JP2007261174A - Manufacturing process of copper cladding laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of a copper cladding laminate in which handleability in laminate manufacturing is improved, microfabrication of at most 30 μm pitch is possible, and which is excellent in flexibility and a foldability resistance. <P>SOLUTION: The manufacturing process of the copper cladding laminate by which an insulating layer made of an insulating resin is formed in one surface of a copper foil, is characterized by using a rolling copper foil with a thickness of 10 μm or more as the copper foil, applying a polyimide precursor resin solution to one surface of this copper foil directly, then forming a polyimide resin insulating layer by heat treating at 100-400°C, and carrying out chemical polishing of the surface which is not in contact with the insulating layer of the obtained laminate with a liquid which contains 0.5-10% of hydrogen peroxide and the range of concentration (wt.%) of 0.5-15% of sulfuric acid so that the thickness of the copper foil is removed in the range of 10-90%, and its surface roughness Rz becomes 2.5 μm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a copper clad laminate, and more specifically, it can be finely processed as a chip-on-film (hereinafter referred to as COF) application, and has flexibility (or flexibility) and folding resistance. The present invention relates to a method for producing an excellent copper-clad laminate for a flexible printed circuit board.

  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 has been developed in which a bare IC chip is directly mounted on a film carrier tape as a mounting method for mounting at higher density in a smaller space. There is a need for a copper-clad laminate for flexible printed circuit boards.

  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 to a predetermined thickness. However, this manufacturing method has a fatal defect in the formation of a fine circuit in which minute holes are scattered in a metal layer called a pinhole and the circuit is inferior in electromigration resistance.

  The laminating method is a method of directly laminating a copper foil on a polyimide film. About this method, in order to obtain the copper clad laminated body which has high flexibility, it is proposed to use the rolled copper foil recrystallized annealing (for example, refer patent document 1). However, such a rolled copper foil is soft, and a thin copper foil having a thickness of 10 μm or less is likely to be deformed by handling during production of the laminate. In addition, it has been proposed to use an electrolytic copper foil having a small crystal orientation for a printed circuit board for a printed circuit board having good etching properties during circuit formation (see, for example, Patent Document 2). However, such a copper foil has a small crystal grain size, and it is difficult to obtain high flexibility and folding resistance, and the use of the product type used is limited.

  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 layered product before chemical polishing is prepared) and etched to obtain a target layered product. For example, in thinning of a copper foil part by chemical polishing in laminate production, an electrolytic copper foil has been proposed in which chemical polishing proceeds uniformly and the surface of the copper foil after chemical polishing is smooth (for example, Patent Document) 3). However, electrolytic copper foil does not have sufficient folding resistance as much as rolled copper foil.

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

  In view of such circumstances, the present invention provides a method for producing a copper-clad laminate that improves handling properties in laminate production, enables fine processing of a pitch of 30 μm or less, and is excellent in flexibility and folding resistance. It is something to be offered.

  The present inventors use a rolled copper foil having a specific thickness and predetermined characteristics, and after forming a polyimide resin insulating layer on the copper foil by a casting method under predetermined conditions, the rolled copper foil surface is maintained under certain conditions. When the thickness of the copper foil is reduced and the surface roughness Rz of the treated surface is kept within a certain range, the manufacturing process of the copper-clad laminate is improved, and fine processing when used for a printed circuit board is reduced. The present inventors have found that it is possible and has sufficient flexibility and folding resistance, and have reached the present invention.

  That is, the method for producing a copper clad laminate of the present invention is characterized by the following configuration or structure.

  (1). In the 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, a rolled copper foil having a thickness of 10 μm or more is used as the copper foil, and one of the copper foils The polyimide precursor resin solution was directly applied to the surface of the substrate, and then heat-treated at 100 to 400 ° C. to form a polyimide resin insulating layer. Hydrogen peroxide was 0.5 to 10% and sulfuric acid was 0.5 to 15%. The surface of the resulting laminate that is not in contact with the insulating layer is chemically polished with a solution containing a range concentration (wt%) so that the thickness of the copper foil is removed in the range of 10 to 90%. A method for producing a copper clad laminate, wherein the surface roughness Rz is 2.5 μm or less.

