Processing method of cross-layer blind hole of printed board

Abstract

The invention discloses a processing method for a cross-layer blind hole of a printed board, and belongs to the technical field of printed circuit boards, and the processing method for the cross-layer blind hole of the printed board comprises the following steps: firstly, carrying out depth-controlled mechanical drilling, and then burning off redundant dielectric materials by using laser drilling until a copper foil of a target core board is exposed, so that the cross-layer blind hole is processed. The problem that laser drilling cannot be achieved through combined laser due to the fact that the thickness of a laminated plate is too large or the copper thickness of a core plate is too large is solved. The processing procedure is simple and reliable, repeated test board making is not needed, the cost is saved, and the quality of the finished printed board is improved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, in particular to a method for processing cross-layer blind holes in printed circuit boards. Background Art

[0002] Currently, mature laser processes are single laser processes such as carbon dioxide laser and UV laser, which cannot meet the increasingly diversified and complex PCB process requirements. The combined laser process is a new process that uses dual lasers for coaxial combined processing without poor alignment accuracy, and can solve some technical difficulties that cannot be solved by a single laser.

[0003] Laser processing equipment is an integrated device that generates a high-energy laser beam through electrically stimulated oscillation, focuses it into a small spot through a series of optical devices, and then irradiates it onto the surface of the material to form processing. Nanoseconds, picoseconds, and femtoseconds in laser processing equipment refer to the time control unit in the laser processing process. Usually, laser processing is a single pulse of energy acting on the surface of the material in a very short time, and through high-frequency repetitive work, it forms applications such as drilling, cutting, marking, and welding.

[0004] However, if the design in the stackup requires blind holes to be achieved through cross-layer laser drilling, the board thickness is too thick or the core board copper thickness is too thick, laser drilling cannot be achieved through combined laser. Summary of the invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for processing cross-layer blind holes in a printed circuit board, which can realize the processing of cross-layer blind holes in thick plates and thick copper core plates.

[0006] The method for processing a cross-layer blind hole of a printed circuit board according to an embodiment of the present invention comprises:

[0007] Step 1: alternately stack and press the multi-layer core board and the multi-layer prepreg to firmly bond the core board and the prepreg;

[0008] Step 2: Use a mechanical drilling device to perform depth-controlled drilling on the laminated multilayer board structure. According to the designed depth of the blind hole, the mechanical drilling reaches the corresponding target core board, but does not penetrate the copper foil of the target core board;

[0009] Step 3: After the controlled depth mechanical drilling is completed, use laser drilling to burn off the excess dielectric material until the copper foil of the target core board is exposed, and a cross-level blind hole is processed;

[0010] Step 4: Metallize the blind holes.

[0011] The method for processing cross-layer blind holes in printed circuit boards according to the embodiments of the present invention has at least the following beneficial effects: the method for processing cross-layer blind holes in printed circuit boards first performs controlled-depth mechanical drilling, and then uses laser drilling to burn off excess dielectric materials until the copper foil of the target core board is exposed, thereby processing cross-layer blind holes. The problem that laser drilling cannot be achieved by combined lasers when the thickness of the laminated board is too thick or the copper thickness of the core board is too thick is solved. The processing procedure is simple and reliable, and there is no need to repeatedly make test boards, which saves costs and improves the quality of finished printed circuit boards.

[0012] According to some embodiments of the present invention, in step 3, the laser drilling is carbon dioxide laser drilling.

[0013] According to some embodiments of the present invention, in step 3, the laser drilling is UV laser drilling.

[0014] According to some embodiments of the present invention, in step 3, the laser drilling is a combination of a carbon dioxide laser and a UV laser.

[0015] According to some embodiments of the present invention, in step 4, the metallization process includes chemical copper plating and electroplating.

[0016] According to some embodiments of the present invention, in step 4, a resin material is used to fill the blind hole after metallization is completed.

[0017] According to some embodiments of the present invention, in step 3, during the process of laser drilling to burn off excess dielectric material, the energy output of the laser and the drilling progress are monitored by a real-time monitoring system.

[0018] According to some embodiments of the present invention, before the metallization process is performed in step 4, the inner wall of the blind hole is cleaned to improve the adhesion and conductivity of the metal layer.

[0019] According to some embodiments of the present invention, after mechanically drilling the plate in step 2, the hole wall is cooled.

