77GHZ millimeter wave radar automobile PCB multilayer board blind slot uncovering structure

Abstract

The utility model discloses a 77GHZ millimeter wave radar automobile PCB multilayer board blind slot uncovering structure, comprising a first copper-clad plate, a second copper-clad plate and a middle PP layer, the first copper-clad plate, the middle PP layer and the second copper-clad plate are sequentially stacked from top to bottom and are pressed and solidified into a whole; a plurality of first through holes are drilled in the first copper-clad plate in a penetrating manner; a first inner copper-clad layer is arranged on the inner wall in the first through hole; the first through hole is filled with a resin filling layer; the first copper-clad plate is covered with an outer copper-clad layer on the outer side of the first through hole; a dry film layer is arranged at the bottom of the plate core L6 layer; a through blind groove is formed in the position, corresponding to the dry film layer, of the second copper-clad plate. According to the utility model, the dry film layer is arranged in the inner layer area of the first copper-clad plate, and then the blind slot is metalized, so that the blind slot plate with good quality is finally obtained, the manufacturing process is greatly shortened, the efficiency is improved, and the cost is saved.

Description

Technical Field

[0001] This utility model relates to the field of blind slot cover technology, and in particular to a blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board. Background Technology

[0002] 77GHz millimeter-wave radar automotive PCB multilayer boards are widely used in the market. Currently, the common processing method for 77GHz millimeter-wave radar automotive PCB multilayer boards involves applying a layer of yellow high-temperature tape (12-17μm thick) to the inner core cover area (bottom of the blind slot). After multilayer core lamination and other processes, the cover is mechanically removed using a depth-controlled method before gold plating. Then, the L01-L05 dielectric layers are removed, and the high-temperature tape on layer L06 is manually removed to expose the copper surface of layer L06, followed by nickel-gold plating.

[0003] After the cover is removed, the yellow high-temperature adhesive adheres to the copper surface of the PCB with the brown coating film, resulting in some adhesive residue on the copper surface and overflow into the chamfer of the blind slot. Manual cleaning with an eraser pen leaves the copper surface rough, and the incomplete or damaged cleaning results in the gold plating failing to meet the quality requirements of most customers.

[0004] There are issues such as excess adhesive residue from high-temperature tape leaving poor resistance to gold plating on copper surfaces, and the difficulty of operation, resulting in high labor costs and low product yield. Utility Model Content

[0005] In view of the above problems, this utility model is proposed to provide a blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board that overcomes or at least partially solves the above problems, especially a small and diversified one.

[0006] This utility model provides a blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board. The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure includes: a first copper-clad board, a second copper-clad board, and an intermediate PP layer. The first copper-clad board, the intermediate PP layer, and the second copper-clad board are stacked sequentially from top to bottom and pressed and cured into one piece.

[0007] The first copper-clad laminate includes a core layer L1, a third PP layer, a core layer L2, a first PP layer, a core layer L3, a dielectric layer, a core layer L4, a second PP layer, a core layer L5, a fourth PP layer, and a core layer L6, which are stacked sequentially from top to bottom.

[0008] The first copper-clad board is provided with multiple through holes drilled through it, so that the core layers L1 to L6 are connected.

[0009] The inner wall of the first through hole is provided with a first inner copper cladding layer; the first through hole is filled with a resin filling layer;

[0010] An outer copper clad layer is provided on the first copper-clad board outside the first through hole;

[0011] A dry film layer is provided at the bottom of the L6 core layer;

[0012] The second copper-clad laminate has a through-hole blind groove corresponding to the position of the dry film layer.

[0013] Optionally, the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure has multiple second through holes.

[0014] Optionally, the inner wall of the second through hole is provided with a second inner copper cladding layer.

[0015] Optionally, the second through hole is filled with a resin ink filling layer.

[0016] The technical solution provided in this embodiment of the utility model has at least the following technical effects or advantages:

[0017] The 77GHz millimeter-wave radar automotive PCB multilayer blind slot uncovering structure of this utility model sets a dry film layer in the inner layer area of ​​the first copper-clad board, and then performs blind slot metallization, finally obtaining a high-quality blind slot board. The dry film layer can be completely removed by stripping solution without leaving any residue, ensuring the quality and reliability of the blind slot, greatly shortening the manufacturing process and improving efficiency while saving costs.

[0018] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more obvious and understandable, specific embodiments of this utility model are given below. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure described in this utility model;

[0021] Figure 2This is a schematic flowchart illustrating the fabrication method of the 77GHz millimeter-wave radar automotive PCB multilayer blind slot cover structure described in this utility model.

