TWI626867B - Method for surface plating without conducting wire and circuit board making by the same - Google Patents

Abstract

A wireless surface plating method includes the steps of: providing an initial circuit board, the initial circuit board comprising a substrate and two conductive circuit layers bonded to two opposite surfaces of the substrate, and each of the conductive circuits of the conductive circuit layer There is at least one gap between them, and the bottom surface of the gap is the surface of the substrate; a conductive polymer film is formed on the bottom surface of the gap, and the conductive lines on both sides of the gap are electrically connected by the conductive polymer film; Forming a photoresist layer on the surface of the conductive circuit layer and the conductive polymer film away from the substrate; forming at least one electroplating bath on the photoresist layer; electroplating a metal protective layer in the electroplating bath; removing the photoresist layer Removing the conductive polymer film. In addition, the present invention also provides a circuit board prepared by the above-mentioned method for electroplating a surface without wires.

Description

Wireless surface plating method and circuit board prepared by the method

The invention relates to a method for electroplating a surface without wires and a circuit board prepared by the method.

In recent years, with the trend of miniaturization and thinning of electronic products, it is required that the circuit boards used therein also have the characteristics of miniaturization and thinning. In order to meet the miniaturization and thinness of electronic products, the circuit boards of electronic products need to adopt a dense circuit design. However, in the manufacturing process of the circuit board, when the metal protective layer is plated on the conductive circuit layer, in order to pass the current required during plating to the circuit board, it is usually necessary to design a plated wire, and the plated wire after the metal protection layer is plated , Usually remain in the circuit board, so it will occupy the space of the circuit board and reduce the layout utilization of the circuit board.

In view of this, it is necessary to provide a new leadless surface plating method to solve the above problems.

In addition, it is necessary to provide a circuit board made by applying the above-mentioned non-lead surface plating method.

A wireless surface plating method includes the following steps:

Step S1: An initial circuit board is provided. The initial circuit board includes a substrate and two conductive circuit layers bonded to opposite surfaces of the substrate. The initial circuit board has a via hole, and the two conductive circuit layers are borrowed. Electrically connected by the vias, each conductive circuit layer is mainly formed of conductive circuits, and at least one gap is formed between the conductive circuits of each conductive circuit layer, and the bottom surface of the gap is the surface of the substrate;

Step S2: forming a conductive polymer film on the bottom surface of the gap, and the conductive lines on both sides of the gap are electrically connected by the conductive polymer film;

Step S3: forming a photoresist layer on the conductive circuit layer and the conductive polymer film away from the substrate surface;

Step S4: forming at least one plating bath on the photoresist layer;

Step S5: plating a metal protective layer in the plating tank;

Step S6: removing the photoresist layer to expose the surface of the conductive circuit layer covered by the photoresist layer, the surface of the conductive polymer film, and the surface of the metal protective layer;

Step S7: The conductive polymer film is removed, so that the surface of the substrate covered by the conductive polymer film, the sides of the gaps of the conductive circuit layer, and the surface of the metal protective layer are exposed.

A circuit board includes a substrate and two conductive circuit layers bonded to opposite surfaces of the substrate. Each conductive circuit layer is mainly formed of conductive circuits. There is at least one between the conductive circuits of each conductive circuit layer. A gap, the gap having a bottom surface and at least two side surfaces connected to the bottom surface, the bottom surface being the surface of the substrate, the circuit board further including at least a metal protective layer, the metal protective layer including a first portion and the first portion An extended second portion is bonded to a surface of the conductive circuit layer away from the substrate, the second portion is bonded to a side surface of the gap adjacent to the first portion, and the second portion is adjacent to a base There is a certain distance between the end of the material and the substrate.

