A printed circuit board and a processing method for reducing laser aperture signal loss.

Abstract

This invention belongs to the field of circuit board technology and discloses a printed circuit board and a processing method for reducing laser hole signal loss. The method includes: S1, inner layer pattern fabrication, where no pad is designed at the location where the high-speed line endpoint needs to connect with the laser hole, so that the laser hole can directly connect with the inner layer high-speed line; S2, finding a mechanical hole with a drilling diameter of 0.5mm or more near the laser hole as a reference hole, and designing a pad within the reference hole in the target layer; S3, first performing deep drilling for rough machining, and then performing laser drilling for fine machining, to achieve precise machining of the reference hole depth; S4, obtaining the machining conditions during the laser drilling for fine machining of the reference hole, and determining the laser energy parameters for laser hole machining based on the machining conditions; S5, machining the target laser hole according to the determined laser energy parameters for laser hole machining.

Description

Technical Field

[0001] This invention belongs to the field of circuit board technology and relates to a printed circuit board and a processing method for reducing laser hole signal loss. Specifically, it relates to a printed circuit board processing method that enables direct connection between laser holes and inner high-speed circuits. Background Technology

[0002] With the continuous improvement of data transmission rates, the application of high-frequency, high-speed printed circuit boards (PCBs) is becoming increasingly widespread.

[0003] In traditional PCB manufacturing methods, the connection between laser vias and high-speed circuitry on inner layers is typically achieved using pads. However, the presence of pads can cause impedance discontinuities in the signal transmission path, leading to signal reflection, attenuation, and other problems that severely impact signal integrity.

[0004] In addition, the depth control precision of laser apertures in traditional methods is insufficient, which can easily lead to unstable aperture wall quality and further aggravate signal loss. Summary of the Invention

[0005] Objective: To overcome the shortcomings of the prior art, this invention provides a printed circuit board and a processing method for reducing laser hole signal loss, which effectively reduces signal loss, improves signal integrity, and achieves precise control of laser hole depth.

[0006] Technical solution: The preferred technical solution adopted in this invention is as follows: According to a first aspect of the present invention, a method for reducing laser aperture signal loss in a printed circuit board is provided, comprising: S1. Inner layer pattern creation: For the high-speed line endpoints that need to be connected to the laser holes, no pads are designed so that the laser holes can be directly connected to the inner layer high-speed lines. S2. Find a mechanical hole with a drilling diameter of 0.5mm or more near the laser hole as a reference hole, and design a pad block in the reference hole of the target layer. S3. First, use deep drilling for rough machining, and then use laser drilling for fine machining to achieve precise machining of the reference hole depth; S4. Obtain the processing conditions during the laser drilling fine machining process of the reference hole, and determine the laser energy parameters for laser hole machining based on the processing conditions; S5. Process the target laser hole according to the determined laser energy parameters for laser hole processing.

[0007] In some embodiments, S3, the deep drilling roughing includes: using a mechanical drill bit to rough-machine the reference hole to a depth of 0.1 mm from the target layer, and controlling the drilling depth error within ±0.05 mm.

[0008] Furthermore, during the deep drilling roughing process, nitrogen is used as an auxiliary gas at a pressure of 0.5 MPa to remove debris generated during drilling.

[0009] In some embodiments, S3, the laser drilling fine processing includes: using laser drilling technology to fine process the reference hole, and adjusting the laser parameters to ensure that the depth accuracy of the reference hole reaches ±0.005mm; the laser parameters include laser power, pulse width, and focal position.

[0010] Furthermore, the laser drilling and fine machining process uses a UV laser with a wavelength of 355nm, a laser power of 8-15W, a pulse width of 20-50ns, and a focal position located 10-20μm below the surface of the board.

[0011] In some embodiments, S4, the processing conditions include laser energy, drilling speed, and hole wall temperature.

[0012] In some embodiments, in S5, the laser hole processing employs graded power control, with initial power used to remove copper foil, followed by a reduction in power to finely process the resin layer.

[0013] In some embodiments, in S2, the diameter of the baffle pad is designed to be about 0.3 mm; the annular ring width between the baffle pad and the edge of the reference hole is not less than 0.1 mm.

[0014] In some embodiments, after the target laser hole is processed, the process further includes S6, post-processing: drilling a reference hole in the mechanical hole processing step.

[0015] According to a second aspect of the present invention, a printed circuit board is provided, which is obtained by the method described above.

[0016] Beneficial effects: This invention provides a processing method for reducing laser aperture signal loss in printed circuit boards, which has the following advantages: 1. Improved signal integrity: By eliminating the pad design at the high-speed line endpoints, the laser aperture is directly connected to the inner high-speed line, effectively reducing signal reflection and attenuation and improving signal integrity.

[0017] 2. High depth control accuracy: The scheme adopts a combination of deep drilling roughing and laser fine machining, with a reference hole depth accuracy of ±0.01mm, providing accurate parameter basis for laser hole machining and ensuring that the depth of all laser holes meets the requirements.

