High-reliability layered composite soft copper bar and manufacturing method thereof

Abstract

The invention discloses a high-reliability layered composite soft copper bar and a manufacturing method thereof. The manufacturing method comprises the following steps of: welding a copper sheet and a nickel sheet through molecular diffusion welding to form an integrated composite flow guide strip; performing fine blanking forming on the composite flow guide strip; coating an insulating film on the surface of the finely punched composite current guide strip through a hot pressing process to form a hard insulating layer; and bending the composite current guide strip coated with the hard insulating layer. According to the method, the reverse technological process of forming the hard insulating layer firstly and then bending is adopted, and the hard characteristic of the insulating layer is controlled to be coordinated with the soft characteristic of the copper bar in the bending area, so that the cooperative deformation of the insulating layer and the current conductor in the bending process is realized, and the technical problem that the insulating layer in the bending area is easy to damage in the traditional process is fundamentally solved. The soft copper bar manufactured through the method has the advantages of being complete in insulating layer, high in bonding strength, excellent in conductivity and high in reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical component manufacturing, in particular to a high-reliability layered composite soft copper bar and a manufacturing method thereof. BACKGROUND

[0002] As a key conductive connection component, soft copper bars are widely used in new energy vehicles, power electronics and energy storage systems, etc. The performance reliability of the soft copper bar is directly related to the safety and stability of the entire electrical system.

[0003] At present, the industry generally adopts the process route of first completing the forming and bending of the current-carrying body, and then performing insulation coating when manufacturing a soft copper bar with an insulation layer. Typical insulation treatment methods include sleeving a heat-shrinkable tube or dipping plastic, etc. However, the traditional process route has a long-standing technical problem that has not been effectively solved: the insulation layer at the bending area is prone to breakage or damage in subsequent use. This is mainly because: the post-coated insulation layer (such as a heat-shrinkable tube) does not closely match the profile of the bent current-carrying body, and there is a microscopic gap, which is prone to breakage due to stress concentration in mechanical vibration or cold and hot cycles. More fundamentally, the insulation layer material itself does not have the mechanical properties that can coordinate with the bending deformation of the copper bar. When the soft copper bar needs to be bent and deformed at the bending area, the hard insulation layer outside cannot deform in coordination, thereby causing the bending area to become a weak point of insulation, and the risk of cracking is significantly increased.

[0004] In addition, the insulation layer and the current-carrying body are usually simply physically coated in the prior art, and the bonding force is weak, which is prone to delamination in harsh environments, further affecting the long-term reliability of the product. SUMMARY

[0005] The purpose of the present application is to provide a high-reliability layered composite soft copper bar and a manufacturing method thereof, which can avoid breakage of the insulation layer at the bending area.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A manufacturing method of a high-reliability layered composite soft copper bar, comprising the following sequential steps:

[0008] S1: welding at least one copper sheet and at least one nickel sheet by molecular diffusion welding to form an integrated composite current-carrying strip;

[0009] S2: fine blanking the composite current-carrying strip to form its accurate external profile;

[0010] S3: coating an insulation film on the surface of the fine-blanked composite current-carrying strip by a hot pressing process to form a hard insulation layer that is tightly combined with the current-carrying strip;

[0011] S4: bending the composite current-carrying strip coated with the hard insulation layer.

[0012] Wherein, the hard insulation layer has been fixedly coated before bending, and in the bending process, the hard state of the insulation layer cooperates with the soft state of the bending area of the composite busbar to realize the integrity of the insulation layer after bending.

[0013] Further, in step S1, a piece of copper foil is clamped between the upper and lower pieces of nickel foil, and a sandwich-structured composite busbar is formed by synchronous welding through one-time molecular diffusion welding.

[0014] Further, in step S3, the hot pressing process makes the Rockwell hardness of the insulation film reach HRB 80-95; and / or, the hot pressing process includes a main pressing stage under a pressure of 130-150 DEG C and 3.92x -5.88x Pa for 2-30 minutes.

[0015] Further, in step S3, a U-shaped cutout is pre-fabricated in the position of the insulation film corresponding to the welding area of the composite busbar.

[0016] Further, in step S4, the bending radius R of the bending is 2-3 times the total thickness of the composite busbar.

[0017] A high-reliability layered composite soft copper bar is prepared by the method for manufacturing the high-reliability layered composite soft copper bar.

