TWM523255U - Flexible circuit board - Google Patents

Description

Flexible circuit board

This creation is about a flexible circuit board, especially an ultra-thin flexible circuit board.

In printed circuit boards, in order to protect metal lines, a polyimide coverlay is usually placed thereon. With the development of technology and product requirements, the size of printed circuit boards tends to be light, thin, and multi-functional. Reducing the overall thickness of printed circuit boards is also an important development goal of the industry. Among them, the thinning of the polyimide layer has become One of the important indicators of the overall design of printed circuit boards.

Furthermore, the general printed circuit board is formed on a polyimide film to form a circuit, and if the thickness of the polyimide film is too thin (less than 6 micrometers or less), the process capability of the prior art is Unable to achieve, so that the thinness of the printed circuit board is limited.

However, due to the process capability of conventional polyimide membranes, ultra-thin polyimide membranes are indeed difficult to develop. It is known that the thickness of the commercially available thinnest polyimide film can be less than 10 micrometers; however, it is almost impossible to achieve a polyimide film of less than 5 micrometers by the existing biaxial stretching technique. . Moreover, it is also necessary to consider the problem of the operability of the laminating in the downstream application, and the ultrathin polyimide film (below 6 micrometers) when the ultrathin polyimide film (below 6 micrometers) is used as a circuit board. It is impossible to make circuits under the existing process capability, so that the ultra-thin polyimide film can not be used as a circuit board, so that the circuit board can not achieve the requirements of lighter, thinner and shorter.

Accordingly, the present invention has been developed for ultra-thin polyimide films, and when applied to printed circuit boards, circuits can be formed thereon to become ultra-thin printed circuit boards.

The present invention provides a flexible circuit board comprising: a polyimide layer having a first surface and a second surface; and a substrate layer removably attached to the polyimide layer a first surface comprising: a polyimine comprising a main structure of the base layer; and a metal layer forming a second surface of the polyimide layer; the base layer being stripped from the polyimide sheet And become an ultra-thin printed circuit board.

The present invention also provides a flexible circuit board comprising: a polyimide layer having a first surface and a second surface; and a substrate layer removably attached to the polyimide layer a first surface, and comprising a polyimine comprising a main structure of the base layer; a metal layer forming a second surface of the polyimide layer; a protective layer comprising a polyimide layer and a substrate layer is releasably attached to the polyimide layer, the polyimide layer is coated on the polyimide layer having the metal layer; and the substrate layer is peelable from the polyimide layer. And become an ultra-thin printed circuit board.

10‧‧‧ basal layer

12‧‧‧ Polyimine layer

14‧‧‧Low surface energy polymer

16‧‧‧ first surface

18‧‧‧ second surface

20‧‧‧ Polyimine

22‧‧‧metal layer

24‧‧‧Protective layer

26‧‧‧colloid

Figure 1 is a first schematic diagram of the fabrication of the flexible circuit board of the present invention.

Figure 2 is a schematic view of the flexible circuit board of Figure 1.

Figure 3 is a second schematic diagram of the fabrication of the flexible circuit board of the present invention.

Figure 4 is a schematic view of the flexible circuit board of Figure 3.

In an embodiment, please refer to FIG. 1 , the flexible circuit board of the present invention, the package The base layer 10 and the polyimide layer 12 are attached to the polyimide layer 12 in a peelable manner. In this embodiment, a low surface energy polymer 14 may be distributed on the base layer 10 or In the polyimide layer 12, the base layer 10 can be peeled off from the polyimide layer 12, and the polyimide substrate 12 is provided with a first surface 16 and a second surface 18, and the surface of the base layer 10 is in direct contact. The first surface 16 is attached to the surface. In the present embodiment, the base layer 10 comprises: a polyfluorene imine 20 constituting the main structure of the layer and a fluorine-containing polymer 14 having a low surface energy, and the low surface energy fluoropolymer 14 may be in the form of particles and distributed on the substrate layer. In 10, the surface energy is lower than 35 dyne/cm. In another embodiment, the base layer 10 or the polyimide layer 12 may also be a siloxane, that is, a polymer of a siloxane or a polyimide, and the polyimide layer 12 or the substrate 10 is contained. The siloxane is used to lower the surface energy of one of the polyimide layer 12 or the base layer 10 to 35 dyne/cm or less to peel the base layer 10 from the polyimide layer 12.

The polyimide layer 12 has a thickness of 6 microns or less, preferably 5 microns or less, for example, 0.1 to 5 microns. In an embodiment, the polyimide layer 2 may have a thickness of 0.1, 1, 2, 2.5, 3, 4, 4.5 microns, or a value between any two of the foregoing.

