Preparation method of thick copper circuit board

Abstract

The invention discloses a thick copper circuit board preparation method, and relates to the technical field of printed circuit board processing, and the method comprises the steps: S1, board selection: selecting a board with 18 [mu] m base material copper; s2, drilling is conducted; s3, copper deposition; s4, first-time whole board electroplating, wherein the copper thickness of the surface of the board is increased by 5-10 microns, and at the moment, the copper thickness of the base material and the copper thickness of primary electroplating are 20-25 microns; s5, pattern transfer, wherein a 3mil dry film is used for pasting a film on the plate, and a pattern is formed through exposure and development; s6, second-time whole board electroplating, wherein the copper thickness on the circuit of the pattern is increased within 70 microns, and at the moment, the base material copper, the electroplating primary copper and the electroplating secondary copper are 52.5-87.5 microns; s7, gold electroplating is conducted, specifically, nickel and gold electroplating treatment is conducted; s8, removing the film: removing the dry film; and S9, etching. The full-board gold plating technology can also be used for producing circuit boards with the copper thickness larger than 52.5 micrometers and smaller than or equal to 87.5 micrometers, and gold wires are not prone to being generated.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board processing, and in particular to a method for preparing a thick copper circuit board. Background Art

[0002] In current printed circuit boards, full-board gold plating is often used, and its purpose is to improve solderability and protect metal coatings. The full-board gold plating process is to perform gold plating after pattern transfer. The product belongs to overall conductive gold plating. The substrate copper and electroplated copper are used as the side etching amount of etching. The thicker the copper layer of the substrate copper and electroplated copper, the greater the side etching amount, and the suspended length of the gold layer will increase accordingly. The gold layer will collapse and fall off due to the influence of the suspension, so circuit boards with a copper thickness of 52.5μm < ≤ 87.5μm are prone to gold wire. At present, the full-board gold plating process is only produced for circuit boards with a copper thickness of ≤ 52.5μm. Summary of the invention

[0003] In order to solve the shortcomings of the prior art, the present invention provides a method for preparing a thick copper circuit board. The full-board gold plating process can be used to produce circuit boards with a copper thickness of 52.5 μm < ≤ 87.5 μm.

[0004] In order to achieve the purpose of the present invention, the following scheme is proposed: A method for preparing a thick copper circuit board comprises the following steps: S1. Board selection: Select a board with a base material copper of 18 μm; S2, drilling: drilling a hole of a preset diameter at a preset position; S3, copper deposition: deposit a layer of chemical copper in the hole wall; S4, the first full-board electroplating: increase the copper thickness on the board surface by 5μm-10μm, at which time the base copper + electroplated copper is 20μm-25μm; S5, Graphic transfer: Use 3mil dry film to laminate the board, and form the graphics through exposure and development; S6, Second full-board electroplating: The copper thickness on the patterned circuit is increased within 70μm, at this time the base copper + electroplated copper + electroplated copper is 52.5μm-87.5μm; S7, electroplating gold: electroplating nickel gold; S8, film stripping: remove the dry film; S9, etching.

[0005] The beneficial effects of the present invention are: 1. The present invention divides the copper electroplating into two steps. A thin copper layer is plated in the first full-board electroplating, and a thick copper layer is plated in the second full-board electroplating. The etching is for the copper below the dry film, which has a thickness of only 20μm-25μm, so it has little effect on the side etching amount. The present invention realizes that the full-board gold plating process can also be used to produce circuit boards with a copper thickness of 52.5μm < ≤ 87.5μm, and it is not easy to produce gold wires.

[0006] 2. Considering that the copper layer of the secondary copper electroplating is relatively thick, the present invention improves the film stripping step so as to more fully remove the dry film to avoid incomplete removal of the dry film, which affects the effect of subsequent etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A flow chart of a method for preparing a thick copper circuit board is shown; Figure 2 The schematic diagram of the structure of the plate obtained after gold electroplating is shown; Figure 3 A structural diagram of the clamping mechanism is shown; Figure 4 A diagram showing the connection relationship between the bracket, the fixture and the adjustment control; Figure 5 Showing a side perspective view of a first clamping plate and a second clamping plate; Figure 6 A side view of the adjustment control is shown; Figure 7 A structural diagram of a clamping mechanism having multiple sets of plates is shown; Figure 8 Shows the plate structure Figure 1 ; Fig. 9 Shows the plate structure Figure 2 ; Figure numerals: clamping mechanism-1, bracket-2, cross bar-21, cylindrical rod-22, clamp-3, first clamp plate-311, second clamp plate-312, guide rod-32, spring-33, baffle-34, slot-35, center rod-36, circular groove-37, adjustment control-4, handle-41, cam-42, first arc surface-421, first plane-422, second arc surface-423, second plane-424, third arc surface-425, third plane-426, limit plate-43, sleeve plate-5, sleeve hole-51, pull ring-52. DETAILED DESCRIPTION

