JP4804806B2 - Copper-clad laminate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a copper clad laminate and a method for producing the same, and more particularly to a copper clad laminate for a flexible printed circuit board that can be finely processed for COF use and has excellent bending resistance, and a method for producing the same.

  Printed circuit boards are often used for electronic circuits of electronic devices. Among them, flexible printed circuit boards (FPCs) are particularly flexible, and the board itself is thin, so a TAB for mounting a driver IC on a tape carrier. It has been applied to the system (tape automated bonding). Recently, a COF method (chip-on-film), in which a bare IC chip is directly mounted on a film carrier tape, has been developed as a mounting method for mounting at a higher density in a smaller space, thereby reducing the pitch of wiring. Therefore, a flexible printed circuit board that can be finely processed is required.

  Conventionally, there are mainly a metallizing method, a laminating method, and a casting method as a manufacturing method for providing a copper-clad laminate capable of fine processing. The metalizing method is a method in which a metal is thinly deposited on the surface of a polyimide film by sputtering, and copper is formed on the surface by a non-electrolytic and / or electrolytic plating method. There are fatal defects in the formation of microcircuits, such as the presence of minute holes in the metal layer, which is inferior in the electromigration resistance of the circuit.

  The lamination method is a method of directly laminating a copper foil on a polyimide film. However, in Patent Document 1, in order to obtain a copper-clad laminate having high bending resistance, a rolled copper foil having a large crystal grain size is used. Is disclosed. However, such a rolled copper foil is soft, and a thin copper foil having a thickness of 35 μm or less is easily deformed by handling at the time of manufacturing a laminated plate. On the other hand, Patent Document 2 discloses that an electrolytic copper foil having a small crystal orientation, that is, a crystal grain size is used for a printed wiring board for a printed board having good etching properties. However, when the crystal grain size is small, it is difficult to obtain high bending resistance.

  The casting method is a method of forming a polyimide film layer by applying a polyimide precursor resin solution on a copper foil, followed by drying and curing. In addition to this method, in order to produce a laminate of good quality, the copper foil needs to have a certain thickness, and if it is required to be a thin copper foil layer, the intermediate laminate ( A laminated body before chemical polishing is prepared) and etched to obtain a target laminated plate. For example, Patent Document 3 discloses an electrolytic copper foil in which chemical polishing progresses uniformly and the surface of the copper foil after chemical polishing becomes smooth in the thinning of the copper foil portion by chemical polishing in the production of laminates. .

JP 2000-256765 A JP-A-7-268678 Japanese Patent Laid-Open No. 9-272994

  An object of the present invention is to provide a laminate that improves the handling properties in the production of laminates, and can be finely processed with a pitch of 30 μm or less, and has excellent bending resistance.

The copper clad laminate to be produced in the present invention is a copper clad laminate in which an insulating layer made of polyimide resin is formed on one surface of the copper foil. The crystal grain size of the copper foil is less than 2 μm before heat treatment. An electrolytic copper foil having a thickness of 2 to 7 μm after heat treatment at 340 ° C. for 9 hours, a crystal grain size of 2 μm or more, and a thickness of the copper foil of 3 to 18 μm, The copper-clad laminate is characterized in that the surface roughness Rz of the surface not in contact with the layer is 2.5 μm or less.
This copper clad laminate is excellent as a laminate for COF used for mounting semiconductor elements.

The present invention relates to a method for producing a copper clad laminate in which an insulating layer made of an insulating resin is formed on one surface of a copper foil. The copper foil has a thickness of 5 μm or more and a crystal grain size before heat treatment. After using an electrolytic copper foil of less than 2 μm and directly applying the polyimide precursor resin solution to one surface of the copper foil, heat treatment at 280 to 400 ° C. to form a polyimide resin insulating layer, After obtaining a laminate having a crystal grain size of 2 μm or more, the surface of the laminate that is not in contact with the insulating layer has a concentration of 0.5 to 10% hydrogen peroxide and 0.5 to 15% sulfuric acid ( and 10% to 90% of the copper foil thickness is removed, and the surface roughness Rz is 2.5 μm or less. It is.