(2). The method for producing a copper-clad laminate according to (1) above, wherein the surface roughness Rz of the rolled copper foil before chemical polishing of the surface not in contact with the insulating layer of the laminate is 1.5 μm or less. .
(3). The method for producing a copper-clad laminate according to (1) or (2) above, wherein the rolled copper foil before the formation of the polyimide resin insulating layer is a rolled copper foil having a reduction rate of 90% or more.
(4). The rolled copper foil before the formation of the polyimide resin insulating layer is a rolled copper foil having a tensile strength of 420 MPa or more, The production of a copper clad laminate according to any one of the above (1) to (3) Method.
(5). When the rolled copper foil before the formation of the polyimide resin insulating layer has a modulus of elasticity before the formation of the polyimide resin insulating layer of 100%, the rolled copper foil having an elastic modulus of 60% or less after heat treatment at 360 ° C. for 6 minutes. The method for producing a copper clad laminate according to any one of (1) to (4) above, wherein
(6). The laminated body is a chip-on-film laminated body used for mounting a semiconductor element, The production of a copper-clad laminated body according to any one of (1) to (5) above Method.
According to the above means, the following effects can be obtained.

  According to the present invention, based on a rolled copper foil having excellent flexibility, the adhesive strength between the conductor and the insulator is high, the electromigration resistance is excellent, fine processing of 30 μm pitch or less is possible, and the flexibility And the copper clad laminated body which is excellent in bending resistance is obtained. Thereby, it can utilize effectively as a COF use for flexible printed circuit boards.

Embodiments of the present invention will be described below.
The copper clad laminate according to 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 used in the present invention is pure copper or a copper alloy, and these are rolled copper foils.

  The rolled copper foil is generally known as a highly flexible copper foil. When the thickness of the copper foil is less than 10 μm, the copper foil itself becomes soft and easily deformed by handling during production of the laminate. Moreover, it becomes difficult to roll copper foil, and it tends to be difficult to obtain a shape applicable to laminate production. For example, uneven copper foil thickness, sagging ends, and flare are generated. Furthermore, the uneven thickness of the copper foil causes a bad influence on the accuracy of chemical polishing and also adversely affects the circuit workability. Therefore, the thickness of the copper foil at the time of manufacturing the laminate according to the present invention needs to be 10 μm or more. Preferably it is 11-35 micrometers, More preferably, 12-18 micrometers is good. When the thickness of the copper foil is larger than 35 μm, it takes time to reduce the thickness by chemical polishing described later.

  The surface roughness Rz on the side where the insulating layer of the copper foil is provided is 3.0 μm or less, preferably 2.0 μm or less, and more preferably 1.2 μm or less. When the surface roughness Rz is larger than 3.0 μm, an etching residue is generated when an insulating layer is formed thereon and the conductor is removed and fine processing is performed, and the linearity of the circuit is impaired. The surface roughness Rz represents “10-point average roughness” and is measured according to JIS B 0601. Hereinafter, unless otherwise specified, the surface roughness Rz is a value measured in the same manner.

  About the insulating layer which forms a laminated body, 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, 4,4′-diamino-2′-methoxybenzanilide, 1,4-bis (4-aminophenoxy) benzene, and 1,3-bis (4 -Aminophenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4 Examples include '-diaminobiphenyl, 4,4'-diaminobenzanilide and the like. Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride. Products, 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.

  The organic solvent used in the production of the polyimide resin precursor according to the present invention is not particularly limited, but may be a mixed solvent in which one or two or more kinds are used in combination as long as the resin component can be uniformly dissolved. There is no problem. For example, there are N, N-dimethylacetamide (DMAc), n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like.

  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. The copper foil that forms this copper foil layer is annealed or re-annealed during the heat treatment step of the polyimide precursor resin solution, and becomes softer than before lamination.

  About the laminated body of the intermediate body manufactured above, the copper foil surface which is not in direct contact with the insulating layer is made of hydrogen peroxide 0.5 to 10% (wt%) and sulfuric acid 0.5 to 15% (wt%). By chemical polishing with an etching solution in the range, 10 to 90% of the copper foil thickness is removed to obtain a copper-clad laminate according to the present invention. And the thickness of the copper foil of the copper clad laminated body finally obtained is 3-18 micrometers, Preferably it is good to set it as 5-12 micrometers. When the thickness of the copper foil is larger than 18 μm, not only bending resistance and folding resistance are lowered, but also fine processing in a circuit becomes difficult. When the thickness of the copper foil is less than 3 μm, there is a tendency to cause disconnection due to a decrease in the mechanical strength of the copper foil and a decrease in current capacity.

  The surface roughness Rz of the copper foil after chemical polishing is 2.5 μm or less. Preferably it is 1.5 micrometers or less, More preferably, it is 1.0 micrometers 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.

