Preparation method and preparation device of copper-core ball brazing filler metal coating

Abstract

The invention provides a preparation method and a preparation device of a copper-core ball brazing filler metal coating, and the preparation method comprises the following steps: S1, melting alloy brazing filler metal to form brazing filler metal melt; s1, the brazing filler metal melt is sprayed to a nickel-plated copper ball in a vibration state, and the surface of the nickel-plated copper ball is plated with a layer of brazing filler metal melt; and S3, gradient cooling is conducted on the nickel-plated copper ball with the surface plated with the brazing filler metal melt, a brazing filler metal coating is formed on the nickel-plated copper ball, and a copper core ball product with the brazing filler metal coating is obtained. According to the method, the spraying process, the nickel-plated copper ball vibration process, the gradient cooling process and the like are mainly combined, the nickel-plated copper ball is plated with the brazing filler metal coating, and compared with a traditional electroplating process, the preparation method has the beneficial effects of being simple, low in cost, small in pollution, short in working time, good in universality and the like. In addition, the preparation device provided by the invention can realize continuous production of the copper-core ball brazing filler metal coating.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic component manufacturing, and in particular to a method and a device for preparing a copper core ball solder coating for 3D packaging. Background Art

[0002] In recent years, electronic products represented by smartphones and tablets have continued to develop in the direction of miniaturization, lightness, slimness and multifunctionality. At the same time, emerging fields such as the Internet of Things, 5G technology, and artificial intelligence have rapidly emerged. 3D advanced packaging technology is in urgent need of its multifunctionality, high density, large capacity and low cost. In high-density 3D packaging technology, multiple chips are stacked, the size and spacing of micro solder joints are small, and the current density carried during service is getting higher and higher. Traditional SnAgCu solder balls will be remelted after repeated heating at 250°C during the welding process, and will be greatly deformed or even collapsed under the weight of electronic components, resulting in adhesion between solder joints and parts, causing short circuits and other problems, which seriously affects the performance of electronic components and becomes one of the main reasons for the failure of integrated circuits.

[0003] The copper core ball generally consists of three parts: a copper ball, a nickel-plated layer, and a solder-plated layer. The diameter of the copper ball is 300 to 700 μm, the nickel-plated layer is generally 2 to 3 μm, and the solder-plated layer is 10 to 30 μm. The copper ball is the core, the nickel layer can prevent the diffusion of copper elements with the metal elements in the solder or substrate, and the solder layer is the effective welding part of the copper core ball. During the welding process, the copper ball is the core, and its melting temperature is 1080°C. After repeated reflow, the shape does not change, which effectively prevents the copper core balls from contacting each other when the size and spacing are very small. The nickel-plated layer can inhibit the rapid growth of brittle IMC, making the bonding at the solder joint interface more reliable.

[0004] Plating is one of the key technologies for the preparation of copper core balls. The most commonly used process is electroplating. However, for alloy solder plating, the plating solution is difficult to prepare. Invention patent application CN 118272883 A discloses a copper core ball solder layer electroplating solution and its preparation method and electroplating process method. The copper core ball solder layer electroplating solution includes methanesulfonic acid, tin salt, silver salt, copper salt, additives and complexing agents. In the tin-silver-copper plating step, the amount of methanesulfonic acid added is detected by titration, and the amount of tin salt, silver salt and copper salt added is detected by AA atomic absorption spectrometer or titration to detect ion concentration; additives and complexing agents are adjusted by Hall cell experiment.

[0005] Although the above patent application obtains a relatively thick ammonia nitrogen SnAgCu alloy solder coating with uniform surface, good dispersion ability and strong covering ability, the preparation of the solder plating solution requires a variety of chemical solutions, strict process control, and a long electroplating time; and currently there is no method for preparing the plating solution related to the quaternary tin-based solder coating. Summary of the invention

[0006] In view of this, the main object of the present invention is to provide a preparation method and a preparation device for a copper core ball solder coating, so as to achieve efficient, low-pollution and uniform preparation of the copper core ball solder coating.

[0007] To achieve the above object, in the first aspect of the present invention, a preparation method for a copper core ball solder coating is provided, including the following steps: S1. Melt the alloy solder to form a solder melt; S2. Spray the solder melt onto the nickel-plated copper balls in a vibrating state, and coat a layer of the solder melt on the surface of the nickel-plated copper balls; S3. Gradiently cool the nickel-plated copper balls with the solder melt coated on the surface obtained in step S2, form a solder coating on the nickel-plated copper balls, and obtain copper core ball products with a solder coating.

