Ceramic relay shell secondary metallization nickel electroplating pretreatment process

Abstract

The invention provides a secondary metallization nickel electroplating pretreatment process for a ceramic relay shell, which comprises the following steps: S1, pretreatment: carrying out soaking micro-etching on the surface of the shell by using a micro-etching solution to form a metal rough surface; s2, activating: soaking and activating the shell treated in S1 with acid; s3, nickel pre-plating: carrying out pre-plating treatment on the shell treated in S2 in a nickel pre-plating solution; and S4, soft nickel electroplating, wherein nickel plating is conducted in a nickel plating system. Pretreatment is carried out before conventional electroplating, a dense nickel layer with high deep plating capacity is plated, and the problem of blistering in subsequent welding is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic electroplating, and in particular to a secondary metallization nickel electroplating pretreatment process for a ceramic relay housing. Background Art

[0002] In modern industrial production, electroplating has been widely used. After the ceramics are metallized once, it is generally difficult to directly weld them with common solders. They need to be metallized twice (nickel electroplating or nickel coating and sintered nickel). Most manufacturers choose the nickel electroplating method to improve the fluidity of the solder on the metallized surface and prevent the solder from corroding the metallized layer.

[0003] At present, two electroplating processes are commonly used for secondary metallization of ceramics. One is to use ordinary electroplating process, such as Watt dark nickel type of nickel sulfate-nickel chloride-boric acid, and the other is the stress-free nickel plating process of nickel sulfamate. With these two electroplating processes, many small raised spots appear on the metal surface of the ceramic relay housing after nickelization or brazing. Especially after nickelization, these raised nickel spots appear. If you press them gently with your hand, the raised spots (that is, bubbles) will be smoothed. This shows that the raised place is a hole. This situation occurs because: molybdenum manganese sintering is a mixture of organic paste and metal oxides as raw materials laid on the ceramic surface for wet hydrogen sintering. That is, the molybdenum wire furnace is reduced and sintered in a hydrogen atmosphere, reducing the metal oxide to metal, and the organic matter is converted into carbon oxides such as carbon or CO. Due to the generation of gas, the ceramic surface after molybdenum manganese sintering is loose and porous. In the subsequent brazing process of the ceramic relay housing, in order to avoid the presence of organic matter such as sulfur, the dark nickel plating process is used, but the deep plating ability of this process is poor. In the loose and porous molybdenum-manganese layer, nickel cannot be plated from the bottom layer of the voids or microcracks. This is the nickel layer closing the pores or forming holes in the cracks of the microcracks. These holes have a serious impact on the air tightness and tensile strength of the housing, and are a great hidden danger to the housing quality.

[0004] With the development of new energy vehicles, ceramic relay housing is an important part of the battery. Air tightness and tensile strength are two important index parameters. Blisters (holes) are easily generated on the surface of ceramic secondary metallization welding, which seriously affects air tightness and tensile strength.

[0005] The quality of nickel plating on the metallized surface of ceramic parts directly affects the sealing quality of metallized ceramics and metal parts. The existing electroplating methods include electroplating nickel and chemical nickel plating. The document (Liu Huiqing, "Chemical nickel plating process for ceramic-metal sealing", Vacuum Electronic Technology, 2006, No. 2, pp. 55-58) describes the conventional processes and advantages and disadvantages of existing electroplating nickel and chemical nickel plating. The document discloses that the process flow of existing electroplating nickel is: ① cleaning metallized ceramic parts; ② soaking in dilute hydrochloric acid; ③ flushing; ④ immersing in plating solution; ⑤ adjusting the current for electroplating; ⑥ taking out from the plating solution; ⑦ flushing; ⑧ boiling in deionized water; ⑨ drying. The nickel plating system is a nickel sulfate system. The prepared nickel layer has poor all-plating ability and depth ability, and general air tightness, wear resistance and corrosion resistance, which greatly limits the application of the electroplating nickel process.

[0006] For example, patent CN104073850A discloses a method for electroplating nickel on a ceramic metal layer, which includes pre-treating the ceramic metal layer, activating the surface of the ceramic metal layer with acidic and alkaline solutions, and then electroplating. The electroplating is performed by controlling the alternating change of the current density, and the surface coating thickness of the obtained product is uniform, but the problem of welding blistering is not solved.

