Hole plugging method and circuit board

Abstract

The invention belongs to the technical field of circuit boards, and particularly relates to a hole plugging method and a circuit board. The hole plugging method comprises the following steps: preparing a substrate, wherein the substrate is provided with a first plate surface and a second plate surface which is arranged opposite to the first plate surface; drilling is conducted, specifically, the base plate is flatly laid, a female hole is drilled in the first plate face in the first direction, the female hole is provided with a first hole opening located in the first plate face, and the first direction points to the second plate face along the first plate face; electroplating: electroplating a metal material on the hole wall of the female hole so as to enable the female hole to form a plated hole, and arranging a preset position on the hole wall of the plated hole; the area of the cross section of the hole section, between the first hole opening and the preset position, of the plating hole is gradually reduced in the first direction; and hole plugging: injecting a fluid material into the plating hole along the hole wall of the plating hole at the first hole opening. According to the invention, the flow rate of the resin material can be controlled, so that the risk that the resin plug hole is not full due to too fast resin flow can be greatly reduced, and plug hole cavities and plug hole recesses are prevented from being formed in the plated hole.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit boards, and in particular relates to a plugging method and a circuit board. Background Art

[0002] At present, PCB (Printed Circuit Board) has a through-hole resin plugging process according to application requirements. In the actual production process, resin plugging hole voids or resin plugging hole depressions often occur. Especially when the PCB board thickness is thick or the through-hole aperture is small, the defect rate caused by resin plugging hole voids or depressions is high, resulting in multiple rework of resin plugging and resin grinding processes, which wastes production capacity and also poses quality risks.

[0003] The factors that cause such defects are not only related to the high aspect ratio or small through-hole diameter of the PCB itself, but also to the viscosity of the plugging resin. Generally, the through-hole is a straight through-hole. When the viscosity of the resin ink is low, the resin flows along the vertical hole wall during the plugging process. The flow speed will be too fast, which is easy to cause resin loss, resulting in an incomplete plugging. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a plugging method, which aims to solve the problem of how to control the flow of resin and improve the plugging quality.

[0005] To achieve the above purpose, the technical solution adopted in this application is:

[0006] In a first aspect, a plugging method is provided, comprising the following steps:

[0007] Prepare a substrate, wherein the substrate has a first surface and a second surface disposed opposite to the first surface;

[0008] Drilling, laying the substrate flat, and drilling a mother hole on the first board surface along a first direction, wherein the mother hole has a first opening located on the first board surface, and the first direction points along the first board surface to the second board surface;

[0009] Electroplating, electroplating metal material on the hole wall of the mother hole to form a plated hole, wherein a predetermined position is provided on the hole wall of the plated hole; the cross-sectional area of ​​the hole section of the plated hole between the first hole opening and the predetermined position gradually decreases along the first direction;

[0010] The plugging process injects the fluid material into the plated hole along the hole wall of the plated hole at the first hole opening.

[0011] In some embodiments, the hole wall of the plated hole between the first hole opening and the predetermined position is a convex arc surface.

[0012] In some embodiments, the mother hole is a through hole and has a second opening located on the second board surface, and the cross-sectional area of ​​the hole section of the plated hole located between the second opening and the predetermined position gradually decreases along a second direction, and the second direction points to the first board surface along the second board surface.

[0013] In some embodiments, the hole wall of the plated hole between the second hole opening and the predetermined position is a convex arc surface.

[0014] In some embodiments, the mother hole is a through hole, the diameter of the mother hole is greater than 0 and less than or equal to 0.25 mm, or the ratio of the hole depth to the hole diameter of the mother hole is greater than or equal to 8:1; the plugging step includes:

[0015] S41: injecting the fluid material into the plated hole at the first opening to fill a portion of the plated hole;

[0016] S42: Turn the substrate 180 degrees, and inject the fluid material into the plated hole at the second opening to fill another portion of the plated hole.

[0017] In some embodiments, in the electroplating step, a pulse electroplating method is used to electroplate the metal material on the hole wall of the mother hole.

[0018] In some embodiments, before the plugging step, the substrate that has undergone the electroplating step is heated to a predetermined temperature and kept warm.

[0019] In some embodiments, the via plugging method further comprises curing, wherein the substrate filled with the fluid material is baked to cure the fluid material.

