KR101009128B1 - Flexible copper-clad laminate and method for making the same - Google Patents

Abstract

This invention relates to the flexible copper clad laminated board which is easy to handle at the time of copper clad laminated board manufacture, has high flexibility after shaping | molding, good bendability, and is excellent in a stress relaxation effect, without reducing the thickness of copper foil.

The present invention is a copper clad laminate in which a copper foil layer is formed on one or both surfaces of a polyimide resin layer through a heat treatment step, wherein the elastic modulus before heat treatment of the copper foil layer is 50 to 80 GPa, the elastic modulus (p2) before heat treatment and 300 ° C. or higher. Provided is a flexible copper clad laminate having a ratio (p2 / p3) of the elastic modulus p3 to after heat treatment of 3.5 to 5.5.

Flexible Copper Clad Laminates, Copper Foil Layer, Elastic Modulus

Description

Flexible Copper Clad Laminate and its Manufacturing Method {Flexible copper-clad laminate and method for making the same}

TECHNICAL FIELD This invention relates to a flexible copper clad laminated board. Specifically, It is related with the flexible copper clad laminated board which was excellent in bending resistance.

(Patent Document 1) Japanese Patent Application Laid-Open No. 2001-58203

(Patent Document 2) Japanese Patent No. 3009383

Flexible copper clad laminates are widely used in electronic devices that require flexibility, flexibility, and high density mounting. In recent years, as the memory capacity of devices increases, narrower pitches and higher density packaging of wires have progressed, leading to higher demands for mechanical properties for laminates. It is thought that electrolytic copper foil is generally good in the characteristic derived from the manufacturing method of copper foil for the narrow pitch correspondence of a flexible copper clad laminated board. On the other hand, in recent high-density packaging, the bent portion at the time of bending a laminated plate and storing it in a case increases, and the bending angle is decreasing. Therefore, when it is rigid like conventional electrolytic copper foil, and has high tensile strength and low ductility, the flexible copper clad laminated board manufactured by the copper foil will be easily disconnected by the flexible fatigue of copper foil, In many cases, electrical reliability could not be achieved.

According to Patent Document 1, the intensity (I) of the (200) plane obtained by X-ray diffraction of the rolled surface after annealing and recrystallization is obtained from the (200) obtained by X-ray diffraction of fine powder copper. Regarding the strength 10 of the surface, it is described that copper foil has high flexibility by being I / 10> 20, and it is suggested that high flexibility is expressed by control of the crystal structure. In addition, according to Patent Document 2, in order to obtain the crystal structure of Patent Document 1, annealing immediately before the final cold rolling is performed under the condition that the average particle diameter of the recrystallized particles obtained by this annealing is 5 to 20 µm, followed by the final cold It is described to make the rolling workability in rolling into 90% or more.

In addition, since the tensile strength and the rigidity of the conventional electrolytic copper foil do not change much after annealing by heat treatment, and the annealing effect is small, when the attention is paid to the bending resistance of the molded article, a flexible copper foil which suppresses the tensile strength of the copper foil in the step before heat treatment can be used. In this case, in the case of manufacturing a flexible copper clad laminated board, tension was difficult to adjust and it became a factor which reduces productivity.

From this background, so far, in order to make ductility, bending resistance, and fine pattern property compatible, physical properties have been supplemented by making copper sheet thickness thin and increasing the flexibility of the whole laminated board. However, in this technology, since the design of the copper clad laminate is restricted, the development of a flexible copper clad laminate that satisfies the ductility, bending resistance, and fine patternability has been desired even without the thickness adjustment of the copper foil.

An object of this invention is to provide the flexible copper clad laminated board which is easy to handle at the time of copper clad laminated board manufacture, the flexibility after shaping | molding is high, the bending property is excellent, and is excellent in a stress relaxation effect, without reducing the thickness of copper foil.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining, the present inventors discovered that the said subject can be solved by using a specific copper foil for a flexible copper clad laminated board, and completed this invention.

That is, this invention is the copper clad laminated board by which the copper foil layer is formed on one or both surfaces of a polyimide-type resin layer through a heat processing process, The elasticity modulus before heat processing of a copper foil layer is 50-80 GPa, and the elasticity modulus (p2) before heat processing and The ratio (p2 / p3) of the elasticity modulus p3 after heat processing at 300 degreeC or more is 3.5-5.5, It is a flexible copper clad laminated board characterized by the above-mentioned.

In the flexible copper clad laminated board of this invention, it is preferable that the thickness of a copper foil layer is 12-18 micrometers, and the thickness of a resin layer is 15-25 micrometers.

