A method for manufacturing a circuit board and a circuit board

Abstract

The application discloses a manufacturing method of a circuit board and the circuit board. The manufacturing method of the circuit board comprises the following steps: providing a multilayer board to be processed, wherein the multilayer board comprises a metallized blind groove, a protective layer is formed on the surface of the metallized blind groove, at least part of the area of the back surface of the multilayer board provided with the metallized blind groove is covered with a dry film, and the area covered with the dry film is not formed with the protective layer. Back drilling is performed from the bottom of the metallized blind groove at the position where a non-metallized hole is pre-formed at the bottom of the metallized blind groove, and the protective layer and the copper layer covered by the protective layer at the position where the non-metallized hole is pre-formed at the bottom of the metallized blind groove are drilled away. Secondary drilling is performed from the back surface of the multilayer board provided with the metallized blind groove to the position communicated with the back drilling position, and the diameter of the secondary drilling is smaller than that of the back drilling. The dry film and the protective layer are removed to form the non-metallized hole. The metallized blind groove of the printed circuit board manufactured by the technical scheme of the application comprises a non-metallized hole ring of the upper hole and the lower hole which are non-metallized holes.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, and more particularly to a method for manufacturing a circuit board and the circuit board itself. Background Technology

[0002] Currently, the market is constantly increasing its requirements for miniaturization, high density, and high reliability of electronic devices. Customers are also raising higher standards for the functional diversity of printed circuit board products. There is an increasing demand for printed circuit board products with special structural designs. For example, there is a structural design that sets non-metallized holes without metal rings in metallized blind slots. The design requires that the hole rings at the upper and lower holes be non-metallized hole rings to meet the dual requirements of mounting and fixing conductive devices and electrical insulation.

[0003] In existing technologies, secondary drilling is typically performed on the back side of the metallized blind groove to form a non-metallized hole. However, this technical solution cannot achieve a non-metallized hole where both the upper and lower hole openings have non-metallized hole rings. Summary of the Invention

[0004] This invention provides a method for manufacturing a circuit board and a circuit board for preparing a circuit board with non-metallized holes in a metallized blind slot, including hole rings at the upper and lower openings that are non-metallized hole rings.

[0005] According to one aspect of the present invention, a method for manufacturing a circuit board is provided, comprising: A multilayer board to be processed is provided; wherein the multilayer board includes a metallized blind groove, a protective layer is formed on the surface of the multilayer board and the bottom of the metallized blind groove, at least a portion of the back side of the multilayer board where the metallized blind groove is provided is covered with a dry film, and the area covered with the dry film is not covered with a protective layer. At the location where a non-metallized hole is pre-formed at the bottom of the metallized blind trench, back drilling is performed from the bottom of the metallized blind trench to remove the protective layer and the copper layer covered by the protective layer at the location where the non-metallized hole is pre-formed at the bottom of the metallized blind trench. A secondary drilling is performed on the back side of the multilayer board where the metallized blind groove is provided, until it connects with the back drilling position; the diameter of the secondary drilling hole is smaller than the diameter of the back drilling hole; Remove the dry film and protective layer to form a non-metallized hole; the hole rings at the upper and lower openings of the non-metallized hole are non-metallized hole rings.

[0006] Optionally, a metallized hole is provided in the metallized blind groove, and a protective layer is formed on the surface of the metallized blind groove and the metallized hole.

[0007] Optionally, back drilling from the bottom of the metallized blind groove at the location where a non-metallized hole is pre-formed at the bottom of the metallized blind groove includes: A rigid cover plate is placed on the first surface of the multilayer board, and the drill bit is controlled to start drilling from the surface of the rigid cover plate. When the drill bit descends to the bottom of the metallized blind groove, the initial back-drilling position of the drill bit is obtained, and back-drilling is performed based on the initial back-drilling position.

[0008] Optional, the rigid cover plate includes a smooth core plate or a drilled pad plate.

[0009] Optionally, the rigid cover plate includes a non-conductive region and a conductive region, with the conductive region surrounding the non-conductive region; The non-conductive area includes the drill bit's lowering position; The conductive area is provided with a first conductive layer, which is in contact with the protective layer of the multilayer board. The material of the protective layer includes tin.

[0010] Optionally, the drill bit tip angle is greater than 165°.

[0011] Optionally, when the drill bit descends to contact the bottom of the metallized blind groove, the initial back-drilling position of the drill bit is obtained, and back-drilling is performed based on the initial back-drilling position, including: The drill rig conductive contact is brought into contact with the first surface of the multilayer board, and the drill rig conductive contact is connected to the drill rig spindle; When the tip of the drill bit contacts the bottom of the metallized blind groove, the drill spindle receives an electrical signal based on the drill bit; The initial back-drilling position of the drill bit is determined based on the electrical signal; The back drill depth is set according to the thickness of the protective layer at the position of the pre-formed non-metallized hole at the bottom of the metallized blind slot, the thickness of the copper layer covered by the protective layer, and the compensation parameters. Back drilling is performed based on the initial position of the back drill and the drilling depth of the back drill.