[0008] To facilitate continuous preparation of copper core balls, in the second aspect of the present invention, a preparation device for a copper core ball solder coating is provided, including: A graphite groove for melting the alloy solder to form a solder melt, and a solder melt spraying hole is provided at the bottom thereof; A coating processing platform located below the graphite groove for processing and forming a solder coating on the nickel-plated copper balls, which is successively divided into a loading area for placing nickel-plated copper balls, a spraying area for forming a solder coating on the nickel-plated copper balls, and a slow cooling area for stepwise cooling the solder coating, including a steel mesh that circulates and moves from the loading area to the unloading area, a vibration pump and a heating furnace installed in the loading area. The steel mesh is used for placing materials, and under the action of the vibration pump, the materials can vibrate with the vibration of the steel mesh. The steel mesh passes through the heating furnace, and the heating furnace is arranged in the spraying area and the slow cooling area.

[0009] In the third aspect of the present invention, a method for continuously preparing a copper core ball solder coating by using the above preparation device is provided, including the steps: S10. Add the alloy solder into the graphite groove for melting to form a solder melt; S20. Place the nickel-plated copper balls on the steel mesh located in the loading area until they move to the spraying area along with the steel mesh. Maintain the temperature of the spraying area at 150-200 °C. While vibrating the steel mesh, spray the solder melt on the nickel-plated copper balls until a layer of solder melt is coated on the surface of the nickel-plated copper balls; S30. Continuously drive the steel mesh to vibrate, and carry the nickel-plated copper balls with the solder melt coated on the surface formed in step S20 to move in the slow cooling area. The temperature of the slow cooling area starts to drop step by step from 100 °C, form a solder coating on the nickel-plated copper balls, and obtain the copper core ball products.

[0010] In the process of preparing the copper-core ball solder coating by using the above technical solution provided by the present invention, when spraying the solder melt onto the nickel-plated copper balls, the nickel-plated copper balls are vibrated simultaneously, and the nickel-plated copper balls are in a relatively high heating state, so that the solder melt initially sprayed on the nickel-plated copper balls is in a molten state, which is beneficial to the uniform distribution of the solder melt on the nickel-plated copper balls and improves the quality of the solder coating; the solder coating is formed by gradient cooling, so that the components in the solder coating are evenly distributed, and the diffusion of alloy solder elements is reduced, and the generation of interfacial brittle phases is reduced, thereby ensuring the performance of the copper-core ball products formed with the solder coating.

[0011] Therefore, the present invention mainly combines spraying process, vibration of nickel-plated copper balls and gradient cooling process, etc. to realize the plating of solder coating on nickel-plated copper balls. Compared with the traditional electroplating process, this preparation method has the characteristics of simple method, low cost, small pollution, short working time, and the working time can be shortened by 60%, etc.; in addition, this preparation method does not limit the composition and morphology of alloy solder, and has good versatility. In addition, the preparation device provided by the present invention is simple and easy to operate, and can realize the continuous production of copper-core ball solder coating. Brief Description of the Drawings

[0012] Figure 1 It is a schematic diagram of the preparation device for the copper-core ball solder coating provided in Embodiment 1 of the present invention; Figure 2 It is an optical morphology diagram of the copper-core ball prepared for Sample 1 in Embodiment 2 of the present invention (left figure ×25, right figure ×200); Figure 3 It is the microscopic morphology of the copper-core ball solder coating prepared for Sample 2 in Embodiment 2 of the present invention.

[0013] In the above figures: 1 graphite groove, 2 cover plate, 3 air inlet, 4 high-frequency induction welding machine, 5 solder melt spraying hole, 6 baffle, 7 steel mesh, 8 vibration pump, 9 resistance heating furnace, 10 cooling tank, 11 collection container, 70 nickel-plated copper balls, 71 loading area, 72 spraying area, 73 first cooling area, 74 second cooling area, 75 unloading area, 76 copper-core ball products. Detailed Embodiments

[0014] The following further describes the technical solution of the present invention in detail through specific embodiments.

[0015] The terms used in the present invention are all common terms in the art. Without special instructions for the raw materials, equipment, preparation processes, testing methods, etc. used, they are all the existing technologies in the art.

[0016] The present invention mainly combines the spraying process and vibration of nickel-plated copper balls, etc., to coat a layer of molten solder solution on the surface of nickel-plated copper balls at a relatively high temperature; then, gradient cooling is adopted for cooling treatment, so as to obtain a copper core ball product with a uniform solder coating; moreover, the preparation method of the solder coating in the copper core ball has the characteristics of simplicity, high efficiency, low pollution, etc.

[0017] Specifically, the first aspect of the present invention provides a method for preparing a solder coating on a copper core ball, including the following steps: S1. Melt the alloy solder to form a solder solution; S2. Spray the solder solution onto the vibrating nickel-plated copper balls, and coat a layer of the solder solution on the surface of the nickel-plated copper balls; S3. Gradient cool the nickel-plated copper balls with the solder solution coated on the surface obtained in step S2, form a solder coating on the nickel-plated copper balls, and obtain a copper core ball product with a solder coating.

