higher porosity of Comparative Example 2 indicates that the volatile and carbon residues in ordinary organic flux systems will increase weld defects. The porosity of Comparative Example 3 was still higher than that of Example 1, indicating that the carbonaceous deposition generated during the release of fluorine-containing components would offset part of the gas-phase activation effect. Example 1 reduces the risk of carbon residue by first releasing the first release peak, and then completes the vapor phase film breaking by the second release peak, thus achieving the lowest weld porosity.

[0036] Joint shear strength is used to characterize the reliability of the interfacial bond between aluminum alloy cold plate and nickel-plated copper heat sink. It is obtained by testing with a shear testing machine under the same loading rate. The higher the value, the better the load-bearing capacity of the welded joint. The shear strength of the joint in Example 1 was 68.5 MPa, which was higher than that of Comparative Example 1 (31.2 MPa), Comparative Example 2 (39.6 MPa), Comparative Example 3 (46.8 MPa), and Comparative Example 4 (59.4 MPa). The results show that the low contact angle, high spread area and low porosity obtained in Example 1 can be translated into higher actual joint strength. Although Comparative Example 4 used magnesium vapor to assist in membrane rupture and obtained better strength, it was still lower than that of Example 1, indicating that the non-contact fluorine-containing gas-phase activation system of Example 1 can obtain better interfacial bonding effect without relying on magnesium vapor and a closed cavity.

[0037] The percentage of carbon residue area after welding is used to characterize the degree of carbon contamination around the weld and near the interface after welding. It is obtained by statistical analysis using the microscopic image thresholding method and is expressed as the percentage of the carbon residue area to the observed area. The lower the value, the less carbon contamination. The area of ​​residual carbon after welding in Example 1 was 0.7%, which was significantly lower than 6.8% in Comparative Example 2 and 9.5% in Comparative Example 3. The carbon residue area of ​​Comparative Example 1 was 0.4%, but its contact angle, spreading area, porosity and shear strength were all poor, indicating that low carbon residue does not necessarily mean that it has the ability to break the film and activate the film. Example 1 demonstrates that high wettability and high strength are achieved while maintaining low carbon residue, indicating that the continuous synergistic release layer achieves synergistic protection against carbon black and fluorine-containing film rupture. Comparative Example 3 showed the highest carbon residue, indicating that when only a fluorine-loaded core is used, the high-temperature release of fluorine-containing organic components may produce more carbon deposits, thus proving the necessity of a continuous synergistic release layer.

[0038] The residual amount of fluoride ions after welding is used to characterize the risk of migratable fluoride residues after welding. It is detected by ion chromatography on the surface extract after welding and converted to μg / cm² per unit area. The residual fluoride ion content after welding in Example 1 was 0.18 μg / cm², which was lower than that in Comparative Example 3 (0.52 μg / cm²). The results show that although Example 1 releases fluorine-containing small molecule gas, the continuous synergistic release layer and the quartz fiber cloth covering material jointly restrict the migration of solid residues and make the release process more orderly, resulting in a low level of fluorine residues that can migrate after welding. Comparative Examples 1, 2, and 4 do not contain fluorinated alkane activation sources, so the residual amount of fluoride ions is recorded as 0. However, this cannot be used to prove that they have the ability to break down fluorine-containing gas phase films.

[0039] The weld interface continuity rate is used to characterize the continuity of the effective metallurgical bonding area in the metallographic section of the weld. It is obtained by metallographic section image analysis and is expressed as the percentage of the continuous bonding length to the total length of the designed weld interface. The higher the value, the more complete the interface connection. The weld interface continuity rate of Example 1 was 96.4%, which was higher than that of Comparative Example 1 (68.5%), Comparative Example 2 (74.2%), Comparative Example 3 (82.1%) and Comparative Example 4 (91.3%). The results show that Example 1 not only improved surface wetting and macro-spreading, but also improved the continuous bonding quality in the weld cross-section direction; Although Comparative Example 3 had a second release peak, its interface continuity rate was still significantly lower than that of Example 1, indicating that carbon residue and uneven local gas dispersion would damage the interface continuity when there was no anti-carbon black outer layer. The interface continuity rate of Comparative Example 4 is lower than that of Example 1, indicating that the magnesium vapor film breaking route is still affected by the distribution of magnesium vapor, cavity sealing and solder morphology, making it difficult to obtain the same interface continuity as in Example 1 in complex semiconductor heat dissipation structures.

[0040] In summary, the parameters in Table 1, from nine aspects including release timing, activation margin, wetting behavior, spreading ability, weld defects, joint strength, carbon residue, fluorine residue and interface continuity, jointly verified the technical effect of Example 1. Example 1, compared to Comparative Example 1, demonstrates that fluorine-containing vapor phase film breaking can solve the problem of difficult removal of oxide films in conventional vacuum brazing; Example 1, compared to Comparative Example 2, demonstrates that the non-contact vacuum brazing activation material, unlike ordinary organic flux, can reduce carbon residue and meet the requirements of clean semiconductor bonding. Example 1, compared to Comparative Example 3, demonstrates that the continuous synergistic release layer is not an arbitrary added component, but a key structure that suppresses carbon black, reduces porosity, improves strength, and reduces fluorine residue. Example 1, compared to Comparative Example 4, demonstrates that this example can achieve better wettability, weld density, and interface continuity without relying on magnesium vapor assistance and a closed cavity. Therefore, Table 1 supports the synergistic technical logic formed between the fluorine-loaded core, the continuous synergistic release layer, and the inorganic fiber breathable constraint packaging material in this embodiment, and proves that it can complete the gas phase activation before the solder melts, suppress carbon black residue during the activation process, and achieve the comprehensive technical effect of non-contact clean connection in the semiconductor vacuum brazing scenario.

