Printed circuit board of paper material

Abstract

This printed circuit board of a paper material includes: a paper substrate in which pores are formed; thin-film lands printed and formed with a conductive material on the paper substrate; and a slot structure of at least one recess or hole formed in the paper substrate and corresponding to an area where the thin-film lands are formed. While the thin-film lands are printed with the conductive material, the conductive material is absorbed into the slot structure of the paper substrate and pores adjacent to the slot structure, thereby improving the adhesion of the thin-film lands.

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, in structures where wires or thin-film lands are formed on a paper substrate, there is an issue where the wires and thin-film lands do not adhere well to the paper substrate. In this regard, when printing wires or thin-film lands on a paper substrate within a specific temperature range, shrinkage of the paper substrate can cause the wires or thin-film lands to peel off from the paper substrate.

[0008] The present specification aims to solve the aforementioned problems and other problems. The purpose of the present specification is to address the issue of poor adhesion of wires and thin-film lands to the paper substrate in structures where wires or thin-film lands are formed on the paper substrate.

[0009] The purpose of this specification is to solve the issue of wires or thin film lands peeling off from a paper substrate due to shrinkage of the paper substrate when printing wires or thin film lands on the paper substrate at a specific temperature range.

[0010] The purpose of this specification is to simplify the heat treatment process for different types of electronic components on printed circuit boards made of paper.

[0011] To achieve the above or other purposes, a printed circuit board made of paper according to the present specification comprises: a paper substrate having pores formed therein; a thin film land formed by printing a conductive material on the paper substrate; and at least one slot structure of a groove or hole formed in the paper substrate corresponding to an area where the thin film land is formed. While printing the thin film land with the conductive material, the conductive material is absorbed into the inside of the slot structure of the paper substrate and into pores adjacent to the slot structure, thereby improving the adhesion of the thin film land.

[0012] According to an embodiment, the thin film land may be composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, or a third conductive paste made of Ti material.

[0013] According to an embodiment, the slot structure may be composed of a plurality of grooves formed spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate may be formed to be thicker than the thickness of the grooves.

[0014] According to an embodiment, the slot structure may be composed of a plurality of holes formed spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0015] According to an embodiment, the slot structure may be formed as a cross structure of a plurality of grooves and holes that are alternately formed and spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate may be formed to be thicker than the thickness of the grooves. The thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0016] According to an embodiment, the slot structure within the paper substrate may be electrically connected to the thin film land. The at least one groove or hole may be configured as a single or multiple grooves in a circular, linear, cross-shaped, rectangular, or polygonal structure.

[0017] According to an embodiment, the printed circuit board may further include wiring formed by printing a conductive material on a first surface of the paper substrate and configured to be connected to a surface mount device disposed on the paper substrate. The printed circuit board may further include a through hole formed to penetrate the thin film land.

[0018] According to an embodiment, the printed circuit board may further include an insert mount device configured to be inserted through the first side and the second side of the paper substrate through the thin film land. The surface mount device may be positioned between the boundary of the thin film land and the wiring. After the insert mount device is fixed to the paper substrate, the insert mount device and the surface mount device may be thermally cured together, thereby reducing the number of thermal processes from two to one.

[0019] According to an embodiment, the insertion mounting component can be fixed by bonding to the area where the through hole is formed. The printed circuit board may further include a second conductive adhesive layer formed by applying it to the second surface of the paper substrate corresponding to the area where the insertion mounting component is bonded.

[0020] According to an embodiment, the printed circuit board may further include a first conductive adhesive layer formed in an area adjacent to the through hole on the first surface of the paper substrate. The first conductive adhesive layer may be formed on the upper surface and side surfaces of the thin film land and a portion of the side surfaces of the through hole.

[0021] According to an embodiment, the printed circuit board may include a plurality of light-emitting devices (LEDs) spaced apart from each other in a uniaxial direction on the paper substrate; a plurality of resistors spaced apart from each other in a uniaxial direction between the plurality of light-emitting devices; a power line formed in the uniaxial direction in an upper region of the plurality of light-emitting devices and the plurality of resistors and branched to be connected to a first light-emitting device and a third light-emitting device; and a ground line formed in the uniaxial direction in a lower region of the plurality of light-emitting devices and the plurality of resistors and branched to be connected to a second light-emitting device and a fourth light-emitting device. The resistance values ​​of the resistors may be formed to have different values.

[0022] According to an embodiment, the power line may be connected to the first light-emitting element and the third light-emitting element, which are closer than the second light-emitting element and the fourth light-emitting element among the plurality of light-emitting elements. The ground line may be connected to the second light-emitting element and the fourth light-emitting element, which are further away than the first light-emitting element and the third light-emitting element among the plurality of light-emitting elements.

[0023] According to an embodiment, the printed circuit board may include a plurality of light-emitting elements spaced apart in a uniaxial direction on the paper substrate; a plurality of resistors spaced apart in the uniaxial direction between the plurality of light-emitting elements; a power line formed in the uniaxial direction in an upper region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to first and third light-emitting elements; a first ground line formed in the uniaxial direction in a lower region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to second and fourth light-emitting elements; and a second ground line connected to one end of the first ground line, arranged parallel to the first ground line, and having an end connected to a ground terminal of a connector. The other end of the first ground line may be formed spaced apart from the connector.

[0024] According to another aspect of the present disclosure, a method for manufacturing a printed circuit board made of paper includes a slot structure forming process for forming a slot structure of at least one groove or hole in a paper substrate having pores formed therein; and a thin film land forming process for forming a thin film land by printing a conductive material on the paper substrate to correspond to an area where the groove or hole is formed. In the thin film land forming process, while printing the thin film land with the conductive material, the conductive material is absorbed into the interior of the slot structure and pores adjacent to the slot structure, thereby improving the adhesion of the thin film land.

[0025] According to an embodiment, the thin film land may be composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, and a third conductive paste made of Ti material.

[0026] According to an embodiment, the slot structure forming process may include a plurality of groove forming processes for forming a plurality of grooves spaced apart in one axial direction of the paper substrate. In the plurality of groove forming processes, the thickness of the paper substrate may be formed to be thicker than the thickness of the grooves.

[0027] According to an embodiment, the slot structure forming process may include a plurality of hole forming processes for forming a plurality of holes spaced apart in one axial direction of the paper substrate. In the plurality of hole forming processes, the thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0028] According to an embodiment, the slot structure forming process may include a plurality of groove and hole forming processes in which grooves and holes are alternately formed while being spaced apart in one axial direction of the paper substrate. In the plurality of groove and hole forming processes, the thickness of the paper substrate may be formed to be thicker than the thickness of the grooves, and the thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0029] According to an embodiment, at least one groove or hole within the paper substrate may be electrically connected to the thin film land. The at least one groove or hole may be configured as a single or multiple grooves in a circular, linear, cross-shaped, rectangular, or polygonal structure.

[0030] According to an embodiment, the manufacturing method may further include a wiring forming process for forming wiring between the slot structure forming process and the thin film land forming process. The manufacturing method may further include a through hole forming process for forming a through hole to pass through the thin film land after the thin film land forming process. In the wiring forming process, the wiring may be formed by printing a conductive material on a first surface of the paper substrate and connected to a surface mount device placed on the paper substrate.

[0031] According to an embodiment, the manufacturing method may further include an insertion-mount component mounting process in which an insertion-mount component is inserted through the first side and the second side of the paper substrate through the thin film land after the through-hole forming process. The manufacturing method may further include a surface-mount component placement process in which a surface-mount component is placed between a boundary of the thin film land and the wiring. The manufacturing method may further include a thermal curing process in which the insertion-mount component and the surface-mount component are thermally cured together after the insertion-mount component is fixed to the paper substrate. Through the thermal curing process, the number of thermal processes may be reduced from two to one.

[0032] To achieve the above or other purposes, a printed circuit board made of paper according to the present specification comprises: a paper substrate having pores formed therein; a thin film land formed by printing a conductive material on the paper substrate; and at least one slot structure of a groove or hole formed in the paper substrate corresponding to an area where the thin film land is formed. While printing the thin film land with the conductive material, the conductive material is absorbed into the inside of the slot structure of the paper substrate and into pores adjacent to the slot structure, thereby improving the adhesion of the thin film land.

[0033] According to an embodiment, the thin film land may be composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, or a third conductive paste made of Ti material.

[0034] According to an embodiment, the slot structure may be composed of a plurality of grooves formed spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate may be formed to be thicker than the thickness of the grooves.

