TWI389633B - Base film for flexible printed circuit board, substrate and flexible printed circuit board - Google Patents

Description

Flexible circuit board base film, flexible circuit board substrate and flexible circuit board

The invention relates to a flexible circuit board base film, a flexible circuit board substrate including the flexible circuit board base film, and a flexible circuit board manufactured using the flexible circuit board substrate.

Flexible Printed Circuit Board (FPCB) is widely used in electronic products such as folding mobile phones, print heads and hard disk read heads for relative motion between various working parts. To provide power / signal transmission.

At present, the flexible circuit board gradually turns from a single-layer board to a multi-layer board, and the line density in the circuit layer is also getting higher and higher. See also Takahashi, A. Ooki, N. Naai, A. Akahoshi, H. Mukoh, A. Wajima, M. Res. Lab., High density multilayer printed circuit board for HITAC M-880, IEEE Trans. On Components, Packaging , and Manufacturing Technology, 1992, 15(4): 418-425. At the same time, as the line width of the conductive lines of the high-density flexible circuit board becomes thinner and thinner, the resistance of the line becomes larger and larger, and the amount of heat generated is also increased. Components packaged on the board, such as integrated chips, resistors, etc., generate a lot of heat. In order to ensure the stable operation of the circuit board and electronic components, it is necessary to dissipate the heat generated on the circuit board in time.

At present, a substrate for a flexible circuit board is most commonly used as a flexible copper clad laminate, and the flexible copper clad laminate includes a flexible insulating base film and a conductive copper layer formed on the flexible insulating base film. The flexible base film is generally a polyimine, which has Very good flexural performance, but its thermal conductivity is low. Therefore, the heat in a flexible circuit board made of a general flexible copper clad laminate cannot be quickly dissipated from the flexible circuit board.

Therefore, it is necessary to provide a flexible circuit board base film that can quickly dissipate heat in a circuit board, a flexible circuit board substrate including the flexible circuit board base film, and a flexible circuit board fabricated using the flexible circuit board substrate.

Hereinafter, a flexible circuit board base film, a flexible circuit board substrate including the flexible circuit board base film, and a flexible circuit board fabricated using the flexible circuit board substrate will be described by way of embodiments.

A flexible circuit board base film comprising a flexible polymer substrate and a plurality of carbon nanotubes embedded in the flexible polymer matrix, the carbon nanotubes comprising a first end and a second end, the first end being buried in the Flexible polymer matrix.

A flexible circuit board substrate comprising a flexible circuit board base film and at least one conductive layer formed on the base film of the flexible circuit board. The flexible circuit board base film comprises a flexible polymer substrate and a plurality of carbon nanotubes embedded in the flexible polymer matrix, the carbon nanotubes comprising a first end and a second end, the first end being buried in the flexible polymerization In the body of the substance.

A flexible circuit board comprising a flexible circuit board base film and at least one conductive line formed on the base film of the flexible circuit board. The flexible circuit board base film comprises a flexible polymer substrate and a plurality of carbon nanotubes embedded in the flexible polymer matrix, the carbon nanotubes comprising a first end and a second end, the first end being buried in the flexible polymerization In the body of the substance.

In the flexible circuit board base film, the carbon nanotube can be used as a base film of the flexible circuit board The heat on the surface is quickly transferred to the other surface, so that the heat generated in the flexible circuit board fabricated using the flexible circuit board base film can be quickly dissipated.

Referring to FIG. 1 , it is a schematic structural view of a first embodiment of a flexible circuit board base film provided by the present technical solution. The flexible circuit board base film 100 includes a carbon nanotube array 10 and a flexible polymer matrix 12. The flexible polymer matrix 12 has a first surface 122 and a second surface 124 opposite the first surface 122. The carbon nanotube array 10 includes a plurality of carbon nanotubes 102 that are substantially parallel to each other. Each of the carbon nanotubes 102 extends from the first surface 122 to the second surface 124 but does not expose the second surface 124. Each of the carbon nanotubes 102 includes a first end 103 and a second end 104. The first end 103 is flush with the first surface 122 and the second end 104 is embedded within the flexible polymer matrix 12. The length of the carbon nanotubes 102 is less than the distance between the first surface 122 and the second surface 124, so that when the first end 103 of the carbon nanotube 102 is flush with the first surface 122, the second end 104 cannot reach the second The surface 124, that is, is embedded in the flexible polymer matrix 12. The content of the carbon nanotubes 102 is between 1% and 50%.

