KR100993063B1 - Flexible circuit clad laminate - Google Patents

Abstract

In the flexible circuit copper-clad laminate according to the present invention, in the flexible circuit copper-clad laminate comprising a polyimide film, a tie coat layer, a metal seed layer and a metal conductive layer, the oxygen transmission coefficient of the polyimide film is 1410 cm ³ μm / m ² day or less, water content is 2.0% or less, water permeability is 559 cm ³ μm / m ² day or less, the density is characterized in that 1.45g / cm ³ or more.

According to the present invention, a flexible circuit copper-clad laminate having high connection reliability suitable for a use environment of a high-functional digital product can be implemented.

Flexible Printed Circuit Board, Flexible Metal, Sputtering, Polyimide Film

Description

Flexible Circuit Copper Clad Laminates {FLEXIBLE CIRCUIT CLAD LAMINATE}

The present invention relates to a flexible circuit copper-clad laminate, and more particularly, to a flexible circuit copper-clad laminate having improved adhesion using a polyimide film having an optimally controlled oxygen permeability coefficient, moisture content, density, and moisture permeability coefficient. .

The printed circuit is a wiring diagram representing electrical wiring to be connected to a component according to a circuit design. The printed circuit is a printed circuit board (PCB) or a printed wiring board (PC), which is reproduced as an electrical conductor on an insulator by a suitable method. PWB).

The printed circuit board is used for mass production processes because the printed circuit board can be shortened by mounting electronic components at once in a pre-wired board. By using the printed circuit board, there is an advantage that the weight reduction of the electronic device can be realized, and a low production cost and high reliability of wiring can be obtained. Therefore, recent electronic application devices are mostly using printed circuit boards, whether for home use or industrial use.

Recently, miniaturization of printed circuit boards has been required due to the miniaturization of electronic devices such as LCD monitors, PDPs, notebook computers, mobile phones, PDAs, small video cameras, and electronic notebooks. Accordingly, printed circuit boards are made of flexible materials. BACKGROUND OF THE INVENTION The use of flexible printed circuit boards (FPCBs) made of heat-resistant plastic films such as (PET) or polyimide (PI) is increasing. Such flexible printed circuit boards are widely used in small electronic devices and thin electronic components because of flexibility such as bending, overlapping, folding, curling, and twisting.

In order to achieve high-density mounting of electronic devices, circuit boards of this kind are becoming thinner and technologies for forming a metal layer without using an adhesive due to poor adhesion between the plastic substrate and the metal thin film are being investigated. For example, a method of forming a base metal film directly on a plastic substrate by thin film formation techniques such as vacuum deposition, sputtering and ion plating, and then depositing a metal plating layer on the metal film by electroplating or the like is well known.

However, even when the flexible metal laminate is manufactured in the above manner, oxidation of the tie coat layer occurs due to oxygen or moisture infiltration from the polyimide layer, so that the connection strength between the polyimide layer and the copper layer is degraded when the high temperature reliability is evaluated. May occur. Long-term connection reliability is not guaranteed when these problematic flexible metal laminates are used in high voltage equipment.

Accordingly, a method of suppressing oxygen or moisture infiltration by increasing the thickness of the polyimide layer is used, but in this case, there is a problem in that the ductility of the printed board is lowered and the wiring layer breaks during bending.

The present invention was devised to solve the above problems, and by providing optimum control of the oxygen transmission coefficient, water content, density, and water transmission coefficient of the polyimide layer, to provide a flexible circuit copper-clad laminate with high adhesion rate There is this.

The flexible circuit copper-clad laminate according to the present invention for achieving the above technical problem is a flexible circuit copper-clad laminate comprising a polyimide film, a tie coat layer, a metal seed layer and a metal conductive layer, the oxygen transmission coefficient of the polyimide film is 200cm ³ ㎛ / m ² day or more, 1410cm ³ ㎛ / m ² day or less, and the water content is more than 0.5% to 2.0%, the water permeability coefficient is 151cm ³ μm / m ² day or more, 559cm ³ μm / m ^{It is 2} days or less, and the density is 1.45g / cm ³ or more, characterized in that 1.47g / cm ³ or less.