  Further, the surface roughness Rz of the rolled copper foil before chemical polishing of the surface not in contact with the insulating layer of the laminate according to the present invention is preferably 1.5 μm or less. More preferably, it is 1.0 micrometer or less, More preferably, it is 0.8 micrometer or less. When the surface roughness Rz is larger than 1.5 μm, it is difficult to control the surface roughness by the chemical polishing.

  The rolled copper foil before formation of the polyimide resin insulating layer according to the present invention is preferably a rolled copper foil having a rolling reduction of 90% or more. By setting the rolling reduction to 90% or more, the copper crystal structure is sufficiently refined and homogenized, so that necessary mechanical strength can be obtained. More preferably, it is 90 to 95%. If the rolling reduction is less than 90%, it is difficult to obtain the required mechanical strength, and it is necessary to lengthen the annealing time in the subsequent annealing step. The rolling reduction is calculated by the formula of rolling reduction (%) = L / Lo × 100, based on the copper foil thickness (Lo) before rolling and the copper foil thickness (L) after rolling.

  The rolled copper foil used in the present invention preferably has a tensile strength of 420 MPa or more. More preferably, it is 450 MPa or more, and more preferably 480 MPa or more. If the tensile strength of the copper foil is less than 420 MPa, sufficient strength cannot be obtained, and the problem of wrinkles and breakage during the production of the laminate tends to occur.

  The flexibility of the copper foil is remarkably improved as compared with the rolling rise by annealing. In the manufacturing method of the laminated body concerning this invention, annealing or re-annealing of copper foil is performed using the heat treatment process after apply | coating a polyimide precursor resin liquid on a copper foil layer. Therefore, the rolled copper foil before the formation of the polyimide resin insulation layer has a modulus of elasticity of 60% or less after heat treatment at 360 ° C. for 6 minutes, assuming that the elastic modulus before the formation of the polyimide resin insulation layer is 100%. It is good that it is copper foil. If this elastic modulus exceeds 60%, it is likely to be deformed by handling in the polyimide precursor resin liquid coating process.

  In addition, the manufacturing method of the copper clad laminated body of this invention is not limited to above-described embodiment, Of course, various changes can be added in the range which does not deviate from the summary of this invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In addition, the measurement of the various physical properties in an Example is based on the following method.

[Measurement of copper foil thickness after chemical polishing]
In the laminate according to the present invention, the thickness at 30 points was measured at 10 mm intervals in the width direction using a dial gauge (manufactured by Mitutoyo). Thereafter, the copper portion was etched (thinned), and the thickness of the polyimide resin layer was measured in the same manner. The thickness of the copper foil after chemical polishing was calculated from the difference between the thickness of the laminate and the thickness of the polyimide resin layer.

[Measurement of tensile strength of copper foil]
A strip-shaped test piece having a width of 12.7 mm and a length of 254 mm was cut out and measured using a tensile testing machine (Toyo Seiki Co., Ltd., Strograph-R1) at a crosshead speed of 50 mm / min and a chuck distance of 50.8 mm. The displacement (elongation) during the tensile test was determined, and the 0.2% yield strength was calculated from the SS curve.

[Measurement of surface roughness of copper foil]
Using an ultra-deep shape measuring microscope (manufactured by KEYENCE, VK-8500), it was measured at a magnification of 2000 in the length direction of the copper foil surface by 140 μm.

[Measurement of elastic modulus of copper foil]
Using a universal testing machine (STROGRAPH-R1) manufactured by Toyo Seiki Seisakusho Co., Ltd., measurement was performed in an environment of 23 ° C. and 50% RH.

In creating the laminate, the following two types of copper foils were prepared.
1). Copper foil 1: Rolled copper foil, thickness 12 μm, insulating layer side Rz 1.0 μm, resist surface side Rz 0.8 μm, reduction ratio 95%, tensile strength 510 MPa, 360 ° C., elastic modulus 49% after 6 minutes heat treatment (lamination (For elastic modulus of 100% before body formation)
2). Copper foil 1b: Rolled copper foil, thickness 18 μm, insulating layer side Rz 1.0 μm, resist surface side Rz 0.8 μm, reduction ratio 95%, tensile strength 510 MPa, 360 ° C., elastic modulus 65% after 6 minutes heat treatment (lamination (For elastic modulus of 100% before body formation)
3). Copper foil 2: electrolytic copper foil, thickness 15 μm, insulating layer side Rz 0.8 μm, resist surface side Rz 1.7 μm
4). Copper foil 3: electrolytic copper foil, thickness 12 μm, insulating layer side Rz 0.6 μm, resist surface side Rz 0.8 μm
5). Copper foil 4: Rolled copper foil, thickness 18 μm, insulating layer side Rz 1.8 μm, resist surface side Rz 1.8 μm, rolling reduction 90%, tensile strength 440 MPa, 360 ° C., elastic modulus 65% after 6 minutes heat treatment (lamination (For elastic modulus of 100% before body formation)

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

(Synthesis Example 1)
N-methylpyrrolidinone is put into a reaction vessel capable of introducing a thermocouple, a stirrer and nitrogen. After soaking the reaction vessel in ice water, pyromellitic anhydride (PMDA) was charged into 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 the reaction vessel containing n-methylpyrrolidinone was immersed in ice water, PMDA and 3,3′4,4′-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 were introduced into 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.

