A structure for improving the burr of a soft and hard combined plate and a processing method thereof

Abstract

The application discloses a structure for improving burr of a soft and hard combined plate and a processing method thereof, and belongs to the technical field of processing and manufacturing of a PCB soft and hard combined plate. The structure comprises a hard plate base material region and a soft plate base material region which are pressed against each other, an intersection R corner is arranged at the intersection profile of the hard plate base material region and the soft plate base material region, the inside of a finished product forming profile line is an effective region of the finished product, and the outside is a waste material region which needs to be cut off after forming processing. A pre-drilling hole is arranged in the waste material region corresponding to each of the intersection R corners. The pre-drilling hole penetrates the hard plate waste material region and the soft plate waste material region at the corresponding positions. The structure overcomes the defects that long strip burrs are easily generated at the soft and hard intersection R corner during CNC contour processing of the existing soft and hard combined plate, the improvement effect of a conventional process is limited, and a new process increases production cost, and the structure eliminates the soft and hard intersection burr defects from the structural level, does not need an additional post-processing process, and greatly improves production yield.

Description

Technical Field

[0001] This invention belongs to the field of PCB rigid-flex board processing and manufacturing technology, and particularly relates to a rigid-flex board embossing improvement structure and its processing method. Background Technology

[0002] Multilayer rigid-flex PCBs are widely used in internal interconnect components of consumer electronics and automotive electronics. The manufacturing process of multilayer rigid-flex PCBs is much more complex than that of single- or double-sided rigid-flex PCBs. The multilayer rigid-flex PCB consists of flexible and rigid boards, which are bonded together through a lamination process. At the end of the manufacturing process, a CNC milling cutter is used to remove the outer waste material along the preset contour to obtain a finished board that meets the dimensional requirements.

[0003] Existing flexible boards are mainly composed of a cover film, a copper substrate, and a PI (polyimide) composite, while rigid boards are mainly composed of a copper substrate and FR4 glass fiber composite. PI flexible boards are made of continuous long polyimide fibers, exhibiting high toughness and excellent tear resistance, while FR4 rigid boards are made of glass fiber reinforced resin, exhibiting high rigidity and easily cut by cutting tools. The two substrates have vastly different mechanical properties. At the arc-shaped corner where the flexible and rigid substrates intersect, milling stress is highly concentrated. During milling, the milling cutter cannot cut the continuous long PI fibers running through both the flexible and rigid boards in one go. The fibers are torn and elongated by shearing and tension, forming long, fuzzy strands at the edges of the boards, resulting in poor appearance and potential electrical short circuits. This is a common and difficult-to-improve problem in the molding and processing of rigid-flex boards.

[0004] The existing improvement methods are divided into three categories: 1) Optimize CNC machining parameters, adjust spindle speed, feed rate, and feed direction; 2) Improve machining auxiliary materials and tools, replace with special R-angle milling cutters, and apply protective film to the board surface; 3) Add post-processing steps, use laser secondary precision cutting of soft board edges, and manually scrape off burrs.

[0005] The aforementioned existing technologies can only slightly alleviate the formation of fuzz and cannot cut off the continuous fibers across the soft-hard interface at the source; laser secondary cutting and manual trimming will increase processing time and production costs; even after mass production using parameter and tool optimization methods, the fuzz defect rate still exceeds 50%, resulting in a low product yield. Summary of the Invention

[0006] In response to the above situation and to overcome the shortcomings of the prior art, this invention provides a structure for improving the burr at the junction of rigid and flexible boards and its processing method. This invention overcomes the shortcomings of existing CNC machining of rigid and flexible boards, such as the easy generation of long burrs at the junction radius of rigid and flexible boards, the limited improvement effect of conventional process optimization, and the increase in production costs due to additional processes. This invention eliminates the burr defect at the junction of rigid and flexible boards from the structural level, requires no additional post-processing, and significantly improves the production yield.

[0007] The technical solution adopted in this invention is as follows: a soft and hard bond board burr improvement structure, which is a soft and hard bond board blank before CNC routing, including a hard board substrate area and a soft board substrate area that are pressed together. The intersection contour of the hard board substrate area and the soft board substrate area is provided with an intersection R angle. The inner side of the finished product forming contour line is the effective area of ​​the finished product, and the outer side of the finished product forming contour line is the waste area that needs to be removed after forming.

[0008] Pre-drilled holes are made in the waste area corresponding to the outer side of each of the aforementioned intersection R-angles; the pre-drilled holes simultaneously penetrate the hard board waste area and the soft board waste area at the corresponding positions.

