Preparation method of tin-nickel alloy circulating plating layer suitable for long-service-life thermoelectric refrigerating unit

Abstract

The invention belongs to the field of thermoelectric materials, and particularly relates to a preparation method of a tin-nickel alloy circulating coating suitable for a long-service-life thermoelectric refrigerating unit, an activated thermoelectric refrigerating material wafer is circularly subjected to tin-nickel alloy electroplating and chemical nickel liquid plating, and finally a tin coating is electroplated, so that compared with a pure nickel layer, the formed circulating coating has the advantages that the service life of the circulating coating is prolonged; a more stable plating layer with a proper thickness can be formed, meanwhile, a more stable tin-based alloy plating layer is used as a barrier layer, the element diffusion difficulty is increased, element diffusion is more effectively prevented, and therefore the service life of the thermoelectric refrigerating unit is greatly prolonged, and the reliability is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of thermoelectric materials, and in particular relates to a method for preparing a cyclic plating layer of a tin-nickel alloy suitable for a long-life thermoelectric refrigerator. Background Art

[0002] In the field of thermoelectric technology, improving the working efficiency of equipment and extending its service life have always been the focus of research. Thermoelectric coolers use the Peltier effect to achieve heat transfer, thereby achieving the purpose of cooling or heating. Due to their small size and noiselessness, they have unique advantages in the field of refrigeration and heat dissipation. However, in practical applications, thermoelectric coolers often face problems such as a wide operating temperature range and a complex and changeable working environment. These problems place extremely high demands on the durability and stability of materials. However, during the use of commercial thermoelectric coolers, the copper element as an electrode and the tin element of the solder as a solder will diffuse across the barrier layer into the thermoelectric material, resulting in loss of thermoelectric performance and product failure; at the same time, the Te element of the thermoelectric material will also react with the Ni layer of the barrier layer under high temperature or time catalysis to generate NiTe. This will also accelerate product failure.

[0003] In this context, the development of new, efficient, stable and long-life thermoelectric materials has become the focus of scientific researchers. Tin-nickel alloy is considered to be a potential high-performance thermoelectric material due to its good electrical conductivity, thermal conductivity and relatively low cost. However, pure metals or alloys are prone to diffusion at high temperatures, resulting in a decrease in thermoelectric performance, so it is necessary to prepare a coating that can effectively block the diffusion of elements, such as patent CN107737921B. Nickel-tin alloy can form Ni3Sn4, Ni3Sn2, Ni3Sn, among which Ni3Sn4 is the most stable, but it is difficult to control the proportion of nickel-tin alloy by electroplating. Summary of the invention

[0004] In order to solve the problems mentioned in the background technology that the copper element as the electrode and the solder as the solder will diffuse into the internal thermoelectric material and cause the loss of thermoelectric performance, and at the same time it is difficult to control the proportion of tin-nickel alloy to the most stable Ni3Sn4 by electroplating, therefore, the present invention provides a preparation method of a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric refrigerator, by cyclically electroplating a tin-nickel layer and a chemically plated nickel layer, and finally electroplating a tin layer, which increases the difficulty of element diffusion and more effectively prevents the diffusion of elements, thereby greatly extending the life reliability of the thermoelectric refrigerator.

[0005] The technical solution provided by the present invention is a method for preparing a cyclic plating layer of a tin-nickel alloy suitable for a long-life thermoelectric cooler, and the specific steps are: 1) activating the cut and roughened thermoelectric refrigeration material wafer to obtain an activated thermoelectric refrigeration material wafer; 2) electroplating a tin-nickel alloy on the surface of the activated thermoelectric refrigeration material obtained in step 1) to obtain an electroplated tin-nickel layer on the surface of the activated thermoelectric refrigeration material; 3) performing chemical nickel plating on the surface of the electroplated tin-nickel layer obtained in step 2) to obtain a chemical nickel plating layer on the surface of the electroplated tin-nickel layer; 4) Repeat steps 2) and 3) 5) Tin plating is performed on the chemically plated nickel layer finally obtained in step 4) to obtain a nickel-tin alloy cyclic plating layer.

[0006] The cyclic coating provided by the present invention utilizes a more stable nickel-based alloy coating as a barrier layer, which has the advantage of being more stable than pure nickel and can effectively prevent the barrier layer from failing due to the reaction between nickel and thermoelectric materials. At the same time, chemical nickel plating is more dense and can more effectively prevent the copper element used as an electrode and the tin element used as a solder from diffusing into the thermoelectric material. The nickel-based alloy is prepared by electroplating, and a cyclic preparation is required to avoid the difficulty in depositing the coating caused by excessive internal stress, so that a suitable coating thickness can be achieved. At the same time, due to the cyclic coating structure, the difficulty of element diffusion is increased, and the diffusion of elements is more effectively prevented, thereby significantly extending the service life and reliability of the thermoelectric cooler. Furthermore, the reagent used for activation treatment in step 1) is hydrochloric acid.

