Method for producing a printed circuit board protective layer

Abstract

A method for producing a printed circuit board protective layer, comprising the following steps: S10: coating a surface of a printed circuit board (1) with a protective ink and curing to form an ink layer (2), wherein the ink layer (2) has a preset opening (201) and the thickness of the ink layer (2) is greater than or equal to 10 µm; and S20: removing the excess protective printing inks at the inner edge of the preset opening (201) using a laser engraving machine to form a protective layer (3) with a finely carved opening (301); characterized in that step S10 comprises: Printing and curing the protective ink on the circuit board (1) using an inkjet printer to form a first printing layer (21); Printing and curing the protective ink on the first printing layer (21) using the inkjet printer to form a second printing layer (22); and Repeating the above steps until the ink layer (2) is formed; wherein the first printing layer (21), the second printing layer (22) to the N-th printing layer each have a thickness in the range of 3µm - 5pm; wherein the inkjet printer comprises an inkjet head and a radiant light source arranged on one side of the inkjet head and used to cure the protective ink, wherein the radiant light source is a UV light source.

Description

Technical area

[0001] The present application relates to the technical field of printed circuit board production, in particular to a method for producing a printed circuit board protective layer. State of the art

[0002] A printed circuit board (PCB) is a supporting structure for electronic components. A PCB typically comprises one or more layers of circuitry. After the circuit layer(s) and an insulating layer are fabricated on the PCB, the surface of the PCB is coated with a protective layer, commonly known as "green oil." The current process for producing the protective layer is as follows: screen-printing green oil on the surface of the PCB or adhering a partially cured green oil to completely cover the PCB. The green oil is then firmly bonded to the PCB surface through a curing process. The excess green oil is then removed using a wet chemical exposure and development process to form an opening. This process has a complicated production process and may pollute waterways.In addition, the process requires customized auxiliary materials and equipment, which is relatively expensive for small-scale production.

[0003] Document US 2005 / 0 158 668 A1 relates to a method for forming a two-dimensional mask pattern on a substrate, wherein a method is described comprising the steps defined in the preamble of claim 1. Furthermore, document US 2005 / 0 176 177 A1 shows a method and apparatus for applying ink according to a solder mask pattern to a printed circuit board having raised pads defining pad edges, the method comprising flooding the printed circuit board with ink such that the ink reaches the pad edges and is stopped there without reaching the raised pads.Furthermore, document US 2003 / 0 075 532 A1 discloses a method for forming conductive traces on a substrate using a laser ablation technique, wherein a substrate is first coated with a conductive ink, and a laser spot is then focused on the ink to ablate a portion of the ink layer from the substrate and define ink tracks, which are then cured. Furthermore, a method for forming multiple layers of conductive traces on a substrate is described, wherein the individual layers of conductive traces are separated by a layer of cured dielectric ink, and wherein the method comprises the following steps: sequentially applying, ablating, and curing alternating dielectric and conductive ink layers onto a substrate containing cured ink tracks. Task

[0004] The present application aims to provide a method for producing a printed circuit board protective layer to solve the technical problems in producing the protective layer in a wet chemical exposure and development method in the prior art, such as a complicated production process, environmental pollution and high cost. Technical solution

[0005] The present application provides a method for producing a printed circuit board protective layer according to claim 1, comprising the following steps: S10: Coating a surface of a printed circuit board with a protective ink and curing to form an ink layer, wherein the ink layer has a preset opening and the thickness of the ink layer is greater than or equal to 10 µm; and S20: Removing the excess protective inks on the inner edge of the preset opening using a laser engraving machine to form a protective layer with a finely carved opening.

[0006] Step S10 includes the following steps: Printing and curing the protective ink on the circuit board using an inkjet printer to form a first printing layer; Printing and curing the protective ink on the first printing layer using the inkjet printer to form a second printing layer; and Repeat the above steps until the ink layer is formed; wherein the first printing layer, the second printing layer to the N-th printing layer each have a thickness in the range of 3 µm-5 µm.