The flexible copper clad laminated board of this invention is comprised from a copper foil layer and a polyimide-type resin layer. The copper foil layer can be formed on one side or both sides of the polyimide resin layer.

Hereinafter, the flexible copper clad laminated board of this invention is further demonstrated.

Rolled copper foil, electrolytic copper foil, etc. which were manufactured according to a well-known method can be used for the copper foil which comprises a copper clad laminated board. As for the copper foil used in this invention, it is necessary that the elasticity modulus (p2) before the heat processing of a copper foil layer is 50-80 GPa. If the modulus of elasticity is lower than 50 GPa, deformation is likely to occur during the manufacture of the flexible copper clad laminate, and if it is too low, it may break. When the elastic modulus exceeds 80 GPa, the rigidity increases, the relaxation of the tensile stress during the manufacture of the flexible copper clad laminate decreases, and plastic deformation easily occurs. Moreover, for this copper foil, it is necessary that ratio (p2 / p3) of the elasticity modulus p2 before heat processing and the elasticity modulus p3 after heat processing at 300 degreeC or more is 3.5-5.5. If the elastic modulus ratio is lower than 3.5, only a flexible copper clad laminate having insufficient flexibility can be obtained.

The flexible copper clad laminated board of this invention uses the copper foil which shows said elasticity modulus and elasticity modulus ratio, and is manufactured by the manufacturing process which has a heat processing process of a flexible copper clad laminated board. The heat processing temperature of a heat processing process is 300 degreeC or more, Preferably it is 300-450 degreeC. If the heat treatment temperature is lower than 300 ° C, it is estimated, but recrystallization of the copper foil is not sufficient, and a change in elastic modulus may not be seen, which is not preferable. On the other hand, when it exceeds 450 degreeC, copper foil deteriorates by oxidation etc., and the decomposition of the polyimide-type resin used for the flexible copper clad laminated board may occur, and it is unpreferable. Although the heat processing time at the temperature of 300 degreeC or more is arbitrary, Preferably it is 3 to 40 minutes. It is advantageous that the heat treatment step also serves as a heat treatment step performed for drying and imidization of the polyimide or its precursor applied to the copper foil.

The thickness of the copper foil used is 8-35 micrometers, Preferably it is 12-18 micrometers. Tension adjustment becomes difficult at the time of manufacture of a flexible copper clad laminated board, when copper foil thickness does not satisfy 8 micrometers, and when it exceeds 35 micrometers, since the flexibility of a flexible copper clad laminated board falls, it is unpreferable. In addition, the roughness degree of copper foil is Rz (10 point average roughness) = 0.5-1.5 micrometers, Ra (arithmetic mean roughness) = 0.05-0.25 micrometers, roughness, even in the case of copper foil with a smooth surface and a rough surface. In view of the foregoing, Rz = 0.5 to 1.5 µm and Ra = 0.05 to 0.30 µm. By using the thing of this range for the roughness degree of copper foil, it becomes the copper clad laminated board which can shape a fine circuit pattern. In particular, since the roughness of a rough surface affects fine pattern property at the time of circuit processing, it is preferable to use the copper foil whose Ra is 0.05-0.27 micrometers.

As a specific example of the copper foil which satisfy | fills the conditions of said elasticity modulus, an elasticity modulus ratio, and thickness, BHY-HA foil made by Nikko Kinjoku Co., Ltd. is mentioned.

Next, the polyimide resin layer of the copper clad laminate is described.

This polyimide resin layer can be formed by heat-processing the polyimide precursor resin (polyamic acid) obtained by making a well-known diamine and acid anhydride react in presence of a solvent.

As a diamine used for the synthesis | combination of a polyamic acid, it is 4,4'- diamino diphenyl ether, 2'-methoxy-4,4'- diamino benzanilide, 1, 4-bis (4-amino, for example. Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'- Diamino biphenyl, 3,3'- dihydroxy-4,4'- diamino biphenyl, 4,4'- diamino benzanilide, etc. are mentioned. As the acid anhydride, for example, pyromellitic anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfontetracarboxyl Acid dianhydride, 4,4'- oxydiphthalic anhydride, etc. are mentioned. Diamine and acid anhydride may use only 1 type, respectively and may use 2 or more types together.

As a solvent, dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene, etc. are mentioned, for example, 1 type may be used together and 2 or more types may be used together.

It is preferable to apply | coat a polyimide precursor solution directly on copper foil, and to form a polyimide-type resin layer, and to make the resin viscosity of a precursor into 500-35000cps. The coated precursor resin is dried and imidized by performing a heat treatment. The heat treatment is preferably performed at a temperature of 100 to 400 ° C. and a processing time of 20 to 40 minutes.

