KR102234045B1 - Copper-clad laminate, printed wiring board and method of using thereof - Google Patents

Abstract

(Problem) Provided are a copper clad laminate, a printed wiring board, and a method of using the same, which enable countermeasures to a high frequency increase accompanying miniaturization and high performance of electronic devices.
(Solution means) The copper clad laminate includes a polyimide insulating layer and a copper foil on at least one surface of the polyimide insulating layer. The polyimide insulating layer has a thermal line expansion coefficient in the range of 0 ppm/K or more and 30 ppm/K or less, and the formula (i); E ₁ = √ε ₁ × Tanδ ₁ … (i)
[Here, ε ₁ represents the dielectric constant at 3 GHz by the cavity resonator perturbation method, and Tanδ ₁ represents the dielectric tangent at 3 GHz by the cavity resonator perturbation method.] _{The value of E 1} , which is an index indicating that, is less than 0.009. In addition, the copper foil has a square average roughness (Rq) of 0.05 µm or more and less than 0.5 µm of a surface in contact with the polyimide insulating layer.

Description

Copper clad laminate, printed wiring board, and how to use the same {COPPER-CLAD LAMINATE, PRINTED WIRING BOARD AND METHOD OF USING THEREOF}

The present invention relates to a copper clad laminate having a polyimide insulating layer and a copper foil layer, and a printed wiring board obtained by processing the copper foil layer of the copper clad laminate into a wiring circuit, and a method of using the same.

In recent years, with the progress of miniaturization, weight reduction, and space saving of electronic devices, the demand for flexible printed circuits (FPCs) that are thin, lightweight, flexible, and having excellent durability even when bending is repeated is increasing. have. Since FPC can be mounted in three-dimensional and high-density even in a limited space, for example, it can be used as a component such as a wiring or a cable or a connector for moving parts of electronic devices such as HDDs, DVDs, and mobile phones. It is expanding.

In addition to the above-described high-density increase, since the high-performance of the device has progressed, it is also necessary to cope with the high frequency of the transmission signal. In information processing and information communication, measures have been taken to increase the transmission frequency in order to transmit and process large amounts of information, and the printed circuit board material reduces the transmission loss due to the thinning of the insulating layer and the low flow rate of the insulating layer. Lowering is being demanded. Conventional FPC using polyimide has a high dielectric constant and dielectric tangent of a polyimide, and a high transmission loss in a high frequency range, making it difficult to adapt to a high frequency. Therefore, up to now, in order to cope with high frequency, FPCs made of a liquid crystal polymer characterized by a low dielectric constant and a low dielectric tangent as a dielectric layer have been mainly used. However, although the liquid crystal polymer is excellent in dielectric properties, there is room for improvement in heat resistance and adhesion to metal foil.

In order to improve heat resistance and adhesion, a metal-clad laminate made of polyimide as an insulating layer has been proposed (Patent Document 1). According to Patent Document 1, it is generally known that the dielectric constant is lowered by using an aliphatic monomer as a polymer material, but the heat resistance of a polyimide obtained using an aliphatic (chain type) tetracarboxylic dianhydride is remarkably low. Therefore, it becomes impossible to provide for processing such as solder, and it is said that there is a problem in practical use. Moreover, in Patent Document 1, it is said that, when an alicyclic tetracarboxylic dianhydride is used, a polyimide having improved heat resistance compared to that of a chain type can be obtained. However, such a polyimide film had a dielectric constant of 3.2 or less at 10 GHz, but the dielectric tangent exceeded 0.01, and the dielectric properties were still not sufficient.

In order to improve dielectric properties, a copper clad laminate has been proposed in which the concentration of imide groups in a polyimide layer in contact with a copper foil forming a conductor circuit is controlled (Patent Document 2). According to Patent Document 2, it is said that the dielectric properties can be controlled by the combination of the surface roughness (Rz) of the copper foil and the polyimide layer having a low imide group concentration on the surface in contact with the copper foil, but there is a limit to the control, and the transmission characteristics Was not enough to be satisfied.

