A circuit board for a mini-led device and a method of manufacture

Abstract

The embodiment of the present disclosure provides a circuit board for a Mini LED device and a preparation method. The circuit board for the Mini LED device comprises: a substrate comprising an aluminum-containing metal substrate or glass; an insulating adhesive layer on the substrate; and a composite circuit layer laminated on the insulating adhesive layer, wherein the composite circuit layer comprises an aluminum sublayer close to one side of the substrate and a copper sublayer stacked on the aluminum sublayer, the volume fraction of copper in the composite circuit layer is 15-25%, the thickness of the composite circuit layer is 45-55 mu m, the thickness of the copper sublayer is 8-13 mu m, the width of the circuit in the composite circuit layer is greater than or equal to 50 mu m, and the inclination angle of the sidewall is 70-85 degrees. The circuit board has good heat dissipation performance and electrical conductivity.

Description

Technical Field

[0001] This disclosure relates to the field of printed circuit board technology, and in particular to a circuit board for Mini LED devices and its preparation method, especially to a low-cost composite circuit board for Mini LED backlighting with anodized aluminum oxide or insulating glass as the insulating carrier and copper-clad aluminum composite foil as the conductor, and its manufacturing method. Background Technology

[0002] Mini LED backlighting technology, as a next-generation high-end display solution, is rapidly penetrating the mid-to-high-end markets such as televisions, automotive displays, and gaming monitors, thanks to its superior picture quality and increasingly mature industry chain. This technology uses a large number of micron-sized LED chips as the backlight for the LCD panel and leverages local dimming technology to achieve high contrast and high dynamic range, effectively overcoming the bottlenecks of traditional OLED technology in terms of brightness, lifespan, and cost. Currently, Mini LED backlight modules have become one of the core driving forces for the development of the television industry and are gradually expanding into more diversified application scenarios such as automotive and direct-view displays.

[0003] In the manufacturing of printed circuit boards (PCBs) for Mini LED backlight modules, circuit design is a crucial factor determining their performance and reliability. Specifically, different application scenarios have specific requirements for line width and spacing: in television (TV) and automotive display fields, where the number of zones is typically between 500 and 2000, and automotive applications must meet automotive-grade reliability standards such as AEC-Q200, the line width and spacing are generally required to be no less than 150μm; while in mid-to-high-end fields such as gaming monitors with more zones (2000 to 4000), the line width and spacing requirements are even more refined, typically no less than 80μm. Although the requirements for ultra-fine circuitry are slightly lower than those for consumer electronics-grade high-density interconnect (HDI) boards, the requirements for heat dissipation performance are extremely stringent.

[0004] However, existing Mini LED backlight technology still faces challenges in meeting high heat dissipation requirements: to handle the large current required by Mini LEDs, the conductive lines in the circuit board need to have a certain cross-sectional area. But with the trend towards higher contrast and more refined zoning, the wiring density of PCBs is constantly increasing, and the space for reducing line width and spacing is limited. At this point, simply relying on traditional methods such as widening the lines or increasing the copper thickness to improve heat dissipation will not only take up valuable wiring space and increase the risk of short circuits, but also significantly increase material costs and manufacturing difficulty.

[0005] Therefore, the circuit boards and fabrication methods currently used in Mini LED devices still need improvement. Summary of the Invention

[0006] This disclosure provides a circuit board and its fabrication method for a Mini LED device. The circuit board and method employ an insulating adhesive layer and a composite circuit layer structure containing both Al and Cu. Furthermore, improvements have been made to the etching solution used in the fabrication method, resulting in a circuit board with simultaneous Cu and Al etching. The sheet resistance of the composite circuit layer is equivalent to that of a 35μm thick pure copper foil, thereby saving production costs. Compared to a pure Cu circuit board, it can save 80% of the copper usage, and the overall heat dissipation can meet the requirements of a Mini LED substrate.

