WO2017012156A1

WO2017012156A1 - Method for preparing local soft solder coating on surface of aluminum alloy

Info

Publication number: WO2017012156A1
Application number: PCT/CN2015/086518
Authority: WO
Inventors: 李明雨; 杨海峰; 杨世华; 苗峻
Original assignee: 哈尔滨工业大学深圳研究生院; 上海航天设备制造总厂
Priority date: 2015-07-22
Filing date: 2015-08-10
Publication date: 2017-01-26
Also published as: CN105014175B; CN105014175A

Abstract

A method for preparing a local soft solder coating on the surfaces of aluminum and an aluminum alloy in an atmospheric environment under the low-temperature condition. The method achieves preparation of a local soft solder coating on the surface of aluminum or an aluminum alloy in the atmospheric environment under the low-temperature condition by means of the function of ultrasonic phonochemistry. The method overcomes the defect of difficulty in preparation of a soft solder wetting coating on the surface of aluminum or an aluminum alloy. Compared with other coating processes such as electroplating, the method is simple in process, low in manufacturing cost, and pollution-free, and can form a local coating within an extremely short period of time.

Description

Method for preparing local solder coating on aluminum alloy surface

Technical field

The invention belongs to the technical field of materials, and in particular relates to a method for preparing a partial solder coating on an aluminum alloy surface.

Background technique

Aluminum alloy has the advantages of small specific gravity, good heat conduction and high cost performance. In the electronic industry, it mainly plays the role of mechanical support, electrical signal transmission, heat dissipation, electromagnetic field shielding, circuit protection, etc. In recent years, due to the continuous increase in copper prices, some copper components have gradually been replaced by aluminum alloys. From the point of view of the manufacture of electronic products, aluminum alloys are required to have good solderability. Solder solders commonly used in electronic packaging are difficult to wet and spread on aluminum alloys, so the solderability of aluminum alloy members is improved in the electronics manufacturing industry by electroplating tin on the surface of aluminum alloys. The electroplating tin process of aluminum alloy is relatively mature and has been widely used in industries such as electronics manufacturing. Electroplating tin has the following main steps: chemical degreasing - cleaning - acid etching activation - cleaning - nickel immersion - cleaning - pre-plating copper - cleaning - tin plating. In contrast, electroplating on aluminum and aluminum alloys is much more difficult than plating on metals such as steel and copper. The main reasons are as follows:

1. Aluminum is a relatively active metal with a great affinity for oxygen, and it is easy to form a natural oxide film. The presence of an oxide film reduces the binding force to the coating.

2, the electrode potential of aluminum is lower

When immersed in the plating solution, it can undergo a displacement reaction with a plurality of metal ions, and a contact plating layer is formed on the surface of the aluminum to lower the bonding strength between the plating layer and the substrate.

3, aluminum is an amphoteric metal, soluble in acid and alkali, unstable in acidic or alkaline metal plating solution.

4, aluminum alloy castings have sand holes, pores, will leave plating solution and hydrogen, easy to bubble, will also reduce the bonding between the coating and the substrate.

On the other hand, in the electronics manufacturing industry, aluminum alloys need to be interconnected with some circuits and electronic components while being used for mechanical support. Due to the mechanical support, the area of the aluminum alloy member is large, and the area that needs to be interconnected with other devices accounts for only a very small proportion of the entire aluminum alloy member. The electroplating process requires electroplating of the entire aluminum component, increasing the cost of electronics manufacturing and causing waste of energy and raw materials and causing unnecessary pollution to the environment. So far, there is still no viable tin plating process that can achieve local tinning or soldering on the aluminum alloy surface with high efficiency, low cost and no pollution.

Summary of the invention

In view of the technical problems existing in the prior art, it is an object of the present invention to provide a method for preparing a surface partial solder coating of an aluminum or aluminum alloy material. The method can directly form a tin plating layer or a solder coating layer of any area on the surface of the aluminum alloy in an atmospheric environment without damaging the surface morphology of the alloy.

The invention provides a method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment, comprising: forming an ultrasonic coating of an arbitrary area on an aluminum alloy surface in an atmospheric environment by using ultrasonic sonochemistry.