And it is preferable that the said polyimide film is 10 micrometers or more and 50 micrometers or less in thickness.

The tie coat layer is made of a Ni-Cr alloy having a Cr ratio of 3 to 20 wt%, and preferably has a thickness of 50 to 3000 Pa.

The flexible circuit copper-clad laminate according to the present invention prevents the oxidation of the tie coat layer due to oxygen or moisture infiltration from the polyimide layer, thereby improving long-term connection reliability, and thus, for use in an electronic device requiring a high voltage such as a high functional digital product. Suitable for

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a view schematically showing a cross section of a flexible circuit copper clad laminate according to a preferred embodiment of the present invention.

Referring to FIG. 1, the flexible circuit copper-clad laminate according to the present embodiment includes a tie coating layer 20 made of metal, a metal seed layer 30 formed on a tie coating layer 20, and a metal conductive layer on a polymer film 10. Layer 40.

It is preferable that the polymer film 10 has bendability so that it may be suitable for a flexible circuit copper clad laminate, and consists of polyimide films, for example. The polyimide film has high heat resistance, flexibility, and excellent mechanical strength, and has a thermal expansion coefficient similar to that of metal, and thus is widely used as a material of the polymer film 10.

In the present invention, the polyimide film has an oxygen transmission coefficient of 1410 cm ³ μm / m ² day or less, a moisture content of 2.0% or less, a water transmission coefficient of 559 cm ³ μm / m ² day or less, and a density of 1.45 g / cm ³ It is preferable that it is above.

Moreover, in order to apply the flexibility which is one of the characteristics of a polyimide film to the flexible circuit copper clad laminated board of this invention, it is preferable to make thickness of a polyimide film into 50 micrometers or less. The description thereof will be described in detail with reference to experimental examples and comparative examples.

The tie coating layer 20 is vacuum deposited by a sputtering method on the polymer film 10 plane, interposed between the polymer film 10 and the metal seed layer 30 to be deposited on the tie coating layer 20 between the two layers. By connecting the, strengthen the bonding force. Here, the thickness of the tie coating layer 20 coated on the polymer film 10 is preferably 50 to 300 kPa.

 If the thickness of the tie coating layer 20 is too thin, it is vulnerable to high temperatures and poor corrosion resistance, which may be peeled off by the infiltration of the plating liquid after the high temperature treatment or when forming the circuit. In addition, the tie coating layer 20 is interposed between the polymer film 10 and the metal seed layer 30 and is formed to bond the two layers tightly, so it is not necessary to be too thick.

As the material of the tie coating layer 20, a metal having good bonding strength and reactivity with other materials such as chromium or a nickel-chromium alloy is used, but in the present invention, it is preferable that the tie coating layer 20 is a Ni-Cr alloy. In addition, when the tie coating layer 20 is made of a Ni-Cr alloy, when the ratio of Cr in the alloy is less than 3%, the magnetic properties become problematic, and when the amount is 20% or more, 3 to 20 wt. It is preferable that it is%.

As described above, the tie coating layer 20 formed on the polymer film 10 by the vacuum film forming method improves the bonding force between the polymer film 10 and the metal seed layer 30 so that the peel strength is maintained even after high temperature treatment. do.

The metal seed layer 30 is formed on the tie coating layer 20 by performing a sputtering process using a copper or copper alloy target. The metal conductive layer 40 is formed on the plane of the metal seed layer 30 and is formed by using an electroplating method using a plating solution.

On the other hand, the present invention will be described in more detail by explaining more specific examples and comparative examples. However, the present invention is not limited to the following examples and comparative examples, and various forms of embodiments may be implemented within the scope of the appended claims. However, the following examples are intended to facilitate the implementation of the invention to those skilled in the art while at the same time making the disclosure of the present invention complete.