[0007] In one aspect of this application, a circuit board for a Mini LED device is provided. The circuit board includes: a substrate, comprising an aluminum-containing metal substrate or glass; an insulating adhesive layer located on the substrate; and a composite circuit layer laminated onto the insulating adhesive layer. The composite circuit layer includes an aluminum sublayer near the substrate and a copper sublayer stacked on top of the aluminum sublayer. The volume fraction of copper in the composite circuit layer is 15-25%, the thickness of the composite circuit layer is 45-55 μm, and the thickness of the copper sublayer is 8-13 μm. The line width in the composite circuit layer is greater than or equal to 50 μm, and the sidewall tilt angle is 70°-85°. This circuit board exhibits good heat dissipation and conductivity.

[0008] According to an embodiment of this application, the volume resistivity of the composite circuit layer is 1.35-1.45 times that of pure copper, and the sheet resistance of the composite circuit layer is equal to that of a 35μm thick pure copper foil. Therefore, by slightly increasing the thickness of the composite circuit layer, the conductivity of an Al-Cu composite layer equivalent to that of a pure copper circuit layer can be achieved.

[0009] According to an embodiment of this application, the substrate is an aluminum-containing metal substrate, and the circuit further includes an anodic oxide layer between the substrate and the insulating adhesive layer. The anodic oxide layer is subjected to vapor sealing treatment, and the surface roughness Ra of the anodic oxide layer satisfies Ra < 0.08 μm. This improves the oxidation resistance of the anodic oxide layer.

[0010] According to embodiments of this application, the insulating adhesive layer comprises at least one of epoxy resin and optional thermally conductive filler and silane coupling agent, wherein the thermally conductive filler comprises one or more of boron nitride, aluminum nitride, and aluminum oxide.

[0011] According to an embodiment of this application, the insulating adhesive layer includes epoxy resin and the thermally conductive filler. The thickness of the insulating adhesive layer is 15-25 μm, the thermal conductivity is 1.0-2.0 W / (m·K), and the mass percentage of the thermally conductive filler in the insulating adhesive layer is 5%-20%.

[0012] According to an embodiment of this application, the silane coupling agent includes a γ-GPS silane coupling agent, and the mass percentage of the silane coupling agent is 0.1%-1% based on the mass of the insulating adhesive layer.

[0013] In another aspect of this application, a method for manufacturing the aforementioned circuit board is proposed. The method includes: cleaning a substrate; forming an insulating adhesive layer on the substrate and performing plasma activation treatment, wherein the plasma activation treatment power is 100-300W and the time is 30-60s; laminating a composite metal layer onto the insulating adhesive layer, and simultaneously etching copper and aluminum in the composite metal layer using a one-step etching solution to form a composite circuit layer. This method can easily obtain the aforementioned circuit board.

[0014] According to an embodiment of this application, the substrate includes an aluminum-containing metal substrate, which includes an aluminum or aluminum alloy substrate. The cleaning process includes: polishing the surface of the substrate to a roughness Ra < 0.1 μm; performing sulfuric acid anodizing treatment to form a 25-30 μm anodized layer; and performing saturated steam sealing treatment at 105-110°C for 20-30 min at a pressure of 0.3-0.4 MPa.

[0015] According to an embodiment of this application, the one-step etching solution comprises: 50-60 wt% phosphoric acid, 0.5-1.5 wt% nitric acid, 6-10 wt% acetic acid, 1-3 wt% sulfonic acid, 0.1-0.5 wt% amide carboxylic acid, and the balance being water. The pH value of the one-step etching solution is 1.5-2.5, and the etching performed using the one-step etching solution satisfies at least one of the following conditions: The redox potential is 800-1000mV, and the Cu / Al etching rate ratio is 1:(1.0-1.5). The size deviation of the composite circuit layer after the first etching solution treatment is <15μm, and the etching factor is ≥3; The etching is performed by spraying the one-step etching solution at a pressure of 1.5-2.0 bar and a temperature of 28-35°C. After etching, the etch depth on one side of the line is less than 2 μm.

[0016] According to an embodiment of this application, after the surface of the insulating glass substrate is subjected to plasma cleaning treatment, chemical bonding between the substrate and the interface of the insulating adhesive layer is achieved through the γ-GPS silane coupling agent in the insulating adhesive layer.