[0007] Therefore, how to solve welding blistering is an urgent problem for ceramic relay housing manufacturers. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a ceramic relay housing secondary metallization nickel plating pretreatment process, which performs pretreatment before conventional electroplating to plate a nickel layer with strong deep plating ability and density, thereby effectively solving the subsequent welding blistering problem.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] In one aspect, the present invention provides a ceramic relay housing secondary metallization nickel plating pretreatment process, comprising the following steps:

[0011] S1 pre-treatment: Use micro-etching solution to immerse and micro-etch the shell surface to form a rough metal surface;

[0012] S2 activation: The shell treated with S1 is activated by acid immersion;

[0013] S3 pre-nickel plating: pre-plating the shell treated in S2 in a pre-nickel plating solution;

[0014] S4 soft nickel plating: nickel plating is carried out in a nickel plating system.

[0015] Furthermore, the micro-etching solution includes concentrated sulfuric acid and hydrogen peroxide.

[0016] Furthermore, the micro-etching solution includes concentrated sulfuric acid, hydrogen peroxide, thiourea, polyethylene glycol, EDTA-2Na salt and phytic acid.

[0017] Furthermore, in the micro-etching solution, the concentration of concentrated sulfuric acid is 50-65 ml / L; hydrogen peroxide is 200-300 ml / L; thiourea is 2-3 g / L; polyethylene glycol is 0.5-2 g / L; EDTA-2Na salt is 0.5-2 g / L; and phytic acid is 0.2-1.0 ml / L.

[0018] Further, in the micro-etching solution, the concentration of concentrated sulfuric acid is 60 ml / L; hydrogen peroxide is 250 ml / L; thiourea is 2 g / L; polyethylene glycol is 1 g / L; EDTA-2Na salt is 1 g / L; and phytic acid is 0.5 ml / L. Further, the concentrated sulfuric acid is 98% sulfuric acid. Further, the polyethylene glycol is selected from polyethylene glycol 2000, polyethylene glycol 4000 or polyethylene glycol 6000.

[0019] In the micro-etching solution adopted by the present invention, sulfuric acid and hydrogen peroxide are main components, which are used to remove oxide film and corrode metal surface; thiourea and polyethylene glycol are used in combination, which are mainly used to prevent over-corrosion of uniform metal surface; EDTA-2Na salt and phytic acid are hydrogen peroxide stabilizers, which prevent the concentration of hydrogen peroxide from changing too much and affecting the corrosion effect.

[0020] Furthermore, the micro-etching temperature is 20-30° C. Furthermore, the immersion micro-etching time is 30-60 seconds.

[0021] Furthermore, the acid is hydrochloric acid with a concentration of 100-150 ml / L.

[0022] Further, in S2, the activation temperature is 15-25°C, and the activation time is 1-5 minutes. Further, in S2, the activation temperature is 20-25°C, and the activation time is 3-5 minutes.

[0023] Further, the nickel pre-plating solution includes nickel sulfate, dimethylaminoborane (DMAB), sodium citrate trihydrate, citric acid monohydrate, sodium acetate, boric acid, polyethylene glycol, KI and KIO3.

[0024] Furthermore, in the pre-nickel plating solution, the nickel sulfate concentration is 20-30 ml / L; the dimethylaminoborane concentration is 1-5 ml / L; the sodium citrate trihydrate concentration is 15-30 ml / L; the citric acid monohydrate concentration is 7-15 ml / L; the sodium acetate concentration is 10-20 ml / L; the boric acid concentration is 10-15 ml / L; the polyethylene glycol concentration is 0.5-1 ml / L; the KI concentration is 0.5-1.5 ml / L; and the KIO3 concentration is 2-5 ml / L.

[0025] Furthermore, in the pre-nickel plating solution, the nickel sulfate concentration is 25 ml / L; the dimethylaminoborane concentration is 2 ml / L; the sodium citrate trihydrate concentration is 20 ml / L; the citric acid monohydrate concentration is 10 ml / L; the sodium acetate concentration is 15 ml / L; the boric acid concentration is 12 ml / L; the polyethylene glycol concentration is 0.5 ml / L; the KI concentration is 1 ml / L; and the KIO3 concentration is 3 ml / L.

