Aluminum-based copper clad laminate and its preparation method

Abstract

This invention relates to the field of circuit board technology, specifically to an aluminum-based copper-clad laminate and its preparation method. It comprises a first aluminum foil layer, a first thermally conductive adhesive layer, a second aluminum foil layer, a second thermally conductive adhesive layer, and a copper foil layer, stacked sequentially. The aluminum-based copper-clad laminate of this application adopts a double-layer aluminum composite structure. The thermally conductive adhesive layers are distributed in two layers. Because the aluminum foil layer acts as a reinforcing layer in the middle, the two thermally conductive adhesive layers are restrained by the middle aluminum foil layer when the thermally conductive adhesive flows and expands and contracts due to heat. This allows the expansion coefficients between the thermally conductive adhesive and aluminum to compensate for each other, reducing board deformation and warping caused by the thermal expansion coefficients of copper, aluminum, and insulating adhesive. This improves the flatness of the aluminum-based copper-clad laminate, achieving a flatness of ≤0.05mm in post-processing, thus solving the problem of board warping due to flatness issues.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, specifically to an aluminum-based copper-clad laminate and its preparation method. Background Technology

[0002] As is well known, aluminum-based copper clad laminate (ACL) is a plate-like material belonging to the aluminum substrate family. It is made by impregnating electronic fiberglass cloth or other reinforcing materials with resin, covering the surface with copper foil, and then hot-pressing it. It is commonly referred to as copper-clad laminate, or simply aluminum-based copper clad laminate, and can be widely used in high-power, high-heat-dissipation electronic products such as automotive ignition systems and frequency converters. As a substrate material in printed circuit board (PCB) manufacturing, ACL primarily serves to interconnect, insulate, and support PCBs. It has a significant impact on signal transmission speed, energy loss, and characteristic impedance in circuits. Therefore, the performance, quality, and stability of PCBs largely depend on ACL.

[0003] Existing aluminum-based copper clad laminates typically consist of a three-layer structure: copper foil, an insulating layer, and an aluminum plate. The insulating layer uses a fiberglass cloth impregnated with resin system and a thermally conductive pure adhesive system, which is then semi-cured at high temperature. Although this insulating sheet serves both thermal conductivity and insulation functions, its drawbacks are: due to the different coefficients of thermal expansion of copper and aluminum, the sheet deforms and warps, resulting in poor flatness, and its pressure resistance cannot be improved. Summary of the Invention

[0004] The main objective of this invention is to provide an aluminum-based copper-clad laminate and its preparation method, aiming to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention proposes an aluminum-based copper-clad laminate, comprising a first aluminum foil layer, a first thermally conductive adhesive layer, a second aluminum foil layer, a second thermally conductive adhesive layer, and a copper foil, which are stacked sequentially.

[0006] In addition, the aluminum-based copper-clad laminate of the present invention may also have the following additional technical features.

[0007] According to one embodiment of the present invention, the first thermally conductive adhesive layer and the second thermally conductive adhesive layer are formed by semi-curing thermally conductive adhesive liquid by baking at high temperature, and the first aluminum foil layer, the first thermally conductive adhesive layer, the second aluminum foil layer and the second thermally conductive adhesive layer are sequentially stacked and pressed into shape.

[0008] This invention also proposes a method for preparing aluminum-based copper-clad laminates, comprising the following steps: Prepare the thermally conductive adhesive according to the above-mentioned mass percentage of each component. Apply the prepared thermally conductive adhesive to the aluminum and copper foil carriers and bake it in a tunnel oven at different temperature ranges of 60-150 degrees Celsius to semi-cur it and form an RCC and aluminum adhesive bond. Anodizing / sulfur-free coating oxidation is performed on the surface of the 10mm aluminum plate to obtain a protective layer. An aluminum adhesive layer is then applied sequentially to the un-oxidized surface of the 10mm aluminum plate, followed by a copper adhesive layer. The plate is then placed under vacuum, with step-by-step pressure and segmented temperature increases, hot-pressed at a maximum temperature of 110-195 degrees Celsius. The temperature is then gradually reduced, finally entering cold-pressing conditions at a pressure of 5 kg / cm². 2 The plate is cooled by circulating room temperature water and the internal stress inside the plate is eliminated so that its flatness meets the corresponding requirements.