The carbon nanotubes 102 can be single-walled carbon nanotubes or multi-walled carbon nanotubes. It can be from 1 micron to 30 microns in length. The flexible polymer matrix 12 is a material suitable for use as a flexible circuit board insulating base film, such as Polyimide (PI), polyethylene terephthalate (PET), and polytetrafluoroethylene. (Polytetrafluoroethylene, PTFE), Polyamide, Polymethylmethacrylate, Polycarbonate (Polycarbonate) or Polyamide polyethylene-terephthalate copolymer.

Since the second end 104 of the carbon nanotube 102 is buried within the flexible polymer matrix 12, when the conductive layer is disposed on the second surface 124, the carbon nanotube 102 is electrically insulated from the conductive layer. Since the flexible polymer between the second surface 124 and the second end 104 of the carbon nanotube 102 is relatively thin, heat generated at the second surface 124 of the flexible polymer substrate 12 can be rapidly transferred to the carbon nanotube 102. The two ends 104, while the carbon nanotubes 102 have a very high thermal conductivity in the radial direction, so heat can be quickly transferred from the second end 104 of the carbon nanotubes 102 to the first end 103 of the carbon nanotubes 102. That is, heat can be quickly transferred from the second surface 124 of the flexible polymer substrate 12 to the first surface 122. When the second surface 124 is packaged with electronic components, the heat emitted by the electronic components can be dissipated in time. And since the direction of the carbon nanotubes 102 is substantially perpendicular to the first surface 122 and the second surface 124, and the content of the carbon nanotubes 102 is between 1% and 5%, the carbon nanotube array 10 does not affect the flexible circuit. The flexural properties of the base film 12 of the board.

In the present embodiment, the carbon nanotubes 102 are arranged in an array, however, it is understood that the plurality of carbon nanotubes 102 are randomly distributed over a range of angles, such as each of the carbon nanotubes 102 and the first surface 122 or the second surface. The angle between 124 is between 1 and 10 degrees.

Referring to FIG. 2, the flexible circuit board base film 200 of the second embodiment includes a carbon nanotube array 20 and a flexible polymer substrate 22. The flexible polymer matrix 22 has a first surface 222 and a second surface 224 opposite the first surface 222. The carbon nanotube array 20 includes a plurality of carbon nanotubes 202 that are substantially parallel to each other. each The root carbon nanotubes 202 are both embedded at both ends of the flexible polymer matrix 22 and are substantially perpendicular to the first surface 222 or the second surface 224. Both ends of the carbon nanotube 202 are buried in the flexible polymer substrate 22. When the conductive layer is disposed on the first surface 222 and the second surface 224, the carbon nanotube array 20 is electrically insulated from the conductive layer.

Referring to FIG. 3, a method for fabricating the flexible circuit board base film 100 of the first embodiment will be described below by way of an embodiment, the method comprising the following steps:

In the first step, referring to FIG. 4, a sacrificial layer 30 is provided. The sacrificial layer 30 may be a metal layer such as a copper layer, an aluminum layer or a nickel layer. The sacrificial layer 30 may have a thickness of from 2 micrometers to 200 micrometers.

In the second step, a catalyst layer 32 is formed on the sacrificial layer 30. Referring to FIG. 5, first, a catalyst film 31 is formed on the sacrificial layer 30. The catalyst film 31 may be iron, cobalt, nickel or an alloy. When the catalyst film 31 is formed, plating, vapor deposition, sputtering, or vapor deposition may be employed. Referring to Figure 6, the catalyst film 31 is then oxidized to form a catalyst layer 32 comprising a plurality of catalyst particles.

