Contact structure with gradient-failed insulation and method of manufacturing the same

Abstract

The application relates to the field of electric contact elements, in particular to a gradient failure type insulating contact structure and a preparation method thereof. The contact comprises, from bottom to top, a ferrous base layer, a copper conductive intermediate layer and a silver alloy contact layer. The surface middle area of the copper conductive intermediate layer is recessed to form a mounting groove, the opening size of the mounting position along the contact width direction is not more than 2 / 3 of the total width of the upper surface of the copper conductive intermediate layer; the copper conductive intermediate layer forms current guide shoulder portions on both sides of the mounting groove; an insulating portion is arranged in the mounting groove; the silver alloy contact functional layer covers the upper surface of the intermediate layer and is electrically conductive with the current guide shoulder portions; a non-contact gap is formed between the bottom surface of the contact functional layer and the groove bottom of the mounting groove, and the electric connection with the copper conductive intermediate layer is realized only through the current guide shoulder portions on both sides, thereby forming an electrically conductive path. The application realizes active insulating failure when the contact life ends, and prevents the risk of melting adhesion and short circuit.

Description

Technical Field

[0001] This application relates to the field of electrical contact elements, and in particular to a gradient failure type insulating contact structure and its preparation method. Background Technology

[0002] In the field of power control, electrical contacts, the core component of relays and switching equipment, have long faced safety challenges related to end-of-life failure modes. Current mainstream contacts employ a two-layer structure design with a silver alloy layer and an oxygen-free copper substrate. The silver alloy provides low contact resistance and resistance to arc erosion, while the oxygen-free copper substrate provides mechanical support and heat conduction. This structure typically exhibits excellent initial conductivity under low-voltage DC conditions, with contact life generally set between 10,000 and 20,000 operating cycles. When the contacts undergo repeated arc erosion and mechanical wear under high-frequency switching conditions, the surface silver alloy layer continuously thins until it is partially depleted. At this point, the underlying oxygen-free copper substrate is exposed and comes into direct contact with the opposite contact.

[0003] This failure mechanism leads to two major safety hazards: First, when the copper substrate is exposed to high current density and high temperature environments, it is prone to melting and adhesion due to instantaneous electric arcs, posing a risk of power short circuits. Second, the irregular formation of oxides on the copper surface causes drastic fluctuations in contact resistance. Although the circuit may eventually break due to the thickening of the oxide layer, the failure process is uncontrollable and significantly delayed, making precise end-of-life protection impossible. Especially in scenarios requiring high cycle counts, traditional contact structures, lacking a failure-guided safety mechanism, have to significantly increase the thickness of the silver layer to delay the copper substrate exposure time. However, this significantly increases raw material costs and exacerbates the risk of contact cracking due to the difference in ductility of the thick silver layer.

[0004] Based on the aforementioned technical bottlenecks, there is an urgent need to develop a contact structure with a self-disconnect function within a predetermined lifespan. Summary of the Invention

[0005] The purpose of this application is to overcome at least one deficiency in the existing technology and provide a gradient failure type insulating contact structure and its preparation method. This contact structure can actively control the failure mode at the end of the contact life. By constructing a functional insulating interlayer between the silver alloy conductive layer and the oxygen-free copper substrate, the controllable conversion of the contact from the conducting state to the insulating state can be achieved. It is mainly used in scenarios with strict requirements for contact failure safety, such as high-voltage relays for electric vehicles and safety switches for industrial equipment.

[0006] To achieve the above objectives, in a first aspect, this application discloses a contact structure for gradient failure insulation, wherein the contact comprises, from bottom to top, an iron base layer, a copper conductive intermediate layer, and a silver alloy contact layer.

[0007] The copper conductive intermediate layer has a recessed mounting groove in the central area of ​​its surface. The opening size of this mounting position along the contact width direction does not exceed 2 / 3 of the total width of the upper surface of the copper conductive intermediate layer. The copper conductive intermediate layer has flow-guiding shoulders on both sides of the mounting groove. An insulating part is provided inside the mounting groove.

[0008] The silver alloy contact layer covers the upper surface of the intermediate layer and is electrically connected to the flow-guiding shoulder; a non-contact gap is formed between the bottom surface of the contact functional layer and the bottom of the mounting groove, and the electrical connection with the copper conductive intermediate layer is achieved only through the flow-guiding shoulders on both sides, forming an electrical conduction path.

[0009] As an optional technical solution, the mounting groove is a rectangular groove.

[0010] As an optional technical solution, the copper conductive intermediate layer is made of C10200 oxygen-free copper.

