Drilling method for laser X-shaped through hole of circuit board and circuit board

Abstract

The invention provides a drilling method for a laser X-shaped through hole of a circuit board and the circuit board, and the drilling method for the laser X-shaped through hole of the circuit board comprises the steps: covering a dry film on the surface of a copper-clad plate; patterning the dry film to form a mask coverage area and a non-mask area corresponding to the position of the preset positioning target; removing the dry film in a non-mask area; carrying out brownification treatment to change the color of the copper surface of the copper-clad plate in the non-mask area; and performing laser drilling on the copper-clad plate based on a positioning target by using the characteristic difference between the non-mask region and the mask coverage region as the positioning target. The characteristic difference between the color-changing copper surface in the non-mask area and the non-color-changing copper surface below the mask covering area is used as a positioning target of laser drilling. A traditional low-precision mechanical drilling positioning mode is replaced, the positioning reference is directly generated on the plate surface by utilizing the high-precision characteristic of the photoetching technology, the manufacturing precision of the positioning target is fundamentally improved, and the positioning target is particularly suitable for drilling scenes with strict position precision requirements and is beneficial for improving the product yield and reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit board, and particularly relates to a laser X-shaped via hole drilling method of a circuit board and the circuit board. BACKGROUND

[0002] In the field of modern electronic packaging and circuit board manufacturing, laser drilling technology is widely used because it can manufacture micro-aperture, high aspect ratio through holes. These through holes are the key structure to realize the electrical connection between multiple layers of circuits, and the manufacturing precision directly affects the performance and reliability of the product.

[0003] At present, when laser drilling is performed on a circuit board substrate, especially in scenarios requiring high-precision positioning, such as manufacturing small-aperture through holes, blind holes, buried holes, or double-sided drilling structures requiring accurate alignment, a common process flow relies on pre-made reference features. This flow usually includes making positioning holes on the substrate by mechanical drilling. The laser drilling machine uses these mechanical positioning holes as the reference for the device vision system to recognize and align, and then performs laser ablation to form the required through holes.

[0004] However, as the integration of circuit design continues to improve, the requirements for through hole aperture, position accuracy and alignment accuracy are becoming more and more stringent. The traditional laser drilling method relying on mechanical positioning holes exposes obvious technical bottlenecks. Mechanical drilling itself has inherent tolerances, typically about ±0.03mm. When the laser drilling machine aligns based on this, the initial positioning error is directly transferred and superimposed on the final drilling position accuracy. Considering the laser drilling machine's own alignment error, typically about ±0.02mm, the substrate material's deformation error during processing, typically about ±0.01mm, and the laser drilling process error, typically about ±0.01mm, the overall alignment accuracy limit achieved by using mechanical positioning holes is about 0.039mm. For applications requiring high-precision alignment, such as manufacturing small-aperture through holes or through holes that need to be accurately intersected from both sides, this level of accuracy often cannot meet the requirements, easily leading to poor hole wall connection, alignment deviation, or even open circuit defects, seriously affecting product yield and electrical performance.

[0005] Therefore, there is a need to improve the existing drilling technology to overcome the deficiencies of the prior art. SUMMARY

[0006] To overcome the problems in the related art, one of the purposes of the present application is to provide a laser X-shaped via hole drilling method of a circuit board, which makes high-precision optical positioning targets by adopting photochemical patterning combined with surface treatment, instead of traditional mechanical positioning holes, to overcome the low yield and low reliability caused by the large error of mechanical positioning holes in the prior art.

[0007] A laser X-shaped via hole drilling method of a circuit board, comprising:

[0008] covering a dry film on a surface of a copper-clad plate;

[0009] patterning the dry film to form a mask-covered area and a non-mask area corresponding to a preset positioning target position;

[0010] removing the dry film located in the non-mask area;

[0011] brown processing to cause the copper surface of the copper-clad plate located in the non-mask area to discolor;

[0012] using the feature difference between the non-mask area and the mask-covered area as a positioning target, and performing laser drilling on the copper-clad plate based on the positioning target to form an X-shaped via hole.

