A processing method of intensive back-drilling and PCB board

Abstract

The application relates to the technical field of PCB (Printed Circuit Board), in particular to a processing method of intensive back drilling and a PCB. The processing method comprises the following steps: when adjacent back drilling is needed, S1, a laminated board is made, a through hole is drilled on the laminated board, a copper layer is made on the hole wall of the through hole, the thickness of the copper layer is 18-22 mu m, and a conductive hole is obtained; S2, first back drilling is performed on the conductive hole, the depth of the first back drilling is 0.2-0.3 mm less than the target depth of the back drilling, and the hole diameter of the first back drilling is 0.04-0.16 mm larger than that of the conductive hole; S3, polishing treatment is performed on the laminated board to remove burrs on the hole mouth, and then micro-etching treatment is performed to remove burrs on the board surface; S4, copper and tin electroplating treatment is performed on the board surface of the laminated board; S5, second back drilling is performed on the through hole of the laminated board, the hole diameter and position of the second back drilling are the same as those of the first back drilling; and S6, residual copper in the back drilling hole is etched by alkali, and the laminated board is subjected to tin removal treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PCB board, and particularly relates to a processing method of intensive back drilling and a PCB board. BACKGROUND

[0002] With the vigorous development and in-depth application of new technologies such as 5G, ABC and IoT, the printed circuit board suitable for high-frequency communication and phased array radar is evolving towards high density, high precision, high integration and multi-layer. High-frequency communication and radar antenna circuit boards need to meet the demand for high-integrity electronic signal transmission function, among which back drilling, a technology of drilling off the redundant column of the signal path from the back side, can improve the demand for electronic signal transmission function, and the processing flow of back drilling is shown in Figure 1 .

[0003] In order to ensure that the copper of the signal path hole is completely drilled clean, the back drilling often needs to increase the diameter of the drill bit. For intensive conductive holes, corresponding intensive back drilling holes will be made. As shown in Figure 2 , the back drilling of the large drill bit will damage the adjacent back drilling holes, which will affect the vertical precision of back drilling, and then cause the residual copper of the signal path hole, affecting the product function.

[0004] In view of the technical problem, the current industry generally uses mechanical blind hole process to produce products with an electrical signal channel of less than or equal to 0.3 mm, please refer to Figure 3 , and the processing flow is as follows:

[0005] First step: drill holes in core plate 1 and core plate 2 respectively, and metalize the hole wall by sinking / electroplating copper;

[0006] Second step: resin plug holes and grind the residual resin on the plate surface of core plate 1 and core plate 2;

[0007] Third step: make line patterns corresponding to the levels of core plate 1 and core plate 2;

[0008] Fourth step: stack the core plate 1 and core plate 2 on which the inner layer circuit is completed, prepreg and copper foil to press and make them solidify and adhere to a whole;

[0009] Fifth step: continue to drill holes, sink / electroplate copper and make outer layer circuit patterns of the circuit board.

[0010] As can be seen from the above traditional processing steps, when the mechanical blind hole processing process is used to process the PCB board with an electrical signal channel of less than or equal to 0.3 mm, each core plate needs to be drilled separately, which has the problems of long process, multiple drilling and copper sinking processes, and high cost; and after the core plate is subjected to sinking / electroplating copper and resin grinding, the substrate will be deformed in size, which will cause difficulty in alignment during pressing, and high-precision and high-integration products cannot be produced, resulting in low yield. SUMMARY

[0011] One of the purposes of the present application is to provide a processing method for intensive back-drilling holes, which can efficiently and accurately back-drill the electrical signal channels close to each other, effectively avoiding the problems of through-hole damage and through-hole channel deviation.

[0012] The second purpose of the present application is to provide a PCB.

[0013] To achieve the above-mentioned one of the purposes, the present application provides the following technical solutions.

[0014] The processing method for intensive back-drilling holes comprises the following steps when adjacent back-drilling holes need to be made:

[0015] S1, making a press plate, drilling holes on the press plate to obtain through holes, and making a copper layer on the hole wall of the through hole, wherein the thickness of the copper layer is 18-22 microns, and an electrically conductive hole is obtained;

[0016] S2, first back-drilling the electrically conductive hole, wherein the depth of the first back-drilling is 0.2-0.3 mm less than the target back-drilling depth, and the hole diameter of the first back-drilling hole is 0.04-0.16 mm larger than the hole diameter of the electrically conductive hole;

[0017] S3, polishing the press plate to remove the burrs at the hole openings, and then performing micro-etching to remove the burrs on the plate surface;

[0018] S4, electroplating copper and tin on the plate surface of the press plate;

[0019] S5, second back-drilling the through hole on the press plate, wherein the hole diameter and site of the second back-drilling are the same as those of the first back-drilling;

[0020] S6, alkaline etching the residual copper in the back-drilling hole, and tin removal treatment of the press plate.

