Composite metal foil, circuit board and mobile terminal

Abstract

The invention relates to the technical field of miniaturized electronic devices, in particular to a composite metal foil, a circuit board and a mobile terminal. The invention provides a composite metal foil which comprises a base material layer and a metal layer which are sequentially arranged in a stacked mode, the side, opposite to the metal layer, of the base material layer can be stripped from a bearing film, and the binding force F1 between the metal layer and the base material layer and the stripping force F2 between the base material layer and the bearing film meet the condition that F1 / F2 is larger than or equal to 30. On one hand, the composite metal foil meeting the relational expression is easy to peel off from the bearing film, the composite metal foil can be prevented from wrinkling in the peeling process of the composite metal foil and the bearing film, on the other hand, the binding force between the base material layer and the metal layer in the composite metal foil is high, the metal layer and the base material layer are prevented from falling off, and the quality of the composite metal foil is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of miniaturized electronic devices, and in particular to a composite metal foil, a circuit board and a mobile terminal. Background Art

[0002] In order to meet the requirements of miniaturization, lightweight and high heat dissipation efficiency, ultra-thin aluminum-based materials are used instead of traditional epoxy boards for circuit boards in true wireless headphones. This not only makes them have better thermal conductivity and improves the heat dissipation efficiency of electronic components inside the headphones, but also extends service life and improves sound quality stability. At present, most of the ultra-thin aluminum-based materials used in true wireless headphones are made by bonding copper foil to a flexible aluminum substrate to form a composite material. Although mechanical strength and flexibility are taken into account, the adhesion between the metal layer and the substrate in the existing ultra-thin aluminum substrate is insufficient, and it is very easy to fall off during long-term use or in extreme environments. At the same time, as a fine material, ultra-thin aluminum base is prone to wrinkling during processing, which not only reduces the quality of the circuit board, but also affects the quality of the headphone vibration membrane.

[0003] Currently, most ultra-thin aluminum-based materials are made by repeatedly pressing metal foil and substrate. However, after multiple pressings, the bonding force between the substrate and the carrier film is relatively large, which makes it difficult to peel off the carrier film, causing wrinkles in the aluminum-based material and affecting the production quality of subsequent circuits. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of wrinkling of ultra-thin metal foil during processing in the prior art, thereby providing a composite metal foil, a circuit board and a mobile terminal.

[0005] Another technical problem to be solved by the present invention is to overcome the defect of insufficient adhesion between the metal layer and the base layer in the ultra-thin metal foil in the prior art, thereby providing a composite metal foil, a circuit board and a mobile terminal.

[0006] The present invention provides a composite metal foil, comprising a substrate layer and a metal layer stacked in sequence, wherein the side of the substrate layer facing away from the metal layer can be peeled off from a carrier film, and the bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film satisfy F1 / F2≥30. The composite metal foil satisfying the above relationship is easy to peel off from the carrier film, which can prevent the composite metal foil from wrinkling during the peeling process from the carrier film, and the bonding force between the substrate layer and the metal layer in the composite metal foil is strong, which prevents the metal layer from falling off from the substrate layer, thereby improving the quality of the composite metal foil.

[0007] In some of the embodiments, the composite metal foil combines the substrate layer and the metal layer by lamination. In the present invention, the bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film are tested by a peel strength tester in a 90° peeling manner.

[0008] In order to achieve better effects, the bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film satisfy 30≤F1 / F2≤80. Exemplarily, the bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film satisfy F1 / F2 is 30, 32, 35, 40, 45, 50, 52, 60, 64, 70, 75 and 80 or an interval consisting of any two values. The metal layer in the composite metal foil that meets the above relationship is not easy to fall off, the carrier film is easy to peel off, no wrinkles are generated, the quality is stable, and the performance is reliable when applied to circuit boards.

[0009] In order to satisfy the bonding force between the metal layer and the substrate layer in the composite metal foil and prevent the metal layer and the substrate layer from falling off automatically, the bonding force F1 between the metal layer and the substrate layer is greater than or equal to 3N / cm. Within this range, the composite metal foil does not wrinkle and has good integrity. Exemplarily, the bonding force F1 between the metal layer and the substrate layer is 3N / cm, 3.5N / cm, 3.6N / cm, 3.8N / cm, 4.0N / cm, 4.5N / cm or an interval consisting of any two values.

