Printed circuit board of paper material

Abstract

This printed circuit board of paper material includes: a paper layer in which pores are formed to accommodate a flame-retardant filler; coating layers having the flame-retardant filler for flame-retardancy and moisture-proofing of the paper layer and formed on the upper and lower surfaces of the paper layer; through-holes formed to pass through the paper layer; wirings disposed on the upper surface or the lower surface of the paper layer; and via holes formed in side surfaces of the through holes to a predetermined thickness and formed to be electrically connected to the wirings.

Description

Printed circuit board made of paper

[0001] The present disclosure relates to a printed circuit board (PCB) made of paper material and a method for implementing a printed circuit board using a paper substrate.

[0002] A printed circuit board (PCB) is a board with circuits formed to allow electrical signals to be transmitted between electronic components, and it performs the function of attaching and connecting electronic components to each other.

[0003] Printed Circuit Boards (PCBs), a key component of all electronic devices, are constructed by combining epoxy, fiberglass, and thin copper plates. The wiring process involves etching the copper plates, which requires extensive chemical and energy-intensive manufacturing. Furthermore, the use of non-biodegradable materials (epoxy and fiberglass) during PCB disposal releases significant environmental pollutants. To address this issue, research is underway to manufacture PCBs using eco-friendly paper. Paper is a viable material for PCBs due to its environmentally friendly properties, low cost, and availability, as well as its insulating properties and excellent printability. However, paper substrates, made of cellulose, are susceptible to moisture, flame, and low rigidity for use in PCBs, necessitating further improvement.

[0004] The etching-based PCB manufacturing technology used in conventional PCB manufacturing requires more than 20 steps, resulting in lengthy process times, extensive equipment requirements, and significant material consumption and energy costs. Furthermore, the use of hazardous chemicals during the manufacturing process is a significant problem, resulting in the emission of pollutants.

[0005] Printed electronics refers to electronic circuits and electronic products created through a printing process using conductive ink on substrates such as paper, film, and plastic. Compared to conventional PCB manufacturing, printed circuit boards offer advantages such as lower costs, simplified processes, and environmental friendliness. Furthermore, using eco-friendly substrates like paper to manufacture circuits can reduce costs and environmental impacts associated with electronic waste disposal, making it an environmentally friendly technology.

[0006] In this regard, when implementing a PCB using a paper substrate, it is necessary to have flame retardant properties, moisture absorption prevention, and warping prevention through improved rigidity in order to use paper material as a PCB.

[0007] Meanwhile, Fig. 1 illustrates a PCB having a cross-sectional structure and a PCB having a double-sided structure. Referring to Fig. 1(a), an upper conductive layer (1110) may be formed on a PCB having a cross-sectional structure. Referring to Fig. 1(b), an upper conductive layer (1110) and a lower conductive layer (1120) may be formed on the upper and lower surfaces, respectively, of a PCB having a double-sided structure. The upper conductive layer (1110) and the lower conductive layer (1120) may be electrically connected by a via hole (1100v).

[0008] Meanwhile, PCBs require complex wiring configurations to properly connect electronic components. To prevent wires from crossing or overlapping within a confined space, multilayer PCBs can be used. Multilayer PCBs stack multiple substrates, arranging circuits and connecting them through via holes. Efficient PCB design requires a multilayer structure and via hole formation technology for connection.

[0009] However, when implementing such via hole formation on a paper substrate, flame retardancy, moisture absorption prevention, and warpage prevention through improved rigidity are required.

[0010] The present disclosure aims to solve the aforementioned problems and other problems. The purpose of the present disclosure is to provide a printed circuit board (PCB) made of paper and a method for fabricating a printed circuit board using a paper substrate.

[0011] The purpose of the present disclosure is to prevent warping by improving the flame retardancy, moisture absorption prevention, and rigidity of a paper substrate when implementing a PCB using the paper material as a PCB.

[0012] The purpose of this disclosure is to propose a substrate structure for forming a PCB using a paper substrate and a process for forming via holes.

[0013] In order to achieve the above or other purposes, a printed circuit board made of paper according to the present specification comprises: a paper layer having pores formed therein so as to accommodate a flame-retardant filler; and coating layers formed on upper and lower surfaces of the paper layer, the paper layer having the flame-retardant filler for flame retardancy and moisture resistance; through holes formed to penetrate the paper layer; wires arranged on the upper or lower surface of the paper layer; and via holes formed on the side surfaces of the through holes to a predetermined thickness and electrically connected to the wires. The flame-retardant filler of the coating layers can penetrate the pores of the paper layer through a pressing process under conditions of a first range of temperature and a second range of pressure, thereby improving the rigidity and flame retardancy of the paper layer.

[0014] According to an embodiment, the via hole and the wiring may be formed using a conductive paste. The viscosity of the conductive paste forming the via holes may be formed to be lower than the viscosity of the conductive paste forming the wiring.

[0015] According to an embodiment, the temperature of the first range can be formed in a range of 100°C to 200°C. The pressure of the second range can be formed in a range of 3Mpa to 10Mpa.

[0016] According to an embodiment, the coating layers may include a first coating layer disposed on the upper surface of the paper layer and a second coating layer disposed on the lower surface of the paper layer. The coating layers may include an organic or inorganic flame retardant filler in an organic resin material.

[0017] According to an embodiment, the paper layer may include a first paper layer and a second paper layer disposed below the first paper layer. The printed circuit board may further include an adhesive layer disposed between the lower surface of the first paper layer and the upper surface of the second paper layer, the adhesive layer configured to adhere the first paper layer and the second paper layer.

[0018] According to an embodiment, the adhesive layer may include an inorganic filler. Through a pressing process under the conditions of the first range of temperature and the second range of pressure, the adhesive layer may improve the rigidity and flame retardancy of the paper layers by allowing the inorganic filler to penetrate into the first paper layer and the second paper layer.

[0019] According to an embodiment, the through holes may be formed in first regions of the paper layer. The wiring may include upper wirings arranged in second regions of the upper surface of the paper layer and lower wirings arranged in second regions of the lower surface of the paper layer. The via holes may be formed to be connected to ends of the upper wirings and ends of the lower wirings.

[0020] According to an embodiment, the ends of the upper wires may be formed further inward than the ends of the paper portions separated by the through holes. The ends of the lower wires may be formed further outward so as to protrude further than the ends of the paper portions. A first diameter of a first protrusion on the upper side of the via holes connected to the ends of the upper wires may be formed larger than a second diameter of a second protrusion on the lower side of the via holes connected to the ends of the lower wires.

[0021] According to an embodiment, screen masks may be arranged on top of the upper wirings. Spacers may be arranged on bottom of the lower wirings. The via holes may be formed by adsorbing conductive pastes arranged on the screen masks onto the side surfaces of the through holes through a via filling process.

[0022] According to an embodiment, the upper wirings adjacent to the via holes can be printed to avoid the via holes, thereby preventing the conductive paste from filling into the via holes. The lower wirings can penetrate into the via holes, thereby electrically connecting the second protrusions at the bottoms of the via holes through the via filling process.

[0023] According to an embodiment, in the via filling process connecting the upper wirings and the lower wirings, the spacers may be placed on the lower wirings. The spacers may be placed on the lower porous film. As the porous film on which the spacers are placed is removed, the second protrusions connected by the via filling process may be electrically isolated.

[0024] According to an embodiment, the thickness of the paper layer is formed to be 0.3 mm or less, so that the via filling process can be performed on the side surfaces of the through holes simultaneously with the printing process of the upper wires and the lower wires.

[0025] According to another aspect of the present disclosure, a method for manufacturing a printed circuit board using paper includes: a paper layer preparation process for preparing a paper layer having pores formed therein so as to accommodate a flame-retardant filler; a coating layer formation process for providing the flame-retardant filler for flame retardancy and moisture resistance of the paper layer and forming coating layers on the upper and lower surfaces of the paper layer; and a pressing process for applying a first range of temperature and a second range of pressure to the paper substrate on which the coating layers are formed so that the flame-retardant filler of the coating layers penetrates the pores of the paper layer to improve rigidity and flame retardancy of the paper layer. The manufacturing method may further include a through-hole formation process for forming through holes so as to penetrate the paper layer; a wiring formation process for forming wirings arranged on the upper or lower surface of the paper layer; and a via-hole formation process for forming via holes formed on side surfaces of the through holes to a predetermined thickness and electrically connected to the wirings.