[0021] In some embodiments, the manufacturing step of the press plate comprises:

[0022] S11, cutting the core plate, laminating the core plate into a copper-clad plate, and cutting the copper-clad plate;

[0023] S12, laminating and exposing the copper-clad plate to transfer the preset circuit pattern to the corresponding copper-clad plate, etching the copper-clad plate to make a core plate containing a circuit pattern;

[0024] S13, stacking all the core plates in corresponding order and placing a semi-cured sheet between adjacent core plates, and then pressing in a press to make a press plate containing multiple layers of circuit patterns.

[0025] In some embodiments, in S1, a copper layer is made on the hole wall by electroplating copper or copper deposition.

[0026] In some embodiments, the method of the first back drilling and / or the second back drilling comprises: using a numerical control drilling machine, and making the numerical control drilling machine drill the conductive hole according to the depth and line surface.

[0027] In some embodiments, in S2, the hole radius of the first back drilling is 0.05mm larger than the hole radius of the conductive hole.

[0028] In some embodiments, after S6, a subsequent process is included, which comprises:

[0029] S7, resin is filled into the back drilled hole, the resin is baked and cured, and then the resin overflowing the hole is ground;

[0030] S8, a copper layer is made on the hole of the press plate, and the resin in the back drilled hole is covered with copper;

[0031] S9, film pasting, exposure and development are performed on the press plate, the preset outer line pattern is copied to the surface of the press plate, and then etching is performed to complete the outer line making of the press plate;

[0032] S10, solder mask printing is performed on the surface line of the press plate.

[0033] The processing method of the dense back drilling hole has the following advantages:

[0034] The processing method of the dense back drilling hole of the application controls the back drilling hole diameter, performs the first back drilling on the conductive hole, the first back drilling only drills out 0.02-0.08mm of the thickness of the conductive hole wall, strictly reduces the back drilling range, effectively avoids the problem of deformation of the adjacent electrical signal channels, the first back drilling only drills out the hole copper of the conductive hole, the burrs on the hole after back drilling are polished and micro-etched, and the excess copper is further removed; the second back drilling is performed after tin removal, the second back drilling hole diameter is consistent with the first back drilling hole diameter and site, the second back drilling only drills out the residual copper and excess tin that are not removed by the first back drilling, and finally alkaline etching is performed to completely etch the residual copper of the back drilling hole, so that the copper is completely back drilled. Compared with the traditional method of back drilling to drill out the copper layer, the application reduces the back drilling hole diameter and combines multiple back drilling and etching, so that the back drilling hole diameter can be as small as possible under the condition of ensuring the effect of drilling out the copper layer of the conductive hole, and the problem of deformation and drilling of the conductive hole with a diameter of ≤0.3mm between adjacent electrical signal channels due to the large back drilling hole diameter is avoided. At the same time, the application does not need to drill and deposit copper on each plate layer multiple times, improves the production efficiency, reduces the cost, and avoids the problem of deformation of the plate caused by too many processes.

[0035] Also provided is a PCB plate made by the above-mentioned processing method of intensive back drilling. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a prior art back drilling process flow chart.

[0037] Figure 2 is a picture of defects in conductive holes caused by large drill back drilling.

[0038] Figure 3 is a prior art mechanical blind hole manufacturing process flow chart for manufacturing adjacent electrical signal channel distance ≤0.3mm.

[0039] Figure 4 is a schematic diagram of the processing method of intensive back drilling according to the specific embodiment of the present application.

[0040] Figure 5 is a schematic diagram of the thickness of the back drilling conductive hole wall according to the specific embodiment of the present application. DETAILED DESCRIPTION

[0041] Preferred embodiments of the present application will be described in greater detail below, with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it is understood that the present application can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0042] The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0043] It should be understood that although the terms "first", "second", "third" etc. can be employed in this application to describe various information, but these information should not be limited by these terms. These terms are only used to distinguish one piece of information from another piece of information of the same type. For example, the first information can also be called the second information, and similarly, the second information can also be called the first information without departing from the scope of the present application. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0044] EMBODIMENT

[0045] Please refer toFigures 4-5 The embodiment discloses a processing method for intensive back drilling, comprising the following steps: when adjacent back drilling needs to be made, the distance between electrical signal channels in the adjacent back drilling is ≤0.3mm,

[0046] S1, a press plate is made, a hole is drilled on the press plate to obtain a through hole, and a copper layer is made on the hole wall of the through hole, the thickness of the copper layer is 18-22μm, and a conductive hole is obtained;

