JP2011031603A - Metalized polyimide film, flexible wiring board, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metalized polyimide film having an initial adhesion strength of 900 N/m or larger and an adhesion strength of 600 N/m or larger after a PCT test, and also to provide a method for manufacturing a flexible wiring board using the same. <P>SOLUTION: In the metalized polyimide film where a metal film is directly provided on the surface of a polyimide film by a plating method, the polyimide film has an oxygen permeability of 300 to 500 cm<SP>3</SP>/m<SP>2</SP>/24 h and also a water absorption rate of 1 to 3%. In the flexible wiring board, a wiring pattern of the metal film is provided on the surface of the polyimide film having a thermal expansion coefficient of 10 to 18 ppm/°C, and the polyimide film contains imido bonding formed by biphenyltetracarboxylic acid and a diamine compound in a polyimide molecule. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a metallized polyimide film, a flexible wiring board, and a method for producing them, and more specifically, a metallized polyimide having an initial adhesion strength of 900 N / m or more and an adhesion strength of 600 N / m or more after a PCT test. The present invention relates to a film, a flexible wiring board, and a manufacturing method thereof.

  The board on which these electronic components are formed by forming an electronic circuit is a rigid plate-like “rigid wiring board” and a film-like, flexible “flexible wiring board” (hereinafter referred to as FPC). May be called). Of these, FPCs can be used in flexible parts such as LCD driver wiring boards, hard disk drives (HDD), digital versatile disk (DVD) modules, and mobile phone hinges by taking advantage of their flexibility. Therefore, the demand is increasing more and more.

By the way, such a flexible wiring board uses a base material in which a metal layer is provided on the surface of a polyimide film, and the wiring is obtained by processing the metal layer by a subtractive method or a semi-additive method. Incidentally, in the case of obtaining a flexible wiring board by the subtractive method, first, a resist layer is provided on the surface of the metal layer of the base material, a mask having a predetermined wiring pattern is provided on the resist layer, and from there An exposure mask is exposed to ultraviolet light, developed, and developed to obtain an etching mask for etching the metal layer. Then, the exposed metal portion is removed by etching, then the remaining resist layer is removed, washed with water, and washed. In this case, a predetermined plating is applied to the lead terminal portion of the wiring.
In the case of obtaining by the semi-additive method, a resist layer is provided on the metal surface of the substrate, a mask having a predetermined wiring pattern is provided on the resist layer, and ultraviolet rays are irradiated from above to be exposed and developed. A plating mask for electrodepositing copper on the surface of the metal layer is obtained, and the wiring layer is formed by electroplating using the metal layer exposed in the opening as a cathode, and then the resist layer is removed and soft etching is performed. Then, the metal layer on the surface of the substrate other than the wiring part is removed to complete the wiring part, washed with water, and if necessary, obtained by performing predetermined plating on the lead terminal part of the wiring.

Currently, liquid crystal displays (hereinafter sometimes referred to as LCDs), mobile phones, digital cameras, and various electrical devices are required to be thin, small, light, and low in cost, and electronic components mounted on them. However, as a matter of course, the trend toward miniaturization is progressing. As a result, the wiring pitch of the flexible wiring board used has been required to be 25 μm or less. In the wiring board for driver of LCD, finer wiring pitch is remarkable, and COF (Chip on film) tape is an example of one aspect of FPC.
In order to meet this requirement, when trying to obtain a flexible wiring board with a wiring pitch of 25 μm, when the wiring is obtained by the subtractive method, the influence of side etching at the time of wiring preparation is eliminated, and the cross section is rectangular. In order to obtain good wiring, the thickness of the metal layer provided on the substrate must be 20 μm or less. Of course, when the wiring is obtained by the semi-additive method, the thickness of the metal layer must be several μm.
As a method for obtaining such a base material, a metal thin film is obtained on the surface of the insulating resin film by a dry plating method, a copper thin film is obtained thereon by a dry plating method, and a copper layer is provided thereon by a wet plating method. The method of obtaining a layer is recommended. This is because the thickness of the metal layer can be arbitrarily controlled in this base material because all the constituent films are obtained by plating.

  In addition, as the wiring pitch becomes finer, the improvement in the adhesion between the metal layer and the insulating film is also required. For example, when a semiconductor element is mounted on a flexible wiring board, the electrode on the surface of the semiconductor element and the inner lead portion of the wiring are wire-bonded. In order to shorten the tact time at this time, pressure is applied at a high temperature. This is because wire bonding is performed by multiplying. For this reason, for example, it has become important to evaluate the adhesion strength (PCT adhesion strength) after performing Pressure Cooker Test (PCT) at 125 ° C., humidity 85%, and 96 hours.

By the way, improvement of the adhesion strength between the polyimide film and the metal layer provided on the surface thereof has been an ongoing study since the development of such a substrate, and many attempts have already been made.
Incidentally, the present applicant includes pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA) as main components, or pyromellitic dianhydride (PMDA) as main components. Using a polyimide film containing a component composed of 4,4′-diaminodiphenyl ether (ODA), a component composed of biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiphenyl ether (ODA), the surface of this polyimide film Is modified by plasma treatment, corona discharge or wet treatment to introduce a hydrophilic functional group on the surface, and the thickness of the modified layer is set to 200 mm or less, and at least nickel, chromium, and A seed layer is made of a metal selected from the group consisting of these alloys, and plated on it. By providing a copper layer of Riatsusa 8 [mu] m, it has proposed a method of manufacturing a two-layer plated copper polyimide substrate (see Patent Document 1 the first and second pages).
By this method, the initial adhesion strength between the polyimide surface of the obtained base material and the metal layer was PCT for 100 hours at 121 ° C., 95% humidity and 2 atm after being left in the atmosphere at 150 ° C. for 168 hours. The adhesion strength after the test was all excellent at 400 N / m or more (see Patent Document 1, page 5).