[0012] Optionally, removing the dry film and protective layer to form non-metallized pores includes: Remove the dry film, remove the copper in the dry film-covered area using a chemical etching process, and remove the protective layer.

[0013] Optionally, forming the multilayer board to be processed includes: A dry film is applied to the first surface of the multilayer board and the back surface of the multilayer board where metallized blind grooves are provided, and the dry film is exposed and developed. Pattern electroplating is performed on multilayer boards to form the multilayer boards to be processed.

[0014] According to another aspect of the present invention, a circuit board is provided, which can be manufactured by the manufacturing method of any embodiment of the present invention.

[0015] The technical solution of this invention involves back-drilling from the bottom of the metallized blind slot at the location where a non-metallized hole is pre-formed. This back-drills the protective layer and the copper layer covering it at the pre-formed non-metallized hole location, removing at least the copper layer at the upper opening and the hole ring of the pre-formed non-metallized hole. A secondary drilling is then performed from the back side of the multilayer board where the metallized blind slot is located, connecting to the back-drilled location. The diameter of the secondary drilling hole is smaller than the diameter of the back-drilled hole. The dry film and protective layer are removed to form the non-metallized hole. After removing the dry film, the copper layer at the hole ring at the lower opening of the non-metallized hole can be removed by etching, thus making the hole rings at the upper and lower openings of the non-metallized hole non-metallized. In summary, the technical solution of this invention enables non-metallized holes in the metallized blind slots of the circuit board, including the hole rings at the upper and lower openings, to be non-metallized, fulfilling the requirements for mounting plug-in components and electrical isolation.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A top view of a circuit board provided for related technologies; Figure 2 A top view of another circuit board provided for related technologies; Figure 3 A cross-sectional view of a circuit board provided for related technologies; Figure 4 A schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, provided for related technologies; Figure 5 A schematic cross-sectional view of a multilayer board during another circuit board manufacturing process provided for related technologies; Figure 6 A schematic cross-sectional view of a multilayer board in another circuit board manufacturing process provided for related technologies; Figure 7 A schematic cross-sectional view of a multilayer board in another circuit board manufacturing process provided for related technologies; Figure 8 A schematic cross-sectional view of a multilayer board in another circuit board manufacturing process provided for related technologies; Figure 9 A schematic cross-sectional view of a circuit board formed by a circuit board manufacturing method using related technologies; Figure 10 A flowchart illustrating a method for manufacturing a circuit board according to an embodiment of the present invention; Figure 11 A cross-sectional schematic diagram of a multilayer board provided in an embodiment of the present invention; Figure 12 A cross-sectional schematic diagram of another multilayer board provided in an embodiment of the present invention; Figure 13 This invention provides a schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, as shown in an embodiment of the invention. Figure 14 A schematic cross-sectional view of a multilayer board during another circuit board manufacturing process provided in an embodiment of the present invention; Figure 15 A cross-sectional schematic diagram of a circuit board provided in an embodiment of the present invention; Figure 16 A top view of a circuit board provided in an embodiment of the present invention; Figure 17 A flowchart illustrating another method for manufacturing a circuit board according to an embodiment of the present invention; Figure 18 A schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, as provided in an embodiment of the present invention; Figure 19 A schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, as provided in an embodiment of the present invention; Figure 20 A schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, as provided in an embodiment of the present invention; Figure 21 A flowchart illustrating another method for manufacturing a circuit board according to an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Currently, there is a circuit board design requirement that includes both metallized and non-metallized holes within a metallized blind slot for mounting through-hole components. The metallized holes are surrounded by a copper ring, known as a metallized hole ring, for soldering component leads and ensuring electrical conductivity between the component and the circuit board. The non-metallized holes are used to place through-hole components and secure them; therefore, the non-metallized holes in the metallized blind slot cannot have hole rings to provide electrical isolation and prevent short circuits.

[0022] Figure 1 A top view of a circuit board provided for related technologies. Figure 1 A circuit board including metallized vias 40 and non-metallized vias 60 is shown. Figure 2 Another top view of a circuit board provided for related technologies. Figure 2 The diagram shows a circuit board with metallized holes 40 and non-metallized holes 60 in a metallized blind slot 10. The hole rings at the upper and lower openings of the non-metallized holes 60 are non-metallized hole rings. Non-metallized hole rings mean that a ring-shaped copper-free area is formed around the non-metallized holes at the bottom of the metallized blind slot and on the surface of the multilayer board away from the metallized blind slot. Figure 3 A cross-sectional view of a circuit board provided for related technologies. Figure 3 The overall effect of the circuit board is shown from a cross-sectional view.