In the third step, referring to FIG. 7, the carbon nanotube array 10 is grown on the catalyst layer 32. The sacrificial layer 30 formed with the catalyst layer 32 is placed in a reaction furnace, and a carbon source gas is introduced at 700 to 1000 degrees Celsius to grow a carbon nanotube array 10, wherein the carbon source gas may be a gas such as acetylene or ethylene. The height of the carbon nanotube array 10 can be controlled by controlling the growth time, and the growth height is generally 1 to 30 μm. The method for growing the carbon nanotube array 10 is relatively mature. For details, see Science, 1999, 283, 512-414 and J. Am. Chem. Soc, 2001, 123, 11502-11503, and US Patent No. 6,350, 488. Disclosed a large area for growth The method of carbon nanotube arrays.

In a fourth step, referring to Figure 8, a flexible polymer matrix 12 is formed. First, a solution of a flexible polymer precursor or a flexible polymer precursor is applied to the carbon nanotube array 10 by dip coating, coating, pressing or casting, and the flexible polymer precursor is sufficiently filled with a carbon nanotube array. The gap between the 10 carbon nanotubes 102 is such that the flexible polymer precursor coats the carbon nanotube array 10. The flexible polymer precursor may be Polyimide (PI), Polyethylene Terephtalate (PET), Polytetrafluoroethylene (PTFE), Polyamide (Polyamide). ), Polymethylmethacrylate, Polycarbonate, Polyethylene Terephtalate (PET) or Polyimide-Polyethylene-terephthalate copolymerization Prepolymer or solution of Polyamide polyethylene terephthalate copolymer. The flexible polymer precursor is then cured to form a flexible polymer matrix 12. After the flexible polymer matrix 12 is formed, the second end 104 of the carbon nanotube 102 is embedded within the flexible polymer matrix 12. The curing method may be a baking method, the solvent in the flexible polymer precursor is removed, and the flexible polymer precursor is cross-linked, thereby obtaining a flexible circuit board base film composited with the carbon nanotube and the flexible polymer. 100.

In the fifth step, referring to FIG. 9, the sacrificial layer 30 and the catalyst layer 32 are removed to obtain the flexible circuit board base film 100. The first end 103 of the carbon nanotube 102 is flush with the first surface 122 of the flexible circuit board base film 100. Removing the sacrificial layer 30 and the catalyst layer 32 can be etched. For example, when copper is used as the sacrificial layer, and ferric oxide is used as the catalyst layer 32, the wet etching used in the current circuit board can be used to etch copper, that is, copper and ferric oxide are etched with a ferric chloride solution. Of course, when using other sacrificial layers and catalyst layers, the corresponding etchant can be used.

The flexible circuit board base film 200 is fabricated in a similar manner to the above method, except that a flexible polymer precursor is further applied to the first surface 122 of the flexible circuit board base film 100 and cured, so that a flexible circuit board base can be obtained. Film 200. Each of the carbon nanotubes 202 in the flexible base film 200 is embedded in the flexible base film 22 and is substantially perpendicular to the first surface 222 or the second surface 224.

Hereinafter, a flexible circuit board substrate including the above-described flexible circuit board base film will be described by way of embodiments.

Referring to FIG. 10, the flexible circuit board substrate 400 includes a flexible circuit board base film 100 and a conductive layer 42 formed on the flexible circuit board base film 100. Specifically, the conductive layer 42 is formed on the second surface 124 of the flexible circuit board base film 100. The conductive layer 42 is preferably copper, but other metals having high conductivity such as silver, aluminum, or the like may be used. The conductive layer 42 may be formed on the flexible circuit board base film 100 by plating or press bonding. Conductive layer 42 can have a thickness from 1 micron to 50 microns.

Referring to FIG. 11, the flexible circuit board substrate 500 includes a flexible circuit board base film 200 and conductive layers 52 respectively formed on opposite surfaces of the flexible circuit board base film 200. Since the two ends of the carbon nanotube array 20 are buried in the flexible polymer substrate 22 in the flexible circuit board base film 200, the flexible circuit board can be used. A conductive layer 52 is formed on both surfaces of the base film 200.