It is advantageous that this heat treatment also serves as heat treatment of copper foil. In this case, it is good that the time performed at the temperature of 300 degreeC or more is 3 minutes or more. Here, the elasticity modulus (p2) of the copper foil before heat processing is measured about the copper foil in the state which does not give a thermal history to copper foil after copper foil manufacture, and the elasticity modulus (p3) after heat processing in 300 degreeC or more is It is good to measure about the copper foil after heat processing for 3 to 40 minutes at 300-450 degreeC. About the elasticity modulus measurement of the copper foil after actual heat processing, it measures about the copper foil of the part in which resin is not coated at the time of manufacture.

The polyimide resin layer may consist of only a single layer or may be formed of a plurality of layers. When forming a multiple layer polyimide resin layer, it can apply | coat and form another polyimide resin one by one on the polyimide-type resin layer which consists of different structural components. When a polyimide resin layer consists of three or more layers, you may use the polyimide resin of the same structure 2 or more times.

The flexible copper clad laminate of the present invention can be produced by applying a solution of a polyimide precursor onto a copper foil, drying, and heat treatment as described above, but may be prepared by laminating one or more layers of polyimide film onto the copper foil. It may be. The flexible copper clad laminate thus produced may be a one-side copper clad laminate having the copper foil layer on only one side, or may be a double-side copper clad laminate having the copper foil layer on both sides. After forming a one-side copper clad laminated board, the double-sided copper clad laminated board is a method of crimping | bonding a copper foil layer with a hot press, the method of pressing a polyimide film between two copper foil layers, and crimping | bonding by hot press.

<Embodiment of the Invention>

Hereinafter, an Example demonstrates this invention further in detail.

In addition, in the following Examples, unless there is particular notice, various evaluation is based on the following.

[Measurement of Modulus of Elasticity]

It measured in 23 degreeC, 50% RH environment using the universal testing machine (STROGRAPH-R1) by Toyo Seiki Seisakusho.

[Evaluation of Insufficiency]

A test piece width: 8 mm and a test piece length: 150 mm were formed on a flexible copper clad laminate with a 200 μm wide line-and-space circuit, and CISV-1215 manufactured by Nikkan Kogyo Co., Ltd. was used as a cover material. The cover material was laminated | stacked on it, and the acceleration test was done using the Shin-Etsu Engineering Co., Ltd. IPC bending test machine on condition of curvature r: 1.25 mm, vibration stroke: 20 mm, and vibration speed: 1500 times / min. In this test, the number of times until the electrical resistance of the sample rose by 5% was determined.

The polyimide precursor resin solution used for the Example was synthesize | combined according to the following formulation.

Synthesis Example 1

N, N-dimethylacetamide (DMA) was added as a solvent to a thermocouple, a stirrer, and a reaction vessel capable of introducing nitrogen. 4,4'-diamino-2,2'-dimethylbiphenyl (DADMB) and 1,3-bis (4-aminophenoxy) benzene (DAB) were dissolved in the reaction vessel with stirring. Subsequently, 3,3 ', 4,4'-biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were added. The total amount of monomers charged was 15 wt%, the molar ratio (DADMB: BAB) of each diamine was 90:10, and the molar ratio (BPDA: PMDA) of each acid anhydride was 20:79. Thereafter, stirring was continued for 3 hours, and the viscosity of the obtained polyimide precursor resin solution was 20000 cps.

Synthesis Example 2

2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in a reaction vessel containing DMA while stirring. Subsequently, BPDA and PMDA were added. The total amount of the monomers was charged in an amount of 15 wt% and the molar ratio (BPDA: PMDA) of each acid anhydride was 4:69. Thereafter, stirring was continued for 3 hours, and the viscosity of the obtained polyimide precursor resin solution was 5000 cps.

<Example 1>

The polyimide obtained by the synthesis example 1 after preparing BHY-HA foil (18 micrometers in thickness) manufactured by Nikko Kinzoku Co., Ltd. as a copper foil, apply | coating and drying the polyimide precursor resin solution obtained by the synthesis example 2 on this foil. The precursor resin solution was apply | coated and dried, and the polyimide precursor resin solution obtained by the synthesis example 2 was apply | coated and dried on it, and the laminated body in which the polyimide precursor resin layer was formed on the copper foil layer was obtained.