[0041] In this embodiment, the vacuum brazing activation material, used in the scenario of connecting the aluminum alloy cold plate and nickel-plated copper heat sink in the heat dissipation structure of a semiconductor power module, can prevent the release of carbon black by first releasing carbon black in the first release peak temperature range of 220℃-310℃ and the release of fluorine-containing small molecule gas at the second release peak termination temperature of 520℃. This ensures that the main activation process is completed before the solidus temperature of the aluminum-silicon brazing filler metal reaches 577℃, forming a process buffer with an activation margin of 57℃ before the solder solidus temperature. This process buffer avoids the problem that the aluminum-silicon brazing filler metal has melted but the alumina film, nickel oxide, and copper oxide composite film are not sufficiently loosened, thereby reducing the brazing filler metal contact angle to 23° and increasing the brazing filler metal spreading surface. The weld area was increased to 184 mm², the weld porosity was reduced to 1.8%, the joint shear strength was increased to 68.5 MPa, and the weld interface continuity was increased to 96.4%. At the same time, the proportion of residual carbon area after welding was controlled to 0.7%, and the residual amount of fluoride ions after welding was controlled to 0.18 μg / cm². This shows that it can achieve low-pollution, high-wetting and low-pollution vacuum brazing connection between aluminum alloy cold plates and nickel-plated copper heat sinks without relying on magnesium vapor to seal the cavity or directly introducing ordinary organic flux into the weld area. It is especially suitable for semiconductor packaging heat dissipation structures such as SiC power modules and IGBT power modules that are sensitive to the continuity of heat dissipation channels, interface thermal resistance and particulate contamination.

[0042] Example 2 In this embodiment, the vacuum brazing activation material is used for surface activation before vacuum brazing between a stainless steel packaging frame and a nickel-plated copper substrate for semiconductor packaging. In this application scenario, the surface of the stainless steel packaging frame has a composite film of chromium oxide and iron oxide, and the surface of the nickel-plated copper substrate has a nickel oxide film. Under conventional vacuum brazing conditions, the above oxide film will reduce the wetting ability of the silver-copper solder on the surface to be soldered, and easily cause incomplete welding at the weld edge, local voids, and reduced air tightness. In this embodiment, by selecting porous alumina particles loaded with perfluorohexane and forming a continuous synergistic release layer on the outer surface of the fluorine-containing loaded core, the vacuum brazing activation material first releases anti-carbon black gas before the silver-copper solder melts, and then releases fluorine-containing small molecule gas, so as to achieve gas-phase activation of the stainless steel packaging frame and the nickel-plated copper substrate.

[0043] Please see Figure 1 Specifically, the porous inorganic carrier is porous alumina particles; The average pore size of the porous alumina particles is 20 μm; The specific surface area of ​​the porous alumina particles is 80 m² / g; 70g of the porous alumina particles were desorbed at 180°C for 3 hours. After desorption treatment, the moisture content of the porous alumina particles was measured to be 0.32%. The fluoroalkane is perfluorohexane; The perfluorohexane has an acid value of 0.02 mg KOH / g; The perfluorohexane has a water content of 260 ppm; Add 70g of the porous alumina particles and 18g of the perfluorohexane into a sealed impregnation container; The perfluorohexane was immersed at 45°C for 120 minutes to allow it to enter the pores of the porous alumina particles. A fluorine-loaded core was obtained; The perfluorohexane loading in the fluorinated loaded core is 20.5% of the mass of the fluorinated loaded core; The mass loss rate of the fluorine-containing loaded core after being sealed at 25°C for 24 hours, based on its initial mass, was 1.1%. The thickness of the continuous synergistic release layer is 180 μm; The mass of the continuous synergistic release layer is 18% of the mass of the fluorine-loaded core; The continuous synergistic release layer covers 96% of the outer surface of the fluorine-containing loaded core; The nitrogen content of the nitrocellulose is 12.1%; The particle size D50 of the aluminum hydroxide is 8 μm; The silica sol-coated ammonium bicarbonate includes an ammonium bicarbonate core material and a silica sol-cured layer covering the outer surface of the ammonium bicarbonate core material. The mass of the silica sol cured layer is 12% of the mass of the ammonium bicarbonate core material; Mix 4g of the nitrocellulose, 10g of the aluminum hydroxide, 6g of the silica sol-coated ammonium bicarbonate and 16g of the silica sol; Stirring at 30℃ for 50 minutes yields a carbon black synergistic slurry; The carbon black synergistic slurry is coated on the outer surface of the fluorine-containing loaded core, so that a continuous synergistic release layer is formed on the outer surface of the fluorine-containing loaded core; The mass change rate after drying at 60℃ to 0.4% after two consecutive weighings is 0. Then, it is compressed into tablets under a pressure of 12 MPa; A dried composite molded body with a thickness of 1.8 mm and a porosity of 28% was obtained. The dried composite molded body is packed into an alumina fiber paper packaging material with an average air permeability of 25 μm and sealed. The vacuum brazing activation material of this embodiment is obtained; The vacuum brazing activated material was analyzed by thermogravimetric-mass spectrometry (TGA) at a vacuum level of 10. -2 Pa, heating rate is 10℃ / min; The test results show that the temperature range of the first release peak of the vacuum brazing activation material is 210℃-305℃, and the first release peak includes a peak with m / z=18 channel and a peak with m / z=44 channel. The second release peak of the vacuum brazing activation material has an onset temperature of 365°C and an end temperature of 650°C. The second release peak includes a channel peak of m / z=19 and a channel peak of m / z=69. In brazing applications, the vacuum brazing activation material is placed 25mm outside the area to be brazed between the stainless steel encapsulation frame and the nickel-plated copper substrate. The vacuum brazing activation material does not come into direct contact with the silver-copper brazing filler metal, the stainless steel encapsulation frame, and the nickel-plated copper substrate. The solidus temperature of the silver-copper brazing filler metal is 780°C, and the second release peak termination temperature of 650°C is 130°C lower than the solidus temperature of the silver-copper brazing filler metal, so that the vacuum brazing activation material can complete the anti-carbon black synergistic release and fluorine-containing small molecule gas release before the silver-copper brazing filler metal melts.

[0044] In this embodiment, the vacuum brazing activation material is still used for surface activation before vacuum brazing between the aluminum alloy cold plate and the nickel-plated copper heat sink in the heat dissipation structure of the semiconductor power module; The aluminum alloy cold plate, the nickel-plated copper heat sink, and the aluminum-silicon brazing filler are all the same as in Example 1; The solidus temperature of the aluminum-silicon brazing filler metal is 577°C. The difference between this embodiment and Embodiment 1 is that the porous inorganic carrier is selected as porous alumina particles, the fluorinated alkane is selected as perfluorohexane, and by controlling the loading amount, the thickness of the continuous synergistic release layer, the coverage and the room temperature mass loss rate, the vacuum brazing activation material can still form a preliminary anti-carbon black release and subsequent fluorine-containing small molecule gas release before the solder melts in the same aluminum-silicon brazing scenario. This setup illustrates that, without changing the semiconductor brazing application, solder system, or comparative system, by changing the porous inorganic carrier and the type of fluorinated alkane, it is still possible to achieve the synergistic effect between the fluorinated loaded core, the continuous synergistic release layer, and the non-contact activation structure.