[0026] According to an embodiment, the via hole and the wiring may be formed with a conductive paste. The viscosity of the conductive paste forming the via hole may be formed to be lower than the viscosity of the conductive paste forming the via holes. In the pressing process, the temperature in the first range may be formed in a range of 100°C to 200°C, and the pressure in the second range may be formed in a range of 3Mpa to 10Mpa.

[0027] According to an embodiment, the coating layer forming process may include a first coating layer forming process for forming a first coating layer disposed on the upper surface of the paper layer, and a second coating layer forming process for forming a second coating layer disposed on the lower surface of the paper layer. The coating layers may include an organic or inorganic flame retardant filler in an organic resin material.

[0028] According to an embodiment, the paper layer preparation process may include a second paper layer preparation process for preparing a second paper layer having pores formed therein; an adhesive layer arrangement process for arranging an adhesive layer on an upper surface of the second paper layer; and a first paper layer arrangement process for arranging a first paper layer having pores formed therein on the adhesive layer. The adhesive layer is arranged between a lower surface of the first paper layer and an upper surface of the second paper layer to adhere the first paper layer and the second paper layer, and the adhesive layer may include an inorganic filler. In the pressing process under the conditions of the first range of temperature and the second range of pressure, the adhesive layer may allow the inorganic filler to penetrate into the first paper layer and the second paper layer, thereby improving the rigidity and flame retardancy of the paper layer.

[0029] According to an embodiment, in the through-hole forming process, the through-holes may be formed in first regions of the paper layer. The wiring forming process may include an upper wiring forming process for forming upper wirings arranged in second regions of an upper surface of the paper layer; and a lower wiring forming process for forming lower wirings arranged in second regions of a lower surface of the paper layer. In the via-hole forming process, the via-holes may be formed to be connected to ends of the upper wirings and ends of the lower wirings.

[0030] According to an embodiment, the ends of the upper wires may be formed further inward than the ends of the paper portions separated by the through holes. The ends of the lower wires may be formed further outward so as to protrude further than the ends of the paper portions. A first diameter of a first protrusion on the upper side of the via holes connected to the ends of the upper wires may be formed larger than a second diameter of a second protrusion on the lower side of the via holes connected to the ends of the lower wires.

[0031] According to an embodiment, the via hole forming process may include a screen mask arrangement process for arranging screen masks on top of the upper wirings; a space arrangement process for arranging spacers on bottom of the lower wirings; and a via filling process for forming conductive pastes arranged on the screen masks by being adsorbed onto side surfaces of the through holes. The upper wirings adjacent to the via holes may be printed to avoid the via holes, thereby preventing the conductive paste from filling into the via holes. The lower wirings may penetrate into the via holes, so that the second protrusions at the bottoms of the via holes may be electrically connected by the via filling process.

[0032] According to an embodiment, in the via filling process connecting the upper wirings and the lower wirings, the spacers may be placed on the lower wirings. The spacers may be placed on the lower porous film. The via hole forming process may further include a porous film removal process in which the second protrusions connected by the via filling process are electrically isolated as the porous film on which the spacers are placed is removed.

[0033] The technical effects of the printed circuit board made of paper and the manufacturing method thereof according to this specification are described as follows.

[0034] According to this specification, in order to use paper material as a PCB, it is possible to have flame retardant properties and moisture absorption prevention through a composite structure including a coating layer for flame retardancy / moisture resistance and an adhesive layer.

[0035] According to the present specification, the rigidity of a paper substrate can be improved by permeating an inorganic material included in a coating and adhesive material into the pores of the paper.

[0036] According to this specification, the upper / lower circuit wiring layers are formed by a printing process using a conductive paste, and when the upper / lower circuit wiring layers are connected by via holes, the shapes of the upper and lower layers are optimized so that electrical stability and mechanical stability can be implemented.

[0037] Further scope of the applicability of this specification will become apparent from the detailed description below. However, since various changes and modifications within the spirit and scope of this specification will be apparent to those skilled in the art, it should be understood that the detailed description and specific examples, such as preferred embodiments, are given by way of example only.

[0038] Figure 1 shows a PCB with a cross-sectional structure and a PCB with a double-sided structure.

[0039] Figure 2 shows the manufacturing process of a double-sided PCB.

[0040] Figure 3 shows a laminated structure of a PCB having a paper substrate.

[0041] Figure 4 shows a configuration in which temperature and pressure are applied for a composite material process of a printed circuit board having a paper layer.

[0042] Figure 5a shows a laminated structure and cross-sectional analysis photograph of a PCB having a paper layer formed through a high-temperature process.

[0043] Figure 5b shows a laminated structure and cross-sectional analysis photograph of a PCB having a paper layer formed through a high temperature and high pressure process.

[0044] Figure 6 compares the surface photographs of the paper layer of a PCB having a paper substrate and the paper layer of the PCB under various process conditions.

[0045] Figure 7 compares the stiffness of paper substrates under specific temperature and pressure conditions.

[0046] Figure 8 shows the processes of forming upper wiring, lower wiring, and via holes on both sides of a paper layer.

[0047] Figure 9 shows a via filling process for forming a via hole.

[0048] Figure 10 shows an example of a double-sided PCB manufactured using a paper substrate.

[0049] Figure 11 shows a perspective view and a partially enlarged view of a PCB having a paper substrate combined with a reinforcing substrate.

[0050] Figures 12 and 13 show a flow chart of a method for manufacturing a printed circuit board made of paper according to the present disclosure.

[0051] Figure 14 shows a schematic diagram according to an embodiment of a method for manufacturing a printed circuit board made of double-sided paper material.

[0052] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be given the same reference numbers and redundant descriptions thereof will be omitted. The suffixes "module" and "part" used for components in the following description are assigned or used interchangeably only for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of this specification.

[0053] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0054] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0055] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0056] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0057] Below, a detailed description is given of a paper-based printed circuit board and its manufacturing method according to the present disclosure. This disclosure proposes a technology for a paper-based double-sided PCB structure and manufacturing method. Specifically, the structure and manufacturing method of the paper substrate are described, as well as a technique for forming wiring and via holes on the manufactured paper substrate. In this regard, Figure 2 illustrates the manufacturing process of a double-sided PCB.

[0058] Referring to Fig. 2(a), the PCB (1000) is configured with a structure in which an upper conductive layer (1100) and a lower conductive layer (1120) made of copper foil are laminated on the upper and lower surfaces of the insulating layer, as shown. The insulating layer (1010) may be FR4 using epoxy resin and glass fiber, but is not limited thereto.

[0059] The double-sided PCB manufacturing process forms a circuit wiring of a desired structure by forming a through hole (1100h) at a specific location as shown in Fig. 2(b), and then performing an etching process on the upper conductive layer (1100) and the lower conductive layer (1120). Next, a via filling process is performed to fill the interior of the through hole (1100h) with a conductive material. Referring to Figs. 2(b) and 2(c), the through hole (1100h) can be electrically connected to the upper conductive layer (1100) and the lower conductive layer (1120) to form a via hole (1100v). The via hole (1100v) can be implemented by forming it through a plating process or filling it with a conductive paste through a printing process.

[0060] A PCB (1000) is a substrate that houses the connecting elements that make up a circuit. It is required to attach electronic components and connect them to each other. To ensure proper operation in a variety of environments, it requires moisture resistance and high rigidity. Furthermore, a PCB must be flame-retardant to prevent electrical shorts or burning when exposed to flame.

[0061] Meanwhile, paper, a material composed of cellulose fibers derived from wood, is prone to flammability and moisture absorption. Therefore, for use as a PCB, surface treatment and compounding for moisture resistance and flame retardancy are necessary. In this regard, Figure 3 illustrates the laminated structure of a PCB comprising a paper substrate.

