JP6365699B2 - Method for producing metallized polyimide film substrate - Google Patents

Description

  The present invention relates to a method for determining adhesion strength between a metal thin film and a polyimide film in a metallized polyimide film substrate, and a metallized polyimide film substrate using a polyimide film screened by the determination method.

  A metallized polyimide film substrate is mainly a laminate of copper foil and polyimide film using an adhesive. This metallized polyimide film substrate is used as a flexible printed wiring board and widely used as a wiring material in electronic equipment.

  In recent years, as electronic parts have become lighter, thinner and shorter, there is an increasing demand for narrow pitch wiring, and the demand for metalized polyimide film substrates is also demanded of a substrate that can draw fine wiring, and there is no adhesive layer. Was developed. This is because the absence of the adhesive layer does not affect the characteristics of the adhesive layer, and wiring processing with a narrow pitch is possible.

  As a method of obtaining a metalized polyimide film substrate without an adhesive layer, a metal layer is directly laminated on the polyimide film surface by sputtering and vapor deposition, and then the metal layer is thickened by electroplating or electroless plating. There is a way to do it. Generally, as in Patent Documents 1 and 2, a polyimide film is plasma-treated to improve the adhesion between the metal layer and the polyimide film. However, this method has many inconveniences such as easy wrinkling, and if a substrate having the same degree of adhesion can be obtained without plasma treatment, it is advantageous in terms of process stability and cost.

  However, when no adhesive is used and no plasma treatment is performed, the adhesion between the metal layer and the polyimide film is greatly influenced by the surface properties of the polyimide film. Further, the surface physical properties of the polyimide film easily vary due to the influence of the air flow in the manufacturing process. Due to this factor, the adhesion of the metallized polyimide film substrate varies.

  On the other hand, Non-Patent Documents 1 and 2 report factors contributing to adhesion between metal and polyimide.

JP 2002-252257 A JP 2003-334890 A

Maeda Shigeyoshi, J.M. Jpn. Soc. Color Mater. , 80 (1), 26-31 (2007) Maeda Shigeyoshi, J.M. Jpn. Soc. Color Mater. , 80 (1), 68-74 (2007)

  As described above, a metallized polyimide film substrate without an adhesive layer is manufactured, but the adhesive strength is lower than that of a three-layer material FCCL having an adhesive layer, and the adhesive strength varies depending on the polyimide film raw material. The measuring method of the adhesive strength is defined in JIS C 6471 8.1 (copper peel strength) normal method A. Therefore, there is a demand for a metallized polyimide film substrate that manages the surface physical properties of the raw material polyimide film and has stable adhesion.

  Therefore, the objective of this invention is to provide the board | substrate which shows the high adhesive force by managing the surface physical property of the polyimide film which has a correlation with adhesiveness, and using the polyimide film with the high physical property.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the orientation of molecular chains on the extreme surface of the polyimide film has an effect on the adhesion of the substrate, thereby completing the present invention.

  Specifically, the present invention provides the following.

  (1) In a metal thin film / polyimide laminate in which a metal thin film is laminated on the polyimide film surface, the orientation of molecular chains on the pole surface on the laminate surface side of the polyimide film before the metal thin film / polyimide laminate is laminated When the ratio of the maximum X-ray intensity / minimum X-ray intensity, which is the in-plane anisotropy of the X-ray intensity, is 1.05 to 1.40, A step of determining that the adhesion strength between the metal thin film and the polyimide film is good, and an electroplating method, an electroless plating method or both on the metal thin film of the metal thin film / polyimide laminate having the adhesion strength determined to be good. And a step of laminating copper by a method combining the above, and a method for producing a metallized polyimide film substrate.

  (2) The method for producing a metallized polyimide film substrate according to (1), wherein the metal is one or more selected from nickel, copper, and chromium.

  (3) The method for producing a metalized polyimide film substrate according to (1) or (2), wherein the metal thin film is laminated on the surface of the polyimide film by vapor deposition or sputtering.

  (4) The method for producing a metallized polyimide film substrate according to any one of (1) to (3), wherein a surface on the lamination surface side in the polyimide film before lamination is untreated.

  According to this invention, the polyimide film which improves the adhesive strength with a metal thin film can be screened, and, thereby, the metallized polyimide film board | substrate with high adhesive strength with a metal thin film and a polyimide film can be obtained.

It is a figure which shows the GIXD spectrum in Example 3. It is a figure which shows the GIXD spectrum in the comparative example 1. It is a figure which shows the GIXD spectrum in the comparative example 3.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

  The metalized polyimide film substrate that does not require an adhesive layer is formed by forming a primary metal layer such as nickel, chromium, copper, or an alloy thereof by a dry method using a vapor deposition method or a sputtering method, followed by an electroplating method. Or the copper layer which is a secondary metal layer is thickened using the electroless-plating method and the method which combined both. Usually, the primary metal layer has a thickness of several angstroms to several thousand angstroms, and the secondary metal layer has a thickness of several μm to several hundreds of μm. Each process moves the inside of a cell and laminate | stacks a metal layer, conveying a film at several m-several dozen m / min.

