Electroplating pretreatment method and electroplating method for surface of metal foil

Abstract

The invention relates to the technical field of electroplating, in particular to an electroplating pretreatment method for a metal foil surface and an electroplating method. According to the embodiment of the invention, the cleaning agent is used for cleaning the surface of the metal foil, so that dirt and an oxide layer on the surface of the metal foil can be preliminarily removed. After the surface of the metal foil is cleaned, the metal foil is subjected to electrolytic activation treatment. In the process of electrolytic activation treatment, an electrode reaction formula is as follows: an anode: 4OH-4e-> O2 superscript + 2H2O; and the cathode is 2H + + 2e-> H2 (gas). In the process of carrying out electrolytic activation treatment on the metal foil, the nascent state hydrogen of the cathode enables a passive film on the surface of the metal foil to be damaged more easily, so that the metal foil obtains an activated and clean surface, and the binding force between the surface of the metal foil and an electroplated layer is further improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of electroplating technology, and more particularly to an electroplating pretreatment method and an electroplating method for a metal foil surface. Background Art

[0002] Metal foil resistors have the advantages of small size, low power consumption, small resistance temperature coefficient and high long-term stability. They are widely used in defense, military, mobile communications and automobile industries. Metal foil can be used to prepare foil strain gauges and patch resistors. At present, the materials of metal foil resistors are mainly constantan, manganese white copper and nickel-chromium modified alloy. Nickel-chromium modified alloy foil has the advantages of high resistivity and low resistance temperature coefficient, and is currently the best metal foil resistor.

[0003] In the actual use of nickel-chromium modified alloy foil, it needs to be plated to facilitate better soldering of the product. However, due to the presence of chromium and other trace elements, there is a smooth and dense oxide layer on the surface of the nickel-chromium modified alloy foil, resulting in extremely poor bonding between its surface and the metal coating. Summary of the invention

[0004] The embodiments of the present application provide a metal foil surface pre-plating treatment method and an electroplating method, which can enhance the bonding force between the surface of the nickel-chromium modified alloy foil and the metal plating layer by treating the surface of the nickel-chromium modified alloy foil.

[0005] In a first aspect of the present application, a method for pre-plating treatment of a metal foil surface is provided, wherein the material of the metal foil is a nickel-chromium modified alloy, and the method comprises: cleaning the surface of the metal foil with a cleaning agent; performing an electrolytic activation treatment on the metal foil using the metal foil as a cathode and an inert electrode as an anode; wherein the electrolyte used for the electrolytic activation treatment comprises a first inorganic acid and a first metal corrosion inhibitor, and the first metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the dilute sulfuric acid.

[0006] In the embodiment of the present application, the surface of the metal foil is cleaned with a cleaning agent to preliminarily remove dirt and an oxide layer on the surface of the metal foil. After the surface of the metal foil is cleaned, the metal foil is subjected to an electrolytic activation treatment. During the electrolytic activation treatment, the electrode reaction formula is as follows:

[0007] Anode: 4OH - -4e - →O2↑+2H2O

[0008] Cathode: 2H + +2e - →H2↑

[0009] During the electrolytic activation process of the metal foil, the primary hydrogen at the cathode makes the passivation film on the surface of the metal foil more vulnerable to damage, so that the metal foil obtains an activated and clean surface, which further improves the bonding strength between the surface of the metal foil and the electroplating layer.

[0010] In some embodiments, the first inorganic acid includes sulfuric acid and / or phosphoric acid; and the first metal corrosion inhibitor includes at least one of citric acid, hydrogen peroxide, urea, and a saturated solution of disodium hydrogen phosphate.

[0011] In some embodiments, in the dilute sulfuric acid, the first inorganic acid includes sulfuric acid, and the volume of the sulfuric acid accounts for 10%-15% of the total volume of the electrolyte.

[0012] In some embodiments, the electrolytic activation treatment time is 0 to 10 minutes; and during the electrolytic activation treatment, the current density of the anode is 1A / dm 2 ~5A / dm 2 .

[0013] In some embodiments, the method further comprises: stirring the electrolyte during the electrolytic activation treatment.

[0014] In some embodiments, the cleaning agent includes an alkaline solution, and the cleaning of the surface of the metal foil using the cleaning agent includes: soaking the metal foil in the alkaline solution for 5 minutes to 30 minutes at a temperature of 25°C to 80°C to clean the surface of the metal foil; wherein the alkaline solution includes at least one of sodium hydroxide, sodium phosphate, sodium carbonate and alkyl sulfonate.