[0009] According to one embodiment of the present invention, the thickness of the copper foil layer is 0 oz-5 oz, and the thickness of the first thermally conductive adhesive layer and the second thermally conductive adhesive layer is 50-200 μm.

[0010] According to one embodiment of the present invention, the thermally conductive adhesive is made of the following components in weight percentages: Low coefficient of expansion epoxy resin 20-40%; Alumina / silicon powder 60-75%; Additives 3-10%; Furthermore, the sum of the mass percentages of all components in the thermally conductive adhesive is 100%.

[0011] According to one embodiment of the present invention, the low expansion coefficient epoxy resin is composed of epoxy resin A and epoxy resin B128, wherein the mass ratio of epoxy resin A to epoxy resin B128 is 8:2-9:1.

[0012] According to one embodiment of the present invention, the additive has a mass percentage of 3-5% and is made from the following components in mass percentage: Nitrile rubber 80%; HK560 10%; Vulcanizing agent 5%-10%; Z-ML 0.05-1%.

[0013] According to one embodiment of the present invention, the solvent ratio of the thermally conductive adhesive is 1:3:6, wherein the solvent is one or a combination of several of acetone, butanone, ethyl acetate, methyl ether, and DMF.

[0014] According to one embodiment of the present invention, the step of segmented heating includes: The heating rate is 2.0-2.5 degrees Celsius / minute to eliminate deformation and internal stress during the pressing process.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The aluminum-based copper clad laminate of this application adopts a double-layer aluminum composite structure with two layers of thermally conductive adhesive. The aluminum foil layer in the middle acts as a reinforcing layer. When the thermally conductive adhesive flows and expands and contracts due to heat, the two thermally conductive adhesive layers are restrained by the middle aluminum foil layer. This allows the expansion coefficients between the thermally conductive adhesive and aluminum to compensate for each other, reducing the deformation and warping of the board caused by the thermal expansion coefficients of copper, aluminum, and insulating adhesive. This improves the flatness of the aluminum-based copper clad laminate, enabling it to achieve a flatness of ≤0.05MM in post-processing, thus solving the problem of flatness and board warping. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Explanation of icon numbers: Figure 1 This is a cross-sectional view of an aluminum-based copper-clad laminate according to the present invention. Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0020] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] The following reference Figure 1 Aluminum-based copper-clad laminate 100 is described in some embodiments of the present invention.

[0024] Continue to refer to Figure 1 In this embodiment, an aluminum-based copper-clad laminate 100 includes a first aluminum foil layer 10, a first thermally conductive adhesive layer 11, a second aluminum foil layer 12, a second thermally conductive adhesive layer 13, and a copper foil layer 14, which are stacked sequentially.

[0025] In this embodiment, the first thermally conductive adhesive layer 11 is formed by semi-curing the thermally conductive adhesive liquid by baking at high temperature. The first aluminum foil layer 10, the first thermally conductive adhesive layer 11, the second aluminum foil layer 12, the second thermally conductive adhesive layer 13 and the copper foil layer 14 are sequentially stacked and pressed into shape.

[0026] It should be noted that the thickness of the copper foil layer 14 is HOZ-5OZ, and the thickness of the first thermally conductive adhesive layer 11 and the second thermally conductive adhesive layer 13 is 50-200UM.

[0027] In this embodiment, the thermally conductive adhesive is made from the following components in weight percentages: Low coefficient of expansion epoxy resin 20-40%; Alumina / silicon powder 60-75%; Additives 3-10%; Furthermore, the sum of the mass percentages of all components in the thermally conductive adhesive is 100%.

