HIGH FREQUENCY SIGNAL TRANSMISSION STRUCTURE AND METHOD FOR SAME

Abstract

A high frequency signal transmission structure includes an insulating sheet and a conductive wiring layer forming on the insulating sheet. The conductive wiring layer includes a silver conductive layer forming on the insulating sheet, a copper conductive layer forming on the silver conductive layer, and a silver covering layer covering a top surface and side surfaces of the copper conductive layer. The silver conductive layer and the silver covering layer together surround the copper conductive layer.

Description

The subject matter herein generally relates to a multifunction sensing devices.

BACKGROUND

Metal copper is generally used to manufacturing conductive wire layer. However, when the conductive wire layer is used to transmit a high frequency signal, a large loss is generated.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by way of example only, with reference to the attached figures.

FIG. 1 is a flowchart of a method for manufacturing a high frequency signal transmission structure in accordance with a first embodiment.

FIG. 2 is a diagrammatic view of an insulating sheet of the structure of FIG. 1 in accordance with a first embodiment.

FIG. 3 is a diagrammatic view of a silver bottom layer formed on the insulating sheet of FIG. 2.

FIG. 4 is a diagrammatic view of a dry film formed on the silver bottom layer of FIG. 3.

FIG. 5 is a diagrammatic view of the dry film being exposed to a lithographic method of FIG. 4.

FIG. 6 is a diagrammatic view of the dry film being developed through a lithographic method of FIG. 5.

FIG. 7 is a diagrammatic view of forming of a copper conductive layer on the silver bottom layer of FIG. 6.

FIG. 8 is a diagrammatic view showing removal of the dry film of FIG. 6.

FIG. 9 is a diagrammatic view showing the silver bottom layer is etched to form a silver conductive layer on the insulating sheet.

FIG. 10 is a diagrammatic view of a silver covering layer being formed on the copper conductive layer of FIG. 8 to obtain a high frequency signal transmission structure.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.

Several definitions that apply throughout this disclosure will now be presented.

The term “substantially” is defined to be essentially conforming to the particular dimension, shape, or other feature that the term modifies, such that the component need not be exact. For example, “substantially cylindrical” means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. The references “a plurality of” and “a number of” mean “at least two.”

FIG. 10 illustrates a high frequency signal transmission structure 100 according to a first embodiment. The high frequency signal transmission structure 100 includes an insulating sheet 10 and a conductive wiring layer 40 formed on the insulating sheet 10.

A material of the insulation layer 10 is selected from the group consisting of polynaphthalene dicarboxylic acid glycol ester (PEN), polyimide (PI), and polyterephthalate (PET). The conductive wiring layer 40 includes a silver conductive layer 22 formed on the insulating sheet 10, a copper conductive layer 20 formed on the silver conductive layer 22, and a silver covering layer 30 covering a top surface and side surfaces of the copper conductive layer 20. The copper conductive layer 20 is sandwiched between the silver conductive layer 22 and the silver covering layer 30. A thickness of the silver conductive layer 22 is about 0.1˜2 nanometers. A thickness of the silver conductive layer 22 is same with a thickness of the silver covering layer 30.

An electrical conductivity of silver is about σ=6.17*10⁷ S/m, an electrical conductivity of copper is about σ=5.80*10⁷ S/m. When the high frequency signal transmission structure 100 is configured to transmit a high frequency signal, the current of the high frequency signal flowing through the conductive wiring layer 40 tends to be distributed on a surface of the conductive wiring layer 40 due to a conductor skin effect. And because the silver conductive layer 22 and the silver covering layer 30 together surround the copper conductive layer 20, and thus the current tends to be distributed on a surface of the silver conductive layer 22 and the silver covering layer 30, and since an electrical conductivity of silver is greater than an electrical conductivity of copper, transmission losses are reduced, and a transmission efficiency of the high frequency signal is improved.

FIG. 1 illustrates a flowchart in accordance with a second embodiment. The example method 200 for manufacturing the high frequency signal transmission structure 100 (shown in FIG. 10) is provided by way of an example, as there are a variety of ways to carry out the method. Additionally, the illustrated order of blocks is by example only and the order of the blocks can change. The method 200 can begin at block 201.