[0015] In some embodiments, the cleaning agent also includes a hydrocarbon organic solvent, and the use of the cleaning agent to clean the surface of the metal foil also includes: soaking, wiping or rinsing the metal foil with the hydrocarbon organic solvent to clean the surface of the metal foil; wherein the hydrocarbon organic solvent includes at least one of acetone, toluene, vinyl chloride, tetrachloroethylene, trichloroethylene and carbon tetrachloride.

[0016] In some embodiments, the cleaner also includes an acidic solution, and the use of the cleaner to clean the surface of the metal foil also includes: soaking the metal foil in the acidic solution for 0 min to 30 min; wherein the acidic solution includes a second inorganic acid and a second metal corrosion inhibitor, and the second metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the inorganic acid.

[0017] In some embodiments, the second inorganic acid includes at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, chromic anhydride and hydrofluoric acid; the second metal corrosion inhibitor includes at least one of di-o-toluenethiourea, hexamethylenetetramine, thiourea and urea.

[0018] In the second aspect of the present application, a method for electroplating a metal foil surface is also provided, the method comprising: performing electroplating pre-treatment on the surface of the metal foil according to the method described in the first aspect; and electroplating on the surface of the metal foil after the electroplating pre-treatment.

[0019] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 Some embodiments of the present application provide a method for pre-electroplating treatment of a metal foil surface. DETAILED DESCRIPTION

[0022] The principles and spirit of the present disclosure will be described below with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that the description of these specific embodiments is only to enable those skilled in the art to better understand and implement the present disclosure, and does not limit the scope of the present disclosure in any way. In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art.

[0023] As used herein, the term "including" and similar terms should be understood as open inclusion, i.e., "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects, and are only used to distinguish the objects referred to, without implying a specific spatial order, temporal order, order of importance, etc. of the objects referred to.

[0024] In an embodiment of the present application, the material of the metal foil is a nickel-chromium modified alloy, such as nickel-chromium alloy, nickel-chromium-aluminum-iron alloy, nickel-chromium-manganese-silicon alloy and nickel-chromium-aluminum-copper alloy. Due to the presence of chromium and other trace elements, a smooth and dense oxide layer is easily generated on the surface of the nickel-chromium modified alloy. The oxide layer will affect the bonding strength between the metal foil substrate and the coating. In addition, there are usually pollutants such as oil on the surface of the metal foil. Based on this, an embodiment of the present application provides a method for electroplating pretreatment of the metal foil surface, which can effectively remove the pollution and oxide layer on the metal foil surface and improve the bonding strength between the metal foil substrate and the coating.

[0025] For example, Figure 1 The electroplating pretreatment method of the metal foil surface provided by some embodiments of the present application is shown. Figure 1 , the method comprises the following steps:

[0026] Step 11: Use a cleaning agent to clean the surface of the metal foil.

[0027] In the embodiments of the present application, in order to remove oil stains on the surface of the metal foil and preliminarily remove oxides on the surface of the metal foil, it is necessary to clean the surface of the metal foil with a practical cleaning agent.

[0028] In some embodiments, in order to remove grease from the surface of the metal foil, the cleaning agent includes an alkaline solution. The alkaline solution specifically includes an alkali, an inorganic salt and a surfactant. In certain embodiments of the present application, the alkali can be sodium hydroxide; the inorganic salt can be sodium phosphate and sodium carbonate; and the surfactant can be an alkyl sulfonate.

[0029] In some embodiments, step 11 specifically includes: soaking the metal foil in an alkaline solution for 5 min to 30 min at a temperature of 25° C. to 80° C. to clean the surface of the metal foil, wherein the alkaline solution includes at least one of sodium hydroxide, sodium phosphate, sodium carbonate and alkyl sulfonate.

[0030] In some embodiments, in order to further remove grease on the surface of the metal foil, the cleaning agent further comprises a hydrocarbon organic solvent; wherein the hydrocarbon organic solvent comprises at least one of acetone, toluene, vinyl chloride, tetrachloroethylene, trichloroethylene and carbon tetrachloride. Compared with other non-hydrocarbon organic solvents, such as methanol, ethanol, etc., hydrocarbon organic solvents have a better cleaning effect on grease on the surface of the metal foil.