[0018] Further, the insulation layer is a polyimide composite film formed by hot pressing and having a hardness of HRB 80-95, and is not broken in the bending area.

[0019] The beneficial effects of the present application are:

[0020] The present application overturns the traditional process logic of "bending first and then insulating", and adopts the reverse process of "first forming a hard insulation layer by hot pressing and then bending". This makes the hard insulation layer and the composite busbar first form a firm "structural integration" in a flat state by hot pressing, rather than a "external attachment" after the fact. When bending, the soft copper bar substrate can serve as a flexible carrier to guide the hard insulation layer to cooperate and uniformly deform plastically, rather than stress concentration at the bending point. This principle innovation fundamentally eliminates the root cause of insulation layer breakage at the bending point, greatly reducing the insulation layer breakage rate at the bending point.

[0021] Since the insulation layer is combined with the bus bar through a hot-pressing process instead of simple physical wrapping, a chemical bond can be formed between the two through a coupling agent, so that the shear strength of the insulation layer and the bus bar is improved, effectively avoiding the risk of delamination under vibration and cold-heat shock. At the same time, the one-time molecular diffusion welding of the "nickel sheet-copper foil-nickel sheet" is formed, realizing seamless fusion of the conductive interface, and the conductivity is improved compared with traditional partial welding; the synergistic effect of such structural integration and performance optimization makes the soft copper bar product of the present application show excellent advantages in electrical performance, mechanical performance and environmental resistance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structural schematic diagram of a high-reliability layered composite soft copper bar provided by an embodiment of the present application is provided.

[0023] Figure 2 A schematic diagram of the welding area of the high-reliability layered composite soft copper bar provided by an embodiment of the present application is provided.

[0024] Figure 3 A top view of the high-reliability layered composite soft copper bar provided by an embodiment of the present application is provided.

[0025] Figure 4 A Figure 3 A sectional view at A-A;

[0026] Figure 5 A flowchart of the manufacturing method of the high-reliability layered composite soft copper bar provided by an embodiment of the present application is provided.

[0027] MARKER DESCRIPTION:

[0028] 1, copper foil; 2, nickel sheet; 3, insulation film; DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In particular, the understanding of the term "upper" after a noun in the claims should be understood as the entire inner and outer surface of the structure referred to by the noun conforms to the definition of "upper".

[0031] The specific embodiments, structures, features, and effects provided according to the present application are described in detail as follows in combination with the drawings and preferred embodiments.

[0032] As shown in the embodiment, a manufacturing method of a high-reliability layered composite soft copper bar is provided, and the specific steps are as follows: Figures 1 to 5

[0033] Raw material preparation: copper foil: T2 red copper foil with a thickness of 0.8 mm is adopted.

[0034] Nickel sheet: pure nickel sheet with a purity of ≥99.9% and a thickness of 0.15 mm is adopted, and the surface roughness Ra is ≤0.8 μm.

[0035] Insulating film: a modified polyimide composite film with a thickness of 0.2 mm is adopted, and the formula thereof contains 30 parts of epoxy resin, 15 parts of phosphorus-containing resin, and 10 parts of aluminum hydroxide.

[0036] S1, composite flow bar forming: one piece of the above-mentioned copper foil is clamped between two pieces of nickel sheet to form a sandwich structure of "nickel sheet-copper foil-nickel sheet". The laminated structure is placed into a high-frequency diffusion welding machine (power 40 kW, frequency 60 kHz) to perform one-time molecular diffusion welding at a welding temperature of 660°C and a pressure of 0.35 MPa for 4 seconds, and the welding area is W, thereby forming an integrated composite flow bar. After welding, it is detected that the nickel-copper atomic diffusion layer has a thickness of about 6 μm, the welding area has a cavity rate of 3%, and the tensile strength is 85 MPa.

[0037] S2, fine punching: the composite flow bar obtained in step 2 is fine punched using a precision stamping die to remove burrs and form an accurate rectangular external contour meeting the design requirements.

[0038] S3, hot pressing insulation: a U-shaped cut is cut on the modified polyimide insulating film corresponding to the welding area of the two ends of the composite flow bar for future external connection using a laser. The cut depth is 1 / 2 of the insulating film thickness (i.e. 0.1 mm), the width is 1 mm wider than the welding area, and the cut edge is processed with a chamfer of 0.5 mm.