[0022] Figure 3 This is a schematic diagram of the structure of the first copper core plate;

[0023] Figure 4 A structural schematic diagram of the inner layer circuit pattern for the first copper core board;

[0024] Figure 5 This is a schematic diagram of the structure of the first copper-clad laminate;

[0025] Figure 6 This is a schematic diagram of the structure of the first drill plate;

[0026] Figure 7 A schematic diagram of the structure for metallizing the holes in the first drill plate;

[0027] Figure 8 This is a schematic diagram of the orifice plug plate.

[0028] Figure 9 This is a schematic diagram of the structure covering the copper plate;

[0029] Figure 10 This is a schematic diagram of the copper-clad laminate structure;

[0030] Figure 11 This is a schematic diagram of the second drill plate.

[0031] Figure 12 A schematic diagram of the structure for metallizing the holes in the second drill plate;

[0032] Figure 13 This is a schematic diagram of the ink plugging structure for the second drill plate.

[0033] Explanation of reference numerals in the attached figures:

[0034] 100. First copper-clad laminate;

[0035] 1. Core layer L1; 2. Core layer L2; 3. Core layer L3; 4. Core layer L4; 5. Core layer L5; 6. Core layer L6; 7. Resin ink filling layer; 8. Second inner copper cladding layer; 9. Second through-hole; 10. Blind slot; 11. Intermediate PP layer; 13. First PP layer; 14. Dielectric layer; 15. Second PP layer; 16. Third PP layer; 17. Fourth PP layer; 18. First through-hole; 19. First inner copper cladding layer; 20. Resin filling layer; 21. Outer copper cladding layer; 22. Dry film layer;

[0036] 200. Second copper-clad laminate. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings.

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The accompanying drawings show preferred embodiments of the present invention. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0039] Unless otherwise specified, all raw materials, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0040] Figure 1 This is a schematic diagram of the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure described in this utility model, combined with... Figure 1 As shown, the blind slot cover structure of the 77GHz millimeter-wave radar automotive PCB multilayer board includes a first copper-clad laminate 100, a second copper-clad laminate 200 and an intermediate PP layer 11. The first copper-clad laminate 100, the intermediate PP layer 11 and the second copper-clad laminate 200 are stacked from top to bottom and pressed and cured into one piece.

[0041] The first copper-clad laminate 100 includes, from top to bottom, a core layer L1 1, a third PP layer 16, a core layer L2 2, a first PP layer 13, a core layer L3 3, a dielectric layer 14, a core layer L4 4, a second PP layer 15, a core layer L5 5, a fourth PP layer 17, and a core layer L6 6, which are stacked together. The layers of the first copper-clad laminate 100 are obtained by laminating and curing them into one piece, and then subsequent processes such as drilling are performed to obtain the corresponding structure.

[0042] The first copper-clad laminate 100 is provided with multiple through holes 18 drilled through to allow the core L1 layer 1 to core L6 layer 6 to be connected.

[0043] The inner wall of the first through hole 18 is provided with a first inner copper cladding layer 19; the first through hole 18 is filled with a resin filling layer 20;

[0044] An outer copper clad laminate 21 is provided on the first copper clad laminate 100 outside the first through hole 18;

[0045] A dry film layer 22 is provided at the bottom of the core L6 layer 6. The dry film layer 22 is DuPont dry film model W-520. After the light source reacts and is treated with developing solution, a portion of the required dry film is retained on the copper surface of the L06 layer. After exposure, the unexposed areas can be quickly and cleanly dissolved and removed in the developing solution, forming a clear pattern (retaining the uncovered pattern, i.e., the area corresponding to the subsequent blind trench 10).

[0046] The second copper-clad laminate 200 has a through blind groove 10 at the position corresponding to the dry film layer 22.

[0047] In this embodiment of the utility model, the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure is provided with a plurality of second through holes 9; the inner wall of the second through hole 9 is provided with a second inner copper cladding layer 8; and the second through hole 9 is filled with a resin ink filling layer 7.

[0048] It should be noted that, in this embodiment of the present invention, the second copper-clad laminate 200 has the same layer structure as the first copper-clad laminate 100 before drilling.

[0049] In this embodiment of the invention, the dry film layer 22 can be removed by stripping, and a nickel-gold layer can be deposited to achieve metallization of the blind trench 10.