[0062] Referring to FIG. 3, the PCB (1000) may be configured to include a paper layer (1010) and coating layers (1020). The paper layer (1010) may include a first paper layer (1011) and a second paper layer (1012). The PCB (1000) may further include an adhesive layer (1030) that adheres the first paper layer (1011) and the second paper layer (1012).

[0063] The PCB (1000) requires coating layers (1020) for flame retardancy and moisture resistance on the upper and lower surfaces of the paper layer (1010). The coating layers (1020) may include a first coating layer (1021) formed on the upper surface of the paper layer (1010) and a second coating layer (1022) formed on the lower surface of the paper layer (1010). The coating layers (1020) may include a first coating layer (1021) formed on the upper surface of the first paper layer (1011) and a second coating layer (1022) formed on the lower surface of the second paper layer (1012).

[0064] As an example for flame retardancy, a method of adding a flame retardant to the coating layers (1020) can be used. The coating layers (1020) can be manufactured by forming them with a resin containing an environmentally friendly flame retardant. When an acrylic resin is used, moisture-proof coating layers (1020) can be formed, and as environmentally friendly flame retardants, phosphorus-based flame retardants and inorganic flame retardants can be used.

[0065] Ammonium polyphosphate, a phosphorus-based flame retardant, forms a carbon layer on the polymer surface during combustion, blocking oxygen. Inorganic flame retardants, such as aluminum hydroxide (Al(OH)3) and magnesium hydroxide (Mg(OH)2), secure flame retardant properties through heat absorption through dehydration. Meanwhile, halogenated flame retardants, such as brominated flame retardants, possess excellent flame retardancy, but are unsuitable for environmentally friendly PCB construction due to their carcinogenicity and hepatotoxicity.

[0066] Meanwhile, paper has a low elastic modulus of 0.8 GPa, and for use as a commercial circuit board, improved rigidity through composite materialization is necessary. In this regard, Fig. 4 illustrates the configuration in which temperature and pressure are applied for the composite materialization process of a printed circuit board having a paper layer. The configuration of Fig. 4 corresponds to the process of forming a composite material using a press process on a PCB (1010) having a paper layer (1010) of Fig. 3.

[0067] The composite material process can be performed by applying an adhesive to a coated paper layer (1010) and then performing a press process to form a composite. Meanwhile, depending on the process equipment, a coating process may be performed after the press process. It is preferable to use an organic resin as the adhesive for adhesion between the paper layers (1010) and flame retardancy and moisture absorption properties. Epoxy or acrylic resin can be used. As an inorganic filler, flame retardants such as magnesium hydroxide and aluminum hydroxide described in the coating agent, as well as aluminum oxide (Al2O3), silicon oxide (SiO2), titanium dioxide (TiO2), etc. can be used, and flame retardancy, mechanical properties, and adhesive strength can be improved.

[0068] Referring to FIGS. 3 and 4, a first adhesive layer (1021) and a second adhesive layer (1022) may be formed on the upper and lower surfaces of a paper layer (1010). A first press plate (PP1) may be disposed on the upper surface of the first adhesive layer (1021). A second press plate (PP2) may be disposed on the lower surface of the second adhesive layer (1022). Heat and pressure may be applied to the first adhesive layer (1021) and the second adhesive layer (1022) through the first press plate (PP1) and the second press plate (PP2).

[0069] To improve mechanical properties, it is necessary for the adhesive containing the inorganic filler to penetrate the pores of the paper layer (1010). In this regard, Fig. 5a shows the laminated structure and cross-sectional analysis photograph of a PCB having a paper layer formed through a high-temperature process. Fig. 5b shows the laminated structure and cross-sectional analysis photograph of a PCB having a paper layer formed through a high-temperature and high-pressure process.

[0070] Referring to Fig. 5a(a), the particles of the flame-retardant filler (1021a, 1022a), which are inorganic material particles of the first and second coating layers (1021, 1022), are hardly accepted into the paper layer (1010) through the high-temperature process. In addition, the inorganic material particles of the adhesive layer (1030) are hardly accepted into the paper layer (1010). Therefore, referring to Fig. 5a(b), the boundary between the first paper layer (1011) and the adhesive layer (1030) is clearly visible. In addition, the boundary between the adhesive layer (1030) and the first paper layer (1011) is clearly visible.

[0071] Referring to FIGS. 4 and 5b(a), it can be seen that the particles of the flame-retardant filler (1021a, 1022a) of the first and second coating layers (1021, 1022) are accepted into the paper layer (1010) through a high temperature and high pressure process. Accordingly, particles of the inorganic flame-retardant filler (1021b, 1022b) are detected in the paper layer (1010).

[0072] Specifically, particles of the flame-retardant filler (1021a) of the first coating layer (1021) penetrate into the pores of the first paper layer (1011) and are detected as particles of the flame-retardant filler (1021b). Particles of the flame-retardant filler (1022a) of the second coating layer (1022) penetrate into the pores of the second paper layer (1012) and are detected as particles of the flame-retardant filler (1022b). In addition, inorganic material particles (1030a) of the coating layer (1030) can penetrate into the pores of the paper layer (1010).

[0073] Referring to FIG. 4 and FIG. 5b(b), the boundary between the first paper layer (1011) and the adhesive layer (1030) is clearly visible. In addition, the boundary between the adhesive layer (1030) and the first paper layer (1011) is clearly visible.

[0074] Referring to FIGS. 4 and 5b, it can be confirmed that inorganic flame-retardant fillers (1030a, 1022b) are detected in area A composed of a paper layer (1010), thereby effectively progressing the composite. Accordingly, referring to FIGS. 5a and 5b, a paper substrate with significantly improved rigidity compared to general paper can be manufactured through a high-temperature and high-pressure press process accompanied by temperature and pressure.

[0075] Meanwhile, Fig. 6 compares the surface photographs of the paper layer of a PCB having a paper substrate and the paper layer of the PCB under various process conditions. Fig. 6(a) shows a cross-sectional photograph of a paper layer formed of paper material under room temperature and atmospheric pressure conditions. Fig. 6(b) shows a cross-sectional photograph of a paper layer under conditions of 100°C and 10Mpa pressure. Fig. 6(c) shows a cross-sectional photograph of a paper layer under conditions of 150°C and 10Mpa pressure. Fig. 6(d) shows a cross-sectional photograph of a paper layer under conditions of 170°C and 10Mpa pressure.

[0076] Referring to Figures 6(a) to 6(d), it can be confirmed that as the temperature and pressure increase, the inorganic flame-retardant filler penetrates into the pores of the paper layer, resulting in a denser texture. However, since cellulose can undergo thermal decomposition at temperatures above 200°C, a suitable temperature range of 100 to 200°C and a pressure range of 3 MPa to 10 MPa are suitable examples.

[0077] Meanwhile, Fig. 7 compares the stiffness of paper substrates under specific temperature and pressure conditions. Referring to Fig. 7, i) a general paper substrate has a stiffness of 0.8 GPa. On the other hand, when the temperature increases to 100 degrees at the maximum pressure of 10 Map, the stiffness increases to 2.6 GPa. Furthermore, when the temperature increases to 150 degrees at the maximum pressure of 10 Map, the stiffness increases to 3 GPa. Furthermore, when the temperature increases to 170 degrees at the maximum pressure of 10 Map, the stiffness increases to 3.8 GPa.

[0078] Next, we describe the process for manufacturing a PCB using the manufactured paper substrate. PCBs using paper material form circuit wiring through a printing process, rather than etching copper foil. This printing process is environmentally friendly because it allows for the formation of desired wiring directly through printing without the use of chemicals used in the etching process. Because paper is a porous material composed of cellulose, it exhibits excellent adhesion between the wiring and the substrate when printed with conductive paste. Some of the paste's binder is absorbed into the substrate, resulting in superior electrical properties compared to those achieved when printed on polymer film.