[0035] According to an embodiment, the slot structure may be composed of a plurality of holes formed spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0036] According to an embodiment, the slot structure may be formed as a cross structure of a plurality of grooves and holes that are alternately formed and spaced apart in one axial direction of the paper substrate. The thickness of the paper substrate may be formed to be thicker than the thickness of the grooves. The thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0037] According to an embodiment, the slot structure within the paper substrate may be electrically connected to the thin film land. The at least one groove or hole may be configured as a single or multiple grooves in a circular, linear, cross-shaped, rectangular, or polygonal structure.

[0038] According to an embodiment, the printed circuit board may further include wiring formed by printing a conductive material on a first surface of the paper substrate and configured to be connected to a surface mount device disposed on the paper substrate. The printed circuit board may further include a through hole formed to penetrate the thin film land.

[0039] According to an embodiment, the printed circuit board may further include an insert mount device configured to be inserted through the first side and the second side of the paper substrate through the thin film land. The surface mount device may be positioned between the boundary of the thin film land and the wiring. After the insert mount device is fixed to the paper substrate, the insert mount device and the surface mount device may be thermally cured together, thereby reducing the number of thermal processes from two to one.

[0040] According to an embodiment, the insertion mounting component can be fixed by bonding to the area where the through hole is formed. The printed circuit board may further include a second conductive adhesive layer formed by applying it to the second surface of the paper substrate corresponding to the area where the insertion mounting component is bonded.

[0041] According to an embodiment, the printed circuit board may further include a first conductive adhesive layer formed in an area adjacent to the through hole on the first surface of the paper substrate. The first conductive adhesive layer may be formed on the upper surface and side surfaces of the thin film land and a portion of the side surfaces of the through hole.

[0042] According to an embodiment, the printed circuit board may include a plurality of light-emitting devices (LEDs) spaced apart from each other in a uniaxial direction on the paper substrate; a plurality of resistors spaced apart from each other in a uniaxial direction between the plurality of light-emitting devices; a power line formed in the uniaxial direction in an upper region of the plurality of light-emitting devices and the plurality of resistors and branched to be connected to a first light-emitting device and a third light-emitting device; and a ground line formed in the uniaxial direction in a lower region of the plurality of light-emitting devices and the plurality of resistors and branched to be connected to a second light-emitting device and a fourth light-emitting device. The resistance values ​​of the resistors may be formed to have different values.

[0043] According to an embodiment, the power line may be connected to the first light-emitting element and the third light-emitting element, which are closer than the second light-emitting element and the fourth light-emitting element among the plurality of light-emitting elements. The ground line may be connected to the second light-emitting element and the fourth light-emitting element, which are further away than the first light-emitting element and the third light-emitting element among the plurality of light-emitting elements.

[0044] According to an embodiment, the printed circuit board may include a plurality of light-emitting elements spaced apart in a uniaxial direction on the paper substrate; a plurality of resistors spaced apart in the uniaxial direction between the plurality of light-emitting elements; a power line formed in the uniaxial direction in an upper region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to first and third light-emitting elements; a first ground line formed in the uniaxial direction in a lower region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to second and fourth light-emitting elements; and a second ground line connected to one end of the first ground line, arranged parallel to the first ground line, and having an end connected to a ground terminal of a connector. The other end of the first ground line may be formed spaced apart from the connector.

[0045] According to another aspect of the present disclosure, a method for manufacturing a printed circuit board made of paper includes a slot structure forming process for forming a slot structure of at least one groove or hole in a paper substrate having pores formed therein; and a thin film land forming process for forming a thin film land by printing a conductive material on the paper substrate to correspond to an area where the groove or hole is formed. In the thin film land forming process, while printing the thin film land with the conductive material, the conductive material is absorbed into the interior of the slot structure and pores adjacent to the slot structure, thereby improving the adhesion of the thin film land.

[0046] According to an embodiment, the thin film land may be composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, and a third conductive paste made of Ti material.

[0047] According to an embodiment, the slot structure forming process may include a plurality of groove forming processes for forming a plurality of grooves spaced apart in one axial direction of the paper substrate. In the plurality of groove forming processes, the thickness of the paper substrate may be formed to be thicker than the thickness of the grooves.

[0048] According to an embodiment, the slot structure forming process may include a plurality of hole forming processes for forming a plurality of holes spaced apart in one axial direction of the paper substrate. In the plurality of hole forming processes, the thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0049] According to an embodiment, the slot structure forming process may include a plurality of groove and hole forming processes in which grooves and holes are alternately formed while being spaced apart in one axial direction of the paper substrate. In the plurality of groove and hole forming processes, the thickness of the paper substrate may be formed to be thicker than the thickness of the grooves, and the thickness of the paper substrate and the thickness of the holes may be formed to be the same.

[0050] According to an embodiment, at least one groove or hole within the paper substrate may be electrically connected to the thin film land. The at least one groove or hole may be configured as a single or multiple grooves in a circular, linear, cross-shaped, rectangular, or polygonal structure.

[0051] According to an embodiment, the manufacturing method may further include a wiring forming process for forming wiring between the slot structure forming process and the thin film land forming process. The manufacturing method may further include a through hole forming process for forming a through hole to pass through the thin film land after the thin film land forming process. In the wiring forming process, the wiring may be formed by printing a conductive material on a first surface of the paper substrate and connected to a surface mount device placed on the paper substrate.

[0052] According to an embodiment, the manufacturing method may further include an insertion-mount component mounting process in which an insertion-mount component is inserted through the first side and the second side of the paper substrate through the thin film land after the through-hole forming process. The manufacturing method may further include a surface-mount component placement process in which a surface-mount component is placed between a boundary of the thin film land and the wiring. The manufacturing method may further include a thermal curing process in which the insertion-mount component and the surface-mount component are thermally cured together after the insertion-mount component is fixed to the paper substrate. Through the thermal curing process, the number of thermal processes may be reduced from two to one.

[0053] Figure 1 shows a cross-sectional view and a partially enlarged view of a paper substrate on which wiring and thin film lands are formed.

[0054] Figure 2 shows a printed circuit board made of paper material with grooves formed on the paper substrate at a predetermined thickness.

[0055] Figure 3 is a graph showing the change in volume according to the increase in temperature applied to paper materials.

[0056] Figure 4 shows a conceptual diagram showing separation of a paper substrate and a thin film land due to shrinkage of the paper substrate as temperature increases.

[0057] FIG. 5 illustrates cross-sectional views of a paper substrate to prevent delamination by a home structure, a hole structure, or a combination thereof according to embodiments.

[0058] Figure 6 shows the state before and after the conductive material is absorbed into the paper substrate by capillary phenomenon.

[0059] Figure 7 compares the cross-cut test results of a thin film printed on a paper substrate without holes with the cross-cut test results of a thin film printed on a paper substrate with holes formed therein.

[0060] Figure 8 shows a cross-sectional view of a paper substrate at each stage of a land formation method for improving adhesive strength in a printed circuit board made of paper material.

[0061] Figure 9 shows the structure of thin film lands of various shapes according to embodiments.

[0062] Figure 10 is a conceptual diagram showing the component mounting and process sequence of the PCB.

[0063] Figure 11 shows a cross-sectional view of each process of a method for manufacturing a printed circuit board made of paper.

[0064] Fig. 12 shows the structure of a conductive adhesive layer formed on a thin film land through the dispensing process of Fig. 11.

[0065] Figure 13 shows a cross-sectional view of each process of a method for manufacturing a printed circuit board made of paper material implemented through a single thermal process.

[0066] Figure 14 shows a structure in which multiple electronic components are arranged on a printed circuit board made of paper material.

[0067] Fig. 15 shows an equivalent circuit that takes into account the wiring resistance of the printed circuit board made of paper material of Fig. 14.

[0068] Figure 16 is a graph comparing the current values ​​of each LED string for a general substrate structure, a paper substrate structure, and a structure with changed resistance values ​​for the paper substrate.

[0069] Figure 17 is a structure that maintains the same resistance value for each LED string and forms multiple current directions in the ground line.

[0070] Fig. 18 shows an equivalent circuit for the structure of Fig. 17.

[0071] Figure 19 compares the current values ​​of each LED string for the ground line structure of Figure 14 and the ground line structure of Figure 17.

[0072] Figure 20 shows a flow chart of a method for manufacturing a printed circuit board made of paper.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0077] 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.

[0078] Below, a detailed description is given of a printed circuit board made of paper and a method for manufacturing the same according to the present disclosure. The present disclosure describes a method for manufacturing a PCB using a paper substrate, a representative environmentally friendly material, as the substrate material, and a wiring process using a printing method that does not use chemicals.

