CN115319327B - Preparation method of low-temperature active solder - Google Patents

Abstract

A preparation method of low-temperature active solder comprises the following steps: firstly, pre-treating an active metal foil to remove an oxide film, then adding a metal plating layer on the surface of the active metal foil to prepare an active alloy foil, then preparing an Sn-based solder foil to a proper thickness, arranging the active metal foil between the Sn-based solder foils to form the active solder foil in an intercalation mode, then carrying out three-dimensional restraint on the active solder foil by using a clamp, and finally obtaining the low-temperature active solder through high-temperature smelting and calendaring treatment. According to the invention, the welding flux and the clamp are separated by the diaphragm, so that direct welding of the welding flux and the clamp is avoided, the welding flux is easy to take out, and the clamping constraint problem is solved; through intercalation assembly among the foils, the uniform distribution of the active elements in the solder is promoted, the component segregation problem of the active elements is relieved, and the uniformity of the active elements is improved.

Description

A method for preparing low-temperature active solder

Technical field

The present invention relates to the technical field of welding material preparation, and in particular to a method for preparing low-temperature active solder.

Background technique

Graphene is a carbonaceous material with a single-layer two-dimensional honeycomb lattice structure, which is composed of carbon atoms closely packed by sp2 hybridization. Thanks to its unique atomic arrangement, graphene has excellent electrical properties. The electron mobility of graphene at room temperature is as high as 15,000cm ² /(V·S), which is ten times higher than that of silicon material. In addition, graphene also has excellent thermal and mechanical properties, with a thermal conductivity of 5300W/mK and a theoretical Young's modulus of up to 1.0TPa. It is currently one of the materials with the highest thermal conductivity and strength, and has both high toughness and high strength. Flexible.

The excellent physical properties of graphene make it have important application prospects in new materials, communication engineering, electronic devices, etc. However, its wide application inevitably brings about problems in graphene connection. Due to the high chemical stability of the graphene surface, traditional solders are difficult to spread and wet on the surface. Active solders that add active elements to promote wetting have been gradually developed, such as Ag-Cu-Ti solder, Sn-Ti solder, etc.

There are currently two main methods for preparing active solder: arc melting and powder metallurgy. Arc melting refers to an electrothermal metallurgical method that uses electrical energy to generate high-temperature arcs to smelt metals. However, problems such as composition deviation, specific gravity segregation, uneven distribution of active elements, and poor solder reliability are inevitable during the arc melting process. The powder metallurgy method refers to mixing a certain proportion of metal powder through ball milling, forming and sintering to prepare the required solder. However, active metal powders have high specific surface area and high activity, and are easily oxidized during the ball milling process. After mixing, the purity is often low. Therefore, the active solder prepared by powder metallurgy has higher oxygen content and weaker welding performance. In addition, the melting temperature required for Sn-based active solder is often higher than the liquidus line of Sn. Due to the high activity of the active solder, it is easy to weld with the fixture during the melting process and the solder is difficult to remove.

Contents of the invention

In order to solve the above problems, the present invention proposes a low-temperature active solder preparation method. The specific technical solution is:

A method for preparing low-temperature active solder, including the following steps: first pre-treating the active metal foil to remove the oxide film, then adding a metal plating layer on the surface of the active metal foil to prepare an active alloy foil, and then preparing Sn-based solder foil to a suitable thickness, The active metal foil is intercalated and assembled between Sn-based solder foils to form an active solder foil. The active solder foil is then three-dimensionally restrained with a clamp. Finally, the low-temperature active solder is obtained through high-temperature smelting and rolling.

Further, the active metal foil is one or more of Ti foil, Mg foil or Cr foil, and the thickness of the active metal foil after pretreatment is 1 to 10um.

Further, the metal plating layer is one or more of Ni, Cu or Ag.

Further, the Sn-based solder foil is one or more of pure Sn, Sn-Ag alloy, Sn-Bi alloy, Sn-In alloy, Sn-Cu alloy or Sn-Ag-Cu alloy, and its shape and size are Consistent with the active alloy foil, the thickness is controlled according to the mass ratio of base elements in the active solder.

Further, the intercalation assembly is an alternating assembly of Sn-based solder foil and active alloy foil, in which the top layer and the bottom layer are both Sn-based solder foils, and their thickness is not less than that of the Sn-based solder foil and active alloy foil in the middle interlayer. times.

Further, the assembled active solder foil is put into a clamp that matches its shape and size, and a diaphragm is used to separate the active solder foil from the clamp.