[0047] The above step is mainly to make a copper layer in the hole wall of the through hole, at this time, all layers of the circuit board realize conduction, and the circuit network that does not need to be connected is included. The thickness of the copper layer in the hole wall is limited, which can effectively avoid etching the copper layer in the conductive hole at the position of the non-back drilling hole during subsequent micro-etching after back drilling, and effectively ensures the signal channel at the position of the non-back drilling hole in the conductive hole. After limiting the copper layer in the hole wall, even if the residual copper slag is removed by micro-etching, the micro-etching method will not affect the normal signal conduction of the conductive hole. If the thickness of the copper layer is not limited, the copper layer on the signal channel of the conductive hole will be etched and broken during the removal of the back drilling copper slag by micro-etching.

[0048] S2, the conductive hole is subjected to first back drilling, the depth of the first back drilling is 0.2-0.3mm less than the target depth of back drilling, and the thickness of the hole wall of the conductive hole in the radial width direction removed by the first back drilling is 0.02-0.08mm;

[0049] The above step first performs first back drilling, the depth of the first back drilling is controlled, so that the residual copper amount after the first back drilling is etched during subsequent micro-etching without etching the copper layer on the signal channel of the conductive hole, and the accuracy of back drilling is further improved.

[0050] Furthermore, the thickness of the conductive hole removed by the first back drilling is strictly controlled, wherein the hole diameter of the first back drilling is 0.04-0.16mm larger than the hole diameter of the conductive hole, and preferably 0.1mm. The control avoids the problem that the hole wall is excessively removed and the adjacent back drilling holes are drilled through. Since the range of the first back drilling is small, part of burrs will be left, which will be processed subsequently. As shown in the figure, the first back drilling a1 is performed by using a high-precision drilling machine to control the depth of drilling to re-cut the hole wall of the conductive hole a, and the required signal channel of the product is left. Figure 4

[0051] S3, the press plate is subjected to polishing treatment to remove the burrs at the hole opening, and then subjected to micro-etching treatment to remove the burrs on the plate surface;

[0052] The burrs left after the first back drilling are processed, and then micro-etched to remove the burrs on the plate surface as much as possible, and the residual copper on the plate surface does not need to be processed subsequently.​

[0053] S4, electroplating copper and tin on the surface of the laminated board, that is, adding a layer of copper and tin on the copper layer on the surface of the laminated board by electroplating;

[0054] S5, second back drilling on the through hole on the laminated board, the hole diameter and site of the second back drilling are the same as those of the first back drilling; the second back drilling is performed after the first back drilling, and the purpose of the second back drilling is to supplement the first back drilling and further remove residual copper, and the residual copper is better removed after the second back drilling.

[0055] S6, alkaline etching of residual copper in the back drilling hole, and tin removal treatment of the laminated board

[0056] The alkaline etching is performed on the back drilling hole, so as to further remove the excess residual copper in the back drilling hole, and then the tin removal treatment is performed.

[0057] In the embodiment, the manufacturing steps of the laminated board include:

[0058] S11, cutting the core board, laminating the core board into a copper-clad plate, and cutting the copper-clad plate;

[0059] S12, laminating the copper-clad plate and exposing it to light, transferring the preset circuit pattern to the corresponding copper-clad plate, etching the copper-clad plate, and manufacturing a core board containing a circuit pattern;

[0060] S13, stacking all the core boards in corresponding order and placing a prepreg between adjacent core boards, and then placing them in a press to make a laminated board containing multiple layers of circuit patterns.

[0061] In the embodiment, in S1, the copper layer is manufactured on the hole wall by electroplating copper or copper deposition.

[0062] In the embodiment, the first back drilling and / or the second back drilling method includes using a numerical control drilling machine to drill the conductive hole according to the depth and the circuit surface.

[0063] In the embodiment, after S6, subsequent processes are included, and the subsequent processes include:

[0064] S7, resin is filled into the back drilled hole, the resin is baked and cured, and then the resin overflowing from the hole is ground;

[0065] The grinding is to polish the resin overflowing from the back drilling hole and the through hole to be flat.

[0066] S8, copper layer manufacturing on the hole of the laminated board, that is, secondary copper deposition, so as to cover the resin surface in the back drilling hole with copper, and provide a corresponding copper layer for subsequent wiring on the resin surface;

[0067] S9, film pasting, exposure and development are performed on the pressboard, a preset outer layer circuit pattern is copied to the pressboard surface, then etching is performed, and outer layer circuit manufacturing of the pressboard is completed;

[0068] S10, the pressboard surface circuit is subjected to solder mask printing treatment, and then subsequent processes are performed.