[0013] By covering a dry film on the surface of a copper-clad plate, patterning the dry film to form a mask-covered area and a non-mask area, and removing part of the dry film, and then performing brown processing, the feature difference between the non-discolored copper surface of the non-mask area and the mask-covered area (the underlying non-discolored copper surface) is ingeniously used to make a positioning target for laser drilling. Instead of the traditional low-precision mechanical drilling positioning method, the positioning reference is directly generated on the plate surface using the high-precision characteristics of photolithography technology, which fundamentally improves the manufacturing precision of the positioning target itself and lays a foundation for high-precision positioning in subsequent laser drilling. It is especially suitable for small-diameter or precision alignment drilling scenarios that require high positioning accuracy, and helps to improve product yield and reliability.

[0014] Further, the step of patterning the dry film specifically includes exposing the dry film according to a pattern corresponding to the preset positioning target position using a laser direct imaging machine.

[0015] Using a laser direct imaging machine (LDI) for the patterned exposure of the dry film can further improve the transfer precision and resolution of the positioning target pattern. Compared with the traditional mask exposure method, LDI does not require a physical mask, avoiding problems such as mask manufacturing errors, expansion and deformation, and alignment errors, and can achieve higher-precision direct writing of patterns, thereby making the final positioning target pattern more accurate and further improving the positioning accuracy of laser drilling based on the target.

[0016] Further, the dry film is a light-colored dry film or a transparent dry film.

[0017] Using light-colored dry film or transparent dry film, the optical contrast between the non-discolored copper surface (usually bright copper color) under the mask covered area and the discolored copper surface (usually dark brown or black) in the non-masked area after the brown process can be maximized. This high contrast enables the visual recognition system of the laser drilling machine to capture and recognize the positioning target more clearly, stably and quickly, improves the stability and accuracy of target recognition, reduces the possibility of misjudgment, and ensures the reliable implementation of high-precision positioning.

[0018] Further, the feature difference includes the color difference and / or the light reflection ability difference between the discolored copper surface of the non-masked area and the non-discolored copper surface under the mask covered area.

[0019] The copper-clad plate has a first copper-clad surface and a second copper-clad surface, and both the first copper-clad surface and the second copper-clad surface are provided with a predetermined positioning target;

[0020] The step of laser drilling the copper-clad plate based on the positioning target includes:

[0021] Based on the positioning target on the first copper-clad surface, a first laser drilling is performed from the first copper-clad surface;

[0022] Based on the positioning target on the second copper-clad surface, a second laser drilling is performed from the second copper-clad surface, so that the first laser drilling and the second laser drilling intersect inside the copper-clad plate to form the X-shaped via.

[0023] Positioning targets are arranged on both the first and second copper-clad surfaces of the copper-clad plate, respectively for the alignment of the first and second laser drillings. This can significantly improve the alignment accuracy (i.e., reduce the vertical deviation) at the intersection of the two components of the X-shaped via (blind holes drilled from both sides). Compared with the traditional method, this double-sided high-precision alignment can more reliably ensure good connection of the X-shaped via, which is particularly critical for small-aperture X-shaped vias, effectively improving the manufacturing success rate and electrical performance of such complex interconnection structures.

[0024] Further, before the step of performing the second laser drilling from the second copper-clad surface based on the positioning target on the second copper-clad surface, the method further includes:

[0025] A protective copper foil is laminated on the first copper-clad surface.

[0026] Before performing the second laser drilling on the second copper-clad surface, a protective copper foil is laminated on the first copper-clad surface, solving the problem of damage to the equipment table surface caused by laser penetration drilling in the prior art. As a sacrificial layer, the protective copper foil can effectively absorb the excess laser energy penetrating the substrate, avoiding direct ablation of the laser drilling machine worktable surface, thereby protecting the equipment, prolonging its service life, and helping to maintain the flatness and precision of the table surface, ensuring the stability of subsequent processing.

[0027] Further, after the second laser drilling from the second copper clad surface based on the positioning target on the second copper clad surface, the method further comprises:

[0028] removing the protective copper foil.