Further, the high-temperature smelting is carried out at a temperature of 500 to 1000°C for 0.5 to 4 hours.

Further, after high-temperature sintering is completed, the sample is taken out and surface polished and mechanically rolled alternately until the appropriate thickness.

Beneficial effects of the present invention:

(1) Through pre-treatment and adding surface coating, the oxide film on the surface of the active metal foil is removed, while avoiding the oxidation of active elements in subsequent processes and improving the purity of the solder;

(2) The solder and the clamp are separated by a diaphragm, which avoids direct welding of the solder and the clamp. The solder is easy to remove, solving the problem of clamping constraints;

(3) Through intercalation assembly between foils, the uniform distribution of active elements in the solder is promoted, the problem of component segregation of active elements is alleviated, and the uniformity of active elements is improved.

Description of drawings

Figure 1 is a schematic diagram of the intercalation assembly of the present invention.

In the picture: 1 active metal foil, 2 Sn-based solder foil.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

As shown in Figure 1, a low-temperature active solder preparation method includes the following steps: first pre-treat the active metal foil 1 to remove the oxide film, then add a metal plating layer on the surface of the active metal foil 1 to prepare an active alloy foil, and then prepare The Sn-based solder foil 2 is adjusted to a suitable thickness, and the active metal foil 1 is placed between the Sn-based solder foils 2 and assembled to form an active solder foil. The active solder foil is then three-dimensionally restrained with a clamp, and is finally obtained by high-temperature smelting and rolling. Low temperature active solder.

Wherein, the active metal foil 1 is one or more of Ti foil, Mg foil or Cr foil, etc., and the thickness of the active metal foil 1 after pretreatment is 1-10um; the selected thickness of the active metal foil 1 should be greater than The target thickness is to reduce the thickness of the active metal foil 1 after treatment. By controlling the treatment time, the active metal foil 1 can be adjusted to a suitable thickness.

Wherein, the metal coating is one or more of Ni, Cu or Ag, and its preparation method includes but is not limited to plasma spraying, electroplating or magnetron sputtering.

Wherein, the Sn-based solder foil 2 is one or more of pure Sn, Sn-Ag alloy, Sn-Bi alloy, Sn-In alloy, Sn-Cu alloy or Sn-Ag-Cu alloy, and its shape and size are Consistent with the active alloy foil, the thickness is controlled according to the mass ratio of base elements in the active solder.

Wherein, the intercalation assembly is an alternating assembly of Sn-based solder foil 2 and active alloy foil, in which the top layer and the bottom layer are both Sn-based solder foil 2, and their thickness is not less than that of the Sn-based solder foil 2 and active alloy foil in the middle interlayer. twice; the Sn-based solder foil has at least 6 layers, and the corresponding active alloy foil has at least 5 layers.

Among them, the assembled active solder foil is put into a clamp that matches its shape and size, and the active solder foil and the clamp are separated by a diaphragm. Because the molecular distance increases after the metal melts, the volume expands due to thermal expansion and contraction, as well as the generation of intermetallic compounds, so a certain amount of space must be left when designing the fixture.

It should be noted that due to the high activity of the active solder, it can be welded to almost all fixtures during the high-temperature melting process, so it needs to be separated by a diaphragm. Preferably, the separator is a graphene film; using graphene as a separator, its interlayer force is small, and it is very easy to peel off from the active solder after smelting, and the graphene can also be easily polished clean; at the same time, the chemical properties of graphene are very Stable, it can avoid contamination caused by atomic diffusion during the active solder melting process.

Wherein, the high-temperature smelting is carried out at a temperature of 500-1000°C for 0.5-4 hours, and the smelting process is carried out in an inert gas protection or a vacuum environment not higher than 1×10 ^-3 Pa.

Among them, after high-temperature sintering is completed, the sample is taken out and surface polished and mechanically rolled alternately until the appropriate thickness.

The resulting solder is not prone to segregation during the continued welding process, and the solder joints have good uniformity. As the purity of the solder increases, the flexibility of the solder joints is also improved, making it suitable for the preparation of highly flexible solder joints.