[0079] In this regard, Fig. 1 shows a cross-sectional view and a partially enlarged view of a paper substrate on which wiring and thin film lands are formed. Fig. 1(a) shows a cross-sectional view of a paper substrate (1010) on which upper wiring (1110) and thin film lands (1130) are formed. Fig. 1(b) shows a cross-sectional view of a paper substrate (1010) on which upper wiring (1110) and thin film lands (1130) are formed.

[0080] Referring to FIG. 1, a wiring (1100) and a thin film land (1130) may be formed on the upper surface of a paper substrate (1010). The wiring (1100) and / or the thin film land (1130) may be formed on the paper substrate (1010) to implement a printed circuit board (PCB) (1000) made of paper. The thin film land (1130) may be implemented as a metal pad. Electronic components may be placed between the thin film land (1130) implemented as first and second metal pads (MP1, MP2).

[0081] Meanwhile, Fig. 2 shows a printed circuit board made of paper material in which grooves of a predetermined thickness are formed on a paper substrate. Fig. 2(a) shows a cross-sectional view of a PCB (1000) in which grooves (1010g) of a predetermined thickness are formed on a paper substrate (1010). The thickness (h1) of the paper substrate (1010) is formed thicker than the thickness (h2) of the grooves (1010g). Fig. 2(b) shows a cross-sectional view of a PCB (1000) in which a conductive material of a thin film land (1130) is absorbed into a pore area adjacent to the grooves of the paper substrate (1010).

[0082] Referring to FIGS. 2(a) and 2(b), the shape of the absorption regions (1010R) in which the conductive material is absorbed may be formed differently from the shape of the grooves (1010g). The conductive material is accommodated in the grooves (1010g) of the paper substrate (1010) and penetrates into the pores adjacent to the grooves (1010g). Therefore, the width (volume) of the absorption regions (1010R) in which the conductive material is absorbed may be formed wider than the width (volume) of the grooves (1010g). Accordingly, the second width (W2) of the absorption regions (1010R) in which the conductive material is absorbed may be formed wider than the first width (W1) of the grooves (1010g).

[0083] Referring to FIGS. 1 and 2, a thin film land (1130) and absorption regions (1010R) will be described. In order to improve the adhesion between the thin film land (1130) formed on the paper substrate (1010) by a printing process and the paper substrate (1010), micro holes or grooves (1010g) may be provided in the thin film land (1130) portion of the paper substrate (1130). When silver paste (Ag paste), which is a printing wiring material, is printed on the thin film land (1130), it may penetrate into the paper substrate (1010) by a capillary phenomenon. We would like to propose a manufacturing method in which the adhesion between the paper and the land increases as a conductive material such as silver paste penetrates into the paper substrate (1010).

[0084] In addition, in the method of mounting components on a paper substrate (1010), a method is proposed that can replace the wave soldering process for insert-mounted components and reduce the number of thermal processes, thereby reducing lead time and energy consumption. Meanwhile, when the structure and process of the present disclosure are applied to high-intensity lighting products such as refrigerators, the wiring resistance of the paper substrate (1010) increases compared to the existing FR-4 substrate. In the present disclosure, a method is additionally proposed that can improve the LED current deviation that occurs due to the increased wiring resistance caused by the paper substrate (1010).

[0085] Meanwhile, Printed Circuit Boards (PCBs), a core component of all electronic products, consist of a thin copper plate bonded to epoxy. To form circuit wiring, the wiring is created by etching the unnecessary copper. This manufacturing process requires numerous etching chemicals and numerous processes. Specifically, the PCB manufacturing process can include exposure, development, etching, and stripping. Due to these processes, the increasing demand for electronic products has led to an increase in electronic waste, including PCBs, and thus, environmental pollutants. Therefore, research into eco-friendly substrate materials and chemical-free manufacturing processes is needed to improve emissions.

[0086] Meanwhile, the thin film land is where circuit elements are attached. To maintain product performance after the circuit elements are mounted, the circuit elements must remain firmly fixed to the PCB even when subjected to external forces (e.g., temperature changes). In particular, when using a paper substrate, the length of the paper substrate and metal wiring changes with temperature, compared to conventional PCBs. In this regard, Figure 3 is a graph showing volume changes in paper materials as a function of temperature.

[0087] Referring to Figure 3, paper materials have the unique characteristic of decreasing in volume (length) as temperature increases. In this regard, all paper materials, including art paper, copy paper, kraft paper, and corrugated cardboard, exhibit a decrease in volume as temperature increases. Meanwhile, as the thickness of the paper material increases, such as kraft paper and corrugated cardboard, the volume decreases further. This characteristic is due to the evaporation of moisture contained in the paper material, resulting in a decrease in volume. Meanwhile, silver paste, a conductive material, exhibits a characteristic of increasing in volume (length) as temperature increases, and silver has a coefficient of thermal expansion of 19 ppm / ℃.

[0088] Due to the temperature-dependent characteristics of FIG. 3, different external forces may be generated on the paper substrate as the temperature increases. In this regard, FIG. 4 illustrates a conceptual diagram of separation between the paper substrate and the thin film land due to shrinkage of the paper substrate as the temperature increases. Referring to FIG. 4, an external force that causes the paper substrate (1010) to shrink in a uniaxial direction may be generated as the temperature increases.

[0089] Meanwhile, an external force different from the external force generated on the paper substrate (1010) may be generated on the thin film land (1130). As the temperature rises, an external force (F1) may be generated on the paper substrate (1010), so that the paper substrate (1010) may be reduced in length by a first length (L1) on both sides in the uniaxial direction. As the temperature rises, an external force (F2) may be generated on the thin film land (1130), so that the thin film land (1130) may be increased in length by a second length (L2) on both sides in the uniaxial direction. Therefore, different external forces (F1, F2) may be generated on the paper substrate (1010) and the thin film land (1130). A peeling phenomenon may occur in which the paper substrate (1010) and the thin film land (1130) are separated due to the different external forces (F1, F2).

[0090] As described above, a groove structure or a hole structure may be introduced into the paper substrate (1010) to prevent a peeling phenomenon in which the paper substrate (1010) and the thin film land (1130) are separated by different external forces. FIG. 5 illustrates cross-sectional views of a paper substrate to prevent a peeling phenomenon by a groove structure, a hole structure, or a combination thereof according to embodiments.

[0091] Referring to FIG. 5(a), a plurality of grooves (1100g) may be formed on a paper substrate (1010) spaced apart from each other in one axial direction. The plurality of grooves (1010g) may be formed spaced apart from each other not only in the illustrated axial direction but also in another axial direction orthogonal to the axial direction. The thickness (h1) of the paper substrate (1010) may be formed thicker than the thickness (h2) of the grooves (1010g). Meanwhile, the paper substrate (1010) may include a first paper layer and a second paper layer laminated on a lower portion of the first paper layer. An adhesive layer may be formed between the first paper layer and the second paper layer. The plurality of grooves (1010g) may be formed on the first paper layer on the upper portion of the paper substrate (1010). The thickness of the first paper layer may be formed to be the same as the thickness (h2) of the plurality of grooves (1010g).

[0092] Referring to FIG. 5(b), a plurality of holes (1100h) may be formed spaced apart in one axial direction on a paper substrate (1010). The plurality of holes (1100h) may be formed spaced apart not only in the illustrated axial direction but also in another axial direction orthogonal to the axial direction. The thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0093] Referring to FIG. 5(c), grooves (1100g) and holes (1100h) may be formed alternately and spaced apart in one axial direction on a paper substrate (1010). The grooves (1100g) and holes (1100h) may be formed spaced apart not only in the illustrated axial direction but also in another axial direction orthogonal to the axial direction. The paper substrate (1010) may include a first paper layer and a second paper layer laminated on a lower side of the first paper layer. An adhesive layer may be formed between the first paper layer and the second paper layer. A plurality of grooves (1010g) may be formed in the first paper layer on the upper side of the paper substrate (1010). The thickness of the first paper layer may be formed to be the same as the thickness (h2) of the plurality of grooves (1010g). The thickness (h1) of the paper substrate (1010) may be formed to be thicker than the thickness (h2) of the grooves (1010g). The thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0094] In order to improve the weakening of the adhesive strength of the thin film land due to shrinkage of the paper substrate (1010), fine grooves (1100g) or grooves (1100h) may be formed at the bottom and around the thin film land. Referring to FIGS. 2 and 5, when the thin film land is printed with a conductive material such as silver paste, the paste is absorbed into the pores inside the paper substrate (1010) by a capillary phenomenon through the grooves (1010g) or holes (1010h). Therefore, the conductive material such as silver paste absorbed into the paper substrate (1010) combines with the thin film land (1130) to form an anchor structure that holds the thin film land (1130), thereby improving the adhesive strength of the thin film land.