[0007] It is further provided that the inkjet printer comprises an inkjet head and a radiation light source arranged on one side of the inkjet head and used to cure the protective printing ink.

[0008] In one embodiment, step S10 again comprises: Printing the protective ink on the circuit board using a screen printing stencil; and Curing the protective ink using a curing lamp to form the ink layer.

[0009] In one embodiment, the curing radiator comprises one or both of a light radiator and a heat radiator.

[0010] In one embodiment, the light emitter is a UV curing oven and the heat emitter is a mesh belt oven or an oven.

[0011] In one embodiment, the resolution of the preset aperture is higher than 100 µm and the resolution of the finely carved aperture is lower than 100 µm.

[0012] In one embodiment, step S20 again comprises: Transmitting the size information of the circuit board and the finely carved opening to a control module of the laser engraving machine; Identifying the pattern coated on the protective layer of the circuit board by an identification module of the laser engraving machine, transmitting it to the control module, and comparing it with the size information to calculate a laser engraving path; and Moving a laser head of the laser engraving machine to the edge of the preset opening and removing the unnecessary protective ink according to the laser engraving path to form the protective layer.

[0013] In one embodiment, the laser engraving machine comprises a control module, an identification module, and a laser head, wherein the identification module is electrically connected to the control module, wherein the identification module is used to transmit the received information to the control module, and wherein the control module is used to control the movements of the laser head.

[0014] In one embodiment, it is provided that the resolution of the laser engraving machine in the transverse direction is less than or equal to 5 µm, and the resolution of the laser engraving machine in the longitudinal direction is less than or equal to 5 µm.

[0015] In one embodiment, the method after step S20 further comprises cleaning the protective printing ink remaining on the circuit board.

[0016] In one embodiment, the protective printing ink consists of a thixotropic agent and an epoxy resin.

[0017] In one embodiment, the thixotropic agent is one or more of hydrogenated castor oil derivatives, polyamide waxes, polyureas, fumed silicas, bentonites, and polyethylene glycol.

[0018] The method for manufacturing a printed circuit board protective layer according to the present application has the following advantages: Compared with the prior art, the method for manufacturing a printed circuit board protective layer according to the present application first applies and cures an ink layer with a preset opening on the surface of the printed circuit board, and then uses a laser engraving machine to remove the excess protective ink at the inner edge of the preset opening to ensure the accuracy of the opening. This method eliminates the need for production processes such as exposure and development to form the protective layer. The process is simple and pollution-free. It achieves high material utilization rate and high opening resolution, and is suitable for production of various volumes such as prototypes, small series, and large batches. Short description of the characters

[0019] To more clearly explain the technical solution in the detailed embodiments of the present application, the figures used in the explanation of the embodiments or the prior art are briefly introduced below. Obviously, the figures described below show only some embodiments of the present application. Those of ordinary skill in the art can derive other figures based on the figures without requiring creative work. Fig. 1 shows a flowchart of a method for manufacturing a printed circuit board protective layer in an embodiment of the present application. Fig. 2 shows a schematic structural view of a printed circuit board in an embodiment of the present application. Fig. 3 shows a structural view for applying an ink layer in the present application. Fig. 4 shows a structural view for applying an ink layer in another embodiment of the present application. Fig. 5 shows a structural view of a circuit board coated with a protective layer in an embodiment of the present application. Embodiments of the invention

[0020] In order to more clearly clarify the technical problems to be solved by the present application, the technical solutions, and the advantageous effects of the present application, the present application will be described in more detail below in conjunction with the drawings and exemplary embodiments. It should be understood that the detailed embodiments described herein serve only to explain the present application and do not limit the present application.

[0021] It should be noted that when an element is described as being "attached" or "located" to another element, the element may be directly on the other element or indirectly on the other element. When an element is described as being "connected" to another element, the element may be directly connected to the other element or indirectly connected to the other element.

