Ni-Fe-B functional coating

Abstract

The invention relates to the technical field of electric contact materials, in particular to a Ni-Fe-B functional coating. And the Ni-Fe-B functional coating comprises the following components in atomic percent: 1 to 10 at% of B, 1 to 5 at% of Fe and the balance of Ni. According to the Ni-Fe-B functional coating, a composite structure with nickel as a base body and iron and boron as alloy elements dispersed in the Ni-Fe-B functional coating is formed, the defect of a nickel oxide layer is effectively overcome through iron and boron while the high conductivity of nickel is utilized, and the oxidation resistance of the coating is further improved. By adding a proper amount of iron and boron, the hardness and wear resistance of the functional coating are remarkably improved on the premise of reducing the influence of iron and boron on conductivity as much as possible. The Ni-Fe-B functional coating disclosed by the invention is relatively rapid to develop and apply, can meet the requirements of an electrical contact and an electronic packaging shell, remarkably reduces the production cost, and meets the requirements of RoHS (Restriction of Hazardous Substances) of EU (European Union) on Instructions about restricting the use of some toxic substances in electrical and electronic equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical contact materials, and particularly to a Ni-Fe-B functional coating. Background Art

[0002] Electrical contact materials are key materials for conducting electric current and maintaining electrical connections, and are widely used in the fields of electrical contacts and chip electronic packaging. In electrical contacts, copper and copper alloys are recognized as relatively ideal materials to replace silver contacts in the art. However, in a non-vacuum environment, as an electrical contact material, it has a major drawback, that is, it is very easy to oxidize during operation, react with oxygen in the air to generate copper oxide and cuprous oxide, and form an oxide film on the surface of the copper-based contact, resulting in an increase in the contact resistance of the contact and too high a temperature rise.

[0003] Currently, the common solutions are as follows. First, on the basis of the existing contact manufacturing process, rare earth elements or rare earth oxides are added to the contact to improve the oxidation resistance of the contact to a certain extent. However, this method has limited effect and it is difficult to achieve a stable working state like that of silver contacts. Another method is to cover a layer of coating with strong oxidation resistance and good electrical conductivity on the contact surface. For example, a processing technology of a copper-bottom silver-tungsten coating contact and a copper-bottom silver-tungsten coating contact disclosed in Patent CN117995577A. This technical solution sprays silver-tungsten alloy powder on the surface of the copper core to form a silver-tungsten alloy coating on the contact surface, achieving the effect of improving the contact life. However, the coating of this technical solution requires the use of silver, resulting in a high cost, and the coating of this technical solution needs to go through multiple heating and cooling processes, with low efficiency.

[0004] In the field of chip electronic packaging, since the chip is prone to losing its effectiveness under high-temperature conditions, aluminum-silicon-tungsten of the electronic packaging material is used to match the thermophysical properties of the chip and the external housing to achieve encapsulation with a high-silicon aluminum alloy housing. In order to improve the electrical conductivity, chemical stability, corrosion resistance of the encapsulated housing, ensure accurate signal transmission, reduce signal loss, and improve the overall performance of the device, a layer of gold is plated on the surface of its housing. In order to minimize the use of this precious metal gold, a layer of alloy film is also selected to cover the surface of the electronic packaging housing. For example, an application of a tungsten-copper composite material with high thermal conductivity as a tungsten-copper heat sink and an electronic packaging material disclosed in Patent CN103194712B. In this technical solution, through plasma spraying technology, a tungsten-copper composite coating is coated on the electronic packaging material, and the obtained electronic packaging material has a uniform and dense structure and high thermal conductivity. However, this technical solution does not test the electrical conductivity of the coating, and due to the large difference in the thermal expansion coefficients of tungsten and copper, the coating is prone to peeling at high temperatures. To sum up, in both the field of electrical contacts and the field of electronic packaging, a coating that simultaneously has good electrical conductivity and excellent oxidation resistance is needed. Summary of the Invention

[0005] The present invention aims to overcome the defects in the prior art that there is a lack of coating materials with both good conductivity and excellent oxidation resistance, and it is difficult to replace the precious metals required in the contact and electronic packaging fields, and provides a Ni-Fe-B functional coating to overcome the above defects.