[0079] In this regard, Fig. 8 illustrates the processes of forming upper and lower wiring and via holes on both sides of a paper layer. Fig. 8(a) shows the manufacturing steps of an insulating board having a paper layer (1010). As described above, it is manufactured through coating and composite materialization to secure moisture resistance, flame retardancy, and rigidity required for a PCB. The paper layer (1010) is an insulating material and can function as an insulating layer located at the center of the board.

[0080] Figure 8(b) illustrates a step for forming a through hole (1100p) in a paper layer (1010). The through hole (1100p) can be processed using drilling or a laser. Hole processing and via filling processes of Φ0.4 mm are also possible in a paper substrate having a paper layer (1010).

[0081] Figures 8(c) and 8(d) illustrate circuit wiring formation steps for forming upper wirings (1110) and lower wirings (1120). The circuit wiring can be formed using a printing process such as screen printing or inkjet printing. The printing process is a manufacturing method suitable for eco-friendly substrates such as paper-based PCBs because it can form wiring without using an etching process. It is effective to print the upper wirings (1110) larger than the through-holes (1100p), as shown in Figure 8(c). This is because when printing without avoiding the through-holes (1100p), the conductive paste may block the through-holes, which may lead to defects in the via-holes.

[0082] When printing the lower wirings (1120), it is effective to design the mask to be equal to or smaller than the through hole (1100p). As shown in Fig. 8(d), it is printed by encroaching on a portion of the through hole (1100p), which has the advantage of stably connecting the upper wirings (1110) and the lower wirings (1120) during the via filling process.

[0083] Figure 8(e) illustrates a printing via process for forming a via hole (1100v). The paper layer (1010) is a porous material with excellent paste absorption properties. Therefore, the conductive paste is absorbed onto the side of the via hole (1100p) of Figure 8(d), enabling the stable formation of the via hole through the screen printing process.

[0084] Meanwhile, Fig. 9 illustrates a via filling process for forming a via hole. Fig. 9(a) is a process for preparing via hole printing in a state where a through hole (1100p) is formed. Referring to Fig. 9(a), screen masks (1050) may be placed on upper wirings (1110), and spacers (1040) may be placed on lower wirings (1120). A porous film (1045) may be placed under the spacers (1040). Conductive paste (1051) may be placed on the screen masks (1050), and pressure may be applied through a plate (1052) to cause the conductive paste (1051) to flow into the inside of the through hole (1100p).

[0085] FIG. 9(b) illustrates a process of printing via holes (1100v) on the side surfaces of the through hole (1100p) and the upper and lower surfaces of the paper layer (1010). Referring to FIG. 9(b), the via holes (1100v) may be formed on the side surfaces of the through hole (1100p). The via hole (1100v) includes an upper first protrusion (1110p) formed on the upper surface of the paper layer (1010). The via hole (1100v) includes a lower second protrusion (1120p) formed on the lower surface of the paper layer (1010).

[0086] FIG. 9(c) illustrates a process in which a porous film (1045) having spacers (1040) coupled with lower wires (1120) is removed. A portion (1051b) of conductive paste may be disposed between the spacers (1040). Additionally, screen masks (1050) coupled with upper wires (1110) may be removed. Via holes (1100v) may be formed on side surfaces of through holes (1100p). The via holes (1100v) include an upper first protrusion (1110p) formed on the upper surface of the paper layer (1010). The via holes (1100v) include a lower second protrusion (1120p) formed on the lower surface of the paper layer (1010).

[0087] Referring to Fig. 9, spacers (1040) and a porous film (1045) are attached to the lower portion of the substrate during the via filling process, and then a printing process is performed. To prevent the lower portion pressure (P1) from becoming higher than the upper portion pressure (P0) when forming a via hole (1100v), a porous film (1045) is provided at the lower portion of the PCB (1000).

[0088] Meanwhile, if the lower part of the PCB (1000) is blocked, the pressure at the lower part (P1) may increase, which may cause a problem in that the paste cannot be filled all the way to the via hole (1100v). The porous film (1045) is preferably a material having pores, such as a paper layer (1010), and the pressure can be adjusted according to the degree of air permeability. Therefore, the porous film (1045) can control the side wall thickness of the via hole (1100v) to the intended thickness by selecting an appropriate porous film.

[0089] The paste remaining after filling the via hole (1100v) can be attached to a porous film as shown in Fig. 9(c) so that the thickness protruding from the bottom of the via hole (1100v) does not exceed the thickness of the spacer (1040). Therefore, a spacer (1040) is required to adjust the height of the bottom of the via hole (1100v). A low-adhesion film or a thermal release film can be used as the spacers (1040). If the via filling process is performed without a spacer and a porous film, a high protrusion may be formed at the bottom of the via hole, and a defect may occur in the next process.

[0090] For example, when a protective layer printing process such as a subsequent solder resist is performed, problems such as printing defects or mask damage due to protrusions may occur. The thickness of the first protrusion (1110p) on the upper side of the via hole (1100v) is determined by the thickness of the screen mask (1050). As described above, the thickness of the second protrusion (1120p) on the lower side of the via hole (1100v) can be adjusted by the thickness of the spacer (1040). It is preferable to maintain the thickness of the first protrusion (1110p) on the upper side of the via hole (1100v) and the second protrusion (1120p) on the lower side to 50 um or less.

[0091] Meanwhile, Fig. 10 shows an example of a double-sided PCB manufactured using a paper substrate. Fig. 10(a) and Fig. 10(b) show the front and bottom sides of a PCB (1000) made of paper material.

[0092] Referring to FIGS. 10(a) and 10(b), electronic components in the form of chips can be mounted on the upper and lower surfaces. For example, the electronic components placed on the upper surface of the PCB (1000) can be light-emitting elements such as LEDs. The electronic components placed on the lower surface of the PCB (1000) can be passive elements such as chip resistors. The upper and lower surfaces of the PCB (1000) are electrically connected through via holes (1100v).

[0093] Fig. 10(c) is a cross-sectional X-Ray CT photograph of a double-sided PCB on which a via filling process has been performed on a paper layer. Referring to Fig. 10(c), it can be confirmed that a via hole (1100v) can be formed on the paper layer (1010) through a printing process. The via hole (1100v) penetrates the paper layer (1010) to electrically connect the upper wires (1110) and the lower wires (1120).

[0094] The outermost layer of a PCB (1000) having a paper substrate can be implemented as an SR (Solder Resist) layer (1060) as shown in FIG. 10. The SR layer (1060) functions to protect the circuit from the external environment while preventing unnecessary solder or conductive adhesive from being attached during component mounting. In the PCB (1000) having a paper substrate, it is preferable to form an SR layer (1060) that can be manufactured through a printing process, and a UV or thermally curable SR material can be used.

[0095] A PCB (1000) having a paper substrate can be used for various purposes other than as a rigid PCB with components mounted on both sides. For example, the PCB (1000) having a paper substrate can be used as a multilayer PCB with components mounted on only one side or as a double-sided flexible PCB. Since the PCB (1000) having a paper substrate forms circuit wiring through a printing process, it is possible to manufacture a double-sided board using a simpler process than that described above on a thin flexible paper substrate.

[0096] Meanwhile, a PCB having a paper substrate can also be used as a rigid PCB by combining with a reinforcing substrate. In this regard, Fig. 11 shows a perspective view and a partially enlarged view of a PCB having a paper substrate combined with a reinforcing substrate. Fig. 11(a) shows a perspective view of a PCB (1000) having a paper substrate combined with a reinforcing substrate. The PCB (1000) can be configured to include electronic components (1310, 1320, 1330) on the front surface. Fig. 11(b) shows a partially enlarged view of a PCB (1000) having a paper substrate combined with a reinforcing substrate.

[0097] Referring to FIG. 11, a printed circuit board (PCB) (1000) made of paper material and coupled to a reinforcing substrate is described. The paper material PCB (1000) may be configured to include electronic components (1310, 1320, 1330) on the front surface.