[0020] According to some embodiments of the present invention, the cooling process includes spraying a cooling liquid or a cooling gas toward the hole wall.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is a flow chart of a method for processing cross-layer blind vias of a printed circuit board according to an embodiment of the present invention;

[0024] Figure 2 yes Figure 1 A schematic diagram of the structure of the pressing process in step 1;

[0025] Figure 3 yes Figure 1 The structural diagram of the second controlled depth mechanical drilling process in step 2;

[0026] Figure 4 yes Figure 1 The schematic diagram of the structure of the laser drilling process in step 3;

[0027] Figure 5 yes Figure 1 The schematic diagram of the structure of the laser drilling process in step 4;

[0028] Reference numerals:

[0029] Core board 100 ; target core board 110 ; prepreg 200 . DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0032] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0033] refer to Figures 1 to 4 A method for processing cross-layer blind vias of a printed circuit board according to an embodiment of the present invention is described.

[0034] like Figures 1 to 4 As shown, the method for processing a cross-layer blind hole of a printed circuit board according to an embodiment of the present invention includes:

[0035] Step 1: alternately stack and press the multi-layer core board 100 and the multi-layer prepreg 200 to firmly combine the core board 100 and the prepreg 200;

[0036] Step 2: On the laminated multilayer board structure, a mechanical drilling device is used to perform depth-controlled drilling. According to the designed depth of the blind hole, the mechanical drilling device is used to drill to the corresponding target core board 110 , but does not penetrate the copper foil of the target core board 110 ;

[0037] Step 3: After the controlled depth mechanical drilling is completed, laser drilling is used to burn off excess dielectric material until the copper foil of the target core board 110 is exposed, thereby processing a cross-layer blind hole;

[0038] Step 4: Metallize the blind holes.

[0039] like Figure 1 As shown, the core board 100 is the base material of the PCB, usually composed of glass fiber and epoxy resin, while the prepreg 200 is a pre-impregnated material for interlayer connection. The lamination process is carried out under high temperature and high pressure to ensure a strong bond between the core board 100 and the prepreg 200. During the lamination process, the control of temperature and pressure is crucial to avoid excessive thermal damage or incomplete curing of the material. After the lamination is completed, a new multi-layer board structure is formed, ready for the subsequent drilling process.

[0040] like Figure 2 As shown, mechanical drilling equipment is used to perform controlled depth drilling on the laminated multilayer board structure. Blind holes are holes that start from one surface of the PCB but do not penetrate to the other surface. The key to this step is to control the depth of the drilling to ensure that the target core board 110 is drilled, but the copper foil of the target core board 110 is not penetrated. In this embodiment, the target core board 110 is the third-layer core board 100, so it is ensured that the third-layer core board 100 is drilled, but the copper foil of the third-layer core board 100 is not penetrated. This step requires precise mechanical drilling equipment and precise depth control technology to ensure the accuracy and consistency of the drilling. During the drilling process, special drill bits and coolants can be used to improve drilling efficiency and drill bit life.

[0041] like Figure 3 As shown, after the controlled depth mechanical drilling is completed, laser drilling technology is used to burn off excess dielectric material until the copper foil of the core board 100 and the target core board 110 is exposed. This step can use a carbon dioxide laser, a UV laser, or a combination of a carbon dioxide laser and a UV laser. The advantage of laser drilling lies in its high precision and flexibility, which can accurately remove materials in a specified area without affecting the surrounding structure. During the laser drilling process, the energy, pulse width and scanning speed of the laser need to be precisely controlled to ensure the effective removal of the dielectric material while avoiding damage to the copper foil.

[0042] like Figure 4As shown, the processed blind holes are metallized to facilitate subsequent electrical connections. Metallization usually includes chemical copper plating and electroplating to form a conductive metal layer on the hole wall. After metallization is completed, you can choose to perform resin plugging or not plugging according to the requirements of the PCB design. Resin plugging is to fill the blind holes with specific resin materials to provide mechanical support and protection, and also to prevent dirt from accumulating in the holes. If plugging is not performed, it is necessary to ensure the cleanliness and protection of the blind holes to avoid contamination in the subsequent production process.

[0043] Therefore, the processing method of the cross-layer blind hole of the printed circuit board adopts the method of first performing controlled depth mechanical drilling, and then using laser drilling to burn off the excess dielectric material until the copper foil of the target core board 110 is exposed, thereby processing the cross-layer blind hole. The problem that the thickness of the laminated board is too thick or the copper thickness of the core board 100 is too thick, laser drilling cannot be achieved by combined lasers is solved. The processing procedure is simple and reliable, and there is no need to repeatedly make test boards, which saves costs and improves the quality of the finished printed circuit board.