[0006] In order to achieve the purpose of the above invention, the present invention is implemented by the following technical solutions: In a first aspect, the present invention discloses a Ni-Fe-B functional coating, wherein the Ni-Fe-B functional coating comprises, by atomic percentage, 1-10 at % B, 1-5 at % Fe, and the remainder Ni.

[0007] In the field of electrical contacts, copper-based contacts have low costs and the widest range of applications. To improve their conductivity, a silver alloy layer is electroplated on the contact surface. At the same time, the contacts on electrical appliances need to be welded on a bridge, which is commonly electrolytic copper. To ensure the stability of the switch, a layer of silver is also electroplated on the bridge. In the field of electronic packaging, since chips are prone to lose performance under high temperature conditions, aluminum alloys are required for packaging. To improve the packaging effect, a layer of gold is usually plated on the surface of the shell. It can be seen that in both fields, precious metal coatings are required for anti-oxidation treatment. If there is an alloy coating that can be used in both fields at the same time, it can greatly simplify the industrial production process and further reduce costs on the basis of reducing the amount of precious metals used.

[0008] In the field of electrical contacts, the surface coating of the electrical contacts requires better oxidation resistance and conductivity; while in the field of electronic packaging, the surface coating of the packaging shell needs to be more corrosion-resistant and have a certain hardness, while taking into account a certain heat dissipation. Therefore, the present invention discloses a Ni-Fe-B functional coating while taking into account the requirements of the two fields. The Ni content in this coating is the highest, thus forming a composite structure with nickel as the matrix and iron and boron as alloy elements dispersed therein. There are the following reasons for using nickel as the matrix of the functional coating. First, although the conductivity of nickel is lower than that of silver or gold, it is significantly better than that of iron and boron. Using nickel as the matrix can improve the conductivity of the coating of the present invention as much as possible; second, nickel generates a dense nickel oxide oxide layer at high temperature. The oxide layer has a high melting point (melting point 1955°C) and can effectively block oxygen diffusion. Therefore, using nickel as the matrix can ensure that the oxide layer is mainly nickel oxide, has high stability, and can significantly inhibit further oxidation of the coating.

[0009] Although the nickel coating has good oxidation resistance and high electrical conductivity, the obtained coating has low hardness and cannot meet the practical needs. First of all, in the present invention, an appropriate amount of boron is added to the functional coating. The addition of boron significantly improves the hardness and wear resistance of the coating, and boron will form boron oxide during the oxidation process. Its melting point is relatively low and it is in a liquid state at high temperatures and can flow. It can fill the microcracks and grain boundary pores of the nickel oxide layer to form a dynamic self-healing protective layer, further improving the stability of the coating at instantaneous high temperatures. However, excessive boron will form a continuous amorphous phase in the nickel matrix. Since boron and boron oxides have poor electrical conductivity, this will have a greater impact on the electrical conductivity of the coating. Therefore, through experimental verification, the content of boron in the present invention is limited to 1-10 at%, which can reduce the impact on the electrical conductivity. As the thickness of the coating increases, the possibility of microcracks appearing in the nickel matrix also becomes higher, and the content of boron can be appropriately increased.

[0010] In the application scenario of electrical contacts, frequent switching will significantly increase the temperature of the contact points of electrical contacts; in the usage scenario of chips, in the case of high power and poor heat dissipation, the temperature at the chip will rise sharply. Therefore, the functional coating of the present invention also has to cope with high-temperature environments. For this reason, after many experiments, a small amount of iron is added to the functional coating of the present invention. On the one hand, a small amount of iron forms a solid solution with nickel, promoting the formation of the NiFe2O4 spinel structure, and its compactness is better than that of nickel oxide, further slowing down the penetration of oxygen at high temperatures; on the other hand, the most common substrates for electrical contacts and electronic packaging housings are copper and aluminum, and iron can form a metal diffusion layer with them, which can effectively prevent the coating from peeling off. However, excessive iron may form iron oxide that is prone to peeling during the oxidation process. Therefore, the content of iron in the present invention is limited to 1-5 at%.