[0017] In summary, the copper consumption of this invention is reduced by approximately 80% compared to the pure copper foil solution, and the one-step etching yield reaches 89%. It is suitable for Mini backlighting scenarios with 500-4000 zones in TVs, automotive displays, and gaming monitors. The above-mentioned circuit board and its fabrication method have at least one of the following beneficial effects: The use of a composite circuit layer composed of aluminum and copper significantly reduces the amount of Cu required for the circuit board. By adjusting the thickness of each sublayer in the composite circuit layer, better conductivity is achieved. Therefore, this circuit board has a strong ability to hedge against the price of Cu. The insulating adhesive layer has a good thermal conductivity, so the overall heat dissipation can meet the requirements of Mini backlight, and the amount of thermally conductive filler used is small, resulting in low cost. By replacing two stages with one-step etching, eliminating the need for alkali-resistant inks and stage switching operations, production efficiency is improved. Attached Figure Description

[0018] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments according to this disclosure and should not be construed as limiting the scope of this disclosure.

[0019] Figure 1 This is a schematic diagram of the cross-sectional structure of the aluminum-based circuit board of the present invention; Figure 2 This is a schematic cross-sectional view of the circuit board structure of the glass-based solution of the present invention.

[0020] Wherein, 1—aluminum or aluminum alloy substrate; 2—anodic oxide layer; 3—insulating adhesive layer; 4—aluminum sublayer; 5—copper sublayer; 6—composite circuit layer; 7—glass substrate. Detailed Implementation

[0021] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure, and different embodiments can be combined arbitrarily without conflict. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0022] As one aspect of this disclosure, an embodiment provides a circuit board for a Mini LED device, with reference to... Figure 1 as well as Figure 2The circuit board includes a substrate 1, which may be an aluminum-containing metal substrate, such as an aluminum or aluminum alloy substrate 1, or a glass substrate 7. An insulating adhesive layer 3 is located on the substrate, and a composite circuit layer 6 is laminated onto the insulating adhesive layer. The composite circuit layer 6 includes an aluminum sublayer 4 near the substrate and a copper sublayer 5 stacked on top of the aluminum sublayer. The volume fraction of copper in the composite circuit layer 6 is 15-25%, the thickness of the composite circuit layer is 45-55 μm, and the thickness of the copper sublayer is 8-13 μm. The line width in the composite circuit layer 6 is greater than or equal to 50 μm, and the sidewall tilt angle is 70°-85°. This circuit board has good heat dissipation performance and conductivity.

[0023] As mentioned earlier, Mini LED backlighting has high requirements for heat dissipation. Therefore, to meet the requirements of high heat dissipation and sufficient linewidth, related technologies often use pure copper as the circuit layer to ensure the current conduction capacity of the circuit layer. However, in the pure copper solution, the copper content of 35μm thick pure copper foil is 287g / ㎡, making the circuit board sensitive to copper price fluctuations. If a multi-metal layer is used to construct the circuit board, it is difficult to achieve synchronous etching due to the different selectivity of etchants for different metals, resulting in the need for multi-stage etching processes, thus leading to low yield and complicated processes. Furthermore, related technologies often use epoxy resin prepreg (PP) as the insulating layer, making it difficult to balance thermal conductivity and electrical insulation. If a composite insulating structure is used, on the one hand, the insulating layer structure becomes more complicated, and on the other hand, it is difficult to fully improve the thermal conductivity of the insulating layer.

[0024] In summary, this application employs a composite circuit layer composed of a copper sublayer and an aluminum sublayer. The copper layer is located on the outermost side as a solderable layer, and the aluminum core serves as the circuit conductor. A one-step etching solution is used to simultaneously etch both copper and aluminum, thus forming a composite circuit layer with a linewidth that meets the requirements of Mini LED circuit boards. Furthermore, the sidewall tilt angle of the circuit formed by simultaneous etching is also more reasonable, thereby maintaining the electrical performance and current carrying capacity of the circuit layer. This helps to improve the heat dissipation performance and stability of the circuit board, making the impedance characteristics of the etched circuit layer more consistent with the design. It also reduces the problem of signal transmission performance degradation caused by the mismatch between circuit impedance and design due to the deviation of the circuit layer cross-sectional shape from the design value caused by asynchronous etching.

