A laser blind hole flash processing method for flexible circuit board

Abstract

The present invention relates to a method for processing a flexible circuit board, and in particular to a method for laser blind hole burr treatment of a flexible circuit board, which comprises: providing a flexible circuit board, copper plating the flexible circuit board, and laser drilling the flexible circuit board; providing a first nylon brush and a second nylon brush, and mechanically grinding the blind holes formed on the flexible circuit board twice, with the preset abrasive meshes of the two grindings being different. Wherein, if the flexible circuit board is opened for copper removal after copper plating, so that part of the flexible circuit board is exposed, then after the second mechanical grinding of the flexible circuit board, the flexible circuit board is placed in a cylinder, and a solution is poured into the cylinder and ultrasonic vibration is performed to remove the burrs of the blind holes; if the flexible circuit board is not opened for copper removal after copper plating, the flexible circuit board is placed in a cylinder, and clean water is poured into the cylinder and the flexible circuit board is washed with water. With the structure of the present invention, the burrs of the blind holes can be cleaned by multiple mechanical grindings in combination with preset ultrasonic treatment without damaging the flexible circuit board.

Description

Technical Field

[0001] The invention relates to a flexible circuit board processing method, in particular to a method for processing laser blind hole flashing of a flexible circuit board. Background Art

[0002] The description in this section merely provides background information related to the present disclosure and may not constitute prior art.

[0003] In the process of processing flexible circuit boards, laser drilling is generally required. Due to the physical properties of the substrate, burrs are usually left at the blind holes, which affects the yield rate of flexible circuit board processing. Therefore, the burrs need to be removed. The existing method is to remove the burrs of the flexible circuit board by mechanical grinding, but the mechanical grinding strength is not enough, and it is often difficult to achieve satisfactory results. Therefore, some existing technologies use auxiliary plasma cleaning to treat the flexible circuit board, but plasma cleaning is costly and time-consuming, and the treatment depth is insufficient for the blind hole treatment of some complex structures. Or some directly use the ultrasonic treatment method used in hard circuit boards in the treatment of flexible circuit boards. Since some flexible circuit boards may not have windows for copper removal, the ultrasonic treatment will crack the copper plating. After the cracking, some areas of the copper layer are prone to collecting clean water or chemicals, resulting in contamination of the board surface of the flexible circuit board, affecting the yield rate of the product.

[0004] Currently, there is no method for processing laser blind vias on flexible circuit boards that can solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for processing laser blind hole burrs of flexible circuit boards, which can clean the burrs of blind holes by multiple mechanical grindings combined with preset ultrasonic treatment without damaging the flexible circuit boards.

[0006] In order to achieve the above-mentioned object, the present invention discloses the following method for processing laser blind hole burr of flexible circuit board; the method for processing laser blind hole burr of flexible circuit board comprises:

[0007] Providing a flexible circuit board, copper-plating the flexible circuit board, and laser drilling the copper-plated flexible circuit board to form blind holes in the flexible circuit board;

[0008] Providing a first nylon brush, wherein the first nylon brush has a first preset abrasive mesh, and the first nylon brush performs a first mechanical grinding on the blind hole of the soft board;

[0009] Providing a second nylon brush, the second nylon brush having a second preset abrasive mesh number, the second nylon brush performing a second mechanical grinding on the blind hole of the soft board, and making all the overhanging copper at the opening of the blind hole be brushed flat by the second nylon brush, wherein the second preset abrasive mesh number is greater than the first preset abrasive mesh number;

[0010] Among them, after the step of "plating copper on the soft board", if the soft board is subjected to window opening and copper removal, so that part of the soft board is exposed, then after the soft board is subjected to the second mechanical grinding, the soft board is placed in a cylinder, and liquid medicine is poured into the cylinder and ultrasonic vibration is performed to remove the burrs of the blind holes; after the step of "plating copper on the soft board", if the soft board is not subjected to window opening and copper removal, the soft board is placed in the cylinder, and clean water is poured into the cylinder and the soft board is washed with water.

[0011] Furthermore, two first nylon brushes are provided. During the step of "using the first nylon brush to perform the first mechanical grinding on the blind hole of the soft board", the two first nylon brushes respectively perform the first mechanical grinding at the upper and lower opposite ends of the blind hole of the soft board.

[0012] Furthermore, the number of the second nylon brushes is set to two. After the step of "the first nylon brush performs the first mechanical grinding on the blind hole of the soft board" and before the step of "the second nylon brush performs the second mechanical grinding on the blind hole of the soft board", the two first nylon brushes stop running, the soft board is pushed to the positions of the two second nylon brushes, and then the two second nylon brushes perform the second mechanical grinding at the upper and lower opposite ends of the blind hole of the soft board respectively.