[0011] In the second aspect, the present invention discloses a contact with a Ni-Fe-B functional coating deposited on the surface, which includes a base contact material, and the Ni-Fe-B functional coating as described in claim 1 is deposited on the surface of the base contact material.

[0012] Furthermore, the thickness of the Ni-Fe-B functional coating is 1-50 μm.

[0013] Furthermore, the base contact material includes one or more of copper alloy, pure copper, and silver. The most common contacts on the market are copper alloy contacts or copper-silver composite contacts, and the functional coating of the present invention can effectively improve the oxidation resistance of these two types of contacts.

[0014] Furthermore, the copper alloy is composed of Cu and one or more of diamond, graphene, graphite, lanthanum, cerium, ytterbium, samarium, zirconium, silver, aluminum, iron, chromium, niobium, tin, zinc, tungsten, molybdenum, vanadium, indium, and tellurium.

[0015] Furthermore, in the copper alloy, calculated by mass percentage, Cu accounts for 80-99.9%.

[0016] In a third aspect, the present invention also discloses an electronic packaging housing with a Ni-Fe-B functional coating deposited on its surface, which comprises a base housing material, and the Ni-Fe-B functional coating as described in claim 1 is deposited on the surface of the base housing material.

[0017] Furthermore, the thickness of the Ni-Fe-B functional coating is 1 - 30 μm.

[0018] Furthermore, the base housing material comprises one or more of aluminum silicon, aluminum silicon carbide, and aluminum silicon tungsten.

[0019] Furthermore, in the aluminum silicon tungsten, by mass percentage, silicon accounts for 30 - 60%, tungsten accounts for 10 - 20%, and the balance is aluminum.

[0020] Therefore, the present invention has the following beneficial effects: (1) The Ni-Fe-B functional coating of the present invention forms a composite structure with nickel as the matrix and iron and boron dispersed therein as alloying elements. While utilizing the relatively high electrical conductivity of nickel, iron and boron effectively compensate for the defects of the nickel oxide layer, further improving the oxidation resistance of the coating. (2) By adding appropriate amounts of iron and boron, the present invention significantly improves the hardness and wear resistance of the functional coating on the premise of minimizing their impact on electrical conductivity. (3) The development and application of the Ni-Fe-B functional coating of the present invention are relatively fast, can meet the requirements of both electrical contacts and electronic packaging housings, significantly reduce production costs, and comply with the requirements of the EU RoHS (Restriction of Hazardous Substances) Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment. Specific Embodiments

[0021] The following further describes the present invention with reference to specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only some of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention. In the following text, the core lipid without surface modification is called O-L; the ginkgo flavonoid - astragalus polysaccharide dual-loaded liposome of the present invention is called M-L.

[0022] Example 1: Coating Composition: Nickel: 95 at%; Iron: 1 at%; Boron: 4 at%; Coating Thickness: 10 μm

[0023] The coating of this embodiment is used for an electrical contact, which is made of CuLa alloy powder with 1% La content and the balance being copper. The steps for electroplating the coating on the electrical contact are as follows: Prepare an electroplating solution containing nickel ions, iron ions, and borate in the above-mentioned ratio; Apply a DC power supply so that nickel ions and iron ions are reduced to metals by obtaining electrons on the surface of the cathode (electrical contact) and co-deposit with boron element to form the nickel-iron-boron coating of this embodiment.

[0024] Example 2: Coating composition: Nickel: 91 at%; Iron: 1 at%; Boron: 8 at%; Coating thickness: 20 μm

[0025] The coating of this embodiment is used for an electrical contact, and the composition of the contact is as follows: By mass percentage, 50% CuLa alloy powder and 50% CuZrLa alloy powder. Among them, the La content in CuLa is 1%; the Zr content in CuZrLa is 0.37%, the La content is 0.55%, and the balance is copper. Electroplate the coating of this embodiment on the electrical contact in the manner of Example 1.