[0010] To ensure that the composite metal foil can be easily peeled off from the carrier film, the peeling force F2 between the carrier film layer and the substrate layer is less than or equal to 0.1 N / cm. Within this range, the composite metal foil does not wrinkle and has good integrity. Exemplarily, the peeling force F2 between the carrier film layer and the substrate layer is 0.1 N / cm, 0.08 N / cm, 0.07 N / cm, 0.05 N / cm, 0.04 N / cm, 0.01 N / cm or an interval consisting of any two values.

[0011] In some embodiments, the composite metal foil further comprises a carrier film, and the roughness Rz of the carrier film near one side of the substrate layer is 0.5 to 2 μm. Exemplarily, the roughness Rz of the carrier film near one side of the substrate layer is 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.6 μm, 1.7 μm, 2.0 μm, or an interval consisting of any two values. When the roughness of the carrier film is within this range, the bonding force between the substrate layer and the carrier film is low, and the substrate layer and the carrier film are easy to peel off.

[0012] In some embodiments, the thickness of the carrier film is 10-100 μm. Exemplarily, the thickness of the carrier film is 10 μm, 20 μm, 25 μm, 30 μm, 50 μm, 65 μm, 80 μm, 100 μm or an interval consisting of any two values.

[0013] Optionally, the material of the carrier film is polyimide (PI), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polyester or other polymer materials.

[0014] The carrier film is coated with a release agent on one side close to the substrate layer, and the release agent includes at least one of silicone oil, wax release agent, water-based release agent, liquid paraffin, silicone rubber, polytetrafluoroethylene (PTFE), and acrylic resin. Preferably, the release agent is acrylic resin. This is because, on the one hand, acrylic resin release agents can usually maintain stability under high temperature environment, are not easy to decompose or fail, and are therefore suitable for high temperature processing. On the other hand, acrylic resin release agents can effectively prevent materials from adhering to the mold surface, ensuring smooth demoulding of the product. The film they form can play an effective isolation role between the mold and the material, ensuring the surface quality of the molded product. At the same time, acrylic resin release agents are chemically stable and are not easily eroded by solvents or processing media. In use, they can be evenly covered on the mold surface by smearing or spraying, are easy to operate, and do not contain ingredients that are harmful to the environment, and are environmentally friendly and safe.

[0015] In order to improve the bonding strength between the metal layer and the substrate layer, the surface roughness Rz of the metal layer close to the substrate layer is 3 to 10 μm. Exemplarily, the surface roughness Rz of the metal layer close to the substrate layer is 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, or an interval consisting of any two values.

[0016] In order to further reduce the difficulty of peeling the composite metal foil from the carrier film, the roughness Rz of the substrate layer close to the side of the carrier film is 2 to 10 μm. Exemplarily, the roughness Rz of the substrate layer close to the side of the carrier film is 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, or an interval consisting of any two values.

[0017] In the present invention, the substrate can be formed into a substrate layer by lamination or casting. When the lamination method is adopted, the lamination equipment is a fast press, the pressure is 73 kg, the lamination time is 90 s, and the temperature is 60-185°C.

[0018] In order to reduce the bonding force between the composite metal foil and the carrier film, in the present invention, the surface tension of the carrier film on the side close to the substrate layer is 30 to 40 dynes. When the surface tension of the carrier film on the side close to the substrate layer is within this range, it is beneficial to reduce the wettability of the carrier film. When the carrier film and the composite metal foil are pressed together, specifically, when the carrier film contacts one side of the substrate layer, the bonding force after pressing can be effectively reduced. Exemplarily, the surface tension of the carrier film on the side close to the substrate layer is 30 dynes, 31 dynes, 34 dynes, 38 dynes, 40 dynes, or an interval consisting of any two values.

[0019] In order to further reduce the wettability of the carrier film and reduce the bonding force between the composite metal foil and the carrier film, in the present invention, the water drop angle of the side of the carrier film close to the substrate layer is 90° to 96°. Exemplarily, the water drop angle of the side of the carrier film close to the substrate layer is 90°, 91°, 94°, 96°, or an interval consisting of any two values.