This laminated body was put into oven, and it heat-processed at 360 degreeC for 3 minutes, and the single-sided copper clad laminated board whose polyimide resin thickness is 25 micrometers was obtained. The elastic modulus of the copper foil before heat treatment was 62 GPa, the elastic modulus of the copper foil layer after heat treatment was 17 GPa, and the elastic modulus ratio was 3.6.

The result of the test for breaking of the obtained flexible copper clad laminate was 55,000 times of breaking.

Comparative Example 1

Except having used BHY-22BT foil (18 micrometers in thickness) by Nikko Kinzo Co., Ltd. as copper foil, it carried out similarly to Example 1, and manufactured the flexible copper clad laminated board.

The elastic modulus of the copper foil before heat treatment was 53 GPa, the elastic modulus of the copper foil after heat treatment was 23 GPa, and the elastic modulus ratio was 2.3.

The result of the test for breaking of the obtained flexible copper clad laminate was 12500 times of breaks.

<Example 2>

The polyimide obtained by the synthesis example 1 after preparing BHY-HA foil (18 micrometers in thickness) manufactured by Nikko Kinzoku Co., Ltd. as a copper foil, apply | coating and drying the polyimide precursor resin solution obtained by the synthesis example 2 on this foil. The precursor resin solution was apply | coated and dried, and the polyimide precursor resin solution obtained by the synthesis example 2 was apply | coated and dried on it, and the laminated body in which the polyimide precursor resin layer was formed on the copper foil layer was obtained. This laminated body was heat-processed at 360 degreeC for 6 minutes, and the single-sided copper clad laminated board whose polyimide resin thickness is 25 micrometers was obtained.

The elasticity modulus of the copper foil before heat processing was 62 GPa, the elasticity modulus of the copper foil after heat processing was 16 GPa, and the elasticity modulus ratio was 3.9.

The result of the test for breaking of the obtained flexible copper clad laminate was 54000 times of breaking.

Comparative Example 2

Except having used HY-22BT foil (18 micrometers in thickness) by Nikko Kinzo Co., Ltd. as copper foil, it carried out similarly to Example 2, and manufactured the flexible copper clad laminated board.

The elasticity modulus of the copper foil before heat processing was 53 GPa, the elasticity modulus of the copper foil after heat processing was 21 GPa, and the elasticity modulus ratio was 2.5.

The result of the test for breaking of the obtained flexible copper clad laminate was 12000 times of breakdown.

<Example 3>

The polyimide obtained by the synthesis example 1 after preparing BHY-HA foil (18 micrometers in thickness) by Nikko Kinzoku Co., Ltd. as a copper foil, apply | coating and drying the polyimide precursor resin solution obtained by the synthesis example 2 on this foil. The precursor resin solution was apply | coated and dried, and the polyimide precursor resin solution obtained by the synthesis example 2 was apply | coated and dried on it, and the laminated body in which the polyimide precursor resin layer was formed on the copper foil layer was obtained. This laminated body was heat-processed at 360 degreeC for 13 minutes, and the single-sided copper clad laminated board whose polyimide resin thickness is 25 micrometers was obtained.

The elastic modulus of the copper foil before heat treatment was 62 GPa, the elastic modulus of the copper foil after heat treatment was 15 GPa, and the elastic modulus ratio was 4.1.

The test result of the breakdown of the obtained flexible copper clad laminate was 52000 times of breakdown.

Comparative Example 3

Except having used BHY-22BT foil (18 micrometers in thickness) by Nikko Kinzo Co., Ltd. as copper foil, it carried out similarly to Example 3, and manufactured the flexible copper clad laminated board.

The elasticity modulus of the copper foil before heat processing was 53 GPa, the elasticity modulus of the copper foil after heat processing was 21 GPa, and the elasticity modulus ratio was 2.5.

The result of the test for breaking of the obtained flexible copper clad laminate was 12000 times of breakdown.

ADVANTAGE OF THE INVENTION According to this invention, the flex resistance and the bending resistance of a flexible copper clad laminated board can be improved, and the flexible circuit material with high reliability at the time of use to the electrical and electronic components used by bending can be provided.

Claims (2)

A copper clad laminate formed by forming a copper foil layer on one or both surfaces of a polyimide resin layer through a heat treatment step, wherein the copper foil layer has an elastic modulus of 50 to 80 GPa before heat treatment, and has an elastic modulus (p2) before heat treatment and heat treatment at 300 ° C or higher. The ratio of the elastic modulus p3 (p2 / p3) is 3.5-5.5, The flexible copper clad laminated board characterized by the above-mentioned. The flexible copper clad laminate according to claim 1, wherein the copper foil layer has a thickness of 12 to 18 µm and the resin layer has a thickness of 15 to 25 µm.