  Hereinafter, the present invention will be described in detail.

  The copper clad laminate of the present invention has a structure in which an insulating layer made of polyimide resin is formed on one surface of a copper foil. Here, the copper foil which comprises a copper clad laminated board is 340 degreeC, and the copper clad laminated board of 9 hours of heat processing WHEREIN: The crystal grain diameter of this copper foil is less than 2 micrometers before heat processing, 340 degreeC, 9 hours It is an electrolytic copper foil which becomes 2-7 micrometers after the heat processing of this. Here, the state before the heat treatment usually corresponds to the state before the insulating layer is formed. For example, when an insulating layer is formed on a commercially available copper foil to form a copper clad laminate, the commercially available copper foil may have the above crystal grain size. And when forming an insulating layer in this copper foil and making it a laminated body, what is necessary is just to perform the heat processing for about 340 degreeC and about 9 hours before or after that. When the insulating layer is formed, a heat treatment is performed. If this heat treatment is not sufficient to obtain a desired crystal grain size, a necessary heat treatment can be added before or after that. . Furthermore, the copper foil constituting the copper foil layer of the copper clad laminate of the present invention has a crystal grain size of 2 μm or more, a thickness of 3 to 18 μm, and a surface roughness Rz of the surface not in contact with the insulating layer. It is necessary to be 2.5 μm or less. Since such a copper clad laminate can be obtained by the production method of the present invention, the copper clad laminate of the present invention will be described while explaining the production method.

  For the copper foil forming the laminate of the present invention, an electrolytic copper foil is used, and the crystal grain size of the copper foil is less than 2 μm, preferably 1 μm or less, more preferably 0.5 μm or less before the heat treatment. is there. When the crystal grain size of the copper foil is 2 μm or more, the copper foil itself becomes soft and easily deformed by handling at the time of manufacturing the laminate. Moreover, the thickness of the copper foil to be used is 5-35 micrometers, Preferably it is 9-18 micrometers, More preferably, it is good that it is 12-18 micrometers. When the thickness of the copper foil is larger than 35 μm, it takes time to reduce the thickness by chemical polishing. Further, when the thickness of the copper foil is less than 5 μm, the copper foil is easily deformed by handling at the time of manufacturing the laminate. A copper foil having such characteristics can be selected from commercially available products.

  The surface roughness Rz on the side where the insulating layer of the copper foil is provided is 3 μm or less, preferably 2 μm or less, and more preferably 1.2 μm or less. When the surface roughness Rz is larger than 3 μm, an etching residue is generated when an insulating layer is formed thereon, the conductor is removed, and fine processing is performed, and the linearity of the circuit is impaired. The surface roughness Rz of the copper foil not in direct contact with the insulating layer is 3.5 μm or less, preferably 2.7 μm or less, and more preferably 1.5 μm or less. When the surface roughness Rz is larger than 3.5 μm, it is difficult to control the surface roughness by chemical polishing described later.

  About the insulating layer which forms a laminated board, after apply | coating a polyimide precursor resin solution, it forms by drying and hardening. The polyimide precursor resin solution can be produced by polymerizing a known diamine and acid anhydride in the presence of a solvent.

  Examples of the diamine used include 4′4-diaminodiphenyl ether, 2′-methoxy 4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, and 1,3-bis (4-amino). Phenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'- Diaminobiphenyl, 4,4′-diaminobenzanilide and the like can be mentioned. Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride and the like. Each of the diamine and acid anhydride may be used alone or in combination of two or more.

  Examples of the solvent include dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and they can be used alone or in combination of two or more.

  About the said polyimide precursor resin solution, it is preferable to apply | coat and form directly on a copper foil layer in a precursor state, and it is preferable to make the polymerized resin viscosity into the range of 500 cps-35,000 cps. The polyimide resin layer may be formed of only a single layer or may be formed of a plurality of layers. When a plurality of polyimide resin layers are used, other polyimide precursor resin solutions can be sequentially applied on a polyimide precursor resin layer composed of different components and dried, and multiple layers can be applied simultaneously. You can also. When the polyimide resin layer is composed of three or more layers, two or more polyimide precursor resins having the same configuration may be used.