At block 201, as shown in FIG. 2, an insulating sheet 10 is provided and is pre-treated using a plasma method to strength a silver bottom layer 12 combine with the insulating sheet 10. The insulating sheet 10 is made from polyester polymer, thus the insulating sheet 10 comprised of ester group (—COOR). In the illustrated embodiment, The pre-treatment method includes steps of first hydrolyzing ester group (—COOR) comprised in the polyester polymer into carboxyl (—COOH), the carboxyl (—COOH) then being changed into ester (—COO⁻) in a slightly alkaline environment.

At block 202, as shown in FIG. 3, a silver bottom layer 12 is formed on the insulating sheet 10 using a method of vacuum evaporation. Specifically, under a vacuum condition, the insulating sheet 10 is used as a substrate, a metallic silver piece is arranged toward the insulating sheet 10 as a target source. The target source is heated to under a high temperature, the metallic silver piece evaporates to silver ions, and the metal silver ions are gradually deposited on the insulating substrate 10. Silver ions and ester group (—COO⁻) on a surface of the insulating sheet 10 form ionic bonds (—COO—Ag), and such ionic bonds can reach about 150-400 kJ/mole. The silver ions can thus adhere to the insulating sheet 10, and the silver bottom layer 12 is thus formed. The heating method can include resistance heating, electron beam heating, laser beam heating, or plasma spray column heating.

At block 203, as shown in FIG. 4 to FIG. 7, a copper conductive layer 20 is formed on the silver bottom layer 12. One portion of the silver bottom layer 12 is covered by the copper conductive layer 20, and the other portion is exposed by the copper conductive layer 20. In the illustrated embodiment, the copper conductive layer 20 is formed using electroplating method, rather than by a traditional wet etching process. Using an electroplating method to form the copper conductive layer 12 reduces use of copper liquids, and is more environmentally friendly.

A method for forming the copper conductive layer 20 on the silver bottom layer 12 comprises:

Firstly, as shown in FIG. 4, a dry film 14 is formed on the silver bottom layer 22.

Secondly, as shown in FIG. 5 and FIG. 6, the dry film 14 is exposed through a lithographic method to a pattern defined on the copper conductive layer 20. After the step of exposure and development, the dry film 14 then protects the silver bottom layer 12, and the portion of the silver bottom layer 12 exposed by the dry film 14 can be electroplated with a layer of copper (see next step).

Thirdly, as shown in FIG. 7, a copper layer is electroplated onto the silver bottom layer 12, and the layer of copper becomes the copper conductive layer 20, and one portion of the silver bottom layer 12 is covered by the copper conductive layer 20.

Lastly, as shown in FIG. 8, the dry film 14 is removed, and the copper conductive layer 20 is in finished form on the silver bottom layer 12.

At block 204, as shown in FIG. 9, a fast vertical etching method is used to remove the silver bottom layer 12 exposed by the copper conductive layer 20. Only the silver bottom layer 12 sandwiched between the insulating sheet 10 and the copper conductive layer 20 is retained. The silver bottom layer 12 sandwiched between the insulating sheet 10 and the copper conductive layer 20 constitute the silver conductive layer 22. In the illustrated embodiment, the silver bottom layer 12 is etched using an alkaline solution. Using an alkaline solution to fast-etch the silver bottom layer 12 means that etching only takes place along a direction perpendicular to a surface of the insulating sheet 10. Any etching which is done to a side of the copper conductive layer 20 can be ignored, so the reliability of the copper conductive layer 20 is high, and cracks or breaks in the copper conductive layer 20 are reduced.

At block 205, as shown in FIG. 10, a silver covering layer 30 is formed on a top surface and side surfaces of the copper conductive layer 20. That is to say, the copper conductive layer 20 is sandwiched between the silver covering layer 30 and the silver conductive layer 22. The silver conductive layer 22, the copper conductive layer 20 and the silver covering layer 30 together form the conductive wiring layer 40.

The silver covering layer 30 is formed using a sterling silver method. That is to say, in a silver solution, silver ion in the silver solution is replaced with copper comprised in the copper conductive layer 20, namely 2Ag⁺+Cu→2Ag+Cu²⁺. A silver covering layer 30 is gradually formed on the copper conductive layer 20, in this way, a thickness of the conductive wiring layer 40 can be better controlled. A high frequency signal transmission structure 100 is thereby obtained.