  At this time, the physical properties of the surface of the polyimide film are greatly involved in the adhesion of the metalized polyimide film substrate. According to the present invention, when the orientation of the molecular chain on the surface of the polyimide film is within a predetermined range, a metallized polyimide film substrate showing adhesion is obtained.

  Here, the polyimide film pole surface is a depth of several tens of nanometers from the surface, and cannot be measured by a normal X-ray diffraction method. In order to measure the orientation of the molecular chain in this region, it is necessary to measure by a grazing incident X-ray diffraction (abbreviated as GIXD) or the like. Since the critical angle is about 0.15 degrees in polyimide, it is necessary to make X-rays incident below this angle. In addition, when the sample has unevenness of several tens of nm or more, the X-rays penetrate into a region deeper than the extreme surface, and thus the unevenness of the sample is required to be several tens of nm or less. When the sample is fixed to the apparatus, it is necessary to fix the sample smoothly.

  In GIXD measurement, information on the bulk crystal state is first obtained by X-ray diffraction by a normal transmission method. Next, an X-ray diffraction profile in which X-rays are incident at a critical angle or less is obtained. Comparing the X-ray profiles of the bulk and the pole surface, and if there is a diffractive surface peculiar to the pole surface, the detector was fixed to 2θ (theta) of the diffractive surface and X-ray diffraction was performed below the critical angle φ ( Phi: Phi) By scanning, the X-ray diffraction intensity of the film pole surface can be obtained. On the other hand, when there is no X-ray diffraction peak peculiar to the pole surface, φ scan data can be obtained by fixing the detector to 2θ of the target diffraction surface and performing the same measurement as described above. From the obtained φ scan data, the diffraction intensity is read, and the convex value (maximum X-ray intensity) / concave value (minimum X), which is the ratio of the peak convex part (maximum X-ray intensity) to the concave part (minimum X-ray intensity). The molecular chain orientation is determined by calculating the (linear intensity).

  In GIXD measurement, X-rays are incident on the film at about 0.15 degrees, so that the X-rays spread over several centimeters on the film. Therefore, the film needs to have a certain degree of smoothness over several centimeters, and is sampled to a large extent with a margin when cutting. This is particularly important for φ scans that rotate the film 360 degrees. When performing φ scan with GIXD measurement, if the film is cut into a rectangle, even if X-rays extending in the long side direction do not protrude from the film, the short side direction may protrude from the extended irradiation range. Come on. When the spread X-rays protrude from the film, the intensity of the detected X-rays inevitably decreases. For this reason, it is preferable that the film used for φ scan is sampled in a circular shape instead of a rectangular shape.

  In general, a stretched film has in-plane anisotropy in the MD direction, which is the flow direction at the time of manufacture, and the TD direction, which is the width direction in the manufacture. The strength / concave value (minimum X-ray intensity) often corresponds to either the MD direction / TD direction or the TD direction / MD direction depending on the production method (stretching method).

  In the present invention, the adhesion strength is determined to be good when the ratio of the maximum X-ray intensity / minimum X-ray intensity, which is the in-plane anisotropy of the X-ray intensity, is 1.05 to 1.40. More preferably, it is the range of 1.08 to 1.22. The polyimide film whose molecular chain orientation on the extreme surface is within the above range is highly amorphous because the molecular chains on the extreme surface are evenly scattered on the film surface, resulting in adhesion to metal. It is thought that became higher. On the other hand, molecular chains of the polyimide film exceeding 1.40 are pulled, and it is considered that the adhesion to the metal is lowered as a result of the stretching being too strong and the crystallinity being increased. On the other hand, although the reason is not clear, the adhesion strength also decreases when it is less than 1.05.

  The polyimide film obtained by the above screening provides a metallized polyimide film substrate having a high adhesion strength of 660 N / m or more, preferably 700 N / m or more as adhesion strength. Here, the adhesion strength is a measured value obtained by the above-described JIS C 6471 8.1 (copper peel strength) normal method A.

  In the polyimide film used in the present invention, the laminated surface of the metal thin film is preferably untreated, but may be subjected to plasma treatment or corona treatment. Here, untreated means that plasma treatment, corona treatment, primer treatment or the like has not been performed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.

[Production of metallized polyimide film substrate]
<Example 1>
As a polyimide film, 38 μm of Kapton (registered trademark) 150EN (manufactured by Toray DuPont) was used, and heat treatment was performed at 150 ° C. for 1 minute in a chamber maintained at a vacuum degree of 0.01 to 0.1 Pa. This polyimide film is untreated on the laminated surface.