[0018] The step S1 includes: heating the alloy solder to a temperature 100°C - 150°C higher than its melting point, so that the alloy solder is in a molten state to obtain a solder solution. Among them, the heating method is high-frequency induction heating. In this way, under the action of an alternating magnetic field, the atoms inside the alloy solder move randomly and at high speed, generating eddy currents to achieve rapid melting of the alloy solder. Among them, an infrared thermometer is used to measure the temperature of the solder solution, and the temperature of the solder solution is higher than the melting point of the corresponding alloy solder.

[0019] The alloy solder is preferably a tin-based solder, and the solder components and forms are not limited. Preferably, the tin-based solder includes Ag: 3.0 - 4.1 wt%, Cu: 0 - 0.5 wt%, In: 0 - 8 wt%, Bi: 0 - 2.2 wt%, and the balance is Sn. Further, the alloy solder can be a ternary alloy solder, a quaternary alloy solder, a quinary alloy solder or other multi-component alloy solders.

[0020] The step S2 includes: maintaining the temperature of the vibrating nickel-plated copper balls at 150 - 200°C, and spraying the solder solution onto the nickel-plated copper balls at this temperature, so that the solder solution is coated on the surface of the nickel-plated copper balls. Specifically, first place the nickel-plated copper balls on a steel mesh, then heat to 150 - 200°C and perform constant temperature treatment, and at the same time vibrate the steel mesh to make the nickel-plated copper balls rotate on the steel mesh, and at the same time spray the solder solution onto the nickel-plated copper balls to uniformly coat a layer of solder solution on the surface of the nickel-plated copper balls. The diameter of the nickel-plated copper balls is 300 - 800 μm.

[0021] Among them, in step S2, factors such as the spraying speed, spraying time, vibration of nickel-plated copper balls, and temperature of the solder melt act synergistically to ensure that a layer of solder melt is evenly coated on the surface of the nickel-plated copper balls. Specifically, if the spraying speed of the solder melt is too fast or too slow, or the spraying time is too short or too long, it is easy to cause uneven coating and uneven surface quality or excessive surface thickness of the final solder coating. Therefore, preferably, the spraying speed is 5 - 10 m / s, and the spraying time is 30 - 120 s.

[0022] If the vibration frequency of the nickel-plated copper balls is too fast, they are prone to collide with each other, affecting the uniformity of the solder plating solution spraying on the nickel-plated copper balls; if the vibration frequency is too slow, the nickel-plated copper balls are difficult to rotate or the rotation angle is not obvious, making it difficult to achieve uniform coating. Therefore, preferably, the vibration frequency of the steel mesh is 40 - 60 Hz.

[0023] The spraying area temperature is selected to be 150 - 200 °C because it is related to the melting point of the solder coating. If the set temperature is too high, it is difficult to achieve the coating of the solder coating. Therefore, at this temperature, it can ensure that the alloy solder remains in a molten state during the coating process, better realizing the solder coating on the surface of the nickel-plated copper balls.

[0024] The main purpose of using gradient cooling in step S3 is to reduce the influence of the cooling speed on the undercooling degree of the alloy solder and make the solder coating evenly distributed; at the same time, the nickel-plated copper balls also remain in a vibrating state during this process, further promoting the uniformity of the solder coating distribution. The specific setting of the gradient cooling temperature is related to the properties of the alloy solder. Based on the tin-based solder, step S3 includes: continuously vibrating the nickel-plated copper balls with the surface coated with the solder melt, first cooling it to 80 - 100 °C and performing a constant temperature treatment, and then cooling it to 30 - 50 °C and performing a constant temperature treatment to obtain the copper core ball product. Among them, the constant temperature time at 80 - 100 °C is 20 - 30 s, and the constant temperature time at 30 - 50 °C is 20 - 30 s. Too long or too short time will result in uneven surface quality of the solder coating.

[0025] To facilitate industrial and continuous preparation of copper core balls, the second aspect of the present invention provides a preparation device for the solder coating of copper core balls, including: A graphite tank for melting the alloy solder to form a solder melt, and a solder melt spraying hole is provided at its bottom; The coating processing platform is located below the graphite groove and is used to form a solder coating on nickel-plated copper balls. It is sequentially divided into a loading area for placing nickel-plated copper balls, a spraying area for forming a solder coating on the nickel-plated copper balls, and a slow cooling area for stepwise cooling the solder coating. It includes a steel mesh that circulates and moves from the loading area to the unloading area, a vibration pump and a heating furnace installed in the loading area. The steel mesh is used to place materials and, under the action of the vibration pump, the materials can vibrate along with the vibration of the steel mesh. The steel mesh passes through the heating furnace, and the heating furnace is arranged in the spraying area and the slow cooling area.