  After the polyimide precursor resin liquid is applied on the copper foil layer, heat treatment is performed. This heat treatment is preferably performed at 100 to 150 ° C. for 2 to 4 minutes in the air, and then vacuum heating is performed for about 9 hours. The heating temperature here is 150-400 degreeC, Preferably it is 200-370 degreeC, More preferably, it is 280-360 degreeC. By heating to the said temperature, a polyimide precursor resin turns into a polyimide resin and the laminated body of an intermediate body is obtained.

  The laminated body of the intermediate body obtained by said heat processing consists of a copper foil layer and an insulating layer. By adjusting the heat treatment conditions, the crystal grain size of the copper foil forming the copper foil layer is 2 to 7 μm, preferably 2 to 5 μm. If the crystal grain size of the copper foil is less than 2 μm, it is difficult to obtain high bending resistance.

  About the laminated body manufactured above, the etching solution containing 0.5 to 10% (wt%) of hydrogen peroxide and 0.5 to 15% (wt%) of sulfuric acid is applied to the copper foil that is not in direct contact with the insulating layer. 10 to 90% of the copper foil thickness is removed by chemical polishing in order to obtain the copper-clad laminate of the present invention. And the thickness of copper foil is 3-18 micrometers, Preferably it is 5-12 micrometers. When the thickness of the copper foil is larger than 18 μm, not only the bending resistance is lowered, but also fine processing in the circuit becomes difficult. When the thickness of the copper foil is less than 3 μm, the electromigration resistance of the circuit is inferior. The surface roughness Rz of the copper foil after chemical polishing is 2.5 μm or less, preferably 1.5 μm or less, and more preferably 1.0 μm or less. When the surface roughness of the copper foil is larger than 2.5 μm, it becomes difficult to perform fine processing in the circuit.

  Based on electrolytic copper foil with large crystal grain size, which has excellent flexibility, high adhesion between conductor and insulator, excellent electromigration resistance, fine processing of 30μm pitch or less is possible, and bending resistance A copper-clad laminate with excellent resistance can be obtained. Thereby, it can utilize effectively as a COF use for flexible printed circuit boards.

  Hereinafter, the present invention will be described in more detail with reference to examples.

In preparing the laminated plate, the following four types of copper foils were prepared.
1) Copper foil 1: electrolytic copper foil, insulating layer side Rz 0.6 μm, resist surface side Rz 0.7 μm, crystal grain size 0.4 μm before heat treatment, HLS foil 12 μm manufactured by Nippon Electrolytic Co., Ltd.
2) Copper foil 2: Electrolytic copper foil, insulating layer side Rz 1.3 μm, resist surface side Rz 0.9 μm, crystal grain size 0.5 μm before heat treatment, Nippon Electrolytic Co., Ltd. HLB foil 12 μm
3) Copper foil 3: Electrolytic copper foil, insulating layer side Rz 0.6 μm, resist surface side Rz 0.7 μm, crystal grain size 0.4 μm before heat treatment, USLP-S foil 12 μm manufactured by Nihon Denki Co., Ltd.
4) Copper foil 4: electrolytic copper foil, insulating layer side Rz 0.8 μm, resist surface side Rz 1.7 μm, crystal grain size 0.4 μm before heat treatment, NA-VLP foil 15 μm manufactured by Mitsui Kinzoku Co., Ltd.

The following etching solution was prepared as a chemical abrasive for the laminate.
Etching solution: Hydrogen peroxide / sulfuric acid chemical polishing solution (sulfuric acid concentration 20 g / L, hydrogen peroxide concentration 80 g / L)

Synthesis example 1
N-methylpyrrolidinone is placed in a thermocouple, a stirrer, and a reaction vessel into which nitrogen can be introduced. After soaking the reaction vessel in ice water, pyromellitic anhydride (PMDA) is added to the reaction vessel, and then 4,4'-diaminodiphenyl ether (DAPE) and 2'-methoxy 4,4'-diaminobenzanilide. (MABA) was added. The total amount of monomers charged was 15 wt%, the molar ratio of each diamine was MABA: DAPE = 60: 40, and the molar ratio of acid anhydride to diamine was 0.98: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 15,000 cps.