[0095] In this regard, Fig. 6 shows a state before and after a conductive material is absorbed into a paper substrate by a capillary phenomenon. Referring to Fig. 6(a), a conductive material (1051) may be applied to a paper substrate (1010), such as cellulose. The conductive material (1051) may include a binder (1051a) and particles (1051b) that may be combined with the paper substrate (1010). The particles (1051b) of the conductive material (1051) implemented as a silver paste may be particles of a silver (Ag) material.

[0096] Referring to FIG. 6(b), particles (1051b) can penetrate into the pores of the paper substrate (1010). As shown in the enlarged view of a portion of FIG. 6(b), an absorption region (1010R) in which a conductive material is absorbed can be formed in the groove of the upper wiring (1110) or the lower portion of the thin film land (1130).

[0097] Meanwhile, a cross-cut test can be performed to evaluate the adhesion of the wiring and thin film structure of the paper substrate according to the present disclosure. In this regard, Fig. 7 compares the cross-cut test results of a thin film printed on a paper substrate without holes with the cross-cut test results of a thin film printed on a paper substrate with holes formed therein.

[0098] Figures 7(a) and 7(b) are front views of a thin film printed on a paper substrate without holes before and after a cross-cut test. Figures 7(c) and 7(d) are front views of a thin film printed on a paper substrate with holes before and after a cross-cut test. The cross-cut test is performed by cutting the printed thin film into a right-angled grid pattern to evaluate the adhesive strength of the printed land, then firmly attaching it with a test tape and then peeling it off.

[0099] Referring to FIGS. 7(a) and 7(b), the thin film printed on the paper substrate without holes is removed by peeling off the printed land in the first region (1010R1). Referring to FIGS. 7(c) and 7(d), the thin film printed on the paper substrate with holes is not peeled off in the first region. Therefore, the cross-cut test results show that the thin film printed after forming micro-holes on the paper substrate has improved adhesion and no peeled thin film occurs.

[0100] Meanwhile, the method for forming lands to improve adhesive strength in a paper-based printed circuit board according to the present disclosure can be achieved through a series of processes. In this regard, Fig. 8 illustrates a cross-sectional view of a paper substrate during each process of the method for forming lands to improve adhesive strength in a paper-based printed circuit board.

[0101] Referring to FIG. 5 and FIG. 8(a), grooves (1010g), holes (1010h), or a structure in which grooves (1010g) and holes (1010h) of a predetermined width are formed in a portion where a thin film land is to be formed on a porous paper substrate (1010). Processing of the grooves (1010g), holes (1010h), or a structure in which grooves (1010g) and holes (1010h) are combined can be implemented using a laser or a cutter, etc.

[0102] Referring to Fig. 8(b), a thin film land (1130) may be formed on the upper or lower surface of the paper substrate (1010) corresponding to the portion where the grooves (1010g) are formed. The thin film land (1130) may be implemented with various metal pastes other than silver paste, such as copper paste (Cu paste) or titanium paste (Ti paste). In addition to the thin film land (1130), an upper wiring may be formed on the upper surface of the paper substrate (1010), or a lower wiring may be formed on the lower surface.

[0103] Referring to Fig. 8(c), after a certain period of time has elapsed so that the conductive paste can be absorbed into the paper substrate (1010), absorption regions (1010R) can be formed. In this regard, when thermal curing is performed, the formation of a thin film land (1130) with improved adhesion to the paper substrate (1010) is completed. Referring to Figs. 8(a) and 8(c), the second width (W2) of the absorption regions (1010R) into which the conductive material is absorbed can be formed to be wider than the first width (W1) of the grooves (1010g).

[0104] Meanwhile, the thin film land for improving adhesive strength in the paper-based printed circuit board according to the present disclosure can be formed in various shapes. In this regard, FIG. 9 illustrates the structures of thin film lands of various shapes according to embodiments.

[0105] Referring to Fig. 9(a), the thin film land (1130) may be formed in a square shape, like the metal pads (MP1, MP2) of Fig. 1. Referring to Fig. 9(c), the thin film land (1130b) may be formed in a circular or polygonal shape.

[0106] Referring to FIG. 9(c), grooves (1011g, 1012g, 1013g, 1014g), holes (1011h, 1012h, 1013h, 1014h) or a combination thereof may be arranged inside a rectangular-shaped thin film land (1130).

[0107] Circular grooves (1011g) or holes (1011h) may be arranged adjacent to the center and four corner portions of the thin film land (1130). Rectangular grooves (1012g) or holes (1012h) may be arranged on one side, the other side, the upper and lower regions of the thin film land (1130). Rectangular ring-shaped grooves (1013g) or holes (1013h) may be formed spaced inward from the boundary of the thin film land (1130). Cross-shaped grooves (1014g) or holes (1014h) may be arranged adjacent to at least two corner portions of the thin film land (1130) or may be arranged at the center.

[0108] Referring to FIG. 9(d), grooves (1011g, 1012g, 1013g, 1014g), holes (1011h, 1012h, 1013h, 1014h) or a combination thereof may be arranged inside a thin film land (1130b) having a circular or polygonal shape.

[0109] Circular grooves (1011g) or holes (1011h) may be arranged adjacent to the center and four corner portions of the thin film land (1130b). Rectangular grooves (1012g) or holes (1012h) may be arranged on one side, the other side, the upper and lower regions of the thin film land (1130b). Rectangular ring-shaped grooves (1013g) or holes (1013h) may be formed spaced inward from the boundary of the thin film land (1130b). Cross-shaped grooves (1014g) or holes (1014h) may be arranged at the center of the thin film land (1130) or at two points on a line passing through the center.

[0110] Meanwhile, electronic components can be mounted on a printed circuit board made of paper according to the present disclosure. In this regard, PCBs, a key component of all electronic products, are structured by combining epoxy, fiberglass, and thin copper plates. This manufacturing method requires numerous processes, including the use of chemicals for etching the copper plates during the wiring process, and energy sources. Furthermore, the use of materials that do not readily decompose (epoxy and fiberglass) during PCB disposal generates significant environmental pollutants. To address this issue, the present disclosure can be used to create a PCB using paper, a representative eco-friendly material, as the substrate material.

[0111] However, due to the nature of the paper substrate material, mounting components on paper substrates is impossible using existing mounting processes and methods. Therefore, this disclosure proposes a component mounting method and process sequence suitable for paper substrates. Furthermore, it aims to simplify the process and reduce costs by simultaneously heat-treating both surface-mount and insert-mount components.

[0112] Meanwhile, types of electronic components include surface-mount devices (SMDs), which are mounted on the surface of a PCB board, and insert-mount devices (IMDs), which are mounted by drilling holes in the board and having the component leads penetrate the board. In this disclosure, we will primarily describe representative processes in which surface-mount and insert-mount components are mounted on a single-sided PCB with electrode wiring on only one side of the board.

[0113] Meanwhile, Fig. 10 is a conceptual diagram illustrating the component mounting and process sequence of a PCB. Referring to Fig. 10(a), solder (1041) is applied to the required location using screen printing on a PCB (1000b) in which an upper wiring (1110) and a thin film land (1130) are formed on a substrate (1010b).

[0114] Referring to Fig. 10(b), an adhesive (1042) for bonding surface-mount components is applied. The purpose of applying the adhesive (1042) is to perform the wave soldering process while the substrate is turned over when mounting insert-mount components later. This is to prevent surface-mount components that are mounted first from being separated from the substrate (1010b) by liquid lead during the wave soldering process.

[0115] Referring to Fig. 10(c), after applying an adhesive, a surface-mount component (1310) is placed using an automatic insertion device, and then heat is applied to the solder using a reflow device to mount the surface-mount component (1310) on the substrate (1010b). Referring to Fig. 10(d), the substrate (1010b) is turned over and the insertion-mount component (1320) is inserted. In addition, a wave soldering device is used to attach liquid solder (1041b) to the metal pad of the thin-film land (1130) so that the insertion-mount component (1320) can be electrically connected to the wiring of the PCB.

[0116] However, paper substrates can become deformed, including burn marks, at temperatures above 200°C. Therefore, low-temperature curing electrically conductive adhesives (ECAs) must be used. For surface-mount components, screen-printing conductive adhesives instead of solder is possible. However, wave soldering presents challenges due to the thermosetting nature of conductive adhesives and their viscosity.