[0020] In some embodiments, a metal sheet and an air guide pad are prepared, the air guide pad is located below the metal sheet, the two side surfaces of the substrate are respectively connected to the metal sheet and the air guide pad, the metal sheet is provided with a first avoidance hole at a position corresponding to the mother hole, and the air guide pad is provided with a second avoidance hole at a position corresponding to the mother hole.

[0021] In a second aspect, a circuit board is provided, which is processed by plugging holes using the plugging method.

[0022] The beneficial effect of the present application is that: by making the hole wall near the first orifice have a certain inclination relative to the central axis of the plated hole, the inclined hole wall can appropriately slow down the flow of resin, thereby realizing the control of the flow rate of the resin material. The resin flows from the first orifice to a predetermined position, and forms a certain aggregation at the predetermined position before flowing to the other side of the plated hole, thereby greatly reducing the risk of incomplete resin plugging due to too fast resin flow, avoiding the formation of plugging holes and plugging depressions in the plated hole, and improving the plugging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or exemplary technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is a flow chart of a plugging method provided in an embodiment of the present application;

[0025] Figure 2 is a schematic diagram of a substrate provided in another embodiment of the present application in which a mother hole is drilled;

[0026] Figure 3 yes Figure 2 Schematic diagram of copper plating on a mother hole in a substrate;

[0027] Figure 4 yes Figure 3 A schematic diagram of the entire plated hole plugging from the first hole opening;

[0028] Figure 5 yes Figure 3 A schematic diagram of partially plated via plugging from a first hole opening;

[0029] Figure 6 yes Figure 5 Schematic diagram of partially plated via plugging from the second hole opening.

[0030] Among them, the reference numerals in the figure are:

[0031] 20, substrate; 201, first board surface; 202, second board surface; 211, first opening; 212, second opening; 210, mother hole; 220, plated hole; 310, metal sheet; 301, first avoidance hole; 320, air guide pad; 302, second avoidance hole; DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present application.

[0033] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0034] See also Figures 1 to 3 The embodiment of the present application provides a plugging method for plugging a hole in a substrate 20, where the substrate 20 may be a PCB board that has been processed by a previous process. The plugging method includes the following steps:

[0035] S1: preparing a substrate 20, wherein the substrate 20 has a first surface 201 and a second surface 202 disposed opposite to the first surface 201;

[0036] S2: drilling, placing the substrate 20 flat on a drilling device, and using the drilling device to drill a mother hole 210 on the first board surface 201 along a first direction, wherein the mother hole 210 has a first opening 211 located on the first board surface 201, and the first direction points from the first board surface 201 to the second board surface 202, that is, in this application, the first direction is vertically downward;

[0037] S3: electroplating, electroplating metal material on the hole wall of the mother hole 210 to form a plated hole 220 in the mother hole 210, and a predetermined position is set on the hole wall of the plated hole 220; the cross-sectional area of ​​the hole section of the plated hole 220 between the first hole opening 211 and the predetermined position gradually decreases along the first direction; it can be understood that the metal material can be metal copper, and a layer of metal copper can be electroplated on the hole wall of the mother hole 210 through copper deposition and electroplating processes, and the thickness of the copper layer gradually increases along the first direction, so that the aperture of the plated hole 220 gradually decreases along the first direction, that is, the hole wall of the plated hole 220 close to the first hole opening 211 is inclined, such as a cone shape; it can be understood that the predetermined position can be located at one-quarter of the hole depth or one-third of the hole depth of the plated hole 220. In the embodiment of the present application, the predetermined position is located at one-half of the hole depth of the plated hole 220, that is, the middle position of the plated hole 220. In other embodiments, it can be selected according to actual conditions and is not limited here.

[0038] S4: Plug the hole. At the first orifice 211, inject the fluid material into the plated hole 220 along the hole wall of the plated hole 220. In the present application, the fluid material is a resin. The resin has a certain viscosity, so it can flow downward along the hole wall of the plated hole 220. Since the hole wall of the plated hole 220 is inclined, the gravity of the resin is decomposed into a vertical downward component and a vertical component of the hole wall, so that the flow rate of the resin on the hole wall of the plated hole 220 can be reduced to control the resin to slowly flow into the plated hole 220, avoiding the formation of plug hole cavities and plug hole depressions.

[0039] See also Figures 1 to 3 In the embodiment of the present application, the hole wall near the first orifice 211 has a certain inclination relative to the central axis of the plated hole 220, and the inclined hole wall can appropriately slow down the flow of resin, thereby achieving control of the flow rate of the resin material. The resin flows from the first orifice 211 to a predetermined position, and forms a certain aggregation at the predetermined position before flowing to the other side of the plated hole 220, thereby greatly reducing the risk of incomplete resin plugging due to excessively fast resin flow, avoiding the formation of plugging holes and plugging depressions in the plated hole 220, and improving the plugging quality.