[0025] According to embodiments of this application, the volume resistivity of the composite circuit layer is 1.35-1.45 times that of pure copper, and the sheet resistance of the composite circuit layer is equal to that of a 35μm thick pure copper foil. By designing the thickness of the aluminum sublayer and the copper sublayer, the equivalent current-carrying cross-section of the composite circuit layer can be made equal to that of a 35μm thick pure copper foil. Therefore, by slightly increasing the thickness of the composite circuit layer, the conductivity of an Al-Cu composite layer can be achieved equivalent to that of a pure copper circuit layer.

[0026] According to embodiments of this application, the substrate is an aluminum-containing metal substrate, such as an aluminum substrate or an aluminum alloy substrate. (See reference...) Figure 1 An anodic oxide layer 2 is further included between the substrate and the insulating adhesive layer 3. The anodic oxide layer has undergone vapor sealing treatment. Specifically, an aluminum oxide film layer can be first formed on the surface of the aluminum substrate using methods such as sulfuric acid anodizing. However, the aluminum oxide film layer has a porous honeycomb structure (pore size of about 10-50 nm), and these micropores will significantly reduce the insulation performance. Vapor sealing uses high-temperature and high-pressure saturated steam to expand the pore walls of the porous aluminum oxide and close the pores. At the same time, the aluminum oxide inside the pores reacts with water to generate aluminum hydroxide with a larger volume, filling and sealing the pores, thereby greatly improving the insulation and corrosion resistance of the film. As a result, the breakdown voltage of the circuit board can be significantly improved. Furthermore, the surface roughness Ra of the anodic oxide layer 2 satisfies Ra < 0.08 μm. After vapor sealing, the surface roughness of the anodic oxide insulating film can be significantly reduced. The low roughness can improve the adhesion of the subsequent insulating adhesive layer, improve the uniformity of the epoxy thickness of the bonded insulating adhesive layer, and reduce the risk of pinholes and leakage current paths.

[0027] According to embodiments of this application, the insulating adhesive layer comprises epoxy resin. The insulating adhesive layer may be composed of an epoxy-containing material, such as conventional epoxy prepreg (PP). In some embodiments, the insulating adhesive layer may further contain at least one of a thermally conductive filler and a silane coupling agent, wherein the thermally conductive filler includes one or more of boron nitride, aluminum nitride, and alumina. In some embodiments, the insulating adhesive layer used in this application does not contain glass cloth. Removing the glass cloth from the insulating adhesive layer can result in better thermal conductivity, and with the addition of thermally conductive fillers, a thinner insulating adhesive layer can achieve both insulation and protection against damage.

[0028] According to embodiments of this application, the mass percentage of thermally conductive filler in the insulating adhesive layer can be 5%-20%.

[0029] According to embodiments of this application, the silane coupling agent comprises a γ-GPS silane coupling agent. The mass percentage of the silane coupling agent is 0.1%-1% based on the mass of the insulating adhesive layer.

[0030] According to embodiments of this application, the thickness of the insulating adhesive layer is 15-25 μm, and the thermal conductivity is 1.0-2.0 W / (m·K). By adding an appropriate amount of the above-mentioned thermally conductive additive, an insulating adhesive layer with a thermal conductivity within the above range can be provided even with a relatively thin thickness.

[0031] When the substrate is aluminum alloy or aluminum substrate, the insulation performance can be improved by an anodized layer with vapor-sealed pores, and the insulation effect can be further enhanced by a thin epoxy insulating adhesive layer. The thermally conductive additives added to the insulating adhesive layer also provide some insulation. γ-GPS silane coupling agent can further mitigate the risk of pinhole leakage caused by an excessively thin insulating adhesive layer: one end of the γ-GPS silane coupling agent can be bonded to the anodized layer, and the other end can be bonded to the composite circuit layer, thereby improving the overall insulation performance of the circuit board. When the substrate is a glass substrate, the aforementioned γ-GPS silane coupling agent can also be bonded to the glass substrate, thereby improving the overall performance of the circuit board.