[0029] The protective copper foil is removed after the second laser drilling on the second copper clad surface is completed, ensuring the temporary nature of the protective measures. This does not hinder subsequent PCB manufacturing processes (such as desmear, electroplating, circuit fabrication, etc.).

[0030] Further, the step of pressing the protective copper foil on the first copper clad surface specifically comprises:

[0031] The vacuum film presser is used to press the copper foil on the first copper clad surface.

[0032] By using a vacuum film presser to press the protective copper foil, compared with the simple placement of sacrificial pieces, it can ensure that the protective copper foil is flat, bubble-free, and firmly attached to the surface of the first copper clad plate. This close fit not only provides more uniform and reliable table protection, but more importantly, it can effectively fix the substrate and prevent it from moving or vibrating slightly under the impact of laser drilling on the second copper clad surface, thereby improving the stability of the processing process and further ensuring the position accuracy of drilling. It is a further enhancement of the protective effect and precision protection.

[0033] The second purpose of the present application is to provide a circuit board made by the above method.

[0034] Due to the use of high-precision positioning target manufacturing method and (when applicable) stable protective pressing process, the X-shaped via has higher position accuracy and alignment accuracy. The final circuit board has more reliable electrical connections and lower manufacturing defect rates, especially in fine lines, small apertures, and high-density interconnection designs, which can exhibit superior electrical performance and long-term reliability.

[0035] The beneficial effects of the present application are:

[0036] The application provides a laser X-shaped via hole drilling method for a circuit board. The laser X-shaped via hole drilling method for the circuit board is performed by sequentially performing dry film coating, dry film patterning to define mask and non-mask areas, selective dry film removal and subsequent brown oxidation treatment on the surface of the copper-clad board. The method cleverly constructs an area with significant feature difference (i.e. the brown-oxidized copper surface and the non-discolored copper surface protected by the dry film) on the surface of the copper-clad board, and uses the feature difference as a positioning target for laser drilling. This positioning target manufacturing method based on photochemical patterning and surface treatment fundamentally replaces the traditional method of making positioning holes by relying on low-precision mechanical drilling. Since the photoetching patterning technology (such as exposure and development) can achieve much higher pattern precision than mechanical drilling, the positioning target produced by the method has higher position and shape precision. This provides a solid foundation for the subsequent laser drilling step to achieve high-precision positioning, which is of great significance for manufacturing circuit boards with small hole diameter, high density and strict alignment accuracy (such as HDI boards, carrier boards and IC carrier boards), and can effectively improve the position accuracy of the final drilling, reduce defects caused by positioning errors, and thus improve product yield and electrical connection reliability. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 FIG. 1 is a schematic diagram of the laser X-shaped via hole drilling method for a circuit board provided in the present application. DETAILED DESCRIPTION

[0038] Preferred embodiments of the present application will be described in more detail with reference to the drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0039] The X-shaped via hole involved in the present application is also commonly referred to as an hourglass-shaped via hole or a reverse drilling structure, which is a special through-hole structure. It is usually formed by drilling two blind holes from opposite sides of the circuit board, which accurately intersect at a predetermined depth inside the circuit board. The hole wall of this structure converges in the middle region, forming a profile similar to the letter "X" or an hourglass. The X-shaped via hole has advantages in certain application scenarios due to its unique structure, such as improving plating uniformity in thicker circuit boards or being used for impedance control in certain high-frequency designs. However, the manufacturing of X-shaped via holes requires high alignment accuracy of the two component blind holes, and any significant alignment deviation can cause poor connection, reduced reliability, or even open circuit problems, especially in the case of small hole diameter. The present application is proposed to improve the drilling accuracy of such X-shaped via holes.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a method for drilling X-shaped through-holes in a circuit board and a circuit board for use with copper-clad laminates having X-shaped through-holes with a diameter of 50 μm. The drilling method includes:

[0042] Step S101: Substrate preparation

[0043] Select a suitable copper-clad laminate substrate and cut it into 305mm x 457mm pieces. Bake the copper-clad laminate at 150℃ for 240 minutes to remove internal moisture and reduce deformation caused by heat during subsequent processing. Clean the surface with a cleaning agent to remove oxides, oil, and other contaminants, ensuring a clean surface.