[0117] To address the aforementioned issues, the processes of a method for manufacturing a paper-based printed circuit board according to the present disclosure are described. In this regard, Fig. 11 illustrates cross-sectional views of each process of the method for manufacturing a paper-based printed circuit board.

[0118] Referring to FIG. 11(a), a conductive adhesive layer (1151) of ECA material may be formed to attach a surface-mount component to a thin film land (1130) of a paper substrate (1010). A through hole (1100p) may be formed to place an insert-mount component in the paper substrate (1010).

[0119] Referring to Fig. 11(b), after applying a conductive adhesive layer (1151) of ECA material by screen printing, the reflow chamber temperature is lowered from the existing 250°C to 150°C so that the surface-mounted component (1310) can be mounted first. Referring to Fig. 11(c), a conductive adhesive is applied to the pad of the insert-mounted component through a dispensing process so that a first conductive adhesive layer (1152) is formed. Referring to Fig. 11(d), the paper substrate (1010) is turned over, the insert-mounted component (1320) is inserted, and curing is performed once more at a reflow chamber temperature of 150°C to complete the mounting of the insert-mounted component (1320).

[0120] Fig. 12 illustrates the structure of a conductive adhesive layer formed on a thin film land through the dispensing process of Fig. 11. Referring to Figs. 11 and 12, when applying a conductive adhesive before inserting an insert-mount component (1320) into a through hole (1100p), the conductive adhesive is applied inwardly of the through hole (1100p) for the purpose of increasing the contact area between the component lead and the conductive adhesive. Accordingly, a first conductive adhesive layer (1152) formed by applying the conductive adhesive can be formed on the upper surface (S1) and the side surface (S2) of the thin film land (1130) and a portion of the side surface (S3) of the through hole (1100p).

[0121] When dispensing, the conductive adhesive is dispensed further inward than the actual through-hole (1100p). This is to increase the contact area between the component leads and the conductive adhesive when inserting the insert-mounted component. Although the conductive adhesive is liquid, its viscosity is approximately 15,000 cps and it does not flow easily. Furthermore, even if the conductive adhesive does flow, it stops at the inner wall of the through-hole (1100p), which increases the contact area between the component leads and the conductive adhesive, thereby improving electrical properties.

[0122] In terms of process lead time and power consumption, the reflow and wave solder processes of FIGS. 12(b) and 12(d) increase power consumption due to heat, resulting in a longer lead time in proportion to the two thermal processes. Therefore, limiting the number of thermal processes for the paper substrate (1010) to one will be advantageous in terms of lead time and power consumption. Hereinafter, the processes of a method for manufacturing a paper-based printed circuit board implemented through a single thermal process will be described.

[0123] In this regard, Fig. 13 shows a cross-sectional view of each process of a method for manufacturing a printed circuit board made of paper material implemented through a single thermal process.

[0124] Referring to Fig. 13(a), an adhesive is applied using a dispenser device to secure the insertion mounting component, thereby forming a second conductive adhesive layer (1153) on the second surface, which is the lower surface of the paper substrate (1010). The second conductive adhesive layer (1153) may be formed near the boundary of the through hole (1100p).

[0125] Referring to Fig. 13(b), the insert-mount component (1320) is inserted into the through hole (1100p). To shorten the adhesive curing time, a UV irradiation process may be added using a UV-type adhesive. Referring to Fig. 13(c), since screen printing is not possible with the insert-mount component (1320) mounted, the pads of both the surface-mount component and the insert-mount component (1320) are applied together using a dispenser device.

[0126] Referring to Fig. 13(d), a conductive adhesive layer (1151) of ECA material may be formed at the end of the thin film land (1130). In addition, a first conductive adhesive layer (1152) of ECA material may be formed on the thin film land (1130) corresponding to the boundaries of the bottom of the through hole. After the surface mount components (1310) are placed so as to be connected to the end of the thin film land (1130) and the reflow chamber is operated at 150°C, all electronic components can be cured in a single thermal process. However, if the manufacturing process of Fig. 13 is applied to existing reflow equipment and conveyor chains, problems such as warping of the drive board or interference due to the height of the components may occur in the case of heavy and large insert-mount components. Therefore, when the process is performed using existing equipment infrastructure, surface mount components and insert-mount components that are below the critical weight or below the critical size must be used.

[0127] Meanwhile, a plurality of electronic components may be arranged on a printed circuit board made of paper according to the present disclosure. In this regard, Fig. 14 illustrates a structure in which a plurality of electronic components are arranged on a printed circuit board made of paper. Fig. 15 illustrates an equivalent circuit considering the wiring resistance of the printed circuit board made of paper of Fig. 14. Fig. 16 is a graph comparing the current values ​​of each LED string for a general substrate structure, a paper substrate structure, and a structure in which the resistance value for the paper substrate is changed.

[0128] Referring to FIG. 14, a printed circuit board (PCB) (1000) may be configured to include a plurality of light emitting devices (LEDs) (1410) and a plurality of resistors (1420). The plurality of light emitting devices (1410) may be arranged to be spaced apart in one axial direction on a paper substrate (1010). The plurality of resistors (1420) may be arranged to be spaced apart in one axial direction between the plurality of light emitting devices (1410). The plurality of light emitting devices (1410) may include first to fourth light emitting devices (1411, 1412, 1413, 1414). The plurality of resistors (1420) may include a first resistor (1421) positioned between the first and second light-emitting elements (1411, 1412) and a second resistor (1422) positioned between the third and fourth light-emitting elements (1413, 1414).

[0129] A printed circuit board (PCB) (1000) may be configured to further include a power line (1430), a ground line (1440a), and a connector (1450). The power line (1430) may be arranged in an upper region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420), and may be formed in one axial direction. The power line (1430) may be branched to be connected to first and third light-emitting elements (1411, 1413) among the plurality of light-emitting elements (1410).

[0130] A ground line (1440a) may be arranged in an upper region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420), and may be formed in one axial direction. The ground line (1440a) may be branched to be connected to the second and fourth light-emitting elements (1412, 1414) among the plurality of light-emitting elements (1410). A connector (1450) may be connected to one end of a power line (1430) and the ground line (1440a), and may apply voltage to the power line (1430).

[0131] Specifically, a voltage of 12 V is applied to a power line (1430), and current is applied in parallel to six LED strings. First and second light-emitting elements (1411, 1412) and a first resistor (1421) can constitute a first LED string. Third and fourth light-emitting elements (1413, 1414) and a second resistor (1422) can constitute a second LED string. Therefore, each LED string has two LEDs and one resistor connected in series, and the amount of current flowing to the LED is controlled by the resistance value of one resistor. Therefore, one resistor between the two LEDs acts as a current-limiting resistor.

[0132] In one embodiment, an LED 5630 package may be used as a plurality of light-emitting elements (1410), and a 100-ohm resistor of size 3216 may be connected as a plurality of resistors (1420). By connecting a 100-ohm resistor, light is emitted while satisfying the representative current value of the LED, which is approximately 60 mA. However, when a paper substrate and printed wiring are used, the wiring resistance increases compared to the copper electrode due to the material properties of the printed wiring.

[0133] Referring to FIGS. 14 and 15, a first wiring resistance (1430R) of a power line (1430) and a second wiring resistance (1440R) of a ground line occur in a printed circuit board made of paper. A current drop and a current deviation (luminance deviation) between each LED string occur due to the first wiring resistance (1430R) of the power line (1430) and the second wiring resistance (1440R) of the ground line. The first wiring resistance (1430R) has a value of 0.8 ohm for each LED string. The second wiring resistance (1440R) has a value of 0.8 ohm for each LED string.

[0134] Referring to FIGS. 14 to 16, in a general substrate structure such as FR4, the current value of each LED string is the same as 62.7 mA. Meanwhile, in a paper substrate structure, the current value of each LED string monotonically decreases to 59.1, 55.1, 52, 49.7, 48.2, and 47.5 mA. Meanwhile, in order to reduce the current deviation of each LED string in the paper substrate structure, the resistance values ​​of the plurality of resistors (1420) may be designed to be different. In order to reduce the current deviation, the resistance values ​​of the plurality of resistors (1420) may be configured as 93, 85, 79, 74, 71, and 69 ohms. The current values ​​of each LED string for the structure in which the resistance value for the paper substrate is changed have values ​​of 62.6, 62.6, 62.3, 62.5, 62.3, and 62.7 mA. Therefore, we have a negligible current deviation of less than 0.4 mA for the six LED strings.

