Composite aluminum sheet for mechanical drilling and back drilling, preparation method and application of composite aluminum sheet

Abstract

The invention provides a composite aluminum sheet for mechanical drilling and back drilling and a preparation method and application thereof, and relates to the technical field of printed circuit boards, the composite aluminum sheet comprises an aluminum foil, a binder layer and a substrate which are sequentially arranged from top to bottom, and the substrate comprises 80-85 parts of glass fiber and 15-20 parts of PP solid gum; the adhesive layer comprises the following components: 25-35 parts of 2-ethylhexyl acrylate, 4-6 parts of methyl acrylate, 7-9 parts of butyl acrylate, 44-46 parts of methylbenzene, 1-3 parts of a cross-linking agent and 2-4 parts of a viscosity loss aid. According to the composite aluminum sheet for mechanical drilling and back drilling and the preparation method of the composite aluminum sheet, the difficulty that the depths of back drilling holes are different due to the fact that metal filings on the tip of a drill point are abnormal in advance during back drilling hole production in the industry is solved, the composite aluminum sheet not only can provide precise alignment precision, but also can remove the residual metal filings on the tip of the drill point, and the service life of the back drilling holes is prolonged. Therefore, the point of the drill point is in intact contact with the aluminum foil, and the problem of different drilling depths is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board processing, in particular to a composite aluminum sheet for mechanical drilling and back drilling, a preparation method and application thereof. BACKGROUND

[0002] With the development of science and technology and the progress of society, PCBs are designed to be multifunctional, and products in the field of communication and artificial intelligence (AI) are particularly rapidly developed.

[0003] In communication products, to ensure the stability of signal transmission and meet the demand for noise reduction, the metal layer of the hole layer that does not transmit signals is removed when designing the circuit board, and only the metal hole layer that transmits signals is retained. Currently, only the back drilling function in mechanical drilling can meet this requirement. When back drilling is designed, the depth of the removed copper layer is required to be very precise due to the influence of the PCB layer spacing and the wavelength of signal transmission. When a traditional aluminum sheet is used for back drilling production, the drill bit directly drills into the aluminum sheet without a buffer layer on the surface, which is not stable in positioning and is easy to deviate. Moreover, the metal powder carried by the drill bit tip forms a conductive loop with the aluminum sheet before the drill bit tip contacts the aluminum sheet due to the influence of metal conductivity. Thus, the calculated height of the drill bit tip is not the actual height, which results in that the drilling depth is not the required depth, and the communication signal transmission is affected.

[0004] A corresponding processing aluminum sheet is developed for such products through development and testing in the factory. The new aluminum sheet design needs to consider the conductivity of the aluminum sheet while removing the metal powder on the drill bit tip to reduce the time difference caused by the metal powder and improve the drilling precision of the board. Moreover, considering the environmental impact factor, the new aluminum sheet design also needs to achieve the purpose of recycling aluminum sheet waste. SUMMARY

[0005] The purpose of the present application is to solve the problem of abnormal conduction caused by the metal powder remaining on the drill bit tip during back drilling, which causes errors in the back drilling reference and results in different drilling depths, and further leads to abnormal signal transmission. The present application also solves the problem of difficult recycling of such waste aluminum sheets. The present application provides a composite aluminum sheet for mechanical drilling and back drilling, a preparation method and process thereof, which can accurately assist the mechanical drilling machine to complete high-precision back drilling and 100% recycling of waste aluminum sheets without affecting the environment.

[0006] The technical solution adopted by the present application is as follows: A composite aluminum sheet for mechanical drilling and back drilling, wherein the composite aluminum sheet comprises, from top to bottom, an aluminum foil, an adhesive layer and a substrate.

[0007] Preferably, the composite aluminum sheet for mechanical drilling and back drilling, wherein the thickness of the aluminum foil is 10-15 um.

[0008] Preferably, the composite aluminum sheet for mechanical drilling back drilling has the following characteristics: the thickness of the substrate is 3-5 μm; and by weight, the substrate comprises 80-85 parts glass fiber and 15-20 parts PP solid adhesive.

[0009] Preferably, the composite aluminum sheet for mechanical drilling back drills comprises, by weight, the adhesive layer comprising: 25-35 parts isooctyl acrylate, 4-6 parts methyl acrylate, 7-9 parts butyl acrylate, 44-46 parts toluene, 1-3 parts crosslinking agent, and 2-4 parts anti-adhesion agent.