[0026] Furthermore, the pH of the pre-nickel plating solution is 7.8-8.8, preferably 8.5, and ammonia water is used to adjust the pH of the solution.

[0027] Furthermore, the temperature of the pre-plating treatment is 40-60° C., preferably 45° C. Furthermore, the current of the pre-plating treatment is 0.5-1A, and the time is 5-10s.

[0028] Furthermore, the amount of nickel loaded on the surface of the shell obtained after the pre-plating treatment is 0.5 to 2.0 dm 2 / L, preferably 1.5dm 2 / L. Further, the deposition rate of nickel on the shell surface obtained after the pre-plating treatment is 1-10 um / h, preferably 4.0 um / h. Further, the thickness of the nickel layer on the shell surface obtained after the pre-plating treatment is controlled to be 0.5-1.0 um.

[0029] The main salt of the pre-nickel plating solution of the present invention is nickel sulfate; DMAB is used as a reducing agent to avoid the problem of nickel layer melting caused by brazing temperature fluctuations in the subsequent brazing process, thereby affecting the problem of air tightness of the nickel layer; sodium citrate trihydrate, citric acid monohydrate and sodium acetate are combined complexing agents, which on the one hand avoid the deposition of nickel ions and thus reduce the pre-nickel plating efficiency, and on the other hand effectively ensure the efficiency of nickel sulfate nickel plating, and try to reduce the cost consumption of the pre-nickel plating solution; boric acid is a pH buffer and preservative, which prevents chemical nickel from being easily caused by bacterial reproduction due to the complexing agent citric acid when it is stopped, which will cause the coating quality to be not meticulous. The addition of boric acid can sterilize and inhibit the generation of bacteria, and maintain the stability of the pre-nickel plating solution. Polyethylene glycol is a surfactant, which reduces the generation of pinholes in the nickel layer. Potassium iodide and potassium iodate are combined stabilizers, which are harmless to the physical and chemical properties of the coating and can effectively slow down the autocatalytic speed of the pre-nickel plating solution. The pre-nickel plating solution of the present invention is a phosphorus-free solution, which solves the defect of phosphorus in the chemical nickel plating solution (pre-nickel plating solution), can prevent the phosphorus in the nickel layer from affecting the subsequent brazing effect, and can also avoid the leakage phenomenon of subsequent brazing. The pre-nickel plating solution of the present invention is a chemical nickel system, does not contain phosphorus, and can trigger chemical nickel after a layer of nickel is forcibly plated on the shell.

[0030] Further, the nickel plating system includes nickel, nickel chloride, and boric acid. Further, the nickel plating system includes a nickel concentration of 25 to 35 g / L, a nickel chloride concentration of 3 to 7 g / L, and a boric acid concentration of 35 to 50 g / L. Further, the nickel plating system includes a nickel concentration of 30 g / L, a nickel chloride concentration of 5 g / L, and a boric acid concentration of 40 g / L.

[0031] Furthermore, the pH of the nickel plating system is 3.8-4.5, preferably 4.

[0032] Furthermore, the temperature of the soft nickel electroplating is 40-50° C., preferably 45° C. Furthermore, the shell D of the soft nickel electroplating K 0.5~1.0dm 2 , preferably 0.5dm 2 Furthermore, the current density of the soft nickel electroplating is 1 to 40 A / dm 3 .

[0033] Furthermore, after the soft nickel electroplating step, the thickness of the nickel layer on the shell is controlled to be 1.5-2.0 um, and the thickness of the nickel layer of the final product is controlled to be 2-3.5 um.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] ① Through the micro-etching step, the surface deep oxide film is removed to form a uniform and fresh metal rough surface, creating a good metal surface layer for subsequent nickel plating. Through the activation step, a small amount or slight oxide film on the metal surface layer is removed. In the pre-nickel plating process, alkaline chemical nickel is used to provide a chemical nickel layer with good ductility and strong deep plating ability. Because phosphorus is an unfriendly element for brazing and easily forms harmful components such as secondary crystal phases with iron, the pre-nickel plating solution uses nickel-boron chemical nickel, which is phosphorus-free chemical nickel. In the soft nickel electroplating process, the nickel layer is thickened by the aminosulfonic acid nickel process. The nickel plating system used mainly obtains the nickel layer plated by aminosulfonic acid nickel. The nickel layer can achieve stress-free or low-stress, which has a great effect on the subsequent brazing without cracking.