[0050] The blind slot uncovering structure of the 77GHz millimeter-wave radar automotive PCB multilayer board of this utility model sets a dry film layer 22 in the inner layer area of ​​the first copper-clad board 100, and then performs metallization of the blind slot 10. The dry film layer 22 can be completely removed by stripping solution without leaving any residue, and finally a high-quality blind slot board is obtained, ensuring the quality and reliability of the blind slot 10, greatly shortening the manufacturing process and improving efficiency while saving costs.

[0051] The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure of this utility model can be obtained by the preparation method of the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure of the above embodiment. It has the corresponding functional steps and beneficial effects. For the corresponding preparation process, please refer to the following embodiment of the preparation method of the 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure.

[0052] This utility model provides a method for fabricating a blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board. The method for fabricating the blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board includes the following steps:

[0053] S1. A first copper core board is obtained by cutting copper-clad substrate from copper-clad substrate using a cutting machine, and copper foil is cut to obtain core L1 layer 1 and core L6 layer 6. The first copper core board includes core L2 layer 2, first PP layer 13, core L3 layer 3, dielectric layer 14, core L4 layer 4, second PP layer 15 and core L5 layer 5 stacked in sequence.

[0054] Figure 3 The diagram below shows the structure of the first copper core board. In this embodiment of the invention, the copper-clad substrate is cut into the designed size by a cutting machine to obtain the first copper core board, and copper foil is cut to obtain the core layer L1 and the core layer L6.

[0055] In this embodiment of the invention, the material of the dielectric layer 14 is polyimide, Teflon, polysulfide, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, or polyimide-polyethylene-terephthalate copolymer or a combination thereof.

[0056] In this embodiment of the utility model, the thickness of the core layer L1, core layer L2, core layer L3, core layer L4, core layer L5, and core layer L6 is 0.5 oz.

[0057] S2. The first copper core board, the first core board and the sixth core board are baked respectively.

[0058] In this embodiment of the present invention, in step S2, the baking temperature is 170°C and the baking time is 2 hours. The baking process can dry the water vapor molecules absorbed by the core layers L1, L2, L3, L4, L5, and L6 due to storage, thus preventing deformation of the board material during subsequent processing.

[0059] S3. On the first copper core board, an inner layer circuit pattern is created by etching.

[0060] Figure 4 A schematic diagram of the structure for fabricating the inner layer circuit pattern of the first copper core board is shown in Figure 4. According to actual needs, the required temperature and pressure are selected. A dry film is applied to the surface of the first copper core board, and then a film is used for alignment. Finally, ultraviolet light is used in the exposure machine to cause the dry film not covered by the film to react and form the required circuit pattern on the board surface. Then, in the developing section, the film not exposed to light is dissolved under the action of the developing solution. In the etching section, the exposed copper is etched away under the action of the acid etching solution. Finally, in the stripping section, the film is removed under the action of the stripping solution, exposing the inner layer circuit pattern.

[0061] S4. Perform optical inspection on the first copper core board after etching to identify the defective parts on the first copper core board and repair them.

[0062] This utility model embodiment uses an Eagle Eye AOI machine to scan and identify open or short circuit defects, mark and process them, and then repair them.

[0063] S5. The core L1 layer 1, the first copper core plate and the core L6 layer 6 are stacked and laminated, and a third PP layer 16 is filled between the first core and the first copper core plate, and a fourth PP layer 17 is filled between the first copper core plate and the sixth core. The core L1 layer 1, the third PP layer 16, the first copper core plate, the fourth PP layer 17 and the core L6 layer 6 are cured by heating to obtain the first copper clad laminate 100.

[0064] Figure 5 The diagram below shows the structure of the first copper-clad laminate 100. In this embodiment of the invention, heating causes the semi-cured resin of each PP layer to flow and fill the circuit, substrate and depth control blind groove 10. When the temperature reaches a certain level, curing occurs, bonding the layers together.

[0065] S6. A plurality of through holes 18 are drilled on the first copper-clad board 100 to make the core L1 layer 1 to the core L6 layer 6 connected to each other, thus obtaining the first drilled board.

[0066] Figure 6 The diagram below shows the structure of the first drilled board. Referring to Figure 6, this utility model uses mechanical drilling to drill a first through hole 18 of 0.3mm / 0.25mm, so that the core layers L01-L6 are drilled through. The thickness of the copper plating in the holes is 20-23μm, so that the inner layers L1-L6 are connected to the other layers.