[0026] Example 3: Coating composition: Nickel: 86 at%; Iron: 5 at%; Boron: 9 at%; Coating thickness: 50 μm

[0027] The coating of this embodiment is used for an electrical contact, and the composition of the contact is as follows: By mass percentage, 50% CuLa alloy powder and 50% CuZrLa alloy powder. Among them, the La content in CuLa is 1%; the Zr content in CuZrLa is 0.37%, the La content is 0.55%, and the balance is copper. Electroplate the coating of this embodiment on the electrical contact in the manner of Example 1.

[0028] Example 4: Coating composition: Nickel: 95 at%; Iron: 1 at%; Boron: 4 at%; Coating thickness: 3 μm

[0029] The coating of this embodiment is used for a bridge, and the bridge is made of pure copper. Electroplate the coating of this embodiment on the bridge in the manner of Example 1.

[0030] Example 5: Coating composition: Nickel: 91 at%; Iron: 1 at%; Boron: 8 at%; Coating thickness: 3 μm

[0031] The coating of this embodiment is used for a bridge, and the bridge is made of pure copper.

[0032] Example 6: Coating composition: Nickel: 95 at%; Iron: 1 at%; Boron: 4 at%; Coating thickness: 3 μm

[0033] The coating of this embodiment is used for an electronic packaging housing, and the housing is aluminum-silicon. By mass percentage, the silicon content is 50%, and the balance is aluminum.

[0034] Example 6: Coating composition: Nickel: 91 at%; Iron: 1 at%; Boron: 8 at%; Coating thickness: 3 μm

[0035] The coating of this embodiment is used for an electronic packaging housing, and the housing is aluminum-silicon. By mass percentage, the silicon content is 50%, and the balance is aluminum. Through electroless plating, a reducing agent is used to cause a redox reaction of nickel ions, iron ions, and borohydride in the plating solution to deposit a nickel-iron-boron alloy coating on the surface of the electronic packaging housing.

[0036] Example 7: Coating composition: Nickel: 91 at%; Iron: 1 at%; Boron: 8 at%; Coating thickness: 25 μm

[0037] The coating of this embodiment is used for an electronic packaging housing, and the housing is aluminum-silicon-tungsten. By mass percentage, silicon accounts for 40%, tungsten accounts for 10%, and the balance is aluminum. Through electroless plating, a reducing agent is used to cause a redox reaction of nickel ions, iron ions, and borohydride in the plating solution to deposit a nickel-iron-boron alloy coating on the surface of the electronic packaging housing.

[0038] Comparative Example 1: Coating composition: Nickel: 100 at%; Coating thickness: 10 μm

[0039] The coating of this embodiment is used for an electrical contact, which is made of CuLa alloy powder with 1% La content and the balance being copper. The coating is electroplated in the manner of Example 1.

[0040] Comparative Example 2: Coating composition: Nickel: 91 at%; Boron: 9 at%; Coating thickness: 20 μm

[0041] The coating of this embodiment is used for an electrical contact, and the composition of the contact is as follows: By mass percentage, 50% CuLa alloy powder and 50% CuZrLa alloy powder. Among them, the La content in CuLa is 1%; the Zr content in CuZrLa is 0.37%, the La content is 0.55%, and the balance is copper. The coating is electroplated in the manner of Example 1.

[0042] Comparative Example 3: Coating composition: Nickel: 97 at%; Iron: 3 at%; Coating thickness: 50 μm

[0043] The coating of this embodiment is used for an electrical contact, which is made of CuLa alloy powder with 1% La content and the balance being copper. The coating is electroplated in the manner of Example 1.

[0044] Comparative Example 4: Coating composition: Nickel: 80 at%; Iron: 8 at%; Boron: 12 at%; Coating thickness: 10 μm

[0045] The coating of this embodiment is used for an electrical contact, which is made of CuLa alloy powder with 1% La content and the balance being copper. The coating is electroplated in the manner of Example 1.

[0046] Comparative Example 5: Coating composition: Nickel: 100 at%; Coating thickness: 3 μm

[0047] The coating of this embodiment is used for an electronic packaging housing, which is aluminum-silicon. By mass percentage, the silicon content is 50% and the balance is aluminum. The coating is electroplated in the manner of Example 6.

