A method for filling vias in PCB board through-hole electroplating

Abstract

The present invention discloses a method for filling vias in PCB boards by electroplating, which includes the following steps: manufacturing vias in single-sided PCB boards, laminating multi-layer PCB boards, performing primary electroplating, filling a resin layer in the sunken holes of the primary electroplating, manufacturing a plurality of slot holes on the surface of the filled resin, and performing secondary electroplating, so as to conduct and connect the copper layer on the surface of the secondary electroplating, the copper layer on the surface of the primary electroplating, and the copper layer of the trapezoidal via, thereby effectively improving the transitional contact force between the copper layer of the trapezoidal via and the copper layer on the surface of the multi-layer PCB board, and solving the problem that the transitional contact between the copper layer of the cylindrical via and the copper layer on the surface is disconnected due to excessive welding temperature, resulting in conduction failure.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB manufacturing, and particularly relates to a method for electroplating and filling vias on a PCB board. Background Art

[0002] With technological innovation, electronic products tend to develop towards miniaturization, lightweight, multi-functionality, and high reliability, enabling the core carrier of electronic products, the multi-layer PCB board, to continuously develop towards a higher and more dense layout. The conduction of fine lines and micro-vias on the multi-layer PCB board is one of the effective solutions for the high density of printed circuit boards. Therefore, the electroplating and filling technology for micro-vias has become a key technology for manufacturing multi-layer PCB boards, enabling the electroplated copper layer and electrical interconnection of micro-vias to be completed in one step, greatly shortening the production cycle of multi-layer PCB boards. At the same time, it can significantly improve the electrical interconnection reliability and packaging density of multi-layer PCB boards. In addition, it can also improve the electrical conductivity, heat conductivity, and mechanical properties of multi-layer PCB boards to meet the development requirements of multi-layer PCB boards.

[0003] When manufacturing a multi-layer PCB board, as Figure 1 shown, multiple single-layer PCB boards 10 are initially laminated into a multi-layer PCB board. The multi-layer PCB board can be drilled once to obtain cylindrical vias 20a. Drilling the multi-layer PCB board in one step saves a certain amount of operation time. At the same time, in order to achieve the welding density and welding reliability of the solder layer on the board surface, it is necessary to perform electroplating and filling treatment on the cylindrical vias 20a.

[0004] Traditional electroplating and filling treatment method: electroplating a copper layer to metallize the cylindrical vias 20a, and filling the entire cylindrical vias 20a with the electroplated copper layer to make it conductive. For example, the prior art with the publication number CN111575752B discloses "a method for electroplating and manufacturing deep micro-vias in a PCB", which uses a linear gantry electroplating production line for full-board electroplating. Utilizing the characteristic that the electroplating solution applicable to this production line has good via penetration ability, it achieves the effect of simultaneously electroplating through-holes and blind vias on the board. The deep plating ability of blind vias is 82%, and the deep plating ability of through-holes is 65%. When filling the cylindrical vias 20a using the above method for electroplating and manufacturing deep micro-vias in a PCB, the obtained multi-layer PCB board is as Figure 2As shown, electroplating treatment is carried out to continuously deposit and fill the cylindrical through-hole copper layer 30a in the cylindrical through-hole 20a. The upper and lower plate surfaces of the multi-layer PCB board are continuously deposited with the board surface copper layer 40a that is conductively connected in transition with the cylindrical through-hole copper layer 30a. During the printing and wiring process of the board surface copper layer 40a, the contact thickness between the board surface copper layer 40a and the cylindrical through-hole copper layer 30a at the edge of the opening end of the cylindrical through-hole 20a is relatively thin, and it is easy to have defects such as incomplete filling of the depression. When welding electronic devices near the position of the cylindrical through-hole 20a, due to the too high welding temperature, the transitional contact force between the board surface copper layer 40a and the cylindrical through-hole copper layer 30a at the edge of the opening end of the cylindrical through-hole 20a is insufficient, and it is easy to occur the situation of conduction failure; in addition, when the manufactured multi-layer PCB board is collided, it is easy to cause the cylindrical through-hole copper layer 30a in the cylindrical through-hole 20a to collide and damage at the transitional connection position with the board surface copper layer 40a, which not only leads to the failure of the conductive connection, but also the cylindrical through-hole copper layer 30a in the cylindrical through-hole 20a is easy to fall off. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for electroplating and filling holes in PCB board through-holes, which is used to solve the defects caused by insufficient transitional contact force between the electroplated cylindrical through-hole copper layer in the cylindrical through-hole and the board surface copper layer.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for electroplating and filling holes in PCB board through-holes includes the following steps:

[0008] S1. Making through-holes in a single-layer PCB board, and the through-holes are trapezoidal through-holes with an inverted trapezoid shape;

[0009] S2. Pressing multi-layer PCB boards, pressing at least two of the single-layer PCB boards to make a multi-layer PCB board, and the adjacent upper and lower trapezoidal through-holes are stacked and connected;

[0010] S3. Electroplating the stacked connected through-holes in the multi-layer PCB board once until a primary electroplated board surface copper layer and depression holes are deposited on the upper and lower board surfaces, so that the stacked connected through-holes are filled with trapezoidal through-hole copper layers, and depression holes are formed at the transitional positions between the trapezoidal through-hole copper layers and the primary electroplated board surface copper layer;

[0011] S4. Filling the depression holes in the multi-layer PCB board with a resin layer once, so that the depression holes are filled with resin;

[0012] S5. Making a plurality of slot holes on the surface of the filled resin layer, and the slot holes are drilled along the depth direction of the filled resin layer;

[0013] S6. Conducting secondary electroplating treatment on the multi-layer PCB board until a secondary electroplated board surface copper layer is deposited in the primary electroplated board surface copper layer and the slot holes.

[0014] As a further solution of the present invention: a step S10 is provided between the step S1 and the step S2, and the step S10 is to perform reaming treatment on the upper and lower opening ends of the through hole.

[0015] As a further solution of the present invention: the reaming of the upper opening end of the through hole is an upper reaming in an inverted trapezoidal shape, and the reaming of the lower opening end is a lower reaming in a trapezoidal shape.

[0016] As a further solution of the present invention: the plurality of slot holes include a core hole one and a side hole two. The core hole one drills inward from the end face of the filled resin layer, and the side hole two drills along the edge end face of the filled resin layer.

[0017] As a further solution of the present invention: when performing primary electroplating on the multi-layer PCB board in the step S3, the electroplating solution is pre-treated with spiral turbulent flow from bottom to top in the stacked through holes.

[0018] As a further solution of the present invention: after the primary electroplating of the multi-layer PCB board in the step S3 is completed, the thickness of the copper layer on the surface of the primary electroplating is 10-15 μm, and the depth of the concave hole is 20-30 μm.

[0019] As a further solution of the present invention: after the filled resin layer is filled in the concave hole in the step S4, the surface of the filled resin layer is flush with the surface of the copper layer on the primary electroplating board surface.

[0020] As a further solution of the present invention: when performing secondary electroplating on the multi-layer PCB board in the step S6, the slot holes are pre-treated with vacuum pumping.

[0021] As a further solution of the present invention: after the secondary electroplating of the multi-layer PCB board in the step S6 is completed, the thickness of the copper layer on the surface of the secondary electroplating is 8-12 μm.

[0022] Advantages of the present invention:

[0023] (1) By pre-making through holes in a single-layer PCB board and then laminating it into a multi-layer PCB board, at the lamination surface position of adjacent single-layer PCB boards, the lower inverted trapezoidal through hole and the upper inverted trapezoidal through hole are variably diameter-connected to meet the staggered attachment and contact of the electroplated copper layers, which helps to improve the adhesion of the copper layer in the trapezoidal through hole in the stacked through holes, thereby avoiding the situation of collision and detachment;

[0024] (2) The multi-layer PCB board is subjected to one-time electroplating treatment until a copper layer is deposited on the upper and lower board surfaces and sunken holes are formed. The filling resin layer can be easily filled in the sunken holes to solve the defect of sunken holes generated during one-time electroplating. The filling resin layer drills into the slot holes, and then a secondary electroplating treatment is carried out. The copper layer on the secondary electroplated board surface is embedded in the filling resin layer, and the thickness of the copper layer on the primary electroplated board surface is supplemented, so that the copper layer on the secondary electroplated board surface, the copper layer on the primary electroplated board surface, and the copper layer of the trapezoidal through hole are conductively connected, thereby effectively improving the transitional contact force between the copper layer of the trapezoidal through hole and the copper layer on the surface of the multi-layer PCB board, and solving the problem that the conductive failure occurs due to the disconnection of the transitional contact between the columnar through hole copper layer and the board surface copper layer caused by too high welding temperature;

[0025] (3) After the through holes are made on the single-layer PCB board, the upper and lower opening ends of the through holes are subjected to reaming treatment. When the multi-layer PCB board is fabricated by pressing, the upper and lower board surfaces of the multi-layer PCB board and the stacked through holes are transitioned through reaming, so that the copper layer on the primary electroplated board surface and the copper layer of the trapezoidal through hole are smoothly transitioned and deposited and connected. The thickness of the copper layer at the edge of the trapezoidal through hole connecting the primary electroplated board surface can be increased, and the transitional contact force between the trapezoidal through hole copper layer and the board surface copper layer can be initially enhanced;

