Lighting device and manufacturing method thereof

Abstract

The present invention relates to a lighting device and a method for manufacturing the same, and relates to the field of LED technology. The lighting device comprises: an aluminum substrate, divided into a mirrored area and an adhesive area. The aluminum substrate in the mirrored area comprises a first aluminum layer and a silver layer plated on the surface of the first aluminum layer. The aluminum substrate in the adhesive area comprises a second aluminum layer, an adhesive layer, an insulating layer, a circuit layer, and a protective layer stacked in sequence, with the adhesive layer attached to the adhesive surface of the second aluminum layer; a chip assembly comprising a plurality of chips and metal wires. The chips are fixed to the aluminum substrate in the mirrored area, and the chips are electrically connected to the circuit layer via the metal wires; and a fluorescence conversion assembly comprising a fluorescence converter and a dam adhesive. The dam adhesive is attached to the aluminum substrate, the dam adhesive surrounds the aluminum substrate in the mirrored area to form a dam rubber ring, and the fluorescence converter is filled in the dam rubber ring, covering the chips and the metal wires. The lighting device prevents the silver layer from being sulfided or oxidized, while also having extremely high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of LEDs, and in particular to a lighting device and a preparation method thereof. Background Art

[0002] In order to obtain higher reflectivity, the circuit boards used in lighting COB-LED products generally use mirror aluminum as the bottom substrate. The mirror aluminum is silver-plated to obtain a reflectivity of ≥98%. The existing COB packaging technology generally combines mirror aluminum with multiple layers of different functional materials ( Figure 1 ) laminated and bonded to form a circuit board ( Figure 2 ), and then encapsulate the chip, fluorescent conversion material, etc. on the circuit board, such as Figure 3 As shown, a finished LED device is manufactured.

[0003] In order to achieve high brightness of COB devices, the mirror aluminum must have high reflectivity, so a silver layer must be plated on the aluminum to take advantage of the reflective effect of the silver layer. In addition, its surface is very smooth, reaching the level of a mirror.

[0004] However, because it contains silver, the substrate is very sensitive to sulfur, oxygen, halogens, etc. After long-term use, the silver layer gradually corrodes inward, causing the device to lose light or even fail. On the other hand, its smooth surface is not conducive to the adhesive layer to firmly bond with it, causing the adhesive layer to peel off and directly destroy the device structure.

[0005] In addition, if lamination defects occur during the circuit board manufacturing process, resulting in loose bonding of the adhesive layer, a capillary effect will occur at the bonding interface, which will lead to the above-mentioned failure phenomenon more quickly. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention provides a lighting device in which the area on the aluminum substrate where the chip is mounted is configured as a mirrored area, and the remaining area of ​​the aluminum substrate is configured as an adhesive area. By removing the silver layer in the adhesive area to expose the aluminum layer, the silver layer is prevented from being sulfided or oxidized. At the same time, the adhesive surface of the aluminum layer is roughened, thereby forming a high-strength mesh with the adhesive layer after lamination.

[0007] In order to achieve the above object, the present invention provides a lighting device, comprising:

[0008] An aluminum substrate, the aluminum substrate being divided into a mirror area and an adhesive area, the aluminum substrate in the mirror area comprising a first aluminum layer and a silver layer plated on a surface of the first aluminum layer, the aluminum substrate in the adhesive area comprising a second aluminum layer, an adhesive layer, an insulating layer, a circuit layer, and a protective layer stacked in sequence, the adhesive layer being attached to the adhesive surface of the second aluminum layer;

[0009] A chip assembly comprising a plurality of chips and metal wires, wherein the chips are fixed to the aluminum substrate in the mirror area, and the chips are electrically connected to the circuit layer via the metal wires; and

[0010] The fluorescence conversion component includes a fluorescence converter and a dam glue. The dam glue is attached to the aluminum substrate. The dam glue surrounds the aluminum substrate in the mirror area to form a dam rubber ring. The fluorescence converter is filled in the dam rubber ring. The fluorescence converter covers the chip and the metal wire.

