Preparation method of foil of Ag-Cu-Ge medium-temperature brazing filler metal

Abstract

The invention relates to the technical field of medium-temperature brazing filler metal preparation, and particularly discloses a foil preparation method of Ag-Cu-Ge medium-temperature brazing filler metal, which comprises the following steps: weighing Cu, Ge, Sn, In and / or Ga and the balance of Ag according to atomic percent, and carrying out high-vacuum induction melting to obtain a master alloy; melting the master alloy under the covering protection of B2O3, casting into a cast ingot, carrying out annealing treatment on the cast ingot, carrying out multi-pass hot rolling under a temperature control condition, and finally annealing under a vacuum condition, so as to obtain the brazing filler metal foil with the thickness of 30-100 mu m. Through the synergistic effect of component design and smelting, annealing and hot rolling processes, stable preparation of the Ag-Cu-Ge medium-temperature brazing filler metal from a cast state to a foil state is achieved, and the obtained foil has the melting characteristic suitable for medium-temperature brazing at 400-600 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medium-temperature brazing filler metal preparation, and particularly relates to a foil preparation method of Ag-Cu-Ge medium-temperature brazing filler metal. BACKGROUND

[0002] As an important means of connecting metal and non-metal materials, brazing technology is widely used in the fields of aerospace, electronic packaging, chemical industry, nuclear energy and the like. As a filler material, the performance of the brazing filler metal directly affects the welding quality. Under the background of the development of electronic devices towards miniaturization and high power, the demand for medium-temperature brazing filler metal suitable for different temperature ranges is increasing, and the research on brazing filler metal with a melting temperature of 400-600 DEG C is still insufficient.

[0003] At present, medium-temperature brazing filler metal is mainly based on Au-Ag and Ag-Cu alloys, and elements such as Ge, Si, In and Sn are added to reduce the melting point. However, such alloys still have problems such as poor processing performance, wide melting range and high cost in practical application.

[0004] For example, when the content of Sn in Ag-Cu-Sn alloy exceeds 15wt.%, the plasticity of the alloy decreases significantly due to the formation of brittle electronic compounds, and the alloy is difficult to process and shape; although Ag-Cu-In-Sn alloy can realize medium-temperature brazing, the melting range of the alloy is wide, which is not conducive to the control of the welding process. In addition, the high silver content leads to the increase of cost, which limits the wide application of the alloy.

[0005] Ag-Cu-Ge alloy has a melting temperature suitable for medium-temperature brazing, a narrow melting range and a moderate price, and has important industrial value. However, the preparation of the alloy into foil is limited by the coarse primary phase and intermetallic compound phase.

[0006] Therefore, it is of important industrial application value to develop a method for preparing medium-temperature brazing filler metal foil. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a foil preparation method of Ag-Cu-Ge medium-temperature brazing filler metal, which can effectively solve the problems in the background.

[0008] To solve the above problems, the technical scheme adopted by the present application is as follows: a foil preparation method of Ag-Cu-Ge medium-temperature brazing filler metal, comprising the following steps: S1. The raw materials are weighed according to the atomic percentage, wherein Cu is 29-31%, Ge is 24-30%, Sn, In and / or Ga is 1-10%, and the balance is Ag; S2. The raw materials are placed in a graphite crucible and melted in a high-vacuum induction melting furnace under an argon protective atmosphere to obtain a master alloy; S3. Put the master alloy into an alumina crucible, cover the surface of the master alloy with B2O3 powder without crystal water, heat to 700-800℃ to melt the alloy, and then pour into a preheated graphite mold at 300-400℃ to form an ingot; S4. Put the ingot into an electric resistance furnace, anneal at 450-500℃ for 5-10 hours to obtain a rolling stock alloy; S5. Hot roll the rolling stock alloy in multiple passes using a hot rolling mill with heatable rollers, the roller temperature is 300-500℃, and the stock alloy is heated to 350-500℃ before hot rolling; S6. Put the rolled foil into a vacuum annealing furnace, anneal at 350-500℃ for 30 minutes to obtain an Ag-Cu-Ge medium temperature solder foil.

[0009] Preferably, at least one of Sn, In and Ga is selected as an additive element.

[0010] Preferably, the B2O3 powder is used to isolate air and absorb impurities on the surface of the alloy melt during alloy melting, and the B2O3 powder without crystal water is prepared by the following method: heat industrial grade B2O3 powder at 1200℃ for 10 hours to remove crystal water, and grind to 10-50μm after cooling.

[0011] Preferably, in the hot rolling step, the roller speed is controlled at 0.1-0.5m / min.

[0012] Preferably, the reduction amount of each pass in the hot rolling process is 0.05-0.1mm, and the inter-pass holding time is 2 minutes.

[0013] Preferably, the foil obtained after multiple hot rolling passes has a thickness of 30-100μm.

[0014] Preferably, the obtained Ag-Cu-Ge medium temperature solder foil is used for medium temperature brazing process with a melting temperature of 400-600℃.