[0008] like Figure 1 As shown, this embodiment provides a method for preparing a thick copper circuit board, comprising the following steps: S1. Board selection: Select a board with a base material copper of 18 μm; S2, drilling: drilling a hole of a preset diameter at a preset position; S3, copper deposition: deposit a layer of chemical copper in the hole wall to serve as the base for subsequent copper electroplating; S4, the first full-board electroplating: increase the copper thickness on the board surface by 5μm-10μm, at which time the base copper + electroplated copper is 20μm-25μm; S5, Graphic transfer: Use 3mil dry film to laminate the board, and form the graphics through exposure and development; S6, Second full-board electroplating: The copper thickness on the patterned circuit can be increased by up to 70μm, at which time the base copper + electroplated copper + electroplated copper is 52.5μm-87.5μm; S7, electroplating gold: electroplating nickel gold, the plate at this time is Figure 2 As shown; S8, film stripping: Use film stripping liquid to remove the dry film. The film stripping liquid is a conventional liquid, and its components will not be described in detail here; S9, Etching: Figure 2 In the process, the thickness of the substrate copper below the dry film + the electroplated copper is 20μm-25μm. This thickness is the etching part, so it has little effect on the side etching amount.

[0009] In the method provided in the above embodiment, the copper electroplating is divided into two steps. A thin layer of copper is plated during the first full-board electroplating, and a thick layer of copper is plated during the second full-board electroplating. The total copper thickness of the substrate copper + the first electroplated copper + the second electroplated copper is 52.5μm-87.5μm, and the etching is for the copper below the dry film, which has a thickness of only 20μm-25μm, so it has little effect on the side etching amount, and it is not easy to produce gold wires in the gold layer after etching.

[0010] If the dry film is not completely removed, it will affect the etching step. Considering that the copper layer of the secondary copper electroplating is thicker, in the stripping step, in order to more fully remove the dry film, this embodiment immerses the plate in the stripping liquid by vertical suspension, which is more conducive to the detachment of the dry film from the plate. Imagine that if the plate is horizontally immersed in the stripping liquid, part of the dry film may remain in the concave part on the top of the plate.

[0011] The film stripping steps of S8 of this embodiment are as follows: suspend a plurality of plates that have been electroplated with nickel and gold under the clamping mechanism 1, move the clamping mechanism 1 to the top of the film stripping pool by using a conveying track, and move the clamping mechanism 1 downward under the action of the lifting mechanism until the plates are immersed in the film stripping liquid.

[0012] The conveying track, lifting mechanism and film stripping tank are conventional technologies and will not be shown or described in detail. Figure 3 , Figure 4As shown, the clamping mechanism 1 includes a bracket 2, a plurality of clamps 3 and a plurality of adjustment controls 4. The bracket 2 includes two bases and two cross bars 21 and a columnar rod 22 arranged between the two bases. The three are parallel to each other. The columnar rod 22 is located on the outside of one of the cross bars 21, and the position of the columnar rod 22 is lower than the position of the cross bar 21. The plurality of clamps 3 are arranged in an array along the long axis direction of the two cross bars 21. The clamps 3 include a first clamping plate 311, a second clamping plate 312, a guide rod 32 and a spring 33. The guide rod 32 is arranged horizontally, and the two ends of the guide rod 32 are respectively fixedly connected to the two cross bars 21. The top of the first clamping plate 311 is fixedly connected to the guide rod 32, and the second clamping plate 312 is fixedly connected to the guide rod 32. The top of the plate 312 slides horizontally on the guide rod 32, and the two ends of the spring 33 are respectively connected to the inner wall of the first clamp 311 and the inner wall of the second clamp 312. A plurality of adjustment controls 4 are arranged in an array along the long axis direction of the cylindrical rod 22. One adjustment control 4 corresponds to one clamp 3. The adjustment control 4 is used to control the opening and closing of the corresponding clamp 3. The adjustment control 4 includes a handle 41, a cam 42 and two limit plates 43. The two limit plates 43 are coaxially fixed on the cylindrical rod 22. The cam 42 is rotatably matched with the cylindrical rod 22, and the cam 42 is located between the two limit plates 43. The handle 41 is fixed on the outer wall of the cam 42. When the cam 42 rotates, it can control the opening and closing of the corresponding clamp 3.