Japanese Laid-Open Patent Publication No. 2004-358961 Japanese Patent Publication No. 5031639

An object of the present invention is to provide a copper clad laminate, a printed wiring board, and a method of using the same, which enables countermeasures to a high frequency increase accompanying miniaturization and high performance of electronic devices.

In order to solve the above-described problem, the present inventors focused on the skin effect in the copper foil, using a copper foil having a specific surface state as a conductor layer, and using a polyimide having a specific dielectric property for the insulating layer, It has been found that a circuit board such as an FPC having excellent transmission characteristics in a high frequency region can be obtained, and the present invention has been completed.

That is, the copper clad laminate of the present invention includes a polyimide insulating layer and a copper foil on at least one surface of the polyimide insulating layer. In the copper clad laminate of the present invention, the polyimide insulating layer has the following configurations Ia and Ib:

Ia) The coefficient of thermal expansion is in the range of 0 ppm/K or more and 30 ppm/K or less;

Ib) the following equation (i),

E ₁ = √ε ₁ × Tanδ ₁ … (i)

[Here, ε ₁ represents the dielectric constant at 3 GHz by the cavity resonator perturbation method, and Tanδ ₁ represents the dielectric tangent at 3 GHz by the cavity resonator perturbation method.]

_{The value of E 1} which is an index indicating dielectric properties calculated based on is less than 0.009;

And, in addition, the copper foil, the following configuration c:

c) The average square roughness (Rq) of the surface in contact with the polyimide insulating layer is within a range of 0.05 µm or more and less than 0.5 µm;

It is equipped with.

In the copper clad laminate of the present invention, the dielectric constant may be 3.1 or less, and the dielectric tangent may be less than 0.005.

In the copper clad laminate of the present invention, the arithmetic mean height (Ra) of the surface of the copper foil in contact with the polyimide insulating layer may be 0.2 µm or less.

The copper clad laminate of the present invention may have a 10-point average roughness (Rz) of 1.5 µm or less on a surface of the copper foil in contact with the polyimide insulating layer.

The copper clad laminate of the present invention may have a dielectric constant of 3.0 or less in 10 GHz of the polyimide insulating layer and a dielectric tangent of 0.005 or less.

The printed wiring board of the present invention is obtained by processing the copper foil of any of the above-described copper clad laminates into a wiring circuit.

In the method of using the printed wiring board of the present invention, it is preferable to use the printed wiring board in a frequency range within the range of 1 GHz to 40 GHz, and more preferably use in a frequency range within the range of 1 GHz to 20 GHz.

The copper clad laminate of the present invention can effectively utilize the dielectric properties of the polyimide insulating layer by suppressing an increase in resistance due to the skin effect of the copper foil, and thus can be preferably used as an electronic material requiring high-speed signal transmission.

1 is a graph showing the results of Example 1 and Reference Examples 1-3.
2 is a graph showing the results of simulations (1) to (6).
3 is a graph showing the results of simulations (7) to (12).

Hereinafter, an embodiment of the present invention will be described.

<Copper clad laminate>

The copper clad laminate of the present embodiment is a copper clad laminate comprising a polyimide insulating layer and a copper foil layer on at least one surface of the polyimide insulating layer, and is a single-sided copper having copper foil on only one side of the polyimide insulating layer. A coated laminate may be sufficient, or a double-sided copper clad laminate provided with copper foil on both sides of the polyimide insulating layer may be used. In addition, the double-sided copper-clad laminate is formed by, for example, forming a single-sided copper-clad laminate and then making the polyimide insulating layers face each other and pressing by hot pressing, or on the polyimide insulating layer of the single-sided copper clad laminate. It can be obtained by forming a copper foil by pressing it.

<Polyimide insulating layer>

As the polyimide forming the polyimide resin layer, including so-called polyimide, heat-resistant resins having an imide group in structures such as polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, polysiloxaneimide, etc. have.