In addition, the applicant of the present invention is a two-layer plated copper polyimide substrate in which two seed layers are provided on the polyimide film surface, and a copper layer is provided thereon, and a 5 to 25 angstrom thick Cr layer provided by sputtering. The layer is a first layer, and a second layer is formed thereon. Then, a nickel-chromium alloy film having a Cr concentration of 15 to 40% with a thickness of 10 to 150 mm is formed by a sputtering method to form a seed layer. It is proposed to provide a copper layer having a thickness of 8 μm (see Patent Document 2, pages 1 and 2).
According to this method, the adhesion strength has been confirmed to be 640 to 690 N / m after being left at 150 ° C. for 10 days, and to be 530 to 590 N / m even after being left at 350 to 450 ° C. for 10 seconds (Patent Document). 2 See Table 1).
However, the wire bonding to the inner lead portion of the 25 μm pitch wiring described above is performed at a temperature of 400 ° C. or higher and under pressure, so high heat and pressure are concentrated on the tip of the inner lead. There is a problem that the inner lead tip and the polyimide film peel off. Therefore, recently, higher adhesion strength has been demanded.

JP 2007-318177 A (refer to pages 1, 2, and 5) JP 2004-158493 A (refer to Table 1, page 1, 2)

  An object of the present invention is to provide a metallized polyimide film, a flexible wiring board, and a flexible wiring board having an initial adhesion strength of 900 N / m or more and an adhesion strength of 600 N / m or more after the PCT test in view of the above-described problems of the prior art. It is to provide a manufacturing method.

  As a result of various studies to solve the above problems, the present inventors have used an polyimide film having a specific oxygen permeability and water absorption rate, so that the initial adhesion strength is 900 N / m or more, and the adhesion after the PCT test is achieved. It has been found that a metallized polyimide film having a strength of 600 N / m or more can be obtained, and if this is used, a flexible wiring board can be obtained in which the adhesive strength does not decrease even when wire bonding is performed to the inner lead portion of a 25 μm pitch wiring. The present invention has been completed.

That is, according to the first invention of the present invention, a metallized polyimide film in which a metal film is directly provided on the surface of a polyimide film by a plating method, and the polyimide film is measured under 1013 hPa when the film thickness is 35 μm. oxygen permeability, at 300~500cm ³ / ^m 2/24 hours, and, metallized polyimide films are provided, wherein the water absorption is 1-3%.

  According to a second invention of the present invention, in the first invention, the polyimide film is a polyimide film characterized by having a coefficient of thermal expansion of 10 ppm / ° C. to 18 ppm / ° C. A metallized polyimide film is provided.

  According to a third invention of the present invention, in the first or second invention, the polyimide film contains an imide bond by biphenyltetracarboxylic acid and a diamine compound in the polyimide molecule, and the TD direction on the surface thereof. Characterized by having only a peak having a half width of 1.5 ° or less at 2θ = 12 ° to 18 ° when thin film X-ray diffraction measurement is performed (Cu Kα incident angle = 0.1 °). A polyimide film is provided.

  According to a fourth invention of the present invention, in any one of the first to third inventions, the metal film is a metal thin film made of at least one selected from nickel, chromium, or an alloy thereof. There is provided a metallized polyimide film comprising a copper thin film provided on the metal thin film and a copper layer provided on the copper thin film.

  Furthermore, according to a fifth aspect of the present invention, there is provided a metallized polyimide film characterized in that in any one of the first to fourth aspects, the metal film has a thickness of 20 μm or less. .

According to a sixth invention of the present invention, according to any one of the first to fifth inventions, when the film thickness is 35 μm, the oxygen permeability measured under 1013 hPa is 300 to 500 cm ³ / m ² / Using a polyimide film having a film thickness of 25 to 50 μm having a water absorption of 1 to 3% for 24 hours, a metal thin film and a copper thin film are sequentially formed on the surface by a dry plating method. A method for producing a metallized polyimide film is provided in which a copper layer is formed by a wet plating method.

  On the other hand, according to the seventh invention of the present invention, there is provided a flexible wiring board in which a metal film wiring pattern is provided on the surface of a polyimide film having a thermal expansion coefficient of 10 ppm / ° C. to 18 ppm / ° C. Contains an imide bond by biphenyltetracarboxylic acid and a diamine compound in the polyimide molecule, and when the surface TD direction is measured by thin film X-ray diffraction (Cu Kα incident angle = 0.1 °), 2θ = A flexible wiring board having one peak having a half width of 1.5 ° or less in a range of 12 ° to 18 ° is provided.

According to an eighth aspect of the present invention, in the seventh aspect, the metal film comprises at least one metal thin film selected from nickel, chromium, or an alloy thereof, and an upper surface of the metal thin film. There is provided a flexible wiring board comprising three layers of a copper thin film provided on the copper thin film and a copper layer provided thereon.
According to a ninth aspect of the present invention, there is provided the flexible wiring board according to the seventh or eighth aspect, wherein the metal film has a thickness of 20 μm or less.
According to the tenth aspect of the present invention, in any one of the seventh to ninth aspects, when the metal film layer is removed by etching and the film surface after wiring processing is reproduced, the surface of the polyimide film is Flexible wiring characterized in that when a thin film X-ray diffraction measurement is performed in the TD direction (Cu Kα incident angle = 0.1 °), a peak with a half width of 1.5 ° or less exists at 2θ = 12 ° to 18 °. A board is provided.
Furthermore, according to the eleventh invention of the present invention, according to any one of the first to sixth inventions, the metal film on the surface of the metallized polyimide film is processed by a subtractive method or a semi-additive method. Provided is a method for manufacturing a flexible wiring board, wherein the wiring is formed.