[0045] In specific implementation, porous alumina particles are selected as porous inorganic carriers, and the average pore size of the porous alumina particles is 20μm and the specific surface area is 80m² / g. When the average pore size is 20 μm, perfluorohexane can enter the pores of the porous alumina particles and maintain appropriate pore constraint, which avoids insufficient impregnation due to too small a pore size, and also avoids premature volatilization in the early stage of vacuuming due to too large a pore size. When the specific surface area is 80 m² / g, it can provide a stable adsorption interface for perfluorohexane and enable the fluorine-containing loaded core to form an identifiable second release peak in subsequent thermogravimetric-mass spectrometry detection. If the specific surface area is too low, the adsorption capacity of perfluorohexane will be insufficient, and the release intensity of fluorine-containing small molecule gases will decrease. If the specific surface area is too high, the perfluorohexane release process may have a tailing effect, causing the termination temperature of the second release peak to be too close to the solidus temperature of the aluminum-silicon solder.

[0046] 70g of the porous alumina particles were desorbed at 180℃ for 3h. After desorption, the moisture content of the porous alumina particles was measured to be 0.32%. The 180°C desorption temperature and 3h desorption time are used to remove adsorbed water and low-boiling impurities from the pores of porous alumina particles, so that perfluorohexane can enter the pores and form a stable load. If the desorption treatment is insufficient, the water content can easily approach or exceed 0.5%. Residual water in the pores will occupy adsorption sites and lead to a decrease in the perfluorohexane loading. If the desorption temperature or time is increased excessively, the improvement in reducing the moisture content will be limited, and it may lead to powder agglomeration, affecting the uniformity of the coating of the fluorine-loaded core by the anti-carbon black synergistic slurry.

[0047] In this embodiment, perfluorohexane was selected as the fluoroalkane. The perfluorohexane has an acid value of 0.02 mg KOH / g and a moisture content of 260 ppm. The perfluorohexane has a low boiling point and a high fluorine content, making it suitable for forming an early release window of fluorine-containing small molecules under the constraint of the porous alumina particles. The acid value of 0.02 mg KOH / g can reduce the risk of uncontrolled corrosion of aluminum alloy cold plates and nickel-plated copper heat sink surfaces by acidic impurities; The moisture content of 260 ppm can reduce phase separation during the impregnation stage and abnormal gas release in the early stage of vacuum heating. If the acid value or moisture content is too high, it can easily cause fluctuations in the release peak, increase the residue around the weld, and increase the risk of localized corrosion on the metal surface.

[0048] 70g of the porous alumina particles and 18g of the perfluorohexane were added to a sealed impregnation container and impregnated at 45°C for 120 minutes to allow the perfluorohexane to enter the pores of the porous alumina particles, thereby obtaining a fluorine-loaded core. The 45°C impregnation temperature can improve the wetting efficiency of perfluorohexane on the pores of porous alumina particles, while avoiding rapid volatilization of perfluorohexane during the impregnation process. If the impregnation temperature is too low, the rate at which perfluorohexane enters the pores will decrease, which can easily lead to uneven loading. If the impregnation temperature is too high, the evaporation pressure inside the sealed impregnation container will increase, which can easily cause fluctuations in the load. The 120-minute immersion time allows perfluorohexane to reach a relatively stable loading state within the pores of porous alumina particles. If the impregnation time is too short, the pores will not be filled sufficiently; If the impregnation time is too long, the loading capacity will increase only slightly, and the risk of loss of low-boiling components will increase.

[0049] The perfluorohexane loading in the fluorinated loaded core is 20.5% of the mass of the fluorinated loaded core; The mass loss rate of the fluorine-containing loaded core after being sealed at 25°C for 24 hours, based on its initial mass, was 1.1%. The 20.5% loading ensures that sufficient fluorine-containing small molecule gas is released before the solder melts, so as to act on the alumina film on the surface of the aluminum alloy cold plate and the composite oxide film on the surface of the nickel-plated copper heat sink. If the loading is too low, the gas phase activation capacity will be insufficient; If the load is too high, it can easily increase the risk of fluorine residue and localized corrosion. The mass loss rate of 1.1% indicates that the fluorine-containing loaded core can maintain a good retention capacity of active ingredients during temporary storage and transfer at room temperature, avoiding rapid loss of fluorinated alkanes after preparation.

[0050] In this embodiment, the thickness of the continuous synergistic release layer is 180 μm, the mass of the continuous synergistic release layer is 18% of the mass of the fluorine-containing load core, and the coverage of the continuous synergistic release layer on the outer surface of the fluorine-containing load core is 96%. The 180μm thickness can form a continuous carbon black release prevention area on the outside of the fluorine-containing load core and maintain the escape channel of fluorine-containing small molecule gas. If the thickness is too small, the fluorine-containing load core is prone to local exposure, causing the fluorine-containing components to be released directly without a prior carbon black protection environment. If the thickness is too large, the resistance to the escape of fluorine-containing small molecule gases will increase, and the second release peak may shift to the later stage. The 18% mass ratio provides sufficient oxygen, water, and gas release components while avoiding excessive overall gas release. The 96% coverage reduces the exposed core region, allowing the first release peak to form stably before the second release peak.

[0051] The nitrogen content of the nitrocellulose is 12.1%, and the particle size D50 of the aluminum hydroxide is 8 μm. The silica sol-coated ammonium bicarbonate includes an ammonium bicarbonate core material and a silica sol-cured layer coated on the outer surface of the ammonium bicarbonate core material, wherein the mass of the silica sol-cured layer is 12% of the mass of the ammonium bicarbonate core material. When the nitrogen content of the nitrocellulose is 12.1%, it can provide moderate oxygen release in the lower temperature range. If the nitrogen content is too low, the oxygen release capacity is insufficient. If the nitrogen content is too high, the decomposition rate is too fast and may cause local gas release shock. When the aluminum hydroxide particle size D50 is 8μm, it can be uniformly dispersed in the synergistic release slurry. When the particle size is too large, the dispersion uniformity decreases, and when the particle size is too small, the slurry viscosity increases and the coating continuity is affected. When the mass of the silica sol cured layer is 12% of the mass of the ammonium bicarbonate core material, it can delay the release of ammonium bicarbonate and prevent its premature decomposition during stirring at 30°C and drying at 60°C. If the silica sol curing layer is too thin, ammonium bicarbonate is easily lost prematurely; If the silica sol curing layer is too thick, the gas release process will be delayed excessively, making it difficult to form an effective expansion channel in the first release peak temperature zone.