[0022] It should be noted that the directional or positional relationships using technical terms such as "length," "width," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," etc., are based on the directional or positional relationships illustrated in the figures. They serve only to explain the present application and facilitate explanation. They do not show or imply that the illustrated devices or elements have particular directions or are intended to be constructed and operated in particular directions. Therefore, they cannot be understood as limiting the present application.

[0023] Furthermore, "the first," "the second," etc., are used only to clarify the objective and cannot be understood to indicate or imply the relative importance or the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly mean that the number of that feature is one or more. In the description of the present application, the word "more" means two or more unless expressly defined otherwise.

[0024] As in Fig. 1 to 5, a method for producing a printed circuit board protective layer according to the present application is explained in more detail below. The method for producing a printed circuit board protective layer comprises the following steps: S10: Coating a surface of a printed circuit board 1 with a protective ink and curing to form an ink layer 2, wherein the ink layer 2 has a preset opening 201 and the thickness of the ink layer 2 is greater than or equal to 10 µm; and S20: Removing the excess protective inks at the inner edge of the preset opening 201 using a laser engraving machine to form a protective layer 3 with a finely carved opening 301.

[0025] The circuit layer 11 and the insulating layer of the printed circuit board 1 are already finished, and the protective layer 3 has a protective function for the surface of the printed circuit board 1. With the finely carved opening 301 on the protective layer 3, the circuits can be exposed on the surface of the printed circuit board 1 to facilitate subsequent welding, tinning, and the like.

[0026] Compared with the prior art, the method for manufacturing a printed circuit board protective layer according to the present application first applies and cures an ink layer 2 with a preset opening 201 on the surface of the printed circuit board 1. Then, the excess protective ink at the inner edge of the preset opening 201 is removed by a laser engraving machine to ensure the accuracy of the opening. This method eliminates the need for production processes such as exposure and development to form the protective layer 3. The method is simple and pollution-free. It features a high material utilization rate and high opening resolution, and is suitable for production of various volumes such as prototypes, small series, and large batches.

[0027] Furthermore, in one embodiment, the resolution of the preset opening 201 is higher than 100 µm, and the resolution of the finely carved opening 301 is lower than 100 µm. For the ink layer 2 directly applied to the printed circuit board 1, its preset opening 201 has a lower resolution due to limitations of printing and screen printing technology. In the present embodiment, the preset opening 201 is finely carved using a laser engraving machine to remove the excess protective ink, thereby forming a finely carved opening 301 with a resolution of less than 100 µm to meet the requirement of the printed circuit board 1 for the accuracy of the protective layer 3.

[0028] Furthermore, one embodiment provides that the protective printing ink consists of a thixotropic agent, an epoxy resin, and other materials. A thixotropic network can be formed between the thixotropic agent molecules, so that the printing ink contains pseudoplastic or thixotropic substances. The thixotropic agent can be one or a combination of hydrogenated castor oil derivatives, polyamide waxes, polyureas, fumed silicas and modified substances thereof, bentonites, and polyethylene glycol. After the epoxy resin has cured, its long-term heat resistance temperature is above 180°C, whereby the printing ink layer 2 has better heat resistance.

[0029] The protective ink has the properties of light-curing or thermal curing and can be rapidly cured under irradiation of a certain light energy or heat energy; above this, the thickness of the protective layer is greater than or equal to 10 µm. The protective ink has the following properties after full curing: a breakdown voltage of greater than 1000 V, a surface hardness of greater than 2H, and an adhesion force to the substrate of greater than 10 N. The organic monomers with a small molecular weight in the protective ink can be bonded together in the low-temperature light-curing process, and no waste emissions are generated in the subsequent process.

[0030] According to Fig. 3, S10 according to the present application comprises the following steps: Printing and curing the protective ink on the circuit board 1 using an inkjet printer to form a first printing layer 21; Printing and curing the protective ink on the first printing layer 21 using the inkjet printer to form a second printing layer 22; and Repeating the above steps until the ink layer 2 is formed; wherein the first printing layer 21, the second printing layer 22 to the N-th printing layer each have a thickness in the range of 3 µm - 5 µm.