[0032] In another aspect, this application proposes a method for manufacturing the aforementioned circuit board. The method includes: cleaning a substrate, forming an insulating adhesive layer on the substrate, performing plasma activation treatment, laminating a composite metal layer onto the insulating adhesive layer, and simultaneously etching copper and aluminum in the composite metal layer using a one-step etching solution to form a composite circuit layer. This method can easily obtain the aforementioned circuit board.

[0033] According to embodiments of this application, the substrate includes an aluminum-containing metal substrate, which comprises an aluminum or aluminum alloy substrate. For the aluminum metal substrate, the cleaning process may include: polishing the substrate surface to a roughness Ra < 0.1 μm; performing sulfuric acid anodizing to form a 25-30 μm anodic oxide layer; and performing saturated steam sealing treatment at 105-110°C for 20-30 minutes at a pressure of 0.3-0.4 MPa. This allows for the gradual formation of the aforementioned anodic oxide layer, thereby improving the insulation performance of the circuit board. When the conditions for anodizing and steam sealing are within the above ranges, an anodic oxide layer of moderate thickness and sufficient sealing can be formed.

[0034] In some embodiments, the substrate is a glass substrate. The insulating glass substrate is one of soda-lime glass, borosilicate glass, aluminosilicate glass, and quartz glass. The insulating glass substrate itself serves as an insulating layer, and its breakdown voltage can reach greater than or equal to 1000VDC. In this case, cleaning the substrate may include plasma cleaning.

[0035] According to embodiments of this application, an insulating adhesive layer can be formed on a substrate that has undergone the above-described cleaning process. The structure of the insulating adhesive layer has been described in detail previously and will not be repeated here. According to embodiments of this application, the insulating adhesive layer may contain thermally conductive fillers and silane coupling agents. In some embodiments, after the surface of the insulating glass substrate is subjected to plasma cleaning, chemical bonding between the substrate and the insulating adhesive layer interface can be achieved through the γ-GPS silane coupling agent in the insulating adhesive layer. This improves the adhesion between the substrate and the insulating adhesive layer.

[0036] According to embodiments of this application, in order to improve the adhesion between the composite circuit layer and the insulating adhesive layer in subsequent steps, the insulating adhesive layer can be subjected to plasma activation treatment before the circuit layer is applied. Specifically, the plasma activation treatment power is 100-300W, and the time is 30-60s. This improves surface activity and enhances the adhesion between the composite circuit layer and the insulating adhesive layer in subsequent steps.

[0037] According to an embodiment of this application, a copper-aluminum composite foil can be subsequently laminated onto the surface of the treated insulating adhesive layer. The copper-aluminum composite foil includes an aluminum layer in contact with the insulating adhesive layer and a copper layer stacked on the aluminum layer. After a one-step etching process, the aforementioned composite circuit layer is formed.

[0038] In some embodiments, the copper-aluminum composite foil can be a CCV-rolled composite foil, with no nickel barrier layer between the copper layer and the aluminum core. In some embodiments, the volume percentage of copper in the copper-aluminum composite foil can be 15-25%, the total thickness is 45-55 micrometers, and the absolute thickness of the copper layer can be 8-12 micrometers. This ensures that the circuit layer formed after etching meets the aforementioned conditions. Subsequently, a one-step etching solution is used for etching, simultaneously etching both copper and aluminum to form the aforementioned composite circuit layer. Specifically, the one-step etching solution includes 50-60 wt% phosphoric acid, 0.5-1.5 wt% nitric acid, 6-10 wt% acetic acid, 1-3 wt% sulfonic acid, 0.1-0.5 wt% amide carboxylic acid, and the balance being water. The pH value of the one-step etching solution is 1.5-2.5. Therefore, based on the phosphoric acid-nitric acid main system combined with sulfonic acid buffer to inhibit aluminum over-etching, and the addition of amide carboxyl synergistic corrosion inhibition, a ternary formulation design was developed to achieve the same rate of synchronous dissolution of copper and aluminum in the same acidic bath, breaking through the etching bottleneck of copper-clad aluminum composite foil in the field of circuit boards, and thus the aforementioned composite circuit layer can be easily obtained.