[0052] Mix 4g of nitrocellulose, 10g of aluminum hydroxide, 6g of silica sol-coated ammonium bicarbonate and 16g of silica sol, and stir at 30°C for 50 minutes to obtain a carbon black synergistic slurry. This formulation enables the carbon black-resistant synergistic slurry to simultaneously possess oxygen release, water release, gas release, and film-forming capabilities. The stirring temperature of 30°C can ensure the fluidity of the slurry and prevent the premature decomposition of silica sol-coated ammonium bicarbonate. The 50-minute stirring time ensures that all components are evenly dispersed. If the stirring time is too short, local component segregation is likely to occur in the continuous synergistic release layer; If the stirring time is too long, the viscosity of the slurry will change more, affecting the stability of the coating thickness.

[0053] The carbon black synergistic slurry is coated on the outer surface of the fluorine-containing loaded core, so that a continuous synergistic release layer is formed on the outer surface of the fluorine-containing loaded core; The core-outer layer composite with the continuous synergistic release layer was dried at 60°C until the mass change rate of two consecutive weighings was 0.4%. The material is then pressed into a sheet under a pressure of 12 MPa to obtain a dried composite molded body with a thickness of 1.8 mm and a porosity of 28%. The drying temperature of 60°C can remove free water and low-boiling components from the slurry, while reducing the loss of perfluorohexane. The mass change rate of 0.4% indicates that the drying process has stabilized; If drying is insufficient, abnormal gas release will occur during subsequent vacuum heating. If the drying process is excessive, the continuous synergistic release layer is prone to cracking. The 12MPa compression pressure enables the dried composite molded body to have sufficient strength and maintain pore connectivity. If the pressure is too low, powder will easily fall off and the coating layer will peel off. If the pressure is too high, the porosity will decrease and gas release will be hindered; The 1.8mm thickness and 28% porosity can balance the requirements of gas release, structural integrity and non-contact cleanliness.

[0054] The dried composite molded body is packed into an alumina fiber paper packaging material with an average air permeability of 25 μm and sealed to obtain the vacuum brazing activated material of this embodiment. The alumina fiber paper packaging material has the characteristics of vacuum and high temperature resistance and low particle shedding; The 25μm average pore size allows carbon black gas and fluorine-containing small molecule gas to pass through, while restricting powder particles and solid residues from entering the weld area of ​​the heat dissipation structure of the semiconductor power module. If the pore size is too small, the diffusion of the released gas will be hindered and may cause the release peak to shift backward. If the venting aperture is too large, the risk of fine powder and residue penetrating the packaging material increases, which is detrimental to cleanliness control of semiconductor soldering.

[0055] The vacuum brazing activated material was analyzed by thermogravimetric-mass spectrometry (TGA) at a vacuum level of 10. -2 Pa, heating rate is 10℃ / min; The test results show that the temperature range of the first release peak of the vacuum brazing activation material is 210℃-305℃, and the first release peak includes a peak with m / z=18 channel and a peak with m / z=44 channel. The second release peak of the vacuum brazing activation material has an onset temperature of 365°C and an end temperature of 530°C. The second release peak includes a channel peak of m / z=19 and a channel peak of m / z=69. The solidus temperature of the aluminum-silicon brazing filler metal is 577°C, and the second release peak termination temperature of 530°C is 47°C lower than the solidus temperature of the aluminum-silicon brazing filler metal. The 47°C activation margin ensures that the fluorine-containing small molecule gas is released before the aluminum-silicon solder melts, and that the oxide film on the surface to be soldered is activated in the gas phase. If the termination temperature of the second release peak is close to 577℃, the activation of the fluorine-containing gas phase overlaps with the melting process of the solder, which can easily cause wetting lag and local non-soldering.

[0056] In brazing applications, the vacuum brazing activation material is placed 25mm outside the area to be brazed between the aluminum alloy cold plate and the nickel-plated copper heat sink. The vacuum brazing activation material does not come into direct contact with the aluminum-silicon brazing filler metal, the aluminum alloy cold plate and the nickel-plated copper heat sink. The 25mm placement distance allows fluorine-containing small molecule gas to reach the area to be welded and act on the alumina film, nickel oxide and copper oxide composite film, while also preventing solid residues of the activating material from entering the weld. If the distance is too close, the surface of the packaging material may be near the weld and increase the risk of particulate contamination; If the distance is too far, the concentration of the gas-phase activated components reaching the surface to be welded will decrease, resulting in insufficient loosening of the oxide film. Therefore, in this embodiment, the perfluorohexane is loaded onto porous alumina particles, the anti-carbon black gas is released in advance by a continuous synergistic release layer, and non-contact constraint is achieved by alumina fiber paper packaging material. This enables the vacuum brazing activation material to complete the gas phase activation before the solder melts in the same aluminum-silicon brazing application scenario as in Embodiment 1, and reduces the risk of insufficient solder spreading, weld voids, and carbon residue.