[0044] Step S102: Apply dry film

[0045] The cleaned and dried copper-clad laminate is fed into the laminator. A light-colored or transparent photosensitive dry film is selected (e.g., a transparent negative dry film). The lamination is performed at a temperature of 110℃±10℃ and a pressure of 4-6 kg / cm². 2 The dry film is evenly and smoothly applied to both sides of the copper-clad laminate. The dry film surface should be smooth, free of bubbles and wrinkles after application. A light-colored or transparent dry film is chosen to maximize the optical contrast between the un-browned and browned copper surfaces underneath in subsequent steps.

[0046] Step S103: Patterning the dry film (creating the positioning target pattern)

[0047] Based on the circuit design requirements and the recognition needs of the laser drilling equipment, design the graphic file of the positioning target. The positioning target (e.g., cross-shaped, circular, etc.) is usually placed around the perimeter of the unit board, for example, 10-15mm from the edge of the board, to facilitate the equipment's gripping.

[0048] The double-sided copper-clad laminate with dry film applied is fed into a laser direct imaging (LDI) device. Before use, the alignment accuracy of the LDI device is calibrated; for example, the inner layer alignment accuracy for UV mode is required to be ≤25μm.

[0049] The LDI device reads a preset target image file and directly scans and exposes it on the dry film using a high-precision laser beam, accurately transferring the target image onto the dry film. The exposure energy is selected based on the dry film type and device characteristics. After exposure, photochemical changes occur in the area corresponding to the target (mask-covered area) and the area not corresponding to the target (non-mask area) on the dry film.

[0050] Developing. The exposed copper clad board is immersed or sprayed with a developing solution (e.g. sodium carbonate solution) to remove the un-polymerized (for negative dry film, unexposed) dry film. The developing conditions are controlled, such as developing solution concentration 0.8-1.2%, developing pressure 1.0-1.5 kg / cm 2 , developing time 50-60 seconds. After developing, the dry film in the target pattern area is retained (forming the mask covered area), while the dry film in other areas (non-mask area) is removed, exposing the underlying copper foil.

[0051] Step S104: Brown-oxidation

[0052] The pattern-developed copper clad board is subjected to brown-oxidation. Brown-oxidation is a surface treatment process in PCB manufacturing, usually used to increase the adhesion of the copper surface to the subsequent laminated media, or to change the copper surface properties in certain specific applications. In the present invention, the main purpose of brown-oxidation is to cause the copper surface in the non-mask area to chemically react and change color (usually to dark brown or black), while the copper surface under the mask covered area (i.e. the target area) remains its original bright copper color, as it is still covered by the light-colored / translucent dry film.

[0053] After brown-oxidation, a significant color difference and reflectivity difference is created between the dark (low reflectivity) copper surface in the non-mask area and the bright (high reflectivity) copper surface under the mask covered area, forming a clear feature difference. This high-contrast feature difference is extremely easy to be recognized and captured by the CCD vision alignment system of the laser drill, thus achieving high-precision targeting.

[0054] Step S105: First copper surface laser drilling

[0055] The treated copper clad board is placed on the worktable of the laser drill. The laser drill recognizes and precisely locks the targeting mark (feature difference) formed in Step S104 on the first copper surface of the copper clad board, through its vision alignment system. Based on this high-precision targeting mark, the laser drill starts laser drilling from the first copper surface, according to the pre-set drilling program, forming the first part of the X-shaped via (a series of blind holes). The drilling depth is usually controlled at about half of the board thickness.

[0056] Step S106: Protective copper foil lamination

[0057] After the laser drilling of the first copper surface is completed, a critical protection step is performed before the drilling of the second copper surface. The unit board is taken out of the laser drill and sent to a vacuum film laminator. A protective copper foil (its thickness can be selected as needed, e.g. 1 / 3 oz or 1 / 2 oz) that is large enough to cover the entire unit board or at least the drilling area is placed on the first copper surface that has completed laser drilling.