[0031] Furthermore, the inkjet printer is provided with an inkjet head and a radiation light source. Compared to the circuit board 1, the inkjet head is smaller in size and cannot print the required ink layer 2 through unidirectional movement. Specifically, the printing path of the inkjet head may be as follows: after the inkjet head finishes printing along the forward horizontal direction, the inkjet head moves toward the vertical direction by a certain distance, then the inkjet head moves along the reverse horizontal direction and irradiates the ink until the single-layer printing is completed. In the inkjet printing process of the inkjet head, the radiation light source performs light irradiation for the printed protective ink, so that the ink is cured or partially cured.After each layer of protective inks is printed, the protective ink layer is fully cured or partially cured under the action of the radiant light source. The relative positions of the inkjet head and the radiant light source are not limited here. Specifically, the protective ink is partially cured under the condition of light irradiation, and at a temperature below 250°C, the partially cured protective ink remains in a non-flowing state throughout. It should be noted that the radiant light source emits light as an initiating light source to cure the ink of each layer. In general, the light from a radiant light source can be UV light or light emitted by daylight lamps such as LEDs. According to the present invention, the radiant light source is a UV light source.Of course, after the ink layer 2 is completely formed, the ink layer 2 can also be fully cured by light curing or thermal curing, so that it has higher structural strength and insulating electrical performance.

[0032] It should be noted that the ink layer 2 consists of the first printing layer 21, the second printing layer 22, and the Nth printing layer 2, where N is an integer greater than or equal to 3. Of course, the ink layer 2 may also be formed by superimposing only the first printing layer 21 and the second printing layer 22. In this case, the thickness of the first printing layer 21 and the second printing layer 22 is each 5 µm, and the thickness of the ink layer 2 is 10 µm.

[0033] Referring to Fig. 4 includes S10 in another embodiment of a circuit board protection layer according to the present application: Printing the protective ink on the circuit board 1 using a screen printing stencil; and Curing the protective ink using a curing lamp to form the ink layer 2.

[0034] In this embodiment, the protective ink is printed on the surface of the printed circuit board 1 through the screen printing stencil in one step, then the protective ink is cured using a curing lamp to form the ink layer 2. Specifically, when printing the screen printing stencil, the print head prints unidirectionally in the horizontal direction or unidirectionally in the vertical direction, and the ink layer 2 can be formed by one print. When curing the protective ink using the curing lamp, the specific steps may be as follows: placing the printed circuit board 1 in a UV curing oven or other light irradiation device, irradiating the protective ink so that it is partially cured and forms a non-flowing state, then placing the printed circuit board 1 in a mesh belt oven, a baking oven, or other heat irradiation device so that the protective ink is fully cured.

[0035] Referring to Fig. 5, in step S20, the excess protective inks at the inner edge of the preset opening 201 are removed using a laser engraving machine to form a finely carved opening 301.

[0036] The resolution of the laser engraving machine in the transverse direction is less than or equal to 5 μm, and the resolution of the laser engraving machine in the longitudinal direction is less than or equal to 5 μm to ensure the accuracy of the laser engraving, so that the accuracy of the finely carved opening 301 meets the design requirements.

[0037] Step S20 in turn includes: Transmitting the size information of the circuit board 1 and the finely carved opening 301 to a control module of the laser engraving machine; Identifying the pattern coated on the ink layer 2 of the circuit board 1 by an identification module of the laser engraving machine, transmitting it to the control module, and comparing it with the size information to calculate a laser engraving path; and Moving a laser head of the laser engraving machine on the edge of the preset opening 201 and removing the unnecessary protective ink according to the laser engraving path to form the protective layer 3.