[0011] As an optional technical solution, the upper surface of the flow-guiding shoulder slopes downwards towards the outer edge of the copper conductive intermediate layer to form a contact slope. The contact slope increases the contact area with the silver alloy contact layer, thereby improving connection stability and reliability.

[0012] Preferably, the contact slope forms an angle of 15°-25° with the horizontal plane.

[0013] Preferably, the surface of the contact bevel is serrated.

[0014] As an optional technical solution, the upper surface of the insulating part is flush with the upper surface of the copper conductive intermediate layer.

[0015] As an optional technical solution, the upper surface of the insulating part is higher than the upper surface of the copper conductive intermediate layer, and correspondingly, the lower surface of the silver alloy contact layer is provided with an upper groove adapted to the insulating part. Preferably, the height of the upper surface of the insulating part exceeds the opening plane of the mounting groove by 0.05-0.1mm, forming an upwardly protruding insulating barrier.

[0016] As an alternative technical solution, the silver alloy contact layer is integrally covered on the surface of the copper conductive intermediate layer through a metallurgical bonding method.

[0017] Secondly, this application discloses a method for preparing a contact structure for use in gradient failure insulation, the method comprising the following steps:

[0018] Step S1: Clean the copper strip and iron strip to remove surface oil and oxides;

[0019] Step S2: Hot-roll the copper strip and iron strip into a primary composite strip with copper and iron double layers;

[0020] Step S3: Grooving is performed on the surface of the primary composite strip;

[0021] Step S4: After the primary composite strip with grooved sections is finished, it is sequentially cleaned, polished and dried before precision rolling.

[0022] Step S5: Clean the slit primary composite strip to remove surface oil and oxides, and send the insulating strip into hot rolling to combine the insulating strip with the copper-iron composite strip to form a secondary composite strip.

[0023] Step S6: Clean the surfaces of the secondary composite strip and the silver alloy strip to remove oil and oxides. Then, hot roll the silver alloy strip and the secondary composite strip together to form the tertiary composite strip.

[0024] Step S7: Perform precision rolling on the grade III composite strip and then slit it after precision rolling.

[0025] Furthermore, in step S1, the thickness of the copper strip is between 0.1 mm and 0.3 mm.

[0026] Furthermore, in step S1, the thickness of the iron strip is between 0.2 mm and 0.5 mm.

[0027] Furthermore, the cleaning in steps S1, S4, and S6 includes alkaline washing and acid washing.

[0028] Furthermore, the hot rolling temperature in steps S2, S5, and S6 is between 800 °C and 900 °C, and the rolling speed is between 1 m / min and 3 m / min.

[0029] Furthermore, in step S4, the drying temperature is between 100 °C and 120 °C, and the drying time is between 5 min and 10 min.

[0030] Further, in steps S4 and S7, finishing rolling is performed with a reduction rate of no more than 5%.

[0031] Furthermore, in step S3, an installation groove is machined using CNC milling or laser cutting. The groove depth is between 0.05 mm and 0.15 mm, the bottom of the groove is flat, and the length direction of the groove is consistent with the length direction of the strip.

[0032] Compared with the prior art, this application has at least one of the following beneficial technical effects:

[0033] 1. This application achieves active insulation failure at the end of the contact life, preventing melting and adhesion and short circuit risks;

[0034] 2. This application ensures that the failure process is controllable and reliable, and eliminates uncontrollable disconnection caused by contact resistance fluctuations.

[0035] The beneficial effects listed above are not exhaustive of all advantages. Other potential beneficial effects and detailed technical implementation methods will be further disclosed in the embodiments or other descriptive sections of this application. Attached Figure Description

[0036] A better understanding of various aspects of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. The positions, dimensions, and extents of the structures shown in the drawings, etc., do not always represent actual positions, dimensions, and extents. In the drawings:

[0037] Figure 1 This is a schematic diagram of the structure of one embodiment disclosed in this application.

[0038] Figure 2 This is a schematic diagram of another embodiment disclosed in this application.

[0039] Figure 3 This is a schematic diagram of another embodiment disclosed in this application.

[0040] Figure 4 This is a flowchart of the processing steps disclosed in this application. Detailed Implementation

[0041] The present disclosure will now be described with reference to the accompanying drawings, which illustrate several embodiments of the present disclosure. However, it should be understood that the present disclosure can be presented in many different ways and is not limited to the embodiments described below; in fact, the embodiments described below are intended to make the disclosure more complete and to fully illustrate the scope of protection of the present disclosure to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments.