[0013] Furthermore, the two first nylon brushes and the two second nylon brushes are arranged at adjacent positions on the same machine.

[0014] Furthermore, during the steps of "the first nylon brush performs the first mechanical grinding on the blind hole of the soft board" and "the second nylon brush performs the first mechanical grinding on the blind hole of the soft board", the brush voltage current is maintained at 0.5-0.8A and the brush width is maintained at 0.8-1.0mm.

[0015] Furthermore, the first preset abrasive mesh size is 600 mesh, and the second preset abrasive mesh size is 800 mesh.

[0016] Furthermore, in the step of "setting the soft board in a cylinder, pouring a potion into the cylinder and performing ultrasonic vibration so that the burrs of the blind hole are removed", the potion is set to be a biodegradable chemical corrosion inhibitor, and the biodegradable chemical corrosion inhibitor is composed of an organic solvent, a surfactant, a buffer, a corrosion inhibitor and water.

[0017] Furthermore, in the step of "pouring clean water into the cylinder and washing the soft board", the water washing pressure is 75-85kg.

[0018] Furthermore, in the step of "pouring liquid medicine into the cylinder and performing ultrasonic vibration to remove the burrs on the blind hole", the ultrasonic frequency is set to 20kHz to 80kHz.

[0019] By means of the above technical solution, the beneficial effects of the present invention are as follows:

[0020] The laser blind hole burr treatment method of the flexible circuit board of the present invention can achieve a better grinding effect without damaging the flexible circuit board body through two mechanical grindings with different intensities. At the same time, according to the window opening and copper removal of the flexible circuit board, the flexible circuit board is subjected to ultrasonic treatment or only water washing according to the situation of window opening and copper removal, so as to prevent the soft circuit board that has not been windowed and copper removed from being cracked by ultrasonic waves, so that the copper layer of the cracked area may be filled with clean water or chemicals, resulting in the contamination of the board surface of the flexible circuit board. Therefore, by using this method, while ensuring the production yield, a better burr cleaning effect is achieved, and the cost is more favorable than that of plasma cleaning.

[0021] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 This is a schematic diagram of a method for processing laser blind vias on a flexible circuit board after processing according to an embodiment of this specification;

[0024] Figure 2 This is a schematic diagram before processing of a method for processing laser blind vias on a flexible circuit board provided in an embodiment of this specification; DETAILED DESCRIPTION

[0025] To help those skilled in the art better understand the technical solutions in this specification, the following will provide a clear and complete description of the technical solutions in the embodiments of this specification, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this specification, not all of them. All other embodiments derived by those skilled in the art based on the embodiments in this specification without creative effort shall fall within the scope of protection of this specification.

[0026] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0027] It should be understood that although terms such as "first," "second," and "third" may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. In addition, the term "or" as used herein may include any one or more combinations of the associated listed items, as appropriate.

[0028] The following is a method for processing laser blind via burring of a flexible circuit board according to this embodiment; wherein the method for processing laser blind via burring of a flexible circuit board comprises:

[0029] Providing a flexible circuit board, copper plating the flexible circuit board, and laser drilling the copper-plated flexible circuit board to form blind holes on the flexible circuit board;

[0030] Providing a first nylon brush, the first nylon brush having a first preset abrasive mesh, and the first nylon brush performing a first mechanical grinding on the blind hole of the soft plate;

[0031] Providing a second nylon brush, the nylon brush having a second preset abrasive mesh number, the second nylon brush performs a second mechanical grinding on the blind hole of the soft board, and makes all the overhanging copper at the opening of the blind hole be brushed flat by the second nylon brush, wherein the second preset abrasive mesh number is greater than the first preset abrasive mesh number;

[0032] Among them, after the step of "copper plating on the soft circuit board", if the soft circuit board is opened for copper removal so that part of the soft circuit board is exposed, then after the soft circuit board is mechanically polished for the second time, the soft circuit board is placed in a cylinder, and liquid medicine is poured into the cylinder and ultrasonic vibration is performed to remove the burrs of the blind holes; after the step of "copper plating on the soft circuit board", if the soft circuit board is not opened for copper removal, the soft circuit board is placed in a cylinder, and clean water is poured into the cylinder and the soft circuit board is washed with water.