[0057] In this embodiment, while maintaining the same conditions as in Example 1 for the aluminum alloy cold plate, nickel-plated copper heat sink, aluminum-silicon brazing filler metal, and vacuum brazing, the average pore size of the alumina porous particles is 20 μm, the specific surface area is 80 m² / g, and the water content after desorption treatment is 0.32%. Combined with perfluorohexane having an acid value of 0.02 mg KOH / g and a moisture content of 260 ppm, the perfluorohexane loading in the fluorinated load core is stably maintained at 20.5%. Furthermore, the mass loss rate of the fluorinated load core after being sealed at 25°C for 24 hours, based on its initial mass, is only 1.1%. This result demonstrates that Example 2 more effectively solves the problem of premature loss of low-boiling-point fluoroalkanes during preparation, transfer, and furnace loading, making the activated material suitable for prefabricated feeding and multi-station turnover in the batch brazing of semiconductor power modules. Simultaneously, the continuous synergistic release layer has a thickness of 180 μm, a mass of 18% of the mass of the fluorinated load core, and a coverage of 96%, enabling the first release... The peak temperature range is stable between 210℃ and 305℃, and the termination temperature of the second release peak is 530℃, which is lower than the solidus temperature of aluminum-silicon brazing filler metal of 47℃. This release window can complete the gas phase activation of the alumina film, nickel oxide and copper oxide composite film before the aluminum-silicon brazing filler metal melts, and avoids the premature release of fluorine-containing components leading to insufficient effective concentration. In addition, the thickness of the dried composite molded body is 1.8mm and the porosity is 28%. Combined with the alumina fiber paper packaging material with an average permeable pore size of 25μm and a non-contact placement distance of 25mm, it can limit the entry of powder particles and solid residues into the weld area while ensuring gas permeability. Therefore, the special advantage of Example 2 is that it improves the storage stability, batch preparation consistency and pre-furnace activity retention of the low-boiling-point fluoroalkane activation material. It is especially suitable for the actual manufacturing scenario in semiconductor power module production lines that require the pre-preparation of activation materials, batch loading of aluminum alloy cold plates and nickel-copper heat sinks, and the requirement for stable and repeatable activation effects before brazing.

[0058] Example 3 In this embodiment, the vacuum brazing activation material is used for surface activation before vacuum brazing between the metallized ceramic substrate and the copper-based heat sink. In this application scenario, the metallization layer on the surface of the metallized ceramic substrate is prone to forming a composite film of nickel oxide and copper oxide, and the surface of the copper-based heat sink is prone to forming a copper oxide film. Under conventional vacuum brazing conditions, the above-mentioned oxide film will reduce the spreading continuity of the copper-based solder and easily cause local non-bonding at the interface, increased thermal resistance, and decreased heat dissipation reliability of power devices. In this embodiment, by controlling the pressing pressure, thickness, and porosity of the dried composite molding body, and using boron nitride fiber felt as an inorganic fiber breathable constraint packaging material, the vacuum brazing activation material can complete the anti-carbon black synergistic release and fluorine-containing small molecule gas release in a non-contact manner before the copper-based solder melts.

[0059] Please see Figure 1 and Figure 2 Specifically, the fluorine-containing loaded core and the continuous synergistic release layer are prepared according to S1-S2 in Example 1; The core-outer layer complex with the continuous synergistic release layer formed thereon was dried at 65°C. The drying endpoint was defined as a mass change rate of 0.35% between two consecutive weighings. The dried core-outer layer composite was compressed into tablets under a pressure of 25 MPa. A dried composite molded body is obtained; The thickness of the dried composite molded body is 3.5 mm; The porosity of the dried composite molded body is 18%; The inorganic fiber breathable restraint packaging material is boron nitride fiber felt; The average air permeability pore size of the boron nitride fiber felt is 60 μm; The boron nitride fiber felt had a mass loss rate of 0.4% after being kept in a vacuum environment at 900℃ for 30 minutes. The dried composite molded body is inserted into the boron nitride fiber felt and sealed. The vacuum brazing activation material of this embodiment is obtained; The vacuum brazing activated material was detected by thermogravimetric-mass spectrometry. The detected vacuum level is 10. -3 Pa; The heating rate is 15℃ / min; The test results show that the first release peak temperature range of the vacuum brazing activation material is 230℃-325℃; The first release peak includes a channel peak at m / z=18 and a channel peak at m / z=44; The second release peak initiation temperature of the vacuum brazing activation material is 420℃; The termination temperature of the second release peak of the vacuum brazing activation material is 780℃. The second release peak includes a channel peak at m / z=19 and a channel peak at m / z=69; In brazing applications, the vacuum brazing activation material is placed 35mm outside the area to be brazed between the metallized ceramic substrate and the copper-based heat sink. The vacuum brazing activation material does not come into direct contact with the copper-based brazing filler metal, the metallized ceramic substrate, and the copper-based heat dissipation base plate. The solidus temperature of the copper-based brazing filler metal is 850°C. The second release peak termination temperature of 780°C is lower than the solidus temperature of the copper-based solder, which is 70°C. This enables the vacuum brazing activation material to complete the anti-carbon black synergistic release and fluorine-containing small molecule gas release before the copper-based brazing filler metal melts.

[0060] This embodiment is an extended embodiment of the application of claim 1 in a high solids line solder system, used to illustrate the applicability of the vacuum brazing activation material in the surface activation process before vacuum brazing between a metallized ceramic substrate and a copper-based heat sink. This embodiment does not directly use the aluminum-silicon brazing filler metal comparative system in Example 1. Instead, it is used to verify that under the condition that the solidus temperature of copper-based brazing filler metal is 850°C, the vacuum brazing activation material can still complete the anti-carbon black synergistic release and fluorine-containing small molecule gas release before the solder melts by controlling the release peak timing. The metallization layer on the surface of the metallized ceramic substrate typically includes a nickel layer, a copper layer, or a nickel-copper composite layer. The metallization layer is prone to forming a nickel oxide and copper oxide composite film during storage, assembly, and heating. Copper oxide film is easily formed on the surface of copper-based heat sink base plate, and the copper oxide film will reduce the spreading ability of copper-based solder on the surface of heat sink base plate. If the oxide film cannot be sufficiently loosened or transformed before the copper-based solder melts, the molten copper-based solder is prone to problems such as interruption of the spreading front, local non-welding, increased thermal resistance of the weld, and decreased heat dissipation reliability of power devices. Therefore, this embodiment focuses on controlling the pressing pressure, thickness, porosity, and air permeability of the inorganic fiber air-permeable constraint packaging material of the dried composite molded body, so that the activated material can maintain structural integrity, unobstructed gas release, and non-contact cleanliness in high-temperature vacuum brazing scenarios.