[0020] In some embodiments, the thickness of the substrate layer is 4-5 μm. Preferably, the thickness of the substrate layer is 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, or an interval consisting of any two values.

[0021] Preferably, the substrate layer includes but is not limited to polystyrene-based thermoplastic resins, vinyl acetate-based thermoplastic resins, polyester-based thermoplastic resins, polyethylene-based thermoplastic resins, polyamide-based thermoplastic resins, rubber-based thermoplastic resins, acrylic-based thermoplastic resins, phenolic-based thermosetting resins, epoxy-based thermosetting resins, thermoplastic polyimide thermosetting resins, urethane-based thermosetting resins, melamine-based thermosetting resins, alkyd-based thermosetting resins, and alkaline phenol-formaldehyde (ABF) resins. Any resin that can satisfy the carrier function is within the requirements of this solution and is not listed in detail here. Exemplarily, the substrate layer is selected from polyimide, modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyetheretherketone, polyphenylene ether, polytetrafluoroethylene, liquid crystal polymer, polyoxadiazole, epoxy glass cloth, BT resin, and other substrate layers that can meet the performance requirements are within the scope of the present solution and are not listed in detail here.

[0022] In some embodiments, the thickness of the metal layer is 3-10 μm. The thickness of the metal layer is 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, or an interval consisting of any two values.

[0023] Preferably, the metal layer is aluminum foil, copper foil, chromium foil, zinc foil, or alloy metal foil, and the alloy metal foil contains at least one of copper, chromium and zinc. Preferably, the metal layer is aluminum foil.

[0024] In some embodiments, a bonding layer is provided between the substrate layer and the metal layer, and the thickness of the bonding layer is 1-4 μm. The thickness of the bonding layer is 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, or an interval consisting of any two values.

[0025] Preferably, the adhesive layer includes at least one of resins selected from the group consisting of vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylate, phenolic, epoxy, polyimide, urethane, melamine, alkyd, ABF and the like.

[0026] In some embodiments, a protective film layer is further disposed on the side of the metal layer away from the substrate layer or the bonding layer, and the thickness of the protective film layer is 10 to 100 μm. Exemplarily, the thickness of the protective layer is 10 μm, 20 μm, 25 μm, 30 μm, 50 μm, 65 μm, 80 μm, 100 μm, or an interval consisting of any two values.

[0027] The present invention also provides a method for preparing a composite metal foil, comprising the following steps:

[0028] The substrate layer is adhered to the surface of the carrier film through a release agent. After the substrate layer is cyclized, an adhesive material is applied to the side of the substrate layer away from the carrier film to form an adhesive layer, a metal layer is pressed on the side of the adhesive layer away from the substrate layer, and a protective film is pressed on the side of the metal layer away from the adhesive layer to form a composite metal foil.

[0029] The circuit board made of the composite metal foil has strong manufacturing reliability, good quality stability, and is convenient for transportation and storage.

[0030] The overall quality of the mobile terminal manufactured using the above circuit board is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a schematic diagram of the structure of the composite metal foil in Example 1 of the present invention;

[0033] Reference numerals:

[0034] 1-substrate layer; 2-metal layer; 3-carrier film. DETAILED DESCRIPTION

[0035] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0036] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0037] Example 1

[0038] This embodiment provides a composite metal foil, and its structural schematic diagram is as follows Figure 1 As shown, it comprises a base material layer 1 and a metal layer 2 which are stacked in sequence.

[0039] The substrate layer is made of polyimide with a thickness of 4 μm. The polyimide film is solidified on the carrier film 3.

[0040] The metal layer is aluminum foil with a thickness of 6 μm.

[0041] The dyne value of the side of the substrate layer close to the metal layer is 36, and the surface roughness Rz of the side of the metal layer close to the substrate layer is 3 μm.

[0042] The metal layer is connected to the substrate layer by lamination, and the lamination conditions are: fast lamination, lamination temperature of 185° C., pressure of 120 kg, and lamination time of 180 s.

[0043] Example 2

[0044] The other technical features of this embodiment are the same as those of Embodiment 1, except that the surface roughness Rz of the side of the metal layer close to the substrate layer is 9 μm.