[0036] ② Compared with the conventional electroplating process, after pretreatment by the method of the present invention, there is almost no blistering in the product obtained by subsequent nickelization or brazing, and the blistering rate is less than 0.1%, which effectively solves the problem of welding blistering in the conventional electroplating process. The method is also used in actual production and has achieved good economic results.

[0037] ③ The thickness of the nickel layer on the shell surface obtained by the method of the present invention is controlled at 2 to 3.5 um, with high tensile strength, good air tightness and fineness, and high yield rate, which is significantly better than the electroplating process in the prior art, has broad application prospects, and has almost no bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0039] Figure 1 The sample is a foaming sample after nickelization in the prior art;

[0040] Figure 2 This is a sample that has been nickelized using the method provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] As used herein:

[0042] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0043] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0044] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0045] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0046] The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing the specific embodiments and are not intended to limit the present invention. In the embodiments, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0048] The technical solution of the present invention is further described in detail below in conjunction with specific implementation methods.

[0049] Embodiment 1:

[0050] A ceramic relay housing secondary metallization nickel plating pretreatment process comprises the following steps:

[0051] S1 pre-treatment: 25℃, immerse the shell surface in micro-etching solution for 40s to form a rough metal surface, take it out and rinse it with water;

[0052] S2 activation: The shell treated with S1 was immersed in 120ml / L hydrochloric acid at 25℃ for 5 minutes, then taken out and rinsed with water;

[0053] S3 pre-nickel plating: The shell treated in S2 was pre-plated in a pre-nickel plating solution with a pH of 8.5 at 45°C, taken out, and rinsed with water. The pre-plating current was 0.8A and the time was 10s. The amount of nickel loaded on the surface of the shell obtained after the pre-plating treatment was 1.5dm 2 / L; the deposition rate of nickel on the shell surface is 4.0um / h; the thickness of the nickel layer on the shell surface is controlled at 0.5~1.0um;

[0054] S4 soft nickel plating: 45°C, nickel plating in a nickel plating system, take out, rinse with water, the soft nickel plated shell D K 0.5dm 2 , the current density of soft nickel plating is 20A / dm 3 After the soft nickel electroplating step, the thickness of the nickel layer on the shell is controlled at 1.5um, and the thickness of the nickel layer of the final product is controlled at 2um.

[0055] The micro-etching solution contains 60 ml / L of concentrated sulfuric acid, 250 ml / L of hydrogen peroxide, 2 g / L of thiourea, 1 g / L of polyethylene glycol 6000, 1 g / L of EDTA-2Na salt, and 0.5 ml / L of phytic acid. Further, the concentrated sulfuric acid is 98% sulfuric acid.

[0056] In the pre-nickel plating solution, the concentration of nickel sulfate is 25 ml / L; the concentration of dimethylaminoborane is 2 ml / L; the concentration of sodium citrate trihydrate is 20 ml / L; the concentration of citric acid monohydrate is 10 ml / L; the concentration of sodium acetate is 15 ml / L; the concentration of boric acid is 12 ml / L; the concentration of polyethylene glycol is 0.5 ml / L; the concentration of KI is 1 ml / L; and the concentration of KIO3 is 3 ml / L.

[0057] The nickel plating system has a pH of 4, including a nickel concentration of 30 g / L; a nickel chloride concentration of 5 g / L; and a boric acid concentration of 40 g / L.