[0026] The graphite groove is an irregular graphite groove and is used to accommodate alloy solders in various states. A heating component is installed on the graphite groove. The heating component is preferably a high-frequency induction heating component, including a magnetic induction coil wound around the graphite groove and a high-frequency induction welding machine connected to the magnetic induction coil.

[0027] Nitrogen is introduced downward from the top of the graphite groove, and the nitrogen gas flow rate is 1 - 2 m / s; A number of solder melt spraying holes are provided at the bottom of the graphite groove. The diameter of the solder melt spraying holes is 0.9 - 1.1 mm, and the spacing is 0.9 - 1.1 mm. The solder melt spraying holes are regularly arranged at the bottom of the graphite groove.

[0028] A movable spraying hole shielding structure is further provided at the bottom of the graphite groove. The spraying hole shielding structure can cover or expose the solder melt spraying holes. When the spraying hole shielding structure covers the solder melt spraying holes, it can prevent the alloy solder from leaking out from the solder melt spraying holes during the melting process in the graphite groove. When starting to spray the solder melt, the spraying hole shielding structure can be moved away to expose the solder melt spraying holes.

[0029] To minimize the oxidation of the alloy solder to form impurities during the melting process and improve the spraying speed of the molten alloy solder, an air inlet is provided at the upper part of the graphite groove for introducing inert gases such as nitrogen, helium, neon, argon, etc. Additionally, the spraying speed of the solder melt can be controlled by controlling the downward flow rate of the inert gas introduced into the graphite groove 1. Preferably, the flow rate of the inert gas can be controlled to be 1 - 2 m / s.

[0030] The steel mesh is variable-speed. During the spraying process, that is, the steel mesh does not move in the spraying area, and after spraying, it can move towards the slow cooling area at a moving rate of 15 - 25 mm / s.

[0031] The slow cooling area includes a first cooling area connected to the spraying area and a second cooling area adjacent to the unloading area. Among them, the temperature of the first cooling area can be controlled at 80 - 100 °C, and the temperature of the second cooling area can be controlled at 30 - 50 °C.

[0032] The heating furnace is preferably a resistance heating furnace provided on the outer surface of the steel mesh, which can effectively prevent the nickel-plated copper balls from falling off the steel mesh.

[0033] For the convenience of collecting the copper core ball products, the coating processing platform is further divided into a discharging area for unloading the copper core ball products with the solder coating, and a collection container is arranged below the discharging area.

[0034] For the convenience of collecting the materials falling from the steel mesh, cooling tanks are arranged below the loading area, the spraying area and the slow cooling area.

[0035] The third aspect of the present invention provides a method for continuously preparing a copper core ball solder coating by the above preparation device, including the steps: S10. Adding alloy solder into a graphite tank for melting to form a solder melt; S20. Placing nickel-plated copper balls on the steel mesh located in the loading area until they move to the spraying area with the steel mesh, maintaining the temperature of the spraying area at 150 - 200 °C, and while vibrating the steel mesh, spraying the solder melt on the nickel-plated copper balls until a layer of solder melt is plated on the surface of the nickel-plated copper balls; S30. Continuously driving the steel mesh to vibrate and carrying the nickel-plated copper balls with a solder melt plated on the surface formed in step S20 to move in the slow cooling area, the temperature of the slow cooling area gradually decreases starting from 100 °C, and a solder coating is formed on the nickel-plated copper balls to obtain the copper core ball products.

[0036] The vibration frequency of the steel mesh is the same as that of the nickel-plated copper balls. If the steel mesh vibrates too fast, the nickel-plated copper balls are likely to collide with each other and even fall off the steel mesh; if the steel mesh vibrates too slowly, it is difficult to make the nickel-plated copper balls rotate or the rotation of the nickel-plated copper balls is relatively slow. Therefore, the vibration frequency of the steel mesh is preferably 40 - 60 Hz. The moving speed of the steel mesh in the slow cooling area is 15 - 25 mm / s, mainly to obtain a better morphology of the solder coating and high working efficiency. During the process of preparing the copper core ball solder coating by using the above technical solution provided by the present invention, when spraying the solder melt onto the nickel-plated copper balls, the steel mesh is vibrated simultaneously to make the nickel-plated copper balls vibrate, and the nickel-plated copper balls are in a relatively high heating state, so that the solder melt just sprayed onto the nickel-plated copper balls is in a molten state, which is beneficial to the uniform distribution of the solder melt on the nickel-plated copper balls and improves the quality of the solder coating; the solder coating is formed by gradient cooling, so that the components in the solder coating are evenly distributed, and the diffusion of alloy solder elements is reduced, and the generation of interfacial brittle phases is reduced, thereby ensuring the performance of the copper core ball products formed with the solder coating.