Although the polyimide insulating layer has a coefficient of thermal expansion in the range of 0 to 30 ppm/K, by controlling it within such a range, it is possible to suppress warpage and decrease in dimensional stability when a copper clad laminate is formed. Moreover, although the polyimide insulating layer has a single layer or a polyimide layer of multiple layers, application as a base film layer (main layer of an insulating resin layer) of a polyimide layer of low thermal expansion is preferable. Specifically, the coefficient of thermal expansion is in the range of 1 × 10 ^-6 to 30 × 10 ^-6 (1/K), preferably in the range of 1 × 10 ^-6 to 25 × 10 ^-6 (1/K) , More preferably, a large effect is obtained when a polyimide layer having low thermal expansion properties in the range of ^{15 × 10 -6} to 25 × 10 ^{-6 (1/K) is applied to the base film layer.} On the other hand, it is also preferable to apply a polyimide layer exceeding the thermal-ray expansion coefficient as an adhesive layer with a copper foil layer. As a polyimide that can be preferably used as such an adhesive polyimide layer, the glass transition temperature is preferably 350°C or less, and more preferably in the range of 200 to 320°C.

The thickness of the polyimide insulating layer is, for example, in the range of 6 to 50 µm, and preferably in the range of 9 to 45 µm. If the thickness of the polyimide insulating layer is less than 6 µm, there is a concern that problems such as wrinkles may occur during transport in the manufacture of copper-clad laminates, etc. On the other hand, if the thickness of the polyimide insulating layer exceeds 50 µm, copper coating There is a concern that a problem may occur in dimensional stability or flexibility during manufacture of the laminated plate. Further, when forming a polyimide insulating layer from a plurality of polyimide layers, the total thickness may be within the above range.

(Genetic characteristics)

The polyimide insulating layer is an insulating resin layer as a whole in order to secure the transmission characteristics in a high frequency band when used for a circuit board such as a flexible circuit board (hereinafter sometimes referred to as "FPC"). _{The value of E 1} , which is an index indicating dielectric properties at 3 GHz by the cavity resonator perturbation method calculated based on formula (i), is less than 0.009, preferably in the range of 0.0025 to 0.007, and more preferably A range of 0.0025 to 0.006 is good. When the E ₁ value exceeds the above upper limit, when used for a circuit board such as an FPC, problems such as electric signal loss are liable to occur on a transmission path of a high frequency signal.

(Dielectric constant and dielectric tangent)

When the polyimide insulating layer is used for a circuit board such as an FPC, the dielectric constant at 3 GHz is in the range of 1 to 40 GHz to achieve a transmission loss equivalent to that of a copper clad laminate produced using a liquid crystal polymer. (ε ₁ ) is preferably 3.1 or less, and the dielectric tangent (Tanδ ₁ ) is preferably less than 0.005. When the dielectric constant at 3 GHz of the polyimide insulating layer exceeds 3.1 and the dielectric tangent is 0.005 or more, the problem of electric signal loss tends to occur when used for a circuit board such as an FPC.

In addition, the polyimide insulating layer preferably has a dielectric tangent of less than 0.005 at 3 GHz in order to lower the transmission loss to a level equivalent to that of a liquid crystal polymer when used for a circuit board such as an FPC. When the dielectric tangent at 3 GHz of the polyimide insulating layer is 0.005 or more, when used for a circuit board such as an FPC, an electric signal loss occurs on a transmission path of a high frequency signal.

In addition, when the polyimide insulating layer is used for a circuit board such as an FPC, in order to reduce the transmission loss to a level equivalent to that of a liquid crystal polymer, the dielectric constant at 10 GHz is preferably 3.0 or less, and the dielectric tangent is 0.005 or less. It is good. By controlling the dielectric properties of the polyimide insulating layer within such a range, it is possible to suppress a transmission loss on a transmission path of a high-frequency signal when used for a circuit board such as an FPC.