[0038] In one embodiment, the laser engraving machine comprises a control module, an identification module, and a laser head, wherein the identification module is electrically connected to the control module. After the information obtained by the identification module has been transmitted to the control module, the control module can calculate the movement path of the laser head in accordance with the information and control the movement of the laser head.When the printed circuit board 1 is under the laser engraving machine, the identification module of the laser engraving machine captures the images of the printed circuit board 1 and the ink layer 2 and transmits the captured images to the control module. After analysis, the control module compares the size information of the printed circuit board 1 in the image information with the pre-stored size information of the printed circuit board 1, and sets the position of the finely carved opening 301 through the pre-stored size information of the finely carved opening 301 to calculate the engraving path of the laser head. Then, the laser head is moved to a position above the preset opening 201, and in accordance with the calculated path movement, the excess protective inks are removed to form the protective layer 3.

[0039] After step S20, the method for producing a printed circuit board protective layer may further include cleaning the protective ink remaining on the printed circuit board to remove the waste ink remaining after laser burning, thereby further improving the surface quality of the printed circuit board. Of course, the method after step S20 may further include tinning, welding, and other steps, but this is not limited here.

[0040] The above content is a detailed explanation of the present application in conjunction with preferred embodiments; the present application is not limited thereto. All modifications, equivalent replacements, and improvements made within the spirit and principles of the present application are to be considered within the scope of the present application. List of reference symbols 1 circuit board 11 Circuit layer 2 ink layers 201 preset opening 21 first printing layer 22 second printing layer 3 protective layer 301 finely carved opening

Claims

[1] A method for producing a printed circuit board protective layer, comprising the following steps: S10: coating a surface of a printed circuit board (1) with a protective ink and curing to form an ink layer (2), wherein the ink layer (2) has a preset opening (201) and the thickness of the ink layer (2) is greater than or equal to 10 µm; and S20: removing the excess protective printing inks at the inner edge of the preset opening (201) using a laser engraving machine to form a protective layer (3) with a finely carved opening (301); characterized by , that step S10 includes: Printing and curing the protective ink on the circuit board (1) using an inkjet printer to form a first printing layer (21); Printing and curing the protective ink on the first printing layer (21) using the inkjet printer to form a second printing layer (22); and Repeating the above steps until the ink layer (2) is formed; wherein the first printing layer (21), the second printing layer (22) to the N-th printing layer each have a thickness in the range of 3µm - 5pm; wherein the inkjet printer comprises an inkjet head and a radiant light source arranged on one side of the inkjet head and used to cure the protective ink, wherein the radiant light source is a UV light source. [2] A method for producing a printed circuit board protective layer according to claim 1, characterized by that the resolution of the preset aperture (201) is higher than 100 µm, and the resolution of the finely carved aperture (301) is lower than 100 µm. [3] A method for producing a printed circuit board protective layer according to claim 1, characterized by that step S20 further comprises: Transmitting the size information of the circuit board (1) and the finely carved opening (301) to a control module of the laser engraving machine; Identifying the pattern coated on the protective layer (3) of the circuit board (1) by an identification module of the laser engraving machine, transmitting it to the control module, and comparing it with the size information to calculate a laser engraving path; and Moving a laser head of the laser engraving machine on the edge of the preset opening (201) and removing the unnecessary protective ink according to the laser engraving path to form the protective layer (3). [4] A method for producing a printed circuit board protective layer according to claim 1, characterized bythat the laser engraving machine comprises a control module, an identification module and a laser head, wherein the identification module is electrically connected to the control module, wherein the identification module is used to transmit the received information to the control module, and wherein the control module is used to control the movements of the laser head. [5] A method for producing a printed circuit board protective layer according to claim 1, characterized by that the resolution of the laser engraving machine in the transverse direction is less than or equal to 5 µm, and the resolution of the laser engraving machine in the longitudinal direction is less than or equal to 5 µm. [6] A method for producing a printed circuit board protective layer according to claim 1, characterized by that the method after step S20 further comprises cleaning the protective printing ink remaining on the circuit board (1). [7] A method for producing a printed circuit board protective layer according to claim 1, characterized by that the protective printing ink consists of a thixotropic agent and an epoxy resin. [8] A method for producing a printed circuit board protective layer according to claim 7, characterized by that the thixotropic agent is one or more of hydrogenated castor oil derivatives, polyamide waxes, polyureas, fumed silicas, bentonites, and polyethylene glycol.

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