[0037] Further, step S30 further includes moving the copper core balls with a solder coating to the discharging area, performing grinding, cleaning and drying treatments, and loading them into a collection container.

[0038] To ensure the surface uniformity of the copper core balls, the steel mesh needs to vibrate in both the spraying area and the slow cooling area.

[0039] Furthermore, the method for preparing the solder coating on the copper core balls further includes performing quality inspection on the solder coating in the copper core balls. Those with qualified quality are packaged as finished products, and those unqualified are recycled.

[0040] Furthermore, during the process of vibrating the steel mesh in step S20, materials such as copper-nickel-copper ball raw materials, nickel-plated copper balls with a solder melt solution coated on the surface, and copper core ball products that fall from the steel mesh fall into the cooling tank, are filtered, dried, screened in the cooling tank, and then conveyed to the steel mesh through a conveying device for repeated spraying.

[0041] Step S30 includes: continuously driving the steel mesh to vibrate and move to the slow cooling area, while keeping the nickel-plated copper balls with the solder melt solution coated on the surface in a vibrating state. First, move in the first cooling area of the slow cooling area for 20 - 30 s, and then move in its second cooling area for 20 - 30 s to obtain the copper core ball products; wherein, the temperature of the first cooling area is 80°C - 100°C, and the temperature of the second cooling area is 30°C - 50°C.

[0042] Therefore, the present invention mainly combines the spraying process, the vibration method, and the gradient cooling process to achieve the coating of the solder coating on the nickel-plated copper balls. This preparation method has the advantages of not restricting the composition and form of the alloy solder, good versatility, low cost, small pollution, simple operation, short process time. Compared with the traditional electroplating process, the working time can be shortened by 60% and so on. In addition, the preparation device provided by the present invention is simple and easy to operate.

[0043] The following further illustrates the technical solution protected by the present invention with specific embodiments.

[0044] Example 1 The embodiment of the present invention provides a preparation device for a solder coating on a copper core ball, including: a graphite tank 1 for melting an alloy solder and a coating processing platform located below the graphite tank 1.

[0045] The graphite tank 1 is an irregular graphite tank for accommodating alloy solders in various states. The tank body of the graphite tank 1 is mainly composed of a large tank body with a larger diameter located in the upper part and a small tank body with a smaller diameter located in the lower part, and the two tank bodies are coaxially arranged. A magnetic induction coil is wound around the outer surface of the large tank body, and this magnetic induction coil is connected to a high-frequency induction welder 4. An infrared thermometer is installed inside the large tank body for monitoring the temperature of the materials in the graphite tank during the heating and melting process.

[0046] A cover plate 2 is provided at the top of the large trough body, which is used to cover the graphite trough 1 during the process of heating and melting the alloy brazing filler metal. An air inlet 3 is provided on the cover plate 2. During the process of heating and melting the brazing filler metal, nitrogen gas is introduced downward into the graphite trough 1 from the air inlet 3 and cooperates with the cover plate 2 to minimize impurities in the alloy brazing filler metal during the melting process. A number of brazing filler metal melt spraying holes 5 are provided at the bottom of the small trough body. The diameter of the brazing filler metal melt spraying holes is 1 mm, and the spacing is 1 mm. They are regularly arranged at the bottom of the graphite trough 1, and the spraying speed of the brazing filler metal melt can be controlled by the flow rate of the nitrogen gas introduced into the graphite trough 1.

[0047] A baffle 6 for covering the brazing filler metal melt spraying holes 5 is further provided at the bottom of the small trough body to prevent the alloy brazing filler metal from leaking out from the brazing filler metal melt spraying holes 5 during the melting process in the graphite trough. When starting to spray the brazing filler metal melt, only need to remove the baffle 6.

[0048] The coating processing platform is mainly used to process a brazing filler metal coating on the nickel-plated copper ball 70 to obtain the copper core ball product 76. The coating processing platform is sequentially divided into a loading area 71 for placing the nickel-plated copper ball 70, a spraying area 72 for forming a brazing filler metal coating on the nickel-plated copper ball 70, a slow cooling area for stepwise cooling the brazing filler metal coating, and a unloading area 75 for unloading the copper core ball product 76. The slow cooling area includes a first cooling area 73 connected to the spraying area 72 and a second cooling area 74 adjacent to the unloading area 75.