[0031] In some embodiments, step 11 specifically further includes soaking, wiping or rinsing the metal foil with a hydrocarbon organic solvent to clean the surface of the metal foil. Among the hydrocarbon organic solvents, short-chain hydrocarbons such as trichloroethylene, toluene, and acetone have better degreasing effects; directly wiping the surface of the metal foil with trichloroethylene, toluene and / or acetone can achieve a better cleaning effect. For organic solvents with weaker degreasing effects, such as ethanol and ethylene glycol, ultrasonic cleaning and other processes are required to achieve a better cleaning effect.

[0032] In some embodiments, in order to remove the oxide layer on the surface of the metal foil, the cleaning agent also includes an acidic solution, and step 11 specifically includes: soaking the metal foil in the acidic solution for 0 min to 30 min; wherein the acidic solution includes a second inorganic acid and a second metal corrosion inhibitor, the second metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the inorganic acid, and the second inorganic acid is used to remove the oxide layer on the surface of the metal foil. In some embodiments, the second inorganic acid includes at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, chromic anhydride and hydrofluoric acid; the second metal corrosion inhibitor includes at least one of di-o-toluene thiourea, hexamethylenetetramine, thiourea and urea.

[0033] In some embodiments, the surface of the metal foil may be cleaned using an alkaline solution, a hydrocarbon organic solvent, and an acidic solution, respectively. Specifically, the surface of the metal foil may be cleaned using an alkaline solution and a hydrocarbon organic solvent first to remove grease and other contaminants on the surface of the metal foil, and then an acidic solution may be used to preliminarily remove the oxide layer on the surface of the metal foil.

[0034] Step 12, using the metal foil as the cathode and the inert electrode as the anode, the metal foil is subjected to electrolytic activation treatment; wherein the electrolyte used in the electrolytic activation treatment includes a first inorganic acid and a first metal corrosion inhibitor, and the first metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the dilute sulfuric acid.

[0035] In the embodiment of the present application, in order to further improve the bonding force between the metal foil surface and the electroplating layer, the metal foil needs to be subjected to cathodic activation treatment. Specifically, the metal foil is subjected to electrolytic activation treatment, that is, the metal foil is used as the cathode, the inert electrode is used as the anode, and the first inorganic acid and the first metal corrosion inhibitor are used as the electrolyte to carry out an electrolytic reaction. That is, the electrolyte includes the first inorganic acid and the first metal corrosion inhibitor, and the first metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by dilute sulfuric acid. The inert electrode can specifically be a graphite plate, a lead plate, a stainless steel plate or a titanium alloy plate, etc.

[0036] In some embodiments, the first metal corrosion inhibitor includes at least one of citric acid, hydrogen peroxide, urea, and a saturated solution of disodium hydrogen phosphate. In some embodiments, the first inorganic acid includes sulfuric acid, and the volume of the sulfuric acid accounts for 10%-15% of the total volume of the electrolyte. In other embodiments, the first inorganic acid may also include sulfuric acid.

[0037] In some embodiments, in order to improve the activation effect on the surface of the metal foil, the electrolytic activation treatment time is 0 to 10 minutes; and during the electrolytic activation treatment, the current density of the anode is 1A / dm 2 ~5A / dm 2 .

[0038] In some embodiments, the method further comprises: stirring the electrolyte during the electrolytic activation process to help discharge the gas generated on the anode and cathode and prevent bubbles from staying on the surface of the metal foil. The stirring method may be pneumatic stirring.

[0039] In the embodiments of the present application, during the electrolytic activation treatment, the electrode reaction formula is as follows:

[0040] Anode: 4OH - -4e - →O2↑+2H2O

[0041] Cathode: 2H + +2e - →H2↑

[0042] During the electrolytic activation process of the metal foil, the primary hydrogen at the cathode makes the passivation film on the surface of the metal foil more vulnerable to damage, so that the metal foil obtains an activated and clean surface, which further improves the bonding strength between the surface of the metal foil and the electroplating layer.

[0043] In some embodiments, after the metal foil is subjected to electrolytic activation treatment, the above method further includes determining whether the surface of the metal foil after the electrolytic activation treatment is qualified. If qualified, the surface of the metal foil after the electrolytic activation treatment can be electroplated; if unqualified, repeating steps 11 to 12 to continue to perform pre-electroplating treatment on the surface of the metal foil.