[0011] During the research, the inventors found that the failure problem of COB devices in the prior art is all due to the presence of silver. The mechanism of failure of COB devices due to the presence of the silver layer is as follows: the silver layer on the mirror aluminum is spread over the entire surface. At the edge of the circuit board, the silver is exposed due to the cut end face, and the end face of the silver layer is directly in contact with the outside world. During long-term use or accelerated aging testing, the corrosion of the silver layer gradually penetrates inward, causing the device to lose light or even fail, or causing the adhesive layer to peel off, directly destroying the device structure. The silver layer on the mirror aluminum is destroyed by sulfidation to produce a loose structure ( Figure 4 ), further adsorbing water vapor, sulfur, oxygen, etc., forming a vicious cycle of acceleration. Therefore, the inventors believe that it is necessary to improve the reliability shortcomings of the parts prone to failure to prevent failure during device use or aging testing.

[0012] The inventors divide the aluminum substrate into a mirrored area and a bonding area. The mirrored area is where the chip is mounted and requires high reflectivity, while the bonding area is where the chip is not mounted and does not require high reflectivity. In conventional products, the silver layer in the bonding area is exposed to the outside world and is easily exposed to harmful substances such as water, oxygen, sulfur, and halogens, causing oxidation and sulfidation, which can lead to light decay or even failure of the lighting device. Therefore, the inventors retain the silver layer in the mirrored area and remove the silver layer in the bonding area to expose the aluminum layer. This complete removal of the easily oxidized silver layer ensures its chemical stability, thereby preventing or slowing the rate of corrosion within the light source. Furthermore, aluminum has self-limiting oxidation properties, and its oxides coat the aluminum layer surface, preventing further oxidation. This cuts off the path for water and oxygen to erode the device interior, providing excellent protection for the silver layer in the mirrored area. Furthermore, the inventors roughened the aluminum layer in the bonding area so that when the bonding layers are pressed together, the molten bonding layer can fully infiltrate the bonded aluminum layer. After bonding, the roughened three-dimensional structure of the aluminum layer forms a high-strength mesh with the adhesive. This high-strength engagement makes the device less likely to delaminate or crack when used for a long time or in harsh environments, thus having extremely high reliability.

[0013] In one embodiment, the adhesive surface has a rough structure.

[0014] In one embodiment, the mirror area is circular or square.

[0015] In one embodiment, when the mirror area is circular, the outer shape of the dam rubber ring is concentric with the mirror area.

[0016] In one embodiment, the protective layer is attached to the insulating layer and the circuit layer; the protective layer is hollowed out to expose the circuit layer to form a pad area.

[0017] In one embodiment, the circuit layer is plated with a metal film.

[0018] In one embodiment, the chips are evenly distributed on the aluminum substrate in the mirror area; the chips are LED chips, and the number of the chips is ≥1.

[0019] In one embodiment, the fluorescent converter completely covers the chip and the metal wire.

[0020] The present invention also provides a method for preparing the lighting device, comprising the following steps:

[0021] Preparation of aluminum substrate: preparing an aluminum layer on a substrate and plating silver to form an aluminum substrate;

[0022] Removing the silver layer: dividing the aluminum substrate into the mirror area and the bonding area, removing the silver layer of the aluminum substrate in the bonding area to expose the second aluminum layer;

[0023] Laminating: sequentially laminating an adhesive layer, an insulating layer, a circuit layer, and a protective layer on the second aluminum layer, and pressing them together;

[0024] Loading the chip: loading the chip onto the aluminum substrate, and connecting the circuit layer and the chip with metal wires to form an electrical connection;

[0025] Packaging: applying dam glue around the aluminum substrate in the mirror area to form a dam glue ring, filling the fluorescent converter into the dam glue ring, so that the fluorescent converter covers the chip and the metal wire.

[0026] In one embodiment, a roughening step is further included between the silver layer removal step and the stacking step: roughening the second aluminum layer so that the bonding surface of the second aluminum layer forms a rough structure.