[0049] The coating processing platform includes a steel mesh 7, a vibration pump 8 installed in the loading area 71, and resistance heating furnaces 9 installed in the spraying area 72, the first cooling area 73, and the second cooling area 74. The steel mesh 7 serves as the main carrier for processing the nickel-plated copper ball 70 and is used to place materials such as the nickel-plated copper ball 70, the nickel-plated copper ball coated with the brazing filler metal melt, and the copper core ball 76. The steel mesh 7 is variable-speed during the process of circulating from the loading area 71 to the unloading area 75. It can stop moving after moving to the spraying area 72 until a layer of brazing filler metal melt is sprayed on the surface of all the nickel-plated copper balls 70 in this area, and then move to the unloading area 75 through the slow cooling area 74. Among them, the moving speed of the steel mesh 7 can be 15 - 25 mm / s. The steel mesh 7 passes through the resistance heating furnace 9. The vibration pump 8 can drive the steel mesh 7 to vibrate with the materials carried on it.

[0050] A collection container 11 is provided below the unloading area 75 to facilitate the collection of the copper core ball product 76.

[0051] A cooling tank 10 is provided below the loading area 71, the spraying area 72, the first cooling area 73, and the second cooling area 74 to facilitate the collection of the materials falling from the steel mesh 7.

[0052] The following examples use the preparation device for the copper-core spherical solder coating provided in this example to prepare the copper-core spherical solder coating.

[0053] Example 2 A method for preparing a copper-core spherical solder coating proposed in an embodiment of the present invention, the specific preparation method includes the following steps: S1: First, close the solder melt spraying hole 5 at the bottom of the graphite tank 1 with a baffle 6, and then heat the Sn3.0AgCu ternary alloy solder in the graphite tank 1 to 350 °C to form a molten state to obtain a solder melt; wherein, during the heating and melting process, nitrogen is introduced from the top of the graphite tank 1 container downward, and the nitrogen gas flow rate is 1 m / s; S2: Place the nickel-plated copper ball 70 with a diameter of 300 μm on the steel mesh 7 at the loading area 71, and drive the steel mesh 7 to carry the nickel-plated copper ball 70 to move horizontally to the spraying area 72; start the resistance heating furnace 9, and heat the nickel-plated copper ball 70 located in the spraying area to the temperature shown in Table 1 below and keep it constant; then start the vibration pump 8 to vibrate the steel mesh at the frequency shown in Table 1 below, and at the same time remove the baffle 6, and the solder melt is evenly sprayed on the nickel-plated copper ball 70 placed in the spraying area under the action of pressure through the solder melt spraying hole 5, and the spraying time is shown in Table 1 below; S3: After the spraying is completed, move the nickel-plated copper ball sprayed with the solder melt horizontally to the first cooling area 73 and the second cooling area 74 through the steel mesh 7 with a moving speed of 20 mm / s in sequence, so that the solder coating is evenly cooled to obtain a solder coating; wherein, the process parameters of the first cooling area 73 and the second cooling area 74 and the thickness of the solder coating are shown in Table 1 below; S4: Move the copper-core ball 76 of the solder coating prepared in step S3 horizontally through the copper mesh 7 to the unloading area 75, and perform grinding, cleaning, and drying treatments, and then load them into the collection container 11; S5: Detect the quality of the solder coating in the copper-core balls prepared in step S4, and those with qualified quality are packaged as finished products, and those with unqualified quality are recycled; S6: During the vibration of the copper mesh 7, the nickel-plated copper balls falling from each area where the steel mesh is located fall into the cooling tank 10, are filtered from the cooling tank, dried, and then conveyed to the steel mesh through the conveying device.

[0054] Table 1 Process parameters for preparing the ternary alloy solder coating

[0055] Example 3 This example provides a method for preparing a copper-core spherical solder coating. This preparation method is basically the same as the preparation method provided in Sample 1 of Example 2, and the main difference is: Step S1: Using Sn3.5AgBi4In quaternary alloy solder as raw material, the temperature of the solder melt is 340 °C, and the nitrogen gas flow rate is 2 m / s; Step S2: The diameter of the nickel-plated copper ball is 800 μm, the spraying time is 100 s, and the constant temperature in the spraying area is 150 °C; Step S3: The first cooling zone is kept at a constant temperature of 70 °C for 30 s, the second cooling zone is kept at a constant temperature of 30 °C for 20 s, the moving speed of the steel mesh is 20 mm / s, and the thickness of the solder coating is 20 μm; The remaining method steps are the same as those of Sample 1 in Example 2, and a copper core ball Q10 with a solder coating is obtained.