[0044] In some embodiments, the method for judging whether the surface of the metal foil after electrolytic activation treatment is qualified is as follows: if the surface of the metal foil after electrolytic activation treatment is bright and the water film on the surface of the metal foil is uninterrupted, then the surface of the metal foil after electrolytic activation treatment is qualified; otherwise, it is unqualified.

[0045] In a second aspect of the present application, a method for electroplating a metal foil surface is also provided, the method comprising: performing electroplating pre-treatment on the surface of the metal foil according to the method provided in the above embodiment; and electroplating on the surface of the metal foil after the electroplating pre-treatment.

[0046] Several embodiments of the present application are provided below.

[0047] Example 1

[0048] A method for pre-treatment of a metal foil surface by electroplating, the method comprising the following steps:

[0049] (1) After the metal foil is immersed in a 10% sodium hydroxide aqueous solution for 10 minutes, the metal foil is taken out and washed with deionized water.

[0050] (2) The metal foil was ultrasonically treated in anhydrous ethanol for 10 min, and then washed with deionized water.

[0051] (3) placing the metal foil in an acidic solution, soaking it at 40° C. for 5 minutes, and then washing the metal foil with deionized water, wherein the acidic solution includes 10% hydrochloric acid and 0.5% hexamethylenetetramine.

[0052] (4) The metal foil is used as the cathode and the inert electrode is used as the anode to perform cathode electrolytic activation treatment on the metal foil; the electrolyte includes 15% sulfuric acid, 10% phosphoric acid and 12% citric acid. The anode plate is a lead plate, the temperature of the electrolytic activation treatment is 50°C, and the current density of the anode during the electrolytic activation treatment is 5A / dm 2 The electrolytic activation treatment time is 10 min.

[0053] Example 2

[0054] A method for pre-treatment of a metal foil surface by electroplating, the method comprising the following steps:

[0055] (1) After immersing a metal foil in an alkaline solution at 40° C. for 5 minutes, the metal foil is taken out and washed with deionized water; wherein the alkaline solution includes 5% sodium carbonate, 3% sodium phosphate and 3% sodium silicate.

[0056] (2) After wiping the surface of the metal foil with trichloroethylene, the metal foil is cleaned with deionized water.

[0057] (3) placing the metal foil in an acidic solution, soaking it at 40° C. for 5 minutes, and then washing the metal foil with deionized water, wherein the acidic solution includes 20% sulfuric acid and 0.5% thiourea.

[0058] (4) using the metal foil as the cathode and the inert electrode as the anode, subjecting the metal foil to a cathode electrolytic activation treatment; the electrolyte comprises 60% phosphoric acid and 12% chromic anhydride, the anode plate is a lead plate, the electrolytic activation treatment temperature is 65° C., and the anode current density during the electrolytic activation treatment is 5 A / dm 2 The electrolytic activation treatment time is 10 min.

[0059] Example 3

[0060] A method for pre-treatment of a metal foil surface before electroplating, the method comprising the following steps:

[0061] (1) After immersing the metal foil in an alkaline solution at 40° C. for 5 minutes, the metal foil is taken out and washed with deionized water; wherein the alkaline solution includes 5% sodium hydroxide, 5% sodium phosphate, and 5% sodium carbonate.

[0062] (2) After wiping the surface of the metal foil with acetone, the metal foil is cleaned with deionized water.

[0063] (3) placing the metal foil in an acidic solution, soaking it at 40° C. for 5 minutes, and then washing the metal foil with deionized water, wherein the acidic solution includes 20% sulfuric acid and 0.5% thiourea.

[0064] (4) The metal foil is used as a cathode and the inert electrode is used as an anode to perform a cathode electrolytic activation treatment on the metal foil; the electrolyte includes 10% sulfuric acid and 12% chromic anhydride; the anode plate is a graphite plate, the temperature of the electrolytic activation treatment is 65° C., and the current density of the anode during the electrolytic activation treatment is 5 A / dm 2 The electrolytic activation treatment time is 8 minutes.

[0065] Example 4

[0066] A method for pre-treatment of a metal foil surface before electroplating, the method comprising the following steps:

[0067] (1) After immersing the metal foil in an alkaline solution at 40° C. for 5 minutes, the metal foil is taken out and washed with deionized water; wherein the alkaline solution includes 5% sodium hydroxide, 5% sodium phosphate and 5% sodium carbonate.

[0068] (2) After wiping the surface of the metal foil with acetone, the metal foil is cleaned with deionized water.