[0042] It should be understood that the same reference numerals denote the same elements in all the accompanying drawings. For clarity, the dimensions of certain features may be modified in the drawings.

[0043] It should be understood that the terminology used in this specification is for describing specific embodiments only and is not intended to limit this disclosure. All terms used in this specification (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. For the sake of brevity and / or clarity, techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail; however, where appropriate, such techniques, methods, and apparatus should be considered part of this specification.

[0044] Unless otherwise specified, the singular forms “a,” “the,” and “the” used in this specification include the plural forms. The terms “comprising,” “including,” and “containing” used in this specification indicate the presence of the claimed feature but do not exclude the presence of one or more other features. The term “and / or” used in this specification includes any and all combinations of one or more of the relevant listed items.

[0045] See attached document Figures 1 to 4 Furthermore, this embodiment proposes a gradient failure type insulation contact structure, which is composed of an iron base layer 1, a copper conductive intermediate layer 2, and a silver alloy contact layer 3 stacked sequentially from bottom to top. The three are formed into a whole by hot rolling metallurgy. Under overload or aging conditions, it can fail layer by layer along a preset gradient, thereby suppressing arc propagation and extending service life. The central area of ​​the copper conductive intermediate layer 2 is milled to form an installation groove 201. The opening size of the installation groove 201 along the contact width direction is between 1 / 3 and 2 / 3 of the total width of the upper surface of the copper conductive intermediate layer. Conducting shoulders 202 are retained on both sides of the groove. An insulating part 203 is embedded in the installation groove 201. The silver alloy contact layer 3 covers the upper surface of the copper conductive intermediate layer 2 and achieves electrical conduction with the conducting shoulders 202. A non-contact gap is formed between the bottom surface of the silver alloy contact layer 3 and the bottom of the installation groove 201. The electrical connection path is established with the copper conductive intermediate layer 2 only through the conducting shoulders 202 on both sides.

[0046] More specifically, the copper conductive intermediate layer 2 is made of C10200 oxygen-free copper with an oxygen content of less than 10 ppm and a conductivity of not less than 100% IACS, in order to ensure low contact resistance and excellent thermal conductivity.

[0047] See attached document Figure 2 In some embodiments, the upper surface of the flow guide shoulder 202 slopes downward from the outer edge of the copper conductive intermediate layer toward the mounting groove to form a contact slope, and the angle between the slope and the horizontal plane is preferably 15°–25°.

[0048] See attached document Figure 3 In other embodiments, while the guide shoulder 202 forms a contact slope downwards, the surface of the contact slope is rolled to form a serrated microstructure with a tooth height of 0.01–0.03 mm and a pitch of 0.05 mm. This increases the effective contact area, reduces the shrinkage resistance, and provides mechanical locking during thermal expansion and contraction cycles to prevent the silver alloy contact layer 3 from peeling off.

[0049] Furthermore, the insulating part 203 is made of polyetheretherketone or an equivalent high heat-resistant engineering plastic, with a heat distortion temperature of not less than 250 °C and a volume resistivity of ≥1×10^16 Ω·cm.

[0050] See attached document Figure 1 and 3The upper surface of the insulating part 203 is flush with the upper surface of the copper conductive intermediate layer 2, and the silver alloy contact layer 3 directly covers and presses the insulating part 203 to form a sealed interface.

[0051] In another exemplary scenario, refer to Appendix Figure 2 The upper surface of the insulating part 203 is 0.05–0.1 mm higher than the upper surface of the copper conductive intermediate layer 2. Correspondingly, an upper groove 301 is provided on the lower surface of the silver alloy contact layer 3. The depth of the upper groove 301 is 0.01–0.02 mm higher than the protrusion height, forming an upwardly protruding insulating barrier to block creepage channels and guide arc energy to be concentrated and released into the gap.

[0052] Furthermore, the silver alloy contact layer 3 is made of AgNi10 or AgSnO2 alloy and is integrally covered on the surface of the copper conductive intermediate layer 2 by hot rolling metallurgy. The rolling temperature is 800–900 °C and the reduction rate is 3–5%. The resulting bonding interface shear strength is ≥80 MPa, ensuring that no interlayer separation occurs during long-term current carrying and interruption.

[0053] The preparation method of the contact structure is as follows: First, the copper strip and iron strip are successively subjected to alkaline washing and acid washing to remove oil and oxide scale; then, the two are hot rolled into a copper-iron double-layer primary composite strip at 800–900°C and 1–3 m / min; the installation groove is processed on the surface of the copper layer by CNC milling or laser cutting, with a groove depth of 0.05–0.15 mm and the groove length direction parallel to the length direction of the strip; then, the primary composite strip is cleaned and polished, dried with hot air at 100–120°C for 5–10 min, and then fine rolled and leveled with a reduction rate of ≤5%.