[0013] The structure of the cam 42 is as follows: Figure 4 , Figure 6 As shown, the side wall of the cam 42 includes a first arc surface 421, a first plane 422, a second arc surface 423, a second plane 424, a third arc surface 425 and a third plane 426 in sequence. The radius of the first arc surface 421 is equal to the radius of the third arc surface 425, and the radius of the first arc surface 421 is greater than the radius of the second arc surface 423. The second arc surface 423 is coaxial with the cylindrical rod 22. The handle 41 is arranged on the second plane 424. When the clamp 3 is in the open state, the first plane 422 is close to the outer wall of the second clamp plate 312.

[0014] In step S8, during the film removal step, the clamping mechanism 1 clamps the sheet in the following manner: S801, inserting the top of the plate between the first clamping plate 311 and the second clamping plate 312 of the plurality of clamps 3; S802, the staff pushes the multiple handles 41 upwards in sequence, gradually making the third plane 426 of the cam 42 close to the outer wall of the second clamping plate 312, and gradually moving the second clamping plate 312 toward the first clamping plate 311 during the rotation of the cam 42. When the third plane 426 is close to the outer wall of the second clamping plate 312, the first clamping plate 311 just clamps the plate.

[0015] Here, let us explain one thing. Assuming that the clamping mechanism 1 is provided with 15 clamps 3 in total, and 5 adjacent clamps 3 form a group for clamping one plate, then the clamping mechanism 1 can clamp 3 plates.

[0016] More specifically, when the top of the plate is inserted into the plurality of fixtures 3, in order to ensure that the plurality of plates are arranged neatly and at the same height, as Figure 4 , Figure 5 As shown, in this embodiment, a baffle 34 is provided on the inner wall of the first clamp plate 311, and the baffle 34 is located below the spring 33. The baffle 34 is used to stop the plate and position the plate. A slot 35 is provided at the corresponding position of the second clamp plate 312. When the second clamp plate 312 moves toward the first clamp plate 311, the slot 35 is used to accommodate the baffle 34. The baffle 34 is in the shape of a rectangular parallelepiped. When the baffle 34 is inserted into the slot 35, the baffle 34 can also guide the moving direction of the second clamp plate 312, thereby improving the stability of the second clamp plate 312.

[0017] More specifically, the thickness of the plate obtained after the gold plating is very thin, which means that when the first clamping plate 311 and the second clamping plate 312 clamp the plate, the distance between the first clamping plate 311 and the second clamping plate 312 is also very small, so the space for the spring 33 is limited. In order to solve this problem, the present embodiment adopts the following measures: Figure 5 As shown, a center rod 36 is provided on the inner wall of the first clamping plate 311, and a circular groove 37 is provided at a corresponding position of the second clamping plate 312. The spring 33 is located at the outer periphery of the center rod 36, and one end of the spring 33 is located in the circular groove 37, thereby expanding the space for the spring 33. In step S802, when the second clamping plate 312 moves toward the first clamping plate 311, the circular groove 37 is used to accommodate the center rod 36.

[0018] As mentioned above, each time a plate is clamped, multiple handles 41 need to be pushed upward in sequence. Similarly, when removing a plate, multiple handles 41 also need to be pushed downward in sequence. Therefore, the process of clamping or removing a plate is relatively cumbersome. In this embodiment, it is considered that a set plate 5 can be used to control multiple handles 41 at the same time. The specific implementation method is as follows: Figure 4 , Figure 7-Figure 9 As shown, the clamping mechanism 1 also includes a plurality of sleeve plates 5, a plurality of sleeve holes 51 are arrayed on one side of the sleeve plate 5, a pull ring 52 is provided on the other side of the sleeve plate 5, the plurality of sleeve holes 51 are used to match a plurality of adjacent handles 41, the outer diameter of the free end of the handle 41 is larger than the outer diameter of the fixed end thereof, the free end of the handle 41 refers to the end of the handle 41 away from the cam 42, an elastic layer is provided on the inner wall of the sleeve hole 51, the material of the elastic layer is rubber or foam glue, the elastic layer has two functions: one is to allow the handle 41 to be inserted into the corresponding sleeve hole 51 by squeezing the elastic layer to deform, and the second is that the elastic layer wraps the handle 41 to improve the connection stability between the handle 41 and the sleeve plate 5.