[0026] (4) When the reamed through holes are used to fabricate the multi-layer PCB board by pressing, at the adjacent pressing interface positions, the inverted trapezoidal through holes on the lower side and the inverted trapezoidal through holes on the upper side with reaming are connected with variable diameters, further expanding the staggered attachment and contact space of the electroplated copper layer, strengthening and enhancing the adhesion of the trapezoidal through hole copper layer in the stacked through holes, thereby strengthening the anti-collision and anti-shedding performance of the trapezoidal through hole copper layer and ensuring the stability of the conductive connection between the trapezoidal through hole copper layer and the board surface copper layer. Description of the Drawings

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 It is a schematic diagram of a multi-layer PCB board of the PCB board through-hole electroplating and filling method in the prior art;

[0029] Figure 2 It is a schematic diagram of the electroplated copper layer of the multi-layer PCB board of the PCB board through-hole electroplating and filling method in the prior art;

[0030] Figure 3 It is a schematic diagram of the step flow of the PCB board through-hole electroplating and filling method in Embodiment 1 of the present invention;

[0031] Figure 4 It is a schematic diagram of the single-layer PCB board obtained in step s1 in Embodiment 1 of the present invention;

[0032] Figure 5 It is a schematic diagram of the multi-layer PCB board obtained in step s2 in Embodiment 1 of the present invention;

[0033] Figure 6It is a schematic diagram of a multi-layer PCB board manufactured in step S3 of Embodiment 1 of the present invention;

[0034] Figure 7 It is a schematic diagram of a multi-layer PCB board manufactured in step S4 of Embodiment 1 of the present invention;

[0035] Figure 8 It is a schematic diagram of a multi-layer PCB board manufactured in step S5 of Embodiment 1 of the present invention;

[0036] Figure 9 It is a schematic diagram of a multi-layer PCB board manufactured in step S6 of Embodiment 1 of the present invention;

[0037] Figure 10 It is a schematic diagram of a single-layer PCB board manufactured in step S10 of Embodiment 2 of the present invention.

[0038] In the figure: 10, single-layer PCB board; 20, inverted trapezoidal through-hole; 21, upper enlarged hole; 22, lower enlarged hole; 20a, cylindrical through-hole; 30, trapezoidal through-hole copper layer; 30a, cylindrical through-hole copper layer; 40, primary electroplated surface copper layer; 40a, surface copper layer; 50, recessed hole; 60, filled resin layer; 61, core hole one; 62, edge hole two; 70, secondary electroplated surface copper layer. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] In the description of the present invention, it should be understood that the terms indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention; in the description of the present invention, the meaning of "a plurality" and "several" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0041] Embodiment 1

[0042] Please refer to Figure 3 As shown, the present invention is a method for electroplating and filling through-holes of a PCB board, including the following steps:

[0043] S1, as Figure 4As shown, a through hole is made in a single-layer PCB board 10, and the through hole is an inverted trapezoidal through hole 20. The through hole is positioned and made according to the circuit pattern of the single-layer PCB board 10. The through hole position is positioned and made by using a drill bit adapted to the inverted trapezoidal through hole 20 or laser etching to penetrate the single-layer PCB board 10. The formed inverted trapezoidal through hole 20 has an inclined hole wall, which can improve the adhesion of the chemical electroplated copper layer, and is conducive to the exchange of the electroplated copper liquid in the inverted trapezoidal through hole 20, so as to facilitate the filling and compaction of the inverted trapezoidal through hole 20 in the later stage.

[0044] S2, such as Figure 5 As shown, the multi-layer PCB board is pressed together, at least two single-layer PCB boards 10 are pressed together to form a multi-layer PCB board, and the upper and lower adjacent inverted trapezoidal through holes 20 are superimposed and connected. The alignment degree is determined by the same central axis of the inverted trapezoidal through holes 20 that need to be connected on the single-layer PCB board 10. During pre-stack, the alignment degree between adjacent single-layer PCB boards 10 is detected by X-Ray. After the alignment degree meets the requirement, pressing is started. Pressing makes the multi-layer PCB board have overlapping and connected holes. At the pressing surface position of the adjacent single-layer PCB board 10, the lower inverted trapezoidal through hole 20 is connected with the upper inverted trapezoidal through hole 20 with a reduced diameter to meet the staggered attachment contact of the electroplated copper layer, which helps to improve the adhesion of the trapezoidal through hole copper layer 30 in the overlapping and connected hole, thereby avoiding collision and falling off.

