High-speed line surface silver deposition method of inner-layer substrate, circuit board preparation method and circuit board

Abstract

The invention discloses a high-speed line surface silver deposition method of an inner-layer substrate, a circuit board preparation method and a circuit board, and belongs to the technical field of printed circuit boards, and the high-speed line surface silver deposition method comprises the steps of inner-layer substrate silver deposition, resin printing and curing and inner-layer basic silver removal. The micron-level pure silver layer is processed on the surface of the inner-layer high-speed wire, and current is concentrated on the silver conductor layer during high-frequency application, so that the conductor loss is reduced, and the insertion loss of the PCB is further reduced. Meanwhile, the silver deposition method is combined with the circuit board preparation method, the normal stack-up structure and process design of the PCB are not affected, the reliability performance of the PCB is not affected, the silver deposition principle is non-electrolytic replacement reaction, and low-cost amp is achieved; the environment-friendly characteristic is achieved, and RoHSamp is met; wEE and other system requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board, and in particular to a high-speed line surface silvering method of inner layer substrate, a circuit board preparation method and a circuit board. BACKGROUND

[0002] Compared with conventional copper foil conductor, silver has better electrical conductivity. At present, silver conductors have been used in connectors and cables in batches, and a small amount of conductive silver paste is used in the surface layer for conduction application, but copper conductors are used in the internal structure, and the application of silver conductors is still a blank in the industry. In the loss control of high-frequency high-speed products, the conductor loss accounts for a higher and higher proportion as the signal frequency increases, so it is an urgent technical problem to use silver conductors in the internal structure. SUMMARY

[0003] The present application aims to overcome the deficiencies in the prior art, and provides a high-speed line surface silvering method of inner layer substrate, a circuit board preparation method and a circuit board, which solves the technical problem of increasing conductor loss in the loss control of high-frequency high-speed products.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: In a first aspect, the present application provides a high-speed line surface silvering method of inner layer substrate, comprising: The inner layer substrate silvering includes setting the silvering thickness according to product requirements, and silvering the entire surface of the inner layer substrate according to the silvering thickness. The resin printing and curing includes printing liquid resin on the surface of the high-speed line of the inner layer substrate, and performing liquid resin curing treatment. The inner layer substrate silvering includes removing silver from the area where the liquid resin is not printed by acid washing or silver removing solution.

[0005] Optionally, the silvering of the entire surface of the inner layer substrate according to the silvering thickness includes setting a horizontal line speed according to the silvering thickness, and silvering the entire surface of the inner layer substrate according to the horizontal line speed.

[0006] Optionally, the silvering of the inner layer substrate further includes fixing the inner layer substrate by a pre-prepared silvering belt clamp, and the silvering belt clamp includes a belt clamp jig, and the belt clamp jig is provided with a groove matching the size of the inner layer substrate.

[0007] Optionally, the liquid resin curing treatment includes UV curing or baking curing according to the type of liquid resin.

[0008] Optionally, the silvering thickness ranges from 0.4 to 1 microns, and the current frequency band range suitable for the high-speed line ranges from 13.3 GHz to 53.3 GHz.

[0009] In a second aspect, the present application provides a method for manufacturing a circuit board with high-speed lines, comprising: manufacturing inner-layer substrates, including manufacturing corresponding inner-layer substrates according to the structure of the circuit board, and etching corresponding inner-layer patterns on each of the inner-layer substrates; silver plating on the surface of the high-speed lines, including silver plating on the inner-layer substrates by using the method for silver plating on the surface of the high-speed lines as described above; brown oxidation of the inner-layer substrates, including oxidizing the inner-layer substrates after the silver plating; pressing the inner-layer substrates, including pressing the circuit board together by using prepregs and a hot press according to the sequence of the structure of the circuit board; outer-layer drilling and electroplating, including drilling holes for electroplating and press-fitting plugs by using a drill, and depositing a copper layer with a preset thickness on the inner wall of the holes by using chemical copper plating and electroplating; manufacturing outer-layer lines, including manufacturing outer-layer patterns by using full-board imaging or pattern electroplating imaging transfer according to the line diagram of the circuit board; manufacturing outer-layer solder masks, including forming solder masks by ink covering according to the line diagram of the circuit board; PCB surface treatment and forming.