[0033] With the above-described structure, when in use, the operator only needs to prepare the flexible circuit board to be processed. First, a layer of copper foil is plated on the surface of the substrate, either chemically or electrolytically, to prepare for the circuit's electrical conduction. Then, as needed, some areas of the flexible circuit board are opened for copper removal after copper plating. The purpose of this windowing and copper removal is to remove the copper layer from the area of ​​the flexible circuit board, making the surface of the flexible circuit board after the opening windowed ready for other processing steps. Some flexible circuit boards leave the copper-plated areas intact. The next step is to laser drill the flexible circuit board. After drilling, a large amount of waste material appears on the surface or inside the newly formed blind hole, forming burrs at the blind hole opening, which need to be cleaned. The blind hole with burrs is then mechanically polished twice, using a first nylon brush and a second nylon brush of different intensities, to smooth out all the overhanging copper at the blind hole opening. For the plates that have undergone window opening and copper removal, after two mechanical grindings, they are placed in a cylinder, filled with chemicals and ultrasonically treated. During the ultrasonic process, the burrs on the blind holes are removed. For the soft boards that have not undergone window opening and copper removal, this step is skipped and they are directly placed in the cylinder for water washing at a water pressure of 75-85kg to avoid damage to the soft boards during the ultrasonic process.

[0034] Specifically, the physical properties of soft boards are completely different from those of hard boards. Soft boards generally have two layers and can be bent. Therefore, the bonding strength between the copper-plated copper layer and the soft board itself is relatively poor. For soft boards without copper removal windows, ultrasonic treatment may cause the ultrasonic waves to crack the copper layer. Therefore, soft boards without copper removal windows are placed in the same production line as soft boards with copper removal windows for high-pressure water washing and cleaning. This achieves a good balance between cleanliness, quality, and yield rate, and does not require changes to the original equipment of the production line, resulting in higher processing efficiency. Soft boards that have undergone ultrasonic cleaning have excellent cleaning effects, with lower costs and faster processing speeds than traditional plasma cleaning. Figure 2 As an example, the soft board before processing can be achieved as follows Figure 1 The effect of blind hole flash treatment is shown.

[0035] Furthermore, two first nylon brushes are provided. During the step of "the first nylon brush performs a first mechanical polishing on the blind hole of the soft board", the two first nylon brushes respectively perform a first mechanical polishing at positions adjacent to the upper and lower ends of the blind hole of the soft board. Similarly, two second nylon brushes are provided. After the step of "the first nylon brush performs a first mechanical polishing on the blind hole of the soft board" and before the step of "the second nylon brush performs a second mechanical polishing on the blind hole of the soft board", the two first nylon brushes stop operating, the soft board is pushed to the positions of the two second nylon brushes, and then the two second nylon brushes respectively perform a second mechanical polishing at positions adjacent to the upper and lower ends of the blind hole of the soft board. Among them, the two first nylon brushes and the two second nylon brushes are set in adjacent positions on the same machine. That is to say, after the soft board after laser treatment is transported to the grinding machine, the upper and lower surfaces of the soft board are firstly contacted with the first nylon brushes at the two locations, and then the two first nylon brushes are started synchronously and the blind hole position is mechanically ground for the first time. After reaching the preset time, the two first nylon brushes stop, and the machine controls the displacement of the soft board so that the soft board is adjacent to the two second nylon brushes above and below the blind hole, and the second nylon brushes are started to mechanically grind the soft board for the second time, and finally the burrs at the blind hole are removed. With the above method, the same soft board is ground twice with different mesh sizes, so that the brushes are aligned without damaging the soft board body, and the second nylon brush is started to mechanically grind the soft board for the second time, and finally the grinding of the burrs at the blind hole is achieved with the best effect.

[0036] Furthermore, in the two-step mechanical grinding process, the first preset abrasive mesh is 600 mesh, and the second preset abrasive mesh is 800 mesh. The processing strength of 600 mesh can just remove most of the blind hole hanging copper, and the processing strength of 800 mesh can make the hanging copper at the blind hole be completely cleaned and leveled, avoiding long-term 600 mesh coarse grinding to reduce damage and improve fineness. At the same time, during the grinding process, the brush pressure current is maintained at 0.5-0.8A, and the brush width is maintained at 0.8-1.0mm. Compared with the general brush pressure current maintained at 1.0-1.5A and the brush width maintained at 1.0-1.4mm for hard board grinding, the brush pressure current for grinding the soft board in this embodiment is about half of that for grinding the hard board of the same specification, and the brush width for grinding the soft board is about one-quarter of that for grinding the hard board of the same specification, which can strike a balance between the cleaning effect and the material protection of the soft board.

[0037] Furthermore, in the step of "placing the flexible circuit board in a cylinder, pouring a solution into the cylinder, and applying ultrasonic vibration to remove the burrs from the blind holes," the solution is a biodegradable chemical corrosion inhibitor, which is composed of an organic solvent, a surfactant, a buffer, a corrosion inhibitor, and water. The organic solvent is mainly composed of alcohols, ketones, esters, etc., and its purpose is to remove excess colloid on the surface of the flexible circuit board to prevent damage to the flexible circuit board.