[0028] This thermally conductive adhesive layer uses a low-expansion resin system and does not use glass cloth, which effectively controls and reduces the overall thermal expansion change. The copper foil uses low-profile copper (roughness reduced from RA6UM to RA3UM), which effectively improves the voltage resistance of the insulation layer and reduces the difference in expansion deformation of copper due to roughness when heated.

[0029] Furthermore, the low expansion coefficient epoxy resin is composed of epoxy resin A and epoxy resin B128, wherein the mass ratio of epoxy resin A to epoxy resin B128 is 8:2-9:1.

[0030] In addition, the additive has a mass percentage of 3-5% and is made from the following components in mass percentage: Nitrile rubber 80%; HK560 10%; Vulcanizing agent 5%-10%; Z-ML 0.05-1%.

[0031] In this embodiment, the thermally conductive adhesive uses a solvent ratio of 1:3:6, wherein the solvent is one or a combination of several of acetone, methyl ethyl ketone, ethyl acetate, dimethyl ether, and DMF. The selection of different improved solvents helps to reduce the formation of pores during the evaporation of the adhesive, thereby improving the pressure resistance of the subsequent insulation layer. By controlling the GT time using baking temperature and time, sufficient time is allowed during the pressing process to compensate for defects in the insulation layer, thus improving the pressure resistance and heat resistance of the finished product.

[0032] The first thermally conductive adhesive layer 11 and the second thermally conductive adhesive layer 13 are made of the same material. The resin used in the first thermally conductive adhesive layer 11 and the second thermally conductive adhesive layer 13 is high-TG epoxy resin to stabilize the expansion coefficient during the heating and processing.

[0033] It should be noted that, in this embodiment, the coefficient of copper expansion in the copper foil layer 14 is 23*10. -6 CM / CM℃; The coefficient of copper expansion of the first thermally conductive adhesive layer 11 and the second thermally conductive adhesive layer is 55*10. -6 CM / CM℃; The coefficient of thermal expansion of aluminum in the first aluminum foil layer 10 and the second aluminum foil layer 12 is 17.7*10. -6 At / ℃, the coefficient of thermal expansion of aluminum in aluminum-based copper clad laminate 100 is ≤23.5*10 -6 CM / CM℃.

[0034] In this embodiment, the aluminum-based copper-clad laminate can be prepared according to the following preparation method, specifically including the following steps: Prepare the thermally conductive adhesive according to the above-mentioned mass percentage of each component. Apply the prepared thermally conductive adhesive to the aluminum and copper foil carriers and bake it in a tunnel oven at different temperature ranges of 60-150 degrees Celsius to semi-cur it and form an RCC and aluminum adhesive bond. Anodizing / sulfur-free coating oxidation is performed on the surface of the 10mm aluminum plate to obtain a protective layer. An aluminum adhesive layer is then applied sequentially to the un-oxidized surface of the 10mm aluminum plate, followed by a copper adhesive layer. The plate is then placed under vacuum, with step-by-step pressure and segmented temperature increases, hot-pressed at a maximum temperature of 110-195 degrees Celsius. The temperature is then gradually reduced, finally entering cold-pressing conditions at a pressure of 5 kg / cm². 2 The plate is cooled by circulating room temperature water and the internal stress inside the plate is eliminated so that its flatness meets the corresponding requirements.

[0035] Tunnel furnace temperature: 60-80-90-100-120-140-160-165-140.

[0036] The segmented heating process includes a heating rate of 2.0-2.5 degrees Celsius per minute to eliminate deformation and internal stress during the pressing process.

[0037] The aluminum-based copper-clad laminate prepared in this embodiment is heated from 30 degrees to 140-150 degrees, and the dimensional change is 2.5-3.0%. When the aluminum-based copper-clad laminate is assembled by hammering, riveting and other processes, its fracture strength is above 670 MPa.