[0039] Hot pressing covering: the insulating film with the cut is covered on the upper and lower surfaces of the fine punched composite flow bar, and then placed in a hot pressing die. The die is a three-layer composite structure: the bottom layer is a stainless steel base plate, the middle layer is a heat-conducting silica gel pad (thermal conductivity 2.5 W / m·K), and the upper layer is a polytetrafluoroethylene release layer.

[0040] ​S4, bending forming: the composite flow bar coated with the hard insulating layer is placed in a special bending mold. The bending mold is integrated with an elastic limiting device (spring elastic coefficient is 80 N / mm). The bending angle is set to 90°, and the bending radius R is 2.5 times of the total thickness of the composite flow bar (1.1 mm), that is, 2.75 mm. After the bending operation, the formed soft copper bar assembly is obtained.

[0041] Product performance test: the soft copper bar assembly prepared is fully inspected, and the results are as follows:

[0042] Insulating layer integrity: magnifying glass observation shows that the insulating layer in the bending area has no visible cracks or damage.

[0043] Electrical performance: the direct current resistance is 0.098 mΩ; the power frequency withstand voltage test maintains no breakdown at 12 kV for 1 minute; the partial discharge amount is ≤4 pC.

[0044] Mechanical life: the bending life test reaches 1.1 x times.

[0045] Environmental resistance: after 96 hours of 5% NaCl solution salt spray test, the corrosion grade of the nickel layer is 9.

[0046] Comparative example

[0047] The soft copper bar of the same specification is manufactured by using the method similar to the traditional process, that is, "bending first and then sleeving the heat shrink tube". After bending, the damage rate of the heat shrink tube at the bending part is about 25%; the combination with the flow body is physical covering, and the combination force is weak; the bending life is only about 3 x times.

[0048] The comparison between the embodiment and the comparative example of the present application can be clear that the present application solves the industry problem that the insulating layer is easy to be damaged at the bending part by the process innovation of "forming the hard insulating layer first and then bending", and combines the synergistic control of the material state, which significantly improves the electrical performance, mechanical life and environmental reliability of the product.

[0049] The above-described embodiments are only preferred embodiments of the present application, and it should be pointed out that, for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and replacements can be made, and these improvements and replacements should be regarded as the protection scope of the present application.

Claims

1. A method for manufacturing a high-reliability layered composite soft copper busbar, characterized in that, Includes the following sequential steps: S1: At least one copper sheet and at least one nickel sheet are welded together by molecular diffusion welding to form an integrated composite flow guide strip; S2: The composite guide strip is precision punched to form its precise external profile; S3: The insulating film is coated onto the surface of the finely punched composite guide strip by hot pressing process to form a hard insulating layer that is tightly bonded to the guide strip; S4: Bending the composite guide strip covered with the rigid insulating layer; The rigid insulating layer is fixedly covered before bending, and during the bending process, the rigid state of the insulating layer works in conjunction with the soft state of the bending area of ​​the composite guide strip to achieve the integrity and undamaged state of the insulating layer after bending.

2. The method according to claim 1, characterized in that, In step S1, a copper foil is sandwiched between two nickel sheets and simultaneously welded to form a sandwich-structured composite flow guide strip through a single molecular diffusion welding process.

3. The method according to claim 1, characterized in that, In step S3, the hot-pressing process causes the Rockwell hardness of the insulating film to reach HRB 80-95; and / or, the hot-pressing process includes pressing at 130-150°C and 3.92× -5.88× Maintain the main pressure phase for 2-30 minutes under a pressure of Pa.

4. The method according to claim 1, characterized in that, In step S3, a clearance structure is prefabricated at the position of the insulating film corresponding to the welding area of ​​the composite flow guide strip; the clearance structure is a U-shaped cut.

5. The method according to claim 1, characterized in that, In step S4, the bending radius R of the bend is 2-3 times the total thickness of the composite guide strip.

6. A high-reliability layered composite soft copper busbar, characterized in that, It is prepared by the method according to any one of claims 1 to 5.

7. The high-reliability layered composite soft copper busbar according to claim 6, characterized in that, The insulating layer is a polyimide composite film formed by hot pressing and has a hardness of HRB 80-95, and it does not crack in the bending area.

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