Synthesis example 2
After immersing the reaction vessel containing n-methylpyrrolidinone in ice water, PMDA and 3,4'3,4'-biphenyltetracarboxylic dianhydride (BTDA) were added to the reaction vessel, and then DAPE was added. . The total amount of monomers added was 15 wt%, the molar ratio of each acid anhydride was BTDA: PMDA = 70: 30, and the molar ratio of acid anhydride to diamine was 1.03: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 3,200 cps.

Synthesis example 3
After immersing the reaction vessel containing n-methylpyrrolidinone in ice water, 3,3'4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA) and PMDA are added to the reaction vessel, and then 1,3 -Bis (4-aminophenoxy) benzene (TPE-R) was added. The total amount of monomers charged was 15 wt%, the molar ratio of each acid anhydride was DSDA: PMDA, 90:10, and the molar ratio of acid anhydride to diamine was 1.03: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 3,200 cps.

Copper foil 1 was used as the copper foil. On the electrolytic copper foil, the polyamic acid solutions of Synthesis Examples 1, 2, and 3 were respectively applied at a mass ratio of 3: 14: 3 and dried, and an intermediate in which a polyimide precursor resin layer was formed on the copper foil layer. A laminate was obtained. This laminate was heat treated at 340 ° C. for 8 hours to obtain a laminate of single-sided copper foil having a polyimide resin thickness of 40 μm. The crystal grain size of the copper foil after this heat treatment was 2.2 μm. This laminate was chemically polished with an etching solution so as to have a conductor thickness of 8.0 μm to obtain a laminate.
In the laminate thus obtained, the surface roughness Rz of the conductor layer not in contact with the insulating layer was 0.8 μm.

A wiring pattern was formed on the laminate obtained above to obtain a COF film carrier tape. At this time, the circuit pattern of the inner lead part was produced at a 30 μm pitch.
In addition, the laminated board obtained above was subjected to predetermined circuit processing, and an MIT folding resistance test was performed.

  A copper foil 2 was used as the copper foil, and a laminate was produced in the same manner as in Example 1. The crystal grain size at this time was 2.4 μm. As a result of chemically polishing this laminate to 8.0 μm with an etching solution, a laminate having a resist surface side Rz of 0.6 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

Comparative Example 1
A copper foil 3 was used as the copper foil, and a laminate was produced in the same manner as in Example 1. The crystal grain size at this time was 0.9 μm. As a result of chemically polishing this laminate to 8.0 μm with an etching solution, a laminate having a resist surface side Rz of 0.4 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

Comparative Example 2
A copper foil 4 was used as the copper foil, and a laminate was produced in the same manner as in Example 1. The crystal grain size at this time was 0.8 μm. As a result of chemically polishing this laminate to 8.0 μm with an etching solution, a laminate having a resist surface side Rz of 1.0 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

  The results are summarized in Table 1. In Table 1, the MIT folding resistance is the result under test conditions with R = 0.8 mm and a 1/2 mil cover material.

Claims (2)

In a method for producing a copper clad laminate in which an insulating layer made of an insulating resin is formed on one surface of a copper foil, the copper foil has a thickness of 5 μm or more, and an electrolysis having a crystal grain size of less than 2 μm before heat treatment After using the copper foil and directly applying the polyimide precursor resin solution to one surface of the copper foil, the polyimide resin insulating layer is formed by heat treatment at 280 to 400 ° C., and the crystal grain size of the copper foil is changed. After obtaining a laminate having a thickness of 2 μm or more, the surface of the laminate that is not in contact with the insulating layer has a concentration (wt%) of 0.5 to 10% hydrogen peroxide and 0.5 to 15% sulfuric acid. A method for producing a copper-clad laminate, characterized in that 10 to 90% of the copper foil thickness is removed by chemical polishing with the contained etching solution and the surface roughness Rz is 2.5 μm or less. The method for producing a copper clad plate according to claim 1, wherein the copper foil thickness is 3 to 18 µm after chemical polishing with an etching solution to remove 10 to 90% of the copper foil thickness .