[0135] Meanwhile, although the current deviation in the paper substrate structure can be reduced by changing the resistance value of each LED string differently, there are issues of implementing the exact resistance value and increasing the design complexity. Therefore, Fig. 17 shows a structure that maintains the same resistance value for each LED string and forms multiple current directions in the ground line. Fig. 18 shows an equivalent circuit for the structure of Fig. 17. Fig. 19 compares the current values ​​of each LED string for the ground line structure of Fig. 14 and the ground line structure of Fig. 17.

[0136] Referring to FIG. 17, a printed circuit board (PCB) (1000) may be configured to further include a plurality of light-emitting elements (1410), a plurality of resistors (1420), a power line (1430), a ground line (1440), and a connector (1450). The plurality of light-emitting elements (1410) may be arranged to be spaced apart from each other in one axial direction on the paper substrate (1010). The plurality of resistors (1420) may be arranged to be spaced apart from each other in one axial direction between the plurality of light-emitting elements (1410). The plurality of light-emitting elements (1410) may include first to fourth light-emitting elements (1411, 1412, 1413, 1414). The plurality of resistors (1420) may include a first resistor (1421) positioned between the first and second light-emitting elements (1411, 1412) and a second resistor (1422) positioned between the third and fourth light-emitting elements (1413, 1414).

[0137] The power line (1430) is arranged in an upper region in the Y-axis direction of the plurality of light-emitting elements (1410) and the plurality of resistors (1420), and may be formed in one axial direction. The power line (1430) may be branched to be connected to the first and third light-emitting elements (1411, 1413) among the plurality of light-emitting elements (1410).

[0138] The ground line (1440) may be configured to include a first ground line (1440a) and a second ground line (1440b). The first ground line (1440a) may be arranged in an upper region in the Y-axis direction of the plurality of light-emitting elements (1410) and the plurality of resistors (1420), and may be formed in one axial direction. The first ground line (1440a) may be branched to be connected to the second and fourth light-emitting elements (1412, 1414) among the plurality of light-emitting elements (1410). The second ground line (1440b) may be arranged parallel to the first ground line (1440a). The direction of the first current on the first ground line (1440a) and the direction of the second current on the second ground line (1440b) are formed in opposite directions. The connector (1450) is connected to one end of the power line (1430) and the second ground line (1440b), and can apply voltage to the power line (1430). The end of the first ground line (1440a) can be formed spaced apart from and not connected to the connector (1450).

[0139] Meanwhile, the first ground line (1440a) and the second ground line (1440b) may be disposed on the same plane of the paper substrate (1010) or may be disposed on the upper and lower surfaces of the paper substrate (1010). Referring to FIG. 17(a), the first ground line (1440a) and the second ground line (1440b) may be disposed on the same plane of the paper substrate (1010). The ground line (1440) may further include a third ground line (1440c) configured to connect an end of the first ground line (1440a) and an end of the second ground line (1440b). The third ground line (1440c) may be formed perpendicular to the first ground line (1440a) and the second ground line (1440b).

[0140] Figures 17(b) and 17(c) illustrate the upper and lower surfaces of the paper substrate (1010). Referring to Figures 17(b) and 17(c), the first ground line (1440a) and the second ground line (1440b) may be respectively arranged on one or the other of the upper and lower surfaces of the paper substrate (1010). A via hole (1100v) may be formed adjacent to an end of the first ground line (1440a) and an end of the second ground line (1440b). The other end of the first ground line (1440a) or the other end of the second ground line (1440b) may be coupled to a connector (1450) on one side of the paper substrate (1010).

[0141] Referring to FIGS. 17 and 18, a first wiring resistance (1430R) of a power line (1430) and a second wiring resistance (1440R1) of a first ground line (1440a) are generated in a printed circuit board made of paper. In addition, a third wiring resistance (1440R2) of a second ground line (1440b) is generated. The first wiring resistance (1430R) has a value of 0.8 ohm for each LED string. The second wiring resistance (1440R1) has a value of 0.8 ohm for each LED string. The third wiring resistance (1440R2) has a value of 4 ohm for the entire length.

[0142] The current deviation due to the first wiring resistance (1430R) of the power line (1430) and the second wiring resistance (1440R1) of the first ground line (1440a) can be compensated by the third wiring resistance (1440R2) of the second ground line (1440b). Therefore, the current deviation due to the first wiring resistance (1430R), the second wiring resistance (1440R1), and the third wiring resistance (1440R2) is reduced as illustrated in FIG. 19.

[0143] Referring to FIGS. 14, 15, and 19, the current values ​​of each LED string in the paper substrate structure monotonically decrease to 59.1, 55.1, 49.7, 48.2, and 47.5 mA. Referring to FIGS. 17 to 19, the current values ​​of each LED string compensated by the third wiring resistor (1440R2) of the second ground line (1440b) have values ​​of 64.7, 61.6, 60.1, 61.6, and 64.7 mA. Therefore, the deviation of the current values ​​of each LED string compensated by the third wiring resistor (1440R2) of the second ground line (1440b) has a deviation value of 4.6 mA or less. Therefore, the six LED strings have a negligible current deviation of 4.6 mA or less.

[0144] The above has described a printed circuit board made of paper according to the present disclosure and a method for manufacturing the same. Below, a printed circuit board (PCB) (1000) made of paper according to one aspect of the present disclosure will be described with reference to FIGS. 1 to 19.

[0145] A printed circuit board (PCB) (1000) made of paper material can be configured to include a paper substrate (1010), a thin film land (1130), and a slot structure (1010s). The paper substrate (1010) can have pores formed therein. The thin film land (1130) can be formed by printing a conductive material on the paper substrate (1010). The slot structure (1010s) can be implemented as at least one groove (1010g) or hole (1010h) formed in the paper substrate (1010) corresponding to an area where the thin film land (1130) is formed.

[0146] When printing a thin film land (1130) with a conductive material, the conductive material may be absorbed into the interior of a slot structure (1010s) of a paper substrate (1010) and into pores adjacent to the slot structure (1010s), thereby improving the adhesion of the thin film land (1130). The conductive material may be absorbed into the interior of at least one groove (1010g) or hole (1010h) of a paper substrate (1010) and into pores adjacent thereto, thereby improving the adhesion of the thin film land (1130). The conductive material absorbed into the slot structure (1010s) and the pores adjacent to the slot structure (1010s) forms absorption regions (1010R). The thin film land (1130) may be composed of a first conductive paste made of an Ag material, a second conductive paste made of a Cu material, or a third conductive paste made of a Ti material.

[0147] The slot structure (1010s) may be composed of a plurality of grooves (1010g) formed spaced apart in one axial direction of the paper substrate (1010). The thickness (h1) of the paper substrate (1010) may be formed thicker than the thickness (h2) of the grooves (1010g).

[0148] The slot structure (1010s) may be composed of a plurality of holes (1010h) formed spaced apart in one axial direction of the paper substrate (1010). The thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0149] The slot structure (1010s) may be formed as a cross structure of a plurality of grooves (1010g) and holes (1010h) that are spaced apart and alternately formed in one axial direction of the paper substrate (1010). The thickness (h1) of the paper substrate (1010) may be formed to be thicker than the thickness (h2) of the grooves (1010g). The thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0150] The slot structure (1010s) inside the paper substrate (1010) can be electrically connected to the thin film land (1130). At least one groove (1010g) or hole (1010h) can be configured as a single or multiple in a circular, linear, cross-shaped, square, or polygonal structure.

[0151] A printed circuit board (PCB) (1000) made of paper material may be configured to further include a wiring (1100). The printed circuit board (PCB) (1000) made of paper material may be configured to further include a through hole (1100p). The wiring (1100) may be formed by printing a conductive material on a first surface or a second surface of the paper substrate (1010). An upper wiring (1110) may be formed by printing a conductive material on the first surface of the paper substrate (1010). The wiring (1100) may be configured to be connected to a surface mount device (1310) disposed on the paper substrate (1010). The through hole (1100p) may be formed to penetrate a thin film land (1130).

[0152] A printed circuit board (PCB) (1000) made of paper material may further include an insert mount device (1320). The insert mount device (1320) may be configured to be inserted through the first and second surfaces of the paper substrate (1010) through thin film lands (1130). The surface mount device (1310) may be positioned between the boundary of the thin film lands (1130) and the wiring (1100). After the insert mount device (1320) is fixed to the paper substrate (1010), the insert mount device (1320) and the surface mount device (1310) may be heat-cured together, thereby reducing the number of heat processes from two to one.