[0015] Preferably, the master alloy in step S3 is kept at 700-800℃ for 2-5 minutes before pouring.

[0016] Compared with the prior art, the present application provides a foil preparation method for Ag-Cu-Ge medium temperature solder, which has the following beneficial effects: By using B2O3 covering protection during melting and pouring, combined with post-casting annealing and controlled temperature hot rolling process, the as-cast structure of the alloy is improved, providing a processable organizational basis for subsequent multiple hot rolling passes, so that the originally difficult-to-process Ag-Cu-Ge alloy can be prepared into a foil with a thickness of 30-100μm.

[0017] By adding appropriate amounts of Sn, In, or Ga, the resulting Ag-Cu-Ge alloy has a well-defined melting initiation and termination temperature, which can meet the melting characteristics requirements of medium-temperature brazing processes at 400–600℃.

[0018] While keeping the cost of Ag-Cu-Ge alloys under control, the transformation of brazing filler metal from traditional block and wire shapes to foil form has been achieved, expanding its application in the field of medium-temperature brazing. Attached Figure Description

[0019] Figure 1 A schematic diagram of the microstructure of Ag-Cu-Ge-Sn / Ga / In solder alloy under as-cast conditions; Figure 2 This is a schematic diagram illustrating the evolution of the microstructure of the Ag-Cu30-Ge30 alloy foil with a thickness of 60 μm according to the present invention. Figure 3 DSC curves for Ag-Cu30-Ge27-In3 and Ag-Cu30-Ge25-In5 alloys. Detailed Implementation

[0020] The present invention will now be described with reference to embodiments. It should be understood that the embodiments described herein are for the purpose of more clearly illustrating the invention, and not for limiting the scope of the invention.

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Reference Figures 1-3 The purpose of this invention is to provide a method for preparing Ag-Cu-Ge medium-temperature solder foil. By optimizing the alloy composition and preparation process, a foil product with uniform structure, good toughness, suitable melting temperature and controllable cost can be obtained.

[0023] The method of the present invention includes the following steps: weighing Ag, Cu, Ge and Sn / In / Ga elements according to atomic percentage, obtaining a master alloy by high vacuum induction melting; covering and protecting with B2O3 powder, melting in an alumina crucible and casting into a preheated graphite mold; after annealing the ingot, performing multiple hot rolling under temperature-controlled rolling conditions, and finally obtaining a tough foil of the target thickness by vacuum annealing.

[0024] Example 1: Preparation of Ag-Cu-Ge-In quaternary alloy foil Step 1: Weigh out 4.3140g Ag, 1.907g Cu, 2.1063g Ge, and 1.1873g In; Step 2: Place the raw material in a graphite crucible and melt it under argon protection in a high-vacuum induction melting furnace; Step 3: Place the smelted alloy in an alumina crucible, cover it with dehydrated B2O3 powder, melt it at 740~760℃ and hold it at that temperature for 2 minutes, then pour it into a cold graphite mold. Step 4: Using rolls heated to 300°C, hot rough rolling is performed on the ingot after preheating at 400~450°C at a speed of 0.1~0.5m / min, with a reduction of 0.05~0.1mm per pass and a holding time of 2 minutes between passes, until the thickness is about 100μm. Step 5: Perform hot finishing under the same conditions until the foil thickness is 30~50μm; Step 6: Anneal the foil at 350°C for 30 minutes in a vacuum annealing furnace to obtain an alloy foil with good toughness; like Figure 1 The image shows the microstructure of the Ag-Cu-Ge-In alloy in this embodiment under as-cast conditions. It can be seen that after high-vacuum induction melting and casting, the alloy mainly consists of silver-based solid solution and Cu-Ge phases, with a relatively uniform microstructure. The vacuum degree of the high-vacuum induction melting is ≤5×10⁻⁶. -3 Pa.

[0025] Example 2: Preparation of Ag-Cu-Ge-Sn quaternary alloy foil Step 1: Weigh out 4.3129g Ag, 1.9052g Cu, 2.1066g Ge, and 0.1130g Sn; Step 2: Place the raw material in a graphite crucible and melt it under argon protection in a high-vacuum induction melting furnace; Step 3: Place the smelted alloy in an alumina crucible, cover it with dehydrated B2O3 powder, melt it at 740~760℃ and hold it at that temperature for 2 minutes, then pour it into a cold graphite mold. Step 4: Using rolls heated to 300°C, hot rough rolling is performed on the ingot after preheating at 400~450°C at a speed of 0.1~0.5m / min, with a reduction of 0.05~0.1mm per pass and a holding time of 2 minutes between passes, until the thickness is about 100μm. Step 5: Perform hot finishing under the same conditions until the foil thickness is 30~50μm; Step 6: Anneal the foil at 350°C for 30 minutes in a vacuum annealing furnace to obtain an alloy foil with good toughness.