The method first uses a commercially available aluminum alloy oil stain cleaning agent to wipe the position of the surface of the aluminum alloy to be plated to achieve a partial degreasing and decontaminating effect. The method does not need to completely clean, acid etch and remove the mechanical grain on the surface of the aluminum alloy, and only partially removes and degreases the area where the solder plating is needed, thereby reducing the production cost and the environmental pollution caused by the use of the cleaning agent.

The ultrasonic welding head used is a titanium-based alloy or ceramic. The welding head can be divided into two categories: (1) the shape and area of the lower surface of the welding head and the shape and area of the coating to be prepared are the same. This type of welding head is suitable for preparing small-area coatings (coating area less than 0.01m ² ). (2) The lower surface of the welding head is square or rectangular, the edges are chamfered, and the area depends on the plating area. This type of horn is suitable for the preparation of large-area coatings. The chamfering design facilitates the filling of the solder to the horn and the aluminum alloy surface during the movement of the horn. The thickness of the two types of welding heads depends on the characteristics of the ultrasonic generator and the horn, and finally the amplitude of the welding head is required to be 5 to 20 μm.

The method is further preferably carried out in the following steps:

(1) After decontaminating the parts of the aluminum alloy surface that need to be plated, place a solder of 200μm-1mm on the surface and heat it until the solder melts. Preferably, the solder is heated to a temperature of 10 to 50 ° C above the liquidus.

(2) The ultrasonic welding head is placed on the molten solder to maintain a distance of 5 to 500 μm with the surface of the aluminum alloy. Preferably, the surface of the ultrasonic conductive medium and the aluminum alloy surface which are difficult to react with the solder such as a titanium-based alloy or ceramic connected to the ultrasonic horn is 5 to 200 μm and heated to 200 to 300 ° C; the ultrasonic conductive medium may be parallel to the aluminum. The surface of the alloy moves.

(3) Applying ultrasonic waves. A longitudinal or transverse ultrasonic wave having an ultrasonic frequency of 15 to 100 kHz and an amplitude of 1 to 20 μm is preferably used, and the ultrasonic conductive medium is moved at a speed of 0 to 5 s or at a speed of 0 to 5 m/min to cover the entire area where plating is required. Then, air-cooled to room temperature to obtain a partially tinned or tin-based solder on the surface of the aluminum or aluminum alloy. When the process parameters are not in this range, for example, the ultrasonic application time is 2S, the plating preparation effect is deteriorated, and the aluminum alloy surface cannot form a complete plating layer.

The solder is pure tin or tin-based solder, and the tin-based solder is composed of: Sn: 10-100% by weight; Pb: 0-37%; Ag: 0-5%; Cu: 0-5 %; Zn: 0 to 9%; Bi: 0 to 57%; Al: 0 to 14%.

The solder is preferably in the form of a foil, a sphere or a block.

A further preferred embodiment of the method is to remove excess solder using a hot air leveling device after sonication.

Advantageous effects of the present invention over the prior art include:

In the present invention, the plating layer is prepared under an atmospheric environment, and the oxide film removing process is not required, and defects caused by incomplete removal of the aluminum oxide film are avoided. Ultrasonic conductive media such as titanium-based alloys or ceramics are difficult to react with tin-based solders, and do not affect the composition of the plating layer, and are easy to clean and can be used repeatedly. The invention utilizes the action of ultrasonic sonochemistry and the effect of the spatial structure on the ultrasonic conduction and the liquid metal, and forms a tin or solder coating on the aluminum alloy surface locally without using a flux. The plating preparation process is simple, easy to automate, and greatly reduce the production cycle; while saving energy and environmental protection, the production cost is greatly reduced.

DRAWINGS

FIG. 1 is a schematic view showing a process of preparing a partial plating layer on an aluminum alloy surface according to a specific embodiment.

FIG. 2 is a schematic view showing a preparation process of a partial plating layer on the surface of the aluminum alloy according to the second embodiment.

FIG. 3 is a schematic view showing a preparation process of a partial plating layer on the surface of the seven aluminum alloy according to the specific embodiment.

FIG. 4 is a schematic view showing a process of preparing a partial plating layer on the surface of an aluminum alloy according to a specific embodiment.

Figure 5 shows the results of line scan of the EDS (Energy Dispersive Spectroscopy) of tin plating and aluminum alloy interface. The results of line scanning show that tin and aluminum alloy form interdiffusion.