From the ease of control of the thickness and physical properties of the polyimide insulating layer, it is preferable to use a so-called cast (coating) method in which a polyamic acid solution is applied directly onto the copper foil and then dried and cured by heat treatment. In addition, when the polyimide insulating layer is formed into a plurality of layers, it can be formed by sequentially applying another polyamic acid solution onto a polyamic acid solution composed of different constituent components. When the polyimide insulating layer consists of a plurality of layers, a polyimide precursor resin having the same configuration may be used two or more times.

A particularly preferred polyimide for forming the polyimide insulating layer is a dimer in which an acid anhydride component containing an aromatic tetracarboxylic anhydride and two terminal carboxylic acid groups of a dimer acid are substituted with a primary aminomethyl group or an amino group. As a polyimide obtained by reacting a diamine component containing an acid-type diamine and an aromatic diamine, it is preferable that the dimer acid-type diamine is in the range of 4 to 40 mol% with respect to all the diamine components.

Such a polyimide is preferably a polyimide having a structural unit represented by the following general formulas (1) and (2).

[Formula 1]

[In the formula, Ar is a tetravalent aromatic group derived from an aromatic tetracarboxylic anhydride, R ₁ is a divalent dimer acid type diamine residue derived from a dimer acid type diamine, and R ₂ is a divalent aromatic diamine residue derived from an aromatic diamine. Respectively, m and n represent the molar ratios of each constituent unit, m is in the range of 0.04 to 0.4, and n is in the range of 0.6 to 0.96]

The group Ar includes, for example, what is represented by the following formula (3) or formula (4).

[Formula 2]

[Wherein, W is a single bond, a divalent hydrocarbon group having 1 to 15 carbon atoms, -O-, -S-, -CO-, -SO-, -SO ₂ -, -NH- or -CONH- Represents a divalent group]

In particular, from the viewpoint of reducing the polar group of the polyimide and improving the dielectric properties, as the group Ar, W in the formula (3) or (4) is a single bond, a divalent hydrocarbon group having 1 to 15 carbon atoms, -O- , It is preferably represented by -S-, -CO-, more preferably W in formula (3) or formula (4) is represented by a single bond, a C1-C15 divalent hydrocarbon group, or -CO- Do.

Moreover, the structural units represented by the said general formulas (1) and (2) may exist in a homopolymer, and may exist as a structural unit of a copolymer. In the case of a copolymer having a plurality of structural units, it may exist as a block copolymer or may exist as a random copolymer.

Since polyimides are generally prepared by reacting an acid anhydride and a diamine, specific examples of the polyimide will be understood by describing the acid anhydride and a diamine. In the general formulas (1) and (2), the group Ar can be said to be a residue of an acid anhydride, and the groups R ₁ and R ₂ can be said to be residues of a diamine. Explained by.

As an acid anhydride having the group Ar as a residue, for example, pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl Sulfonetetracarboxylic dianhydride and 4,4'-oxydiphthalic anhydride are preferably exemplified. Further, as an acid anhydride, for example, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-diphenyl Ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3",4,4"-, 2,3,3",4"- or 2,2",3 ,3"-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3,4- Dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic acid 2 Anhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid 2 Anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6, 7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2, 3,6,7- (or 1,4,5,8-) tetrachloronaphthalene-1,4,5,8- (or 2,3,6,7-) tetracarboxylic dianhydride, 2,3 ,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3 ,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2 ,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, etc. are mentioned. have.