[0009] The minimum normal distance between the outer circumference of the pre-drilled hole and the outline of the finished billet is 0.05 mm.

[0010] The diameter of the pre-drilled hole satisfies the dimensional relationship: D=2R−0.1mm, where D is the diameter of the pre-drilled hole and R is the radius of the arc of the intersection R angle.

[0011] The center of the pre-drilled hole is completely located within the waste area, with only a very small section of the outer circumference extending 0.05mm towards the effective area of ​​the finished product. After the waste is removed by CNC milling, most of the pre-drilled hole is milled away along with the waste, leaving only a small arc notch at the corner of the soft-hard junction of the finished product.

[0012] The pre-drilled holes are only provided at the intersection R-angle position where the rigid substrate area and the flexible substrate area intersect, and no pre-drilled holes are provided on the straight-line forming contour section where the rigid and flexible substrates intersect.

[0013] The present invention also provides a method for processing a rigid-flex PVC board, which improves the structure of the rigid-flex PVC board by using the above-mentioned roughening of the board, and includes the following steps:

[0014] S1. Pressing and laminating: Aligning and pressing the rigid substrate and the flexible substrate together to obtain an integrated rigid-flexible board blank;

[0015] S2. Pre-drilling: Using the finished product's forming outline as the processing reference, a CNC drilling machine drills pre-drilled holes in the scrap area outside the soft-hard junction R-angle of the blank. The minimum normal gap between the outer circumference of the pre-drilled hole and the finished product's forming outline is controlled to be 0.05mm. The pre-drilled holes with a diameter D=2R−0.1mm are matched according to the junction R-angle radius R. The pre-drilled holes simultaneously drill through the corresponding hard board substrate scrap area and soft board substrate scrap area.

[0016] S3, CNC milling: The milling cutter is used to mill and remove the waste material around the blank along the finished product outline. Most of the holes in the pre-drilled holes located in the waste area are milled off along with the waste material. The milling path at the intersection of the pre-drilled holes and the R-angle is divided. The milling cutter cuts the side outline of the hard board substrate and the side outline of the soft board substrate in segments to avoid continuous cutting of the tool across two materials.

[0017] In step S3, during the milling process, the pre-drilled hole serves as a stress relief notch to disperse the concentrated shear stress at the hard-soft interface. Furthermore, the pre-drilled hole pre-cuts the continuous fibers of the substrate that extend across the hard and soft substrates, thus suppressing the generation of long fuzzy fibers during cutting and pulling.

[0018] The beneficial effects of the present invention after adopting the above structure are as follows:

[0019] (1) Before forming and processing, the present invention sets a pre-drilled hole across the soft and hard substrate in the waste area outside the R-angle. The drilling process directly cuts the continuous fiber of the substrate that extends through the hard and soft substrates, dividing the complete through fiber into two independent short fibers. There are no long fibers available for the tool to pull and tear during subsequent milling, thus completely eliminating the generation of long fuzz.

[0020] (2) The R-angle at the junction of soft and hard is the point of stress concentration during milling. The pre-drilled circular hole structure can disperse the cutting shear stress, avoid stress concentration pulling the soft board substrate, and reduce substrate tearing and stringing defects.

[0021] (3) Pre-drilling divides the continuous forming contour at the R-corner into two independent cutting paths for hard board and soft board substrate. The milling cutter does not need to cut across two substrates with huge mechanical differences, such as hard board substrate and soft board substrate, so the cutting force is uniform and the flatness of the edge surface is significantly improved.

[0022] (4) The center of the pre-drilled hole is located in the area of ​​the waste material to be removed, and only the 0.05mm arc edge is close to the finished product outline; when the milling is performed, most of the holes are removed with the waste material, and only a small arc notch is left in the finished product. It will not occupy or damage the effective circuit area of ​​the finished product, and will not change the electrical and structural performance of the product.

[0023] (5) Pre-drilling is only processed in the same way as the original drilling process. There is no need to add extra processes such as laser cutting, manual trimming, and protective film bonding. There are no new steps in the production process and the cost of board making is not increased.

[0024] (6) After adopting the pre-drilled structure blank of the present invention, the poor quality of soft and hard junction fuzz is basically eliminated, the yield of mass production is greatly improved, and the improvement range far exceeds the limit of conventional process optimization methods in the industry, which has outstanding progressiveness. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0026] Figure 1 This is a schematic diagram of the CNC milling tool path and tool entry position for existing rigid-flex PCBs.