[0061] In this embodiment, the fluorine-containing loaded core and the continuous synergistic release layer are prepared according to S1-S2 in Example 1; By using the same fluorine-containing loaded core and continuous synergistic release layer as in Example 1, it can be ensured that this example is consistent with Example 1 in terms of core activation material structure, that is, both include a fluorine-containing loaded core for delayed release of fluorine-containing small molecule gas, and a continuous synergistic release layer for prior release of oxygen, water and gas components. The purpose of this setting is to eliminate the influence of the difference in formulation between the fluorine-loaded core and the continuous synergistic release layer on the release behavior, so that this embodiment mainly examines the influence of tableting parameters, inorganic fiber breathable constraint packaging material and high-temperature copper-based solder window on the application effect of vacuum brazing activated material. If the fluorine-containing loaded core, continuous synergistic release layer, tableting conditions and packaging conditions are changed simultaneously in this embodiment, it is difficult to determine which technical feature the change in release peak and the improvement in brazing effect specifically originate from, which is not conducive to explaining the coordination relationship between the various technical nodes in claim 1.

[0062] The core-outer layer complex with the continuous synergistic release layer was dried at 65°C, and the drying endpoint was defined as a mass change rate of 0.35% between two consecutive weighings. The drying temperature of 65°C can remove free water and low-boiling components in the continuous synergistic release layer, while still being significantly lower than the boiling point of the fluoroalkanes in Example 1, thus reducing the loss of activated components in the fluorine-loaded core during the drying stage. If the drying temperature is too low, the moisture and low-boiling solvent in the continuous co-release layer will be difficult to be fully discharged, and undesigned gas release is likely to occur when the temperature is raised later, resulting in the first release peak becoming wider or occurring abnormally early. If the drying temperature is too high, the fluorinated alkanes in the fluorine-loaded core are prone to volatilization loss during the preparation stage, which reduces the intensity of the second release peak and causes insufficient activation of the fluorine-containing gas phase before the solder melts. The mass change rate of 0.35% after two consecutive weighings indicates that the dried composite system has basically reached a stable state, and can take into account both the structural strength of the continuous synergistic release layer and the activity retention of the fluorine-containing loaded core. If drying is stopped when the rate of change in mass is too large, it indicates that there are still many volatile components remaining in the system, which can easily affect the atmosphere stability during the vacuum brazing process.

[0063] The dried core-outer layer composite was compressed into tablets under a pressure of 25 MPa to obtain a dried composite molded body. The 25MPa pressure is higher than the pressing pressure in Examples 1 and 2, and is suitable for the application scenario of copper-based brazing filler metal at higher temperatures in this example, because the brazing temperature between the metallized ceramic substrate and the copper-based heat sink is higher, and the activation material needs higher structural integrity during furnace loading, vacuuming and heating. If the tableting pressure is too low, the dried composite molded body is prone to powder loss during handling and packaging, and the continuous synergistic release layer may peel off locally, which in turn leads to instability of the first release peak. If the tableting pressure is too high, the pores inside the dried composite molded body will be excessively compacted, increasing the escape resistance of fluorine-containing small molecule gases and carbon black release gases. The second release peak may shift later and approach the solidus temperature of the copper-based solder. Therefore, a pressure of 25 MPa can achieve a balance between mechanical strength and gas release channels, making the activated material less prone to breakage in a high-temperature vacuum environment while still maintaining controllable release capability.

[0064] The thickness of the dried composite molded body is 3.5 mm, and the porosity is 18%. The 3.5mm thickness provides sufficient loading of activating material, enabling it to release a sufficient amount of gaseous activating components on the outer side of the large soldering area of ​​the metallized ceramic substrate and the copper-based heat sink. If the thickness is too small, the total amount of fluorine-containing loaded core and continuous synergistic release layer in the unit activation material will be insufficient, and the gas phase activation components will be difficult to cover a large area to be welded. If the thickness is too large, the internal heat conduction and gas escape paths of the activated material become longer, which can easily lead to tailing of the release peak and increase the risk of the second release peak termination temperature shifting backward. The 18% porosity ensures that the dried composite molded body has the necessary gas channels while maintaining the mechanical integrity after tableting. If the porosity is too low, the diffusion of the released gas will be hindered, and both the first and second release peaks may shift towards higher temperatures. If the porosity is too high, the strength of the molded body will decrease, and it will be prone to powder shedding or cracking, which is not conducive to cleanliness control in semiconductor brazing scenarios.

[0065] The inorganic fiber breathable restraint packaging material is boron nitride fiber felt, the average breathable pore size of the boron nitride fiber felt is 60μm, and the mass loss rate of the boron nitride fiber felt after being kept in a vacuum environment at 900℃ for 30min is 0.4%. The reason for choosing boron nitride fiber felt is that it has high thermal stability, low risk of particulate contamination and good chemical inertness, making it suitable for high-temperature vacuum brazing environments corresponding to copper-based brazing filler metals. The 60μm average pore size ensures that the water vapor and carbon dioxide-related gases generated by the first release peak and the fluorine-containing small molecule gases generated by the second release peak can pass through the packaging material smoothly and diffuse to the area to be welded. If the average pore size is too small, the resistance of the released gas through the packaging material will increase, which may cause the activated gas to be retained inside the packaging material and shift the release peak to the later stage. If the average pore size is too large, the packaging material's ability to contain solid powder, debris and inorganic residues will decrease, which will easily increase the risk of particulate contamination on the surface of the metallized ceramic substrate. The mass loss rate after heat preservation in a vacuum environment of 900℃ for 30 minutes was 0.4%, indicating that boron nitride fiber felt still has good quality stability in an environment higher than the solidus temperature of copper-based brazing filler metal in this embodiment. If the packaging material has a high high-temperature mass loss rate, it may release polluting volatiles or become structurally embrittled, which is not conducive to the clean connection of the heat dissipation structure of semiconductor power devices.

[0066] The dried composite molded body is inserted into the boron nitride fiber felt and sealed to obtain the vacuum brazing activated material of this embodiment. The sealing process is used to confine the dried composite molded body inside the boron nitride fiber felt, so that no powder escapes during the vacuum furnace evacuation, heating and heat preservation process. This constraint method does not prevent the release of gas-phase activated components, but rather utilizes the permeable pore structure of boron nitride fiber felt to achieve gas passage and solid retention; If the packaging is not sealed, powder may fall off the edges of the tablet body during handling or heating. Solid residues entering the weld will cause inclusions, local incomplete welding, and dielectric contamination. Therefore, boron nitride fiber felt covering and sealing is an important structural step for achieving non-contact clean applications.