[0023] The typical process for manufacturing circuit boards using related technologies includes: pre-processing, lamination, drilling, blind soldering, plasma etching, copper plating, board surface electroplating, outer layer pretreatment, outer layer lamination, outer layer exposure, outer layer development, pattern electroplating, secondary drilling, alkaline etching, and post-processing. Pre-processing may include material preparation, cleaning, inner layer circuit fabrication, inner layer circuit inspection, inner layer copper plating, and board stacking. Post-processing may include outer layer circuit inspection, solder mask application, text silkscreen printing, surface treatment, final shape cutting, and electrical testing. Figure 4This diagram illustrates a cross-sectional view of a multilayer board during the manufacturing process of a circuit board, providing insights into related technologies. After pre-processing steps including lamination, drilling, blind soldering, plasma plating, copper plating, surface electroplating, and outer layer pretreatment, a multilayer board can be formed as shown below. Figure 4 The metallized blind trench shown has metallized holes inside, and both the metallized blind trench and the metallized holes are copper-plated. After an outer layer lamination process, a structure like... Figure 4 The structure shown has a dry film 30 applied to the upper and lower surfaces of the multilayer board.

[0024] Figure 5 This provides another schematic cross-sectional view of a multilayer board in the process of manufacturing a circuit board, which is shown in the diagram below. The multilayer board is formed after outer layer exposure, outer layer development, and pattern electroplating. Figure 5 In the structure shown, a portion of the lower surface of the multilayer board is covered with dry film 30, and the area covered by dry film 30 is not plated with tin. The areas of the metallized blind trench 10 and metallized via 40 not covered by dry film are plated with tin.

[0025] Because there is a stepped height difference between the upper surface of the multilayer board and the metallized blind groove 10, when the dry film is applied to the entire board, the dry film 30 is suspended above the metallized blind groove 10 and cannot be effectively applied to the bottom of the metallized blind groove 10. After the outer layer is exposed and developed, the dry film above the metallized blind groove 10 will be removed. After pattern electroplating, copper and tin layers are plated on the bottom of the metallized blind groove 10 and at the metallized hole position at the bottom of the metallized blind groove 10. Figure 6 Another schematic diagram of a multilayer board cross-section in the process of manufacturing a circuit board is provided for related technologies, such as... Figure 6 As shown, a secondary drilling is performed at the location where the non-metallized hole is to be formed, on the side covered with dry film, to form a non-metallized hole 60. As mentioned earlier, the dry film on the upper surface of the multilayer board cannot be shaped during film application, and it is impossible to form a non-metallized hole with a non-metallized hole ring at the location of the metallized blind slot 10.

[0026] Figure 7 This is another schematic cross-sectional view of a multilayer board in the process of manufacturing a circuit board, provided for related technologies. Figure 8 This is another schematic cross-sectional view of a multilayer board in the process of manufacturing a circuit board, provided for related technologies. Figure 9 This provides a schematic cross-sectional view of a circuit board formed by a circuit board manufacturing method using related technologies; Reference Figures 7-9 Remove the dry film in sequence ( Figure 7 ), etching to remove copper layer ( Figure 8 ) and stripped tin ( Figure 9 ), ultimately forming as Figure 9The multilayer board shown is processed into a circuit board. It can be observed that in circuit boards manufactured using related techniques, the dry film cannot cover the top opening and ring area of ​​the non-metallized vias, resulting in tin forming on the surface of the multilayer board and the bottom of the metallized blind trenches after pattern plating. After alkaline etching, the copper layer of the top opening and ring of the non-metallized vias is covered by tin and not removed. Therefore, the ring at the top opening of the non-metallized via is a metallized ring, which may result in insufficient electrical clearance with surrounding traces, pads, or copper foil, potentially causing short circuits during production or use; or the excess copper ring may alter its capacitance or impedance characteristics, affecting high-frequency signals or power integrity. Circuit boards manufactured using the above techniques do not meet design requirements.

[0027] Given that existing circuit board manufacturing methods cannot meet design requirements, this invention provides a method for manufacturing non-metallic hole rings at the upper and lower openings of non-metallic holes in metallized blind slots. Figure 10 The flowchart illustrates a method for manufacturing a circuit board according to an embodiment of the present invention. Figure 11 This is a cross-sectional schematic diagram of a multilayer board provided in an embodiment of the present invention. Figure 12 This is a cross-sectional schematic diagram of another multilayer board provided in an embodiment of the present invention. The circuit board manufacturing method of the present invention is applicable to scenarios where multilayer boards are processed to form circuit boards. For example, the circuit board manufacturing method of the present invention can be used in scenarios where multilayer boards are processed to form circuit boards. Figure 11 The multilayer board shown is processed to form a circuit board. For example... Figure 10 As shown, the method for manufacturing a circuit board according to an embodiment of the present invention includes: S101, Provide multilayer boards to be processed.

[0028] refer to Figure 11 The multilayer board 100 includes a metallized blind groove 10. A protective layer 20 is formed on the surface of the multilayer board 100 and the bottom of the metallized blind groove 10. At least a portion of the back side of the multilayer board 100 where the metallized blind groove 10 is provided is covered with a dry film 30. The area covered with the dry film 30 is not covered with a protective layer 20.