[0153] An insert-mount component (1320) can be fixed by bonding to an area where a through hole (1100p) is formed. A printed circuit board (PCB) (1000) made of paper material can be configured to further include a second conductive adhesive layer (1153). The second conductive adhesive layer (1153) can be formed by applying it to a second surface of the paper substrate (1010) corresponding to the area where the insert-mount component (1320) is bonded.

[0154] A printed circuit board (PCB) (1000) made of paper material may be configured to further include a conductive adhesive layer (1151). A first conductive adhesive layer (1152) may be formed in an area adjacent to a through hole (1100p) on a first surface of the paper substrate (1010). The first conductive adhesive layer (1152) may be formed on a top surface (S1) and a side surface (S2) of a thin film land (1130) and a portion of a side surface (S3) of the through hole (1100p).

[0155] A printed circuit board (PCB) (1000) made of paper material can be configured to include a plurality of light emitting devices (LEDs) (1410), a plurality of resistors (1420), a power line (1430), and a ground line (1440a). The plurality of light emitting devices (1410) can be arranged spaced apart in one axial direction on the paper substrate (1010). A plurality of resistors (1420) can be arranged spaced apart in one axial direction between the plurality of light emitting devices (1410).

[0156] A power line (1430) may be formed in the X-axis direction, which is one axial direction, in an upper region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420). The power line (1430) may be branched to be connected to a first light-emitting element (1411) and a third light-emitting element (1413). A ground line (1440a) may be formed in the X-axis direction, which is one axial direction, in a lower region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420). The ground line (1440a) may be branched to be connected to a second light-emitting element (1412) and a fourth light-emitting element (1414). The resistance values ​​of the plurality of resistors (1420) may be configured to have different values. The resistance values ​​of the plurality of resistors (1420) may be configured to decrease as they get farther away from a point where voltage is applied to the power line (1430).

[0157] The power line (1430) may be connected to the first light-emitting element (1411) and the third light-emitting element (1413) which are closer than the second light-emitting element (1412) and the fourth light-emitting element (1414) among the plurality of light-emitting elements (1410). The ground line (1440a) may be connected to the second light-emitting element (1412) and the fourth light-emitting element (1414) which are further away than the first light-emitting element (1411) and the third light-emitting element (1413) among the plurality of light-emitting elements (1410).

[0158] A printed circuit board (PCB) (1000) made of paper material can be configured to include a plurality of light emitting devices (LEDs) (1410), a plurality of resistors (1420), a power line (1430), a first ground line (1440a), and a second ground line (1440b). The plurality of light emitting devices (1410) can be arranged spaced apart from each other in a uniaxial direction on the paper substrate (1010). A plurality of resistors (1420) can be arranged spaced apart from each other in a uniaxial direction between the plurality of light emitting devices (1410).

[0159] A power line (1430) may be formed in the X-axis direction, which is one axial direction, in an upper region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420). The power line (1430) may be branched to be connected to a first light-emitting element (1411) and a third light-emitting element (1413). A first ground line (1440a) may be formed in the X-axis direction, which is one axial direction, in a lower region in the Y-axis direction of a plurality of light-emitting elements (1410) and a plurality of resistors (1420). The first ground line (1440a) may be branched to be connected to a second light-emitting element (1412) and a fourth light-emitting element (1414). The second ground line (1440b) may be connected to one end of the first ground line (1440a). The second ground line (1440b) may be arranged parallel to the first ground line (1440a). An end of the second ground line (1440b) may be connected to a ground terminal of the connector (1450). The other end of the first ground line (1440a) may be formed to be spaced apart from the connector (1450).

[0160] The above describes a printed circuit board made of paper according to one aspect of the present disclosure. Below, a method for manufacturing a printed circuit board made of paper according to another aspect of the present disclosure will be described. In this regard, the configuration and operation of FIGS. 1 to 19 and the configuration and operation of a printed circuit board made of paper according to one aspect of the present disclosure can be applied to a method for manufacturing a printed circuit board. FIG. 20 illustrates a flowchart of a method for manufacturing a printed circuit board made of paper.

[0161] Hereinafter, a method for manufacturing a printed circuit board (1000) made of paper according to another aspect of the present disclosure will be described with reference to FIGS. 1 to 20. The method for manufacturing a printed circuit board (1000) may be configured to include a slot structure forming process (S100) and a thin film land forming process (S200).

[0162] In the slot structure forming process (S100), a slot structure (1010s) having at least one groove (1010g) or hole (1010h) can be formed on a paper substrate (1010) having pores formed therein. In the thin film land forming process (S200), a thin film land (1130) can be formed by printing a conductive material on the paper substrate (1010) to correspond to the area where the groove (1010g) or hole (1010h) is formed. During the printing of the thin film land (1130) with the conductive material in the thin film land forming process (S200), the conductive material can be absorbed into the interior of the slot structure (1010s) of the paper substrate (1010) and the pores adjacent to the slot structure (1010s), thereby improving the adhesion of the thin film land (1130). A conductive material may be absorbed into the interior of at least one groove (1010g) or hole (1010h) of a paper substrate (1010) and pores adjacent thereto, thereby improving the adhesion of a thin film land (1130). The conductive material absorbed into the slot structure (1010s) and the pores adjacent to the slot structure (1010s) forms absorption regions (1010R). The thin film land (1130) may be composed of a first conductive paste made of an Ag material, a second conductive paste made of a Cu material, or a third conductive paste made of a Ti material.

[0163] The slot structure forming process (S100) may include a plurality of groove forming processes (S110). In the plurality of groove forming processes (S110), a plurality of grooves (1010g) spaced apart in one axial direction of the paper substrate (1010) may be formed. In the plurality of groove forming processes (S110), the thickness (h1) of the paper substrate (1010) may be formed to be thicker than the thickness (h2) of the grooves (1010g).

[0164] The slot structure forming process (S100) may include a plurality of hole forming processes (S120). In the plurality of hole forming processes (S120), a plurality of holes (1010h) may be formed spaced apart from each other in one axial direction of the paper substrate (1010). In the plurality of hole forming processes (S120), the thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0165] The slot structure forming process (S100) may include a plurality of groove and hole forming processes (S130). In the plurality of groove and hole forming processes (S130), a plurality of grooves (1010g) and holes (1010h) may be formed in an alternating structure spaced apart from each other in one axial direction of the paper substrate (1010). In the plurality of groove and hole forming processes (S130), a thickness (h1) of the paper substrate (1010) may be formed to be thicker than a thickness (h2) of the grooves (1010g). The thickness (h1) of the paper substrate (1010) and the thickness (h1) of the holes (1010h) may be formed to be the same.

[0166] The slot structure (1010s) inside the paper substrate (1010) can be electrically connected to the thin film land (1130). At least one groove (1010g) or hole (1010h) can be configured as a single or multiple in a circular, linear, cross-shaped, square, or polygonal structure.

[0167] A method for manufacturing a printed circuit board (PCB) (1000) made of paper may further include a wiring forming process (S200a). A method for manufacturing a printed circuit board (PCB) (1000) made of paper may further include a through-hole forming process (S200b). A wiring forming process (S200a) for forming wiring may be formed between a slot structure forming process (S100) and a thin film land forming process (S200). In this regard, the wiring forming process (S200a) may be performed before or simultaneously with the slot structure forming process (S100).

[0168] In the through-hole forming process (S200b), a through-hole (1100p) may be formed to penetrate the thin-film land (1130). The through-hole forming process (S200b) may be performed before the wiring forming process (S200a) and the thin-film land forming process (S200). A via hole may be formed on the side of the through-hole (1100p) formed through the through-hole forming process (S200b) by coating it with a conductive material. Since the through-hole (1100p) and the via hole are formed through the through-hole forming process (S200b), the through-hole forming process (S200b) may be referred to as a via-hole forming process.

[0169] In the wiring formation process (S200a), a wiring (1100) may be formed by printing a conductive material on the first surface of a paper substrate (1010). The wiring (1100) may be formed to be connected to one terminal of a surface mount device (1310) placed on the paper substrate (1010). A thin film land (1130) may be formed to be connected to the other terminal of the surface mount device (1310).

[0170] A method for manufacturing a printed circuit board (PCB) (1000) made of paper may further include an insertion component mounting process (S300). A method for manufacturing a printed circuit board (PCB) made of paper may further include a surface-mount component placement process (S400). A method for manufacturing a printed circuit board (PCB) made of paper may further include a thermal curing process (S500).