[0027] In one embodiment, in the step of removing the silver layer, the silver layer is removed by grinding or etching; in the step of roughening, the second aluminum layer is roughened by sandblasting, grinding or corrosion.

[0028] In one embodiment, the step of removing the silver layer comprises removing the silver layer by grinding, which includes the following steps: grinding and thinning the aluminum substrate in the bonding area by mechanical grinding, wherein the thinning thickness is 1-50 μm.

[0029] By adopting the above operation, the surface of the aluminum layer can be roughened while removing the silver layer.

[0030] In one embodiment, the thinned thickness is 5-15 μm.

[0031] In one embodiment, in the step of removing the silver layer, the silver layer is removed by etching, which includes the following steps: blocking the aluminum substrate in the mirror area, spraying a corrosive liquid, and etching the aluminum substrate in the bonding area, wherein the etching depth is 1-50 μm.

[0032] By adopting the above operation, the surface of the aluminum layer can be roughened while removing the silver layer.

[0033] In one embodiment, the etching depth is 5-15 μm.

[0034] In one embodiment, the silver layer is removed by etching, and the aluminum substrate in the mirror area is shielded by an exposure and development material or a protective film.

[0035] In one embodiment, the adhesive layer is a film or an adhesive.

[0036] In one embodiment, the adhesive film is of the hot pressing and melting type.

[0037] In one embodiment, the insulating layer is made of BT material, glass fiber or ALC material.

[0038] In one embodiment, the protective layer is made of circuit ink or glass glaze.

[0039] In one embodiment, the metal plating is nickel-palladium-gold, nickel-gold or tin plating.

[0040] In one embodiment, the dam glue is made of epoxy resin.

[0041] In one embodiment, the fluorescent converter includes the following raw materials: silica gel and fluorescent powder.

[0042] In one embodiment, the LED chip includes at least one of the following chips: a blue light chip, a red light chip, a green light chip, a yellow light chip, an ultraviolet chip, or an infrared chip.

[0043] In one embodiment, the metal wire is a gold wire or a silver alloy wire.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a lighting device and its manufacturing method. In this lighting device, an aluminum substrate is divided into a mirrored area and an adhesive area. The mirrored area, where the chip is mounted, retains an intact silver layer. The adhesive area, where the chip is not mounted, removes the silver layer, exposing the aluminum layer. Through this method, the silver layer, which is susceptible to sulfidation and oxidation, is replaced by an aluminum layer with self-limiting oxidation properties. The aluminum is easily oxidized by air into a dense, high-hardness aluminum oxide film, which covers the surface of the aluminum layer, effectively protecting the aluminum inside from further oxidation and thus exhibiting excellent weather resistance. Because the silver layer is free of erosion, the adhesive layer interface does not produce a loose, water-absorbing structure, thus eliminating the path for water and oxygen to enter the device interior and effectively protecting the silver-containing area of ​​the light-emitting surface. Simultaneously, the aluminum layer is roughened, allowing the molten adhesive layer to fully infiltrate the aluminum layer when the adhesive layer is pressed together. After bonding, the microscopic three-dimensional structure of the surface forms a strong bond with the adhesive. This high-strength engagement makes the device less likely to delaminate or crack when used for a long time or in harsh environments, thus having extremely high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of the stacked structure of an aluminum substrate in a COB-LED lighting product in the prior art;

[0047] Figure 2 This is a schematic diagram of the structure of a conventional lighting COB-LED product after pressing;

[0048] Figure 3 This is a schematic diagram of the structure of a COB-LED lighting product after packaging in the prior art;

[0049] Figure 4 The loose structure is caused by the silver coating on the mirror aluminum of the existing COB-LED lighting product being destroyed by sulfidation.