In the metallized polyimide film of the present invention, a metal thin film is formed on the surface of a specific polyimide film by dry plating using either nickel, chromium or an alloy thereof, and a copper thin film is formed thereon by dry plating. Then, a copper layer was provided thereon by a wet plating method to form a metal film having a thickness of 20 μm or less, so that the initial adhesion strength was 900 N / m or more, and the adhesion strength after the PCT test was 600 N / m. It will have the above.
Therefore, the flexible wiring board of the present invention having a fine pitch wiring portion produced using the metallized polyimide film of the present invention is suitable for wire bonding work at a high temperature required in recent mounting work. We can cope enough. Therefore, the industrial value of the present invention is high.

It is a chart of the thin film X-ray diffraction of the polyimide film used by this invention (Example 1). It is the chart obtained by performing thin film X-ray diffraction with respect to the surface which is not covered with a metal layer among COF of this invention (Example 1), and the polyimide was exposed.

Hereinafter, the metallized polyimide film of the present invention, the flexible wiring board, and the production methods thereof will be described in detail.
The present invention provides a metallized polyimide film having an initial adhesion strength of 900 N / m or more and an adhesion strength of 600 N / m or more after the PCT test, and a method for producing a flexible wiring board obtained using the same. is there. In the present invention, in order to achieve this object, a metallized polyimide film, a specific polyimide film, a metal thin film directly provided on the surface thereof by a dry plating method, and a copper thin film provided thereon by a dry plating method And a metal layer composed of three copper layers formed thereon by a wet plating method.

1. Polyimide film used in the polyimide film present invention, the value of oxygen permeability obtained by measuring under 1013hPa when the film thickness 35μm is, is of 300~500cm ³ / ^m 2/24 hours, and water absorption 1 to 3%.
And preferably, the thermal expansion coefficient is 10 ppm / ° C. to 18 ppm / ° C., the polyimide molecule contains an imide bond by biphenyltetracarboxylic acid and a diamine compound, and the surface thereof is in the TD direction (the width direction of the polyimide film). ) Has a peak with a half width of 1.5 ° or less at 2θ = 12 ° to 18 ° when thin film X-ray diffraction measurement is performed (Cu Kα incident angle = 0.1 °). However, the polyimide film used in the present invention does not have a peak with a half width of 1.5 ° or less at 2θ = 2 ° to 10 °.

After the metal thin film and the copper thin film are provided by the dry plating method on the surface of the specific polyimide film, the metalized polyimide film of the present invention is obtained by providing the copper layer having a predetermined thickness by the wet plating method. .
When a copper layer is obtained by a wet plating method, particularly an electroplating method, a tensile stress is generated as an electrodeposition stress in the copper layer, and this tensile stress causes peeling between the metal layer and the polyimide layer.
When a copper layer is provided by a wet plating method, the polyimide film is immersed in a plating bath. The polyimide film has good water absorption, and when immersed in a plating bath, it absorbs water and expands. And since it is heat-dried after completion | finish of plating, it shrink | contracts and it returns to the state before a plating process. Therefore, if the polyimide film has an appropriate expansion rate due to water absorption, a copper plating layer can be completed on the surface of the polyimide film that has been appropriately expanded, and then the polyimide film can be contracted and stretched by heating and drying. It is possible to reduce the tensile stress remaining as internal stress in the copper layer.

The reason why the polyimide film in which the oxygen permeability is defined in the present invention is used is that the oxygen permeability is a substitute characteristic of the expansion rate due to water absorption. In the present invention, the values of oxygen permeability obtained by measuring under 1013hPa when the film thickness 35μm is, to use a polyimide film of 300~500cm ³ / ^m 2/24 hours, if this range, electroplating This is because the expansion rate due to the water absorption of the polyimide film at the time becomes a more appropriate value, and the tensile stress existing as internal stress in the copper layer obtained by heating and drying can be reduced. That is, when the oxygen permeability is less than 300 cm ³ / (m ² · 24 h · atm), the polyimide film has insufficient expansion rate due to water absorption, and copper plating cannot be completed on the polyimide film surface. The tensile stress existing as the internal stress of the copper plating layer due to the subsequent shrinkage of the polyimide film cannot be sufficiently reduced.
On the other hand, when the oxygen permeability exceeds 500 cm ³ / (m ² · 24 h · atm), moisture remaining in the polyimide film after heating and drying increases, and the obtained metallized polyimide film is used as an electronic component. Since a problem arises in the corrosion resistance of the copper layer, it is not preferable.

Moreover, in this invention, it is necessary to consider a water absorption rate with the expansion rate by the water absorption of a polyimide film. In the present invention, a polyimide film having a water absorption rate of 1 to 3%, preferably 1 to 2% is used. However, when the water absorption rate is less than 1%, the amount of expansion of the polyimide film due to water absorption decreases, and the object of the present invention is achieved. Not. If the water absorption exceeds 3%, the amount of expansion due to water absorption of the polyimide film becomes too large, and when heated and dried, compressive stress is generated as internal stress in the copper layer, and sufficient initial adhesion strength and PCT adhesion strength are obtained. There may not be.
When a metal layer is provided directly on the surface of the polyimide film, the larger the difference in the coefficient of thermal expansion between the metal layer and the polyimide film, the greater the load on the bonding surface between the narrow wiring portion and the polyimide film due to high-temperature heating during bonding wire. Takes and becomes easy to peel off. Therefore, in order to avoid this, it is preferable that the thermal expansion coefficient of the polyimide film to be used is 10 ppm / ° C. to 18 ppm / ° C.