[0040] S5: Curing, baking the substrate 20 filled with resin to cure the resin, grinding the resin and performing post-processing, which includes but is not limited to outer layer circuit production, solder mask, character, surface treatment, molding, electrical testing and packaging.

[0041] Optionally, the cross-sectional shape of the mother hole 210 is circular.

[0042] See also Figures 2 to 4 In some embodiments, the hole wall of the plated hole 220 between the first hole opening 211 and the predetermined position is a convex arc surface.

[0043] Optionally, the flow of the resin can be appropriately slowed down by the convex arc surface of the plated hole 220 wall, thereby improving the fullness of the plated hole 220 plugging.

[0044] See also Figures 2 to 4 In some embodiments, the mother hole 210 is a through hole and has a second opening 212 located on the second board surface 202, and the cross-sectional area of ​​the hole section of the plated hole 220 located between the second opening 212 and the predetermined position gradually decreases along the second direction, and the second direction points along the second board surface 202 to the first board surface 201.

[0045] Optionally, along the first direction, the cross-sectional area of ​​the plated hole 220 is first gradually reduced, and after reaching a predetermined position, the cross-sectional area of ​​the plated hole 220 is gradually expanded, thereby facilitating the reduction of the flow rate of the resin, thereby reducing the risk of incomplete resin plugging of the hole due to excessively fast resin flow.

[0046] See also Figures 2 to 4In some embodiments, the hole wall of the plated hole 220 between the second hole opening 212 and the predetermined position is a convex arc surface.

[0047] Optionally, the hole wall of the plated hole 220 is a convex arc surface as a whole, that is, the intersection line of the longitudinal section along the hole depth direction and the hole wall of the plated hole 220 is an arc, which is beneficial to reduce the flow rate of the resin.

[0048] See also Figures 2 to 4 In some embodiments, during the electroplating step, a pulse electroplating method is used to electroplate the metal material on the hole wall of the mother hole 210 .

[0049] Optionally, in the present application, the forward and reverse pulse waveform current is set to 1:3 to 1:4, and the time ratio is set to 60:3 to 120:6 to increase the effect of the reverse pulse current and increase the thickness of the copper layer at the middle position of the plated hole 220. This is because, during the pulse electroplating process, the higher the reverse current ratio and the longer the reverse electroplating time, the thicker the copper layer at the middle position of the plated hole 220, ultimately achieving the effect of thickening the copper thickness in the middle position of the plated hole 220 and forming an "arc-shaped" hole wall.

[0050] Optionally, the electroplating current density and the electroplating time can be set according to actual requirements. In this example, the minimum hole copper thickness requirement is 20 μm, the current density is set to 18 ASF, and the electroplating time is 60 min.

[0051] See also Figures 2 to 4 In some embodiments, the mother hole 210 is a through hole, the diameter of the mother hole 210 is greater than 0 and less than or equal to 0.25 mm, or the ratio of the hole depth to the hole diameter of the mother hole 210 is greater than or equal to 8:1; for example, the hole diameter of the mother hole 210 can be 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, and the ratio of the hole depth to the hole diameter of the mother hole 210 can be 8:1, 9:1, 10:1, 11:1, 12:1, etc. There is no limitation here, and it can be selected according to actual conditions.

[0052] See also Figures 5 and 6 , the plugging step includes:

[0053] S41: injecting the fluid material into the plated hole 220 at the first opening 211 to fill a portion of the plated hole 220, and filling the fluid material along the first direction to a predetermined position of the plated hole 220; it can be understood that the first board surface 201 is arranged upward, so that the resin material first fills the upper end portion of the plated hole 220;

[0054] S42: Flip the substrate 20 180 degrees, set the second orifice 212 upward, and then inject the fluid material into the plated hole 220 at the second orifice 212 to fill another part of the plated hole 220. It can be filled along the second direction to the predetermined position of the plated hole 220, thereby completing the entire plugging process of the plated hole 220.