[0067] S7. The first drilled board is subjected to hole metallization treatment to make the core L1 layer 1 to core L6 layer 6 conductive. After copper plating is performed on the first through hole 18 of the first copper-clad board 100, the copper-clad board 100 after copper plating is subjected to VCP hole electroplating to thicken copper, so that the inner wall of the first through hole 18 is formed with the first inner copper clad layer 19.

[0068] Figure 7 The structural diagram for the hole metallization of the first drill plate is shown in Figure 7. In this embodiment of the present invention, in step S7, the thickness of the copper plating is 0.02 μm, and the thickness of the thickened copper is 25-35 μm.

[0069] This utility model embodiment performs hole metallization treatment on the board after drilling. The main purpose of the treatment is to form a conductive layer in the substrate area in the middle of the board. After copper plating, the board is mechanically drilled to thicken the copper inside by electroplating, so that the L1 layer and the L6 layer are connected.

[0070] S8. The first through hole 18 is filled with resin by using resin plugging, so that the first through hole 18 is filled with resin filling layer 20, and a plugged plate is obtained.

[0071] Figure 8 The diagram below shows the structure of the plug plate. In this embodiment of the invention, the resin filling layer 20 ensures the insulation effect.

[0072] S9. A copper coating layer 21 is plated on the outside of the resin ink in the metallized mechanical holes of the plugging plate to obtain a copper coating plate.

[0073] Figure 9 For a structural schematic diagram of the copper plate, refer to Figure 9. In this embodiment of the present invention, the thickness of the outer copper layer 21 is greater than 12 μm.

[0074] S10. Repeat steps S1-S5 to obtain a second copper-clad laminate 200 with the same layer structure as the first copper-clad laminate 100.

[0075] This utility model is implemented by repeating steps S1-S5 to obtain a second copper-clad laminate 200, and then etching the required circuit pattern on the second copper-clad laminate 200.

[0076] S11. After applying a dry film layer 22 to the outside of the core L6 layer 6 of the copper plate, perform exposure and development treatment to form a clear target pattern, and then perform browning treatment.

[0077] The dry film layer 22 is DuPont dry film model W-520. After the light source reacts and is treated with developing solution, a portion of the required dry film is retained on the copper surface of layer L06. After exposure, the unexposed areas can be quickly and cleanly dissolved and removed in the developing solution, forming a clear pattern (retaining the uncovered pattern, i.e., the area corresponding to the subsequent blind trench 10).

[0078] S12. The copper clad laminate after browning treatment is laminated with the second copper clad laminate 200. An intermediate PP layer 11 is filled between the core L6 layer 6 and the second copper clad laminate 200. The copper clad laminate, the intermediate PP layer 11 and the second copper clad laminate 200 are cured by heating to obtain a copper clad cured board.

[0079] Figure 10The diagram above shows the structure of the copper-clad laminate. As shown in Figure 10, in this embodiment of the invention, heating causes the semi-cured resin of each PP layer to flow and fill the circuit, substrate and depth control blind groove 10. When the temperature reaches a certain level, curing occurs, bonding the layers together.

[0080] S13. A plurality of through holes 9 are drilled on the copper-clad curing board to make the layers of the copper-clad board and the second copper-clad board 200 interconnected, thus obtaining a second drilled board.

[0081] Figure 11 The diagram below shows the structure of the second drilled plate. In this embodiment of the invention, a second through hole 9 of 0.3mm / 0.25mm is drilled using mechanical drilling to allow the copper clad plate and the layers of the second copper clad plate 200 to be interconnected.

[0082] S14. The second drilled board is subjected to hole metallization treatment. After copper plating is performed on the second through hole 9 of the second drilled board, the copper-plated second drilled board is then subjected to VCP hole plating to thicken copper, so that a second inner copper cladding layer 8 is formed on the inner wall of the second through hole 9.

[0083] Figure 12 A schematic diagram of the structure for the hole metallization treatment of the second drilled plate is shown in Figure 12. The thickness of the second inner copper cladding layer 8 produced in this embodiment of the present invention is 23-25 ​​μm.

[0084] S15. After etching the second drill plate again, the required pattern is etched on the second drill plate.

[0085] S16. The first through hole 18 of the second drilled plate after etching is filled with ink plugging, so that the second through hole 9 is filled with resin ink filling layer 7, and a plugged plate is obtained.

[0086] Figure 13 The diagram below shows the structure of the second drilled plate with ink plugging. Specifically, in this embodiment, ink is plugged into the second through hole 9, and a layer of ink with a thickness of 18-40 μm is applied to the copper surface. Then, it is exposed by an LDI machine and reacted with Na₂CO₃ developing solution. The part that needs to be covered with ink is retained, and the part that does not need to be covered with ink is developed to expose the copper pads, etc.