The reason why the polyimide film has oxygen permeability and water absorption as described above can be considered as follows.
Generally, it is known that a polyimide film is easily crystallized due to its heat resistance and molding method. In the crystallized polyimide film, polyimide molecules are aligned, and moisture easily enters and exits between the molecules. That is, in a properly crystallized polyimide, oxygen permeability obtained by measuring under 1013hPa becomes 300~500cm ³ / ^m 2/24 hours using a polyimide film having a thickness of 35 [mu] m, the water absorption 1-3% It can be.
Whether or not the polyimide film is crystallized can be confirmed by thin film X-ray diffraction measurement of the polyimide film surface. When crystallizing, depending on the degree of crystallinity, a plurality of peaks are usually confirmed on the chart. In the present invention, a crystallized polyimide film in which only a peak having a half width of 1.5 ° or less is shown at 2θ = 12 ° to 18 ° is used, and this provides an appropriate oxygen permeability and water absorption rate in the present invention. It is the polyimide film which has.

  The polyimide film used in the present invention is not limited by its constituents as long as it has the above characteristics, but it is preferable to use a polyimide film mainly composed of biphenyltetracarboxylic acid. This is because a polyimide film containing biphenyltetracarboxylic acid as a main component is excellent in heat resistance and dimensional stability.

  The thickness of the polyimide film used in the present invention is not particularly limited, but it is 25 to 50 μm and preferably 25 to 45 μm in view of ensuring bendability and yield when forming a metal film.

Moreover, what added the filler for the purpose of improving the various characteristics of films, such as slidability and heat conductivity, can also be used. In this case, preferable fillers include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.
The particle size of the filler is not particularly limited because it varies depending on the film characteristics to be modified and the type of filler to be added, but generally the average particle size is 0.05 to 100 μm, preferably 0.1 to 0.1 μm. It is 75 μm, more preferably 0.1 to 50 μm, particularly preferably 0.1 to 25 μm. If the particle diameter is below this range, the modification effect is less likely to appear, and if it exceeds this range, the surface characteristics may be greatly impaired, or the mechanical characteristics may be greatly deteriorated.
Also, the amount of filler added is not particularly limited because it is determined by the film properties to be modified, the filler particle diameter, and the like. Generally, the addition amount of the filler is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight with respect to 100 parts by weight of polyimide. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired.
As an example of such a preferable polyimide film, for example, Apical 35 FPI (registered trademark) commercially available from Kaneka Corporation can be given.

2. Manufacturing method of polyimide film The polyimide film used in the present invention is not limited by the manufacturing method, but first, the polyamic acid as a precursor is first manufactured and then converted into polyimide, and then the film is used. The method of making can be illustrated.

(1) Manufacture of polyamic acid which is a precursor In order to obtain polyamic acid, a well-known method and the method which combined them can be used. As typical polymerization methods, the following methods (a) to (e) may be mentioned. That is,
(A) An aromatic diamine is dissolved in an organic polar solvent, and an equimolar amount of an aromatic tetracarboxylic dianhydride is added thereto and polymerized.
(B) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, the aromatic diamine compound is added and polymerized so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound finally become substantially equimolar.
(C) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, the aromatic tetracarboxylic dianhydride is added and polymerized so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound finally become substantially equimolar.
(D) After dissolving and / or dispersing the aromatic tetracarboxylic dianhydride in an organic polar solvent, an aromatic diamine compound is added and polymerized so as to be substantially equimolar.
(E) A substantially equimolar mixture of aromatic tetracarboxylic dianhydride and aromatic diamine is reacted in an organic polar solvent for polymerization.
In order to obtain a polyamic acid, any of these methods (a) to (e) may be used, or a partial combination may be used. The polyamic acid obtained by any method can also be used as a raw material for the polyimide film used in the present invention.

Examples of the acid dihydrate include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride Anhydride, 4,4′-oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride Bis (2,3-dicarboxy Phenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimerit Acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and the like. A mixture of proportions can be preferably used.
Among these acid dianhydrides, especially pyromellitic dianhydride and / or 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride And / or the use of 3,3′4,4′-biphenyltetracarboxylic dianhydride, and further acid dianhydride containing 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride The use of a mixture of products is more preferred.

  Examples of the aromatic diamine compound include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 3,3′-dimethylbenzidine, and 2,2′-dimethylbenzidine. 3,3′-dimethoxybenzidine, 2,2′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-oxy Dianiline, 3,3′-oxydianiline, 3,4′-oxydianiline, 1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane, 4,4′-diaminodiphenylsilane, 4,4 '-Diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N Methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, bis {4- (4-amino Phenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1, 3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4-diaminobenzophenone, and the like thereof.

The polyamic acid for polyimide film used in the present invention is obtained by selecting and polymerizing the kind and blending ratio of aromatic acid tetracarboxylic dianhydride and aromatic diamine within the above range.
A preferred solvent for synthesizing the polyamic acid is not limited as long as it is a solvent that dissolves the polyamic acid, but amide solvents, that is, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2- Pyrrolidone and the like are preferable, and N, N-dimethylformamide and N, N-dimethylacetamide are particularly preferable.