[0055] See also Figures 5 and 6 In some embodiments, a metal sheet 310 and an air guide pad 320 are prepared, the air guide pad 320 is located below the metal sheet 310, the two side surfaces of the substrate 20 are respectively connected to the metal sheet 310 and the air guide pad 320, the metal sheet 310 is provided with a first avoidance hole 301 at a position corresponding to the mother hole 210, and the air guide pad 320 is provided with a second avoidance hole 302 at a position corresponding to the mother hole 210. Optionally, the metal sheet 310 may be made of aluminum. Optionally, in this example, the diameter of the mother hole 210 is 0.25 mm, the plate thickness is 3.0 mm, the ratio of the hole depth to the hole diameter of the mother hole 210 is 12:1 (aspect ratio), the substrate 20 to be plugged is taken out from the constant temperature oven, the substrate 20 is positioned and fixed on the plugging machine table, the metal sheet 310 and the air guide pad 320 are respectively connected to the first plate surface 201 and the second plate surface 202, the first avoidance hole 301 and the second avoidance hole 302 correspond to the first orifice 211 and the second orifice 212 respectively.

[0056] See also Figures 5 and 6 When plugging the hole, firstly, vacuum resin plugging is performed from the first hole 211 of the first board surface 201, and then the substrate 20 is turned over so that the second board surface 202 faces upward and the first board surface 201 faces downward, and then vacuum resin plugging is performed from the second hole 212.

[0057] See also Figures 5 and 6 It is understandable that after the base plate 20 is turned over 180 degrees, the metal sheet 310 and the air guide pad 320 can be replaced, that is, a new metal sheet 310 and air guide pad 320 are used, and the metal sheet 310 and the air guide pad 320 are respectively connected to the second board surface 202 and the first board surface 201. Of course, if the aperture of the second avoidance hole 302 on the air guide pad 320 is larger than the aperture of the mother hole 210, the air guide pad 320 does not need to be replaced.

[0058] It can be understood that the metal sheet 310 is connected to the first board surface 201, and a first avoidance hole 301 is opened at the position of the metal sheet 310 corresponding to the mother hole 210. The first avoidance hole 301 is a straight through hole and its aperture is larger than the aperture of the plated hole 220 at the first hole opening 211. When the plated hole 220 is plugged with resin, the resin can enter the plated hole 220 from the first avoidance hole 301, ensuring that the plated hole 220 is plugged full and preventing excess resin from overflowing and adhering to other positions of the substrate 20, making it difficult to remove.

[0059] It is understandable that the second avoidance hole 302 can be used to discharge the gas in the plated hole 220, that is, through the air guide pad 320 disposed under the substrate, when the resin plugging is performed, the gas in the plated hole 220 can be discharged from the plated hole 220 in time through the second avoidance hole 302, so that the resin plugging of the plated hole 220 is fuller and has no depression. Optionally, both sides of the plugging are processed by plugging the holes with a metal sheet 310, and the aperture of the first avoidance hole 301 on the metal sheet 310 is 0.05mm larger than the aperture of the mother hole 210 on one side, that is, when the first avoidance hole 301 and the mother hole 210 are both circular holes, the radius of the first avoidance hole 301 is 0.05mm larger than the radius of the mother hole 210.

[0060] See also Figures 5 and 6 In some embodiments, the substrate is heated before the hole plugging step, which includes the following steps:

[0061] S31: Heat the electroplated substrate 20 to a predetermined temperature and keep it warm; the predetermined temperature ranges from 30 to 40 degrees Celsius. In the present application, the predetermined temperature is 35 degrees Celsius. In other embodiments, the predetermined temperature may also be 30 degrees Celsius, 31 degrees Celsius, 36 degrees Celsius, 37 degrees Celsius, 39 degrees Celsius, or 40 degrees Celsius. There is no limitation here and you can choose according to actual conditions.

[0062] S32: Place the substrate 20 in a vacuum environment, such as placing the substrate 20 in a vacuum resin plugging machine, so that the vacuum resin plugging machine can be used to perform plugging operations on the substrate 20. Before plugging, the vacuum resin plugging machine needs to evacuate the air inside the vacuum resin plugging machine so that the vacuum degree inside the vacuum resin plugging machine is less than or equal to 120Pa. When plugging, the angle of the scraper of the vacuum resin plugging machine is controlled at 10±5°, and the plugging speed is controlled at 50±10mm / s.

[0063] Optionally, the substrate 20 is vertically inserted into a special partition rack and placed in a cabinet constant temperature oven for baking. The baking temperature setting range can be 30 to 40 degrees Celsius. After the substrate 20 is heated to the set temperature, the oven automatically maintains a constant temperature state.