The non-conductor surface plating method forms a conductive polymer film on a substrate of a conductive circuit layer exposed through a gap, and uses the conductive polymer film to achieve electroplating conduction. After the metal is formed by electroplating, the conductivity is high. The molecular membrane is removed. Compared with the conventional process of punching the electroplated lead when the electroplated lead is used to achieve electroplating continuity, and the electroplated lead is finally retained on the circuit board, the conductive polymer film of the present invention does not require the punching process to simplify the manufacturing process. And the conductive polymer film will eventually be removed from the circuit board to improve the space utilization of the circuit board. In addition, compared with the use of electroplated leads to achieve circuit conduction, the conductive polymer film of the present invention does not need to use a metal material for making electroplated leads and saves costs.

FIG. 1 is a schematic cross-sectional view of an initial circuit board according to a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of forming a conductive polymer film on the bottom of the gap of the initial circuit board shown in FIG. 1.

FIG. 3 is a schematic diagram of forming a photoresist layer on the surfaces of the conductive circuit layer and the conductive polymer film shown in FIG. 2.

FIG. 4 is a schematic diagram of forming a plating bath on the photoresist layer shown in FIG. 3.

FIG. 5 is a schematic diagram of a plating metal protective layer in the plating tank shown in FIG. 4.

FIG. 6 is a schematic diagram of removing the photoresist layer shown in FIG. 5.

FIG. 7 is a schematic diagram of a circuit board according to a preferred embodiment of the present invention.

Please refer to FIGS. 1 to 7 in combination. A preferred embodiment of the present invention provides a non-conductor surface plating method for a circuit board.

Step S1, referring to FIG. 1, an initial circuit board 10 is provided. The initial circuit board 10 includes a substrate 11 and two conductive circuit layers 12 bonded to two opposite surfaces of the substrate 11. The initial circuit board 10 has a via (not shown), and the two conductive circuit layers 12 are electrically connected through the via. Each conductive circuit layer 12 is mainly formed of a conductive circuit 120. There is at least one gap 13 between the conductive lines 120 of each conductive line layer 12.

The gap 13 has a bottom surface 131 and at least two side surfaces 132 connected to the bottom surface 131. The bottom surface 131 of the gap 13 is the surface of the substrate 11. In other words, the substrate 11 is exposed through the gap 13.

The material of the substrate 11 may be a material of a substrate conventionally applied to a circuit board such as polyimide.

Each of the conductive circuit layers 12 includes one or more layers. In this embodiment, the conductive circuit layer 12 includes a first layer 121 coupled to the surface of the substrate 11 and a second layer 122 coupled to the surface of the first layer 121 and away from the surface of the substrate 11. The first layer 121 is formed on the surface of the substrate 11 by a chemical plating method. The second layer 122 is formed on the surface of the first layer 121 by a plating method.

In step S2, referring to FIG. 2, a conductive polymer film 14 is formed on the bottom surface 131 of the gap 13. The conductive polymer film 14 covers the entire bottom surface 131 of the gap 13. The conductive polymer film 14 is in direct contact with and electrically connected to the conductive lines 120 on both sides of the gap 13. In other words, the conductive lines 120 on both sides of the gap 13 are electrically connected through the conductive polymer film 14.

The material of the conductive polymer film 14 may be polyaniline, polypyrrole, polythiophene, a derivative of aniline, a pyrrole derivative, or a polymer of a thiophene derivative. Such as poly 3,4-ethylene dioxythiophene or poly 2,5-dimethoxyaniline.

The thickness of the conductive polymer film 14 is smaller than the thickness of the conductive circuit layer 12. Preferably, the thickness of the conductive polymer film 14 is 1 to 1000 nm.

The step of forming the conductive polymer film 14 includes:

In step S21, a dense MnO ₂ (manganese dioxide) film (not shown) is formed on the surface of the substrate 11.

Specifically, the bare substrate 11 in the gap 13 is oxidized by using an oxidizing solution containing permanganate (MnO ^4- ) to form the MnO ₂ film on the surface of the substrate 11.

The oxidizing solution containing permanganate may be a mixture of permanganate and boric acid (HBO ₃ ). Wherein the permanganate is potassium permanganate may be (KMn _4), sodium permanganate (NaMn _4), a high lithium manganate (LiMn ₄₎ and other soluble permanganate. It can be understood that the boric acid may be replaced with hydrochloric acid, nitric acid, or the like.