The thickness of the base layer 10 is not particularly limited, and the thickness of the conventional base layer can be employed. In some embodiments, the base layer 10 has a thickness of 5 to 10 microns. In some embodiments, the base layer 10 may have a thickness of 10 microns or more.

In the embodiment, the fluorine-containing polymer 14 distributed in the base layer 10 may be, for example but not limited to, fluorocarbons. Specifically, the fluorine-containing polymer includes, for example, a fluorinated polyalkene, a polyalkylene having a fluorine substituent, a polyalkoxy having a fluorine substituent, or a chlorofluorocarbon.

In some embodiments, the fluorine-containing polymer is polyvinyl fluoride (PVF) or polyfluorinated vinylidene (PVDF). Polymer, polytetrafluoroethylene (PTFE), polyfluorinated ethylene propylene (FEP), perfluoropolyether (PEPE), perfluorosulfonic acid (PFSA) polymer, a polymer of perfluoroalkoxy (PFA), a polymer of chlorotrifluoroethylene (CTFE), and a polymer of ethylene chlorotrifuloroethylene (ECTFE), etc. Use or combination.

In the embodiment, the ratio of the fluorine-containing polymer is 45 wt% to 60 wt%, for example, 46, 48, 50, 55, 58 wt%, or the value between any two points based on the total weight of the base layer 10. . In some embodiments, the proportion of the fluorine-containing polymer may be 45 to 55 wt%. In another embodiment, the proportion of the fluorine-containing polymer may be 55 to 60% by weight. In another embodiment, the proportion of the fluorine-containing polymer may be from 47 to 57% by weight.

The fluorine-containing polymer to be used may be in the form of powder, and the fluorine-containing polymer has an average particle diameter of 20 μm or less, for example, 0.5 μm, 1 μm, 2.5 μm, 5 μm, 7.5 μm, 10 μm, 12.5 μm. , 15 μm, 17.5 μm, 19 μm, 20 μm, or a value between any two of the foregoing. In the examples, the fluorine-containing polymer has an average particle diameter of about 5 to 15 μm. In some embodiments, a fluorine-containing polymer having an average particle diameter of 1 to 10 μm may be used, preferably 2 to 8 μm. In other embodiments, a fluorine-containing polymer having an average particle diameter of 11 to 20 μm may be used, preferably 12 to 18 μm. In other embodiments, a fluorine-containing polymer having an average particle diameter of 6 to 15 μm may be used.

Referring to FIG. 2, the low surface energy fluoropolymer 14 is added to the base layer 10 in the present invention to reduce the surface tension of the film, so that the adhesion of the film surface to other layer structures is reduced. In the embodiment, the base layer 10 may have a desired surface tension due to the addition of the fluorine-containing polymer, so that the polyimide layer 12 can be formed on one surface of the base layer 10. another The advantage is that the base layer 10 can be easily removed when the present polyimine layer 12 is applied for subsequent applications, for example, when the metal layer 22 is bonded to prepare a flexible circuit board, for example, the base layer 10 can be directly peeled off. The polyimide layer 12 is completely retained and adhered to the metal layer (e.g., copper foil) 20 without cracking the polyimide layer 12 or separating from the copper foil with the substrate layer 10.

In an embodiment, the substrate layer 10 has a water contact angle greater than 40°, such as 50°, 60°, 75°, 90°, 120°, 150°, 180°, or a value between any two of the foregoing.

In one embodiment, the peel strength between the polyimide layer 12 and the substrate layer 10 is less than 0.15 kgf/cm, for example, 0.14 kgf/cm, 0.12 kgf/cm, 0.10 kgf/cm, 0.05 kgf/cm, Or the value between any two of the foregoing.

In an embodiment, the preparation step of the present invention may include: preparing a base layer 10, wherein the base layer 10 comprises a polyimine 20 constituting a main structure of the base layer and a polymer having a low surface energy distributed therein Applying a polyamic acid solution to one surface of the base layer 10; and heating the polyamic acid solution to form a polyimine layer 12 on the base layer, wherein the base layer 10 is It is peelably attached to the polyimide layer 12. The details are as follows. First, the base layer is prepared, and the desired diamine monomer and the dianhydride monomer are placed in a solvent to form a first polyaminic acid solution, followed by adding a low surface energy polymer 14, which is uniformly mixed and then placed on a glass or stainless steel plate. The upper layer is coated. The base layer 10 is then formed by baking at a temperature of from about 90 ° C to about 350 ° C.