[0045] Example 3

[0046] The composite metal foil of this embodiment has an adhesive layer between the substrate layer and the metal layer. Other technical features are the same as those of Example 1, except that the surface roughness Rz of the metal layer close to the substrate layer is 3 μm, the thickness of the adhesive layer is 1.5 μm, and the material is epoxy resin.

[0047] Example 4

[0048] The other technical features of this embodiment are the same as those of Embodiment 3, except that the surface roughness Rz of the metal layer close to the substrate layer is 10 μm, the thickness of the bonding layer is 3 μm, and the material is polyurethane.

[0049] Comparative Example 1

[0050] The other technical features of this embodiment are the same as those of Embodiment 1, except that the roughness Rz of the side of the metal layer close to the substrate layer is 2.5 μm.

[0051] Comparative Example 2

[0052] The other technical features of this embodiment are the same as those of Embodiment 1, except that the roughness Rz of the side of the substrate layer close to the carrier film is 1.5 μm.

[0053] Experimental example

[0054] The composite metal foil of the embodiment and the comparative example was used to press a carrier film on the aluminum foil surface. A stretching machine was used to detect the bonding force F1 between the substrate layer and the metal layer and the peeling force F2 between the substrate layer and the carrier film after the composite metal foil was pressed. At the same time, the appearance of the composite metal foil before and after the peeling force test was recorded. The experimental results are shown in Table 1 below.

[0055] Table 1 Properties of composite metal foil

[0056] Group <![CDATA[F1 / (N / cm)]]> <![CDATA[F2 / (N / cm)]]> <![CDATA[F1 / F2]]> Appearance Example 1 5.427 0.07 77.53 OK Example 2 3.6 0.08 45 OK Example 3 3.293 0.058 56.77 OK Example 4 4.171 0.084 49.65 OK Comparative Example 1 15.17 No tension \ Carrier film falls off Comparative Example 2 15.25 0.18 84.72 Wrinkles when peeling

[0057] According to the data in Table 1, when the composite metal foil provided by the present invention satisfies the condition of F1 / F2≥30, there is no wrinkling on the surface, and the metal layer and the substrate layer do not fall off automatically.

[0058] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A composite metal foil, characterized in that: It comprises a substrate layer and a metal layer stacked in sequence, the side of the substrate layer facing away from the metal layer can be peeled off from the carrier film, and the bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film satisfy F1 / F2≥30.

2. The composite metal foil according to claim 1, characterized in that: The bonding force F1 between the metal layer and the substrate layer and the peeling force F2 between the substrate layer and the carrier film satisfy 30≤F1 / F2≤80.

3. The composite metal foil according to claim 1, characterized in that: The bonding force F1 between the metal layer and the substrate layer is greater than or equal to 3N / cm.

4. The composite metal foil according to claim 3, characterized in that: The peeling force F2 between the carrier film and the substrate layer is less than or equal to 0.1 N / cm.

5. The composite metal foil according to claim 1, characterized in that: The composite metal foil further comprises a carrier film, and the roughness Rz of a side of the carrier film close to the substrate layer is 0.5 to 2 μm; and / or, The surface roughness Rz of the metal layer on a side close to the substrate layer is 3 to 10 μm.

6. The composite metal foil according to claim 5, characterized in that: The roughness Rz of the side of the substrate layer close to the carrier film is 2-10 μm.

7. The composite metal foil according to claim 6, characterized in that: The surface tension of the side of the carrier film close to the substrate layer is 30 to 40 dynes; and / or, The water drop angle of the side surface of the carrier film close to the substrate layer is 90° to 96°.

8. The composite metal foil according to any one of claims 1 to 7, characterized in that: The thickness of the substrate layer is 4 to 5 μm, and / or The thickness of the metal layer is 3 to 10 μm; and / or, An adhesive layer is provided between the substrate layer and the metal layer, and the thickness of the adhesive layer is 1 to 4 μm; and / or, A protective film layer is further provided on the side of the metal layer away from the substrate layer or the bonding layer, and the thickness of the protective film layer is 10 to 100 μm; and / or, The metal layer is an aluminum layer.

9. A circuit board, characterized in that: The circuit board comprises the composite metal foil according to any one of claims 1-8.

10. A mobile terminal, characterized in that: Including the circuit board described in claim 9.

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