The reaction mechanism of the permanganate-containing oxidizing solution for oxidizing the bare substrate 11 in the gap 13 is: 3 (CH) +5 MnO ^4- + 5H ⁺ → 3CO ₂ + 5MnO ₂ + 4HO ₂ . Among them, (CH) is derived from the substrate 11.

In step S22, a mixed liquid of a conductive polymer monomer and an acid solution is provided, and the mixed liquid is coated on the surface of the MnO ₂ film. Under the catalysis of manganese dioxide, the conductive polymer monomer is polymerized to form a conductive polymer film 14 on the surface of the substrate 11.

The conductive polymer monomer is a polymer having a conductive monomer formed after polymerization. The conductive polymer monomer is usually a liquid. The conductive polymer monomer may specifically be aniline, pyrrole or thiophene, etc., or an aniline derivative, pyrrole derivative, or thiophene derivative, such as 3,4-dioxyethylenethiophene, 2,5- Dimethoxyaniline and so on. Preferred is 3,4-dioxyethylenethiophene.

The acidic solution may be a conventionally used acidic solution such as sulfuric acid, nitric acid, and hydrochloric acid.

It can be understood that the conductive polymer film 14 can also be formed on the surface of the substrate 11 by spraying, printing or chemically depositing the conductive polymer material. The conductive polymer material may be a polymer of polyaniline, polypyrrole, polythiophene, a derivative of aniline, a pyrrole derivative, or a thiophene derivative. Such as poly 3,4-ethylene dioxythiophene or poly 2,5-dimethoxyaniline.

Step S3, referring to FIG. 3, a photoresist layer 15 is formed on the surfaces of the conductive circuit layer 12 and the conductive polymer film 14. The photoresist layer 15 is bonded to the surface of the conductive circuit layer 12 and the conductive polymer film 14 away from the substrate 11 and fills the gap 13.

The material of the photoresist layer 15 is a photosensitive dry film or a photosensitive ink.

Step S4, referring to FIG. 4 further, exposure and development are performed to form at least one electroplating tank 151 on the photoresist layer 15.

The plating tank 151 is a stepped groove. The plating tank 151 includes a first plating recessed portion 1511 and a second plating recessed portion 1512. The bottom surface of the first plated concave portion 1511 is a surface of the conductive circuit layer 12 away from the substrate 11. The bottom surface of the second plated concave portion 1512 is a surface of the conductive polymer film 14 far from the substrate 11. One side surface of the second plated concave portion 1512 coincides with the side surface 132 of the gap 13 adjacent to the first plated concave portion 1511. The other side surface of the two electroplated concave portions 1512 is located between two opposite side surfaces 132 of the gap 13.

In step S5, please refer to FIG. 5 further, a metal protective layer 16 is plated in the electroplating tank 151. At this time, the conductive polymer film 14 is used to pass a current required during the plating into the circuit board.

The metal protective layer 16 is substantially L-shaped. The metal protective layer 16 includes a first portion 161 bonded to a bottom surface of the first plated recessed portion 1511 and a second portion 162 formed in the second plated recessed portion 1512. The second portion 162 is in contact with the conductive polymer film 14.

The thickness of the second portion 162 of the metal protective layer 16 is less than or equal to one-half of the width of the second plated concave portion 1512.

The material of the metal protective layer 16 may be metal such as gold and nickel that are conventionally applied to circuit boards. The material of the metal protective layer 16 may be a metal alloy such as a nickel-gold alloy that is conventionally applied to a circuit board.

Step S6, referring to FIG. 6 further, removing the photoresist layer 15 so that the surface of the conductive circuit layer 12 covered by the photoresist layer 15, the surface of the conductive polymer film 14, and the surface of the metal protective layer 16 are exposed. .

The method for removing the photoresist layer 15 is a method conventionally applied to a circuit board for removing the photoresist layer.