Next, the polyimine layer 12 is prepared, and the desired diamine monomer and the dianhydride monomer are placed in a solvent to form a second polyaminic acid solution, and the monomer used may be the same as the base layer 10, Partially identical or different. Additives such as colorants, matting agents, etc., may be added as needed. The second polyaminic acid solution is coated on the substrate layer to form a layer, and baked at a temperature of about 90 ° C to about 350 ° C. The polyimine layer 12 is formed by baking, and the thickness of the polyimide layer 12 is preferably 5 μm or less, for example, 0.1 to 5 μm.

If necessary, after the formation of the polyimide film (including the base layer 10 and the polyimide layer 12), the biaxial stretching treatment may be further performed, whereby the strength of the polyimide film may be enhanced. Since the thinner the thickness of the polyimide film, the more difficult it is to perform the biaxial stretching treatment. Therefore, it is known that the ultra-thin polyimide film currently commercially available can hardly be biaxially stretched in the process, and the film strength is caused. negative effect. However, since the present polyimine film directly forms the ultrathin polyimide layer 12 on the base layer 10, biaxial stretching treatment may be performed as needed without adversely affecting the film, such as cracking. .

The polyimine film of the present invention can be formed by thermal conversion or chemical conversion. If chemical conversion is employed, the dehydrating agent and catalyst can be added to the polyaminic acid solution prior to the coating step. The solvent, dehydrating agent and catalyst used in the foregoing may be those skilled in the art. The solvent may be an aprotic polar solvent such as dimethylacetamide (DMAC), N,N'-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylene碸 (DMSO), tetramethyl hydrazine, N, N'-dimethyl-N, N'-propenyl urea (DMPU), and the like. The dehydrating agent may be an aliphatic acid anhydride (such as acetic anhydride and propionic anhydride), an aromatic acid anhydride (such as phthalic anhydride and phthalic anhydride), or the like. The catalyst may be a heterocyclic tertiary amine (such as picoline, pyridine, etc.), an aliphatic tertiary amine (such as triethylamine (TEA), etc.), an aromatic tertiary amine (such as xylylene, etc.). Wait. Polylysine: Dehydrating agent: The catalyst has a molar ratio of 1:2:1, i.e., about 2 moles of dehydrating agent and about 1 mole of catalyst per mole of polyamic acid.

In the present invention, a diamine monomer and a dianhydride monomer are subjected to a condensation reaction to form a polyimine, and the diamine and the dianhydride are reacted at a ratio of about equimolar (1:1), for example, 0.9: 1.1, or 0.98: 1.02.

The polyimine 20 which constitutes the main structure of the underlayer 10 and the polyimine 20 of the polyimine layer 12 are not particularly limited.

In an embodiment, the diamine monomer can be 4,4'-diaminodiphenyl ether (4,4'-oxydianiline (4,4'-ODA)), p-phenylenediamine (p-PDA) )), 2,2'-bis(trifluoromethyl)benzidine (TFMB), 1,3-bis(4'-aminophenoxy)benzene ( 1,3-bis(4-aminophenoxy)benzene (TPER), 1,4-bis(4-aminophenoxy)benzene (TPEQ), 4, 4'-Diamino-2,2'-dimethyl-1,1'-biphenyl (2,2'-dimethyl[1,1'-biphenyl]-4,4'-diamine (m-TB- HG)), 1,3-bis(3-aminophenoxy)benzene (1,3'-Bis(3-aminophenoxy)benzene (APBN), 3,5-diaminotrifluorotoluene (3, 5-Diaminobenzotrifluoride (DABTF)), 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) )), 6-amino-2-(4-aminophenyl)benzoxazole (6PBOA), 5-amino-2-(4) -Amino-2-(4-aminophenyl)benzoxazole (5PBOA), etc., may be used singly or in combination.

In an embodiment, the dianhydride monomer may be 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2 -2[2-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (2,2-bis[4-(3,4dicarboxyphenoxy)phenyl]propane dianhydride (BPADA)), pyromellitic acid II Pyromellitic dianhydride (PMDA), 4,4'-(hexafluoroisopropene) diacetic anhydride (2,2'-Bis-(3,4-Dicarboxyphenyl) Hexafluoropropane dianhydride (6FDA)), 4,4-Oxydiphthalic anhydride (ODPA), Benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4' -3,3',4,4'-dicyclohexyltetracarboxylic acid dianhydride (HBPDA), etc., may be used singly or in combination.

