A drilling process for rigid-flex printed circuit boards

Abstract

The application discloses a drilling process of rigid-flex printed circuit board, comprising the following steps: board surface detection: detecting the board surface of the laminated rigid-flex printed circuit board, identifying and determining the uneven area of the board surface; filling treatment: filling the recessed part in the uneven area, and making the board surface tend to be flat after the filling material is solidified; setting the drilling alignment mark on the board surface after the filling treatment; drilling processing: drilling according to the drilling alignment mark. The recessed area is filled and treated, the height difference of the board surface is eliminated, the drill bit is uniformly stressed when contacting the board surface, the drill bit deflection is effectively prevented, and the hole deviation defects are reduced. The flat board surface makes the drill bit stably stressed when passing through different areas, and the hole wall roughness, burr or nail head phenomenon caused by the stress mutation is avoided.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a drilling process for rigid-flex boards. Background Technology

[0002] A rigid-flex PCB is a type of circuit board that combines a rigid circuit board and a flexible circuit board through a lamination process. It combines the flexibility and three-dimensional wiring characteristics of a flexible board with the component load-bearing capacity and mechanical stability of a rigid board. It can break through the limitations of traditional planar design and realize three-dimensional assembly, so it is widely used in aerospace, medical electronics, consumer electronics and other fields with stringent requirements for space and weight.

[0003] As electronic products evolve towards miniaturization, high density, and high reliability, the design of rigid-flex PCBs is becoming increasingly sophisticated and complex. In some complex structural designs, to meet specific three-dimensional assembly requirements, the inner flexible layers are no longer confined to the same planar area but are instead designed in a branched or staggered manner. This design results in uneven distribution of the flexible layers in the lamination area. In addition, the circuit density and thickness of each layer may differ, causing significant thickness differences to form on the surface of the board in different areas after multilayer lamination, resulting in an uneven surface.

[0004] Drilling is a crucial step in the manufacturing of rigid-flex PCBs to achieve interlayer electrical interconnection. The unevenness of the PCB surface presents a significant challenge to subsequent drilling operations. Specifically, existing technologies suffer from the following main problems: First, unevenness on the board surface causes uneven force on the drill bit upon contact with the surface, easily leading to skewness and causing the drilled hole to deviate from the design center, resulting in off-center drilling. Second, when drilling through areas of different thicknesses (such as transitioning from a rigid to a flexible area, or from a filled to an unfilled area), the stress state of the drill bit changes drastically, easily causing rough hole walls, burrs, or spikes, and in severe cases, even drill bit breakage. Finally, traditional positioning methods based on the board edge or individual through holes are difficult to guarantee precise alignment of all holes across the entire board when dealing with board surfaces deformed by local unevenness, further increasing the difficulty of controlling drilling accuracy. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a drilling process for rigid-flexible composite plates, which can avoid the problem of uneven force on the drill bit at the moment of contact with the plate surface during drilling, thereby improving drilling quality and stability.

[0006] A drilling process for a rigid-flexible laminate according to an embodiment of the present invention includes the following steps: Surface inspection: The laminated rigid-flexible laminate is inspected to identify and determine uneven areas on the surface; Filling treatment: A filler material is applied to the surface to cover the raised and recessed areas, and the filler material is cured to thicken the surface and make it flat; Marking: Drilling alignment marks are set on the filled surface; Drilling: Drilling is performed according to the drilling alignment marks.

[0007] It has at least the following beneficial effects: By filling the recessed areas, the height difference of the board surface is eliminated, ensuring uniform force on the drill bit when it contacts the board surface, effectively preventing drill bit deviation and reducing off-center hole defects. The flat board surface ensures stable force on the drill bit when it passes through different areas, avoiding rough hole walls, burrs, or nail-like phenomena caused by sudden changes in force, improving hole wall smoothness and electrical connection reliability; furthermore, setting drill hole alignment marks on the filled and flattened board surface provides a precise positioning benchmark for the drilling equipment, overcoming the problem of traditional positioning methods failing due to board surface deformation, and ensuring the consistency of drilling positions across the entire board; by improving drilling accuracy and quality, the scrap rate caused by off-center holes and broken drills is reduced, increasing the first-pass yield of products, thereby reducing overall manufacturing costs.