Step S7, please refer to FIG. 7 further, remove the conductive polymer film 14 so that the surface of the substrate 11 covered by the conductive polymer film 14, the side surface of the gap 13 of the conductive circuit layer 12, and the metal protective layer 16 The surface is exposed, and a circuit board 100 is manufactured.

Since the conductive polymer film 14 is finally removed, there is a certain distance between the end of the second portion 162 adjacent to the substrate 11 and the substrate 11. The distance is preferably 1 to 1000 nm.

The method for removing the conductive polymer film 14 is a conventional method for decontaminating the surface of a circuit board.

When a manganese dioxide film is formed on the surface of the substrate 11 before the conductive polymer film 14 is formed, when the conductive polymer film 14 is removed, the manganese dioxide film is also removed at the same time.

It can be understood that after the conductive polymer film 14 and the manganese dioxide film are removed, the layer can be further increased on the conductive circuit layer 12 and the steps S1 to S7 are repeated to make more Layer of circuit board.

A circuit board 100 is used in electronic devices (not shown) such as computers, mobile phones, smart watches, and electronic readers. The circuit board 100 includes a substrate 11 and two conductive circuit layers 12 coupled to opposite surfaces of the substrate 11. Each conductive circuit layer 12 is mainly formed by a conductive circuit 120, and there is at least one gap 13 between the conductive circuits 120 of each conductive circuit layer 12. The gap 13 has a bottom surface 131 and at least two side surfaces 132 connected to the bottom surface 131. The bottom surface 131 is a surface of the base material 11.

The circuit board 100 further includes at least one metal protective layer 16. The metal protective layer 16 is substantially L-shaped. The metal protection layer 16 includes a first portion 161 and a second portion 162 extending from the first portion 161. The first portion 161 is bonded to a surface of the conductive circuit layer 12 remote from the substrate 11, and the second portion 162 is bonded to a side surface 132 of the gap 13 adjacent to the first portion 161. There is a certain distance between the end of the second portion 162 adjacent to the substrate 11 and the substrate 11. The distance is preferably 1 to 1000 nm.

The circuit board 100 does not include plating leads, which can effectively save the space of the circuit board 100 and improve the space utilization rate of the circuit board 100.

It can be understood that the circuit board 100 may be a flexible circuit board, a high-density interconnection circuit board (HDI), a rigid-flex board (Rigid-Flex), or an IC carrier board.

In the non-lead surface plating method of the present invention, a conductive polymer film 14 is formed on the substrate 11 of the conductive circuit layer 12 exposed through the gap 13, and the conductive polymer film 14 is used to achieve electroplating conduction, and a metal protective layer is formed by electroplating. After 16, the conductive polymer film 14 is removed. Compared with the conventional process of punching the electroplated lead when the electroplated lead is used to achieve electroplating continuity, and the electroplated lead is finally retained on the circuit board, the conductive polymer film 14 of the present invention does not require the punching process and simplifies the manufacturing process. The conductive polymer film 14 will eventually be removed from the circuit board to improve the space utilization of the circuit board. In addition, compared with the use of electroplated leads to achieve circuit conduction, the conductive polymer film 14 of the present invention does not require the use of a metal material for making electroplated leads and saves costs.

In addition, for a person of ordinary skill in the art, various other corresponding changes and deformations can be made according to the technical concept of the present invention, and all these changes and deformations should fall within the protection scope of the patent application scope of the present invention.

Circuit board: 100

Initial circuit board: 10

Substrate: 11

Conductive circuit layer: 12

Conductive line: 120

First floor: 121

Second floor: 122

Clearance: 13

Underside: 131

Side: 132

Conductive polymer film: 14

Photoresist layer: 15

Plating tank: 151

First plating recess: 1511

Second plating recess: 1512

Metal protective layer: 16

Part I: 161

Part II: 162

no

Claims (10)