[0058] Then, start the vacuum laminator and press under the set process parameters. For example:

[0059] Vacuum stage: temperature set at 100℃, pressure set at 0.7MPa, vacuum degree drawn to <1.2hPa, holding time 50 seconds. This stage uses high temperature and vacuum environment to remove the air between the board surface and the copper foil, so that the copper foil is initially attached.

[0060] Laminating stage: temperature remains at 100℃, pressure remains at 0.7MPa, holding time 50 seconds. This stage makes the copper foil and the board surface tightly and evenly attached together through pressure.

[0061] After pressing by the vacuum laminator, the protective copper foil is firmly and evenly attached to the first copper-clad surface, including covering the hole opening of the drilled blind hole. This layer of protective copper foil will act as a sacrificial layer and a stabilizing layer when drilling the second copper-clad surface in the subsequent process.

[0062] Step S107: Laser drilling of the second copper-clad surface

[0063] The unit board with the protective copper foil attached is sent into the laser drilling machine again. At this time, the unit board is turned over so that the second copper-clad surface that has not been drilled faces upwards.

[0064] The laser drilling machine also uses its visual alignment system to recognize and accurately lock the positioning target (also formed in step S104) on the second copper-clad surface of the copper-clad plate. Based on this positioning target, laser drilling of the second copper-clad surface is carried out. The laser beam penetrates the second copper-clad surface and accurately intersects with the blind hole drilled in the first copper-clad surface inside the board, finally forming a through X-shaped via hole. In this process, since the first copper-clad surface (which is facing downwards and in contact with the equipment table at this time) is covered with a protective copper foil, even if the laser energy penetrates the board, it will be absorbed or blocked by the protective copper foil, effectively avoiding ablation of the laser drilling machine table. At the same time, since the protective copper foil is firmly attached, it also ensures that the board does not shift when subjected to laser impact, ensuring the stability of the drilling.

[0065] Step S108: Removal of the protective copper foil

[0066] After completing the double-sided laser drilling, the unit board is removed from the laser drilling machine. Manually or using automated equipment, the protective copper foil attached to the first copper-clad surface is torn off and removed.

[0067] Step S109: Removal of the remaining dry film

[0068] Depending on the subsequent process arrangement, for example, before performing electroplating hole filling, it may be necessary to remove the dry film remaining in the positioning target area (masking film covering area). This can be done through chemical stripping solution or plasma cleaning, etc. If the subsequent process allows the dry film to remain or will automatically remove it, this step can also be omitted or combined into other cleaning steps.

[0069] The present embodiment also provides a circuit board made by the drilling method described above, which comprises a substrate and a plurality of X-shaped vias formed on the substrate, the two-part blind holes constituting each X-shaped via are highly accurate in center alignment at the internal intersection point of the copper-clad plate, and the vertical deviation value is significantly reduced. By using this method, the vertical deviation value can be controlled within a more optimal range, which is much lower than that of the traditional mechanical positioning hole method (usually about ±0.039 mm). Due to the use of laser direct imaging (LDI) technology to accurately generate positioning targets during the manufacturing process, and the use of high-contrast optical differences formed by dry film and brown processing for high-precision alignment of the laser drilling machine, and the use of a vacuum film pressing and leveling machine to firmly press and cover the protective copper foil before drilling the second surface to ensure processing stability, the X-shaped via formed on the circuit board has significantly improved alignment accuracy.

[0070] The present embodiment provides a laser X-shaped via drilling method for a circuit board, which significantly improves the accuracy of the positioning reference by using laser direct imaging (LDI) technology to accurately generate positioning target patterns and combining the high-contrast feature differences formed by light-colored / transparent dry film and brown processing, thereby enabling subsequent double-sided laser drilling to achieve extremely high alignment accuracy, effectively solving the problem of large vertical deviation of X-shaped vias caused by traditional mechanical positioning methods, and ensuring reliable connection of 50 μm small aperture X-shaped vias. At the same time, before drilling the second surface, a vacuum film pressing and leveling machine is used to firmly press and cover the protective copper foil, which not only effectively protects the laser drilling machine table from ablation and prolongs the service life of the equipment, but more importantly, ensures the stability of the substrate during drilling, prevents additional errors caused by movement of the plate, and further ensures the realization of high-precision drilling.