[0010] Optionally, the PCB after the surface treatment and forming needs to be tested for electrical performance and appearance.

[0011] In a third aspect, the present application provides a circuit board with high-speed lines, which is manufactured by using the method for manufacturing a circuit board as described above.

[0012] Compared with the prior art, the present application has the following beneficial effects: The present application provides a method for silver plating on the surface of high-speed lines of inner-layer substrates, a method for manufacturing a circuit board, and a circuit board. By using the silver plating method, a micron-level pure silver layer is processed on the surface of the high-speed lines of the inner-layer substrates in a conventional PCB structure. When used in high-frequency applications, the current is concentrated on the silver conductor layer, thereby reducing the conductor loss and further reducing the PCB insertion loss. At the same time, the silver plating method is combined with the method for manufacturing a circuit board, without affecting the normal stacking and process design of the PCB, and without affecting the reliability of the PCB. The silver plating principle is a non-electrolytic displacement reaction, which has the characteristics of low cost and environmental protection, and meets the requirements of the RoHS and WEE systems. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a flowchart of the method for silver plating on the surface of high-speed lines of inner-layer substrates provided by the embodiment of the present application; Figure 2 is a schematic diagram of the inner-layer substrates before silver plating of the inner-layer substrates provided by the embodiment of the present application; Figure 3is a schematic diagram of the inner layer substrate after silver deposition of the inner layer substrate provided by the embodiment of the present application; Figure 4 is a schematic diagram of the inner layer substrate after printing of the liquid resin provided by the embodiment of the present application; Figure 5 is a schematic diagram of the inner layer substrate after silver deposition of the inner layer substrate provided by the embodiment of the present application; Figure 6 is a schematic diagram of the theoretical silver thickness corresponding to 13.3GHz simulated according to the skin effect principle provided by the embodiment of the present application; Figure 7 is a schematic diagram of the theoretical silver thickness corresponding to 53.3GHz simulated according to the skin effect principle provided by the embodiment of the present application; Figure 8 is a flowchart of the circuit board preparation method with high-speed lines provided by the embodiment of the present application. DETAILED DESCRIPTION

[0014] The present application will be further described below in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0015] Embodiment one:

[0016] As shown in Figure 1 , the present application provides a silver deposition method for the surface of high-speed lines of an inner layer substrate, comprising: 1. Silver deposition of the inner layer substrate, including setting the silver deposition thickness according to product requirements, and depositing silver on the entire surface of the inner layer substrate according to the silver deposition thickness.

[0017] The silver deposition operation at this place is based on the conventional silver deposition line for PCB surface treatment in the industry, and does not need to configure additional silver deposition equipment. The horizontal line speed is set according to the silver deposition thickness, and silver is deposited on the entire surface of the inner layer substrate according to the horizontal line speed. Figure 2 and Figure 3 As shown, the schematic diagram of the inner layer substrate before and after silver deposition of the inner layer substrate is shown.

[0018] In addition, in order to prevent the over-thin inner layer substrate from being clamped during silver plating processing, the inner layer substrate is also fixed by a pre-prepared silver plating belt clamp, and the silver plating belt clamp comprises a belt clamp jig, and a groove matching the size of the inner layer substrate is arranged on the belt clamp jig, and the inner layer substrate is assembled in the groove during silver plating.

[0019] 2. Resin printing and curing, including printing liquid resin on the surface of the high-speed lines of the inner layer substrate, and performing liquid resin curing treatment.

[0020] The purpose of printing the liquid resin is to protect the silver plating layer on the high-speed lines.