[0056] Example 4 This example provides a method for preparing a solder coating on a copper core ball. This preparation method is basically the same as the preparation method provided by Sample 1 in Example 2. The main differences are as follows: Step S1: Using SnAgBiCuIn quinary alloy solder as raw material, the temperature of the solder melt is 300 °C, and the nitrogen gas flow rate is 1.5 m / s; Step S2: The diameter of the nickel-plated copper ball is 600 μm, the spraying time is 120 s, and the constant temperature in the spraying area is 150 °C; Step S3: The first cooling zone is kept at a constant temperature of 80 °C for 30 s, the second cooling zone is kept at a constant temperature of 50 °C for 20 s, the moving speed of the steel mesh is 20 mm / s, and the thickness of the solder coating is 30 μm; The remaining method steps are the same as those of Sample 1 in Example 2, and a copper core ball Q11 with a solder coating is obtained.

[0057] Comparative Example 1: Provide a copper core ball DQ1 with a coating thickness the same as that of Sample 1 in Example 2. The main difference is that this comparative example is obtained by electroplating.

[0058] Test the thickness and performance of the solder coating on the copper core ball samples provided in each example and comparative example. The specific test methods are as follows: 1) Thickness measurement: Use an X-ray fluorescence film thickness gauge to measure the thickness of the solder coating. Take 6 points on each ball for detection, calculate the average value, and calculate the standard deviation. The results are shown in Table 2 below; 2) Welding effect measurement: Use a dynamic mechanical analyzer to conduct a tensile test. The test temperature is set at room temperature, the loading rate is set at 0.1 N / min, and each solder joint tensile test is conducted 3 times. Calculate the average value. The results are shown in Table 2 below.

[0059] Table 2 Test on the thickness and performance of the solder coating of the copper core ball sample The first point The second point The third point The fourth point The fifth point The sixth point Standard deviation Average tensile strength / Mpa Q1 10.10 9.90 10.01 10.00 10.00 9.98 0.02422 42.74 Q 2 10.20 9.60 9.60 9.70 10.00 9.70 0.25820 41.47 Q 3 9.80 10.20 10.50 10.20 10.60 10.50 0.27080 41.45 Q 4 9.80 10.50 10.60 10.80 10.40 10.30 0.34059 40.75 Q 5 9.50 10.00 9.60 9.20 9.20 9.50 0.29665 41.43 Q 7 10.00 10.20 10.10 10.00 10.20 10.10 0.08944 42.01 Q 8 10.40 10.50 10.70 10.80 10.60 10.60 0.14142 41.89 Q 9 11.70 11.10 11.50 11.20 10.50 11.20 0.40988 40.69 Q 10 9.90 10.10 9.90 10.10 9.80 10.10 0.13292 41.93 Q 11 10.01 10.05 9.90 10.10 10.20 9.90 0.11690 41.87 DQ 1 10.01 10.00 9.97 9.98 10.02 10.04 0.02582 42.3

[0060] As can be seen from Table 1 and Table 2, the standard deviations of samples Q2-5 and Q9 are the largest. Therefore, when the spraying time of the solder melt is too long or too short, problems such as uneven plating and uneven appearance quality or too thick surface layer of the coating will occur, resulting in a decrease in the tensile strength of the welding and a change in the welding effect.

[0061] To prevent uneven surface quality during the solder spraying process, the spraying area ensures that the solder remains in a molten state during the plating process, better realizing the plating of the solder on the surface of the nickel-plated copper ball. Considering that the cooling rate has little effect on the undercooling degree of SAC305 solder, a gradient slow cooling interval is set, which can effectively ensure the morphology of the solder coating.

[0062] Among them, from Figure 2 the optical morphology of the copper core ball of Sample 1 in Embodiment 2 shown in the figure, it can be seen that the average thickness of the solder coating is 10 μm.

[0063] From Figure 3 the microscopic morphology diagram of the solder coating in the copper core ball of Sample 1 in Embodiment 2 shown in the figure, it can be seen that the prepared solder coating mainly consists of Sn, Ag, and Cu and is evenly distributed.