[0058] Embodiment 2:

[0059] 1. A ceramic relay housing secondary metallization nickel plating pretreatment process, the detailed steps are as follows:

[0060] S1 Pretreatment: Use micro-etching solution to immerse and micro-etch the shell surface to form a rough metal surface, then take it out and rinse it with water; the experimental conditions are:

[0061] In the micro-etching solution, the concentration of concentrated sulfuric acid is 50-65 ml / L; hydrogen peroxide is 200-300 ml / L; thiourea is 2-3 g / L; polyethylene glycol is 0.5-2 g / L; EDTA-2Na salt is 0.5-2 g / L; and phytic acid is 0.2-1.0 ml / L; the micro-etching temperature is 20-30° C., and the immersion micro-etching time is 30-60 seconds.

[0062] S2 activation: The shell treated by S1 is activated by soaking in acid, taken out, and rinsed with water; the experimental conditions are:

[0063] The acid is hydrochloric acid, the concentration is 100-150 ml / L, the activation temperature is 20-25° C., and the activation time is 3-5 minutes.

[0064] S3 pre-nickel plating: the shell treated with S2 is pre-plated in a pre-nickel plating solution, taken out and rinsed with water; the experimental conditions are: in the pre-nickel plating solution, the concentration of nickel sulfate is 20-30ml / L; the concentration of dimethylaminoborane is 1-5ml / L; the concentration of sodium citrate trihydrate is 15-30ml / L; the concentration of citric acid monohydrate is 7-15ml / L; the concentration of sodium acetate is 10-20ml / L; the concentration of boric acid is 10-15ml / L; the concentration of polyethylene glycol is 0.5-1ml / L; the concentration of KI is 0.5-1.5ml / L; and the concentration of KIO3 is 2-5ml / L; the pH of the pre-nickel plating solution is 7.8-8.8, and the pH of the solution is adjusted by ammonia water. The temperature of the pre-plating treatment is 40-60°C, the current of the pre-plating is 0.8A, the time is 10s, and the loading amount of nickel on the surface of the shell obtained after the pre-plating treatment is 0.5-2.0dm 2 / L, the deposition rate of nickel on the shell surface obtained after the pre-plating treatment is 1-10 um / h, and the thickness of the nickel layer on the shell surface obtained after the pre-plating treatment is controlled to be 0.5-1.0 um,

[0065] S4 soft nickel plating: nickel plating in the nickel plating system, take out and rinse with water. The experimental conditions are:

[0066] The nickel plating system includes a nickel concentration of 25 to 35 g / L, a nickel chloride concentration of 3 to 7 g / L, and a boric acid concentration of 35 to 50 g / L. The pH of the nickel plating system is 3.8 to 4.5. The temperature of the soft nickel electroplating is 40 to 50° C., and the current density of the soft nickel electroplating is 1 to 40 A / dm 3 .

[0067] The soft nickel plated shell D K 0.5~1.0dm 2 After the soft nickel electroplating step, the thickness of the nickel layer on the shell is controlled to be 1.5-2.0um, and the thickness of the nickel layer of the final product is controlled to be 2-3.5um.

[0068] 2. Parameter selection experiment

[0069] (1) The components in the micro-etching solution were screened, and the results are shown in Table 1 below:

[0070] Table 1 Screening results of concentrations of components in microetching solution

[0071]

[0072]

[0073] (1) Screening the concentration of activated hydrochloric acid, the specific results are shown in Table 2

[0074] Table 2 Screening of the concentration of activated hydrochloric acid

[0075]

[0076]

[0077] (2) The activation step is missing. The results show that there is a residual oxide film on the shell surface. After subsequent pre-nickel plating and soft nickel electroplating, the ceramic shell surface has about 3% blistering.

[0078] (3) Screening of the components of the pre-nickel plating solution, the results are shown in Table 3

[0079] Table 3 Screening of components of pre-nickel plating solution (unit: ml / L)

[0080]

[0081]

[0082] (4) After pre-nickel plating with phosphorus-containing chemical nickel, the resulting ceramic shell leaks during brazing.

[0083] (5) Comparison of nickel plating blistering

[0084] As attached Figure 1 and attached Figure 2 It can be seen that the existing traditional electroplating method results in a lot of bubbles on the surface of the sample; the sample prepared by the method of Example 1 of the present invention has a smooth surface, no bubbles, and good air tightness and fineness.