Group R ₁ is a divalent dimer acid type diamine residue derived from a dimer acid type diamine. The dimer acid-type diamine means a diamine obtained by substituting two terminal carboxylic acid groups (-COOH) of a dimer acid with a primary aminomethyl group (-CH ₂ -NH ₂ ) or an amino group (-NH _{2 ).}

Dimeric acid is a known dibasic acid obtained by intermolecular polymerization of an unsaturated fatty acid, and its industrial production process is almost standardized in the industry, and is obtained by dimerizing an unsaturated fatty acid having 11 to 22 carbon atoms with a clay catalyst or the like. The industrially obtained dimer acid is mainly composed of a dibasic acid having 36 carbon atoms obtained by dimerizing an unsaturated fatty acid having 18 carbon atoms such as oleic acid or linoleic acid, but depending on the degree of purification, an arbitrary amount of monomeric acid (carbon number 18) or trimer acid (carbon number 54 ), and other polymerized fatty acids having 20 to 54 carbon atoms. In the present invention, it is preferable to use a dimer acid in which the dimer acid content is increased to 90% by weight or more by molecular distillation. In addition, although a double bond remains after the dimerization reaction, in the present invention, a further hydrogenation reaction to reduce the degree of unsaturation is also included in the dimer acid.

As a characteristic of the dimer acid-type diamine, a characteristic derived from the skeleton of the dimer acid can be imparted. That is, since the dimer acid-type diamine is an aliphatic macromolecule having a molecular weight of about 560 to 620, the molar volume of the molecule can be increased to relatively reduce the polar group of the polyimide. It is considered that such a characteristic of the dimer acid type diamine will contribute to improving the dielectric properties while suppressing the decrease in the heat resistance of the polyimide. In addition, since it has two freely movable hydrophobic chains of 7 to 9 carbon atoms and two chain-type aliphatic amino groups having a length close to 18 carbon atoms, not only provides flexibility to polyimide, but also non-polyimide Since the target chemical structure or non-planar chemical structure can be used, it is thought that the low dielectric constant of the polyimide can be achieved.

The injection amount of the dimer acid type diamine is in the range of 4 to 40 mol%, preferably in the range of 4 to 30 mol%, and more preferably in the range of 4 to 15 mol% with respect to the total diamine component. When the dimer acid type diamine is less than 4 mol%, the dielectric properties of the polyimide tend to decrease, and when it exceeds 40 mol%, the heat resistance tends to deteriorate due to a decrease in the glass transition temperature of the polyimide.

The dimer acid type diamine is commercially available, and for example, the Kuroda Japan company PRIAMINE1073 (trade name), the same PRIAMINE1074 (brand name), the Cognis Japan company's Basamine 551 (brand name), and the same Basamine 552 ( Brand name) and the like.

Moreover, what is represented by following formula (5)-formula (7) is mentioned, for example as _{group R 2.}

[Formula 3]

[In formulas (5) to (7), R ₃ independently represents a C 1 to C 6 monovalent hydrocarbon group or an alkoxy group, and Z is a single bond, a C 1 to C 15 divalent hydrocarbon group, -O- , -S-, -CO-, -SO-, -SO ₂ -, -NH- or -CONH- represents a divalent group selected from, and n ₁ independently represents an integer of 0 to 4]

In particular, from the viewpoint of reducing the polar group of the polyimide and improving the dielectric properties, as the group R ₂ , Z in the formulas (5) to (7) is a single bond, a divalent hydrocarbon group having 1 to 15 carbon atoms, and R ₃ is It is preferable that a C1-C6 monovalent hydrocarbon group and n ₁ are an integer of 0-4.

Examples of the diamine having the group R ₂ as a residue include 4,4'-diaminodiphenyl ether, 2'-methoxy-4,4'-diaminobenzanilide, 1,4-bis(4-amino Phenoxy)benzene, 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'-diaminobiphenyl, 4,4'-diaminobenzanilide, 2,2-bis-[4-(3-aminophenoxy )Phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)]biphenyl, Bis[4-(3-aminophenoxy)biphenyl, bis[1-(4-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(4 -Aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl] ether, bis[4-(3-aminophenoxy) Phenyl] ether, bis[4-(4-aminophenoxy)]benzophenone, bis[4-(3-aminophenoxy)]benzophenone, bis[4,4'-(4-aminophenoxy)]benz Anilide, bis[4,4'-(3-aminophenoxy)]benzanilide, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, 9,9-bis[4-(3 -Aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl ]Hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 4, 4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodi Phenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 3 ,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-dia Minobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzi Dine, 4,4"-diamino-p-terphenyl, 3,3"-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 1, 4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline , 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl) ether , Bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1, 5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p -Xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4 -Oxadiazole, piperazine, etc. are mentioned.