[0045] S3, such as Figure 6 As shown, the multi-layer PCB board is electroplated with stacked connecting holes once until the first electroplated board surface copper layer 40 and the recessed hole 50 are deposited on the upper and lower board surfaces, so that the stacked connecting holes are filled with the trapezoidal through-hole copper layer 30, and the recessed hole 50 is formed at the transition position between the trapezoidal through-hole copper layer 30 and the first electroplated board surface copper layer 40, so that the first electroplated board surface copper layer 40 and the trapezoidal through-hole copper layer 30 are conductively connected.

[0046] In this step, when the multi-layer PCB board is electroplated once, the electroplating solution is preliminarily subjected to a spiral turbulence treatment from bottom to top in the stacked communicating holes, so that the residual bubbles in the stacked communicating holes are discharged with the spirally floating electroplating solution, thereby solving the bubble cavity defects caused by the copper layer electroplating process; when the stacked communicating holes are electroplated, copper sulfate with a concentration of 180-220g / L, sulfuric acid with a concentration of 50-60g / L and an additive with a current density of 1.1-1.6A / dm are used, and the electroplating treatment is performed for 50min at a current density of 1.1-1.6A / dm. The thickness of the copper layer 40 formed by electroplating once on the electroplated board surface is 10-15μm, and the hole depth of the recessed hole 50 is 20-30μm. The formation of the recessed hole 50 is due to the exchange and transformation of the potion at the opening end of the stacked communicating hole, which is easy to occur when the electroplating is not complete.

[0047] S4, such as Figure 7As shown, a resin layer 60 is filled in the recessed holes 50 of the multi-layer PCB board during the first electroplating, so that the recessed holes 50 are filled with resin. A vacuum plug hole machine is used to fill the recessed holes 50 with resin, and the air in the recessed holes 50 is extracted in advance before resin filling and plugging to avoid the problem that the filled resin and the electroplated layer of the same layer are not tightly attached. After the resin layer 60 is filled in the recessed holes 50, the surface of the resin layer 60 is flush with the surface of the copper layer 40 on the first electroplated board surface. A sander can be used to grind the resin protruding from the surface of the copper layer 40 on the first electroplated board surface of the filled resin layer 60 to ensure that the thickness of the copper layer deposited on the surface of the copper layer 40 on the first electroplated board surface and the filled resin layer 60 is the same during the second electroplating.

[0048] S5. As Figure 8 shown, a plurality of slot holes are made on the surface of the filled resin layer 60. The slot holes are drilled along the depth direction of the filled resin layer 60. The plurality of slot holes include a core hole one 61 and a side hole two 62. The core hole one 61 is drilled from the end surface of the filled resin layer 60 into the interior, and the side hole two 62 is drilled along the edge end surface of the filled resin layer 60. The depths of the core hole one 61 and the side hole two 62 do not exceed the thickness of the filled resin layer 60.

[0049] S6. As Figure 9 shown, the multi-layer PCB board is subjected to a second electroplating treatment until a copper layer 70 on the second electroplated board surface is deposited on the copper layer 40 on the first electroplated board surface and in the slot holes.

[0050] In this step, during the second electroplating of the multi-layer PCB board, the slot holes are pre-vacuumed to evacuate the residual bubbles in the slot holes, solving the problem of bubble void defects caused during the electroplating of the copper layer. The second electroplating uses vertical copper deposition, and the copper layer 40 on the first electroplated board surface and the filled resin layer 60 are subjected to vertical copper deposition treatment, so that while the electroplated copper layer evenly fills the slot holes, a copper layer 70 on the second electroplated board surface is deposited on the surfaces of the copper layer 40 on the first electroplated board surface and the filled resin layer 60. The thickness of the copper layer 70 on the second electroplated board surface is 8 - 12 μm.

[0051] In this step, for the multi-layer PCB board obtained by the second electroplating, the copper layer 70 on the second electroplated board surface is embedded in the filled resin layer 60, and the thickness of the copper layer 40 on the first electroplated board surface is supplemented, so that the copper layer 70 on the second electroplated board surface, the copper layer 40 on the first electroplated board surface, and the trapezoidal through-hole copper layer 30 are conductively connected, thereby effectively improving the transitional contact force between the trapezoidal through-hole copper layer 30 and the copper layer on the surface of the multi-layer PCB board, and solving the problem that the transitional contact between the cylindrical through-hole copper layer 30a and the copper layer on the board surface is disconnected due to too high welding temperature, resulting in conduction failure.