In some embodiments, the monomer of the polyimine 20 constituting the main structure of the base layer 10 comprises the following components: the diamine may be 4,4'-diaminodiphenyl ether (4,4'-ODA), Phenylenediamine (p-PDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB), which may be used singly or in combination; the dianhydride may be pyromellitic dianhydride (PMDA), 3, 3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), alone Or use in combination.

In an embodiment, the polyimide layer 12 may use monomers that are identical, partially identical, or different from the substrate layer 10. In some embodiments, the diamine used in the polyimide layer 12 can be 4,4'-diaminodiphenyl ether (4,4'-ODA), p-phenylenediamine (p-PDA), 2 2'-bis(trifluoromethyl)benzidine (TFMB), which may be used singly or in combination; and dianhydride may be pyromellitic dianhydride (PMDA), 3,3', 4,4'-linked Pyromellitic dianhydride (BPDA) and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) may be used singly or in combination.

In another embodiment, referring to FIG. 3, the present invention further provides a protective layer 24, and the protective layer 24 is another polyimide layer 12 to which the base layer 10 is attached, and the first layer of the polyimide layer 12 The two surfaces 18 are coated with a colloid 26, and the protective layer 22 is adhered to the polyimine layer 12 having the metal layer 24 by a colloid 26 for protecting the metal layer 22. Next, see Fig. 4, self-polymerization The base layer 10 is peeled off from the quinone imine layer 12, and if so, another ultra-thin flexible circuit board having the protective layer 22 can be formed.

The present writing is described in detail below by way of examples.

Example

52.63 g of 4,4'-ODA and 440 g of DMAc of the solvent were placed in a three-necked flask. After stirring at 30 ° C until completely dissolved, about 57.37 g of PMDA was added. Among them, the monomer accounts for 20% by weight of the total weight of the reaction solution. Next, the first polyaminic acid solution was obtained by continuously stirring and continuing the reaction at 25 ° C for 20 hours. Add 100 grams of PTFE powder (45% by weight of the total weight of the PI film) to the first polyamic acid solution, and then add acetic anhydride and methylpyridine as a catalyst after stirring (addition ratio of polyamine solution: acetic anhydride) The molar ratio of the methylpyridine was about 1:2:1), the defoaming was applied to a glass plate, and it was placed in an oven at 80 ° C for about 30 minutes to remove most of the solvent. Next, the above-mentioned glass plate coated with the polyaminic acid solution was placed in an oven at 170 ° C and heated for about 1 hour to form the base layer 10.

Next, an ultrathin polyimine plate was prepared in a similar manner. The second polyaminic acid solution can be obtained by reacting 52.63 g of 4,4'-ODA with 57.37 g of PMDA to obtain a percentage of the total weight of the first polyamid acid solution monomer in the total weight of the reaction solution. Baking was carried out on the base layer 10 in an oven at 80 ° C for 30 min. The wet film composed of the base layer 10 and the ultra-thin polyimide substrate 10 was removed and fixed on an extension machine equipped with a needle plate on both sides, and the wet film was biaxially stretched. The original width and length of the wet film are L _0x and L _0y , and the width and length after extension are L _x and L _y , which are calculated by the formulas (L _x -L _0x )/L _0x and (L _y -L _0y )/L _0y The width elongation (ε _x ) and the length elongation (ε _y ), in the present embodiment, ε _x and ε _y are respectively about 40%.

Finally, the biaxially stretched wet film was placed in an oven at 170-350 ° C for 4 hours.

The total thickness of the finally obtained polyimide film was 27.5 μm, wherein the thickness of the base layer was 25 μm, and the thickness of the polyimide sheet was 2.5 μm.

Film performance test

Water contact angle test: The contact angle (DSA10-MK2, Kruss) was measured using the seat drop method. The light is used to illuminate the droplet, which is projected onto the CCD to display the image on the display, and then the built-in analysis software is controlled to calculate the contact angle with an error of ±5°.

Peel strength test: The surface of the ultra-thin polyimide layer was glued and pressed to a copper foil of 18 μm and measured by a universal material testing machine (Hounsfield H10ks) according to the IPC-TM650 2.4.9 method. It was confirmed that the interface of the peeling was between the base layer and the ultrathin polyimide layer.

The polyimine film obtained in the foregoing examples had a water contact angle of 45°; and the peel strength between the ultrathin polyimide layer 12 and the base layer 10 was measured to be 0.14 kgf/cm.

Comparative example 1

The procedure was the same as in the above examples except that the PTFE powder in the first polyaminic acid solution was changed to 42.4 g (30% by weight based on the total weight of the PI film).