Among them, 1 is a horn (ultrasonic welding head); 2 is a titanium-based alloy or ceramic connected to the horn, such as an ultrasonic conducting medium that does not react with the solder, and the lower end of the conducting medium is chamfered to promote soldering. The material is caulked, and the conductive medium can be moved in parallel with the horn at a certain speed; 3 is a solder ball or a solder ball; 4 is an aluminum alloy.

detailed description

In order to explain the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the invention is not limited thereto.

Embodiment 1

As shown in FIG. 1 , the partial plating of the aluminum or aluminum alloy of the present embodiment is achieved by the following steps: 1. After decontaminating the portion of the aluminum alloy to be plated, a tin foil having an area of 15×15 mm and a thickness of 300 μm is deposited on the surface. 2. A titanium-based alloy ultrasonic conducting medium (lower surface area of 20 x 20 mm) connected to the ultrasonic horn is placed on the tin foil and heated to 250 °C. 3. Apply longitudinal ultrasonic waves with a frequency of 30 kHz and an amplitude of 5 μm. After ultrasonic treatment for 15 s, remove the ultrasonic conductive medium, remove the excess tin with a hot air leveling device, and cool the aluminum alloy to room temperature in air.

The coating was macroscopically examined and the surface of the coating was clean and free of voids. The EDS line scan shows that tin and aluminum alloy form a good metallurgical bond, as shown in Figure 5.

Specific implementation method 2:

As shown in FIG. 2, the partial plating of the aluminum or aluminum alloy of the present embodiment is achieved by the following steps: 1. After decontaminating the portion of the aluminum alloy to be plated, a tin foil having a surface area of 25×25 mm and a thickness of 300 μm is deposited on the surface. 2. Place the ceramic ultrasonic transmission medium (lower surface area of 10×10 mm) connected to the ultrasonic horn on the tin foil and heat to 250 °C. 3. Apply longitudinal ultrasonic wave with a frequency of 30 kHz and an amplitude of 5 μm. After ultrasonic sonication for 10 s, the ultrasonic device is moved in parallel at a speed of 0.05 m/min, so that the ceramic medium covers the entire area to be plated at a slow speed and stays at the final position for 10 s. . The ultrasonically conductive medium is removed, the excess tin is removed using a hot air leveling device and the aluminum alloy is placed in air to cool to room temperature.

Embodiment 3:

This embodiment differs from the first embodiment in that longitudinal ultrasonic waves having a frequency of 20 kHz and an amplitude of 10 μm are applied, and ultrasonic treatment is performed for 8 s. The other steps and parameters are the same as in the first embodiment.

Embodiment 4:

This embodiment differs from the specific embodiment 1 in that Sn-3Ag-0.7Cu solder is used instead of tin, and other steps and parameters are the same as in the first embodiment.

Embodiment 5:

This embodiment differs from the specific embodiment in that Sn is replaced with Sn-9Zn solder, and other steps and parameters are the same as those in the first embodiment.

Embodiment 6:

This embodiment differs from the second embodiment in that Sn-3Ag-0.7Cu solder is used instead of tin. A longitudinal ultrasonic wave having a frequency of 20 kHz and an amplitude of 10 μm was applied, and the moving speed of the ultrasonic device was 0.01 m/min. Other steps and parameters are the same as in the second embodiment.

Specific implementation method seven:

As shown in FIG. 3, the present embodiment differs from the specific embodiment in that tin balls or tin fast are used instead of tin foil, and the effect of ultrasonic caulking is used to achieve the purpose of tin wetting on the surface of the aluminum alloy. The other steps and parameters are the same as in the first embodiment.

Embodiment 8:

As shown in FIG. 4, the present embodiment differs from the second embodiment in that instead of tin foil, a solder ball or tin is used instead of tin foil, and the wetting of tin on the surface of the aluminum alloy is achieved by the action of ultrasonic caulking. Other steps and parameters are the same as in the second embodiment.

Embodiment 9:

This embodiment differs from the seventh embodiment in that a transverse ultrasonic wave having a frequency of 35 kHz and an amplitude of 5 μm is applied, and a gap between the ultrasonic conductive medium and the aluminum alloy surface is 30 μm. The other steps and parameters are the same as in the seventh embodiment.

DETAILED DESCRIPTION OF THE INVENTION

This embodiment differs from the eighth embodiment in that a transverse ultrasonic wave having a frequency of 35 kHz and an amplitude of 5 μm is applied, and a gap between the ultrasonic conductive medium and the aluminum alloy surface is 30 μm. The other steps and parameters are the same as in the eighth embodiment.