[0071] Embodiment 2

[0072] The present embodiment provides a laser X-shaped via drilling method for a circuit board, which is used to make high-precision positioning blind holes on a copper-clad plate. The method specifically includes:

[0073] Step S201: substrate preparation

[0074] Select a copper-clad plate substrate, cut to size as needed, and perform standard surface cleaning and baking and dehumidification treatment to ensure that the substrate is clean and dry.

[0075] Step S202: dry film covering

[0076] Send the treated copper-clad plate to the film laminator. Cover a layer of light blue negative dry film on both sides. Ensure that the dry film is flat and defect-free.

[0077] Step S203: patterning dry film (making positioning target pattern)

[0078] A mask (physical mask) containing a positioning target pattern is designed. After aligning the mask with the dry film attached copper clad board, the board is sent to a conventional parallel light exposure machine for exposure. The exposure energy is determined according to the dry film characteristics and the light source intensity. After exposure, the board is developed using, for example, a sodium carbonate solution to remove the dry film in the unexposed areas, leaving the mask covered areas corresponding to the positioning target pattern, and exposing the copper surface in the other non-masked areas.

[0079] Step S204: Brown processing

[0080] The copper clad board after patterned development is subjected to brown processing. The copper surface exposed in the non-masked areas is turned dark brown, while the copper surface under the mask covered areas remains original color due to the protection of the light blue dry film. After processing, a significant color and reflectivity difference is formed between the discolored copper surface in the non-masked areas and the non-discolored copper surface under the mask covered areas, constituting the optical positioning target.

[0081] Step S205: Laser drilling

[0082] The processed copper clad board (target surface facing up) is placed on the worktable of a laser drilling machine. The laser drilling machine recognizes and locks the optical positioning target formed on the board surface through a vision system. The high-precision target is used as a reference for alignment, and then according to the preset program, the laser beam ablates the copper foil and the underlying dielectric layer to form an X-shaped via.

[0083] The laser X-shaped via drilling method for a circuit board provided by the embodiment can generate a positioning target with significant feature differences (color and / or reflectivity differences) on the surface of a copper clad board by using conventional mask exposure to pattern the dry film and combining brown processing. Even without LDI equipment, the positioning accuracy of laser drilling can be improved using the basic principles of the present application, which is a significant improvement over methods that rely on mechanical positioning holes.

[0084] To further illustrate the technical effects that can be achieved by the present application, the present method is compared with traditional methods as follows:

[0085] In laser drilling (especially when forming a through structure such as an X-shaped via that requires double-sided alignment), the final drilling position accuracy is affected by multiple independent error sources. These error sources can be roughly divided into: positioning reference manufacturing tolerances (Δ positioning hole / Δ positioning target), laser equipment alignment errors (Δ alignment), material deformation errors during processing (Δ material), and laser process errors (Δ laser). The total vertical deviation value can be approximately considered as the root sum square of these independent error sources.

[0086] In the traditional method of mechanical drilling positioning holes, the typical values of the main error sources are as follows:

[0087] Mechanical positioning hole tolerance (Delta positioning hole): ±0.03mm

[0088] Laser equipment alignment error (Delta alignment): ±0.02mm

[0089] Material deformation error (Delta material): ±0.01mm

[0090] Laser process error (Delta laser): ±0.01mm

[0091] The total vertical deviation (Delta total) of the traditional method is about:

[0092]

[0093] Delta total ≈ 0.0387mm

[0094] The total vertical deviation value of the traditional method is about ±0.039mm.

[0095] The drilling method of the laser X-shaped via of the circuit board provided by the application adopts an optical positioning target mode to replace mechanical drilling. When the method of the application is used, the typical values of each main error source are as follows:

[0096] Optical positioning target tolerance (Delta positioning target): ±0.01mm

[0097] Laser equipment alignment error (Delta alignment): ±0.02mm

[0098] Material deformation error (Delta material): ±0.01mm

[0099] Laser process error (Delta laser): ±0.01mm

[0100] Similarly, the total vertical deviation (Delta total') of the method of the application is about:

[0101]

[0102] Delta total' ≈ 0.0265mm

[0103] The total vertical deviation value of the method of the application is about ±0.026mm.