[0019] In order to further improve the stability of the sleeve 5, a first threaded hole is provided at the free end of the handle 41, and a plurality of second threaded holes are arrayed on one side of the sleeve 5 having a pull ring 52. The second threaded holes are connected to the corresponding sleeve holes 51 for installing screws. Note that it is not necessary to install screws in all the second threaded holes. One or two screws are sufficient to firmly connect the sleeve 5 and the handle 41.

[0020] The steps for installing the set plate 5 are before S801, and are as follows: S800, select a sleeve plate 5 of appropriate length according to the size of the plate, align the multiple sleeve holes 51 with the handles 41 of the multiple adjustment controls 4, and squeeze them hard to insert the handles 41 into the corresponding sleeve holes 51; then reinforce the sleeve plate 5 and the handles 41 with a number of screws; when the size of the plate increases, more clamps 3 may be required for clamping, which means that the number of handles 41 corresponding to one plate also increases. In this case, it is only necessary to replace the sleeve plate 5 with a larger length; S801, insert the top of the plate into the multiple clamps 3 corresponding to the set plate 5, ensuring that the top of the plate is close to the baffle 34; S802, push the pull ring 52 upward to cause multiple clamps 3 to close simultaneously, thereby clamping the plate.

[0021] In summary, the present embodiment realizes that the full-board gold plating process can also be used to produce circuit boards with a copper thickness of 52.5μm<copper thickness≤87.5μm, and gold wires are not easily generated; further, considering that the copper layer of the secondary copper electroplating is thicker, the present embodiment improves the film stripping step to more fully remove the dry film, so as to avoid incomplete removal of the dry film, which affects the effect of subsequent etching.

[0022] The above embodiments are only used to illustrate the technical ideas and features of the present invention, and are not intended to be the only or limit the present invention. It should be understood by those skilled in the art that various changes or equivalent substitutions made to the present invention without departing from the scope of the present invention all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a thick copper circuit board, characterized in that: The following steps are involved: S1. Board selection: Select a board with a base material copper of 18 μm; S2, drilling: drilling a hole of a preset diameter at a preset position; S3, copper deposition: deposit a layer of chemical copper in the hole wall; S4, the first full-board electroplating: increase the copper thickness on the board surface by 5μm-10μm, at which time the base copper + electroplated copper is 20μm-25μm; S5, Graphic transfer: Use 3mil dry film to laminate the board, and form the graphics through exposure and development; S6, Second full-board electroplating: The copper thickness on the patterned circuit is increased within 70μm, at this time the base copper + electroplated copper + electroplated copper is 52.5μm-87.5μm; S7, electroplating gold: electroplating nickel gold; S8, film stripping: remove the dry film; S9, etching.

2. The method for preparing a thick copper circuit board according to claim 1, characterized in that: S8, film stripping step: suspend a plurality of plates that have been electroplated with nickel and gold below the clamping mechanism (1), move the clamping mechanism (1) to the top of the film stripping pool by using a conveying track, and move the clamping mechanism (1) downward under the action of the lifting mechanism until the plates are immersed in the film stripping liquid.