[0010] Preferably, the composite aluminum sheet for mechanical drilling back drills contains azobisisobutyronitrile as the crosslinking agent and a silane coupling agent as the debonding aid.

[0011] This invention also provides a method for preparing a composite aluminum sheet for mechanical drilling back drills, comprising the following steps: Step S1: Provide aluminum foil and mix 25-35 parts of isooctyl acrylate, 4-6 parts of methyl acrylate, 7-9 parts of butyl acrylate, 44-46 parts of toluene, 1-3 parts of crosslinking agent and 2-4 parts of detackifier to obtain an adhesive. Spray the adhesive onto the aluminum foil to form an adhesive layer. Step S2: Mix 80-85 parts of glass fiber and 15-20 parts of PP solid adhesive, and cure to form a substrate. Then place the substrate on the adhesive layer to form a laminated composite aluminum sheet. Step S3: The composite aluminum sheet stacked in step S2 is passed through a roller device to remove air, and during the roller rolling process, the aluminum sheet and the substrate are heated and tightly rolled into a whole by the adhesive. Finally, it is cut into the required size by an aluminum sheet cutting machine.

[0012] Preferably, in the method for preparing the composite aluminum sheet for mechanical drilling back drill, the curing temperature in step S2 is 170-190℃ and the curing time is 50-70min; the calendering temperature in step S3 is 50℃-65℃.

[0013] This invention also provides an application of a composite aluminum sheet for mechanical drilling back drills, wherein the composite aluminum sheet is applied to mechanical drilling back drills, specifically including the following steps: Step a1. Place the composite aluminum sheet on the PCB board to be drilled, with the aluminum foil on the side closest to the PCB board so that the aluminum foil overlaps with the PCB board, and place a pad on the side of the PCB board away from the aluminum foil to form a stacked structure. Place the stacked structure on the platform. Step a2: Set the corresponding drilling depth on the PCB board and drill. When the drill bit of the drilling machine contacts the substrate, it removes the metal chips on the drill bit as it drills down the substrate. The drill bit continues to drill down. When the drill bit reaches the aluminum foil, the drill bit and the aluminum foil form a conductive circuit. The drilling machine starts to automatically calculate the current needle tip height. Step a3: The drill bit continues to drill precisely to the corresponding depth according to the set drilling depth and the current needle tip height, and the drilling ends; Step S4: Lift the drill bit and move it to the next hole. Repeat steps S1-S3 to continue mechanical drilling.

[0014] Preferably, in the application of the composite aluminum sheet for mechanical drilling back drilling, in step S3 after drilling is completed, the distance between the drill bit and the pad is t=TbH, where T is the distance between the top surface of the aluminum foil and the bottom surface of the pad, b is the thickness of the aluminum foil, and H is the set drilling depth.

[0015] Advantages of this invention: (1) The composite aluminum sheet for mechanical drilling back drilling and its preparation method of the present invention solves the problem of uneven back drilling depth caused by the abnormality of metal chips on the drill bit tip conducting electricity in advance during back drilling production in the industry. The composite aluminum sheet of the present invention can not only provide accurate alignment, but also remove residual metal chips on the drill bit tip, thereby ensuring good contact between the drill bit tip and the aluminum foil and reducing the problem of uneven drilling depth.

[0016] (2) The composite aluminum sheet for mechanical drilling back drilling of the present invention has the advantage of convenient high-temperature adhesive loss and debonding, which can maximize the recycling of waste aluminum sheets. The new composite aluminum sheet for back drilling forms a complete process flow from design to processing, use and recycling, which solves the processing difficulties in back drilling technology production, and maximizes benefits while protecting the environment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the composite aluminum sheet used for mechanical drilling back drilling according to the present invention.

[0018] Figure 2 This is a schematic diagram of the composite aluminum sheet for mechanical drilling back drills of the present invention applied to mechanical drilling back drills.

[0019] Figure 3 This is a schematic diagram of the structure when the drill bit of the present invention travels to the aluminum foil.

[0020] Figure 4 This is a schematic diagram of the drill bit of the present invention drilling to the corresponding depth. Detailed Implementation

[0021] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0022] Example 1 like Figure 1 A composite aluminum sheet for mechanical drilling back drilling, wherein: the composite aluminum sheet 1 includes: aluminum foil 1-1, adhesive layer 1-2, and substrate 1-3 arranged sequentially from top to bottom.