Comparative Embodiment 11:

This embodiment differs from the specific embodiment in that the tin foil is heated to 235 ° C and ultrasonic waves are applied. The other steps and parameters are the same as in the first embodiment. Plating effect: Due to the temperature difference between the welding head and the brazing material, the brazing material quickly solidifies after the welding head contacts the brazing material, and the coating on the aluminum alloy surface cannot be formed.

Comparative Embodiment 12:

This embodiment differs from the specific embodiment in that the ultrasonic welding head is placed close to the molten solder. On the surface of the near aluminum alloy, other steps and parameters are the same as in the first embodiment. Plating effect: Due to the strong attenuation effect of the ultrasonic wave in the metal, the plating layer is formed within a range of less than 15 mm from the welding head, and the plating layer cannot be formed beyond the distance of 15 mm.

Comparative Embodiment 13:

This embodiment differs from the specific embodiment in that the ultrasonic application time is 50 s, and the other steps and parameters are the same as those of the specific embodiment 1. Plating effect: Due to the long-term application of ultrasonic waves, the surface of the solder is severely oxidized and the coating is destroyed.

Comparative Embodiment 14:

The difference between the present embodiment and the second embodiment is that the ultrasonic amplitude is 30 μm, and other steps and parameters are the same as those of the specific embodiment 1. Plating effect: Due to the large amplitude of the ultrasonic wave, the solder cannot be filled between the ultrasonic welding head and the surface of the aluminum alloy, and a continuous and complete coating cannot be formed.

It can be seen from the EDS line scan that the specific embodiments 2 to 10 are as in the first embodiment, and the solder forms a good metallurgical bond with the aluminum alloy.

Summary of Effects, it can be seen from the above examples and comparative examples that the preferred embodiment of the present invention is significantly superior to the comparative embodiment, and a continuous, complete plating structure can be formed in a short time.

The above is a further detailed description of the present invention in connection with the specific preferred embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Claims

The invention relates to a method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment, characterized in that an ultrasonic softening effect is used to form an arbitrary area of local solder coating on an aluminum alloy surface in an atmospheric environment.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 1, wherein the surface of the aluminum alloy surface to be coated is first treated to remove oil and decontamination.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 1, characterized in that the method comprises the following steps:

(1) After decontaminating the parts of the aluminum alloy surface that need to be plated, place 100μm-1mm solder on the surface and heat until the solder melts;

(2) placing the ultrasonic welding head on the liquid solder on the surface of the aluminum alloy, maintaining a distance of 5 to 50 μm from the surface of the aluminum alloy, that is, the thickness of the brazing material is maintained at 5 to 50 μm;

(3) Applying ultrasonic waves.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 3, wherein the step (1) is to heat the solder to 20 to 30 ° C above the liquidus.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 3, wherein the step (2) is to harden and solder a titanium-based alloy or ceramic connected to the ultrasonic horn. The surface of the ultrasonically conductive medium reacted with the aluminum alloy is 5 to 50 μm and heated to 200 to 300 ° C; the ultrasonic conductive medium can move parallel to the surface of the aluminum alloy.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 3, wherein the step (3) is a longitudinal or transverse ultrasonic wave having an ultrasonic frequency of 15 to 100 kHz and an amplitude of 1 to 20 μm. The ultrasonically conductive medium is moved by ultrasonication for 3 to 20 s or at a speed of 0 to 5 m/min to cover the entire area where plating is required.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 3, wherein the ultrasonic horn is a titanium-based alloy or a ceramic, and the solder is a foil, a sphere or a block.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 1, wherein the solder is a pure tin or tin-based solder, and the tin-based solder is composed of: Sn: 10 to 100%; Pb: 0 to 37%; Ag: 0 to 5%; Cu: 0 to 5%; Zn: 0 to 9%; Bi: 0 to 57%; and Al: 0 to 14%.
The method for preparing a local solder coating on an aluminum alloy surface in an atmospheric environment according to claim 1, characterized in that after the ultrasonic treatment, the hot solder flattening device is used to remove excess solder.
An aluminum alloy comprising a partial solder coating, characterized in that the aluminum alloy is prepared by the method of any of claims 1-9.