Example 1:

In this embodiment, a Ti foil with a thickness of 20um is selected, and the added coating is a pure Ni layer. The proportion of Ti is 5wt.% and the proportion of Ni is 0.5wt.%. The specific operation steps are as follows:

First, cut the Ti foil into square pieces of 100mm×100mm, and cut out 5 pieces for later use. Treat with 10% HF for 45 seconds to remove the oxide film on the surface of the titanium foil, rinse with pure water for 1 minute, then treat with a hydrogenation solution of concentrated H ₂ SO ₄ and concentrated HCl with a ratio of 1:3 for 45 minutes, rinse with pure water for 3 minutes, and finally use dust-free paper Dry and set aside. The thickness of the Ti foil after treatment is reduced, and the Ti foil can be adjusted to the appropriate thickness by controlling the treatment time; the treated Ti foil is weighed, and the mass of Ni and Sn are calculated according to the mass ratio: after processing 5 pieces of titanium foil The total mass is 4.506g. After calculation, the mass of Ni should be 0.451g and the mass of Sn should be 85.163g.

The components of the nickel plating solution and the concentrations of each component are as follows: nickel sulfate hexahydrate 240g/L, nickel chloride hexahydrate 40g/L, and boric acid 30g/L. The electroplating temperature is 45~50℃, the current density is 10A/ ^dm2 , and the electroplating time is 45s. After electroplating is completed, rinse with pure water for 3 minutes, dry and set aside.

According to the intercalation assembly method, prepare 6 pieces of Sn foil. The thickness of the top and bottom Sn foils is not less than twice that of the middle layer. Calculated from the mass and density formula of Sn: the middle layer Sn foil thickness is 150um, a total of 4 pieces, the top and bottom Sn foil thickness is 300um, a total of 2 pieces, a total of 6 pieces. Take an appropriate amount of pure Sn, calender it to a predetermined thickness, and cut it into 100mm×100mm square pieces. Finally, the Sn foil thickness is fine-tuned according to the total mass until it meets the set mass ratio.

The Sn foil and alloy Ti foil are assembled in an intercalation manner, wrapped with graphene on the outside, and placed in a stainless steel fixture. The clamp is designed as a rectangular box with dimensions of 100mm×100mm×1.5mm. After the assembly is completed, it is sintered at a temperature of 900°C and a vacuum of 6.0×10 ^-4 for 1 hour. Cool the furnace to room temperature, take it out, polish the surface-welded graphene with 400-grit sandpaper, and then roll it to a suitable thickness to obtain the required Sn-5Ti-0.5Ni low-temperature active solder.

Example 2:

In this embodiment, a Ti foil with a thickness of 20um is selected, and the added coating is a pure Cu layer. The proportion of Ti is 5wt.% and the proportion of Cu is 0.5wt.%. The specific operation steps are as follows:

First, cut the Ti foil into square pieces of 100mm×100mm, and cut out 5 pieces for later use. Treat with 10% HF for 45 seconds to remove the oxide film on the surface of the titanium foil, rinse with pure water for 1 minute, then treat with a hydrogenation solution of concentrated H ₂ SO ₄ and concentrated HCl with a ratio of 1:3 for 45 minutes, rinse with pure water for 3 minutes, and finally use dust-free paper Dry and set aside. Weigh the treated Ti foil and calculate the mass of Ni and Sn respectively according to the mass ratio: the total mass of the 5 pieces of titanium foil after treatment is 4.506g. After calculation, the mass of Cu should be 0.451g and the mass of Sn should be 85.163 g.

The components of the copper plating solution and the concentrations of each component are as follows: copper pyrophosphate 75g/L, potassium pyrophosphate trihydrate 310g/L, and ammonium citrate 40g/L. The electroplating temperature is 40-45°C, the current density is 5A/dm ² , and the electroplating time is 2 minutes. After electroplating is completed, rinse with pure water for 3 minutes, dry and set aside.

According to the intercalation assembly method, prepare 6 pieces of Sn foil. The thickness of the top and bottom Sn foils is not less than twice that of the middle layer. Calculated from the mass and density formula of Sn: the middle layer Sn foil thickness is 150um, a total of 4 pieces, the top and bottom Sn foil thickness is 300um, a total of 2 pieces, a total of 6 pieces. Take an appropriate amount of pure Sn, calender it to a predetermined thickness, and cut it into 100mm×100mm square pieces. Finally, the Sn foil thickness is fine-tuned according to the total mass until it meets the set mass ratio.

The Sn foil and alloy Ti foil are assembled in an intercalation manner, wrapped with graphene on the outside, and placed in a stainless steel fixture. The clamp is designed as a rectangular box with dimensions of 100mm×100mm×1.5mm. After the assembly is completed, it is sintered at a temperature of 900°C and a vacuum of 6.0×10 ^-4 for 1 hour. Cool the furnace to room temperature, take it out, polish the surface-welded graphene with 400-grit sandpaper, and then roll it to a suitable thickness to obtain the required Sn-5Ti-0.5Cu low-temperature active solder.