[0027] Figure 2 A schematic diagram of the CNC milling process for the rigid-soft bonding plate after pre-drilling is provided in this invention;

[0028] Figure 3 This is a schematic diagram of a blank structure with pre-drilled holes before processing, which is a method for improving the structure of a flexible and rigid bonded plate with improved burr texture.

[0029] Figure 4 This is a schematic diagram of the structure after processing of the flexible and rigid combined plate with improved burr structure proposed in this invention;

[0030] Figure 5 This is a comparison chart showing the edge fuzz defects and yield of finished products processed by existing technologies and the present invention.

[0031] In the attached diagram: 1. Rigid substrate area, 2. Flexible substrate area, 3. Intersection radius, 4. Effective area, 5. Waste area, 6. Pre-drilled hole. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] like Figures 1-5As shown, a structure for improving the burrs on a rigid-soft bonded board is a rigid-soft bonded board blank before CNC machining. It includes a rigid board substrate area 1 and a soft board substrate area 2 that are pressed together. The intersection of the rigid board substrate area 1 and the soft board substrate area 2 is provided with an intersection R angle 3. The inner side of the finished product forming outline is the effective area of ​​the finished product 4, and the outer side of the finished product forming outline is the waste area 5 that needs to be removed after forming.

[0035] A pre-drilled hole 6 is opened in the waste area 5 corresponding to the outer side of each of the intersection R angles 3; the pre-drilled hole 6 simultaneously penetrates the corresponding hard board waste area 5 and soft board waste area 5; the minimum normal distance between the outer circumference of the pre-drilled hole 6 and the forming outline of the finished blank is 0.05mm; the diameter of the pre-drilled hole 6 satisfies the dimensional relationship: D=2R−0.1mm, where D is the diameter of the pre-drilled hole 6 and R is the radius of the arc of the intersection R angle 3.

[0036] The center of the pre-drilled hole 6 is completely located within the waste area 5, with only a very small section of the outer circumference extending 0.05mm towards the effective area 4 of the finished product. After the waste is removed by CNC milling, most of the hole body of the pre-drilled hole 6 is milled away along with the waste, leaving only a small arc notch at the corner of the soft-hard junction R angle 3 of the finished product.

[0037] The pre-drilled hole 6 is only provided at the intersection R-angle 3 where the rigid substrate area 1 and the flexible substrate area 2 intersect, and the pre-drilled hole 6 is not provided on the straight forming contour section where the rigid and flexible substrates intersect.

[0038] The present invention also provides a method for processing a rigid-flex PVC board, which improves the structure of the rigid-flex PVC board by using the above-mentioned roughening of the board, and includes the following steps:

[0039] S1. Pressing and laminating: Aligning and pressing the rigid substrate and the flexible substrate together to obtain an integrated rigid-flexible board blank;

[0040] S2. Pre-drilling hole 6 processing: Using the finished product forming outline as the processing reference, the CNC drilling equipment drills pre-drilled holes 6 in the waste area outside the soft-hard junction R angle 3 of the blank. The minimum normal gap between the outer circumference of the pre-drilled hole 6 and the finished product forming outline is controlled to be 0.05mm. The pre-drilled hole 6 with a processing diameter D=2R−0.1mm is matched according to the radius R of the junction R angle 3. The pre-drilled hole 6 simultaneously drills through the corresponding hard board substrate waste area 5 and soft board substrate waste area 5.

[0041] S3, CNC milling: The milling cutter is used to mill along the finished product outline to remove the waste material around the blank. Most of the holes in the pre-drilled hole 6 located in the waste area are milled off along with the waste material. The milling path at the intersection R angle 3 of the pre-drilled hole 6 is divided. The milling cutter cuts the side contour of the hard board substrate and the side contour of the soft board substrate in segments to avoid continuous cutting of the tool across two materials.

[0042] In step S3, during the milling process, the pre-drilled hole 6 serves as a stress relief notch to disperse the concentrated shear stress at the hard-soft interface. Furthermore, the pre-drilled hole 6 cuts off the continuous fibers of the substrate that extend across the hard and soft substrates in advance, thus suppressing the generation of long fuzzy fibers during cutting and pulling.

[0043] The specific usage is as follows:

[0044] The rigid substrate area and the flexible substrate area 2 are pressed together before CNC milling. The radius of the arc at the intersection of the two is R=0.3mm.