[0029] In this embodiment of the invention, the metallized blind groove 10 can be formed by performing blind soldering, plasma, and electroless copper plating processes on the multilayer board 100. The bottom and sidewalls of the metallized blind groove 10 are plated with a copper layer, and a protective layer 20 is plated on the surface of the copper layer. The back side of the multilayer board 100 where the metallized blind groove 10 is provided can be the surface of the multilayer board 100 away from the metallized blind groove 10.

[0030] The protective layer 20 can be a metal layer, such as metallic tin. The chemical stability of the protective layer 20 is greater than that of the copper layer, and it can protect the copper layer covered by the protective layer 20 from being etched away during etching. The location covering the dry film 30 can be the location where the pre-formed non-metallized via is formed. The location covering the dry film 30 does not form the protective layer 20. During the stripping etching, the dry film 30 is stripped first. After the dry film 30 is removed, the copper layer in the area covered by the dry film 30 is etched away. Finally, the protective layer 20 is removed.

[0031] refer to Figure 12 In some embodiments, a metallized hole 40 is provided in the metallized blind groove 10, and a protective layer 20 is formed on the surface of the metallized blind groove 10 and the surface of the metallized hole 40.

[0032] The metallized holes 40 can be obtained by drilling before blind soldering of the multilayer board 100. The metallized holes 40 exist in the metallized blind grooves 10 formed after plasma and electroless copper plating processes on the multilayer board 100. The surface of the metallized holes 40 in the metallized blind grooves 10 is plated with a copper layer, and a protective layer 20 is plated on the surface of the copper layer. For example... Figure 12 In the multilayer board 100, the position covering the dry film 30 can be the position where the pre-formed non-metallized holes are formed, or the position outside the hole ring of the metallized holes 40. The metallized blind groove 10 includes one, two, or more metallized holes 40, which can be set according to the actual situation. The embodiments of the present invention do not impose specific limitations on this.

[0033] S102. At the location where a non-metallized hole is pre-formed at the bottom of the metallized blind trench, back-drill from the bottom of the metallized blind trench to remove the protective layer and the copper layer covered by the protective layer at the location where the non-metallized hole is pre-formed at the bottom of the metallized blind trench.

[0034] Figure 13 This is a schematic cross-sectional view of a multilayer board during the manufacturing process of a circuit board, provided as an embodiment of the present invention. Figure 14 This is a schematic cross-sectional view of a multilayer board during another circuit board manufacturing process provided in an embodiment of the present invention, with reference to... Figure 13 and Figure 14Back drilling can be performed using drill bit 50. The second depth y can represent the sum of the thickness of the protective layer 20 at the bottom of the metallized blind slot 10, the location where the non-metallized hole 60 is pre-formed, and the thickness of the copper layer covering the location of the protective layer 20. In actual manufacturing, the back drilling depth x can be slightly greater than the second depth y to ensure that the drill bit 50 at least removes the copper layer covering the location of the protective layer 20 without affecting the overall function of the circuit board. As mentioned above, the metallized hole ring at the upper opening of the non-metallized hole 60 can be removed. The number of non-metallized holes 60 can be one or more. Back drilling can be performed at different locations using one drill bit 50, or multiple drill bits 50 can be used to back drill to form multiple non-metallized hole rings at the upper opening of the non-metallized hole 60. This embodiment of the invention does not impose specific limitations on the number of non-metallized holes 60, the number of drill bits 50, or the back drilling method.

[0035] S103. Drill a secondary hole from the back of the multilayer board where the metallized blind groove is provided until it connects with the back drill position.

[0036] The diameter of the secondary borehole is smaller than the diameter of the back borehole.

[0037] refer to Figure 14 A hole can be drilled at the position of the pre-formed non-metallized hole using a drill bit. The position of the secondary drilling is opposite to the position of the back drilling, so that the non-metallized hole 60 formed by the secondary drilling can be connected with the back drilling hole.

[0038] It is understandable that, from the back side of the multilayer board 100 where the metallized blind groove 10 is provided, a drill bit 50 is used to drill at the position where the non-metallized hole is pre-formed. The back side of the multilayer board 100 where the metallized blind groove 10 is provided is covered by a dry film 30, meaning a secondary drilling is performed from the dry film 30. The drill bit diameter for the secondary drilling is smaller than the width of the dry film 30. Half the difference between the dry film width d1 and the secondary drilling diameter d2 is the width d3 of the non-metallized hole ring at the lower opening of the non-metallized hole 60. For example, the width d3 of the non-metallized hole ring at the lower opening of the non-metallized hole 60 is: The width of the hole ring must meet electrical isolation requirements. Half the difference between the back-drilled hole diameter d4 and the secondary drilled hole diameter d2 is the width d5 ​​of the non-metallized hole ring at the opening of the non-metallized hole 60. For example, the width d5 ​​of the non-metallized hole ring at the opening of the non-metallized hole 60 is: The width of the hole ring must meet electrical isolation requirements. The diameter of the drill bit used for secondary drilling is smaller than that used for back drilling. The secondary drilling diameter d2 can be the diameter of the non-metallized hole 60, and the back drilling diameter d4 can be the diameter of the drill bit 50. It should be noted that the dry film width d1, secondary drilling diameter d2, and back drilling diameter d4 are only used to explain the width of the non-metallic ring at the upper and lower openings of the formed non-metallized hole 60. In actual manufacturing, appropriate dry film width d1, secondary drilling diameter d2, and back drilling diameter d4 can be selected according to the actual situation to form a printed circuit board that meets the design requirements.