[0104] Effect comparison:

[0105] As can be seen from the comparison, the total vertical deviation (±0.026mm) of the method of the application is much smaller than the total vertical deviation (±0.039mm) of the traditional method. The percentage of precision improvement is about:

[0106]

[0107] The drilling alignment accuracy can be improved by about 33.33% by using the method. For the X-shaped via with a 50 mu m aperture (0.05 mm), the deviation (±0.039 mm) of the traditional method has accounted for 78% of the aperture, which is easy to cause poor connection; and the deviation (±0.026 mm) of the method accounts for 52% of the aperture, which greatly reduces the risk of poor hole connection, and significantly improves the conduction reliability and manufacturing yield of the X-shaped via.

[0108] The relative arrangement of components and steps, numerical expressions, and numerical values set forth in these examples are not intended to limit the scope of the application unless otherwise specifically stated. In all of the examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as a limitation. Thus, other examples of exemplary embodiments can have different values. It is noted that like numbers and letters refer to like elements throughout the several views of the drawings, and that the first definition of such elements in one figure should not be construed to limit the further discussion of such elements in another figure.

[0109] In addition, it should be noted that the use of "first", "second", and the like words of distinction are used only to facilitate identification, and unless otherwise stated, the words have no special meaning and should not be construed as limiting the scope of protection of the present application.

[0110] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for drilling laser-driven X-shaped through holes in a circuit board, characterized in that, include: Apply a dry film to the surface of the copper-clad laminate; The dry film is graphically represented to form a mask-covered area and a non-masked area corresponding to the preset positioning target position; Remove the dry film located in the non-masked area; Browning treatment causes the copper surface of the copper-clad laminate located in the non-mask area to change color. Using the feature difference between the non-mask area and the mask-covered area as a positioning target, laser drilling is performed on the copper-clad laminate based on the positioning target to form X-shaped through holes.

2. The drilling method for laser X-shaped through holes in a circuit board according to claim 1, characterized in that: The step of patterning the dry film specifically includes exposing the dry film using a laser direct imaging machine according to the pattern corresponding to the preset positioning target position.

3. The drilling method for laser X-shaped through holes in a circuit board according to claim 1 or 2, characterized in that: The dry film is a light-colored dry film or a transparent dry film.

4. The drilling method for laser X-shaped through holes in a circuit board according to claim 1, characterized in that: The characteristic differences include the color difference and / or reflectivity difference between the color-changing copper surface in the non-mask area and the uncolor-changing copper surface below the mask-covered area.

5. The drilling method for laser X-shaped through holes in a circuit board according to claim 1 or 2, characterized in that: The copper-clad laminate has a first copper-clad surface and a second copper-clad surface, and a predetermined positioning target is provided on both the first copper-clad surface and the second copper-clad surface; The step of laser drilling the copper-clad laminate based on the positioning target includes: Based on the positioning target on the first copper-clad surface, a first laser drilling is performed from the first copper-clad surface; Based on the positioning target on the second copper-clad surface, a second laser drilling is performed from the second copper-clad surface, so that the first laser drilling and the second laser drilling intersect inside the copper-clad board to form the X-shaped through hole.

6. The drilling method for laser X-shaped through holes in a circuit board according to claim 5, characterized in that: Before performing the second laser drilling from the second copper-clad surface, the positioning target based on the second copper-clad surface is further included: A protective copper foil is pressed onto the first copper-clad surface.

7. The drilling method for laser X-shaped through holes in a circuit board according to claim 6, characterized in that: After the second laser drilling is performed on the positioning target based on the second copper-clad surface, the method further includes: Remove the protective copper foil.

8. The drilling method for laser X-shaped through holes in a circuit board according to claim 6, characterized in that: The step of pressing a protective copper foil onto the first copper-clad surface specifically includes: The copper foil is pressed onto the first copper-clad surface using a vacuum lamination and leveling machine.

9. A circuit board, characterized in that, The circuit board is manufactured by the drilling method of laser X-shaped through holes of the circuit board according to any one of claims 1 to 8.

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