[0018] 3. Improved processing efficiency: By using existing mechanical holes as reference holes, there is no need to design additional targets, which simplifies the process and reduces production costs.

[0019] 4. Strong compatibility: This method is applicable to a variety of PCB materials (such as FR-4, polyimide, etc.) and is compatible with existing PCB manufacturing equipment. Attached Figure Description

[0020] Figure 1 A schematic flowchart illustrating a method for processing a printed circuit board according to an embodiment of the present invention; Figure 2 This is a side view of the printed circuit board product prepared according to an embodiment of the present invention; Figure 3 This is a top view schematic diagram of the printed circuit board product prepared according to an embodiment of the present invention; In the diagram, the laser passes through layer 1, high-speed line 2, and laser aperture ring 3. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0024] This invention provides a method for reducing laser aperture signal loss in printed circuit boards. This method is applicable to the fabrication of the printed circuit boards provided in this invention. Figure 1 A flowchart illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention is shown below. Figure 1 As shown, a processing method for reducing laser aperture signal loss in a printed circuit board includes: S1. Inner layer pattern creation: When creating the inner layer pattern, no pads are designed for the high-speed line endpoints that need to be connected to the laser holes, so that the laser holes can be directly connected to the inner layer high-speed lines.

[0025] It should be noted that in step S1, no pad is designed to allow the laser hole to be directly connected to the inner high-speed circuit. This technical solution avoids the influence of the pad on the signal, thereby reducing signal reflection and attenuation and improving signal integrity.

[0026] S2. Reference hole selection and pad design: Find a mechanical hole with a drill diameter of 0.5mm or more near the laser hole as a reference hole, and design a pad within the reference hole of the target layer.

[0027] Furthermore, the diameter of the resist pad is designed to be approximately 0.3 mm; the annular width between the resist pad and the edge of the reference hole is not less than 0.1 mm.

[0028] It should be noted that the diameter of the resist pad is designed to be approximately 0.3mm to ensure accurate positioning reference for laser hole processing without affecting subsequent mechanical hole processing.

[0029] In addition, ensuring that the annular ring width between the pad and the edge of the reference hole is not less than 0.1 mm is to comply with the IPC-2222 standard requirements.

[0030] S3. First, use deep drilling for rough machining, and then use laser drilling for fine machining to achieve precise machining of the reference hole depth.

[0031] The deep drilling roughing process includes: using a CNC drilling machine's mechanical drill bit to rough-machine the reference hole to a depth of 0.1 mm from the target layer, controlling the drilling depth error within ±0.05 mm.

[0032] Furthermore, during the deep drilling roughing process, nitrogen is used as an auxiliary gas at a pressure of 0.5 MPa to remove debris generated during drilling, thereby improving the hole wall quality.

[0033] The laser drilling fine processing includes: using laser drilling technology to fine process the reference hole, and adjusting the laser parameters to ensure that the depth accuracy of the reference hole reaches ±0.005mm; the laser parameters include laser power, pulse width, and focal position.

[0034] In some embodiments, the laser drilling fine processing uses a UV laser with a wavelength of 355nm, a laser power of 8-15W, a pulse width of 20-50ns, and a focal position located 10-20μm below the surface of the plate.

[0035] More specifically, in some embodiments, the laser drilling fine machining includes: fixing the rough-machined PCB board onto the worktable of the laser drilling equipment, and using the through holes drilled by the X-ray target machine as coarse positioning coordinates. A UV laser (wavelength 355nm) is used to fine-machine the reference holes, with the laser power set to 10W, pulse width 30ns, and the focal point located 10μm below the surface of the board. A spiral scanning mode is used, with a scanning speed of 500mm / s, repeated 3 times to ensure hole wall smoothness and depth accuracy.

[0036] S4. Processing Condition Acquisition and Parameter Adjustment: Acquire the processing conditions during the laser drilling fine machining process of the reference hole, and determine the laser energy parameters for laser hole machining based on the processing conditions; wherein the processing conditions include laser energy, drilling speed and hole wall temperature; During the fine machining of a reference hole using laser drilling technology, machining conditions, including laser energy, drilling speed, and hole wall temperature, are acquired in real time. Based on these acquired conditions, the laser parameters are automatically adjusted by a closed-loop control system. S5. Laser Hole Machining: Machin the target laser holes according to the determined laser energy parameters for laser hole machining, ensuring that the machining depth of all laser holes meets the requirements.

[0037] Furthermore, the laser hole processing employs graded power control. The initial power is used to remove the copper foil, and then the power is reduced to finely process the resin layer. More specifically, the initial power of 15W is used to remove the copper foil, and then the power is reduced to 8W to finely process the resin layer, ensuring the consistency of the laser hole depth and diameter.

[0038] It should be noted that the correlation model between the laser energy parameter E and the penetration depth D of the dielectric layer is as follows: E=k・(D・ρ・C p ) / (α・(1-R)) Where E represents the laser energy parameter, k represents the material heat loss correction factor, D represents the penetration depth of the dielectric layer, ρ represents the dielectric density, and C... p Let α represent the specific heat capacity, α represent the absorption coefficient, and R represent the surface reflectivity.