[0007] Furthermore, the concentration of hydrochloric acid is 5 to 25 vol%.

[0008] Further, in step 2), the electroplating solution includes 50-55 g / L nickel sulfate, 250-275 g / L nickel chloride, 30-40 g / L stannous chloride, 40-50 g / L ammonium chloride, 15-25 ml / L concentrated hydrochloric acid, 30-40 g / L sodium fluoride, and 20-30 g / L boric acid; the pH of the electroplating is 2-2.5.

[0009] When the pH of the plating solution is lower than 2, that is, the pH is too low, a large amount of hydrogen will be precipitated on the cathode, resulting in a decrease in current efficiency, or even making the current efficiency zero. When the pH value exceeds 2.5, nickel hydroxide precipitate will appear and be mixed in the coating, causing the coating to fall off, become brittle, and even difficult to deposit in deep holes.

[0010] Furthermore, the pH of the electroplating was adjusted by ammonia water.

[0011] Furthermore, the electroplating parameters are: the electroplating temperature is 60-70°C; the electroplating current density is 1-1.5A / dm 2 ; The electroplating time is 8 to 15 minutes.

[0012] Further, in step 3), the chemical nickel plating solution includes 15-25 g / L sodium hypophosphite, 150-180 g / L nickel chloride, 10-20 g / L sodium tartrate, and 20-30 g / L ammonium chloride; the temperature of the chemical nickel plating is 85-90°C; and the pH of the chemical nickel plating is 4.5-5.

[0013] When the pH of the chemical nickel plating solution is too low, that is, the pH is lower than 4.5, it will make it difficult to form an chemical plating layer due to excessive acidity. When the pH is too high, the plating layer caused by impurities doped in the chemical plating layer will be easy to peel off, resulting in a shortened life of the final cyclic plating layer.

[0014] Furthermore, the reagent used to adjust pH during chemical nickel plating is ammonia water.

[0015] Furthermore, the number of repetitions in step 4) is 0 times or more.

[0016] Furthermore, the thermoelectric material is a thermoelectric material with N / P type bismuth telluride as the main body, and the surface of the thermoelectric material is chemically etched.

[0017] The beneficial effects of the present invention are: 1. Using a more stable nickel-based alloy coating as a barrier layer is more stable than pure nickel and can effectively prevent the failure of the barrier layer caused by the reaction between nickel and thermoelectric materials.

[0018] 2. Chemical nickel plating is more dense and can more effectively prevent the copper element used as the electrode and the tin element of the solder from diffusing into the thermoelectric material.

[0019] 3. Adding an electroplated tin-nickel layer and a chemically plated nickel layer in the middle of the electroplated tin layer can ignore the internal stress, deposit a thicker coating, and achieve a suitable coating thickness.

[0020] 4. The cyclic coating structure increases the difficulty of element diffusion and more effectively prevents the diffusion of elements, thereby greatly extending the life and reliability of the thermoelectric cooler. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the cyclic plating layer obtained in Example 1. DETAILED DESCRIPTION

[0022] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0023] Example 1 (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0024] (2) Electroplating Preparation of electroplating solution: weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0025] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0026] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 3 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0027] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0028] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that the comparative example does not have step (3) in the example, and the rest of the process is the same as that in the example. The specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the thermoelectric refrigeration material to be plated.

[0030] (2) Preparation of electroplating plating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain a plating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0031] (3) Cyclic plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step 2 is subjected to step (2) again and repeated 6 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0032] (4) Tin plating Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the thermoelectric cooling material after the N-type bismuth telluride cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , and the final N-type bismuth telluride thermoelectric refrigeration material is obtained.

[0033] (5) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (4), and a corresponding life test is performed.

[0034] Comparative Example 2 The difference between this comparative example and Example 1 is that step (2) in the comparative example is omitted in this comparative example, and the rest of the process is the same as that in Example 1, and the specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0035] (2) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the N-type bismuth telluride thermoelectric refrigeration material to be plated obtained in step (1) into the chemical nickel plating solution, react for 6 minutes, and remove them to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0036] (3) Cyclic plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (2) is subjected to step (2) again and repeated 6 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0037] (4) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (3) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0038] (5) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (4), and a corresponding life test is performed.