[0021] Liquid resin curing process includes: UV curing or baking curing according to the type of liquid resin.

[0022] UV curing resin occurs photopolymerization under ultraviolet light (wavelength 200-400 nm) irradiation, achieving second-level curing, suitable for high-efficiency production scenarios.

[0023] Baking curing initiates crosslinking reaction by heating, suitable for thick-walled parts or high-temperature stable scenarios.

[0024] Here, the curing is semi-cured, and it will also melt and flow when the inner layer substrate is laminated, so it will not affect the uniformity of the insulating layer thickness of the PCB. As shown in Figure 4 , it is an inner layer substrate schematic diagram after liquid resin printing.

[0025] 3, Inner layer basic silver fading, including removing silver by acid washing or silver fading medicine.

[0026] The purpose of silver fading is to prevent silver from being brought into the subsequent brown process, which will adversely affect the subsequent process. As shown in Figure 5 , it is an inner layer substrate schematic diagram after the inner layer basic silver fading.

[0027] Ansys simulation software calculates the required chemical silver thickness at a specified frequency as shown in Table 1.

[0028] The embodiment of the present application does not affect the normal stacking and process design of PCB, uses the commonly used chemical silver replacement level line, and processes a 0.4-1.0 micron pure silver layer on the surface of the inner layer high-speed line, and then uses liquid resin protection. According to the skin effect principle, as shown in Figure 6 and Figure 7 , it can concentrate the current in the silver conductor layer in the frequency range of 13.3 GHz-53.3 GHz, thereby reducing the conductor loss, and further reducing the PCB insertion loss.

[0029] Table 1: Required chemical silver thickness at a specified frequency

[0030] Conductivity: Copper: 63 x 10*6 siemens / m Silver: 59 x 10*6 siemens / m Gap:7% Theoretically, it can reduce the conductor loss by 7%.

[0031] The insertion loss at 53.3 GHz is shown in Table 2.

[0032] Table 2: Insertion loss of copper and silver layer with the same thickness

[0033] Theoretical insertion loss can be reduced by 2.28%.

[0034] Embodiment two: As Figure 8 shown, the embodiment of the application provides a circuit board preparation method with high-speed lines, comprising: 1. Preparing inner layer substrates, including making corresponding inner layer substrates according to the structure of the circuit board, and etching corresponding inner layer patterns on each inner layer substrate.

[0035] 2. Silver plating on the surface of high-speed lines, including silver plating treatment on the inner layer substrate by using the silver plating method on the surface of high-speed lines provided in Embodiment One.

[0036] 3. Brown oxidation of the inner layer substrate, including oxidation treatment of the inner layer substrate after silver plating treatment. The main purpose is to increase the bonding force between the inner layer substrate and the prepreg or copper foil.

[0037] The application only covers silver plating on the surface of high-speed lines, and the remaining large copper area can still be processed by brown oxidation, without reducing the interlayer bonding force of the inner layer and affecting the reliability performance of the PCB.

[0038] 4. Inner layer substrate pressing, including pressing the circuit board together using the prepreg and hot press according to the sequence of the circuit board structure.

[0039] 5. Outer layer drilling and electroplating, including drilling the through holes that need to be electroplated and crimped and plugged using a drilling machine, and depositing a copper layer with a preset thickness on the inner wall of the through hole with chemical copper deposition and electroplated copper through hole (>20um).

[0040] 6. Outer layer circuit making, including making outer layer patterns using full board image or pattern electroplating image transfer according to the circuit diagram of the circuit board.

[0041] 7. Outer layer solder mask making, including forming a solder mask layer by ink covering according to the circuit diagram of the circuit board.

[0042] 8. PCB surface treatment and forming.

[0043] 9. Electrical performance test and appearance inspection.