[0038] The aluminum-based copper clad laminate of this application adopts a double-layer aluminum composite structure with two layers of thermally conductive adhesive. The aluminum foil layer in the middle acts as a reinforcing layer. When the thermally conductive adhesive flows and expands and contracts due to heat, the two thermally conductive adhesive layers are restrained by the middle aluminum foil layer. This allows the expansion coefficients between the thermally conductive adhesive and aluminum to compensate for each other, reducing the deformation and warping of the board caused by the thermal expansion coefficients of copper, aluminum, and insulating adhesive. This improves the flatness of the aluminum-based copper clad laminate, enabling it to achieve a flatness of ≤0.05MM in post-processing, thus solving the problem of flatness and board warping.

[0039] The following four examples provide a detailed description of the aluminum-based copper-clad laminate in this embodiment: Implementation 1

[0040] The thermally conductive adhesive is made from the following components in the indicated weight percentages: 1. Low expansion coefficient epoxy resin 40% (epoxy resin A: epoxy resin B128 = 9:1). 2. Additives 5-10%; 3. Thermally conductive filler content: 50-60%; Preparation method of composite aluminum-based copper clad laminate: Prepare thermally conductive adhesive according to the above components and content ratios. Apply the prepared thermally conductive adhesive to the aluminum and copper foil carriers, and bake at different temperature ranges of 60-150 degrees Celsius to semi-cur and form RCC and aluminum-adhesive composite. Anodize / sulfur-free coating oxidation is performed on the surface of the 10 aluminum plate to obtain a protective layer on the aluminum surface. Then, cover the unoxidized surface of the 10 aluminum plate with an aluminum adhesive layer, followed by a copper adhesive layer. Place it under vacuum, apply pressure stepwise, and raise the temperature in stages. Hot press it at a maximum temperature of 110-195 degrees Celsius in stages, then lower the temperature stepwise, and finally cold press it (5KG / CM2). Cool it with room temperature water circulation and eliminate the internal stress in the plate to achieve the required flatness.

[0041] Implementation 2 The thermally conductive adhesive is made from the following components in the indicated weight percentages: 1. Low expansion coefficient epoxy resin 30% (epoxy resin A: epoxy resin B128 = 9:1). 2. Additives 5-10%; 3. Thermally conductive filler content: 60-70%; Prepare the thermally conductive adhesive according to the above components and content ratios, bake it in stages at 60-155 degrees to form semi-cured thermally conductive copper foil adhesive and aluminum composite adhesive, and hot press it at a staged temperature of -110-195 degrees. Cold pressing is the same as in step 1.

[0042] Implementation 3 The thermally conductive adhesive is made from the following components in the indicated weight percentages: 1. Low expansion coefficient epoxy resin 30% (epoxy resin A: epoxy resin B128 = 8:2); 2. Additives 5-10%; 3. Thermally conductive filler content: 60-70%; Prepare the thermally conductive adhesive according to the above components and content ratios, bake it in stages at 60-160 degrees Celsius to form semi-cured thermally conductive copper foil adhesive and aluminum composite adhesive, and hot press it at a staged temperature of -110-195 degrees Celsius. Cold pressing is the same as in step 1.

[0043] Implementation 4 The hot glue is made from the following components in the indicated weight percentages: 1. Low expansion coefficient epoxy resin 22-25% (epoxy resin A: epoxy resin B128 = 8:2); 2. Additives 5-10%; 3. Thermally conductive filler 60-75%; Prepare the thermally conductive adhesive according to the above components and content ratios, bake it in stages at 60-165 degrees to form semi-cured thermally conductive copper foil adhesive and aluminum composite adhesive, and hot press it at a staged temperature of -110-195 degrees. Cold pressing is the same as in step 1.