[0067] The vacuum brazing activated material was analyzed by thermogravimetric-mass spectrometry (TGA) at a vacuum level of 10. -3 Pa, heating rate is 15℃ / min; The 10 -3 The Pa vacuum degree is used to simulate the low-pressure environment during vacuum brazing of copper-based brazing filler metals, so that the release peak detection conditions are close to the actual brazing conditions. If the detection pressure is significantly higher than the actual vacuum brazing pressure, the release behavior may be affected by the gas mass transfer resistance and cannot accurately reflect the furnace release characteristics. The heating rate of 15℃ / min is close to the heating process in high-temperature copper-based brazing, and can reflect the release sequence of the activated material under rapid heating conditions. If the heating rate is too low, the release peak may broaden and shift towards lower temperatures; If the heating rate is too high, the release peak may shift towards higher temperatures and shorten the activation time before the solder melts.

[0068] The test results show that the temperature range of the first release peak of the vacuum brazing activation material is 230℃-325℃, and the first release peak includes a peak with m / z=18 channel and a peak with m / z=44 channel. The m / z=18 channel peak is used to characterize the water vapor-related release signal, and the m / z=44 channel peak is used to characterize the carbon dioxide-related release signal. The first release peak is located at 230℃-325℃, indicating that the continuous synergistic release layer can produce water and gas release behavior before the fluorine-containing load core enters the main release stage, and establish a loose and diffused environment for the subsequent release of fluorine-containing small molecule gases. If the first release peak is too low, the release process may have ended in the early stage of vacuum brazing, making it difficult to form an effective synergy with the subsequent release of fluorine-containing small molecule gases. If the first release peak is too high, it may overlap with the second release peak, resulting in a lag in the anti-carbon black effect and an inability to suppress carbon deposition before a large amount of fluorine-containing components are released.

[0069] The second release peak of the vacuum brazing activation material has an onset temperature of 420°C and an end temperature of 780°C. The second release peak includes a channel peak of m / z=19 and a channel peak of m / z=69. The m / z=19 channel peak is used to characterize the fluorine-related fragment signal in fluorine-containing small molecules, and the m / z=69 channel peak is used to characterize the fluorine-containing carbon fragment related signal. The second release peak started at 420℃, indicating that the fluorine-containing load core began to release fluorine-containing small molecule gas after the continuous synergistic release layer formed a preliminary anti-carbon black environment. The second release peak termination temperature is 780℃, which is lower than the solidus temperature of copper-based solder, 850℃, forming an activation margin of 70℃ between the two. The 70°C activation margin ensures that the fluorine-containing small molecule gas is released before the copper-based solder melts, so that the oxide film on the surface of the metallized ceramic substrate and the copper-based heat sink is activated by the gas phase first. If the termination temperature of the second release peak is higher than or close to the solidus temperature of the copper-based solder, the release of fluorine-containing small molecule gas will overlap with the solder melting process, resulting in the molten solder still being in contact with the unactivated oxide film. If the termination temperature of the second release peak is too low, the fluorine-containing small molecule gas may be released prematurely before the temperature of the workpiece to be welded reaches an effective activation state, resulting in a decrease in the utilization rate of the activation gas.

[0070] In brazing applications, the vacuum brazing activation material is placed 35mm outside the area to be brazed between the metallized ceramic substrate and the copper-based heat sink plate. The vacuum brazing activation material does not directly contact the copper-based brazing filler metal, the metallized ceramic substrate, and the copper-based heat sink plate. The 35mm placement distance is suitable for a large-area planar connection structure between the metallized ceramic substrate and the copper-based heat sink, which enables the fluorine-containing small molecule gas to diffuse to the area to be soldered in a vacuum environment and reduces the risk of solid residues entering the interface. If the boron nitride fiber felt is placed too close to the weld edge, it may increase the risk of particulate contamination and localized residue. If the placement distance is too far, the concentration of fluorine-containing small molecule gas reaching the surface to be welded will decrease, resulting in insufficient loosening of the oxide film; Therefore, a placement distance of 35mm can achieve a balance between gas phase activation efficiency and clean isolation.

[0071] This embodiment utilizes a high pressing pressure, a large molded body thickness, moderate porosity, and a high-temperature stable boron nitride fiber felt packaging material to enable the vacuum brazing activation material to adapt to the high-temperature vacuum brazing environment corresponding to copper-based brazing filler metals. Among them, the continuous synergistic release layer forms the first release peak at 230℃-325℃, providing an environment for water and gas release in advance; The fluorine-loaded core forms a second release peak at 420℃-780℃, releasing fluorine-containing small molecule gas and completing the main activation process before the solidus temperature of copper-based solder is 850℃. Boron nitride fiber felt packaging allows gas to pass through and restricts the migration of solid residues, enabling activating materials to act on the surfaces of metallized ceramic substrates and copper-based heat sinks in a non-contact manner. Therefore, this embodiment can reduce the risks of discontinuous copper-based solder spreading, local non-welding at the interface, increased weld thermal resistance, and solid contamination entering the weld area, and further proves that the preparation method described in claim 1 is feasible and applicable to high-temperature semiconductor heat dissipation connection scenarios.

[0072] In this embodiment, under the high-temperature vacuum brazing scenario of a metallized ceramic substrate and a copper-based heat sink, the dried composite molded body is formed by drying at 65°C until the mass change rate after two consecutive weighings is 0.35%, and then pressing it into a sheet under 25MPa pressure. This achieves a thickness of 3.5mm and a porosity of 18%, thus balancing structural integrity during the high-temperature furnace loading process with the escape channels for released gases. These structural parameters can prevent the activated material from experiencing powder shedding, cracking, or delayed release in the high-temperature vacuum environment corresponding to copper-based brazing filler metal. Simultaneously, the boron nitride fiber felt has an average permeable pore size of 60μm, and its mass loss rate after being held at 900°C in a vacuum environment for 30 minutes is 0.4%, indicating that it can maintain low volatility and low contamination constraints under conditions close to the high-temperature brazing window of copper-based brazing filler metal. Based on this, the first release peak temperature range is 230℃-325℃, the second release peak starting temperature is 420℃, and the second release peak ending temperature is 780℃. This forms a 70℃ activation margin before the solidus temperature of the copper-based solder (850℃), allowing the fluorine-containing small molecule gas to act on the nickel oxide and copper oxide composite film on the surface of the metallized ceramic substrate and the copper oxide film on the surface of the copper-based heat sink before the copper-based solder melts. Therefore, the special advantage of Example 3 is that it improves the anti-powdering ability, high-temperature coating constraint ability, and large-area interface gas phase activation ability of the vacuum brazing activation material in high-temperature semiconductor heat dissipation connection scenarios. It is especially suitable for heat dissipation structures of power devices such as metallized ceramic substrates and copper-based heat sinks that are sensitive to interface thermal resistance, weld continuity, and the cleanliness of the insulating ceramic surface.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended technical solutions and their equivalents.