[0045] A pre-drilled hole 6 is set in the waste area 5 outside the intersection R-angle 3. According to the dimensional relationship D=2R−0.1mm, the diameter of the pre-drilled hole 6 is D=0.5mm. The center of the pre-drilled hole 6 is located in the waste area 5. The minimum normal gap between the outer circumference of the pre-drilled hole 6 and the finished product forming outline is controlled to be 0.05mm. The pre-drilled hole 6 simultaneously drills through the corresponding hard substrate waste section and soft board substrate waste section. The pre-drilled hole 6 is only set at the R-angle position. The straight forming outline section where the hard substrate and soft board substrate intersect is not set with a pre-drilled hole 6.

[0046] Supporting processing steps:

[0047] S1. Align and stack the rigid substrate and the flexible substrate, and press them together at high temperature to obtain an integrated blank;

[0048] S2, CNC drilling process, using the finished product outline as the machining reference, pre-drill holes with a diameter of 0.5mm in the waste area outside the soft and hard junction R angle 3;

[0049] S3, CNC milling of the outer contour: the milling cutter cuts the outer waste along the finished product's forming contour line, and the pre-drilled holes are mostly peeled off with the waste; the milling cutter cuts the contour of the hard substrate side and the soft substrate side in sections to avoid continuous cutting across materials; after forming, only a small arc notch is left at the R-corner edge of the finished product.

[0050] Batch verification data: Of the 1000 boards in the same batch, only 5 were defective with fuzzy fibers, resulting in a production yield of 99.48%. There were no long fiber fuzzy fibers at the junction of soft and hard surfaces.

[0051] Using the same rigid substrate and flexible substrate as above, with the same pressing parameters and the same CNC milling plate speed and feed parameters, the blank was not pre-drilled with holes 6. The burrs were only improved by optimizing the tool path and replacing the wear-resistant milling cutter. In the same batch of 1000 sheets, 560 sheets had burr defects, and the production yield was only 44%. Long fiber burrs appeared in large quantities at the R-angle 3 where the soft and hard materials meet.

[0052] The above are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention; any technical solutions obtained by equivalent substitution or simple transformation of the pre-drilling size and processing parameters based on the core concept of the present invention shall fall within the scope of protection of the present invention.

[0053] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. In conclusion, if those skilled in the art, inspired by this description, design similar structural methods and embodiments without departing from the inventive spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A structure for improving the burrs on a rigid-soft bonded board, which is a rigid-soft bonded board blank before CNC milling, including a rigid board substrate area and a soft board substrate area that are pressed together. The intersection contour of the rigid board substrate area and the soft board substrate area is provided with an intersection R angle. The inner side of the finished product forming contour line is the effective area of ​​the finished product, and the outer side of the finished product forming contour line is the waste area that needs to be removed after forming. Its features are, Process pre-drilling holes are opened in the waste area corresponding to the outer side of each of the aforementioned intersection R-angles; the process pre-drilling holes simultaneously penetrate the corresponding hard board substrate waste area and soft board substrate waste area.

2. The soft-hard bonded plate burr improvement structure according to claim 1, characterized in that, The minimum normal distance between the outer circumference of the pre-drilled hole and the finished billet contour line is 0.05 mm.

3. The soft-hard bonded plate burr improvement structure according to claim 1, characterized in that, The diameter of the pre-drilled hole in the process satisfies the dimensional relationship: D=2R−0.1mm, where D is the diameter of the pre-drilled hole and R is the radius of the arc of the intersection R angle.

4. A method for processing rigid-flex PVC board, characterized in that, The processing of the improved structure using the soft-hard bonded plate and burr as described in any one of claims 1-3 includes the following steps: S1. Pressing and laminating: Aligning and pressing the rigid substrate and the flexible substrate together to obtain an integrated rigid-flexible board blank; S2. Pre-drilling: Using the finished product outline as the processing reference, the CNC drilling equipment drills process pre-drilling holes in the waste area outside the R-angle where the hard and soft materials meet. The process pre-drilling holes simultaneously drill through the corresponding hard board substrate waste area and soft board substrate waste area. S3, CNC milling shape forming: The milling cutter is used to mill along the finished product forming outline to remove the waste material around the blank; pre-drilling holes divides the milling path at the intersection R-angle, and the milling cutter cuts the side outline of the hard board substrate and the side outline of the soft board substrate in segments.

5. The method for processing rigid-flex PCBs according to claim 4, characterized in that, In step S3, during the milling process, the pre-drilled hole serves as a stress relief notch to disperse the concentrated shear stress at the hard-soft interface, and the pre-drilled hole also cuts off the continuous fibers of the substrate that extend across the hard and soft substrates in advance.

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