[0039] S104. Remove the dry film and protective layer to form non-metallized pores.

[0040] Among them, the hole rings at the upper and lower openings of the non-metallized hole 60 are non-metallized hole rings.

[0041] Figure 15 This is a cross-sectional schematic diagram of a circuit board provided in an embodiment of the present invention. Figure 16 A top view of a circuit board provided in an embodiment of the present invention, with reference to... Figure 14 , Figure 15 and Figure 16 In such Figure 14 Based on the multilayer board 100 shown, the multilayer board 100 is subjected to the following steps: film stripping to remove the dry film 30; alkaline etching to remove the copper layer covered by the dry film 30; and tin removal to remove the protective layer 20, ultimately forming the multilayer board 100 as shown. Figure 15 The multilayer board 100 shown includes a metallized blind slot 10, in which metallized holes 40 and non-metallized holes 60 are provided. The surfaces of the metallized blind slot 10 and the metallized holes 40 are covered with a copper layer. The upper and lower openings of the metallized holes 40 are equipped with metallized hole rings, and the upper and lower openings of the non-metallized holes 60 are equipped with non-metallized hole rings. Figure 16 The shape of the metallized blind slot 10 shown in the top view can be circular, elliptical, or square, etc. The multilayer board 100 can be processed into a circuit board that meets design requirements. A indicates the upper surface of the multilayer board 100 where the metallized blind slot 10 is located.

[0042] It is understandable that if the metallized blind slot 10 of the multilayer board 100 does not have a metallized hole 40, the final circuit board will include the metallized blind slot 10, the metallized blind slot 10 has a non-metallized hole 60, the bottom and the wall of the metallized blind slot 10 have a copper layer, and the hole rings at the upper and lower openings of the non-metallized hole 60 are non-metallized hole rings.

[0043] According to the technical solution of the present invention, by back-drilling from the bottom of the metallized blind slot at the location where a non-metallized hole is pre-formed, the protective layer and the copper layer covered by the protective layer at the location of the pre-formed non-metallized hole at the bottom of the metallized blind slot can be removed, at least the copper layer at the upper opening and the hole ring of the pre-formed non-metallized hole can be removed. A secondary drilling is performed from the back side of the multilayer board where the metallized blind slot is provided until it connects with the back-drilled location; the diameter of the secondary drilling hole is smaller than the diameter of the back-drilled hole. The dry film and protective layer are removed to form a non-metallized hole. After removing the dry film, the copper layer at the hole ring of the lower opening of the non-metallized hole can be removed by etching, thus making the hole rings at the upper and lower openings of the non-metallized hole non-metallized. In summary, the technical solution of the embodiments of the present invention enables non-metallized holes in the metallized blind slots of the circuit board, including the hole rings at the upper and lower openings, to be non-metallized, thus meeting the requirements for mounting plug-in components and electrical isolation.

[0044] Figure 17 This is a flowchart illustrating another method for manufacturing a circuit board according to an embodiment of the present invention. The embodiments of the present invention can be implemented as follows: Figure 4 This fabrication method is implemented on the multilayer board shown. For example... Figure 17 As shown, the method for manufacturing a circuit board according to an embodiment of the present invention may include: S201. A dry film is covered on the first surface of the multilayer board and the back surface of the multilayer board where metallized blind grooves are provided, and the dry film is exposed and developed.

[0045] refer to Figure 4 The first surface of the multilayer board 100 can be the upper surface with the metallized blind groove 10. A dry film 30 is covered on the upper surface with the metallized blind groove 10 and the surface of the multilayer board 100 away from the metallized blind groove. The positions where the dry film 30 needs to be retained are exposed and cured, and the positions where the dry film 30 does not need to be retained are developed. For example, the dry film 30 at the lower opening and the hole ring of the pre-formed non-metallized hole position is exposed. If there is a metallized hole in the metallized blind groove 10, the dry film 30 at the lower opening and hole ring position of the metallized hole is not exposed. The remaining positions on the first surface of the multilayer board 100 and the surface on the side of the metallized blind groove of the multilayer board 100 can be exposed and developed according to the circuit pattern design requirements.

[0046] S202. Perform pattern electroplating on the multilayer board to form the multilayer board to be processed.

[0047] right Figure 4 The multilayer board 100 shown is subjected to pattern electroplating to form a pattern as shown. Figure 12 The multilayer board 100 shown has a protective layer 20 formed at the location where the dry film 30 is covered, and a protective layer 20 is formed at the location where the dry film 30 is not covered.