[0069] (3) placing the metal foil in an acidic solution, soaking it at room temperature for 3 minutes, and then washing the metal foil with deionized water, wherein the acidic solution includes 20% hydrochloric acid and 10% ferric chloride.

[0070] (4) The metal foil is used as the cathode and the inert electrode is used as the anode to perform cathode electrolytic activation treatment on the metal foil; the electrolyte includes 10% sulfuric acid, 63% phosphoric acid, and 6% chromic anhydride. The anode plate is a graphite plate, the temperature of the electrolytic activation treatment is 65°C, and the current density of the anode during the electrolytic activation treatment is 5A / dm 2 The electrolytic activation treatment time is 8 minutes.

[0071] The metal foils provided in Examples 1-4 whose surfaces have been pre-treated for electroplating are electroplated to form electroplated layers (such as electroplated copper layers and electroplated nickel layers) on the surfaces of the metal foils, and the bonding strength between the surfaces of the metal foils provided in each example and the electroplated layers is tested. The test results show that the bonding strength between the surfaces of the metal foils provided in each example and the electroplated layers is above 5B, which can meet the performance requirements. Therefore, the electroplating pre-treatment method for the surface of the metal foil provided in the examples of the present application can effectively improve the problem of poor bonding strength between the surface of the nickel-chromium modified alloy foil and the electroplated layer.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for pre-treatment of a metal foil surface by electroplating, characterized in that: The material of the metal foil is a nickel-chromium modified alloy, and the method comprises: Cleaning the surface of the metal foil using a cleaning agent; Using the metal foil as a cathode and the inert electrode as an anode, the metal foil is subjected to electrolytic activation treatment; The electrolyte used in the electrolytic activation treatment includes a first inorganic acid and a first metal corrosion inhibitor, and the first metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the dilute sulfuric acid.

2. The method according to claim 1, characterized in that The first inorganic acid includes sulfuric acid and / or phosphoric acid; The first metal corrosion inhibitor includes at least one of citric acid, hydrogen peroxide, urea and a saturated solution of disodium hydrogen phosphate.

3. The method according to claim 2, characterized in that The first inorganic acid includes sulfuric acid, and the volume of the sulfuric acid accounts for 10%-15% of the total volume of the electrolyte.

4. The method according to claim 1, characterized in that The electrolytic activation treatment time is 0 to 10 minutes; and During the electrolytic activation treatment, the current density of the anode is 1A / dm 2 ~5A / dm 2 .

5. The method according to claim 1, characterized in that The method further comprises: During the electrolytic activation treatment, the electrolyte is stirred.

6. The method according to any one of claims 1 to 5, characterized in that: The cleaning agent includes an alkaline solution, and the cleaning agent is used to clean the surface of the metal foil, including: Under the temperature condition of 25° C. to 80° C., soaking the metal foil in an alkaline solution for 5 min to 30 min to clean the surface of the metal foil; Wherein, the alkaline solution includes at least one of sodium hydroxide, sodium phosphate, sodium carbonate and alkyl sulfonate.

7. The method according to claim 6, characterized in that The cleaning agent further comprises a hydrocarbon organic solvent, and the cleaning agent is used to clean the surface of the metal foil, and further comprises: Soaking, wiping or washing the metal foil with a hydrocarbon organic solvent to clean the surface of the metal foil; Wherein, the hydrocarbon organic solvent includes at least one of acetone, toluene, vinyl chloride, tetrachloroethylene, trichloroethylene and carbon tetrachloride.

8. The method according to claim 6, characterized in that The cleaning agent also includes an acidic solution, and the cleaning of the surface of the metal foil using the cleaning agent also includes: Soaking the metal foil in the acidic solution for 0 to 30 minutes; The acidic solution includes a second inorganic acid and a second metal corrosion inhibitor, and the second metal corrosion inhibitor is used to prevent or slow down the corrosion of the metal foil by the inorganic acid.

9. The method according to claim 8, characterized in that The second inorganic acid comprises at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, chromic anhydride and hydrofluoric acid; The second metal corrosion inhibitor includes at least one of di-o-toluenethiourea, hexamethylenetetramine, thiourea and urea.

10. A method for electroplating a metal foil surface, characterized in that: The method comprises: Performing a pre-plating treatment on the surface of the metal foil according to the method described in any one of claims 1 to 9; Electroplating is performed on the surface of the metal foil after the electroplating pre-treatment.

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