[0171] After the through-hole forming process (S200b), an insert-mount component mounting process (S300) may be performed. In the insert-mount component mounting process (S300), an insert-mount component (1320) may be inserted through the first and second surfaces of the paper substrate (1010) via the thin film land (1130). In the component placement process (S500), a surface-mount component (1310) may be placed between the boundary of the thin film land (1130) and the wiring (1100). In the thermal curing process (S500), after the insert-mount component (1320) is fixed to the paper substrate (1010), the insert-mount component (1320) and the surface-mount component (1310) may be thermally cured together. Through the thermal curing process (S500), the number of thermal processes may be reduced from two to one.

[0172] 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 can be summarized as follows, but are not limited thereto.

[0173] According to the present specification, in a structure in which wires or thin-film lands are formed on a paper substrate through a groove or hole structure inside the paper substrate, wires and thin-film lands can be easily attached to the paper substrate.

[0174] According to this specification, a wiring or a thin film land can be easily printed and formed on a paper substrate at a specific temperature range through a groove or hole structure inside the paper substrate.

[0175] According to this specification, a wiring or thin film land can be implemented so that the wiring or thin film land is not peeled off from the paper substrate due to shrinkage of the paper substrate through a groove or hole structure inside the paper substrate.

[0176] According to the present specification, the heat treatment process can be simplified so that surface-mount components and insert-mount components can be fixed on a printed circuit board made of paper material with a single heat curing process.

[0177] 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.

[0178] 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 substrate having pores formed inside; A thin film land formed by printing a conductive material on the above paper substrate; and It comprises a slot structure of at least one groove or hole formed in the paper substrate corresponding to the area where the thin film land is formed, A printed circuit board characterized in that, while printing the thin film land with the conductive material, the conductive material is absorbed into the interior of the slot structure of the paper substrate and into the pores adjacent to the slot structure, thereby improving the adhesion of the thin film land.

2. In paragraph 1, A printed circuit board, wherein the above thin film land is composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, or a third conductive paste made of Ti material.

3. In paragraph 1, The above slot structure is composed of a plurality of grooves formed spaced apart in one axial direction of the paper substrate, A printed circuit board, wherein the thickness of the above paper substrate is formed thicker than the thickness of the above grooves.

4. In paragraph 1, The above slot structure is composed of a plurality of holes formed spaced apart in one axial direction of the paper substrate, A printed circuit board in which the thickness of the above paper substrate and the thickness of the above holes are formed to be the same.

5. In paragraph 1, The above slot structure is formed by a cross structure of a plurality of grooves and holes that are alternately formed and spaced apart in one axial direction of the paper substrate, The thickness of the above paper substrate is formed thicker than the thickness of the above grooves, A printed circuit board in which the thickness of the above paper substrate and the thickness of the above holes are formed to be the same.

6. In paragraph 1, The slot structure inside the above paper substrate is electrically connected to the thin film land, A printed circuit board, wherein at least one of the above-mentioned home or hole is configured as a single or multiple home or hole having a circular, straight, cross, square or polygonal structure.

7. In paragraph 1, Wiring formed by printing a conductive material on the first surface of the paper substrate and configured to be connected to a surface mount device placed on the paper substrate; and A printed circuit board further comprising a through hole formed to penetrate the thin film land.

8. In paragraph 7, Further comprising an insert mount device configured to be inserted through the first side and the second side of the paper substrate through the thin film land, The surface-mount component is placed between the boundary of the thin film land and the wiring, A printed circuit board in which, after the insertion-mounted component is fixed to the paper substrate, the insertion-mounted component and the surface-mounted component are heat-cured together, thereby reducing the number of heat processes from two to one.

9. In paragraph 8, The insertion mounting part is fixed by bonding it to the area where the through hole is formed, A printed circuit board further comprising a second conductive adhesive layer formed by applying it to a second surface of the paper substrate corresponding to the area where the insertion mounting component is bonded.

10. In paragraph 9, Further comprising a first conductive adhesive layer formed in an area adjacent to the through hole on the first surface of the paper substrate; A printed circuit board, wherein the first conductive adhesive layer is formed on the upper surface and side surfaces of the thin film land and a portion of the side surfaces of the through holes therebetween.

11. In paragraph 1, A plurality of light emit devices (LEDs) arranged spaced apart in one axial direction on the above paper substrate; A plurality of resistors arranged spaced apart in the uniaxial direction between the plurality of light-emitting elements; A power line formed in the uniaxial direction in the upper region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to the first light-emitting element and the third light-emitting element; and A ground line is formed in the uniaxial direction in the lower region of the plurality of light-emitting elements and the plurality of resistors, and is branched to be connected to the second light-emitting element and the fourth light-emitting element. A printed circuit board in which the resistance values ​​of the above resistors have different values.

12. In paragraph 11, The above power line is connected to the first light-emitting element and the third light-emitting element, which are adjacent to the second light-emitting element and the fourth light-emitting element among the plurality of light-emitting elements, A printed circuit board, wherein the ground line is connected to the second light-emitting element and the fourth light-emitting element, which are spaced apart from the first light-emitting element and the third light-emitting element among the plurality of light-emitting elements.

13. In paragraph 1, A plurality of light emitting elements arranged spaced apart in one axial direction on the above paper substrate; A plurality of resistors arranged spaced apart in the uniaxial direction between the plurality of light-emitting elements; A power line formed in the upper region of the plurality of light-emitting elements and the plurality of resistors in the uniaxial direction and branched to be connected to the first and third light-emitting elements; and A first ground line formed in the uniaxial direction in the lower region of the plurality of light-emitting elements and the plurality of resistors and branched to be connected to the second and fourth light-emitting elements; and A second ground line is connected to one end of the first ground line and is arranged parallel to the first ground line, and has an end connected to a ground terminal of the connector. A printed circuit board, wherein the other end of the first ground line is spaced apart from the connector.

14. A method for manufacturing a printed circuit board made of paper, A slot structure forming process for forming a slot structure of at least one groove or hole in a paper substrate having pores formed therein; and It includes a thin film land forming process of forming a thin film land by printing a thin film land with a conductive material on the paper substrate corresponding to the area where the above home or hole is formed. A method for manufacturing a printed circuit board, characterized in that during the thin film land forming process, the conductive material is absorbed into the interior of a slot structure and pores adjacent to the slot structure while printing the thin film land, thereby improving the adhesion of the thin film land.

15. In paragraph 14, A method for manufacturing a printed circuit board, wherein the above thin film land is composed of a first conductive paste made of Ag material, a second conductive paste made of Cu material, and a third conductive paste made of Ti material.

16. In paragraph 14, The above slot structure forming process includes a plurality of groove forming processes for forming a plurality of grooves spaced apart in one axial direction of the paper substrate, A method for manufacturing a printed circuit board, wherein in the above-mentioned plurality of groove forming processes, the thickness of the paper substrate is formed thicker than the thickness of the grooves.

17. In paragraph 15, The above slot structure forming process includes a plurality of hole forming processes for forming a plurality of holes spaced apart in one axial direction of the paper substrate, A method for manufacturing a printed circuit board, wherein the thickness of the paper substrate and the thickness of the holes are formed to be the same in the above-mentioned plurality of hole forming processes.

18. In paragraph 14, The above slot structure forming process includes a plurality of groove and hole forming processes in which grooves and holes are alternately formed spaced apart in one axial direction of the paper substrate, A method for manufacturing a printed circuit board, wherein in the above-described plurality of groove and hole forming processes, the thickness of the paper substrate is formed to be thicker than the thickness of the grooves, and the thickness of the paper substrate and the thickness of the holes are formed to be the same.

19. In paragraph 14, At least one groove or hole within the paper substrate is electrically connected to the thin film land, A method for manufacturing a printed circuit board, wherein at least one of the above-mentioned grooves or holes is configured as a single or multiple grooves in a circular, I-shaped, cross-shaped, square or polygonal structure.

20. In paragraph 14, A wiring forming process for forming a wiring between the above slot structure forming process and the above thin film land forming process; and After the above thin film land forming process, a through hole forming process is further included for forming a through hole to penetrate the thin film land. A method for manufacturing a printed circuit board, wherein the wiring is formed by printing a conductive material on a first surface of the paper substrate in the above wiring formation process, and the wiring is formed so as to be connected to a surface mount device placed on the paper substrate.

21. In paragraph 20, An insertion-mounting component mounting process in which an insertion-mounting component is inserted through the first surface and the second surface of the paper substrate through the thin film land after the above-mentioned through-hole forming process; A surface mount component placement process for placing surface mount components between the boundary of the above thin film land and the above wiring; and Further comprising a heat curing process in which the insertion-mounted component and the surface-mounted component are heat cured together after the insertion-mounted component is fixed to the paper substrate, A method for manufacturing a printed circuit board, wherein the number of thermal processes is reduced from two to one through the above thermal curing process.

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