Example 3:

In this embodiment, a Ti foil with a thickness of 20um is selected, and the added coating is a pure Ni layer. The proportion of Ti is 3wt.% and the proportion of Ni is 0.3wt.%. The specific operation steps are as follows:

First, cut the Ti foil into square pieces of 100mm×100mm, and cut out 5 pieces for later use. Treat with 10% HF for 45 seconds to remove the oxide film on the surface of the titanium foil, rinse with pure water for 1 minute, then treat with a hydrogenation solution of concentrated H ₂ SO ₄ and concentrated HCl with a ratio of 1:3 for 45 minutes, rinse with pure water for 3 minutes, and finally use dust-free paper Dry and set aside. Weigh the treated Ti foil, and calculate the mass of Ni and Sn respectively according to the mass ratio: the total mass of the 5 pieces of titanium foil after treatment is 4.506g. After calculation, the mass of Ni should be 0.451g, and the mass of Sn should be 145.243 g.

The components of the nickel plating solution and the concentrations of each component are as follows: nickel sulfate hexahydrate 240g/L, nickel chloride hexahydrate 40g/L, and boric acid 30/L. The electroplating temperature is 45~50℃, the current density is 10A/ ^dm2 , and the electroplating time is 45s. After electroplating is completed, rinse with pure water for 3 minutes, dry and set aside.

According to the intercalation assembly method, prepare 6 pieces of Sn foil. The thickness of the top and bottom Sn foils is not less than twice that of the middle layer. Calculated from the mass and density formula of Sn: the middle layer Sn foil thickness is 150um, a total of 4 pieces, the top and bottom Sn foil thickness is 300um, a total of 2 pieces, a total of 6 pieces. Take an appropriate amount of pure Sn, calender it to a predetermined thickness, and cut it into 100mm×100mm square pieces. Finally, the Sn foil thickness is fine-tuned according to the total mass until it meets the set mass ratio.

The Sn foil and alloy Ti foil are assembled in an intercalation manner, wrapped with graphene on the outside, and placed in a stainless steel fixture. The clamp is designed as a rectangular box with dimensions of 100mm×100mm×2.2mm. After the assembly is completed, it is sintered at a temperature of 900°C and a vacuum degree of 6.0×10 ^-4 for 1 hour. Cool the furnace to room temperature, take it out, polish the surface-welded graphene with 400-grit sandpaper, and then roll it to a suitable thickness to obtain the required Sn-3Ti-0.3Ni low-temperature active solder.

Claims (4)

1. The preparation method of the low-temperature active solder is characterized by comprising the following steps of: firstly, pre-treating an active metal foil to remove an oxide film, then adding a metal plating layer on the surface of the active metal foil to prepare an active alloy foil, then preparing an Sn-based solder foil to a proper thickness, arranging the active alloy foil between the Sn-based solder foils to form an active solder foil in an intercalation mode, then carrying out three-dimensional restraint on the active solder foil by using a clamp, and finally obtaining low-temperature active solder through high-temperature smelting and calendaring treatment;

the intercalation assembly is formed by alternately assembling an Sn-based solder foil and an active alloy foil, wherein the top layer and the bottom layer are both Sn-based solder foils, the thickness of the Sn-based solder foil of the middle layer is 150um, and the thicknesses of the Sn-based solder foils at the top and the bottom are 300um;

loading the assembled active solder foil into a clamp matched with the shape and the size of the active solder foil, and separating the active solder foil and the clamp by a diaphragm;

the active metal foil is Cr foil, the thickness of the active metal foil after pretreatment is 1-10 um, and the diaphragm is a graphene film; the high-temperature smelting is carried out for 0.5 to 4 hours at the temperature of 500 to 1000 ℃.

2. The method of claim 1, wherein the metal plating layer is one or more of Ni, cu or Ag.

3. The method according to claim 1, wherein the Sn-based solder foil is one or more of pure Sn, sn-Ag alloy, sn-Bi alloy, sn-In alloy, sn-Cu alloy, and Sn-Ag-Cu alloy, and has a shape and size consistent with those of the active alloy foil, and a thickness regulated according to a mass ratio of the base element In the active solder.

4. The method for preparing a low-temperature active solder according to claim 1, wherein after the high-temperature melting is completed, the sample is taken out, and surface polishing and mechanical rolling are alternately performed until a proper thickness is reached.