[0048] The ratios of the components of the examples and comparative examples are shown in Table 1:

[0049] The resistivity, microhardness, wear rate (by weight), and oxidation resistance of the materials prepared in the above examples and comparative examples were tested.

[0050] The wear rate test method is as follows: Clean the specimens of the examples and comparative examples, and accurately measure the initial mass; Place the specimens on a friction and wear testing machine, and set the same loading load, friction speed and other parameters for the experiment; After the experiment, clean and accurately measure again, and repeat the above steps three times to calculate the average wear rate. The calculation formula of the wear rate is as follows:

[0051] The oxidation experiment method is as follows: Place the specimens of the same shape and specification of the examples and comparative examples at room temperature and an air humidity of 40%-50%, and record the oxidation color of the specimen surface after 30 days. If there is only a tiny oxidation color on the specimen surface, it is called "extremely little oxidation"; if the oxidation color area is about 5%-25%, it is called "less oxidation"; if the oxidation color area is 25%-50%, it is called "more oxidation"; if the oxidation color area is greater than 50%, it is called "severe oxidation".

[0052] The test results are shown in Table 2:

[0053] From the test results, it can be seen that compared with Example 1, Comparative Example 1 did not add iron and boron, and its conductivity was close to that of Example 1, but its hardness decreased significantly and its oxidation resistance was poor; compared with Example 2, Comparative Example 2 did not add iron, resulting in a significant decrease in oxidation resistance; compared with Example 3, Comparative Example 3 lacked the addition of boron, so the Ni-Fe-B composite structure of the example was not formed. In the thicker coating, the lack of boron's supplementary effect on the coating gaps led to a decrease in microhardness and poor oxidation resistance; compared with Example 1, Comparative Example 4 added too much iron and boron, resulting in a significant decrease in conductivity; compared with Example 6, in the application of the electronic packaging housing, in the thinner coating of Comparative Example 5, its hardness and wear resistance did not meet the actual requirements due to the lack of iron and boron.

[0054] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, not to limit them; Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements on some or all of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Ni-Fe-B functional coating, characterized in that: In the Ni-Fe-B functional coating, by atomic percentage, it includes 1-10 at% of B, 1-5 at% of Fe, and the balance is Ni.

2. A contact with a surface-deposited Ni-Fe-B functional coating, characterized in that: It includes a base contact material, and the Ni-Fe-B functional coating as described in claim 1 is deposited on the surface of the base contact material.

3. The contact with a surface-deposited Ni-Fe-B functional coating according to claim 2, characterized in that: The thickness of the Ni-Fe-B functional coating is 1-50 μm.

4. The contact with a surface-deposited Ni-Fe-B functional coating according to claim 2, wherein: The base contact material includes one or more of copper alloy, pure copper, and silver.

5. The contact with a surface-deposited Ni-Fe-B functional coating according to claim 4, characterized in that: The copper alloy is composed of Cu and one or more of diamond, graphene, graphite, lanthanum, cerium, ytterbium, samarium, zirconium, silver, aluminum, iron, chromium, niobium, tin, zinc, tungsten, molybdenum, vanadium, indium, tellurium.

6. The contact with a surface-deposited Ni-Fe-B functional coating according to claim 5, characterized in that: In the copper alloy, by mass percentage, Cu accounts for 80-99.9%.

7. An electronic packaging housing with a surface-deposited Ni-Fe-B functional coating, characterized in that: It includes a base housing material, and the Ni-Fe-B functional coating as described in claim 1 is deposited on the surface of the base housing material.

8. An electronic packaging housing with a surface-deposited Ni-Fe-B functional coating according to claim 7, characterized in that: The thickness of the Ni-Fe-B functional coating is 1-30 μm.

9. An electronic packaging housing with a surface-deposited Ni-Fe-B functional coating according to claim 7, characterized in that: The base housing material includes one or more of aluminum silicon, aluminum silicon carbide, and aluminum silicon tungsten.

10. An electronic packaging housing with a surface-deposited Ni-Fe-B functional coating according to claim 9, characterized in that: In the aluminum silicon tungsten, by mass percentage, silicon accounts for 30-60%, tungsten accounts for 10-20%, and the balance is aluminum.

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