[0048] S203. Place a rigid cover plate on the first surface of the multilayer board and control the drill bit to start drilling from the surface of the rigid cover plate.

[0049] In particular, since the metallized blind slot area is a suspended structure, if a thin or locally insufficient rigid cover plate is used, the cover plate at the metallized blind slot position is prone to local collapse and deformation during back drilling. At the same time, it will cause the drilling rig pressure foot to fail to effectively tighten the support, which can easily lead to back drilling deviation.

[0050] Figure 18 This is a cross-sectional view of a multilayer board during another circuit board manufacturing process provided in an embodiment of the present invention, with reference to... Figure 18 When the drill bit 50 back-drills the multilayer board 100, it starts drilling from the surface of the rigid cover plate 70. The rigid cover plate 70 can provide rigid support for the drill bit 50, preventing local sagging and deformation at the location of the metallized blind groove 10 during back-drilling.

[0051] In some embodiments, the rigid cover plate 70 includes a core plate or a drilled pad.

[0052] By using a core plate or a drilling pad as a rigid cover plate 70 to provide rigid support, it is possible to avoid the drilling machine's pressure foot being unable to effectively press the support due to local sagging and deformation of the cover plate at the metallized blind slot 10, which would cause the drill bit 50 to deviate from its position when drilling.

[0053] Figure 19 This is a schematic cross-sectional view of a multilayer board during the fabrication of a circuit board, as provided in another embodiment of the present invention. Figure 19 As shown, in some embodiments, optionally, the rigid cover plate 70 includes a non-conductive region and a conductive region, with the conductive region surrounding the non-conductive region; the non-conductive region includes the drilling position of the drill bit 50; the conductive region is provided with a first conductive layer, which contacts the protective layer 20 of the multilayer board 100, and the material of the protective layer 20 includes tin.

[0054] refer to Figure 19 The non-conductive area of ​​the rigid cover plate 70 may include the drilling position of the drill bit 50. The first conductive layer of the rigid cover plate 70 is in contact with the protective layer 20 on the sidewall of the metallized blind groove 10, thereby achieving electrical connection with the protective layer 20 at the bottom of the metallized blind groove 10. By employing methods such as... Figure 19 The rigid cover plate 70 shown ensures that the conductive contacts of the drilling rig and the bottom of the metallized blind groove 10 can form an electrical connection path.

[0055] S204. When the drill bit is lowered to the bottom of the metallized blind groove, the initial back-drilling position of the drill bit is obtained, and back-drilling is performed based on the initial back-drilling position.

[0056] Figure 20 This is a cross-sectional view of a multilayer board during another circuit board manufacturing process provided in an embodiment of the present invention, with reference to... Figure 20 When the tip of the drill bit 50 contacts the protective layer 20 at the bottom of the metallized blind groove 10, the initial position of the back drill is acquired and recorded.

[0057] Since the purpose of back drilling is to remove copper from the annulus at the upper opening of non-metallized holes, the back drilling depth is relatively shallow. If the multilayer board is only about 100mm thick, an excessively deep back drilling depth will result in insufficient mounting rigidity at the non-metallized hole position, leading to insufficient support. Therefore, the accuracy requirement for the back drilling depth is high. If the depth calculation is based on the surface of the rigid cover plate 70, the large drilling stroke can easily lead to problems with drilling too deep or too shallow, making it difficult to control the back drilling depth accuracy. Compared to using the tip of the drill bit 50 touching the surface of the rigid cover plate 70 as the initial back drilling position, using the tip of the drill bit 50 touching the protective layer 20 at the bottom of the metallized blind groove 10 as the initial back drilling position can shorten the drilling depth from the surface of the rigid cover plate 70 to the bottom of the metallized blind groove 10, thereby effectively improving the back drilling depth control accuracy.

[0058] In this process, based on the initial back-drilling position, the drill bit 50 is controlled to drill downwards. Since the tip of the drill bit 50 has a certain angle with the horizontal plane, the back-drilling depth can be slightly greater than the second depth, thereby enabling the drill bit 50 to drill through at least the bottom of the metallized blind groove 10 and the copper layer covered by the protective layer 20 at the pre-formed non-metallized hole position.

[0059] S205. Drill a second hole from the back of the multilayer board where the metallized blind groove is provided until it connects with the back drill position.

[0060] S206. Remove the dry film and protective layer to form non-metallized pores.

[0061] Among them, the hole rings at the upper and lower openings of the non-metallized hole are non-metallized hole rings.

[0062] Figure 21 A flowchart illustrating another method for manufacturing a circuit board according to an embodiment of the present invention is shown below. Figure 21 As shown, the circuit board manufacturing process is as follows: S301. A dry film is covered on the first surface of the multilayer board and the back surface of the multilayer board where the metallized blind groove is provided, and the dry film is exposed and developed.