[0039] According to embodiments of this application, metal etching can be performed by spraying a one-step etching solution. The oxidation-reduction potential of the etching treatment is 800-1000mV, the Cu / Al etching rate ratio is 1:(1.0-1.5), the spraying pressure is 1.5-2.0 bar, the temperature is 28-35℃, and the etching depth on one side of the line after etching is less than 2μm. In some embodiments, the dimensional deviation (CD Bias) of the formed composite circuit layer is <15μm, and the etching factor is ≥3.

[0040] The method proposed in this application will be described in detail below using specific embodiments. Operations not explicitly described in the embodiments are conventional experimental methods, and reagents used, unless otherwise specified, are commercially available conventional reagents.

[0041] Example 1 To fabricate a Mini LED circuit board for TVs / automotive applications, with 500-2000 partitions and a line width ≥150μm, follow these steps: (1) Provide aluminum substrate: 1050 pure aluminum, 4.5kg / ㎡, which is polished with 800 mesh, 1200 mesh and 2000 mesh water sandpaper in sequence, and polished with wool wheel and Al2O3 paste to Ra=0.08μm.

[0042] (2) Anodizing: using 15% H2SO4 at 22℃, 1.2A / dm 2 After 30 minutes, an oxide layer with a thickness of 27 μm was formed.

[0043] (3) Steam sealing: 0.35MPa, 108℃, 25min, after treatment the membrane breakdown voltage is 920V DC, Ra=0.06μm.

[0044] (4) Preparation of insulating adhesive layer: 15% BN and 0.5% γ-GPS are added to modified epoxy resin, coated with 20μm, and λ is 1.8W / (m·K) and cured at 120℃.

[0045] (5) Copper-clad aluminum foil: CCV rolled composite, total thickness 49μm (copper 10μm / aluminum 39μm), copper volume ratio 20%, volume resistivity 1.42× pure copper.

[0046] (6) Bonding: Plasma activation 200W×45s, hot pressing 120℃×30s.

[0047] (7) One-step etching solution (wt%): 55% phosphoric acid, 1.0% nitric acid, 8% acetic acid, 2% sulfonic acid, 0.3% amide carbole and water balance. The pH of the one-step etching solution is 2.0 and the ORP is 880mV.

[0048] (8) Etching: Spraying at 1.8 bar, 30°C, Cu etching rate 2.8 μm / min, Al etching rate 3.2 μm / min, Cu / Al = 1:1.14, resulting in CD bias = 11 μm, etching factor 3.2, and sidewall tilt angle ≈ 80°.

[0049] Performance testing: Insulation withstand voltage > 1000V DC; The thermal resistance (Rth) is 42% lower than that of a traditional aluminum substrate (aluminum substrate + 100μm epoxy PP insulation layer with glass cloth + 35μm pure copper foil); The samples were placed in a reflow oven and subjected to three reflow soldering processes at a peak temperature of 260℃. The thickness of the intermetallic compound (IMC) formed at the Cu-Al interface was <0.8μm, with no cold solder joints. The Thermal Cycle Test (TCT) achieved 1000 cycles, repeatedly switching the samples between high and low temperatures 1000 times to simulate the temperature changes experienced by the product throughout its lifespan. The resulting circuit board meets the lifespan requirements of 5-7 years for automotive applications and 3-5 years for TV applications.

[0050] Material cost breakdown (Bill of Materials, BOM): 115 (aluminum base + oxygen + sealing) + 9.7 (CCV foil) + 10 (adhesive) + 6 (lamination) = 140.7 yuan / ㎡.

[0051] Example 2 Fabricate a gaming monitor with 2000-4000 partitions and a line width ≥80μm.

[0052] The remaining operations are the same as in Example 1. The total CCV thickness is 45 μm (9 μm for copper and 36 μm for aluminum), the line width is 80 μm, the etching solution Cu / Al = 1:1.08, the CD bias is 9 μm, the etching factor is 3.5, and the yield is 89%.