[0050] Figure 5 Schematic diagram of the overall cross-section of the lighting device in Example 1;

[0051] Figure 6 Schematic diagram of the partitioning of the aluminum substrate in Example 1;

[0052] Figure 7 This is a schematic diagram of the structure of the aluminum substrates in the bonding area after lamination in Example 1;

[0053] Figure 8 Schematic diagram of the aluminum substrate stacking structure in Example 1;

[0054] Figure 9 Schematic diagram of achieving silver layer removal and roughening by mechanical polishing in Example 3;

[0055] Figure 10 Schematic diagram of achieving silver layer removal and roughening by mechanical polishing in Example 4;

[0056] Figure 11 Schematic diagram of removing the silver layer and roughening by chemical etching in Example 5.

[0057] Among them, 1100 is the mirror area, 1200 is the bonding area, 1210 is the second aluminum layer, 1211 is the rough structure, 1220 is the bonding layer, 1230 is the insulating layer, 1240 is the circuit layer, 1241 is the pad area, 1250 is the protective layer, 1260 is the mirror aluminum layer, 2100 is the chip, 2200 is the metal wire, 3100 is the fluorescent converter, 3200 is the dam glue, 4000 is the protective film, and 5000 is the chemical solution. DETAILED DESCRIPTION

[0058] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0059] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0061] source:

[0062] Unless otherwise specified, the reagents, materials, and equipment used in this example are all commercially available; and the experimental methods, unless otherwise specified, are all conventional experimental methods in the art.

[0063] Example 1

[0064] A lighting device, such as Figure 5 shown.

[0065] The lighting device includes an aluminum substrate, a chip component and a fluorescence conversion component.

[0066] Aluminum substrate, the aluminum substrate is divided into a mirror area 1100 and a bonding area 1200, such as Figure 6 As shown, the aluminum substrate of the mirror area 1100 includes a first aluminum layer and a silver layer plated on the surface of the first aluminum layer, and the aluminum substrate of the bonding area 1200 is as shown. Figure 7 As shown, it includes a second aluminum layer 1210, an adhesive layer 1220, an insulating layer 1230, a circuit layer 1240 and a protective layer 1250 stacked in sequence, wherein the adhesive layer 1220 is attached to the adhesive surface of the second aluminum layer 1210, and the adhesive surface is a rough structure 1211, as shown in FIG. Figure 8 In this embodiment, the mirror area 1100 is circular, the protective layer 1250 is attached to the insulating layer 1230 and the circuit layer 1240, the protective layer 1250 is hollowed out to expose the circuit layer 1240 to form a pad area 1241, and the surface of the circuit layer 1240 is plated with a metal film.

[0067] The chip assembly includes a plurality of chips 2100 and metal wires 2200. The chips 2100 are fixed to the aluminum substrate of the mirror area 1100. The chips 2100 are electrically connected to the circuit layer 1240 via the metal wires 2200. In this embodiment, the chips 2100 are evenly distributed on the surface of the aluminum substrate of the mirror area 1100. The chips 2100 are LED chips, and the number of chips 2100 is ≥1.

[0068] The fluorescence conversion assembly includes a fluorescence converter 3100 and a dam adhesive 3200. The dam adhesive 3200 is attached to the aluminum substrate and surrounds the aluminum substrate in the mirror area 1100 to form a dam adhesive ring. The fluorescence converter 3100 is filled within the dam adhesive ring, completely covering the chip 2100 and the metal wire 2200. In this embodiment, the dam adhesive ring is concentric with the mirror area 1100.

[0069] Example 2

[0070] A lighting device.

[0071] The difference from Example 1 is that the mirror area 1100 is a circumscribed square of the circular area of ​​the loading chip 2100 , and the rest of the structure is the same as that of Example 1.

[0072] Example 3

[0073] A method for preparing a lighting device.

[0074] The method for preparing the lighting device in Example 1 includes the following steps: preparing an aluminum substrate, removing the silver layer, roughening, stacking, loading a chip, and packaging.

[0075] Preparation of aluminum substrate: An aluminum layer is prepared on a substrate and silver is plated to form an aluminum substrate.

[0076] Removing the silver layer: the aluminum substrate is divided into the mirror area 1100 and the bonding area 1200 , and the silver layer of the aluminum substrate in the bonding area 1200 is removed to expose the second aluminum layer 1210 .