[0054] The primary composite strip after finishing rolling is fed together with the insulating strip into a hot rolling mill. Under conditions of 800–900 °C and 1–3 m / min, a secondary composite strip is formed, ensuring that the insulating part is firmly embedded in the mounting groove. Subsequently, the silver alloy strip of the secondary composite strip is simultaneously alkaline-washed and pickled to remove surface impurities. Then, under the same hot rolling parameters, the silver alloy strip is applied over the secondary composite strip to form a tertiary composite strip. Finally, the tertiary composite strip is finished rolled to the design thickness with a reduction rate of ≤5% and slit into individual contact units. Both the finishing rolling and slitting processes are carried out under nitrogen protection to prevent high-temperature oxidation.

[0055] When the contacts are under normal current-carrying conditions, current flows from the iron base layer 1 through the copper conductive intermediate layer 2 and the current-conducting shoulder 202 into the silver alloy contact layer 3. After the silver alloy contact layer 3 is consumed, the insulating part 203 is exposed, replacing the silver alloy contact layer 3 to achieve contact. By utilizing the insulating material properties of the insulating part 203, automatic disconnection is achieved.

[0056] While exemplary embodiments of this disclosure have been described, those skilled in the art will understand that various changes and modifications can be made to the exemplary embodiments of this disclosure without departing from the spirit and scope thereof. Therefore, all changes and modifications are included within the scope of protection of this disclosure as defined by the claims. This disclosure is defined by the appended claims, and equivalents of those claims are also included.

Claims

1. A contact structure for gradient failure type insulation, characterized in that, The contact consists of an iron base layer, a copper conductive intermediate layer, and a silver alloy contact layer from bottom to top. The copper conductive intermediate layer has a recessed mounting groove in the central area of ​​its surface. The opening size of this mounting position along the contact width direction does not exceed 2 / 3 of the total width of the upper surface of the copper conductive intermediate layer. The copper conductive intermediate layer has flow-guiding shoulders on both sides of the mounting groove. An insulating part is provided inside the mounting groove. The silver alloy contact layer covers the upper surface of the intermediate layer and is electrically connected to the flow-guiding shoulder; a non-contact gap is formed between the bottom surface of the silver alloy contact layer and the bottom of the mounting groove, and the electrical connection with the copper conductive intermediate layer is achieved only through the flow-guiding shoulders on both sides, thus forming an electrical conduction path.

2. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The mounting slot is a rectangular slot.

3. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The copper conductive intermediate layer is made of C10200 oxygen-free copper.

4. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The upper surface of the flow-guiding shoulder slopes downwards towards the outer edge of the copper conductive intermediate layer, forming a contact slope.

5. The contact structure for gradient failure insulation as described in claim 4, characterized in that, The contact slope forms an angle of 15°-25° with the horizontal plane.

6. The contact structure for gradient failure insulation as described in claim 4 or 5, characterized in that, The surface of the contact slope is serrated.

7. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The upper surface of the insulating part is flush with the upper surface of the copper conductive intermediate layer.

8. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The upper surface of the insulating part is higher than the upper surface of the copper conductive intermediate layer, and correspondingly, the lower surface of the silver alloy contact layer is provided with an upper groove that matches the insulating part.

9. The contact structure for gradient failure insulation as described in claim 1, characterized in that, The upper surface of the insulation part extends 0.05-0.1mm above the opening plane of the mounting groove, forming an upward-protruding insulation barrier.

10. A method for fabricating a contact structure, applied to the gradient failure type insulation contact structure of claims 1 to 9, the method comprising the following steps: Step S1: Clean the copper strip and iron strip to remove surface oil and oxides; Step S2: Hot-roll the copper strip and iron strip into a primary composite strip with copper and iron double layers; Step S3: Grooving is performed on the surface of the primary composite strip; Step S4: After the primary composite strip with grooved sections is finished, it is sequentially cleaned, polished and dried before precision rolling. Step S5: Clean the slit primary composite strip to remove surface oil and oxides, and send the insulating strip into hot rolling to combine the insulating strip with the copper-iron composite strip to form a secondary composite strip. Step S6: Clean the surfaces of the secondary composite strip and the silver alloy strip to remove oil and oxides. Then, hot roll the silver alloy strip and the secondary composite strip together to form the tertiary composite strip. Step S7: Perform precision rolling on the grade III composite strip and then slit it after precision rolling.

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