[0053] Example 3 The remaining operations are the same as in Example 1, except that the copper layer in the composite foil is 13μm and the aluminum layer is 39μm, with the copper volume accounting for 25%.

[0054] Performance testing: After 3 reflows and 1000 TCT cycles, the IMC thickness is 0.5μm, resulting in better circuit board stability. However, the cost of CCV foil increases to approximately 85% of that of pure copper foil, with a BOM of 143 yuan / ㎡.

[0055] Example 4 (1) Substrate: Aluminosilicate glass substrate, the surface is treated by plasma cleaning (power 200W, time 60s), no polishing, anodizing and sealing steps are required, the glass itself is used as an insulating layer.

[0056] (2) Thin epoxy: Same as in Example 1, modified epoxy with 15% BN and 0.5% γ-GPS is used, coated to 20μm, and cured at 120℃.

[0057] (3) Copper-clad aluminum foil, bonding and one-step etching: Same as in Example 1, CCV total thickness 49μm (copper 10μm / aluminum 39μm), one-step etching solution composition and etching parameters are the same as in Example 1.

[0058] Performance testing: Insulation withstand voltage ≥1000V DC; After three reflows at 260℃, there is no delamination at the glass-epoxy interface. Because the three processes of polishing, anodizing and sealing are eliminated, the process is shortened by about 30% compared to the aluminum-based solution, making it suitable for Mini backlighting scenarios with high insulation withstand voltage requirements and moderate heat dissipation requirements.

[0059] Example 5 Steps (1)-(3) are the same as in Example 1, and the anodic aluminum oxide base treatment is the same; (4) The adhesive layer is made of traditional epoxy prepreg (PP), which is hot-pressed together with copper-clad aluminum composite foil; (5) Subsequent bonding activation and one-step etching are the same as in Example 1.

[0060] The adhesive layer material used in this solution is the same as that of ordinary aluminum substrates, which is convenient to obtain and has a lower cost. Its thermal conductivity is comparable to that of ordinary aluminum substrates, meeting the heat dissipation requirements of Mini backlights.

[0061] Comparative Example 1 An aluminum substrate is used, with 8μm aluminum oxide (sealed with boiling water), a 100μm thick semi-cured PP sheet containing glass cloth as the insulating layer, and a 35μm thick pure copper foil to form the circuit layer.

[0062] The substrate BOM is 163 yuan / ㎡, the overall λ≈2.8, forming a 150μm linewidth circuit as in Example 1, with the same current carrying capacity but the hot spot temperature is 18℃ higher than in Example 1, and the glass cloth edge delaminates after 3 reflows.

[0063] Comparative Example 2 Similar to Example 1, a two-stage etching process is performed using an etching solution: First, copper is etched using acidic copper chloride. Then, alkali-resistant ink is applied to protect the aluminum areas that do not need to be etched. Finally, NaOH is used to etch the aluminum.

[0064] The obtained circuit boards were tested and the yield was 78%. The line speed was reduced by 25% compared with Example 1, and the BOM processing section increased by 3 yuan / ㎡.

[0065] Comparative Example 3 The rest is the same as in Example 1, except that the copper layer thickness is reduced. The total thickness of the composite foil is 49 μm, the copper layer is 4.9 μm, and the copper volume accounts for 10%.

[0066] After three reflows at 260℃, the IMC of the solder pads was 2.5μm, and cold solder joints appeared after 500 TCT cycles.

[0067] Comparative Example 4 The rest is the same as in Example 1, except that the anodic oxide layer is sealed with boiling water (95-100℃, 30min).

[0068] The breakdown voltage is only 520V DC, and the leakage current increases by 3 times after 1000 hours of PCT (high voltage accelerated life test, conducted at 121℃, 100% humidity, and 2 atmospheres).