[0052] Example 2

[0053] As Figure 10As shown, based on Embodiment 1, step S10 is set between step S1 and step S2. Step S10 is the reaming treatment for the upper and lower open ends of the through hole. The upper open end of the through hole is reamed into an upper reamed hole 21 with an inverted trapezoidal shape, and the lower open end is reamed into a lower reamed hole 22 with a trapezoidal shape. When laminating to obtain a multi-layer PCB board, the upper and lower board surfaces of the multi-layer PCB board and the stacked through holes are transitioned through reaming, so that the copper layer 40 on the electroplated board surface and the trapezoidal through-hole copper layer 30 are smoothly transitioned and deposited and connected, which can increase the thickness of the trapezoidal through-hole copper layer 30 at the edge connecting the copper layer 40 on the electroplated board surface; at the adjacent lamination interface position of the multi-layer PCB board, the inverted trapezoidal through holes 20 with lower reaming and the inverted trapezoidal through holes 20 with upper reaming are connected with variable diameters, further expanding the staggered attachment and contact space of the electroplated copper layers, strengthening and enhancing the adhesion of the trapezoidal through-hole copper layer 30 in the stacked through holes, thereby strengthening the anti-collision and anti-shedding performance of the trapezoidal through-hole copper layer 30 and ensuring the conduction connection stability between the trapezoidal through-hole copper layer 30 and the board surface copper layer.

[0054] The above has described in detail an embodiment of the present invention, but the content described is only the preferred embodiment of the present invention and cannot be considered as used to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for filling vias in a PCB board by electroplating, characterized in that, Including the following steps: S1. Make a through hole in a single-layer PCB board (10), and the through hole is an inverted trapezoidal through hole (20); S2. Press multiple-layer PCB boards, press at least two single-layer PCB boards (10) to make a multiple-layer PCB board, and the adjacent inverted trapezoidal through holes (20) up and down are stacked and connected; S3. Electroplate the stacked through holes of the multiple-layer PCB board once until a primary electroplated copper layer on the board surface (40) and a recessed hole (50) are deposited on the upper and lower board surfaces, so that the stacked through holes are filled with a trapezoidal through hole copper layer (30), and a recessed hole (50) is formed at the transition position between the trapezoidal through hole copper layer (30) and the primary electroplated copper layer on the board surface (40); S4. Fill the recessed hole (50) in the multiple-layer PCB board with a resin layer (60) during the first electroplating, so that the recessed hole (50) is filled with resin; S5. Make a plurality of slot holes on the surface of the filled resin layer (60), and the slot holes are drilled along the depth direction of the filled resin layer (60); S6. Perform secondary electroplating treatment on the multiple-layer PCB board until a secondary electroplated copper layer on the board surface (70) is deposited on the primary electroplated copper layer on the board surface (40) and in the slot holes; Wherein, step S10 is set between step S1 and step S2, and step S10 is the reaming treatment of the upper and lower open ends of the through hole. The upper open end of the through hole is reamed into an upper reamed hole (21) in an inverted trapezoidal shape, and the lower open end is reamed into a lower reamed hole (22) in a trapezoidal shape.

2. A method for filling vias in PCB board through-hole electroplating, characterized in that, The plurality of slot holes include a core hole one (61) and a side hole two (62). The core hole one (61) is drilled from the end surface of the filled resin layer (60) towards the inside, and the side hole two (62) is drilled along the edge end surface of the filled resin layer (60).

3. A method for filling vias in PCB board through-hole electroplating, characterized in that, When the multiple-layer PCB board is electroplated for the first time in step S3, the electroplating solution is pre-treated with spiral turbulent flow from bottom to top in the stacked through holes.

4. A method for filling vias in PCB board through-hole electroplating, characterized in that, After the first electroplating of the multiple-layer PCB board in step S3 is completed, the thickness of the primary electroplated copper layer on the board surface (40) is 10 - 15 μm, and the hole depth of the recessed hole (50) is 20 - 30 μm.

5. A method for filling vias in PCB board through-hole electroplating, characterized in that, After the recessed hole (50) in step S4 is filled with the resin layer (60), the surface of the filled resin layer (60) is flush with the surface of the primary electroplated copper layer on the board surface (40).

6. A method for filling vias in a PCB board through-hole plating, characterized in that, When the multiple-layer PCB board is electroplated for the second time in step S6, the slot holes are pre-treated with vacuum pumping.

7. A method for filling vias in PCB board through-hole electroplating, characterized in that, After the second electroplating of the multiple-layer PCB board in step S6 is completed, the thickness of the secondary electroplated copper layer on the board surface (70) is 8 - 12 μm.

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