[0077] Roughening: roughening the second aluminum layer 1210 so that a rough structure 1211 is formed on the bonding surface of the second aluminum layer 1210 .

[0078] Stacking: an adhesive layer 1220 , an insulating layer 1230 , a circuit layer 1240 and a protective layer 1250 are sequentially stacked on the second aluminum layer 1210 and pressed together.

[0079] Loading the chip: Loading the chip 2100 on the aluminum substrate, and connecting the circuit layer 1240 and the chip 2100 with metal wires to form an electrical connection.

[0080] Packaging: Apply the dam glue 3200 around the aluminum substrate of the mirror area 1100 to form a dam glue ring, fill the fluorescence converter 3100 in the dam glue ring, and make the fluorescence converter 3100 cover the chip 2100 and the metal wire 2200.

[0081] In this embodiment, the aluminum substrate material fully covered with a silver-plated layer is obtained through the aluminum substrate preparation step. In the silver layer removal step, the mirror area 1100 of the chip 2100 is loaded. Figure 9 The circular area in the middle is set as the mirror area 1100, and the remaining area of ​​the aluminum substrate is the bonding area 1200 where the silver layer needs to be removed. The aluminum substrate in the bonding area 1200 is polished and thinned by mechanical polishing to a thickness of 5-15 μm. In the packaging step, the dam rubber ring and the mirror area 1100 form concentric circles.

[0082] Through the above-mentioned mechanical polishing, the silver layer in the bonding area 1200 can be removed and the exposed aluminum layer can be roughened at the same time, so that a rough structure 1211 is formed on its surface. The rough microscopic three-dimensional structure can form a high-strength meshing with the bonding layer 1220, so that the lighting device is not easy to delaminate and crack when used for a long time or in harsh environments.

[0083] Example 4

[0084] A method for preparing a lighting device.

[0085] This embodiment is a method for preparing the lighting device in embodiment 2, and has a different step from embodiment 3: through the step of preparing the aluminum substrate, an aluminum substrate material fully covered with a silver-plated layer is obtained. In the step of removing the silver layer, the circumscribed square of the circular area of ​​the loading chip 2100 is set as the mirror area 1100. Figure 10The remaining area of ​​the aluminum substrate is the bonding area 1200 where the silver layer needs to be removed. In the packaging step, the dam rubber ring and the mirror area 1100 form a concentric square.

[0086] The remaining steps are the same as those in Example 3.

[0087] Example 5

[0088] A method for preparing a lighting device.

[0089] The preparation method comprises the following steps: preparing an aluminum substrate, removing the silver layer, roughening, stacking, loading a chip, and packaging.

[0090] Preparation of aluminum substrate: An aluminum layer is prepared on a substrate and silver is plated to form an aluminum substrate.

[0091] Removing the silver layer: the aluminum substrate is divided into the mirror area 1100 and the bonding area 1200 , and the silver layer of the aluminum substrate in the bonding area 1200 is removed to expose the second aluminum layer 1210 .

[0092] Roughening: roughening the second aluminum layer 1210 so that a rough structure 1211 is formed on the bonding surface of the second aluminum layer 1210 .

[0093] Stacking: an adhesive layer 1220 , an insulating layer 1230 , a circuit layer 1240 and a protective layer 1250 are sequentially stacked on the second aluminum layer 1210 and pressed together.

[0094] Loading the chip: Loading the chip 2100 on the aluminum substrate, and connecting the circuit layer 1240 and the chip 2100 with metal wires to form an electrical connection.

[0095] Packaging: Apply the dam glue 3200 around the aluminum substrate of the mirror area 1100 to form a dam glue ring, fill the fluorescence converter 3100 in the dam glue ring, and make the fluorescence converter 3100 cover the chip 2100 and the metal wire 2200.