[0044] The aluminum-based copper-clad laminates prepared in Examples 1-4 of this invention, and commercially available ordinary (PP) aluminum-based copper-clad laminates (hereinafter referred to as ordinary PP type and comparative single-sided aluminum structure aluminum-based copper-clad laminates (hereinafter referred to as ordinary type) were compared in parallel under the same experimental conditions. The measured performance parameters of each are shown in Table 1 below: Coefficient of thermal expansion (cm / cm℃) <![CDATA[25*10 -6 ]]> <![CDATA[25.5*10 -6 ]]> <![CDATA[24*10 -6 ]]> <![CDATA[23.5*10 -6 ]]> <![CDATA[35*10 -6 ]]> <![CDATA[42*10 -6 ]]> Flatness (mm) ≤0.05 ≤0.049 ≤0.5 ≤0.045 ≤0.08 ≤0.12 Thermal conductivity (W / Mk) 3.4 3.76 3.8 4.1 2.7 1.5 Heat resistance (S 288 degrees Celsius) >360 >360 >360 >360 >300 >180 Withstand voltage (kV) >7000 >7000 >7000 >7000 >5000 >4000 As can be seen from the table above, the aluminum-based copper-clad laminates prepared in Examples 1-4 of this invention have higher thermal conductivity, pressure resistance, and flatness than ordinary structures. The high thermal conductivity is related to the type and proportion of fillers in the formula. The main feature of this invention is that its pressure resistance and flatness are due to the double-layer insulating thermally conductive adhesive and the double-layer aluminum structure. Its product performance meets the high requirements and standards of production.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing an aluminum-based copper-clad laminate, characterized in that, The aluminum-based copper-clad laminate comprises a first aluminum foil layer, a first thermally conductive adhesive layer, a second aluminum foil layer, a second thermally conductive adhesive layer, and a copper foil layer, which are stacked sequentially. The copper foil layer has a thickness of 0.5 ounces to 5 ounces, and the first and second thermally conductive adhesive layers have a thickness of 50 micrometers to 200 micrometers. The first and second thermally conductive adhesive layers are formed by semi-curing thermally conductive adhesive liquid through high-temperature baking. The first aluminum foil layer, the first thermally conductive adhesive layer, the second aluminum foil layer, the second thermally conductive adhesive layer, and the copper foil are sequentially stacked and pressed into shape. The thermally conductive adhesive is composed of the following components in the indicated mass percentages: Low coefficient of expansion epoxy resin 20-40%; Alumina / silicon powder 60-75%; Additives 3-10%; Furthermore, the sum of the mass percentages of all components in the thermally conductive adhesive is 100%. The low expansion coefficient epoxy resin is composed of epoxy resin A and epoxy resin B 128, wherein the mass ratio of epoxy resin A to epoxy resin B 128 is 8:2-9:

1. The additive has a mass percentage of 3-5% and is made from the following components in the following mass percentages: Nitrile rubber 80%; HK560 10%; Vulcanizing agent 5%-10%; 2-MI 0.5-1%, The solvent used in the thermally conductive adhesive is one or a combination of several of the following: acetone, butanone, ethyl acetate, dimethyl ether, and DMF. The preparation method includes the following steps: Prepare the thermally conductive adhesive according to the above-mentioned mass percentage of each component. Apply the prepared thermally conductive adhesive to the aluminum and copper foil carriers and bake it in a tunnel oven at different temperature ranges of 60-165 degrees Celsius to semi-cur it and form an RCC and aluminum adhesive bond. The aluminum plate is anodized / sulfur-free coated to create a protective layer. An aluminum adhesive layer is then applied sequentially to the un-oxidized surface, followed by a copper adhesive layer. The plate is then placed under vacuum, with step-by-step pressure and segmented temperature increases, hot-pressed at a maximum temperature of 110-195 degrees Celsius. The temperature is then gradually reduced, finally entering cold-pressing conditions at a pressure of 5 kg / cm². 2 The plate is cooled by circulating room temperature water and the internal stress inside the plate is eliminated so that its flatness meets the corresponding requirements.

2. The preparation method according to claim 1, characterized in that, The temperature of the tunnel furnace is 60-80-90-100-120-140-160-165-140 degrees.

3. The preparation method according to claim 1, characterized in that, The segmented heating step includes: The heating rate is 2.0-2.5 degrees Celsius / minute to eliminate deformation and internal stress during the pressing process.

4. An aluminum-based copper-clad laminate, prepared by the preparation method according to any one of claims 1 to 3.

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