[0098] The first electronic component (1310) may be a power connector coupled to one side of the paper substrate. The power connector of the first electronic component (1310) may have a power terminal and a ground terminal. The second electronic component (1320) may be a surface mount component disposed on the upper wiring (1110). The surface mount component may be disposed on the upper wiring (1110) along a plurality of rows and columns. The surface mount component may be disposed between the first metal pad (MP1) and the second metal pad (MP2) of the upper wiring (1110). The third electronic component (1330) may be a coupling connector disposed on the wiring that couples the plurality of surface mount components.

[0099] Meanwhile, a PCB (1000) having a flexible paper substrate can be used in a portion requiring bending. As shown in FIG. 11, it can also be used as a rigid PCB by combining with a reinforcing substrate (1070). The PCB (1000) having a paper substrate can include a paper layer (1010), a reinforcing substrate (1070) disposed below the paper layer (1010), and a second adhesive layer (1080) that bonds the paper layer (1010) and the reinforcing substrate (1070). The PCB (1000) having a paper substrate can further include an SR layer (1060) formed on an upper surface of the paper layer (1010).

[0100] The material of the reinforcing substrate (1070) can be bonded to the paper layer (1010) not only with paper but also with biodegradable plastic. Therefore, even if a PCB (1000) having a paper layer (1010) is bonded to the reinforcing substrate (1070), it can be said to be an environmentally friendly PCB configuration.

[0101] The above has described a printed circuit board made of paper according to the present disclosure and a method for manufacturing the same. In this regard, the main configuration of a printed circuit board made of paper according to the present disclosure will be described with reference to FIGS. 2 to 11. A printed circuit board (PCB) (1000) made of paper may be configured to include a paper layer (1010) and coating layers (1020). The printed circuit board (PCB) (1000) may be configured to include through holes (1100p), wirings (1100), and via holes (1100v).

[0102] The paper layer (1010) may have pores formed therein to accommodate flame-retardant fillers (1021a, 1022a). Coating layers (1020) may be formed on the upper and lower surfaces of the paper layer (1010). The coating layers (1020) may include flame-retardant fillers (1021a, 1022a) to provide flame retardancy and moisture resistance to the paper layer (1010).

[0103] Through holes (1100p) may be formed to penetrate the paper layer (1010). Wires (1100) may be arranged on the upper or lower surface of the paper layer (1010). The wires (1100) may be configured to include upper wires (1110) arranged on the upper surface of the paper layer and lower wires (1120) arranged on the lower surface of the paper layer. Via holes (1100v) may be formed at a predetermined thickness on the side surfaces of the through holes (1100p). The via holes (1100v) may be formed to be electrically connected to the wires (1100). The via holes (1100v) may be configured to connect the upper wires (1110) and the lower wires (1120).

[0104] Meanwhile, the flame-retardant fillers (1021a, 1022a) of the coating layers (1020) can be penetrated into the pores of the paper layer (1020) through a pressing process under the conditions of a first range of temperature and a second range of pressure. Accordingly, the flame-retardant fillers (1021b, 1022b) can be filled into the pores of the paper layer (1020) to improve the rigidity of the paper layer (1020). In this regard, the temperature of the first range can be formed in the range of 100°C to 200°C. The pressure of the second range can be formed in the range of 3Mpa to 10Mpa.

[0105] The via holes (1100v) and the wiring (1100) may be formed using a conductive paste. The viscosity of the conductive paste forming the via holes (1100v) may be formed to be lower than the viscosity of the conductive paste forming the wiring (1100). Accordingly, the conductive paste forming the via holes (1100v) may have greater fluidity and may be formed with a uniform thickness on the side surfaces of the through holes (1100p).

[0106] The coating layers (1020) may be configured to include a first coating layer (1021) and a second coating layer (1022). The coating layers (1020) may be configured with the aforementioned flame-retardant fillers (1021a, 1022a) in an organic resin material. The flame-retardant fillers (1021a, 1022a) of the coating layers (1020) may penetrate into the pores of the paper layer (1020) under the aforementioned first temperature range and second pressure range conditions, thereby filling the pores with the flame-retardant fillers (1021b, 1022b). The first coating layer (1021) may be disposed on the upper surface of the paper layer (1020). The second coating layer (1020) may be disposed on the lower surface of the paper layer (1020). Meanwhile, the paper layer (1010) may be composed of a plurality of paper layers.

[0107] Meanwhile, the paper layer (1010) may be configured to include a first paper layer (1011) and a second paper layer (1012) disposed below the first paper layer (1011). In this regard, a first coating layer (1021) may be disposed on the upper surface of the first paper layer (1011). A second coating layer (1022) may be disposed on the lower surface of the second paper layer (1012).

[0108] Meanwhile, the PCB (1000) having a paper substrate may be configured to further include an adhesive layer (1030). The adhesive layer (1030) may be disposed between the lower surface of the first paper layer (1011) and the upper surface of the second paper layer (1012). The adhesive layer (1030) may be configured to adhere the first paper layer (1011) and the second paper layer (1012). The adhesive layer (1030) may be configured to adhere the lower surface of the first paper layer (1011) and the upper surface of the second paper layer (1012).

[0109] Meanwhile, the inorganic filler (1030a) of the adhesive layer (1030) can improve the rigidity and flame retardancy of the paper layer (1010). In this regard, the adhesive layer (1030) can include the inorganic filler (1030a). The inorganic filler (1030a) of the adhesive layer (1030) can penetrate into the first paper layer (1011) and the second paper layer (1012) through a pressing process under the conditions of a first range of temperature and a second range of pressure. The inorganic filler (1030a) of the adhesive layer (1030) can penetrate into the pores of the first paper layer (1011) and the pores of the second paper layer (1012), thereby improving the rigidity and flame retardancy of the paper layer (1010).

[0110] Meanwhile, via holes for connecting upper / lower wires may be formed inside the through holes of a printed circuit board (PCB) (1000) made of paper according to the present disclosure. In this regard, the PCB (1000) may be configured to include through holes (1100p), upper wires (1110), and lower wires (1120). The PCB (1000) may further be configured to include via holes (1100v) formed through a via filling process.

[0111] Through holes (1100p) may be formed in first regions of the paper layer (1010). Upper wires (1110) may be arranged in second regions of the upper surface of the paper layer (1010). Lower wires (1120) may be arranged in second regions of the lower surface of the paper layer (1010). The through holes (1100p) may be arranged in regions where the upper wires (1110) or the lower wires (1120) are not arranged. In this regard, the through holes (1100p) may be formed in a land structure such as a metal pad. Meanwhile, the through holes (1100p) may be arranged to partially overlap with the second region where the upper wires (1110) or the lower wires (1120) are arranged.

[0112] Via holes (1100v) with a predetermined thickness can be formed on the side surfaces of the through holes (1100p). The via holes (1100v) can be formed to be connected to the ends of the upper wirings (1110) and the ends of the lower wirings (1120).

[0113] The ends of the upper wires (1110p) may be formed further inward than the ends of the paper portions (1010) separated by the through holes (1100p). The ends of the lower wires (1120) may be formed further outward so as to protrude further than the ends of the paper portions (1010). The first protrusions (1110p) on the upper portions of the via holes (1100v) connected to the ends of the upper wires (1110) may be formed with a first diameter. The first protrusions (1110p) on the upper portions of the via holes (1100v) having the first diameter may be referred to as first metal pads. The second protrusions (1120p) on the lower portions of the via holes (1100v) connected to the ends of the lower wires (1120) may be formed with a second diameter. The second protrusions (1120p) at the bottom of the via holes (1100v) having the second diameter may be referred to as second metal pads. The first diameter of the first protrusions (1110p) at the top of the via holes (1100v) may be formed to be larger than the second diameter of the second protrusions (1120p) at the bottom of the via holes (1100v) connected to the ends of the lower wirings (1120).

[0114] Meanwhile, a printed circuit board (PCB) (1000) made of paper can optimally design and manufacture via holes (1100v) during a via filling process using spacers (1040) and screen masks (1050). In this regard, screen masks (1050) may be placed on top of upper wirings (1110). Spacers (1040) may be placed under lower wirings (1120). The via holes (1100v) may be formed by conductive pastes placed on screen masks (1050) being adsorbed onto the side surfaces of through holes (1100p) during a via filling process.

