TWI420992B - Method for manufacturing printed circuit board - Google Patents

Description

Circuit board manufacturing method

The present invention relates to circuit board manufacturing technology, and in particular, to a circuit board manufacturing method.

Flexible circuit boards are widely used in various fields, especially in portable electronic devices that are light, thin, short, and small, such as mobile phones. Flexible circuit boards for mobile phones are usually produced by the steps of making circuits, making cover layers, electroless nickel plating, electroless gold plating, organic coating processes, and assembly processes. In the circuit fabrication process, a plurality of conductive lines and a plurality of pads are usually formed on the flexible circuit board. The plurality of conductive lines and the plurality of pads are each of a copper material, and each of the pads is connected to at least one of the conductive lines. The subsequent step of making the cap layer refers to forming a cap layer on a plurality of conductive traces. The electroless nickel plating and the electroless gold plating step refer to forming a chemical nickel layer and a chemical gold layer on at least one pad surface of the plurality of pads as a contact point or a plug point to protect the at least one pad. The Organic Solderability Preservatives (OSP) is used to protect the pads by forming an organic solder mask on the surface of the plurality of pads that are not required to be soldered or assembled with the electronic components. . Moreover, the organic solder mask does not affect the solder assembly of the pads with the electronic components in subsequent assembly processes.

The OSP process typically includes steps such as degreasing, microetching, water washing, film formation, water washing, and drying. Wherein, the micro-etching refers to placing the flexible circuit board in the micro-etching liquid, so that the micro-etching The etchant erodes the copper layers of the pad surfaces to roughen the pad surfaces to facilitate subsequent formation of a film layer on the roughened pad surface. However, since the microetching liquid is a strong electrolyte, the standard potential of the chemical gold layer formed on at least one pad surface as a contact point or a plug point is higher than the standard potential of copper on the surface of other pads, thereby In the etched liquid, the electrical contact between gold and copper is caused and the electrode potential difference is present at the same time. From then on, galvanic corrosion is caused between the two, so that the copper etch rate is greatly improved during the micro-etching process. In this way, the degree of micro-etching is not easy to control, and the wiring causes the pad and the conductive line connected to the pad to be excessively bitten and the line is broken.

In view of this, it is necessary to provide a circuit board manufacturing method that can avoid galvanic corrosion during microetching.

Hereinafter, an embodiment of a circuit board will be described by taking an embodiment as an example.

A circuit board manufacturing method comprising the steps of: providing a circuit board, the circuit board comprising an insulating layer, a conductive layer formed on the insulating layer, and a plating layer formed on the partial conductive layer, the material of the conductive layer having a first electrode potential The plating layer is in electrical contact with the conductive layer, the material of the plating layer has a second electrode potential, the second electrode potential is greater than the first electrode potential; a protective layer is formed on the plating layer; the circuit board is wet The treatment liquid is subjected to a wet treatment, and the wet treatment liquid is an electrolyte. During the wet treatment, the protective layer and at least a portion of the conductive layer are exposed to the wet treatment liquid; and the protective layer is removed to obtain a wet-processed circuit board.

Compared with the prior art, the circuit board manufacturing method of the present technical solution has the following advantages: since the circuit board shields the plating layer with a protective layer before performing the wet processing, The plated layer is not exposed to the wet treatment liquid, and the occurrence of galvanic corrosion between the plating layer and the exposed conductive layer in the wet treatment liquid is avoided, so that the exposed conductive layer is not excessively exposed during the wet treatment process. Processing to ensure the production yield and excellent performance of the board.

10‧‧‧ boards

11‧‧‧Insulation

12‧‧‧ Conductive layer

13‧‧‧ Coverage

14‧‧‧ plating

120‧‧‧Electrical graphics

121‧‧‧Electrical circuit

122‧‧‧ pads

1221‧‧‧Contact plate

1222‧‧‧ Assembly disk

15‧‧‧Transition layer

20‧‧‧Protective layer

30‧‧‧Organic soldering layer

1 is a top plan view of a circuit board provided by an embodiment of the present technical solution.

2 is a cross-sectional view of the circuit board provided by the embodiment of the present technical solution taken along line II-II of FIG. 1.

FIG. 3 is a schematic diagram of forming a protective layer on a plating layer of a circuit board provided by an embodiment of the present technical solution.

FIG. 4 is a schematic view showing the wetness treatment and surface treatment of the circuit board provided by the embodiment of the present technical solution.

FIG. 5 is a schematic diagram of the protective layer of the circuit board provided by the embodiment of the present technical solution.

The method for fabricating the circuit board provided by the technical solution will be described in detail below with reference to the accompanying drawings and embodiments.

The circuit board manufacturing method provided by the embodiment of the technical solution includes the following steps:

In the first step, please refer to FIG. 1 and FIG. 2 together to provide the circuit board 10.