The film obtained in Comparative Example 1 had a water contact angle of 32°; and the peel strength test result between the two layers was 0.5 kgf/cm, and the two layers were not easily separated, which was disadvantageous for the step of removing the substrate layer in subsequent applications.

Comparative example 2

The procedure was the same as in the above examples except that the PTFE powder in the first polyaminic acid solution was changed to 231 g (70% by weight based on the total weight of the PI film).

As a result, it was revealed that the second polyaminic acid solution could not be coated on the base layer 10 because the fluorine content of the base layer was too high, so that the surface energy was too low.

In the process of preparing an ultra-thin polyimide layer by a biaxial stretching process, the ultrathin polyimide layer 12 has a minimum thickness of about 10 μm (excluding the substrate layer); and a thickness of less than 10 μm. The process of the amine film is to form a polyimide film, which is then laminated to the PET substrate layer and sold in rolls for subsequent application. Compared with the above-mentioned conventional products and processes thereof, the present invention can form an ultra-thin polyimide layer 12 having a thickness of 5 μm or less directly on the polyimide substrate 10 by using a biaxial stretching process, and can be formed into The film is rolled up directly and sold as a product. Further, the ultrathin polyimide film of the present invention has no influence on the operability of the downstream cloth, and the base layer 10 can be directly and easily removed. Accordingly, the present invention not only reduces the thickness of the film, but also simplifies the process steps, reduces the cost, and facilitates mass production.

The above specific embodiments are intended to describe the present invention in detail, however, these embodiments are for illustrative purposes only and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes or modifications to the present invention are within the scope of the present invention without departing from the scope of the appended claims.

10‧‧‧ basal layer

12‧‧‧ Polyimine layer

14‧‧‧Low surface energy polymer

16‧‧‧ first surface

18‧‧‧ second surface

20‧‧‧ Polyimine

22‧‧‧metal layer

24‧‧‧Protective layer

26‧‧‧colloid

Claims (12)

A flexible circuit board comprising: a polyimide layer having a first surface and a second surface; a substrate layer removably attached to the first surface of the polyimide layer And comprising a polyimine comprising a main structure of the base layer; and a metal layer formed on the second surface of the polyimide layer. The flexible circuit board of claim 1, wherein the base layer or the polyimide layer has a low surface energy of less than 35 dyne/cc. The flexible circuit board of claim 1, wherein the base layer and the polyimide layer have a peel strength of less than 0.15 kgf/cm. The flexible circuit board according to claim 1, wherein the base layer or the polyimide layer has a fluorine-containing polymer having a surface energy of less than 35 dyne/cc, and the fluorine-containing high molecular weight has a thickness of 20 μm or less Average particle size. The flexible circuit board of claim 4, wherein the fluorine-containing polymer is selected from the group consisting of polyvinyl fluoride (PVF), perfluorovinylidene (PVDF) polymer, and polytetrafluoroethylene (PTFE). ), perfluoroethylene propylene (FEP), perfluoropolyether (PEPE), perfluorosulfonic acid (PFSA) polymer, perfluoroalkoxy (PFA) polymer, chlorotrifluoroethylene (CTFE) polymer, And one or more groups of ethylene-chlorotrifluoroethylene (ECTFE) polymers. The flexible circuit board of claim 4, wherein the fluorine-containing polymer is 45 wt% to 60 wt% based on the total weight of the base layer. The flexible circuit board of claim 1, wherein the base layer or the polyimide layer comprises a C-F bond or a decane. A flexible circuit board comprising: a polyimide layer having a first surface and a surface; a substrate layer removably attached to the first surface of the polyimide layer, and comprising a polyimine comprising a primary structure of the base layer; a metal layer formed on the second surface of the polyimide layer; and a protective layer comprising a polyimide layer and a base layer The polyimide layer is peeled off from the polyimide layer, and the base layer is peeled off from the polyimide layer, and the polyimide layer of the protective layer is coated on the polyimide layer having the metal layer. The flexible circuit board of claim 8, wherein the base layer or the polyimide layer has a low surface energy of less than 35 dyne/cc. The flexible circuit board of claim 8, wherein the base layer and the polyimide layer have a peel strength of less than 0.15 kgf/cm. The flexible circuit board of claim 8, wherein the base layer or the polyimide layer comprises a fluorine-containing polymer having a surface energy of less than 35 dyne/cc, and the fluorine-containing polymer has a thickness of 20 μm or less. The average particle size. The flexible circuit board of claim 8, wherein the base layer or the polyimide layer comprises a C-F bond or a decane.