[Production of Polyamic Acid Solution]

A polyamic acid solution can be obtained by polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent.

As the aromatic diamine, para-phenyene diamine, benzidine, 3.4'-diamino diphenyl ether, etc. are used, and pyromellitic acid is used as an acid anhydride component. , 3.3 ', 4.4'-biphenyl tetracarboxylic acid, 2.3'.3.4'-biphenyl tetracarboxylic acid, 3.3'.4.4'-benzophenone tetracarboxylic acid, 2.3.6.7-naphthalene dicarboxylic acid, 2.2- Acid anhydrides such as bis (3.4-dicarboxy phenyl) ether, pyridine2.3.5.6-tetracarbonine and these amide-forming derivatives were used.

 The organic solvent used for the synthesis of the polyamic acid solution may be a sulfoxide solvent such as dimethyl sulfoxide, diethyl sulfoxide, NN-dimethyl formamide, Formamide solvents such as NN-diethyl formamide and solvents such as NN-dimethyl acetamide were used alone or in combination.

In particular, in the present invention, a polyamic acid solution was prepared by reacting DMAC with PPD, 4.4'-ODA, BPDA, and PMDA while stirring at room temperature.

[Production of Polyimide Film]

1) N.N-dimethyl acetamide was added to the polyamic acid solution thus prepared, followed by stirring.

2) After cooling the polyamic acid solution as necessary, the polyamic acid anhydride 8-picoin was mixed to proceed with the imidization of the polyamic acid.

3) After the process of step 2), the obtained polyimide polymer was cast at 90 ° C., the gel film was heated and fixed at 100 ° C., and then stretched at 270 ° C., followed by heat treatment at 380 ° C. To prepare a polyimide film (Polyimide film).

On the other hand, if the process of step 2) is not carried out to partially evaporate the first part of the DMAC at 100 ℃ to prepare a film shape, and then sequentially heated to 270 ℃, 380 ℃ by stretching (stretching) the film while proceeding imidization The mechanical strength of the film was strengthened.

[Manufacture of Flexible Copper Clad Laminates]

The flexible circuit copper-clad laminate was produced by the following procedure using the polyimide film prepared above.

1) Surface treatment of polyimide film.

2) A tie coating layer is formed on the surface-treated polyimide film.

3) Form a metal seed layer on top of the tie coating layer.

4) Form a metal conductive layer on the metal seed layer by electroplating.

[Measurement of peeling strength]

Using the same method as described above, a flexible circuit copper clad laminate sample having the characteristics shown in FIGS. 2 and 3 was prepared, and each sample was subjected to a peel strength test.

In FIGS. 2 and 3, the oxygen permeability coefficient represents the volume of oxygen transmitted through a thickness of 1 μm per square meter per day (ASTM D-3985), and the water content is the maximum moisture content of polyimide (PI) (IPC- TM-650, Meth. 2.6.2), and the water permeation coefficient represents the volume (ASTM E-96) of water (steam) transmitted through a thickness of 1 μm per 1 m 2 per day.

In addition, the peel strength at room temperature is used in accordance with the JIS C 6471 standard, the width of the copper pattern is 1mm, the head speed (Head speed) is pulled at a speed of 50mm / min, the strength is measured by Low Peak Average (Low Peak Average) Was calculated. At this time, the measurement range was 10 to 60 mm.

Similarly, after HTS, the peel strength (kgf / cm) is maintained at 150 ° C and 168hr, and the equipment according to JIS C 6471 standard is used.The width of the pattern is 1mm, the head speed is 50mm / min, and the measurement range is 10 ~. The low peak average was calculated at 60 mm.

2 and 3 are views showing the change in peel strength of the copper clad laminate according to characteristic values such as oxygen transmission coefficient, water content, density, and water transmission coefficient of the polyimide film. When manufacturing the flexible copper clad laminate, if the thickness of the polyimide film, the thickness of the tie coat layer, the composition ratio, etc. are adjusted, as shown in FIGS. 2 and 3, parameters such as oxygen transmission coefficient, water content, density, and water transmission coefficient may be adjusted. It is possible.