The circuit board 10 can be a multi-layer board or a single layer board. In the embodiment, the circuit board 10 is processed, the cover layer, the electroless nickel plating, and the electroless gold plating are processed. The single layer board of the step is introduced as an example. The circuit board 10 includes an insulating layer 11, a conductive layer 12, a cover layer 13, and a plating layer 14.

The insulating layer 11 may be a hard resin layer such as an epoxy resin, a fiberglass cloth, or the like, or a flexible resin layer such as Polyimide (PI) or polyethylene terephthalate (Polyethylene Terephtalate). , PET), Teflon, Polyamide, Polymethylmethacrylate, Polycarbonate or Polyimide-Polyethylene-terephthalate copolymerization (Polyamide polyethylene-terephthalate copolymer).

The conductive layer 12 is formed on one side of the insulating layer 11 and is in contact with the insulating layer 11. The conductive layer 12 is formed with a conductive pattern 120 including at least one conductive line 121 and a plurality of pads 122. The plurality of pads 122 includes at least one contact pad 1221 and at least one assembly pad 1222. The contact pad 1221 refers to a pad for making contact or plugging, for example, a contact for contacting a mobile phone case in a circuit board for a mobile phone, or a connector for interfacing with other components in a circuit board. . Assembly disk 1222 refers to a pad for assembling electronic components, that is, a pad for electrical contact with a pin or contact of an electronic component. In this embodiment, the number of the conductive lines 121, the contact pads 1221 and the assembly pads 1222 are plural, and each of the conductive lines 121 is connected between a contact pad 1221 and an assembly disk 1222. The material of the conductive layer 12 is generally copper, and the electrode potential of the copper is 0.337V.

The cover layer 13 is generally formed on the surface of the insulating layer 11 having no conductive pattern 120 and the surface of the plurality of conductive lines 121 by a printing technique for protecting the plurality of conductive lines 121 from oxidation of the conductive lines 121. The material of the cover layer 13 usually includes a ring Oxygen resin IR baking type, UV curing type, liquid photosensitive type (LPISM-Liquid Photo Imagable Solder Mask) type ink, and dry film solder mask type (Dry Film, Solder Mask).

The plating layer 14 may be a chemical silver layer, a chemical gold layer, an electroplated gold layer or the like for forming on the surface of the at least one contact pad 1221 to protect the at least one contact pad 1221. In this embodiment, the plating layer 14 is a chemical gold layer, which not only protects the plurality of contact pads 1221, but also avoids oxidation of the contact pads 1221 and enhances the conductivity of the contact pads 1221. The electrode potential of gold is 1.68V, which is higher than the electrode potential of copper.

In order to improve the adhesion of the chemical gold layer on the contact pad 1221, the bonding force between the chemical gold layer and the contact pad 1221 is enhanced. Before the chemical gold layer is formed on the contact pad 1221, a transition layer 15 is usually formed on the contact pad 1221. That is, the transition layer 15 is formed between the contact pad 1221 and the plating layer 14 and is in contact with the contact pad 1221 and the plating layer 14. The transition layer 15 can be a conductive material layer such as a chemical nickel layer, an electroless nickel palladium layer, or an electroplated nickel layer, so as to enhance the bonding force between the plating layer 14 and the contact pad 1221, and also make the plating layer 14 and the contact pad 1221. Keep electrical contact. In this embodiment, the transition layer 15 is an electroless nickel layer.

Of course, those skilled in the art can understand that the circuit board 10 can also be fabricated through the inner layer circuit, the inner layer and the outer layer are pressed, drilled, hole metallized, outer layer circuit fabricated, coated, and electroless nickel plated. And a multi-layer board for processing steps such as electroless gold plating, comprising a plurality of insulating layers and a conductive layer spaced apart from each other, and having a plurality of via holes to conduct a plurality of conductive layers. The outer layer of the multilayer board may have a structure similar to that of the circuit board 10.

In the second step, referring to FIG. 3, a protective layer 20 is formed on the plating layer 14, and the protective layer 20 may be an ink, a photoresist or other insulating material that is easy to remove. Specifically, the process of forming the protective layer 20 on the surface of the chemical gold layer may be printing, coating, laminating or other methods.

In the third step, the circuit board 10 is wet-processed with a wet processing liquid for the electrolyte, and the protective layer 20 and at least a portion of the conductive layer 12 are exposed to the wet processing liquid.

This wet processing can be a major process in the board fabrication process, such as line etching, or an auxiliary process in one of the main processes in the board fabrication process, such as microetching in organic coating processes.