[0115] Meanwhile, the upper wiring layers (1110) adjacent to the via holes (1100v) can be printed to avoid the via holes (1100v). Therefore, the conductive paste can be prevented from being filled into the via holes (1100v). The lower wiring layers (1120) can be formed to penetrate into the via holes (1100v). Therefore, the second protrusions (1120p) can be electrically connected at the bottoms of the via holes (1100v) where the spacers (1040) are arranged during the via filling process.

[0116] In a via filling process connecting upper wirings (1110) and lower wirings (1120), spacers (1040) may be placed on the lower wirings (1120). The spacers (1040) may be placed on a porous film (1045) underneath. As the porous film (1045) is removed, the second protrusions (1120p) connected by the via filling process may be electrically isolated.

[0117] Meanwhile, the thickness of the paper layer (1010) can be formed to be 0.3 mm or less. Accordingly, a via filling process can be performed on the side surfaces of the through holes (1100p) simultaneously with the printing process of the upper wires (1110) and the lower wires (1120).

[0118] The above has described a printed circuit board (1000) made of paper according to one aspect of the present disclosure. Below, a method for manufacturing a printed circuit board (1000) made of paper according to another aspect of the present disclosure will be described. In this regard, FIGS. 12 and 13 illustrate flowcharts of a method for manufacturing a printed circuit board made of paper according to the present disclosure.

[0119] Referring to FIGS. 2 to 13, a method for manufacturing a printed circuit board made of paper will be described. The method for manufacturing a printed circuit board (PCB) (1000) made of paper can be configured to include a paper layer preparation process (S100), a coating layer formation process (S200), and a press process (S300). The method for manufacturing a printed circuit board (PCB) (1000) can further be configured to include a through-hole formation process (S400), a wiring formation process (S500), and a via hole formation process (S600).

[0120] In a paper layer preparation process (S100), a paper layer (1010) having pores formed therein so that a flame-retardant filler (1021a, 1022a) can be accommodated can be prepared. In a coating layer formation process (S200), coating layers (1020) can be formed on the upper and lower surfaces of the paper layer (1010). The coating layers (1020) can include flame-retardant fillers (1021a, 1022a) for flame retardancy and moisture resistance of the paper layer (1010).

[0121] In the press process (S300), a first temperature range and a second pressure range can be applied to the paper substrate on which the coating layers (1020) are formed. Through the press process (S300), the flame-retardant fillers (1021a, 1022a) of the coating layers (1020) can penetrate into the pores of the paper layer (1010), thereby improving the rigidity, flame retardancy, and flame resistance of the paper layer (1010).

[0122] In the through-hole forming process (S400), through-holes (1100p) may be formed to penetrate the paper layer (1010). In the wire forming process (S500), wires (1100) may be formed to be arranged on the upper or lower surface of the paper layer (1010). The wires (1100) may be configured to include upper wires (1110) arranged on the upper surface of the paper layer and lower wires (1120) arranged on the lower surface of the paper layer. In the via-hole forming process (S600), via-holes (1100v) may be formed at a predetermined thickness on the side surfaces of the through-holes (1100p). The via-holes (1100v) may be formed to be electrically connected to the wires (1100). The via-holes (1100v) may be formed to connect the upper wires (1110) and the lower wires (1120).

[0123] Meanwhile, the flame-retardant fillers (1021a, 1022a) of the coating layers (1020) can be penetrated into the pores of the paper layer (1020) through a pressing process under the conditions of a first range of temperature and a second range of pressure. Accordingly, the flame-retardant fillers (1021b, 1022b) can be filled into the pores of the paper layer (1020) to improve the rigidity of the paper layer (1020). In this regard, in the pressing process (S300), the first range of temperature can be formed in a range of 100°C to 200°C. The second range of pressure can be formed in a range of 3Mpa to 10Mpa.

[0124] The via holes (1100v) and the wiring (1100) may be formed using a conductive paste. The viscosity of the conductive paste forming the via holes (1100v) may be formed to be lower than the viscosity of the conductive paste forming the wiring (1100). Accordingly, the conductive paste forming the via holes (1100v) may have greater fluidity and may be formed with a uniform thickness on the side surfaces of the through holes (1100p).

[0125] The coating layers (1020) may be composed of the aforementioned flame-retardant fillers (1021a, 1022a) on an organic resin material. The flame-retardant fillers (1021a, 1022a) of the coating layers (1020) may penetrate into the pores of the paper layer (1020) under the temperature conditions of the first range and the pressure conditions of the second range, thereby filling the pores with the flame-retardant fillers (1021b, 1022b). The coating layer forming process (S200) may be configured to include a first coating layer forming process (S210) and a second coating layer forming process (S220). In the first coating layer forming process (S210), a first coating layer (1021) disposed on the upper surface of the paper layer (1020) may be formed. In the second coating layer forming process (S220), a second coating layer (1020) may be formed on the lower surface of the paper layer (1020). Meanwhile, the paper layer (1010) may be composed of a plurality of paper layers.

[0126] Meanwhile, the paper layer preparation process (S100) may include a second paper layer preparation process (S110), an adhesive layer arrangement process (S120), and a first paper layer arrangement process (S130). The paper layer (1010) may be configured to include a first paper layer (1011) and a second paper layer (1012) arranged below the first paper layer (1011).

[0127] In the second paper layer preparation process (S110), a second paper layer (1012) having pores formed therein may be prepared. In the adhesive layer arrangement process (S120), an adhesive layer (1030) may be arranged on the upper surface of the second paper layer (1012). In the first paper layer arrangement process (S130), a first paper layer (1011) having pores formed therein may be arranged on the adhesive layer (1030). Accordingly, the adhesive layer (1030) may be arranged between the lower surface of the first paper layer (1011) and the upper surface of the second paper layer (1012). The adhesive layer (1030) may be configured to adhere the first paper layer (1011) and the second paper layer (1012). The adhesive layer (1030) may be configured to adhere the lower surface of the first paper layer (1011) and the upper surface of the second paper layer (1012).

[0128] Meanwhile, the inorganic filler (1030a) of the adhesive layer (1030) can improve the rigidity and flame retardancy of the paper layer (1010). In this regard, the adhesive layer (1030) can include the inorganic filler (1030a). In the pressing process (S300) under the conditions of the first range of temperature and the second range of pressure, the inorganic filler (1030a) of the adhesive layer (1030) can penetrate into the first paper layer (1011) and the second paper layer (1012). The inorganic filler (1030a) of the adhesive layer (1030) can penetrate into the pores of the first paper layer (1011) and the pores of the second paper layer (1012), thereby improving the rigidity and flame retardancy of the paper layer (1010).

[0129] Meanwhile, in the method for manufacturing a printed circuit board (PCB) (1000) made of paper according to the present disclosure, via holes for connecting upper / lower wirings can be formed within the through holes. In the through hole forming process (S400), through holes (1100p) can be formed in first regions of the paper layer (1010).

[0130] The wiring forming process (S500) may include an upper wiring forming process (S510) and a lower wiring forming process (S520). In the upper wiring forming process (S510), upper wirings (1110) may be formed to be arranged in second regions on the upper surface of the paper layer (1010). In the lower wiring forming process (S520), lower wirings (1120) may be formed to be arranged in second regions on the lower surface of the paper layer (1010). In the via hole forming process (S600), via holes (1100v) may be formed with a predetermined thickness on the side surfaces of the through holes (1100p). In the via hole forming process (S600), the via holes (1100v) may be formed to be connected to the ends of the upper wirings (1110) and the ends of the lower wirings (1120).

[0131] In the wiring forming process (S500), the ends of the upper wires (1110p) may be formed further inward than the ends of the paper portions (1010) separated by the through holes (1100p). The ends of the lower wires (1120) may be formed further outward so as to protrude further than the ends of the paper portions (1010).