2 and 3, when the oxygen transmission coefficient is more than 1410 cm 3 / m 2 day (Comparative Examples 1, 2, 9, 12), there was no change in properties at room temperature peel strength, but the peel strength after HTS was measured The maximum value was below 0.25 kgf / cm. In addition, when the moisture content is more than 2.0% (Comparative Examples 3, 4, 9, 10), there was no change in the properties at room temperature peel strength, but the maximum value was 0.22kgf / cm or less when measuring the peel strength after HTS.

In addition, when the density was 1.45 g / cm 3 or less (Comparative Examples 5, 6, 10, 11), there was no change in properties at room temperature peel strength, but the peel strength after HTS was below 0.18 kgf / cm, which was below the standard value, When the coefficient was 559 cm 3 / m 2 or more (Comparative Examples 7, 8, 11, 12), there was no change in the properties at room temperature peel strength, but the peel strength after HTS was below 0.25 kgf / cm, which was below the standard value.

Therefore, in order to provide excellent peel strength after HTS as well as room temperature peel strength, the oxygen transmission coefficient of the polyimide film constituting the copper clad laminate as in Examples 1 to 36 is 200 cm ³ μm / m ² day or more and 1410 cm ³ μm / m ² day or less, moisture content of 0.5% or more, 2.0% or less, moisture permeability coefficient of 151 cm ³ μm / m ² day or more, 559 cm ³ μm / m ² day or less, density of 1.45 g / cm ³ or more, It can be seen that the 1.47g / cm ³ or less.

4 is a view showing the number of MIT of the copper clad laminate according to the thickness change of the polyimide film. Referring to FIG. 4, when the thickness of the PI (polyimide) film exceeds 50 μm (Comparative Examples 1 to 3), the number of MITs was less than the maximum of 92 times or less. Therefore, in order to have excellent bending characteristics, it can be seen that the thickness of the polyimide film is 10 μm or more and 50 μm or less as in Examples 1 to 5 of FIG. 4.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention includes the matters described in such drawings. It should not be construed as limited to.

1 is a schematic cross-sectional view of a flexible circuit copper clad laminate according to a preferred embodiment of the present invention;

2 and 3 is a view showing the change in peel strength of the copper clad laminate according to the change in the characteristics of the oxygen permeability coefficient, moisture content, density, moisture permeability coefficient of the polyimide film,

4 is a view showing the number of MIT of the copper clad laminate according to the thickness change of the polyimide film.

<Explanation of symbols for main parts of the drawings>

10: polymer film 20: tie coating layer

30 metal seed layer 40 metal conductive layer

Claims (5)

In a flexible circuit copper clad laminate in which a polyimide film, a tie coat layer, a metal seed layer, and a metal conductive layer are sequentially stacked, The polyimide film, And the oxygen permeability coefficient is 200cm ³ ㎛ / m ² day or more, 1410cm ³ ㎛ / m ² day or less, Water content is 0.5% or more and 2.0% or less, Moisture permeability is more than 151cm ³ μm / m ² day, less than 559cm ³ μm / m ² day, A flexible circuit copper clad laminate, characterized in that the density is 1.45g / cm ³ or more, 1.47g / cm ³ or less. The method of claim 1, wherein the polyimide film, A flexible circuit copper-clad laminate, characterized in that the thickness is 10μm or more and 50μm or less. The method according to claim 1 or 2, The tie coat layer, A flexible circuit copper clad laminate, characterized in that consisting of Ni-Cr alloy. The method of claim 3, wherein the Ni-Cr alloy, A flexible circuit copper clad laminate comprising 3 to 20 wt% Cr. The method of claim 3, wherein the tie coat layer, A flexible circuit copper clad laminate, characterized in that the thickness is 50 to 300Å.

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