The embodiments shown and described above are only examples. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.

Claims

1. A method for manufacturing a high frequency signal transmission structure, comprising:

providing an insulating sheet, evaporating a silver bottom layer on the insulating sheet;

forming a copper conductive layer on part of the silver bottom layer;

removing the silver bottom layer which exposed by the copper conductive layer; and

forming a silver covering layer on the copper conductive layer, and the copper conductive layer is surrounded by the silver bottom layer and the silver covering layer, and the silver bottom layer, the copper conductive layer and the silver covering layer together form a conductive wiring layer.

2. The method of claim 1, wherein the insulating sheet is made from polyester polymer.

3. The method of claim 1, wherein before the step of evaporating a silver bottom layer on the insulating sheet, further comprising a step of pre-treatment to the surface of the insulating sheet.

4. The method of claim 3, wherein a method of the pre-treatment comprising: and the ester group comprised in the insulating sheet is first hydrolyzed into carboxyl, the carboxyl (—COOH) then changed into ester ions (—COO−) in a slightly alkaline environment.

5. The method of claim 2, wherein a method for forming the copper conductive layer comprising:

forming a dry film on the silver bottom layer;

exposing and development the dry film to deform a pattern of the copper conductive layer;

electroplating a copper layer on the silver bottom layer to form the copper conductive layer, and removing the dry film.

6. The method of claim 1, wherein the silver bottom layer of exposed by the copper conductive layer is removed by an etching method using an alkaline solution.

7. The method of claim 1, wherein a thickness of the silver conductive layer is same with a thickness of the silver covering layer.

8. A high frequency signal transmission structure comprising:

an insulating sheet, and

a conductive wiring layer forming on the insulating layer comprising: a silver conductive layer forming on the insulating sheet, a copper conductive layer forming on the silver conductive layer, and a silver covering layer covering a top surface and side surfaces of the copper conductive layer, the silver conductive layer and the silver covering layer together surround the copper conductive layer.

9. The high frequency signal transmission structure of claim 8, wherein a thickness of the silver conductive layer is about 0.1˜2 μm.

10. The high frequency signal transmission structure of claim 8, wherein the insulating sheet is made from polyester polymer.

11. The high frequency signal transmission structure of claim 8, wherein the silver conductive layer is formed on the insulating sheet using vapor deposition method.

12. The high frequency signal transmission structure of claim 8, wherein a thickness of the silver conductive layer is same with a thickness of the silver covering layer.

13. A method for manufacturing a high frequency signal transmission structure, comprising:

providing an insulating sheet, forming a silver bottom layer on the insulating sheet;

forming a copper conductive layer on a surface of the silver bottom layer;

removing the silver bottom layer which exposed by the copper conductive layer; and

forming a silver covering layer on the copper conductive layer, and the copper conductive layer is surrounded by the silver bottom layer and the silver covering layer, and the silver bottom layer, the copper conductive layer and the silver covering layer together form a conductive wiring layer.

14. The method of claim 13, wherein the insulating sheet is made from polyester polymer.

15. The method of claim 13, wherein before the step of evaporating a silver bottom layer on the insulating sheet, further comprising a step of pre-treatment to the surface of the insulating sheet.

16. The method of claim 13, wherein a method of the pre-treatment comprising: and the ester group comprised in the insulating sheet is first hydrolyzed into carboxyl, the carboxyl (—COOH) then changed into ester ions (—COO−) in a slightly alkaline environment.

17. The method of claim 13, wherein a method for forming the copper conductive layer comprising:

forming a dry film on the silver bottom layer;

exposing and development the dry film to deform a pattern of the copper conductive layer;

electroplating a copper layer on the silver bottom layer to form the copper conductive layer, and removing the dry film.

18. The method of claim 13, wherein the silver bottom layer of exposed by the copper conductive layer is removed by an etching method using an alkaline solution.

19. The high frequency signal transmission structure of claim 13, wherein the silver conductive layer is formed on the insulating sheet using vapor deposition method.