[0064] Therefore, the solder coating prepared by the method and device provided in the embodiments of the present invention has the following advantages: 1) It has the advantages of not restricting the solder components, morphology, low cost, small pollution, simple operation, short time, and a 60% reduction in time compared to the electroplating process; 2) By using high-frequency induction heating, under the action of an alternating magnetic field, the atoms inside the solder move randomly at high speed, generating eddy currents to achieve rapid melting of the solder; and by means of thermal spraying, the vibration frequency of the steel mesh, and gradient cooling, the best solder coating is prepared; 3) Three temperature intervals are set. The spraying area ensures that the solder remains in a molten state during the plating process, better realizing the plating of the solder on the surface of the nickel-plated copper ball. Considering that the cooling rate has little effect on the undercooling degree of SAC305 solder, a gradient slow cooling interval is set, which can effectively ensure the morphology of the solder coating; 4) The heating temperature is adjusted in real time by using the infrared temperature measurement method to ensure the optimal fluidity of the alloy solder melt, and it can be melted in a nitrogen atmosphere to reduce impurities in the solder and obtain a clean solder solution; 5) By setting small holes at the bottom of the container graphite groove to form spraying holes, the solder melt can be sprayed efficiently and evenly; 6) An external vibration pump can effectively control the uniform distribution of the nickel-plated copper balls on the steel mesh and improve the quality of the solder coating through vibration; 7) By means of gradient cooling, an evenly composed coating is obtained, and the diffusion of solder elements is reduced, and the generation of brittle phases at the interface is reduced.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing a copper core ball solder coating, comprising the following steps: S1. Melt the alloy solder to form a solder melt; S2. Spray the solder melt onto the nickel-plated copper balls in a vibrating state, and coat a layer of the solder melt on the surface of the nickel-plated copper balls; S3. Gradually cool the nickel-plated copper balls with the solder melt coated on the surface obtained in step S2, form a solder coating on the nickel-plated copper balls, and obtain copper core ball products with solder coatings.

2. The preparation method according to claim 1, wherein Step S2 includes: maintaining the temperature of the vibrating nickel-plated copper balls at 150-200 °C, and spraying the solder melt onto the nickel-plated copper balls at this temperature, so that the solder melt is coated on the surface of the nickel-plated copper balls.

3. The preparation method according to claim 1 or 2, characterized in that, Step S3 includes: continuously vibrating the nickel-plated copper balls with the solder melt coated on the surface, first cooling them to 80-100 °C and performing a constant temperature treatment, and then cooling them to 30-50 °C and performing a constant temperature treatment, to obtain the copper core ball products.

4. A device for preparing a copper core ball solder coating, comprising: A graphite tank for melting the alloy solder to form a solder melt, with a solder melt spraying hole provided at the bottom, and an air inlet provided at the upper part of the graphite tank for introducing an inert gas; A coating processing platform located below the graphite tank for processing and forming a solder coating on the nickel-plated copper balls, which is sequentially divided into a loading area for placing nickel-plated copper balls, a spraying area for forming a solder coating on the nickel-plated copper balls, and a slow cooling area for stepwise cooling the solder coating, including a steel mesh that circulates and moves from the loading area to the unloading area, a vibration pump and a heating furnace installed in the loading area, the steel mesh for placing materials, and under the action of the vibration pump, the materials can vibrate with the vibration of the steel mesh, the steel mesh passes through the heating furnace, and the heating furnace is arranged in the spraying area and the slow cooling area.

5. The preparation device according to claim 4, characterized in that, A movable spraying hole shielding structure is further provided at the bottom of the graphite tank, and the spraying hole shielding structure can cover or expose the solder melt spraying hole.

6. The preparation device according to claim 4 or 5, characterized in that, The coating processing platform is further divided into an unloading area for unloading the copper core ball products with the solder coating, and a collection container is provided below the unloading area.

7. According to the preparation device described in claim 4 or 5, cooling tanks are provided below the loading area, the spraying area and the slow cooling area.

8. A method for continuously preparing a copper core ball solder coating by using the preparation device described in any one of claims 4-7, comprising the steps: S10. Add the alloy solder into the graphite tank for melting to form a solder melt; S20. Place the nickel-plated copper balls on the steel mesh located in the loading area until they move to the spraying area with the steel mesh, maintain the temperature of the spraying area at 150-200 °C, and while vibrating the steel mesh, spray the solder melt onto the nickel-plated copper balls until a layer of solder melt is coated on the surface of the nickel-plated copper balls; S30. Continuously drive the steel mesh to vibrate, and carry the nickel-plated copper balls with the solder melt coated on the surface formed in step S20 to move in the slow cooling area, and the temperature of the slow cooling area gradually decreases starting from 100 °C, form a solder coating on the nickel-plated copper balls, and obtain the copper core ball products.

9. The preparation method according to claim 8, characterized in that, In the step S20, the vibration frequency of the steel mesh is 40 to 60 Hz, the spraying speed of the solder melt is 5 to 10 m / s, and the spraying time is 30 to 120 s.

10. The preparation method according to claim 9, characterized in that, The step S30 includes: continuously driving the steel mesh to vibrate and move to the slow cooling zone, while making the nickel-plated copper balls with the surface coated with the solder melt in a vibrating state, first moving in the first cooling zone of the slow cooling zone for 20 to 30 s, and then moving in its second cooling zone for 20 to 30 s, then the copper core ball product can be obtained; wherein, the temperature of the first cooling zone is 80°C to 100°C, and the temperature of the second cooling zone is 30°C to 50°C.

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