[0087] S17. By mechanically controlling the depth, a blind groove 10 is milled into the area corresponding to the dry film layer 22 on the second copper clad laminate 200, so that the dry film layer 22 is located at the bottom of the blind groove 10.

[0088] Combination Figure 1As shown, in this embodiment of the present invention, blind grooves 10 are milled on the second copper-clad laminate 200 in the area corresponding to the dry film layer 22 by mechanical depth control or laser cutting. The depth control accuracy is controlled within ±0.01mm. The depth of the milled groove is determined according to the actual core medium thickness requirements. If it is used to install certain special components or to achieve specific structural functions, the depth control milling capability is between 0.5mm and 1.5mm. Under the premise of ensuring that the core L6 layer 6 is not damaged, the dry film layer 22 is exposed at the bottom of the blind groove 10.

[0089] S18. The dry film layer 22 is removed from the bottom of the blind groove 10 by reacting with the stripping solution, so that the welding plating area of ​​the core L6 layer 6 corresponding to the dry film layer 22 is exposed.

[0090] In this embodiment of the invention, the stripping solution is a sodium hydroxide reagent with a concentration of 1.8%-3.0%, or a reagent with a concentration of 3-5 wt% sodium hydroxide and the balance being deionized water. The stripping solution is used at a temperature of 45-55°C, and the stripping time is 60-90 seconds. In a continuous stripping device, the conveying speed is 2.0-4.0 m / min, and the spray pressure is controlled at 2.0-2.5 bar. The stripping solution reacts with the polymer compounds in the dry film layer 22 through a saponification reaction to generate water-soluble substances, thereby achieving the purpose of stripping the dry film layer 22 on the L06 layer.

[0091] S19. A nickel-gold layer is deposited on the welding plating area.

[0092] In this embodiment of the invention, the dry film layer 22 can be removed by stripping, and a nickel-gold layer can be deposited to achieve metallization of the blind trench 10.

[0093] The method for preparing the blind slot cover structure of the 77GHz millimeter-wave radar automotive PCB multilayer board described in this embodiment involves setting a dry film layer 22 in the inner layer region of the first copper-clad laminate 100, and then removing the dry film layer 22 after subsequent exposure development, lamination, etching, solder resist, curing, and pre-surface treatment (dielectric layer). The dry film layer 22 can be completely removed without residue by the stripping solution, and under ultraviolet irradiation, it can quickly undergo a polymerization reaction to form a stable resist pattern, enabling precise pattern transfer of the circuit board. This ultimately yields a high-quality blind slot board, effectively optimizing the processing technology of the inner layer blind slot 10, ensuring the quality and reliability of the blind slot 10, greatly shortening the manufacturing process and improving efficiency while saving costs.

[0094] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0095] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, the inventive aspect lies in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0096] It should be noted that the above embodiments are illustrative of the present invention and not restrictive of the present invention, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims.

Claims

1. A blind slot cover structure for a 77GHz millimeter-wave radar automotive PCB multilayer board, characterized in that, The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure includes: a first copper-clad board, a second copper-clad board, and an intermediate PP layer. The first copper-clad board, the intermediate PP layer, and the second copper-clad board are stacked sequentially from top to bottom and pressed and cured into one piece. The first copper-clad laminate includes a core layer L1, a third PP layer, a core layer L2, a first PP layer, a core layer L3, a dielectric layer, a core layer L4, a second PP layer, a core layer L5, a fourth PP layer, and a core layer L6, which are stacked sequentially from top to bottom. The first copper-clad board is provided with multiple through holes drilled through it, so that the core layers L1 to L6 are connected. The inner wall of the first through hole is provided with a first inner copper cladding layer; the first through hole is filled with a resin filling layer; An outer copper clad layer is provided on the first copper-clad board outside the first through hole; A dry film layer is provided at the bottom of the L6 core layer; The second copper-clad laminate has a through-hole blind groove corresponding to the position of the dry film layer.

2. The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure according to claim 1, characterized in that: The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure has multiple second through holes.

3. The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure according to claim 2, characterized in that: The inner wall of the second through hole is provided with a second inner copper cladding layer.

4. The 77GHz millimeter-wave radar automotive PCB multilayer board blind slot cover structure according to claim 2, characterized in that: The second through hole is filled with a resin ink filling layer.

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