(2) Conversion from polyamic acid to polyimide and film formation The organic solution containing polyamic acid thus obtained was then cast on a support such as a glass plate, aluminum foil, metal endless belt, metal drum, etc. Resin film. At this time, it is partially cured and / or dried by heating on the support. At this time, hot air or far-infrared radiation heat may be applied. Alternatively, the support itself may be heated. Furthermore, a method of applying hot air or far infrared radiation heat and a method of heating the support itself can be combined.
The resin film cast by heating becomes a self-supporting semi-cured film, a so-called gel film, and is peeled off from the support. This gel film is in an intermediate stage of curing from polyamic acid to polyimide, that is, partially imidized to have a self-supporting property and a residual volatile component such as a solvent.
Next, the gel film is heated to dry to remove the remaining solvent, and the curing (imidization) is completed together with this, but in order to avoid shrinkage of the gel film during drying and curing, the gel film While being held by a tenter frame with a pin or a tenter clip, it is conveyed to a heating furnace and heated at 200 to 400 ° C. to obtain a polyimide film.

3. Metallized polyimide film and method for producing the same The metallized polyimide film of the present invention is a polyimide film that is metallized by directly providing a metal film on the surface of the polyimide film by a plating method. The polyimide film, the oxygen permeability was measured under 1013hPa when the film thickness 35μm is at 300~500cm ³ / ^m 2/24 hours, and water absorption is characterized by a 1-3%.
In order to obtain the metallized polyimide film of the present invention, a metal thin film made of at least one selected from nickel, chromium, and alloys thereof is provided on the surface of the specific polyimide film by a dry plating method, and the metal thin film is formed on the metal thin film. A copper thin film is provided. Then, a copper layer having a predetermined thickness is provided on the copper thin film by a wet plating method to form a metallized polyimide film.

a) Metal thin film The metal thin film ensures reliability such as adhesion and heat resistance between the polyimide film and the metal film. Accordingly, the material of the metal thin film is selected from nickel, chromium, and alloys thereof in order to increase the adhesion between the polyimide film and the copper layer. It is preferable to use a nickel-chromium alloy because of the ease of etching. Further, in order to provide a nickel-chromium alloy concentration gradient, the metal thin film may be composed of a plurality of nickel-chromium alloy layers having different chromium concentrations. If comprised with these metals, the corrosion resistance and migration resistance of the metallized polyimide film will be improved.
Further, in order to further increase the corrosion resistance of the metal thin film, vanadium, titanium, molybdenum, cobalt, or the like may be added to the metal.
In addition, in order to improve adhesion between the polyimide film and the metal thin film before dry plating, the polyimide film surface is subjected to surface treatment by corona discharge or ion irradiation, and then subjected to ultraviolet irradiation treatment in an oxygen gas atmosphere. It is preferable to These treatment conditions are not particularly limited, and may be conditions applied to a normal method for producing a metallized polyimide film.
The thickness of the metal thin film is preferably 3 to 50 nm. If the thickness is less than 3 nm, when the wiring is prepared by etching the metal layer of the metallized polyimide film, the etching solution may erode the metal thin film, soak into the polyimide film and the metal thin film, and the wiring may float. There is not preferable. On the other hand, when the thickness exceeds 50 nm, the metal thin film is not completely removed when the wiring is produced by etching, and there is a possibility that the residue remains between the wirings to cause an insulation failure between the wirings.
The metal thin film is preferably formed by dry plating. The dry plating method includes sputtering method, magnetron sputtering method, ion plating method, cluster ion beam method, vacuum deposition method, CVD method, etc. Any of these may be used, but industrially magnetron sputtering method is used. It is done. This is because production efficiency is high.

b) Copper thin film In the present invention, the copper thin film is preferably formed by a dry plating method. As the dry plating method to be employed, any of the above-described sputtering method, magnetron sputtering method, ion plating method, cluster ion beam method, vacuum deposition method, CVD method and the like can be used. It is also possible to provide the copper thin film by a vapor deposition method after forming the metal thin film by a magnetron sputtering method. That is, the metal thin film and the copper thin film may be formed by dry plating using the same method or by different dry plating.
The reason why the copper thin film is provided is that when the copper layer is directly provided on the metal thin film by electroplating, the current carrying resistance is high and the current density of electroplating becomes unstable. By providing the copper thin film, the current resistance can be lowered and the current density during electroplating can be stabilized. The copper thin film has a thickness of 10 nm to 1 μm, preferably 20 nm to 0.8 μm. If it is thinner than this, the current resistance during electroplating cannot be lowered sufficiently, and if it is too thick, it takes too much time to form a film, which deteriorates productivity and impairs economy.