Based on the dielectric properties of the polyimide, the aromatic tetracarboxylic anhydride preferably used in the preparation of the polyimide precursor is, for example, 3,3',4,4'-biphenyltetracarboxylic dianhydride. (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), pyro Melitic dianhydride (PMDA), etc. are mentioned. Among them, particularly preferred acid anhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride. (BTDA), etc. are mentioned. These aromatic tetracarboxylic anhydrides may be blended in combination of two or more.

In addition to the above acid anhydride, siloxane tetracarboxylic dianhydride can also be preferably used, and examples thereof include siloxane tetracarboxylic dianhydride represented by the following general formula (8).

[Formula 4]

Of the formula (8), R, R 'is independently an aliphatic group or an aromatic trivalent group having a carbon number of 1 to 4, R ₄ ~ R ₇ are, each independently, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have a substituent , n represents an integer of 1 to 50, but the average number of repetitions is 1 to 20]

In addition to the above acid anhydride, siloxane tetracarboxylic dianhydride can also be preferably used, and examples thereof include siloxane tetracarboxylic dianhydride represented by the following general formula (9).

[Formula 5]

[In formula (9), R ₁₁ and R ₁₂ independently represent a divalent hydrocarbon group, R ₄ to R ₇ independently represent a hydrocarbon group having 1 to 6 carbon atoms which may have a substituent, and n is 1 to 50 Represents an integer, but the average number of repetitions is 1 to 20]

In addition, based on the dielectric properties of the polyimide, examples of aromatic diamines preferably used in the preparation of a polyimide precursor include 2,2-bis(4-aminophenoxyphenyl)propane (BAPP), 2 ,2'-divinyl-4,4'-diaminobiphenyl (VAB), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl- 4,4'-diaminobiphenyl, 2,2',6,6'-tetramethyl-4,4'-diaminobiphenyl, 2,2'-diphenyl-4,4'-diaminobiphenyl And 9,9-bis(4-aminophenyl)fluorene. Among them, particularly preferred diamine components include 2,2-bis(4-aminophenoxyphenyl)propane (BAPP), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 2, 2'-dimethyl-4,4'-diaminobiphenyl (m-TB), and the like. These aromatic diamines can also be blended in combination of two or more.

Each of the above acid anhydrides and diamines may be used alone or in combination of two or more. In addition, other diamines and acid anhydrides not included in the general formulas (1) and (2) may be used together with the acid anhydrides or diamines, and in this case, the ratio of use of other acid anhydrides or diamines is preferably It is good to set it as 10 mol% or less, More preferably, it is 5 mol% or less. Thermal expansion properties, adhesion properties, glass transition temperature, and the like can be controlled by selecting the types of acid anhydrides and diamines, and respective molar ratios when two or more types of acid anhydrides or diamines are used.

Polyimide having the structural units represented by the general formulas (1) and (2) can be prepared by reacting the aromatic tetracarboxylic anhydride, dimer acid-type diamine and aromatic diamine in a solvent to produce a precursor resin, followed by heating and cyclization. I can. For example, an acid anhydride component and a diamine component are dissolved in an organic solvent in substantially equimolar amounts, and stirred for 30 minutes to 24 hours at a temperature within the range of 0 to 100°C for polymerization to obtain a polyamic acid as a precursor of a polyimide. In the reaction, the reaction component is dissolved so that the resulting precursor is in the range of 5 to 30% by weight, preferably 10 to 20% by weight in the organic solvent. Examples of the organic solvent used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, and dimethylsulfoxide. Seed, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and the like. Two or more of these solvents may be used in combination, and further, aromatic hydrocarbons such as xylene and toluene may be used in combination. In addition, the amount of such an organic solvent is not particularly limited, but the amount of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction is adjusted to be about 5 to 30% by weight. It is desirable.