[0039] In practical applications, after laser hole processing is completed, a plasma cleaning process is performed to remove carbon residue on the hole wall and improve the quality of subsequent metallization.

[0040] Then, following the standard procedures, processes such as outer layer circuit fabrication, electroplating, and solder masking are carried out to finally produce a PCB circuit board that meets the requirements.

[0041] In some embodiments, after the target laser hole is processed, the process further includes S6, post-processing: drilling a reference hole in the mechanical hole processing step.

[0042] It should be noted that the reference hole is used for positioning and reference during the machining process, and this hole will be drilled in the subsequent mechanical hole machining.

[0043] Application Examples:

[0044] Objective: To fabricate blind vias with a depth of 80μm on a 6-layer FR-4 PCB without an underlying copper baffle.

[0045] Parameters: Ultraviolet laser (wavelength 355nm), initial pulse energy 3mJ, frequency 20kHz, spot diameter 30μm.

[0046] process: 1. First layer processing (0-30μm): Energy 4mJ, rapid removal of surface copper layer; 2. Intermediate layer (30-70μm): Energy is linearly reduced to 2mJ to avoid overheating; 3. Bottom layer trimming (70-80μm): Energy 1mJ + pulse number control, accuracy ±2μm.

[0047] Result: The bottom of the hole was flat, the underlying medium was undamaged, and no baffle layer was required.

[0048] The processing method for reducing laser hole signal loss in a printed circuit board disclosed in this application has the following advantages: 1. Improved signal integrity: By eliminating the pad design at the high-speed line endpoints, the laser aperture is directly connected to the inner high-speed line, effectively reducing signal reflection and attenuation and improving signal integrity.

[0049] 2. High depth control accuracy: The scheme adopts a combination of deep drilling roughing and laser fine machining, with a reference hole depth accuracy of ±0.01mm, providing accurate parameter basis for laser hole machining and ensuring that the depth of all laser holes meets the requirements.

[0050] 3. Improved processing efficiency: By using existing mechanical holes as reference holes, there is no need to design additional targets, which simplifies the process and reduces production costs.

[0051] 4. Strong compatibility: This method is applicable to a variety of PCB materials (such as FR-4, polyimide, etc.) and is compatible with existing PCB manufacturing equipment.

[0052] Based on the same inventive concept, embodiments of the present invention also provide a printed circuit board, such as... Figure 2 , Figure 3 As shown, the printed circuit board is manufactured using the method provided in any embodiment of the present invention, and has the same beneficial effects as the above method. Please refer to the above description, which will not be repeated here.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A processing method for reducing laser aperture signal loss in printed circuit boards, characterized in that, include: S1. Inner layer pattern creation: For the high-speed line endpoints that need to be connected to the laser holes, no pads are designed so that the laser holes can be directly connected to the inner layer high-speed lines. S2. Find a mechanical hole with a drilling diameter of 0.5mm or more near the laser hole as a reference hole, and design a pad block in the reference hole of the target layer. S3. First, use deep drilling for rough machining, and then use laser drilling for fine machining to achieve precise machining of the reference hole depth; S4. Obtain the processing conditions during the laser drilling fine machining process of the reference hole, and determine the laser energy parameters for laser hole machining based on the processing conditions; S5. Process the target laser hole according to the determined laser energy parameters for laser hole processing; In S3, the deep drilling roughing process includes: using a mechanical drill bit to rough-machine the reference hole to a depth of 0.1 mm from the target layer, and controlling the drilling depth error within ±0.05 mm; during the deep drilling roughing process, nitrogen is used as an auxiliary gas with a pressure set to 0.5 MPa to remove debris generated during the drilling process. In S3, the laser drilling fine processing includes: using laser drilling technology to fine process the reference hole, and adjusting the laser parameters to ensure that the depth accuracy of the reference hole reaches ±0.005mm; the laser parameters include laser power, pulse width, and focal position; the laser drilling fine processing uses a UV laser with a wavelength of 355nm, a laser power of 8-15W, a pulse width of 20-50ns, and a focal position located 10-20μm below the surface of the board.

2. The method according to claim 1, characterized in that, In S4, the processing conditions include laser energy, drilling speed, and hole wall temperature.

3. The method according to claim 1, characterized in that, In S5, the laser hole processing employs graded power control, with initial power used to remove copper foil, followed by power reduction to finely process the resin layer.

4. The method according to claim 1, characterized in that, In S2, the diameter of the baffle pad is designed to be about 0.3mm; the annular width between the baffle pad and the edge of the reference hole is not less than 0.1mm.

5. The method according to claim 1, characterized in that, After the target laser hole is processed, the process also includes S6, post-processing: in the mechanical hole processing step, the reference hole is drilled.

6. A printed circuit board, characterized in that, It is prepared by the method described in any one of claims 1-5.

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