c) Copper layer It is preferable that the thickness of the said copper layer shall be 1 micrometer-20 micrometers. It is preferable that If the thickness is less than 1 μm, sufficient conductivity may not be obtained when the wiring is formed, and if it exceeds 20 μm, the internal stress of the copper layer becomes too large.
The copper layer is preferably provided by a wet plating method. This is because in the dry plating method, it takes too much time to plate up to a predetermined thickness, which deteriorates productivity and impairs economy. As the wet plating method, there are an electroplating method and an electroless plating method, either of which may be used and may be used in combination. However, since the electroplating method is simple and the resulting copper layer is dense, it is preferable to the electroless plating method. The plating conditions are known conditions.
When a copper layer is provided by electroplating, it is more preferable to use a sulfuric acid bath because an electrodeposited copper layer having an appropriate tensile stress can be obtained, and the internal stress due to expansion and expansion / contraction of the polyimide film can be easily balanced.
When a copper layer is obtained by electroplating, the internal stress of the copper layer is preferably a tensile stress of 5 to 30 MPa before the polyimide film is dried. When it is less than 5 MPa, the polyimide film stretch effect becomes too large when the polyimide film is dried, and when the tensile stress exceeds 30 MPa, the stretch effect of the polyimide film when the polyimide film is dried becomes too small. It is.
The electrolytic copper plating using a sulfuric acid bath may be performed under normal conditions. As a plating bath, a commercially available copper sulfate plating bath used for general electrolytic copper plating can be used. Moreover, it is preferable that the cathode current density sets the average cathode current density of a plating tank to 1-3 A / dm < ² >. When the average cathode current density of the cathode current density is less than 1 A / dm ² , the hardness of the obtained copper layer becomes high and it becomes difficult to ensure the bendability, and a flexible wiring board using the obtained metallized polyimide film This is because the obtained flexible wiring board does not have good flexibility. On the other hand, if the average cathode current density exceeds 3 A / dm ² , the residual stress generated in the obtained copper layer varies.
As with the dry plating process, the electrolytic copper plating apparatus using a sulfuric acid bath unwinds the roll-shaped polyimide film from the unwinder installed on the inlet side of the electrolytic copper plating apparatus and sequentially passes it through the plating tank. And wind it with a winder. It is preferable to use this roll-to-roll type electroplating apparatus in order to increase the production efficiency of the metalized polyimide film and to reduce the manufacturing cost. In this case, the film transport speed is preferably 50 to 150 m / h. If the conveyance speed is less than 50 m / h, the productivity becomes too low, and if it exceeds 150 m / h, the energization current amount must be increased, and a large-scale power supply device must be used. There is a problem that it becomes expensive.
In the metallized polyimide film of the present invention thus obtained, the initial adhesion strength is 900 N / m or more by evaluation based on JPCA BM01-11.5.3 (Method B) (peeling strength), In addition, the adhesion strength after PCT at a temperature of 125 ° C., a humidity of 85%, and 96 hours is 600 N / m or more.

4). A flexible wiring board and its manufacturing method The flexible wiring board of this invention provides the wiring pattern of a metal film on the surface of the metallized polyimide film whose said thermal expansion coefficient is 10 ppm / degrees C-18 ppm / degrees C. That is, it is a flexible wiring board in which a metal film wiring pattern is provided on the surface of a polyimide film having a thermal expansion coefficient of 10 ppm / ° C. to 18 ppm / ° C., and the polyimide film is an imide composed of biphenyltetracarboxylic acid and a diamine compound. The bond is contained in the polyimide molecule, and when the TD direction of the surface is measured by thin film X-ray diffraction (Cu Kα incident angle = 0.1 °), the half value is in the range of 2θ = 12 ° to 18 °. It has one peak with a width of 1.5 ° or less.
The metal film includes: a metal thin film made of at least one selected from nickel, chromium, or an alloy thereof; a copper thin film provided on the metal thin film; and a copper layer provided thereon The metal film has a thickness of 20 μm or less.
Further, when the metal film layer was etched away with an iron chloride solution and the film surface after wiring processing was reproduced, the TD direction of the surface of the polyimide film was measured by thin film X-ray diffraction measurement (Cu Kα incident angle = 0.1 °). ), There is a peak with a half width of 1.5 ° or less at 2θ = 12 ° to 18 °, and a peak with a half width of 1.5 ° or less at 2θ = 28 ° to 34 °. Here, the peak at 2θ = 12 ° to 18 ° coincides with the peak of the long polyimide film that is a raw material of the metallized polyimide film.

In the method for manufacturing a flexible wiring board of the present invention, the wiring pattern can be obtained by processing by a subtractive method or a semi-additive method.
For example, in order to obtain a flexible wiring board by the subtractive method, a resist layer is provided on the metal film surface of the metallized polyimide film of the present invention, an exposure mask having a predetermined pattern is provided thereon, and ultraviolet rays are emitted from the resist mask. An etching mask for obtaining a wiring part is obtained by irradiation and exposure and development. Next, the exposed metal film is removed by etching, then the remaining etching mask is removed, washed with water, and a desired plating is applied to necessary portions to obtain the flexible wiring board of the present invention.
On the other hand, in order to obtain a flexible wiring board by the semi-additive method, a resist layer is provided on the metal film surface of the metallized polyimide film of the present invention, a mask having a predetermined wiring pattern is provided thereon, and exposure is performed by irradiating ultraviolet rays. Then, development is performed to obtain a plating mask in which the wiring becomes an opening, copper is deposited on the surface of the metal film exposed to the opening by an electrolytic copper plating method, and then the wiring mask is removed. Thereafter, the metal film other than the wiring is removed by soft etching to ensure the insulation of the wiring, washed with water, and desired plating is performed on the necessary portion to obtain the flexible wiring board of the present invention.
The wiring structure of the flexible wiring board of the present invention has a structure in which a metal film composed of a metal thin film, a copper thin film, and a copper layer is laminated in this order from the polyimide film surface, regardless of whether the wiring structure is produced by a subtractive method or a semi-additive method. It has become.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. The oxygen permeability measurement method, thin film X-ray diffraction measurement conditions, adhesion strength measurement method, and Pressure Cooker Test conditions used in the examples are as follows.

(1) Oxygen permeability: Measured in accordance with the JIS K7126 differential pressure method at a temperature of 23 ° C.
(2) Thin-film X-ray diffraction measurement conditions: As a diffractometer, a horizontal X-ray diffractometer SmartLab manufactured by Rigaku Co., Ltd. is used, the incident angle (ω) is 0.1 ° in the TD direction, the sampling width is 0.1 °, The measurement angle 2θ was 2 ° to 60 °, and the scanning speed was 4 ° / min.
(3) Adhesion strength: A wiring pattern having a line width of 1 mm and a length of 50 mm is formed by a subtractive method, and this is used to determine the JPCA BM01-11.5.3 (method B) (stripping strength). It calculated | required by the peeling method.
(4) Pressure Cooker Test conditions: temperature 125 ° C., humidity 85%, 96 hr.
(5) Water absorption: determined by the immersion method (Immersion) at 20 ° C. for 24 hours as defined in ASTM D570.
(6) Thermal expansion coefficient: Using a TMA (thermomechanical analysis) apparatus, the TD direction in the range of 50 ° to 200 ° was determined by a tensile method.