In the present embodiment, the wet treatment refers to a microetching treatment in an organic coating process, and the wet treatment liquid refers to a microetching liquid. Wet processing the circuit board 10 with a wet processing liquid means placing the circuit board 10 in the micro-etching bath to perform micro-etching treatment with the micro-etching liquid to facilitate subsequent formation of the organic solder-preserving layer in the organic coating process. Since the cover layer 13 is formed on the surface of the conductive line 121 and the surface of the insulating layer 11, the protective layer 20 is formed on the surface of the plurality of contact pads 1221, and therefore, only the plurality of assembled pads 1222 in the entire conductive layer 12 are exposed to the micro-etching liquid. Of course, in the micro-etching process, the cover layer 13 and the protective layer 20 are exposed to the micro-etching liquid in addition to the plurality of the assembled layers 1222 of the conductive layer 12. The micro-etching liquid is mainly composed of sodium persulfate and sulfuric acid, and has certain corrosiveness to copper, so that the surface of the plurality of assembled disks 1222 can be roughened.

In the technical solution, since the circuit board 10 masks the plating layer 14 or the chemical gold layer before the micro-etching treatment, the chemical gold layer is not exposed to the micro-etching liquid, thereby avoiding the micro-etching liquid. Galvanic corrosion between the middle chemical gold layer and the assembly plate 1222 The resulting assembly plate 1222 is slightly and evenly punctured during the micro-etching process without being excessively eroded, thereby ensuring the yield and performance of the circuit board 10.

Referring to FIG. 4, in the embodiment, after the micro-etching process is performed on the circuit board 10, the circuit board 10 is also subjected to an Organic Solderability Preservatives (OSP), thereby forming a layer on the surface of the plurality of assembled disks 1222. Organic solder layer 30. The organic solder mask 30 is used to protect the assembly disk 1222 from oxidation of the assembly disk 1222 and is retracted when the assembly disk 1222 is soldered to the electronic component so as not to affect the electrical contact of the assembly disk 1222 with the electronic components.

Of course, those skilled in the art can understand that the wet processing can also be any other process that requires treatment with an electrolyte. After the circuit board 10 is wet-processed, the circuit board 10 can be subjected to any other electrolyte solution. Surface treatment process after the process of treatment.

In the fourth step, referring to FIG. 5, the protective layer 20 is removed by a suitable solvent or etchant to obtain a wet-processed and surface-treated circuit board 10. For example, when the protective layer 20 is a solid photoresist, the protective layer 20 may be removed by stripping or dissolution with a developing solution or the like.

The circuit board manufacturing method of the present technical solution has the following advantages: since the circuit board 10 shields the plating layer 14 with the protective layer 20 before performing the wet processing, the plating layer 14 is not exposed to the wet processing liquid, thereby avoiding the wet processing. The galvanic corrosion between the liquid plating layer 14 and the exposed portion of the conductive layer 12 is such that the exposed portion of the conductive layer 12 is not overtreated during the wet processing process, thereby ensuring the yield and performance of the circuit board 10. .

The circuit board production design system and method of the present technical solution are not limited to the foregoing structure, and the skill A person skilled in the art can make various other corresponding changes and modifications to the coating device provided by the embodiment according to the technical idea of the technical solution. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

1222‧‧‧ Assembly disk

14‧‧‧ plating

20‧‧‧Protective layer

30‧‧‧Organic soldering layer

Claims (9)

A circuit board manufacturing method comprising the steps of: providing a circuit board, the circuit board comprising an insulating layer, a conductive layer formed on the insulating layer, and a plating layer formed on the partial conductive layer, the material of the conductive layer having a first electrode potential The plating layer is in electrical contact with the conductive layer, the material of the plating layer has a second electrode potential, the second electrode potential is greater than the first electrode potential; a protective layer is formed on the plating layer; The wet treatment liquid is subjected to a wet treatment, and the wet treatment liquid is an electrolyte. During the wet treatment, the protective layer and at least a portion of the conductive layer are exposed to the wet treatment liquid; and the circuit board is subjected to an organic coating process to An organic solder resist layer is formed on at least a portion of the surface of the conductive layer after the wet treatment; the protective layer is removed to obtain a wet-processed circuit board. The method of manufacturing a circuit board according to the first aspect of the invention, wherein the protective layer is an ink. The method of fabricating a circuit board according to claim 1, wherein the protective layer is a photoresist. The circuit board manufacturing method of claim 1, wherein the plating layer and the conductive layer have a conductive transition layer, and the material of the transition layer comprises nickel. The method for fabricating a circuit board according to claim 1, wherein the plating layer is a chemical silver layer, a chemical gold layer, an electroplated gold layer or a chemical tin layer. The method for fabricating a circuit board according to the first aspect of the invention, wherein the conductive layer The material is copper, and the material of the plating layer is gold, silver or tin. The circuit board manufacturing method of claim 1, wherein the conductive layer is formed with a conductive pattern, the conductive pattern comprising at least one contact pad, at least one assembly disk, and at least one contact pad coupled to the at least one assembly At least one conductive line between the disks, the plating layer being formed on the surface of the at least one contact pad, the at least one assembly disk being exposed to the wet processing liquid during the wet processing. The circuit board manufacturing method of claim 7, wherein the circuit board further comprises a cover layer formed on a surface of the at least one conductive line. The method of manufacturing a circuit board according to claim 1, wherein the wet processing is a micro-etching treatment.