[0063] S302. Perform pattern electroplating on the multilayer board to form the multilayer board to be processed.

[0064] S303. Place a rigid cover plate on the first surface of the multilayer board and control the drill bit to start drilling from the surface of the rigid cover plate.

[0065] S304. Make the drill conductive contact with the first surface of the multilayer board and connect the drill conductive contact to the drill spindle.

[0066] S305. When the tip of the drill bit contacts the bottom of the metallized blind groove, the drill spindle acquires an electrical signal based on the drill bit.

[0067] refer to Figure 20 In this case, the drill rig conductive contact can be a drill rig mushroom head, and the drill rig conductive contact contacts the protective layer 20 of the first surface A of the multilayer board. The bottom of the metallized blind groove 10 is physically connected to the first surface A of the multilayer board through the protective layer 20. Or, as... Figure 19 The first conductive layer of the rigid cover plate 70 shown contacts the protective layer 20 on the side wall of the metallized blind groove 10, thereby enabling an electrical connection between the first conductive layer of the rigid cover plate 70 and the bottom of the metallized blind groove 10.

[0068] The drill bit 50 is made of conductive material. When the tip of the drill bit 50 contacts the protective layer 20 on the bottom surface of the metallized blind groove 10, the tip of the drill bit 50, the protective layer 20 on the bottom of the metallized blind groove 10, and the conductive contact of the drill can form an electrical connection path, so that the drill spindle can obtain the electrical signal at this time.

[0069] It is understandable that the rigid cover plate 70 includes conductive and non-conductive areas. If the rigid cover plate 70 were entirely conductive, the drill bit 50 would acquire an electrical signal upon contact with its surface. In this case, depth calculation would begin from the surface of the rigid cover plate 70, making it difficult to control the accuracy of the back-drilling depth. Therefore, by using a rigid cover plate 70 that includes both conductive and non-conductive areas, an electrical signal is generated only when the drill bit 50 contacts the protective layer 20 at the bottom of the metallized blind groove 10, thereby improving the control accuracy of the back-drilling depth. The conductive area of ​​the rigid cover plate 70 is electrically connected to at least the sidewall surface of the metallized blind groove 10, and is at least a non-conductive area at the drilling position of the drill bit 50. The size of the conductive and non-conductive areas is not specifically limited.

[0070] S306. Determine the initial back-drilling position of the drill bit based on the electrical signal.

[0071] In this process, after the drill bit begins to drill down from the surface of the rigid cover plate, the drill spindle continuously collects whether an electrical signal is generated until it collects the electrical signal generated when the drill bit first contacts the bottom of the metallized blind groove. The initial position of the back drill is determined based on the electrical signal at this moment.

[0072] S307. Set the back drill depth based on the thickness of the protective layer at the position of the pre-formed non-metallized hole at the bottom of the metallized blind groove, the thickness of the copper layer covered by the protective layer, and the compensation parameters.

[0073] The compensation parameters are obtained through at least one of the following: the drill bit tip angle, the protective layer thickness tolerance, the copper layer thickness tolerance covered by the protective layer, and the machining tolerance of the back drilling equipment itself.

[0074] The intersection of the two cutting edges of the drill bit tip forms an angle, creating an ineffective cutting area and resulting in ineffective drilling depth. Therefore, the depth control error caused by the drill bit tip angle can be compensated for in advance, preventing the incomplete removal of the protective multilayer and its covering copper layer at the location of the non-metallized hole. Furthermore, the thickness of the protective layer and its covering copper layer at the location of the non-metallized hole will vary due to fluctuations in the processing technology. By setting compensation parameters, the effects of ineffective drilling depth and process fluctuations can be offset, achieving precise compensation for back-drilling depth. Controlling the drill bit according to this back-drilling depth effectively improves the control accuracy of the back-drilling depth. On the one hand, it avoids insufficient drilling depth, resulting in incomplete removal of the protective layer and its covering copper layer at the location of the non-metallized hole, thus preventing the formation of a non-metallized hole ring. On the other hand, it avoids excessive drilling depth, leading to insufficient remaining thickness of the board material at the location of the non-metallized hole, which in turn reduces the rigidity and support of the component mounting.

[0075] Optionally, the drill bit tip angle is greater than 165°.

[0076] The drill bit angle greater than 165° is a setting to prevent excessive deviations in the drilling depth caused by the drill bit's tip angle. By selecting a drill bit with a suitable tip angle, ineffective drilling depth can be reduced, and accuracy improved.

[0077] S308. Based on the initial position of the back drill, back drill is performed according to the back drill depth.

[0078] In particular, by determining the back drill depth based on the second depth and compensation parameters, and then drilling at that back drill depth, the back drill accuracy can be improved.

[0079] S309. Drill a secondary hole from the back of the multilayer board where the metallized blind groove is provided until it connects with the back drill position.

[0080] S310, Remove dry film, remove copper from the dry film-covered area using chemical etching process, and remove protective layer.