[0008] According to some embodiments of the present invention, in the filling process, a filling material is first applied or injected to the recessed area of ​​the board surface so that the upper surface of the filling material is flush with or slightly higher than the reference surface of the board surface. Then, the filling material is cured. The surface of the cured filling material is ground flat to make it consistent with the surrounding board surface.

[0009] According to some embodiments of the present invention, in the filling process step, the filler material is a resin-based filler, including one or more of epoxy resin, acrylic resin or polyimide resin.

[0010] According to some embodiments of the present invention, in the filling process step, a photosensitive wet film is printed on the board surface to fill the uneven areas of the board surface.

[0011] According to some embodiments of the present invention, in the filling process, while printing a photosensitive wet film on the board surface, the wet film opens a window at the corresponding position of the drilled hole, and the window size is 1 mil larger than one side of the hole.

[0012] According to some embodiments of the present invention, in the step of setting the marking, the drilling alignment marking includes optical identification marks and / or mechanical positioning holes. The optical identification marks are set at the corners, edges or bifurcation points of the flexible layer on the board surface, and the mechanical positioning holes are set in the non-functional areas of the board surface.

[0013] According to some embodiments of the present invention, in the drilling process, the drilling path and drilling position are determined according to the drilling alignment mark, and the drilling parameters of the filled area and the unfilled area are set according to the material properties of the filled area, and then the drilling process is performed according to the set drilling parameters.

[0014] According to some embodiments of the present invention, in the drilling process, the drilling parameters include one or more of the following: drill bit rotation speed, feed rate, retraction speed, and drill bit life, wherein the drill bit rotation speed in the filling region is lower than that in the non-filling region, and the feed rate in the filling region is lower than that in the non-filling region.

[0015] According to some embodiments of the present invention, after the drilling process is completed, a detection step is also included. The detection step includes: first detecting the hole position accuracy, hole wall quality and hole diameter, and then feeding the detection results back to the filling process and / or the drilling process to optimize the filling scheme and drilling parameters.

[0016] According to some embodiments of the present invention, in the filling process step, the filling material used is a removable filling material that is removed by dissolving or heating after drilling is completed.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0019] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] In the description of this invention, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0022] Reference Figure 1 This invention discloses a drilling process for a rigid-flexible plate, comprising the following steps: Surface inspection: The surface of the laminated rigid-flexible board is inspected to identify and determine the uneven areas on the board surface; Filling treatment: Apply filler material to the board surface to cover the raised and recessed areas, and then cure the filler material to thicken the board surface and make it flat. Marking: Mark the drill hole alignment on the board surface after filling treatment; Drilling: Drilling is performed according to the drill alignment marks.

[0023] Understandably, filling the recessed areas eliminates height differences on the board surface, ensuring uniform force on the drill bit when it contacts the board, effectively preventing drill bit deviation and reducing off-center hole defects. A flat board surface ensures stable force on the drill bit as it traverses different areas, avoiding rough hole walls, burrs, or studs caused by sudden force changes, thus improving hole wall smoothness and electrical connection reliability. Furthermore, setting drill alignment marks on the filled and flattened board surface provides a precise positioning reference for the drilling equipment, overcoming the failure of traditional positioning methods due to board surface deformation, and ensuring consistent drilling positions across the entire board. By improving drilling accuracy and quality, reducing scrap rates due to off-center holes and drill breakage, increasing the first-pass yield, and ultimately lowering overall manufacturing costs.

[0024] Furthermore, in the filling process, a filler material is first applied or injected to the recessed areas of the board surface, so that the upper surface of the filler material is flush with or slightly higher than the reference surface of the board surface. Then, the filler material is cured. The surface of the cured filler material is ground flat to make it consistent with the surrounding board surface.

[0025] Understandably, by making the upper surface of the filler material flush with or slightly higher than the reference surface of the board, and then grinding it flat after curing, it is possible to ensure that the height of the filler area is consistent with the surrounding board surface, eliminate local unevenness, provide a uniform and flat processing surface for drilling, avoid uneven drill bit force and hole position displacement caused by the height difference of the board surface, and further improve drilling quality.