[0096] In this embodiment, an aluminum substrate material fully covered with a silver-plated layer is obtained through the step of preparing the aluminum substrate. In the step of removing the silver layer, the aluminum substrate is divided into a mirror area 1100 and an adhesive area 1200. The mirror area 1100 is a circular area of ​​the loading chip 2100, or a circumscribed square of the circular area of ​​the loading chip 2100. The remaining area of ​​the aluminum substrate is the adhesive area 1200. An exposure and development material or a protective film is used as a protective film 4000 to shield the mirror area 1100. A chemical solution 5000 is sprayed onto the shielded aluminum substrate to perform etching, such as Figure 11 As shown, the silver layer of the bonding area 1200 is etched to a depth of 5-15 μm.

[0097] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A lighting device, characterized in that: include: An aluminum substrate is provided, wherein the aluminum substrate is divided into a mirror surface area and an adhesive area, wherein the aluminum substrate in the mirror surface area is composed of a first aluminum layer and a silver layer plated on the surface of the first aluminum layer; the aluminum substrate in the adhesive area before the silver layer is removed is composed of a silver layer plated on the surface of a second aluminum layer and the second aluminum layer; the silver layer of the aluminum substrate in the adhesive area is removed to expose the second aluminum layer; an adhesive layer, an insulating layer, a circuit layer, and a protective layer are sequentially stacked and pressed together, so that the aluminum substrate in the adhesive area after the silver layer is removed is composed of the second aluminum layer, the adhesive layer, the insulating layer, the circuit layer, and the protective layer; the adhesive layer is attached to the adhesive surface of the second aluminum layer, and the adhesive surface has a rough structure; the protective layer is attached to the insulating layer and the circuit layer; the protective layer is provided with a hollow portion to expose the circuit layer to form a pad area; A chip assembly comprising a plurality of chips and metal wires, wherein the chips are fixed to the aluminum substrate in the mirror area, and the chips are electrically connected to the circuit layer via the metal wires; and The fluorescence conversion component includes a fluorescence converter and a dam glue. The dam glue is attached to the aluminum substrate. The dam glue surrounds the aluminum substrate in the mirror area to form a dam rubber ring. The fluorescence converter is filled in the dam rubber ring. The fluorescence converter covers the chip and the metal wire.

2. The lighting device according to claim 1, characterized in that The mirror area is circular or square.

3. The lighting device according to claim 1, characterized in that The chips are evenly distributed on the aluminum substrate in the mirror area; the chips are LED chips, and the number of the chips is ≥1.

4. The method for preparing the lighting device according to any one of claims 1 to 3, characterized in that: The following steps are involved: Preparation of aluminum substrate: preparing an aluminum layer on a substrate and plating silver to form an aluminum substrate; Silver removal: dividing the aluminum substrate into the mirror area and the bonding area, removing the silver layer from the aluminum substrate in the bonding area before the silver removal to expose the second aluminum layer; Roughening: roughening the second aluminum layer so that the bonding surface of the second aluminum layer forms a rough structure; Lamination: sequentially laminating an adhesive layer, an insulating layer, a circuit layer, and a protective layer on the second aluminum layer, and pressing them together to form an aluminum substrate in the bonding area after the silver layer is removed; Loading the chip: loading the chip onto the aluminum substrate, and connecting the circuit layer and the chip with metal wires to form an electrical connection; Packaging: applying dam glue around the aluminum substrate in the mirror area to form a dam glue ring, filling the fluorescent converter into the dam glue ring, so that the fluorescent converter covers the chip and the metal wire.

5. The preparation method according to claim 4, characterized in that In the step of removing the silver layer, the silver layer is removed by grinding or etching; in the step of roughening, the second aluminum layer is roughened by sandblasting, grinding or etching.

6. The preparation method according to claim 5, characterized in that In the step of removing the silver layer, the silver layer is removed by grinding, which includes the following steps: using mechanical grinding to thin the aluminum substrate in the bonding area before the silver layer is removed, and the thinning thickness is 1-50 μm.

7. The preparation method according to claim 5, characterized in that In the step of removing the silver layer, the silver layer is removed by etching, which includes the following steps: shielding the aluminum substrate in the mirror area, spraying corrosive liquid, and etching the aluminum substrate in the bonding area before removing the silver layer, wherein the etching depth is 1-50 μm.

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