[0044] The steps 1, 3-9 belong to the conventional work flow of PCB, and are listed here to show that the present application does not affect the normal lamination and flow design of PCB. In the conventional PCB structure of the present application, a micron-level pure silver layer is processed on the surface of the inner layer high-speed line, so that the current is concentrated on the silver conductor layer when high-frequency application is performed, thereby reducing the conductor loss and further reducing the PCB insertion loss. The present application does not affect the normal lamination and flow design of PCB, nor does it affect the reliability performance of PCB. The silver deposition principle is a non-electrolytic displacement reaction, which has the characteristics of low cost and environmental protection, and meets the requirements of RoHS, WEE and other systems.

[0045] Example three: The present application provides a circuit board with high-speed lines, which is prepared by the circuit board preparation method provided in the above-mentioned example two. The circuit board has the beneficial effects of the preparation method of the printed circuit board according to any of the embodiments of the present application, which will not be repeated here.

[0046] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, a number of improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A high-speed wire surface silvering method of an inner layer substrate, characterized by, The method comprises the following steps: Inner layer substrate silvering, including setting silvering thickness according to product requirements, and silvering the whole surface of the inner layer substrate according to the silvering thickness; Resin printing and curing, including printing liquid resin on the high-speed line surface of the inner layer substrate, and curing the liquid resin; Inner layer substrate silvering removal, including removing silvering in the area without printing liquid resin by acid washing or silvering medicine.

2. The high-speed wire surface silvering method of an inner layer substrate according to claim 1, characterized by, The step of silvering the whole surface of the inner layer substrate according to the silvering thickness comprises the following steps: Setting horizontal line speed according to the silvering thickness, and silvering the whole surface of the inner layer substrate set horizontally according to the horizontal line speed.

3. The high-speed wire surface silvering method of the inner layer substrate according to claim 1, characterized by, The step of silvering the inner layer substrate further comprises the following steps:

4. The high-speed wire surface silvering method of an inner layer substrate according to claim 1, characterized by, Fixing the inner layer substrate by using a prepared silvering belt fixture, wherein the silvering belt fixture comprises a belt fixture, and the belt fixture is provided with a groove matching the size of the inner layer substrate. The step of curing the liquid resin comprises the following steps:

5. The high-speed wire surface silvering method of an inner layer substrate according to claim 1, characterized by, According to the type of the liquid resin, UV curing or baking curing is performed.

6. A method of manufacturing a circuit board having a high-speed line, characterized by, The silvering thickness ranges from 0.4 to 1 microns, and the current frequency range suitable for the high-speed line ranges from 13.3 GHz to 53.3 GHz. The method comprises the following steps: Preparation of inner layer substrate, including preparing corresponding inner layer substrates according to the structure of the circuit board, and etching corresponding inner layer patterns on each of the inner layer substrates; High-speed line surface silvering, including silvering the inner layer substrate by using the high-speed line surface silvering method according to any one of claims 1-5; Inner layer substrate brown oxidation, including performing oxidation treatment on the silvered inner layer substrate; Inner layer substrate pressing, including pressing the circuit board together by using prepreg and a hot press according to the sequence of the structure of the circuit board; Outer layer drilling and electroplating, including drilling a through hole for electroplating and crimping plug-in use by using a drilling machine, and depositing a copper layer with a preset thickness on the inner wall of the through hole by using chemical copper deposition and electroplating copper; Outer layer circuit manufacturing, including manufacturing an outer layer pattern by using full-board image or pattern electroplating image transfer according to the circuit diagram of the circuit board; Outer layer anti-soldering manufacturing, including forming an anti-soldering layer by ink covering according to the circuit diagram of the circuit board; 7. The method of manufacturing a circuit board with high-speed lines according to claim 6, wherein PCB surface treatment and forming.

8. A circuit board provided with a high-speed line, characterized by comprising: After the PCB surface treatment and forming, electrical performance testing and appearance inspection are further required. The circuit board is prepared by using the circuit board preparation method according to claim 6 or 7.

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