[0026] Furthermore, in the filling process, the filler material is a resin-based filler, including one or more of epoxy resin, acrylic resin, or polyimide resin.

[0027] It is understandable that resin-based fillers such as epoxy resin, acrylic resin, or polyimide resin are selected. These materials have good flowability, filling properties, and adhesion to the substrate. After curing, they have moderate hardness, which facilitates grinding and provides stable support during drilling, preventing the filler material from falling off or deforming during the drilling process, thereby ensuring the stability of the drill hole and the quality of the hole wall.

[0028] In another embodiment of the present invention, in the filling process step, a photosensitive wet film is printed on the board surface to fill the uneven areas of the board surface.

[0029] Understandably, photosensitive wet film is a commonly used material in printed circuit board (PCB) manufacturing. It requires no special equipment or additional materials and can be implemented directly on existing production lines, reducing process modification costs and operational difficulties. Photosensitive wet film has excellent flowability and coatability, allowing it to evenly cover the board surface via screen printing or coating. It automatically flows into and fills recessed areas, avoiding localized accumulation or insufficient filling, ensuring overall board flatness. The photosensitive wet film itself has photosensitive properties; while filling and flattening, it can directly serve as a photosensitive layer for subsequent imaging processes, facilitating the creation of drill alignment marks or other graphic transfer steps, simplifying the process flow. Photosensitive wet film allows for precise control of thickness and coverage, making it suitable for complex rigid-flex boards with high circuit density and small uneven areas, meeting the stringent flatness requirements of high-precision drilling.

[0030] Furthermore, in the filling process, while printing a photosensitive wet film on the board surface, the wet film makes a window at the corresponding position of the drilled hole, and the window size is 1 mil larger than one side of the hole.

[0031] Understandably, by pre-opening windows at the drilling location, the substrate is directly exposed in the drilling area. During drilling, the drill bit does not need to penetrate the wet film layer, avoiding problems such as poor chip removal, hole wall scratches, or drill bit overheating caused by wet film debris entanglement in the drill bit. This improves drilling quality and drill bit life. The window size is limited to 1 mil larger than one side of the hole. This precise dimension ensures that the drill bit operates entirely within the window area during drilling, preventing it from deviating and hitting the wet film. It also prevents the window from being too large, thus avoiding the loss of the wet film's support around the drill bit, achieving a balance between accuracy and stability. After drilling is completed, it is very easy to visually check whether the drill hole is misaligned. If the drill hole aligns with the window position of the photosensitive wet film, it indicates that the hole is not misaligned; otherwise, it indicates that the hole position is misaligned, requiring adjustment of the drilling data to avoid batch scrapping.

[0032] Furthermore, in the marking step, the drilling alignment markings include optical identification marks and / or mechanical positioning holes. The optical identification marks are set at the corners, edges, or bifurcation points of the flexible layer on the board surface, and the mechanical positioning holes are set in the non-functional areas of the board surface.

[0033] Understandably, by setting multiple types of alignment marks at key locations, multiple positioning references can be provided for drilling equipment, improving positioning accuracy and reliability. Placing the marks in non-functional areas or edge positions avoids damage to the effective wiring area of ​​the board, balancing accuracy and product integrity.

[0034] Furthermore, in the drilling process, the drilling path and drilling position are determined according to the drilling alignment mark, and the drilling parameters for the filled area and the unfilled area are set according to the material properties of the filled area. Then, the drilling process is carried out according to the set drilling parameters.

[0035] Understandably, due to the differences in material properties (such as hardness and thermal conductivity) between filled and unfilled areas, using uniform drilling parameters can easily lead to uneven drill bit wear or decreased hole wall quality. This solution uses zoned parameter settings to make the drilling process more adaptable to the material properties of different areas, thereby improving drilling consistency and extending drill bit life.

[0036] Furthermore, in the drilling process, the drilling parameters include one or more of the following: drill speed, feed rate, retraction speed, and drill life, wherein the drill speed in the filling area is lower than that in the non-filling area, and the feed rate in the filling area is lower than that in the non-filling area.