Referring to FIG. 12, the flexible circuit board 600 includes a flexible circuit board base film 100 and conductive traces 44 formed on the flexible circuit board base film 100.

The flexible circuit board 600 can be fabricated by the following methods:

First, a flexible circuit board substrate 400 is provided. The flexible circuit board substrate 400 includes a flexible circuit board base film 100 and a conductive layer 42 formed on the flexible circuit board base film 100.

Next, the conductive layer 44 is etched by a usual etching process to form the conductive wiring 44, and the flexible circuit board 600 can be obtained.

The etching process generally includes three steps of applying photoresist, exposing, developing, etching, and removing the film. Applying a photoresist means applying a layer of photoresist on the conductive layer 42. Exposure refers to selectively exposing the photoresist applied to the conductive layer 42 by a photomask to cure or decompose the photoresist of the exposed portion; The development means that the exposed flexible circuit board substrate 400 is immersed in the developing solution, and the uncured photoresist or the decomposed photoresist is dissolved in the developing solution to form a patterned protective layer on the conductive layer 42; The conductive layer 42 is etched by an etchant to form a conductive line 44, and the conductive layer 42 is not etched away from the photoresist; the film removal means that the photoresist on the conductive line 44 is removed to expose the conductive line 44. .

The flexible circuit board 600 obtained in this embodiment is a single-layer circuit board, that is, has a conductive circuit. It can be understood that the flexible circuit board substrate 500 can be used to form a double-layer circuit board by one etching, that is, two flexible circuit board base films. Conductive lines are formed on the surface. Of course, the flexible circuit board base film and the flexible circuit board substrate can be used to fabricate the multilayer flexible circuit board.

First, referring to FIG. 13, a two-layer flexible circuit board substrate 400 and a flexible circuit board base film 200 are provided. Next, referring to FIG. 14, the two flexible circuit board substrates 400 are respectively pressed onto the opposite surfaces of the flexible circuit board base film 200, so that the opposite surfaces of the flexible circuit board base film 200 and the two flexible circuit board substrates 400 are respectively The flexible circuit board base film 100 is attached. Finally, referring to FIG. 15, a conductive line 701 is formed on the conductive layer 42 of the two-layer flexible circuit board substrate 400, thereby obtaining a flexible circuit board 700. In the present embodiment, a flexible circuit board substrate 400 having a conductive layer formed on one side thereof is used to form a multilayer flexible circuit board 700 having two layers of wiring. Of course, it is also possible to form a layer of flexible circuit boards by layering.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. 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.

100,200‧‧‧Flexible circuit board base film

10,20‧‧‧Nano Carbon Tube Array

102,202‧‧‧Nano carbon tube

103‧‧‧ first end

104‧‧‧ second end

12,22‧‧‧Flexible polymer matrix

122, 222‧‧‧ first surface

102,224‧‧‧second surface

30‧‧‧sacrificial layer

31‧‧‧ Catalyst film

32‧‧‧catalyst layer

400,500‧‧‧Flexible circuit board substrate

42,52‧‧‧ Conductive layer

44‧‧‧Electrical circuit

600,700‧‧‧Flexible circuit board

1 is a cross-sectional view showing a first embodiment of a flexible circuit board base film provided by the present technical solution.

2 is a cross-sectional view showing a second embodiment of a flexible circuit board base film provided by the present technical solution.

3 is a flow chart of a method for fabricating a first embodiment of a flexible circuit board base film provided by the present technical solution.

4-9 is a schematic view showing a manufacturing method of a first embodiment of a flexible circuit board base film provided by the technical solution.

FIG. 10 is a cross-sectional view showing a first embodiment of a flexible circuit board substrate provided by the present technical solution.

11 is a cross-sectional view showing a second embodiment of a flexible circuit board substrate provided by the present technical solution.

12 is a cross-sectional view showing a first embodiment of a flexible circuit board provided by the present technical solution.