[0039] Table 1 Comparison of coating thickness of Example 1 and Comparative Examples 1-2 Electroplating tin-nickel times / times Chemical nickel plating times / times Total thickness of the coating cycle Example 1 3 3 10 Comparative Example 1 0 6 4 Comparative Example 2 6 0 3 According to the data in Table 1, we can observe that when only the electroplated tin-nickel layer or only the chemically plated nickel layer is cycled, the total thickness of the cycled coating is much lower than the coating thickness of the electroplated tin-nickel layer and the chemically plated nickel layer in alternating cycles. The reason is speculated to be that the present invention avoids the difficulty in depositing the coating caused by excessive internal stress through cyclic preparation, so that a suitable coating thickness can be achieved. At the same time, due to the cyclic coating structure, the difficulty of element diffusion is increased, and the diffusion of elements is more effectively prevented, thereby extending the service life of the prepared thermoelectric refrigeration material.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (2), the current density during electroplating is 0.5 A / dm 2 The rest of the process is the same as in Example 1, and the specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0041] (2) Preparation of electroplating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 0.5 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0042] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0043] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 3 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0044] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0045] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0046] Comparative Example 4 The difference between this comparative example and Example 1 is that in step (2), the current density during electroplating is 3A / dm 2The rest of the process is the same as in Example 1, and the specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0047] (2) Preparation of electroplating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 4.0 with aqueous ammonia to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) is placed in the above-prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating is 3A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0048] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0049] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 3 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0050] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0051] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0052] Table 2 Effect of current density during electroplating on the life of the final cyclically plated thermoelectric refrigeration material <![CDATA[Current density A / dm during electroplating 2 > Coating thickness Example 1 1.2 10 Comparative Example 3 0.5 5 Comparative Example 4 3 12(with burrs) From the data in the above table, we can observe that when the current density during electroplating is too high or too low, the thickness of the coating obtained after cyclic plating decreases, thereby reducing the life of the thermal conductive electric refrigeration material. The reasons are speculated to be: when the current density during electroplating is too low, the deposition efficiency of electroplating is reduced, resulting in poor quality of the final coating; when the current density during electroplating is too high, pinholes and burrs will appear in the coating.

[0053] Comparative Example 5 The difference between this comparative example and Example 1 is that in step (3), the temperature of the chemical nickel plating solution is raised to 60° C., and the rest of the process is the same as that of Example 1. The specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0054] (2) Preparation of electroplating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0055] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 2.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 60° C., put the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0056] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 3 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0057] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0058] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0059] Comparative Example 6 The difference between this comparative example and Example 1 is that in step (3), the chemical nickel plating solution is heated to 90° C., and the rest of the process is the same as that of Example 1. The specific steps are as follows: (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0060] (2) Preparation of electroplating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0061] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH to 7, thereby obtaining a chemical nickel plating solution; The chemical nickel plating solution obtained above is heated to 100° C., and the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) is placed in the chemical nickel plating solution, reacted for 6 minutes, and then taken out to obtain the chemical nickel-plated N-type bismuth telluride thermoelectric refrigeration material.

[0062] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 3 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0063] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0064] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0065] Table 3 Effect of the temperature of the chemical nickel plating solution on the life of the final cyclic coating thermoelectric refrigeration material Chemical nickel plating solution temperature / ℃ Coating thickness / μm Example 1 89 10 Comparative Example 5 60 5 Comparative Example 6 100 8 From the data in the above table, we can observe that when the temperature of the chemical nickel plating solution is too high or too low, the thickness of the coating obtained after the cyclic plating is shortened, resulting in a shortened life of the thermoelectric cooling material. The reasons are speculated to be: when the temperature of the chemical nickel plating solution is too low, the reaction rate will be reduced, resulting in difficulties in forming the chemical plating layer; when the temperature is too high, the pH of the chemical nickel plating solution changes too quickly, resulting in poor quality of the chemical nickel plating layer.

[0066] Example 2 (1) Pretreatment The p-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the p-type bismuth telluride thermoelectric refrigeration material to be plated.

[0067] (2) Preparation of electroplating plating solution: Weigh 50 g / L nickel sulfate, 250 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, and 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain a plating solution; The p-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the above-prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the p-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0068] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the electroplated p-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the p-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0069] (4) Tin plating Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the p-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (3) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , and obtain the final p-type bismuth telluride thermoelectric refrigeration material.

[0070] (5) Testing A thermoelectric cooler device is manufactured using the p-type bismuth telluride thermoelectric cooler material prepared in step (4), and a corresponding life test is performed.

[0071] Example 3 (1) Pretreatment The N-type bismuth telluride thermoelectric refrigeration material wafer is cut and roughened, and then immersed in 20 vol% hydrochloric acid for activation to obtain the N-type bismuth telluride thermoelectric refrigeration material to be plated.