[0044] In some specific embodiments of the present invention, in step 3, the laser drilling is carbon dioxide laser drilling. Using carbon dioxide laser drilling can provide a high-energy laser beam to effectively burn off excess dielectric materials. At the same time, the wavelength of carbon dioxide laser is longer and the absorption rate of materials is higher, which can improve drilling efficiency and processing quality.

[0045] In some specific embodiments of the present invention, in step 3, the laser drilling is UV laser drilling. UV laser drilling has a shorter wavelength, can provide higher precision and finer processing effects, is particularly suitable for processing fine circuits and tiny apertures, and helps to improve the manufacturing accuracy of PCBs.

[0046] In some specific embodiments of the present invention, in step 3, the laser drilling is a combination of a carbon dioxide laser and a UV laser. Combining the advantages of the two lasers, more complex and sophisticated processing requirements can be achieved while improving processing efficiency and quality. This combination of laser drilling can adapt to the processing of different materials and thicknesses, improving the flexibility and scope of application of the processing.

[0047] In step 4, the metallization treatment includes chemical copper plating and electroplating. The combination of chemical copper plating and electroplating can ensure the uniformity and integrity of the metal layer on the inner wall of the blind hole, improve the conductivity and mechanical strength, and provide guarantee for the subsequent electrical connection and PCB performance.

[0048] In step 4, the blind holes are filled with resin material after metallization is completed. Filling the blind holes with resin material can provide additional mechanical support, reduce stress concentration in the holes, prevent dirt from hiding in the holes, and improve the reliability and durability of the PCB.

[0049] In step 3, during the laser drilling process to burn off the excess dielectric material, the laser energy output and drilling progress are monitored by the real-time monitoring system. The real-time monitoring system can ensure the stability and consistency of the laser drilling process, detect and adjust the deviation in the processing process in time, and improve the processing accuracy and production efficiency.

[0050] Before metallization in step 4, the inner wall of the blind hole is cleaned to improve the adhesion and conductivity of the metal layer. Cleaning can remove residues and contaminants on the hole wall, improve the bonding strength between the metal layer and the hole wall, reduce defects in the metallization process, and improve the reliability of the PCB.

[0051] After mechanical drilling of the plate in step 2, the hole wall is cooled. The cooling treatment includes spraying coolant or cooling gas to the hole wall. Cooling the hole wall after mechanical drilling can quickly reduce the hole wall temperature, reduce the heat affected area, avoid deformation or damage of the material due to high temperature, and help maintain the dimensional stability of the PCB.

[0052] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A method for processing cross-layer blind holes in a printed circuit board, characterized in that: include: Step 1: alternately stack and press the multi-layer core board and the multi-layer prepreg to firmly bond the core board and the prepreg; Step 2: Use a mechanical drilling device to perform depth-controlled drilling on the laminated multilayer board structure. According to the designed depth of the blind hole, the mechanical drilling reaches the corresponding target core board, but does not penetrate the copper foil of the target core board; Step 3: After the controlled depth mechanical drilling is completed, use laser drilling to burn off the excess dielectric material until the copper foil of the target core board is exposed, and a cross-level blind hole is processed; Step 4: Metallize the blind holes.

2. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: In step 3, the laser drilling is carbon dioxide laser drilling.

3. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: In step 3, the laser drilling is UV laser drilling.

4. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: In step 3, the laser drilling is a combination laser drilling of a carbon dioxide laser and a UV laser.

5. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: In step 4, the metallization process includes chemical copper plating and electroplating.

6. The method for processing cross-layer blind holes in a printed circuit board according to claim 5, characterized in that: In step 4, the blind holes are filled with resin material after metallization is completed.

7. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: In step 3, during the process of laser drilling to burn off excess dielectric material, the energy output of the laser and the drilling progress are monitored by a real-time monitoring system.

8. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: Before the metallization process is performed in step 4, the inner wall of the blind hole is cleaned to improve the adhesion and conductivity of the metal layer.

9. The method for processing cross-layer blind holes in a printed circuit board according to claim 1, characterized in that: After the plate is mechanically drilled in step 2, the hole wall is cooled.

10. The method for processing cross-layer blind holes in a printed circuit board according to claim 9, characterized in that: The cooling process includes spraying cooling liquid or cooling gas onto the hole wall.

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