[0085] (6) Thermal shock test

[0086] The metallized piece prepared by the present invention is sealed with a metal part as a test piece, and the test piece is kept at room temperature to 600°C for 30 minutes, and then subjected to thermal shock at room temperature. After 6 shocks, a leak test is performed, and no leaks are found, and the test results are all qualified. The whole pipe sealing finished product rate reaches 99%, and the thermal shock qualified rate reaches 100%.

[0087] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A ceramic relay housing secondary metallization nickel plating pretreatment process, characterized in that: The following steps are involved: S1 pre-treatment: Use micro-etching solution to immerse and micro-etch the shell surface to form a rough metal surface; S2 activation: The shell treated with S1 is activated by acid immersion; S3 pre-nickel plating: pre-plating the shell treated in S2 in a pre-nickel plating solution; S4 soft nickel plating: nickel plating is carried out in a nickel plating system.

2. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The micro-etching solution comprises concentrated sulfuric acid, hydrogen peroxide, thiourea, polyethylene glycol, EDTA-2Na salt and phytic acid.

3. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 2 is characterized in that: In the micro-etching solution, the concentration of concentrated sulfuric acid is 50-65 ml / L; hydrogen peroxide is 200-300 ml / L; thiourea is 2-3 g / L; polyethylene glycol is 0.5-2 g / L; EDTA-2Na salt is 0.5-2 g / L; and phytic acid is 0.2-1.0 ml / L; the micro-etching temperature is 20-30° C.; and the immersion micro-etching time is 30-60 seconds.

4. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 3 is characterized in that: In the micro-etching solution, the concentration of concentrated sulfuric acid is 60 ml / L; hydrogen peroxide is 250 ml / L; thiourea is 2 g / L; polyethylene glycol is 1 g / L; EDTA-2Na salt is 1 g / L; and phytic acid is 0.5 ml / L; the concentrated sulfuric acid is 98% sulfuric acid; and the polyethylene glycol is selected from polyethylene glycol 2000, polyethylene glycol 4000 or polyethylene glycol 6000.

5. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The acid is hydrochloric acid with a concentration of 100-150 ml / L; In S2, the activation temperature is 15 to 25°C, and the activation time is 1 to 5 minutes.

6. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The nickel pre-plating solution comprises nickel sulfate, dimethylaminoborane, sodium citrate trihydrate, citric acid monohydrate, sodium acetate, boric acid, polyethylene glycol, KI and KIO3.

7. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 6, characterized in that: In the pre-nickel plating solution, the concentration of nickel sulfate is 20-30 ml / L; the concentration of dimethylaminoborane is 1-5 ml / L; the concentration of sodium citrate trihydrate is 15-30 ml / L; the concentration of citric acid monohydrate is 7-15 ml / L; the concentration of sodium acetate is 10-20 ml / L; the concentration of boric acid is 10-15 ml / L; the concentration of polyethylene glycol is 0.5-1 ml / L; the concentration of KI is 0.5-1.5 ml / L; and the concentration of KIO3 is 2-5 ml / L.

8. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The pH of the pre-nickel plating solution is 7.8-8.8, and ammonia water is used to adjust the pH of the solution; The pre-plating temperature is 40-60°C; the pre-plating current is 0.5-1A, and the time is 5-10s; The amount of nickel loaded on the surface of the shell obtained after the pre-plating treatment is 0.5 to 2.0 dm 2 / L, the deposition rate of nickel on the shell surface obtained after the pre-plating treatment is 1-10 um / h, and the thickness of the nickel layer on the shell surface obtained after the pre-plating treatment is controlled to be 0.5-1.0 um.

9. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The nickel plating system includes nickel at a concentration of 25 to 35 g / L; nickel chloride at a concentration of 3 to 7 g / L; and boric acid at a concentration of 35 to 50 g / L; The pH of the nickel plating system is 3.8-4.

5.

10. The ceramic relay housing secondary metallization nickel plating pretreatment process according to claim 1, characterized in that: The temperature of the soft nickel electroplating is 40-50°C. K 0.5~1.0dm 2 The current density of the soft nickel electroplating is 1 to 40 A / dm 3 ; After the soft nickel electroplating step, the thickness of the nickel layer on the shell is controlled to be 1.5-2.0um, and the thickness of the nickel layer of the final product is controlled to be 2-3.5um.

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