[0023] The aluminum foil 1-1 has a thickness of 10µm; the substrate 1-3 has a thickness of 3µm; by weight, the substrate 1-3 comprises 80 parts glass fiber and 20 parts PP solid adhesive, the PP solid adhesive being manufactured by Nan Ya Plastics - Formosa Plastics Group Co., Ltd., and the model number being 1080pp.

[0024] By weight, adhesive layer 1-2 comprises the following components: 25 parts isooctyl acrylate, 4 parts methyl acrylate, 7 parts butyl acrylate, 44 parts toluene, 1 part azobisisobutyronitrile and 2 parts loss-of-tack agent.

[0025] The tack-loss aid is a silane coupling agent, which can be one of A151 (vinyltriethoxysilane), A171 (vinyltrimethoxysilane), and A172 (vinyltri(β-methoxyethoxy)silane). In this embodiment, the silane coupling agent is A151.

[0026] The preparation method of this embodiment includes the following steps: Step S1: Provide aluminum foil 1-1, and mix 25 parts of isooctyl acrylate, 4 parts of methyl acrylate, 7 parts of butyl acrylate, 44 parts of toluene, 1 part of azobisisobutyronitrile and 2 parts of A151 to obtain an adhesive. Spray the adhesive onto the aluminum foil 1-1 to form an adhesive layer 1-2. Step S2: Mix 80 parts of glass fiber and 20 parts of PP solid adhesive, and cure to form substrate 1-3. The curing temperature is 180℃ and the curing time is 60min. Then place substrate 1-3 on adhesive layer 1-2 to form a laminated composite aluminum sheet. Step S3: The stacked composite aluminum sheets are passed through a roller device to remove air, and the aluminum sheets and substrate are heated during the rolling process and tightly rolled into a whole by an adhesive. The rolling temperature is 60°C. Finally, the aluminum sheets are cut into the required size by an aluminum sheet cutting machine.

[0027] The composite aluminum sheet is a square sheet design and can be cut into different sizes and shapes according to the application scenario. The aluminum foil 1-1 is made of pure aluminum by rolling. The adhesive layer 1-2 uses a high-temperature loss-adhesion adhesive. The adhesive has micro-tackiness and can bond the aluminum sheet and the substrate into a whole. Under special high-temperature treatment, it can be quickly peeled off from the adhesive, achieving the purpose of recycling waste aluminum sheets. When the temperature exceeds 170℃, the adhesive loses its stickiness, causing the bonded materials to separate automatically.

[0028] Example 2 like Figure 1 A composite aluminum sheet for mechanical drilling back drilling, wherein: the composite aluminum sheet 1 includes: aluminum foil 1-1, adhesive layer 1-2, and substrate 1-3 arranged sequentially from top to bottom.

[0029] The aluminum foil 1-1 has a thickness of 12 μm; the substrate 1-3 has a thickness of 3-5 μm; by weight, the substrate 1-3 comprises 82 parts glass fiber and 18 parts PP solid adhesive.

[0030] By weight, adhesive layer 1-2 comprises the following components: 30 parts isooctyl acrylate, 5 parts methyl acrylate, 8 parts butyl acrylate, 45 parts toluene, 2 parts azobisisobutyronitrile and 3 parts A151.

[0031] The preparation method of this embodiment includes the following steps: Step S1: Provide aluminum foil 1-1, and mix 30 parts of isooctyl acrylate, 5 parts of methyl acrylate, 8 parts of butyl acrylate, 45 parts of toluene, 2 parts of azobisisobutyronitrile and 3 parts of A151 to obtain an adhesive. Spray the adhesive onto the aluminum foil 1-1 to form an adhesive layer 1-2. Step S2: Mix 82 parts of glass fiber and 18 parts of PP solid adhesive, and cure to form substrate 1-3. The curing temperature is 180℃ and the curing time is 60min. Then place substrate 1-3 on adhesive layer 1-2 to form a laminated composite aluminum sheet. Step S3: The stacked composite aluminum sheets are passed through a roller device to remove air, and the aluminum sheets and substrate are heated during the rolling process and tightly rolled into a whole by an adhesive. The rolling temperature is 60°C. Finally, the aluminum sheets are cut into the required size by an aluminum sheet cutting machine.