[0037] Understandably, the drill bit rotation speed and feed rate are lower in the filled area than in the unfilled area. The filler material is usually harder or tougher, so using a lower rotation speed and feed rate can reduce the cutting load on the drill bit, reducing the risk of drill bit wear and breakage; at the same time, it avoids the filler material chipping or hole wall roughness caused by excessive cutting speed, thereby improving hole wall smoothness and hole diameter accuracy.

[0038] Furthermore, after the drilling process is completed, an inspection step is also included. The inspection step includes: first, inspecting the hole position accuracy, hole wall quality and hole diameter, and then feeding the inspection results back to the filling process and / or drilling process to optimize the filling scheme and drilling parameters.

[0039] Understandably, by establishing a closed-loop feedback mechanism, process deviations can be detected in a timely manner, and filling schemes and drilling parameters can be optimized to achieve continuous process improvement, gradually improve overall processing quality, and reduce scrap rates in mass production.

[0040] It is worth noting that, in the embodiments of the present invention, the drilling process is performed by mechanical drilling or laser drilling.

[0041] Mechanical drilling is suitable for conventional hole diameters and mass production, and is relatively inexpensive; laser drilling is suitable for small hole diameters and high precision requirements, and can avoid damage to the filled area caused by mechanical stress. This solution provides multiple alternative drilling methods, allowing the production process to be flexibly adjusted according to product requirements and equipment conditions, thus expanding the scope of application of this invention.

[0042] Furthermore, in the filling process, the filler material used is a removable filler material, which is removed by dissolving or heating after drilling is completed.

[0043] Removable filler material can meet the flatness requirements before drilling and can be completely removed after drilling, avoiding the impact of filler material residue on subsequent processes (such as electroplating and surface treatment). It is particularly suitable for high-end rigid-flex PCB products with high cleanliness requirements, improving process adaptability and product reliability.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A drilling process for a rigid-flexible composite plate, characterized in that, Includes the following steps: Surface inspection: The surface of the laminated rigid-flexible board is inspected to identify and determine the uneven areas on the board surface; Filling treatment: Apply filler material to the board surface to cover the raised and recessed areas, and then cure the filler material to thicken the board surface and make it flat. Marking: Mark the drill hole alignment on the board surface after filling treatment; Drilling: Drilling is performed according to the drill alignment marks.

2. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, In the filling process, filler material is first applied or injected into the recessed areas of the board surface so that the upper surface of the filler material is flush with or slightly higher than the reference surface of the board surface. Then the filler material is cured. The surface of the cured filler material is ground smooth to ensure it is consistent with the surrounding board surface.

3. The drilling process for a rigid-flexible plate according to claim 2, characterized in that, In the filling process, the filler material is a resin-based filler, including one or more of epoxy resin, acrylic resin, or polyimide resin.

4. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, In the filling process, a photosensitive wet film is printed on the board surface to fill in any uneven areas.

5. The drilling process for a rigid-flexible plate according to claim 4, characterized in that, During the filling process, while printing a photosensitive wet film onto the board surface, the wet film makes a window at the corresponding position of the drilled hole, and the window size is 1 mil larger than one side of the hole.

6. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, In the marking step, the drilling alignment markings include optical identification marks and / or mechanical positioning holes. The optical identification marks are set at the corners, edges, or bifurcation points of the flexible layer on the board surface, and the mechanical positioning holes are set in the non-functional areas of the board surface.

7. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, In the drilling process, the drilling path and position are determined according to the drilling alignment mark, and the drilling parameters for the filled area and the unfilled area are set according to the material properties of the filled area. Then, the drilling process is carried out according to the set drilling parameters.

8. The drilling process for a rigid-flexible plate according to claim 7, characterized in that, In the drilling process, drilling parameters include one or more of the following: drill speed, feed rate, retraction speed, and drill life. The drill speed in the filled area is lower than that in the unfilled area, and the feed rate in the filled area is lower than that in the unfilled area.

9. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, After the drilling process is completed, there is also an inspection step, which includes: first, inspecting the hole position accuracy, hole wall quality and hole diameter, and then feeding the inspection results back to the filling process and / or drilling process to optimize the filling scheme and drilling parameters.

10. The drilling process for a rigid-flexible plate according to claim 1, characterized in that, In the filling process, the filler material used is a removable filler material, which is removed by dissolving or heating after drilling is completed.

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