13-15 are schematic diagrams showing a manufacturing method of a second embodiment of a flexible circuit board provided by the technical solution.

100‧‧‧Flexible circuit board base film

10‧‧‧Nano Carbon Tube Array

102‧‧‧Nano Carbon Tube

103‧‧‧ first end

104‧‧‧ second end

12‧‧‧Flexible polymer matrix

122‧‧‧ first surface

102‧‧‧ second surface

Claims (20)

A flexible circuit board base film comprising a flexible polymer substrate and a plurality of carbon nanotubes embedded in the flexible polymer matrix, the carbon nanotubes comprising a first end and a second end, the first end being buried in the Flexible polymer matrix. The flexible circuit board base film of claim 1, wherein the plurality of carbon nanotubes form an array of carbon nanotubes. The flexible circuit board base film of claim 2, wherein the flexible polymer substrate comprises a first surface and a second surface opposite to the first surface, the plurality of carbon nanotubes and the first surface or The second surface is substantially vertical. The flexible circuit board base film of claim 3, wherein the second end is flush with the first surface or the second end is also buried in the flexible polymer matrix. The flexible circuit board base film of claim 3, wherein the carbon nanotube length is less than a distance between the first surface and the second surface. The flexible circuit board base film of claim 1, wherein the carbon nanotube has a length of from 1 micrometer to 30 micrometers. The flexible circuit board base film according to claim 1, wherein the flexible circuit board substrate is polyimide, polyethylene terephthalate, polytetrafluoroethylene, polythioamide, poly Methyl methacrylate, polycarbonate, polyethylene terephthalate or polyamidene-polyethylene-p-xylylene ester copolymer. A flexible circuit board substrate comprising a flexible circuit board base film and at least one conductive layer formed on the base film of the flexible circuit board, the flexible circuit board base film comprising a flexible polymer substrate and embedded in the flexible polymer matrix a plurality of carbon nanotubes, the carbon nanotube comprising a first end and a second end, the first end Buried in the flexible polymer matrix. The flexible circuit board substrate of claim 8, wherein the plurality of carbon nanotubes form an array of carbon nanotubes. The flexible circuit board substrate of claim 9, wherein the flexible polymer substrate comprises a first surface and a second surface opposite to the first surface, the plurality of carbon nanotubes and the first surface or The two surfaces are substantially vertical. The flexible circuit board substrate of claim 10, wherein the second end is flush with the first surface or the second end is also buried in the flexible polymer matrix. The flexible circuit board substrate of claim 10, wherein the carbon nanotube length is less than a distance between the first surface and the second surface. The flexible circuit board substrate of claim 8, wherein the carbon nanotube has a length of from 1 micrometer to 30 micrometers. A flexible circuit board comprising a flexible circuit board base film and at least one conductive circuit formed on the base film of the flexible circuit board, the flexible circuit board base film comprising a flexible polymer substrate and a plurality of embedded in the flexible polymer matrix The carbon nanotube includes a first end and a second end, the first end being buried in the flexible polymer matrix. The flexible circuit board of claim 14, wherein the plurality of carbon nanotubes form an array of carbon nanotubes. The flexible circuit board of claim 15, wherein the flexible polymer substrate comprises a first surface and a second surface opposite to the first surface, the plurality of carbon nanotubes and the first surface or the second The surface is basically vertical. The flexible circuit board of claim 16, wherein the second end is flush with the first surface or the second end is also buried in the flexible polymer matrix. The flexible circuit board of claim 16, wherein the carbon nanotube length is less than a distance between the first surface and the second surface. The flexible circuit board of claim 14, wherein the carbon nanotube has a length of from 1 micrometer to 30 micrometers. The flexible circuit board of claim 14, wherein the flexible circuit board substrate is polyimide, polyethylene terephthalate, polytetrafluoroethylene, polysulfide, polymethyl Methyl acrylate, polycarbonate, polyethylene terephthalate or polyamidene-polyethylene-p-xylylene ester copolymer.