[0032] Example 3 like Figure 1 A composite aluminum sheet for mechanical drilling back drilling, wherein: the composite aluminum sheet 1 includes: aluminum foil 1-1, adhesive layer 1-2, and substrate 1-3 arranged sequentially from top to bottom.

[0033] The aluminum foil 1-1 has a thickness of 15 μm; the substrate 1-3 has a thickness of 5 μm; by weight, the substrate 1-3 comprises 85 parts glass fiber and 15 parts PP solid adhesive.

[0034] By weight, adhesive layers 1-2 comprise the following components: 35 parts isooctyl acrylate, 6 parts methyl acrylate, 9 parts butyl acrylate, 46 parts toluene, 3 parts azobisisobutyronitrile and 4 parts A151.

[0035] The preparation method of this embodiment includes the following steps: Step S1: Provide aluminum foil 1-1, and mix 35 parts of isooctyl acrylate, 6 parts of methyl acrylate, 9 parts of butyl acrylate, 46 parts of toluene, 3 parts of azobisisobutyronitrile and 4 parts of A151 to obtain an adhesive. Spray the adhesive onto the aluminum foil 1-1 to form an adhesive layer 1-2. Step S2: Mix 85 parts of glass fiber and 15 parts of PP solid adhesive, and cure to form substrate 1-3. The curing temperature is 180℃ and the curing time is 60min. Then place substrate 1-3 on adhesive layer 1-2 to form a laminated composite aluminum sheet. Step S3: The stacked composite aluminum sheets are passed through a roller device to remove air, and the aluminum sheets and substrate are heated during the rolling process and tightly rolled into a whole by an adhesive. The rolling temperature is 60°C. Finally, the aluminum sheets are cut into the required size by an aluminum sheet cutting machine.

[0036] Example 4 like Figure 2 The application of composite aluminum sheets for mechanical drilling back drills: In Example 1, the composite aluminum sheet 1 is applied to mechanical drilling back drills, specifically including the following steps: Step a1. Place the composite aluminum sheet 1 on the PCB board 2 to be drilled, and set the aluminum foil 1-1 on the side close to the PCB board so that the aluminum foil 1-1 overlaps with the PCB board 2. Set the pad 3 on the side of the PCB board 2 away from the aluminum foil 1-1 to form a stacked structure. Place the stacked structure on the platform 4. Step a2: Set the corresponding drilling depth on PCB board 2 on the drilling machine and start drilling. When the drill bit 5 of the drilling machine contacts the substrate 1-3, remove the metal chips on the drill bit 5 as it drills down the substrate. The drill bit continues to drill down. When the drill bit travels to the aluminum foil 1-1, the drill bit and the aluminum foil 1-1 form a conductive circuit. The drilling machine starts to automatically calculate the current tip height. When the drill bit contacts the substrate of the back-drilled aluminum sheet, due to the relatively low hardness of the substrate, the drill bit can form an effective vertical positioning to ensure the positioning offset accuracy. Also, due to the insulation of the substrate, when the drill bit tip and the surface to be drilled have not yet formed an effective conductive area, the metal chips on the tip can be removed as it drills down the substrate, improving the subsequent conductivity accuracy. When the drill bit 5 contacts the aluminum foil layer, the drill bit tip and the aluminum sheet directly form a conductive circuit, which can accurately obtain the accurate height of the drill tip. like Figure 3 and Figure 4 Step a3: The drill bit continues to drill precisely to the corresponding depth according to the set drilling depth and the current needle tip height, and the drilling ends. After the drilling ends, the distance between the drill bit and the pad is t=TbH, where T is the distance between the top surface of the aluminum foil and the bottom surface of the pad, b is the thickness of the aluminum foil, and H is the set drilling depth. In Example 1, the thickness of aluminum foil 1-1 is 10 μm; T is 2.0 mm, H is 0.8 mm, and the distance between the drill bit and the pad is t = 2 - 0.01 - 0.8 mm = 1.19 mm; Step S4: Lift the drill bit and move it to the next hole. Repeat steps S1-S3 to continue mechanical drilling.