Claims

1. A method for preparing a vacuum brazing activation material based on fluorinated alkanes, characterized in that, Includes the following steps: S1. A porous inorganic support with a pore size of 1μm-100μm is desorbed at 120℃-300℃ for 1h-4h. After cooling to 30℃-60℃, it is added to a sealed impregnation container with fluoroalkanes with a boiling point of 40℃-220℃ and a fluorine mass fraction of 30%-80% at a mass ratio of 40-80:10-40. The container is then impregnated at a temperature 10℃-40℃ lower than the boiling point of the fluoroalkanes for 30min-180min, so that the fluoroalkanes enter the pores of the porous inorganic support to obtain a fluorine-loaded core. S2. Nitrocellulose, aluminum hydroxide, silica sol-coated ammonium bicarbonate and silica sol are mixed in a mass ratio of 1-10:1-15:1-15:5-25 and stirred at 20℃-50℃ for 20min-90min to obtain a carbon black synergistic slurry. The carbon black synergistic slurry is coated on the outer surface of the fluorine-containing loaded core to form a continuous synergistic release layer on the outer surface of the fluorine-containing loaded core, thus obtaining a core-outer layer composite. S3. The core-outer layer composite is dried at 20℃-80℃, the drying temperature is 20℃-60℃ lower than the boiling point of the fluoroalkane, and the drying endpoint is when the mass change rate of two consecutive weighings is less than 0.5%. Then, it is pressed into tablets to obtain the dried composite molded body. S4. The dried composite molded body is placed into an inorganic fiber breathable constraint packaging material and sealed to obtain a vacuum brazing activated material. The vacuum brazing activated material is subjected to a vacuum degree of 10. -4 Under the detection conditions of thermogravimetric-mass spectrometry (TGS-MS) at Pa-10 Pa and heating rates of 5℃ / min-20℃ / min, the system exhibits a first release peak formed by the continuous synergistic release layer and a second release peak formed by the fluorine-containing loaded core. The temperature range of the first release peak is 180℃-350℃, the starting temperature range of the second release peak is 350℃-450℃, the termination temperature of the second release peak is 20℃-80℃ lower than the solidus temperature of the solder to be used, the starting temperature of the second release peak is lower than the termination temperature of the second release peak, and the first release peak is formed before the second release peak.

2. The method for preparing a vacuum brazing activation material based on fluorinated alkanes according to claim 1, characterized in that, The porous inorganic carrier is one of calcium fluoride porous particles, alumina porous particles, boron nitride porous particles and magnesium fluoride porous particles. The porous inorganic carrier has a specific surface area of ​​20 m² / g-200 m² / g, and the moisture content of the porous inorganic carrier after the desorption treatment is less than 0.5%.

3. The method for preparing a vacuum brazing activation material based on fluoroalkanes according to claim 2, characterized in that, The fluoroalkane is one of perfluorohexane, perfluoroheptane, perfluorooctane, and 1H,1H,2H,2H-perfluorooctane. The fluoroalkane has an acid value of less than 0.05 mg KOH / g and a moisture content of less than 500 ppm.

4. The method for preparing a vacuum brazing activation material based on fluorinated alkanes according to claim 3, characterized in that, The loading amount of fluorinated alkanes in the fluorinated loaded core is 12%-35% of the mass of the fluorinated loaded core; The mass loss rate of the fluorine-containing loaded core after being sealed at 25°C for 24 hours, based on its initial mass, is less than 2%.

5. The method for preparing a vacuum brazing activation material based on fluoroalkane according to claim 4, characterized in that, The thickness of the continuous synergistic release layer is 50μm-500μm; The mass of the continuous synergistic release layer is 5%-30% of the mass of the fluorine-containing loaded core; The continuous synergistic release layer covers 90%-100% of the outer surface of the fluorine-containing loaded core.

6. The method for preparing a vacuum brazing activation material based on fluoroalkane according to claim 5, characterized in that, The nitrogen content of the nitrocellulose is 10%-13.5%; The particle size D50 of the aluminum hydroxide is 0.5μm-20μm; The silica sol-coated ammonium bicarbonate comprises an ammonium bicarbonate core material and a silica sol-cured layer coated on the outer surface of the ammonium bicarbonate core material, wherein the mass of the silica sol-cured layer is 5%-25% of the mass of the ammonium bicarbonate core material.

7. The method for preparing a vacuum brazing activation material based on fluoroalkane according to claim 6, characterized in that, The pressure for tablet compression is 5MPa-30MPa; The thickness of the dried composite molded body is 0.5mm-5mm; The porosity of the dried composite molded body is 10%-45%.

8. The method for preparing a vacuum brazing activation material based on fluoroalkanes according to claim 7, characterized in that, The inorganic fiber breathable restraint packaging material is one of quartz fiber cloth, alumina fiber paper, and boron nitride fiber felt. The average pore size of the inorganic fiber breathable restraint packaging material is 5μm-100μm; The inorganic fiber breathable restraint packaging material has a mass loss rate of less than 1% after being kept in a vacuum environment at 900℃ for 30 minutes.

9. The method for preparing a vacuum brazing activation material based on fluoroalkanes according to claim 8, characterized in that, Under the aforementioned thermogravimetric-mass spectrometry detection conditions; The first release peak includes a channel peak at m / z=18 and a channel peak at m / z=44; The second release peak includes a channel peak at m / z=19 and a channel peak at m / z=69.

10. The method for preparing a vacuum brazing activation material based on fluoroalkane according to claim 8, characterized in that, The semiconductor workpiece that is compatible with the vacuum brazing activation material is one of the following: aluminum alloy cold plate, stainless steel packaging frame, nickel-plated copper heat sink and metallized ceramic substrate. The solder to be used is one of aluminum-silicon solder, silver-copper solder, and copper-based solder, and the solidus temperature of the solder to be used is 550℃-900℃.

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