Example 1
First, the oxygen permeability is 450 cm ³ / (m ² · 24 hours 1013 hPa), the water absorption is 1.8%, the thermal expansion coefficient is TD direction: 11 ppm / ° C., and the thin film X-ray diffraction results shown in FIG. As can be seen, a long polyimide film mainly composed of biphenyltetracarboxylic acid with a thickness of 35 μm in which only a peak with a half width of 1.0 ° is observed at 2θ = 14 ° (manufactured by Kaneka Corporation, Apical 35FP) ) Was prepared.
A 20 mass% Cr chromium-nickel alloy layer having an average thickness of 230 mm (23 nm) is formed on one side of the polyimide film by a direct current sputtering method using a sputtering facility including an unwinder, a sputtering device, and a winder. It was formed as a metal thin film. Further, similarly, a copper thin film having an average thickness of 1000 mm (100 nm) was formed on the metal thin film.
Next, a copper layer having a thickness of 8 μm was provided on the copper thin film by electrolytic copper plating to obtain a metallized polyimide film. The electroplating bath used was a copper sulfate plating bath with a copper concentration of 23 g / l, and the bath temperature during plating was 27 ° C. In addition, the plating tank is a multi-structure tank in which a plurality of plating tanks are connected so that a polyimide film having a metal layer on one side is continuously immersed in each tank by an unwinder and a winder. Electroplating was carried out while being conveyed. The conveyance speed was 75 m / h, and the average cathode current density of the plating tank was adjusted to 1.0 to 2.5 A / dm ² to perform copper plating.
The initial adhesion strength of the resulting metalized polyimide film was determined to be 1028 N / m, and the adhesion strength after the PCT test was 691 N / m. Incidentally, the adhesion strength after being held at 150 ° C. for 168 hours was 446 N / m.
Next, using this metallized polyimide film, a COF (Chip on film), flexible wiring board having a wiring interval of 35 μm and a total wiring width of 15000 μm was prepared by a subtractive method. An IC chip was mounted thereon, and electrodes on the surface of the IC chip and lead portions of the wiring were wire bonded using a wire bonding apparatus at 400 ° C. under a bonding process condition of 0.5 seconds. Thereafter, an etching process was performed using a ferric chloride solution, a process using an etchant containing hydrochloric acid, and a process using an alkaline etchant containing permanganate to etch the inner lead portion. At this time, the proportion of the bonding failure between the lead and the polyimide film generated in the inner lead portion was 0.0001%.
Further, thin film X-ray diffraction was performed on the surface of the COF that was not covered with the metal film and exposed with the polyimide. As a result, as shown in FIG. 2, it was found that 2θ values had peaks at 14 ° and 29 °. Among these, the peak at 14 ° is a peak caused by a long polyimide film that is a raw material of the metallized polyimide film.

(Example 2)
A flexible wiring board was produced in the same manner as in Example 1 except that the metalized polyimide film obtained in Example 1 was used and the wiring interval was set to 25 μm, and the proportion of poor bonding was obtained in the same manner as in Example 1. The ratio of poor bonding between the inner lead and the polyimide film was 0.005%, and it was found that there was sufficient dimensional reliability even at a fine pitch.

(Comparative Example 1)
As a polyimide film, the thickness is mainly composed of biphenyltetracarboxylic acid having an oxygen permeability of 44 cm ³ / (m ² · 24 h · atm), a water absorption rate of 1.7%, and a thermal expansion coefficient of TD direction: 16 ppm / ° C. A metallized polyimide film was obtained in the same manner as in Example 1 except that a 38 μm polyimide film (manufactured by Toray DuPont, Kapton 150EN) was used. When Kapton 150EN was subjected to thin film X-ray diffraction, large peaks at 2θ of 10 ° and 14 ° were confirmed.
When the obtained metallized polyimide film was evaluated in the same manner as in Example 1, the initial adhesion strength was 725 N / m and the PCT adhesion strength was 412 N / m. Incidentally, the adhesion strength after being held at 150 ° C. for 168 hours was 423 N / m.
Next, a flexible wiring board having a wiring width of 35 μm was produced in the same manner as in Example 1 except that the metalized polyimide film was used, and the proportion of defective bonding was determined in the same manner as in Example 1. The ratio of the bonding failure generated in the inner lead portion of the wiring is 0.001%, which is a bad value as compared with the example, and even with a wiring width of 35 μm, a product having sufficient reliability was not obtained.
Further, when the thin film X-ray diffraction was performed on the surface of the polyimide that was not covered with the metal film of the COF by etching, large peaks at 2 ° and 10 ° and 14 ° were confirmed.

(Comparative Example 2)
A flexible wiring board was prepared in the same manner as in Comparative Example 1 except that the wiring interval was set to 25 μm, and the proportion of defective bonding was determined in the same manner as in Example 1. The ratio of the bonding failure that occurred in the inner lead of the wiring was 0.1%. Compared with Example 2, when the pitch was made fine, a product having sufficient reliability could not be obtained.