[0081] After secondary drilling, the dry film can be removed using a stripping process, followed by a chemical etching process to remove the copper covering the dry film, and finally, the protective layer can be removed. This process creates a non-metallized hole with a non-metallized hole ring at the bottom.

[0082] In summary, compared to the manufacturing methods of related technologies, the embodiments of the present invention only require an additional back-drilling process at the pre-formed non-metallized hole positions after pattern electroplating. By adding only one back-drilling process, the non-metallization processing of the hole ring of the non-metallized hole at the bottom of the metallized blind groove can be completed, resulting in a circuit board that meets the design requirements. The overall process modification is minor, the number of additional steps is small, and the impact on the production cycle is low.

[0083] This invention also provides a circuit board, which can be manufactured by the circuit board manufacturing method of any embodiment of this invention, for example, a multilayer board as shown in Figure 11- Figure 14 The structure shown can be formed as shown in Figure 15, and can be based on, for example, the structure shown in Figure 15. Figure 15 The multilayer board shown is processed into a final circuit board after subsequent processes. The circuit board includes a metallized blind slot, which may contain metallized holes and annular non-metallized holes with non-metallized hole rings. The circuit board produced by the embodiments of the present invention has the beneficial effects of any embodiment of the present invention.

[0084] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0085] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for manufacturing a circuit board, characterized in that, include: A multilayer board to be processed is provided; wherein the multilayer board includes a metallized blind groove, a protective layer is formed on the surface of the multilayer board and the bottom of the metallized blind groove, at least a portion of the back side of the multilayer board where the metallized blind groove is provided is covered with a dry film, and the area covered with the dry film is not covered with the protective layer. At the location where a non-metallized hole is pre-formed at the bottom of the metallized blind slot, back drilling is performed from the bottom of the metallized blind slot to remove the protective layer and the copper layer covered by the protective layer at the location where the non-metallized hole is pre-formed at the bottom of the metallized blind slot. A secondary drilling is performed on the back side of the multilayer board where the metallized blind groove is provided, until it connects with the back drilling position; the diameter of the secondary drilling hole is smaller than the diameter of the back drilling hole; Remove the dry film and the protective layer to form the non-metallized hole; the hole rings at the upper and lower openings of the non-metallized hole are non-metallized hole rings.

2. The manufacturing method according to claim 1, characterized in that, The metallized blind groove is provided with metallized holes, and the protective layer is formed on the surface of the metallized blind groove and the metallized holes.

3. The manufacturing method according to claim 1, characterized in that, The back drilling from the bottom of the metallized blind groove at the location where a non-metallized hole is pre-formed at the bottom of the metallized blind groove includes: A rigid cover plate is placed on the first surface of the multilayer board, and the drill bit is controlled to start drilling from the surface of the rigid cover plate. When the drill bit drills down to the bottom of the metallized blind groove, the initial back-drilling position of the drill bit is obtained, and back-drilling is performed based on the initial back-drilling position.

4. The manufacturing method according to claim 3, characterized in that, The rigid cover plate includes a core plate or a drilled pad plate.

5. The manufacturing method according to claim 4, characterized in that, The rigid cover plate includes a non-conductive region and a conductive region, wherein the conductive region surrounds the non-conductive region; The non-conductive area includes the drill bit's lowering position; The conductive area is provided with a first conductive layer, which is in contact with the protective layer of the multilayer board. The material of the protective layer includes tin.

6. The manufacturing method according to claim 3, characterized in that, The drill bit has a tip angle greater than 165°.

7. The manufacturing method according to claim 3, characterized in that, When the drill bit descends to contact the bottom of the metallized blind groove, the initial back-drilling position of the drill bit is obtained, and back-drilling is performed based on the initial back-drilling position, including: The drill rig conductive contact is brought into contact with the first surface of the multilayer board, and the drill rig conductive contact is connected to the drill rig spindle; When the tip of the drill bit contacts the bottom of the metallized blind groove, the drill spindle acquires an electrical signal based on the drill bit; Based on the electrical signal, the initial back-drilling position of the drill bit is determined; The back drill depth is set according to the thickness of the protective layer at the position of the pre-formed non-metallized hole at the bottom of the metallized blind slot, the thickness of the copper layer covered by the protective layer, and the compensation parameters. Back drilling is performed based on the initial position of the back drill and according to the drilling depth of the back drill.

8. The manufacturing method according to claim 1, characterized in that, The process of removing the dry film and the protective layer to form the non-metallized pores includes: Remove the dry film, remove the copper in the area covered by the dry film using a chemical etching process, and remove the protective layer.

9. The manufacturing method according to claim 1, characterized in that, The process of forming the multilayer board to be processed includes: A dry film is covered on the first surface of the multilayer board and the back side of the multilayer board where the metallized blind groove is provided, and the dry film is exposed and developed. The multilayer board is patterned by electroplating to form the multilayer board to be processed.

10. A circuit board, characterized in that, The circuit board is manufactured by the method of manufacturing any one of claims 1-9.

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