Example 1
Copper foil 1 was used as the copper foil. On this rolled 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 a laminate in which a polyimide precursor resin layer was formed on the copper foil layer was obtained. Obtained. This laminated body was heat-treated at 340 ° C. for 8 hours to obtain a laminated body of a single-sided copper foil intermediate having a polyimide resin thickness of 40 μm. This laminate was chemically polished with the above etching solution so that the copper foil conductor thickness was uniformly 8 μm to obtain a laminate. In the laminated body thus obtained, the surface roughness Rz of the conductor layer not in contact with the insulating layer was 0.9 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 portion was produced at a pitch of 40 μm.
Further, the laminated body obtained above was subjected to predetermined circuit processing and subjected to an MIT folding resistance test.

  The copper foil 1b was used as the copper foil, and an intermediate laminate was produced in the same manner as in Example 1. This laminate was chemically polished to 8 μm with an etching solution, and as a result, a laminate having a resist surface side Rz of 1.8 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

(Comparative Example 1)
A copper foil 2 was used as the copper foil, and an intermediate laminate was produced in the same manner as in Example 1. As a result of chemically polishing this laminated body to 8 μm with an etching solution, a laminated body having a resist surface side Rz of 0.8 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

(Comparative Example 2)
A copper foil 3 was used as the copper foil, and an intermediate laminate was produced in the same manner as in Example 1. As a result of chemically polishing this laminated body to 8 μm with an etching solution, a laminated body having a resist surface side Rz of 0.8 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

(Comparative Example 3)
A copper foil 4 was used as the copper foil, and an intermediate laminate was produced in the same manner as in Example 1. As a result of performing chemical polishing of this laminated body to 8 μm with an etching solution, a laminated body having a resist surface side Rz of 3.2 μm was obtained. The same circuit processing and MIT test as in Example 1 were performed.

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

  From the results in Table 1, it can be seen that flexibility and folding resistance are further improved by thinning the copper foil conductor of the rolled copper foil by chemical polishing.

  The method for producing a copper clad laminate of the present invention has good handleability for laminating a copper foil with a polyamide resin insulating layer, and the produced copper clad laminate can be finely processed. Is highly available.

Claims (6)

  In the 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, a rolled copper foil having a thickness of 10 μm or more is used as the copper foil, and one of the copper foils The polyimide precursor resin solution was directly applied to the surface of the substrate, and then heat-treated at 100 to 400 ° C. to form a polyimide resin insulating layer. Hydrogen peroxide was 0.5 to 10% and sulfuric acid was 0.5 to 15%. The surface of the resulting laminate that is not in contact with the insulating layer is chemically polished with a solution containing a range concentration (wt%) so that the thickness of the copper foil is removed in the range of 10 to 90%. A method for producing a copper clad laminate, wherein the surface roughness Rz is 2.5 μm or less.   The method for producing a copper clad laminate according to claim 1, wherein the surface roughness Rz of the rolled copper foil before chemical polishing of the surface not in contact with the insulating layer of the laminate is 1.5 μm or less.   The method for producing a copper-clad laminate according to claim 1 or 2, wherein the rolled copper foil before forming the polyimide resin insulating layer is a rolled copper foil having a reduction rate of 90% or more.   The method for producing a copper-clad laminate according to any one of claims 1 to 3, wherein the rolled copper foil before the formation of the polyimide resin insulating layer is a rolled copper foil having a tensile strength of 420 MPa or more. When the rolled copper foil before the formation of the polyimide resin insulating layer has a modulus of elasticity before the formation of the polyimide resin insulating layer of 100%, the rolled copper foil having an elastic modulus of 60% or less after heat treatment at 360 ° C. for 6 minutes. The method for producing a copper-clad laminate according to any one of claims 1 to 4, wherein:   The method for producing a copper-clad laminate according to any one of claims 1 to 5, wherein the laminate is a laminate for chip-on-film used for mounting a semiconductor element.