[0038] Furthermore, in the step of "filling the cylinder with liquid medicine and performing ultrasonic vibration to remove the burrs from the blind hole," the ultrasonic frequency is set to 45kHz. Of course, ultrasonic frequencies ranging from 20kHz to 80kHz can also achieve certain results, as long as they can effectively separate and remove burrs while ensuring the flatness and smoothness of the blind hole walls. However, 45Hz is most suitable for flexible circuit boards.

[0039] Of course, in this embodiment, there are multiple blind holes on the soft board, wherein a certain number of blind holes are set on both sides of the soft board, and the first nylon brush and the second nylon brush clamp and grind the soft board from top to bottom, so that all the blind holes can be effectively covered. Figure 1 and Figure 2 The figure shows only a single blind hole.

[0040] The contents disclosed above are only preferred feasible embodiments of the present invention and do not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the description and drawings of the present invention are included in the scope of the patent application of the present invention.

[0041] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0042] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present application without departing from the spirit of the present application. It is intended that the appended embodiments include these modifications and variations without departing from the present application.

Claims

1. A method for processing laser blind hole flash of flexible circuit board; characterized in that: The laser blind hole flash processing method of the flexible circuit board includes: Providing a flexible circuit board, copper-plating the flexible circuit board, and laser drilling the copper-plated flexible circuit board to form blind holes in the flexible circuit board; Providing a first nylon brush, wherein the first nylon brush has a first preset abrasive mesh, and the first nylon brush performs a first mechanical grinding on the blind hole of the soft board; Providing a second nylon brush, wherein the second nylon brush has a second preset abrasive mesh number, and the second nylon brush performs a second mechanical grinding on the blind hole of the soft circuit board, so that all the overhanging copper at the opening of the blind hole is brushed flat by the second nylon brush, wherein the second preset abrasive mesh number is greater than the first preset abrasive mesh number; Wherein, after the step of "plating copper on the soft board", if the soft board is subjected to window opening and copper removal, so that part of the soft board is exposed, then after the soft board is subjected to the second mechanical grinding, the soft board is placed in a cylinder, a solution is poured into the cylinder, and ultrasonic vibration is performed to remove the burrs of the blind holes, wherein the solution is set to be a biodegradable chemical corrosion inhibitor, and the biodegradable chemical corrosion inhibitor is composed of an organic solvent, a surfactant, a buffer, a corrosion inhibitor and water; after the step of "plating copper on the soft board", if the soft board is not subjected to window opening and copper removal, the soft board is placed in the cylinder, clean water is poured into the cylinder, and the soft board is washed with water.

2. The method for treating laser blind vias in flexible printed circuits according to claim 1, wherein: The first nylon brushes are provided in two numbers. During the step of "the first nylon brush performs the first mechanical grinding on the blind hole of the soft board", the two first nylon brushes respectively perform the first mechanical grinding at the upper and lower opposite ends of the blind hole of the soft board.

3. The method for treating laser blind via burrs on a flexible printed circuit board according to claim 2, wherein: Two second nylon brushes are provided. After the step of "the first nylon brush performs the first mechanical grinding on the blind hole of the soft board" and before the step of "the second nylon brush performs the second mechanical grinding on the blind hole of the soft board", the two first nylon brushes stop running, the soft board is pushed to the positions of the two second nylon brushes, and then the two second nylon brushes respectively perform the second mechanical grinding at the upper and lower opposite ends of the blind hole of the soft board.

4. The method for treating laser blind vias in flexible printed circuits according to claim 3, wherein: The two first nylon brushes and the two second nylon brushes are arranged at adjacent positions on the same machine.

5. The method for treating laser blind vias in flexible printed circuits according to claim 1, wherein: During the steps of "the first nylon brush performs a first mechanical grinding on the blind hole of the soft board" and "the second nylon brush performs a first mechanical grinding on the blind hole of the soft board", the brush voltage current is maintained at 0.5-0.8A and the brush width is maintained at 0.8-1.0mm.

6. The method for treating laser blind via flash of flexible printed circuit according to claim 1, characterized in that: The first preset abrasive mesh size is 600 mesh, and the second preset abrasive mesh size is 800 mesh.

7. The method for treating laser blind vias in flexible printed circuits according to claim 1, wherein: In the step of "pouring liquid medicine into the cylinder and performing ultrasonic vibration to remove the burrs of the blind hole", the ultrasonic frequency is set to 20kHz to 80kHz.

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