[0132] In the via hole forming process (S600), the first protrusions (1110p) on the upper portions of the via holes (1100v) connected to the ends of the upper wirings (1110) may be formed with a first diameter. The first protrusions (1110p) on the upper portions of the via holes (1100v) having the first diameter may be referred to as a first metal pad. The second protrusions (1120p) on the lower portions of the via holes (1100v) connected to the ends of the lower wirings (1120) may be formed with a second diameter. The second protrusions (1120p) on the lower portions of the via holes (1100v) having the second diameter may be referred to as a second metal pad. The first diameter of the first protrusion (1110p) on the upper side of the via holes (1100v) may be formed to be larger than the second diameter of the second protrusion (1120p) on the lower side of the via holes (1100v) connected to the ends of the lower wirings (1120).

[0133] Meanwhile, a printed circuit board (PCB) (1000) made of paper material can optimally design and manufacture via holes (1100v) during a via filling process using spacers (1040) and screen masks (1050). In this regard, the via hole forming process (S600) may include a screen mask arrangement process (S610), a space arrangement process (S620), and a via filling process (S630).

[0134] In the screen mask placement process (S610), screen masks (1050) may be placed on top of the upper wires (1110). In the space placement process (S620), spacers (1040) may be placed on bottom of the lower wires (1120). In the via filling process (S630), conductive pastes placed on the screen masks (1050) may be adsorbed on the side surfaces of the through holes (1100p) to form via holes (1100v).

[0135] Meanwhile, the upper wiring layers (1110) adjacent to the via holes (1100v) can be printed to avoid the via holes (1100v). Therefore, the conductive paste can be prevented from being filled into the via holes (1100v). The lower wiring layers (1120) can be formed to penetrate into the via holes (1100v). Therefore, the second protrusions (1120p) can be electrically connected at the bottoms of the via holes (1100v) where the spacers (1040) are arranged during the via filling process.

[0136] In a via filling process (S630) connecting upper wires (1110) and lower wires (1120), spacers (1040) may be placed on the lower wires (1120). The spacers (1040) may be placed on a porous film (1045) below. The via hole forming process (S600) may further include a porous film removing process (S640). In the porous film removing process (S640), the second protrusions (1120p) connected by the via filling process (S630) may be electrically isolated as the porous film (1045) is removed from the spacers (1040).

[0137] Meanwhile, the method for manufacturing a printed circuit board using paper material described above is not limited to the order of the flowcharts of FIGS. 12 and 13. In this regard, FIG. 14 shows a schematic diagram according to an embodiment of a method for manufacturing a printed circuit board using paper material in a double-sided form. In this regard, when using a thin paper substrate, the conductive paste can be applied to the sidewalls of the perforated portions while the wiring printing process is being performed, so that the via filling process can be performed simultaneously with the wiring printing. The thickness of the thin paper substrate can be 0.3 mm or less, which allows for easy bending and straightening. In the case of a paper substrate having a thickness of 1 mm or more, such as a rigid PCB, it can be effective to perform the wiring printing and the via printing separately.

[0138] Referring to FIG. 14, the manufacturing method may be configured to include a substrate preparation process (S301), a through-hole formation process (S400), an upper wiring formation process (S510), and a lower wiring formation process (S520). The manufacturing method may further include a preliminary substrate bonding process (S501) between the through-hole formation process (S400) and the upper wiring formation process (S510). The manufacturing method may further include a preliminary substrate removal process (S511) and a preliminary substrate bonding process (S512) between the upper wiring formation process (S510) and the lower wiring formation process (S520). The manufacturing method may further include a preliminary substrate removal process (S521) after the lower wiring formation process (S520).

[0139] Hereinafter, a method for manufacturing a double-sided paper-based printed circuit board (PCB) (1000) will be described with reference to FIGS. 1 to 14.

[0140] The substrate preparation process (S301) may correspond to the paper layer preparation process (S100), the coating layer forming process (S200), and the press process (S300) of FIGS. 12 and 13. Through the substrate preparation process (S301), coating layers (1020) for flame retardancy and moisture resistance may be formed on the upper and lower surfaces of the paper layer (1010). As the coating layers (1020) for flame retardancy and moisture resistance are formed, a paper substrate made of paper material that has been subjected to a water-repellent and flame retardant treatment may be formed. Therefore, a paper substrate with improved rigidity and flame retardancy may be prepared through the substrate preparation process (S301).

[0141] Through a through-hole forming process (S400), a through-hole (1100p) can be formed in a paper substrate. A cutter, a laser, a drill, etc. can be used to form a through-hole (1100p) in the paper substrate. In a preliminary substrate bonding process (S501), a preliminary substrate can be bonded to the edge of the paper substrate. Through the preliminary substrate bonding process (S501), the conductive paste can be prevented from being sucked into the punched hole during the printing process of the upper wiring (1110), and the flatness of the upper wiring (1110) can be improved. The preliminary substrate is a temporary substrate, and a low-adhesion film or a thermal release film having a thickness of 10 gf or less can be used.

[0142] The printed wiring of the upper wiring (1110) can be formed through the upper wiring formation process (S510). When printing the wiring, conductive paste can enter the through hole (1100p) and a via hole (1100v) can be formed on the side wall of the through hole (1100p) through a via filling process. Therefore, the via hole formation process (S600) of FIGS. 12 and 13 can be performed simultaneously in the upper wiring formation process (S510). Through the upper wiring formation process (S510), the upper wiring (1110) and the via hole (1100v) can be formed and the curing of the conductive paste can be performed.

[0143] The preliminary substrate bonded to the edge of the paper substrate can be removed through the preliminary substrate removal process (S511). Through the preliminary substrate removal process (S511), the formation of one side of the paper substrate on which the upper wiring (1110) is formed can be completed. Meanwhile, the method for manufacturing a double-sided paper material printed circuit board can be configured such that the preliminary substrate bonding process (S512) is performed.

[0144] The preliminary substrate bonding process (S512) can prevent conductive paste from being sucked into the perforated holes during the printing process of the lower wiring (1120) and improve the flatness of the lower wiring (1120). The preliminary substrate is a temporary substrate, and a low-adhesion film or thermal release film of 10 gf or less can be used.

[0145] The printed wiring of the lower wiring (1120) can be formed through the lower wiring formation process (S520). When printing the wiring, conductive paste can enter the through hole (1100p) and a via-filling process can be used to form a via hole (1100v) on the side wall of the through hole (1100p). Therefore, the via-hole formation process (S600) of FIGS. 12 and 13 can be performed simultaneously in the lower wiring formation process (S520). Through the lower wiring formation process (S520), the lower wiring (1120) and the via hole (1100v) can be formed and even the curing of the conductive paste can be performed. Through the preliminary substrate removal process (S521), the preliminary substrate bonded to the edge of the paper substrate can be removed. Through the preliminary substrate removal process (S521), the formation of both sides of the paper substrate on which the upper wiring (1110) and the lower wiring (1120) are formed can be completed.

[0146] The above describes a printed circuit board made of paper and a method for manufacturing the same according to the present disclosure. The technical effects of the printed circuit board made of paper and the method for manufacturing the same according to the present disclosure are as follows.

[0147] According to this specification, in order to use paper material as a PCB, it is possible to have flame retardant properties and moisture absorption prevention through a composite structure including a coating layer for flame retardancy / moisture resistance and an adhesive layer.

[0148] According to the present specification, the rigidity of a paper substrate can be improved by permeating an inorganic material included in a coating and adhesive material into the pores of the paper.

[0149] According to this specification, the upper / lower circuit wiring layers are formed by a printing process using a conductive paste, and when the upper / lower circuit wiring layers are connected by via holes, the shapes of the upper and lower layers are optimized so that electrical stability and mechanical stability can be implemented.

[0150] Further scope of the applicability of this specification will become apparent from the detailed description below. However, since various changes and modifications within the spirit and scope of this specification will be apparent to those skilled in the art, it should be understood that the detailed description and specific examples, such as preferred embodiments, are given by way of example only.

[0151] Meanwhile, the detailed description above should not be construed as limiting in any respect and should be considered illustrative. The scope of this specification should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of this specification are intended to be included within the scope of this specification.