[0069] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0070] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The foregoing disclosure provides many different embodiments or examples for implementing different structures of this disclosure. To simplify this disclosure, components and arrangements of specific examples are described above. Of course, these are merely examples and are not intended to limit this disclosure. Furthermore, reference numerals and / or reference letters may be repeated in different examples of this disclosure; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0071] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this disclosure, and these should all be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A circuit board for a Mini LED device, characterized in that, include: A substrate, wherein the substrate comprises an aluminum-containing metal substrate or glass; An insulating adhesive layer is located on the substrate; A composite circuit layer is laminated onto the insulating adhesive layer. The composite circuit layer includes an aluminum sublayer near the substrate and a copper sublayer stacked on the aluminum sublayer. The volume fraction of copper in the composite circuit layer is 15-25%, the thickness of the composite circuit layer is 45-55 μm, and the thickness of the copper sublayer is 8-13 μm. The line width in the composite circuit layer is greater than or equal to 50 μm, and the inclination angle of the sidewall is 70°-85°.

2. The circuit board according to claim 1, characterized in that, The volume resistivity of the composite circuit layer is 1.35-1.45 times that of pure copper, and the sheet resistance of the composite circuit layer is equal to that of a 35μm thick pure copper foil.

3. The circuit board according to claim 1, characterized in that, The substrate is an aluminum-containing metal substrate, and the circuit further includes an anodic oxide layer between the substrate and the insulating adhesive layer. The anodic oxide layer is vapor-sealed, and the surface roughness Ra of the anodic oxide layer satisfies Ra < 0.08 μm.

4. The circuit board according to claim 1, characterized in that, The insulating adhesive layer comprises at least one of epoxy resin and optionally thermally conductive filler and silane coupling agent. The thermally conductive filler includes one or more of boron nitride, aluminum nitride, and aluminum oxide.

5. The circuit board according to claim 4, characterized in that, The insulating adhesive layer includes epoxy resin and the thermally conductive filler. The thickness of the insulating adhesive layer is 15-25 μm, the thermal conductivity is 1.0-2.0 W / (m·K), and the mass ratio of the thermally conductive filler in the insulating adhesive layer is 5%-20%.

6. The circuit board according to claim 4, characterized in that, The silane coupling agent includes γ-GPS silane coupling agent, and the mass percentage of the silane coupling agent is 0.1%-1% based on the mass of the insulating adhesive layer.

7. A method for manufacturing a circuit board as described in any one of claims 1-6, characterized in that, include: Clean the substrate; An insulating adhesive layer is formed on the substrate and then subjected to plasma activation treatment. The power of the plasma activation treatment is 100-300W and the time is 30-60s. A composite metal layer is laminated onto the insulating adhesive layer, and copper and aluminum in the composite metal layer are simultaneously etched using a one-step etching solution to form a composite circuit layer.

8. The method according to claim 7, characterized in that, The substrate includes an aluminum-containing metal substrate, which includes an aluminum or aluminum alloy substrate, and the cleaning process includes: The substrate surface is polished to a roughness Ra < 0.1 μm; Anodizing with sulfuric acid is used to form an anodic oxide layer of 25-30 μm. Saturated steam sealing treatment is carried out at 105-110℃ for 20-30 minutes at a pressure of 0.3-0.4 MPa.

9. The method according to claim 7, characterized in that, The one-step etching solution comprises: 50-60 wt% phosphoric acid, 0.5-1.5 wt% nitric acid, 6-10 wt% acetic acid, 1-3 wt% sulfonic acid, 0.1-0.5 wt% amide carboxylic acid, and the balance being water. The pH value of the one-step etching solution is 1.5-2.5, and the etching performed using the one-step etching solution satisfies at least one of the following conditions: The redox potential is 800-1000mV, and the Cu / Al etching rate ratio is 1:(1.0-1.5). The size deviation of the composite circuit layer after the first etching solution treatment is <15μm, and the etching factor is ≥3; The etching is performed by spraying the one-step etching solution at a pressure of 1.5-2.0 bar and a temperature of 28-35°C. After etching, the etch depth on one side of the line is less than 2 μm.

10. The method according to claim 7, characterized in that, After the surface of the insulating glass substrate is treated with plasma cleaning, chemical bonding between the substrate and the interface of the insulating adhesive layer is achieved through the γ-GPS silane coupling agent in the insulating adhesive layer.

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