[0072] (2) Electroplating Preparation of electroplating solution: weigh 45 g / L nickel sulfate, 260 g / L nickel chloride, 30 g / L stannous chloride, 45 g / L ammonium chloride, 20 ml / L concentrated hydrochloric acid, 30 g / L sodium fluoride, 20 g / L boric acid, and make up the rest with distilled water. After fully dissolving, adjust the pH of the solution to 2.2 with ammonia water to obtain an electroplating solution; The N-type bismuth telluride thermoelectric refrigeration material with a coating obtained in step (1) was placed in the prepared electroplating solution and reacted at 67°C for 9 minutes. The current density during electroplating was 1.2 A / dm 2 , and obtain the N-type bismuth telluride thermoelectric refrigeration material after electroplating.

[0073] (3) Chemical nickel plating Preparation of chemical nickel plating solution: weigh 20 g / L sodium hypophosphite, 150 g / L nickel chloride, 15 g / L sodium tartrate, and 25 g / L ammonium chloride, dissolve them in distilled water, and after they are completely dissolved, add ammonia water to adjust the pH so that the pH is 4.5 to obtain a chemical nickel plating solution; heat the chemical nickel plating solution obtained above to 89° C., put the electroplated N-type bismuth telluride thermoelectric refrigeration material obtained in step (2) into the chemical nickel plating solution, react for 6 minutes, and remove it to obtain the N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating.

[0074] (4) Circular plating The N-type bismuth telluride thermoelectric refrigeration material after chemical nickel plating obtained in step (3) is subjected to steps (2) and (3) again, and the steps are repeated 5 times to obtain the N-type bismuth telluride thermoelectric refrigeration material after cyclic plating.

[0075] (5) Tin plating: Tin plating solution: 50 g / L stannous sulfate and 2 g / L sulfuric acid, dissolved in distilled water; the N-type bismuth telluride thermoelectric refrigeration material after the cyclic plating in step (4) is placed in the tin plating solution and reacted at 67°C for 10 min with a current density of 1.2 A / dm 2 , the final N-type bismuth telluride thermoelectric refrigeration material is obtained, and the obtained coating is as follows Figure 1 shown.

[0076] (6) Testing A thermoelectric cooler device is manufactured using the N-type bismuth telluride thermoelectric cooler material prepared in step (5), and a corresponding life test is performed.

[0077] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler, characterized in that: The specific steps are: 1) Activating the cut and roughened thermoelectric refrigeration material wafer to obtain an activated thermoelectric refrigeration material wafer; 2) electroplating a tin-nickel alloy on the surface of the activated thermoelectric refrigeration material obtained in step 1) to obtain an electroplated tin-nickel layer on the surface of the activated thermoelectric refrigeration material; 3) performing chemical nickel plating on the surface of the electroplated tin-nickel layer obtained in step 2) to obtain a chemical nickel plating layer on the surface of the electroplated tin-nickel layer; 4) Repeat steps 2) and 3) 5) Tin plating is performed on the chemically plated nickel layer finally obtained in step 4) to obtain a nickel-tin alloy cyclic plating layer.

2. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 1, characterized in that: The reagent for the activation treatment in step 1) is hydrochloric acid.

3. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 2, characterized in that: The concentration of the hydrochloric acid is 5-25 vol%.

4. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 1, characterized in that: In step 2): The plating solution includes nickel sulfate 50~55g / L, nickel chloride 250~275g / L, stannous chloride 30~40g / L, ammonium chloride 40~50g / L, concentrated hydrochloric acid 15~25ml / L, sodium fluoride 30~40g / L, boric acid 20~30g / L; The pH of electroplating is 2~2.

5.

5. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 4, characterized in that: The pH of the electroplating was adjusted by ammonia.

6. A method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric refrigerator according to claim 1 or 4, characterized in that: The parameters for electroplating are: The electroplating temperature is 60~70℃; The current density of electroplating is 1~1.5A / dm 2 ; The electroplating time is 8~15min.

7. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 1, characterized in that: In step 3): The chemical nickel plating solution includes sodium hypophosphite 15~25g / L, nickel chloride 150~180g / L, sodium tartrate 10~20g / L, and ammonium chloride 20~30g / L; The temperature of chemical nickel plating is 85~90℃; The time is 4 to 10 minutes; The pH of chemical nickel plating is 4.5~5.

8. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 7, characterized in that: The reagent used to adjust the pH of chemical nickel plating is ammonia water.

9. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric refrigerator according to claim 1 or 2, characterized in that: The number of repetitions in step 4) is 0 or more.

10. The method for preparing a cyclic plating layer of tin-nickel alloy suitable for a long-life thermoelectric cooler according to claim 1, characterized in that: The thermoelectric material is a thermoelectric material with N / P type bismuth telluride as the main body, and the surface of the thermoelectric material is chemically etched.

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