[0069] The above embodiment changes the aperture difference between the back drilling hole a1 and the conductive hole a, increases the distance between the two adjacent back drills, and optimizes the processes of the first back drilling and the second back drilling, so that the copper in the circuit layer hole which does not need to be implemented to be conductive is completely drilled, and the signal crosstalk between signals is reduced.

[0070] By controlling the aperture of the back drilling hole, the conductive hole is subjected to the first back drilling, the first back drilling only drills out 0.02-0.08mm of the thickness of the conductive hole wall, by strictly reducing the back drilling range, the problem of deformation of the adjacent electric signal channel is effectively avoided, the first back drilling only drills out the first hole copper of the conductive hole, and the back drilling is followed by polishing and micro-etching of the hole mouth to remove the burrs, and further remove the excess copper; after further electroplating copper and tin, finally alkaline etching is performed to bite and etch the residual copper of the back drilling hole, and then the second back drilling is performed, the second back drilling aperture is consistent with the first back drilling aperture and site, the second back drilling drills out the residual copper and excess tin which are not removed by the first back drilling, and then the pressboard is subjected to tin removal treatment. Compared with the conventional back drilling which only drills out the copper layer, the present application can minimize the back drilling aperture while ensuring the effect of drilling out the copper layer of the conductive hole by reducing the back drilling aperture and combining multiple back drilling and etching, thereby avoiding the problem of deformation and drilling through of the conductive hole between the adjacent electric signal channels with a distance of ≤0.3mm due to the too large back drilling aperture. At the same time, the present application does not need to drill holes and deposit copper on each board layer multiple times, thereby improving the production efficiency, reducing the cost, and avoiding the problem of deformation of the board due to too many processes.

[0071] The relative arrangement, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application unless otherwise specifically stated. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in proportion to the actual proportions. The techniques, methods, and devices known to those skilled in the relevant art can not be discussed in detail, but under appropriate circumstances, the techniques, methods, and devices should be considered as part of the authorized specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0072] In the description of the application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship are generally based on the orientation or position relationship shown in the drawings, only for the convenience of describing the application and simplifying the description, without making the opposite statement, these orientation words do not indicate and imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the application; The orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0073] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial position relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0074] In addition, it should be noted that the use of "first", "second" and the like to define parts only facilitates the differentiation of corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the application.

[0075] The above only describes the preferred embodiments of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method of processing a dense back-drilling, characterized by, When adjacent back-drilling holes need to be made, the following steps are included: S1, making a press plate, the making steps of the press plate include: S11, cutting the core plate, laminating the core plate into a copper-clad plate, and cutting the copper-clad plate; S12, laminating the copper-clad plate and exposing it to make the preset circuit pattern transferred to the corresponding copper-clad plate, etching the copper-clad plate to make a core plate containing a circuit pattern; S13, stacking all the core plates in corresponding order and placing a prepreg between adjacent core plates, and then placing them in a press to make a press plate containing multiple layers of circuit patterns; Drilling holes on the press plate to obtain through holes, and making a copper layer on the hole wall of the through hole, the thickness of the copper layer being 18 μm~22 μm, to obtain a conductive hole; S2, first back-drilling the conductive hole, the depth of the first back-drilling being 0.2 mm~0.3 mm less than the target back-drilling depth, and the hole diameter of the first back-drilling hole being 0.04 mm~0.16 mm larger than the hole diameter of the conductive hole; S3, polishing the press plate to remove burrs at the hole opening, and then performing micro-etching to remove burrs on the plate surface; S4, electroplating copper and tin on the surface of the press plate; S5, second back-drilling the through hole on the press plate, the hole diameter and site of the second back-drilling being the same as those of the first back-drilling; S6, alkaline etching the residual copper in the back-drilling hole, and desmearing the press plate; S7, filling resin into the back-drilled hole, baking and curing the resin, and then grinding the resin overflowing from the hole opening; S8, making a copper layer on the hole of the press plate to cover the resin surface in the back-drilling hole; S9, laminating, exposing and developing the press plate to copy the preset outer circuit pattern to the surface of the press plate, and then etching to complete the outer circuit making of the press plate; S10, solder mask printing the circuit on the surface of the press plate.

2. The method of claim 1, wherein, In S1, the copper layer is made on the hole wall by electroplating copper or copper deposition.

3. The method of claim 2, wherein, The method of the first back-drilling and / or the second back-drilling includes using a numerical control drilling machine to drill the conductive hole according to the depth and the circuit surface.

4. The method of claim 1, wherein, In S2, the hole radius of the first back-drilling hole is 0.05 mm larger than the hole radius of the conductive hole.

5. A PCB board characterized by, The method is made by the method of claim 1~4. The method is made by the method of claim 1~4.

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