(Comparative Example 3)
As a polyimide film, the thickness is mainly composed of biphenyltetracarboxylic acid having an oxygen permeability of 8 cm ³ / (m ² · 24 h · atm), a water absorption rate of 1.4%, and a thermal expansion coefficient of TD direction: 14 ppm / ° C. A metallized polyimide film was obtained in the same manner as in Example 1 except that a 35 μm polyimide film (product name, Upilex 35SGA manufactured by Ube Industries) was used. In addition, when Upilex 35SGA was subjected to thin film X-ray diffraction, large peaks were confirmed at θ and 11 ° and 14 ° positions.
When the obtained metallized polyimide film was evaluated in the same manner as in Example 1, the initial adhesion strength was 756 N / m, and the PCT adhesion strength was 516 N / m. Incidentally, the adhesion strength after being held at 150 ° C. for 168 hours was 436 N / m.
Next, a flexible wiring board having a wiring width of 35 μm was produced in the same manner as in Example 1 except that the metalized polyimide film was used, and the proportion of defective bonding was determined in the same manner as in Example 1. The proportion of poor bonding that occurred in the inner leads of the wiring was 0.001%, which was a bad value as compared with Example 1.
In addition, when thin film X-ray diffraction was performed on the surface of the polyimide that was not covered with the metal layer of COF by etching, large peaks at 11 ° and 14 ° at 2θ were confirmed.

(Comparative Example 4)
A flexible wiring board was prepared in the same manner as in Comparative Example 3 except that the wiring interval was set to 25 μm, and the proportion of defective bonding was determined in the same manner as in Example 1. The ratio of the bonding failure that occurred in the electrode part of the wiring was 0.1%, and it was found that, when compared to Example 2, when the pitch was made fine, no reliable one could be obtained.

"Evaluation"
From the above examples, since the metallized polyimide film of the present invention has extremely high initial adhesion strength and PCT adhesion strength after the PCT test, when a fine pitch flexible wiring board is produced using this, It can be seen that even when wire bonding is performed by pressing at a temperature of 400 ° C. or higher when mounting the IC, the lead is not peeled off from the polyimide film, and a highly reliable flexible wiring board can be obtained. This is the same when a fine pitch flexible wiring board is produced.
On the other hand, according to the comparative example, since a metallized polyimide film that does not meet the conditions of the present invention was used, a highly reliable flexible wiring board could not be obtained even with a wiring width of 35 μm.

When a flexible wiring board is produced using the metallized polyimide film of the present invention, the initial adhesion strength and the PCT adhesion strength between the film and the metal film are extremely high. Therefore, at the temperature of 400 ° C. or higher when the IC is mounted on the wiring board. Even if wire bonding is performed under pressure, the lead is not peeled off from the polyimide film, and a highly reliable flexible wiring board can be obtained.
Therefore, the industrial value of the present invention is extremely high as a base material for producing a fine-pitch flexible wiring board, which is most demanded recently.

Claims (11)

It is a metallized polyimide film in which a metal film is directly provided on the surface of the polyimide film by a plating method,
The polyimide film, the oxygen permeability was measured under 1013hPa when the film thickness 35μm is at 300~500cm ³ / ^m 2/24 hours, and metallization, characterized in that water absorption is 1-3% Polyimide film.   The metallized polyimide film according to claim 1, wherein the polyimide film has a thermal expansion coefficient of 10 ppm / ° C to 18 ppm / ° C.   The polyimide film contains an imide bond by biphenyltetracarboxylic acid and a diamine compound in the polyimide molecule, and 2θ when the TD direction of the surface is measured by thin film X-ray diffraction (Cu Kα incident angle = 0.1 °). The metallized polyimide film according to claim 1, wherein the metallized polyimide film has only a peak having a half width of 1.5 ° or less at 12 ° to 18 °.   The metal film includes: a metal thin film made of at least one selected from nickel, chromium, or an alloy thereof; a copper thin film provided on the metal thin film; and a copper layer provided thereon The metallized polyimide film according to any one of claims 1 to 3, wherein the metallized polyimide film is composed of three layers.   The metallized polyimide film according to claim 1, wherein the metal film has a thickness of 20 μm or less. The oxygen permeability was measured under 1013hPa when the film thickness 35μm is a 300~500cm ³ / ^m 2/24 hours, and, using a polyimide film having a thickness of 25~50μm water absorption is 1-3% A metal thin film and a copper thin film are sequentially formed on the surface by a dry plating method, and a copper layer is formed on the copper thin film by a wet plating method. Of manufacturing a fluorinated polyimide film. A flexible wiring board having a metal film wiring pattern provided on the surface of a polyimide film having a thermal expansion coefficient of 10 ppm / ° C to 18 ppm / ° C,
The polyimide film contains an imide bond by biphenyltetracarboxylic acid and a diamine compound in the polyimide molecule, and when the surface TD direction is measured by thin film X-ray diffraction (Cu Kα incident angle = 0.1 °). A flexible wiring board having one peak having a half-value width of 1.5 ° or less in a range of 2θ = 12 ° to 18 °.   The metal film includes: a metal thin film made of at least one selected from nickel, chromium, or an alloy thereof; a copper thin film provided on the metal thin film; and a copper layer provided thereon The flexible wiring board according to claim 7, comprising three layers.   The flexible wiring board according to claim 7, wherein the metal film has a thickness of 20 μm or less.   When the metal film layer is etched away and the film surface after wiring processing is reproduced, the TD direction of the surface of the polyimide film is measured by thin film X-ray diffraction measurement (Cu Kα incident angle = 0.1 °), 2θ = 12 The flexible wiring board according to any one of claims 7 to 9, wherein a peak having a half-value width of 1.5 ° or less is present in a range of from 18 ° to 18 °.   Manufacturing the flexible wiring board characterized by using the metallized polyimide film according to any one of claims 1 to 6 to form a wiring by processing a metal film on the surface thereof by a subtractive method or a semi-additive method. Method.

Images