[0026] Example 3: Preparation of Ag-Cu-Ge-Ga quaternary alloy foil Step 1: Weigh out 4.3138g Ag, 1.9070g Cu, 2.1059g Ge, and 0.6972g Ga; Step 2: Place the raw material in a graphite crucible and melt it under argon protection in a high-vacuum induction melting furnace; Step 3: Place the smelted alloy in an alumina crucible, cover it with dehydrated B2O3 powder, melt it at 740~760℃ and hold it at that temperature for 2 minutes, then pour it into a cold graphite mold. Step 4: Using rolls heated to 300°C, hot rough rolling is performed on the ingot after preheating at 400~450°C at a speed of 0.1~0.5m / min, with a reduction of 0.05~0.1mm per pass and a holding time of 2 minutes between passes, until the thickness is about 100μm. Step 5: Perform hot finishing under the same conditions until the foil thickness is 30~50μm; Step 6: Anneal the foil at 350°C for 30 minutes in a vacuum annealing furnace to obtain an alloy foil with good toughness.

[0027] The preparation process of Examples 2 (Ag-Cu-Ge-Sn) and 3 (Ag-Cu-Ge-Ga) is the same as that of Example 1, and their as-cast microstructures can also be referred to. Figure 1 understand; Each embodiment exhibits the same characteristics as during the hot rolling process. Figure 2 Similarly, its microstructure gradually evolves during the rolling process. This microstructure evolution process shows that the combination of hot rolling parameters used in this invention can achieve the continuous preparation of Ag-Cu-Ge alloy foils without material cracking. The effects of different In contents or Sn and Ga substitution elements on melting behavior can be observed through... Figure 3 The DSC curves shown are used for verification and comparison. The thermal analysis curves show that the alloy has a clear melting start temperature and end temperature, and the melting range is relatively concentrated.

[0028] Based on Examples 1–3, it can be confirmed that within the composition range defined by this invention, by adding appropriate amounts of Sn, In or Ga, and in conjunction with the preparation process described above, the resulting Ag-Cu-Ge alloy can maintain the melting temperature range required for medium-temperature brazing, while avoiding the adverse effects of an excessively wide melting range on the stability of the welding process.

[0029] The results indicate that, through the synergistic effect of material composition and processing technology, this invention provides a feasible preparation route for the engineering application of Ag-based medium-temperature solders.

[0030] The technical solutions of the various embodiments can be combined with each other, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0031] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing foil of Ag-Cu-Ge based medium-temperature solder, characterized in that, Includes the following steps: S1. Weigh the raw materials according to atomic percentage, wherein Cu is 29-31%, Ge is 24-30%, Sn, In and / or Ga is 1-10%, and the balance is Ag; S2. The raw material is placed in a graphite crucible and melted in a high-vacuum induction melting furnace under an argon protective atmosphere to obtain a master alloy; S3. The master alloy is placed in an alumina crucible, and its surface is covered with dehydrated B2O3 powder. After heating to 700-800°C to melt the alloy, it is cast into a graphite mold preheated to 300-400°C to form an ingot. S4. Place the ingot in a resistance furnace and anneal it at 450-500°C for 5-10 hours to obtain a rolled billet alloy. S5. The rolled billet alloy is hot rolled in multiple passes using a hot rolling mill with heatable rolls. The roll temperature is 300-500°C, and the billet alloy is heated to 350-500°C before hot rolling. S6. Place the rolled foil in a vacuum annealing furnace and anneal at 350-500℃ for 30 minutes to obtain Ag-Cu-Ge medium-temperature solder foil.

2. The method for preparing foil of Ag-Cu-Ge based medium-temperature solder according to claim 1, characterized in that, At least one of Sn, In, and Ga is selected as the added element.

3. The method for preparing foil of Ag-Cu-Ge based medium-temperature solder according to claim 1, characterized in that, The B2O3 powder is used to isolate air and adsorb impurities on the surface of the alloy melt during the alloy melting process.

4. The method for preparing a foil of Ag-Cu-Ge medium-temperature solder according to claim 1, characterized in that, In the hot rolling step, the roll speed is controlled between 0.1 and 0.5 m / min.

5. The method for preparing a foil of Ag-Cu-Ge medium-temperature solder according to claim 4, characterized in that, The amount of pressure applied in each pass during the hot rolling process is 0.05 to 0.1 mm, and the temperature is maintained for 2 minutes between passes.

6. The method for preparing a foil of Ag-Cu-Ge medium-temperature solder according to claim 5, characterized in that, The foil thickness obtained after multiple hot rolling processes is 30–100 μm.

7. A method for preparing a foil of Ag-Cu-Ge based medium-temperature solder according to claim 1 or 6, characterized in that, The obtained Ag-Cu-Ge-based medium-temperature brazing foil is used in medium-temperature brazing processes with melting temperatures of 400–600℃.

8. The method for preparing a foil of Ag-Cu-Ge medium-temperature solder according to claim 1, characterized in that, In step S3, the master alloy is held at 700-800℃ for 2-5 minutes before casting.

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