3. The method for preparing a thick copper circuit board according to claim 2, characterized in that: The clamping mechanism (1) comprises a bracket (2), a plurality of clamps (3) and a plurality of adjustment controls (4); the bracket (2) comprises two cross bars (21) and a columnar bar (22), the three of which are parallel to each other; the plurality of clamps (3) are arranged in an array along the long axis of the cross bar (21); the clamps (3) comprise a first clamping plate (311), a second clamping plate (312), a guide rod (32) and a spring (33); the two ends of the guide rod (32) are respectively fixedly connected to the two cross bars (21); the top of the first clamping plate (311) is fixedly connected to the guide rod (32); the second clamping plate (312) is fixedly connected to the guide rod (32); and the spring (33) is provided at the bottom of the first clamping plate (311). 12) The top is horizontally slidably engaged with the guide rod (32), the two ends of the spring (33) are respectively connected to the inner wall of the first clamp (311) and the inner wall of the second clamp (312), a plurality of adjustment controls (4) are arranged in an array along the long axis of the columnar rod (22), one adjustment control (4) corresponds to one clamp (3), and the adjustment control (4) includes two limit plates (43) fixedly arranged on the columnar rod (22), a cam (42) rotatably engaged with the columnar rod (22) and located between the two limit plates (43), and a handle (41) fixedly arranged on the outer wall of the cam (42); In step S8, during the film removal step, the clamping mechanism (1) clamps the sheet in the following manner: S801, inserting the top of the plate between the first clamping plate (311) and the second clamping plate (312) of a plurality of clamps (3); S802, pushing the plurality of handles (41) upwards to cause the second clamping plate (312) to move toward the first clamping plate (311) until the plate is clamped.

4. The method for preparing a thick copper circuit board according to claim 3, characterized in that: A baffle (34) is provided on the inner wall of the first clamping plate (311), a slot (35) is provided at a corresponding position of the second clamping plate (312), and the baffle (34) is located below the spring (33); In step S801, the top of the plate is in close contact with the baffle (34); in step S802, when the second clamping plate (312) moves toward the first clamping plate (311), the slot (35) is used to accommodate the baffle (34).

5. The method for preparing a thick copper circuit board according to claim 4, characterized in that: A center rod (36) is provided on the inner wall of the first clamping plate (311), a circular groove (37) is provided at a corresponding position of the second clamping plate (312), the spring (33) is located on the outer periphery of the center rod (36), and one end of the spring (33) is located in the circular groove (37); In step S802, when the second clamping plate (312) moves toward the first clamping plate (311), the circular groove (37) is used to accommodate the central rod (36).

6. The method for preparing a thick copper circuit board according to claim 3, characterized in that: The side wall of the cam (42) includes a first arc surface (421), a first plane (422), a second arc surface (423), a second plane (424), a third arc surface (425) and a third plane (426) in sequence; the radius of the first arc surface (421) is equal to the radius of the third arc surface (425) and is greater than the radius of the second arc surface (423); the handle (41) is disposed on the second plane (424); when the clamp (3) is in an open state, the first plane (422) is in close contact with the outer wall of the second clamping plate (312); In step S802, the handle (41) is pushed upwards to gradually bring the third plane (426) into close contact with the outer wall of the second clamping plate (312), thereby clamping the plate.

7. The method for preparing a thick copper circuit board according to claim 3, characterized in that: The clamping mechanism (1) further comprises a plurality of sleeve plates (5), one side of the sleeve plates (5) being provided with a plurality of sleeve holes (51) in an array, and the other side being provided with a pull ring (52), the plurality of sleeve holes (51) being used to match a plurality of adjacent handles (41), the outer diameter of the free end of the handle (41) being greater than the outer diameter of the fixed end thereof, the inner wall of the sleeve hole (51) being provided with an elastic layer, the material of the elastic layer being selected from rubber or foam rubber, and being used to wrap the handle (41); S800, selecting a sleeve plate (5) of suitable length according to the size of the plate, aligning the plurality of sleeve holes (51) with the handles (41) of the plurality of adjustment controls (4), and squeezing them hard so that the handles (41) are inserted into the corresponding sleeve holes (51); S801, inserting the top of the plate into a plurality of fixtures (3) corresponding to the sleeve plate (5); S802, pushing the pull ring (52) upwards to cause the multiple clamps (3) to close simultaneously, thereby clamping the plate.

8. The method for preparing a thick copper circuit board according to claim 7, characterized in that: A first threaded hole is provided at the free end of the handle (41), and a plurality of second threaded holes are arranged in an array on one side of the sleeve plate (5) having the pull ring (52), wherein the second threaded holes are connected to the corresponding sleeve holes (51); In step S800, the cover plate (5) is firstly covered on the handles (41) of the plurality of adjustment controls (4), and then the cover plate (5) and the handles (41) are reinforced and connected by a plurality of screws.

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