[0037] Due to the adhesive's tendency to lose its stickiness at high temperatures, when recycling waste composite aluminum sheets, simply place the waste composite aluminum sheets into the recycling chamber and heat the recycling chamber to 170-200℃ using a heater. At this temperature, the adhesive loses its stickiness, causing the aluminum foil 1-1 and the substrate 1-3 to separate completely. Then, the two materials can be separated and classified, allowing for separate recycling and processing of different materials.

[0038] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite aluminum sheet for mechanical drilling back drills, characterized in that: The composite aluminum sheet (1) includes: aluminum foil (1-1), adhesive layer (1-2), and substrate (1-3) arranged sequentially from top to bottom.

2. The composite aluminum sheet for mechanical drilling back drilling as described in claim 1, characterized in that: The aluminum foil (1-1) has a thickness of 10-15 μm.

3. The composite aluminum sheet for mechanical drilling back drilling as described in claim 1, characterized in that: The thickness of the substrate (1-3) is 3-5 μm; by weight, the substrate (1-3) comprises 80-85 parts of glass fiber and 15-20 parts of PP solid adhesive.

4. The composite aluminum sheet for mechanical drilling back drilling as described in claim 1, characterized in that: By weight, the adhesive layer (1-2) comprises the following components: 25-35 parts isooctyl acrylate, 4-6 parts methyl acrylate, 7-9 parts butyl acrylate, 44-46 parts toluene, 1-3 parts crosslinking agent and 2-4 parts tack-reducing agent.

5. The composite aluminum sheet for mechanical drilling back drilling as described in claim 4, characterized in that: The crosslinking agent is azobisisobutyronitrile, and the detackifier is a silane coupling agent.

6. A method for preparing a composite aluminum sheet for mechanical drilling back drills, characterized in that: Includes the following steps: Step S1: Provide aluminum foil (1-1) and mix 25-35 parts of isooctyl acrylate, 4-6 parts of methyl acrylate, 7-9 parts of butyl acrylate, 44-46 parts of toluene, 1-3 parts of crosslinking agent and 2-4 parts of detackifier to obtain an adhesive. Spray the adhesive onto the aluminum foil (1-1) to form an adhesive layer (1-2). Step S2: Mix 80-85 parts of glass fiber and 15-20 parts of PP solid adhesive, and cure to form a substrate (1-3). Then place the substrate (1-3) on the adhesive layer (1-2) to form a laminated composite aluminum sheet. Step S3: The composite aluminum sheet stacked in step S2 is passed through a roller device to remove air, and during the roller rolling process, the aluminum sheet and the substrate are heated and tightly rolled into a whole by the adhesive. Finally, it is cut into the required size by an aluminum sheet cutting machine.

7. The method for preparing the composite aluminum sheet for mechanical drilling back drill as described in claim 6, characterized in that: In step S2, the curing temperature is 170-190℃ and the curing time is 50-70 min; in step S3, the calendering temperature is 50℃-65℃.

8. An application of a composite aluminum sheet for mechanical drilling back drills, characterized in that: The composite aluminum sheet is used in mechanical drilling back drills, specifically including the following steps: Step a1. Place the composite aluminum sheet (1) on the PCB board (2) to be drilled, and set the aluminum foil (1-1) on the side close to the PCB board so that the aluminum foil (1-1) overlaps with the PCB board (2). Set the pad (3) on the side of the PCB board (2) away from the aluminum foil (1-1) to form a stacked structure. Place the stacked structure on the platform (4). Step a2: Set the corresponding drilling depth on the PCB board (2) and drill. When the drill bit of the drilling machine contacts the substrate (1-3), it removes the metal chips on the drill bit as it drills down the substrate. The drill bit continues to drill down. When the drill bit travels to the aluminum foil (1-1), the drill bit and the aluminum foil (1-1) form a conductive circuit. The drilling machine starts to automatically calculate the current needle tip height. Step a3: The drill bit continues to drill precisely to the corresponding depth according to the set drilling depth and the current needle tip height, and the drilling ends; Step S4: Lift the drill bit and move it to the next hole. Repeat steps S1-S3 to continue mechanical drilling.

9. The application of the composite aluminum sheet for mechanical drilling back drilling as described in claim 8, characterized in that: After drilling is completed in step S3, the distance between the drill bit and the pad is t=TbH, where T is the distance between the top surface of the aluminum foil and the bottom surface of the pad, b is the thickness of the aluminum foil, and H is the set drilling depth.

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