Claims

1. In a printed circuit board made of paper, A paper layer having pores formed therein so that flame-retardant filler can be accommodated; and Provided with the flame retardant filler for flame retardancy and moisture resistance of the above paper layer, and including coating layers formed on the upper and lower surfaces of the above paper layer, Through holes formed to penetrate the above paper layer; Wires arranged on the upper or lower surface of the above paper layer; and It includes via holes formed on the side of the above through holes with a predetermined thickness and formed to be electrically connected to the above wirings, A printed circuit board, wherein the flame retardant filler of the coating layers penetrates into the pores of the paper layer through a pressing process under conditions of a first range of temperature and a second range of pressure, thereby improving the rigidity and flame retardancy of the paper layer.

2. In paragraph 1, The above via hole and the above wiring are formed with conductive paste, A printed circuit board, wherein the viscosity of the conductive paste forming the via holes is formed lower than the viscosity of the conductive paste forming the via holes.

3. In paragraph 1, The temperature of the first range is formed in a range of 100 ℃ to 200 ℃, A printed circuit board, wherein the pressure of the second range is formed in a range of 3 MPa to 10 MPa.

4. In paragraph 1, The above coating layers include a first coating layer disposed on the upper surface of the paper layer and a second coating layer disposed on the lower surface of the paper layer, A printed circuit board, characterized in that the above coating layers include an organic or inorganic flame retardant filler in an organic resin material.

5. In paragraph 1, The above paper layer comprises a first paper layer and a second paper layer disposed below the first paper layer, A printed circuit board further comprising an adhesive layer disposed between the lower surface of the first paper layer and the upper surface of the second paper layer and configured to adhere the first paper layer and the second paper layer.

6. In paragraph 5, The above adhesive layer comprises an inorganic filler, A printed circuit board, characterized in that the adhesive layer is formed by a pressing process under the conditions of the first range of temperature and the second range of pressure, and the inorganic filler penetrates into the first paper layer and the second paper layer, thereby improving the rigidity and flame retardancy of the paper layers.

7. In paragraph 1, The above through holes are formed in the first regions of the paper layer, The above wiring includes upper wirings arranged in second areas on the upper surface of the paper layer and lower wirings arranged in second areas on the lower surface of the paper layer, A printed circuit board, wherein the above via holes are formed to be connected to the ends of the upper wirings and the ends of the lower wirings.

8. In paragraph 7, The ends of the above upper wires are formed further inward than the ends of the paper portions separated by the through holes, The ends of the above lower wires are formed further outwardly and protruding than the ends of the above paper parts, A printed circuit board, wherein a first diameter of a first protrusion on the upper side of the via holes connected to the ends of the upper wirings is formed larger than a second diameter of a second protrusion on the lower side of the via holes connected to the ends of the lower wirings.

9. In paragraph 8, Screen masks are placed on top of the above upper wirings, Spacers are placed at the bottom of the above lower wirings, A printed circuit board, wherein the above via holes are formed by conductive pastes arranged on the screen masks being absorbed onto the side surfaces of the through holes by a via filling process.

10. In paragraph 9, The upper wirings adjacent to the via holes are printed to avoid the via holes, thereby preventing the conductive paste from filling into the interior of the via holes. A printed circuit board, characterized in that the lower wirings penetrate into the interior of the via holes, and the second protrusions are electrically connected at the bottoms of the via holes by the via filling process.

11. In paragraph 9, In the via filling process connecting the upper wirings and the lower wirings, the spacers are placed on the lower wirings, The above spacers are arranged on the lower porous film, A printed circuit board, characterized in that the second protrusions connected by the via filling process are electrically isolated as the porous film on which the spacers are arranged is removed.

12. In paragraph 9, A printed circuit board characterized in that the thickness of the paper layer is formed to be 0.3 mm or less, and the via filling process is performed on the side surfaces of the through holes simultaneously with the printing process of the upper wirings and the lower wirings.

13. In a method for manufacturing a printed circuit board made of paper, A paper layer preparation process which prepares a paper layer having pores formed inside so that flame-retardant filler can be accommodated; A coating layer forming process comprising providing the flame retardant filler for flame retardancy and moisture resistance of the paper layer and forming coating layers on the upper and lower surfaces of the paper layer; A press process of applying a first range of temperature and a second range of pressure to a paper substrate on which the coating layers are formed so that the flame retardant filler of the coating layers penetrates into the pores of the paper layer to improve the rigidity and flame retardancy of the paper layer; A through hole forming process for forming through holes to penetrate the above paper layers; A wire forming process for forming wires arranged on the upper or lower surface of the above paper layer; and A method for manufacturing a printed circuit board, comprising a via hole forming process for forming via holes having a predetermined thickness on the side surfaces of the above through holes and electrically connecting the via holes to the above wirings.

14. In paragraph 13, The above via hole and the above wiring are formed with conductive paste, The viscosity of the conductive paste forming the via hole is formed lower than the viscosity of the conductive paste forming the via holes. A method for manufacturing a printed circuit board, wherein, in the above pressing process, the temperature of the first range is formed in a range of 100 ℃ to 200 ℃, and the pressure of the second range is formed in a range of 3 MPa to 10 MPa.

15. In paragraph 13, The above coating layer forming process includes a first coating layer forming process for forming a first coating layer disposed on the upper surface of the paper layer and a second coating layer forming process for forming a second coating layer disposed on the lower surface of the paper layer. A method for manufacturing a printed circuit board, characterized in that the above coating layers include an organic or inorganic flame retardant filler in an organic resin material.

16. In paragraph 13, The above paper layer preparation process is, A second paper layer preparation process for preparing a second paper layer having pores formed inside; An adhesive layer placement process for placing an adhesive layer on the upper surface of the second paper layer; and Including a first paper layer arrangement process of arranging a first paper layer having pores formed inside the adhesive layer, The adhesive layer is formed between the lower surface of the first paper layer and the upper surface of the second paper layer to adhere the first paper layer and the second paper layer, and the adhesive layer includes an inorganic filler. A method for manufacturing a printed circuit board, wherein in the pressing process under the conditions of the first range of temperature and the second range of pressure, the adhesive layer is characterized in that the inorganic filler penetrates into the first paper layer and the second paper layer to improve the rigidity and flame retardancy of the paper layers.

17. In paragraph 13, In the above through hole forming process, the through holes are formed in the first areas of the paper layer, The above wiring formation process is, An upper wiring forming process for forming upper wirings arranged in second areas on the upper surface of the above paper layer; and Including a lower wiring forming process for forming lower wirings arranged in second areas on the lower surface of the above paper layer, A method for manufacturing a printed circuit board, wherein in the above via hole forming process, the via holes are formed to be connected to the ends of the upper wirings and the ends of the lower wirings.

18. In paragraph 17, The ends of the above upper wires are formed further inward than the ends of the paper portions separated by the through holes, The ends of the above lower wires are formed further outwardly and protruding than the ends of the above paper parts, A method for manufacturing a printed circuit board, wherein a first diameter of a first protrusion on the upper side of the via holes connected to the ends of the upper wirings is formed larger than a second diameter of a second protrusion on the lower side of the via holes connected to the ends of the lower wirings.

19. In paragraph 18, The above via hole formation process is, A screen mask placement process for placing screen masks on top of the above upper wirings; A space placement process for placing spacers at the bottom of the above lower wirings; and A via filling process is included so that conductive pastes placed on the above screen masks are adsorbed and formed on the side of the through hole. The upper wirings adjacent to the via holes are printed to avoid the via holes, thereby preventing the conductive paste from filling into the interior of the via holes. A method for manufacturing a printed circuit board, characterized in that the lower wirings penetrate into the interior of the via holes, and the second protrusions are electrically connected at the bottoms of the via holes by the via filling process.

20. In paragraph 19, In the via filling process connecting the upper wirings and the lower wirings, the spacers are placed on the lower wirings, The above spacers are arranged on the lower porous film, The above via hole formation process is, A method for manufacturing a printed circuit board, further comprising a porous film removing process in which the second protrusions connected by the via filling process are electrically isolated as the porous film on which the spacers are arranged is removed.

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