A wireless surface plating method includes the following steps:
Step S1: An initial circuit board is provided. The initial circuit board includes a substrate and two conductive circuit layers bonded to opposite surfaces of the substrate. The initial circuit board has a via hole, and the two conductive circuit layers are borrowed. Electrically connected by the vias, each conductive circuit layer is mainly formed of conductive circuits, and at least one gap is formed between the conductive circuits of each conductive circuit layer, and the bottom surface of the gap is the surface of the substrate;
Step S2: forming a conductive polymer film on the bottom surface of the gap, and the conductive lines on both sides of the gap are electrically connected by the conductive polymer film;
Step S3: forming a photoresist layer on the surface of the conductive circuit layer and the conductive polymer film far from the substrate;
Step S4: forming at least one plating bath on the photoresist layer;
Step S5: plating a metal protective layer in the plating tank;
Step S6: removing the photoresist layer to expose the surface of the conductive circuit layer covered by the photoresist layer, the surface of the conductive polymer film, and the surface of the metal protective layer;
Step S7: The conductive polymer film is removed, so that the surface of the substrate covered by the conductive polymer film, the sides of the gaps of the conductive circuit layer, and the surface of the metal protective layer are exposed. According to the leadless surface electroplating method according to item 1 of the scope of patent application, wherein the conductive polymer film covers the entire bottom surface of the gap, and the conductive polymer film is in direct contact with and electrically connected to conductive lines on both sides of the gap, The conductive polymer film has a thickness of 1 to 1000 nm. The non-wire surface plating method according to item 1 of the scope of patent application, wherein the material of the conductive polymer film is polyaniline, polypyrrole, polythiophene, aniline derivative, pyrrole derivative, or polymerization of thiophene derivative Thing. The method for electroplating a surface without a lead as described in item 1 of the scope of patent application, wherein step S2 includes the following steps:
Step S21: oxidize the bare substrate in the gap with an oxidizing solution containing permanganate to form a manganese dioxide film on the surface of the substrate;
Step S22: Provide a mixed solution of the conductive polymer monomer and the acidic solution, and apply the mixed solution on the surface of the manganese dioxide film. Under the catalysis of manganese dioxide, the conductive polymer monomer is generated. Polymerize to form a conductive polymer film on the surface of the substrate. The conductive polymer monomer is aniline, pyrrole, thiophene, an derivative of aniline, a pyrrole derivative, or a thiophene derivative. The method for electroplating the surface of a leadless wire according to item 1 of the scope of patent application, wherein the method for forming a conductive polymer film is spraying, printing, or chemically depositing a conductive polymer material on the surface of a substrate. The method for electroplating the surface of a leadless wire according to item 1 of the scope of the patent application, wherein the photoresist layer is a photosensitive dry film or a photosensitive ink. The method for electroplating the surface of a non-conductor wire according to item 1 of the scope of patent application, wherein the conductive polymer film is removed by a method of decontaminating the surface of the circuit board. According to the lead-free surface electroplating method according to item 1 of the scope of patent application, wherein the electroplating tank is a stepped groove, the electroplating tank includes a first electroplated concave portion and a second electroplated concave portion, and a bottom surface of the first electroplated concave portion is The surface of the conductive circuit layer away from the substrate, the bottom surface of the second plated concave portion is the surface of the conductive polymer film away from the substrate, and the thickness of the metal protective layer is less than or equal to half of the width of the second plated concave portion. one. The method for electroplating a surface without wires according to item 8 of the scope of patent application, wherein the metal protective layer is L-shaped, and the metal protective layer includes a first portion bonded to a bottom surface of the first electroplated recessed portion and formed on the second The second part in the plating recess. A circuit board includes a substrate and two conductive circuit layers bonded to opposite surfaces of the substrate. Each conductive circuit layer is mainly formed of conductive circuits. There is at least one between the conductive circuits of each conductive circuit layer. A gap, the gap having a bottom surface and at least two side surfaces connected to the bottom surface, the bottom surface being the surface of the substrate, the circuit board further including at least one metal protective layer, which is improved in that the metal protective layer includes a first portion and A second portion extending from the first portion, the first portion being bonded to a surface of the conductive circuit layer remote from the substrate, the second portion being bonded to a side of the gap adjacent to the first portion, the second portion There is a certain distance between the end of a portion of the adjacent substrate and the substrate.