  Subsequently, a nickel-chromium alloy target containing 20% by mass of chromium and a copper target were used to form a nickel-chromium alloy layer having a thickness of 20 nm and a copper layer having a thickness of 100 nm on the polyimide film surface.

  Thereafter, 180 g / L of sulfuric acid, 80 g / L of copper sulfate, 50 mg / L of chloride ions, and a plating solution added with a predetermined amount of organic additives for the purpose of ensuring the smoothness of the copper plating film, etc. A copper film was formed by electroplating to a thickness of 8 μm under the above plating conditions.

  As described above, the metallized polyimide film substrate according to the embodiment of the present invention has a structure of a sputtered metal thin film 20 nm composed of nickel, chromium and copper, a sputtered copper thin film 100 nm, and a copper plating film 8 μm on a polyimide film 38 μm. A laminate was obtained.

<Examples 2 to 5, Comparative Examples 1 to 3>
The polyimide film of Example 1 is the same as Example 1 except that various polyimide films having different manufacturing methods and lots were used, and the metalized polyimide film substrates of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained. It was.

[Adhesion strength measurement]
Adhesion strength measurement conditions: JIS C 6471 8.1 (copper peel strength) normal state Evaluation was made by method A. The results are shown in Table 1.

[Evaluation of molecular orientation on the surface of polyimide film]
The raw material polyimide film used in the examples and comparative examples was sampled into a circular shape having a diameter of 10 cm so that the surface was not contaminated in an untreated state before the copper-clad laminate was processed. Vaseline was applied to the flat glass and the film was adhered and fixed smoothly and then subjected to GIXD measurement under the following conditions.

  The results are shown in Table 1. 1 to 3 show Example 3 (the ratio of maximum X-ray intensity / minimum X-ray intensity is 1.20) and Comparative Example 1 (the ratio of maximum X-ray intensity / minimum X-ray intensity is 1.00, respectively). ), A GIXD spectrum of the sample of Comparative Example 3 (the ratio of maximum X-ray intensity / minimum X-ray intensity is 2.00). The vertical dotted lines in FIGS. 1 to 3 alternately represent the maximum X-ray intensity and the minimum X-ray intensity, and the maximum X-ray intensity and the minimum X-ray intensity are obtained by smoothing the GIXD spectrum. is there.

(measuring device)
D8 DISCOVER μ-HR (manufactured by Bruker AXS) was used.
(Measurement condition)
Using CuKα, the voltage and current were set to 50 kV-22 mA. A zero-dimensional detector (scintillation counter) was used as the detector.
(Measuring method)
The surface scattering intensity was measured while changing the incident angle of X-rays, and the point (critical angle) at which the scattering intensity changed rapidly was experimentally determined. In the case of this polyimide, it was around 0.15 degree. An in-plane measurement was performed by rotating the 2θχ axis called the in-plane axis to obtain a “φ-2θχ” profile. Based on this profile, the detector is fixed at the peak of the (002) plane (about 5 degrees), which is a typical diffraction surface of polyimide, and the film is rotated to scan the Data indicating orientation was obtained.

  From the results of Table 1 and FIGS. 1 to 3, when the ratio of the maximum X-ray intensity / minimum X-ray intensity in the GIXD spectrum of the polyimide film pole surface is within the range of the present invention, the adhesion is high. It can be seen that the adhesion is reduced both outside the upper and lower limits.

  The metallized polyimide film substrate of the present invention can be suitably used for a flexible printed wiring board, for example.

Claims (4)

In a metal thin film / polyimide laminate in which a metal thin film is laminated on the surface of the polyimide film, the orientation of molecular chains on the polar surface on the lamination surface side of the polyimide film before the metal thin film / polyimide laminate is laminated When the ratio of the maximum X-ray intensity / minimum X-ray intensity, which is an in-plane anisotropy of the X-ray intensity, is measured by using an angle incident X-ray diffraction method, Determining the adhesion strength with the polyimide film as good,
A step of laminating copper on the metal thin film of the metal thin film / polyimide laminate determined to have good adhesion strength by electroplating, electroless plating, or a combination of both, and a metallized polyimide film A method for manufacturing a substrate. The method for producing a metallized polyimide film substrate according to claim 1, wherein the metal is one or more selected from nickel, copper, and chromium. The method for producing a metallized polyimide film substrate according to claim 1 or 2, wherein the metal thin film is laminated on the surface of the polyimide film by vapor deposition or sputtering. The method for producing a metallized polyimide film substrate according to any one of claims 1 to 3, wherein a surface on the lamination surface side of the polyimide film before lamination is untreated.

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