[0064] To prevent the substrate 20 from being exposed to room temperature for a long time after being taken out of the oven and being cooled, which may affect the plugging effect, only one rack of boards can be taken out for horizontal vacuum resin plugging each time plugging is performed, and the vacuum plugging of the entire rack of boards must be completed before another rack of boards can be taken out for processing. Each rack of boards includes multiple substrates 20.

[0065] After the substrate 20 is heated to 35 degrees Celsius, during the plugging process, the resin can enter the plated hole 220, and the viscosity of the resin can be reduced to about 32Pa.s (the resin viscosity is controlled at 35±5Pa.s, and the resin viscosity is about 37Pa.s at room temperature of 25 degrees Celsius). The appropriate reduction in resin viscosity can accelerate the flow of the resin, which is beneficial to resin filling.

[0066] When the temperature exceeds 40 degrees Celsius and is between the glass transition temperature (Tg) of the resin, the resin viscosity will drop to below 30 Pa.s. If the viscosity is too low, the resin will flow too fast, and the resin will be seriously lost during the plugging process. The resin will gather less in the plated hole 220, which can easily cause the resin plugging hole to be concave or void. Therefore, when the substrate 20 is at 30-40 degrees Celsius, the resin viscosity can be reduced to a "suitable" viscosity, which can improve the fluidity of the resin while ensuring that the resin will not be lost due to too low viscosity, thereby improving the fullness of the resin plugging hole. Adding a baking plate process before resin plugging can appropriately reduce the resin viscosity, which is beneficial to the filling of the through hole with resin during the resin plugging process.

[0067] The present invention also provides a circuit board, which is processed by plugging holes using the above-mentioned plugging method.

[0068] The above are only optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A plugging method, characterized in that: The steps include: Prepare a substrate, wherein the substrate has a first surface and a second surface disposed opposite to the first surface; Drilling, laying the substrate flat, and drilling a mother hole on the first board surface along a first direction, wherein the mother hole has a first opening located on the first board surface, and the first direction points along the first board surface to the second board surface; Electroplating, electroplating metal material on the hole wall of the mother hole to form a plated hole, wherein a predetermined position is provided on the hole wall of the plated hole; the cross-sectional area of ​​the hole section of the plated hole between the first hole opening and the predetermined position gradually decreases along the first direction; The plugging process injects the fluid material into the plated hole along the hole wall of the plated hole at the first hole opening.

2. The plugging method according to claim 1, characterized in that: The hole wall of the plated hole between the first hole opening and the predetermined position is a convex arc surface.

3. The plugging method according to claim 1, characterized in that: The mother hole is a through hole having a second opening located on the second board surface, and the cross-sectional area of ​​the hole section of the plated hole located between the second opening and the predetermined position gradually decreases along a second direction, and the second direction points to the first board surface along the second board surface.

4. The plugging method according to claim 3, characterized in that: The hole wall of the plated hole between the second hole opening and the predetermined position is a convex arc surface.

5. The plugging method according to claim 3, characterized in that: The mother hole is a straight through hole, the diameter of the mother hole is greater than 0 and less than or equal to 0.25 mm, or the ratio of the hole depth to the hole diameter of the mother hole is greater than or equal to 8:1; the plugging step includes: S41: injecting the fluid material into the plated hole at the first opening to fill a portion of the plated hole; S42: Turn the substrate 180 degrees, and inject the fluid material into the plated hole at the second opening to fill another portion of the plated hole.

6. The plugging method according to any one of claims 1 to 5, characterized in that: In the electroplating step, a pulse electroplating method is used to electroplate the metal material on the hole wall of the mother hole.

7. The plugging method according to any one of claims 1 to 5, characterized in that: Before the plugging step, the substrate after the electroplating step is heated to a predetermined temperature and kept warm.

8. The plugging method according to any one of claims 1 to 5, characterized in that: The plugging method further includes curing, wherein the substrate filled with the fluid material is baked to cure the fluid material.

9. The plugging method according to any one of claims 1 to 5, characterized in that: Prepare a metal sheet and an air guide pad, the air guide pad is located below the metal sheet, the two side surfaces of the substrate are respectively connected to the metal sheet and the air guide pad, the metal sheet is provided with a first avoidance hole at a position corresponding to the mother hole, and the air guide pad is provided with a second avoidance hole at a position corresponding to the mother hole.

10. A circuit board, characterized in that: The circuit board is processed by plugging holes using the plugging method described in any one of claims 1-9.

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