The synthesized precursor is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted, or substituted with other organic solvents as necessary. In addition, since the precursor is generally excellent in solvent solubility, it is advantageously used. The method of imidizing the precursor is not particularly limited, for example, a heat treatment such as heating in the solvent at a temperature in the range of 80 to 400°C over 1 to 24 hours is preferably employed.

The polyimide insulating layer may contain an inorganic filler in the polyimide layer as necessary. Specifically, for example, silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and the like can be mentioned. These can be used alone or in combination of two or more.

<Copper foil>

In the copper clad laminate of the present embodiment, the copper foil has a square mean roughness (Rq) of 0.05 µm or more and less than 0.5 µm, preferably 0.1 µm or more and 0.4 µm or less. Become me The square mean roughness (Rq) defined here is based on JIS B0601:2001. In addition, the material of the copper foil may be a copper alloy.

The copper foil used for the copper clad laminate of the present embodiment is not particularly limited as long as it satisfies the above characteristics, and a commercially available copper foil can be used. As a specific example, as a rolled copper foil, BHY-22B-T (brand name), copper GHY5-93F-T (brand name) etc. manufactured by JX Nikko Nisseki Metals Co., Ltd. can be mentioned. As an electrolytic copper foil, Furukawa Electric F1-WS (trade name) manufactured by Kogyo Co., Ltd., HLS (brand name) manufactured by Nippon Electrolytic Co., Ltd., HLS-Type2 (brand name), HLB (trade name), AMFN (brand name) manufactured by JX Nikko Nisseki Metals Corporation I can.

In a state in which a high-frequency signal is supplied to the signal wiring, there is a problem that the current flows only on the surface of the signal wiring, the effective cross-sectional area through which the current flows is reduced, the DC resistance increases, and the signal is attenuated (skin effect). By lowering the surface roughness of the surface of the copper foil in contact with the polyimide insulating layer, it is possible to suppress an increase in the resistance of the signal wiring due to this skin effect. However, when the surface roughness is lowered in order to satisfy the electrical performance requirement criterion, the adhesive strength (peel strength) between the copper foil and the polyimide insulating layer is weakened. Therefore, it is important to control the square mean roughness Rq as a parameter of the surface roughness from the viewpoint of satisfying the electrical performance requirements and securing the adhesiveness with the polyimide insulating layer. That is, from the simulation test results to be described later, the average square roughness (Rq) more accurately reflects the influence of the fine irregularities on the copper foil surface with respect to the current flowing through the copper foil surface due to the skin effect, compared to other indicators of surface roughness. It is speculated to be. Therefore, by using the average square roughness (Rq) as an index of the surface roughness of the surface in contact with the polyimide insulating layer in the copper foil, and defining this average square roughness (Rq) within the above range, adhesion with the polyimide insulating layer It is possible to simultaneously satisfy the trade-off demands of securing performance and suppressing increase in wiring resistance.

Moreover, as for the surface roughness of the surface in contact with the insulating resin layer of copper foil, it is preferable that the arithmetic average height (Ra) is 0.2 micrometers or less, and it is preferable that the 10-point average roughness (Rz) is 1.5 micrometers or less.

<Printed wiring board>

The printed wiring board of this embodiment can manufacture the printed wiring board which is one embodiment of this invention by processing the copper foil of the copper clad laminated board of this embodiment into a pattern by a conventional method to form a wiring layer.

Hereinafter, the method of manufacturing the printed wiring board of the present embodiment will be specifically described by taking the case of the cast method as an example.

First, the manufacturing method of a copper clad laminated board can include the following steps (1)-(3).

Process (1):

Step (1) is a step of obtaining a resin solution of polyamic acid which is a precursor of polyimide used in the present embodiment.

Step (2):

Step (2) is a step of forming a coating film by applying a resin solution of polyamic acid on copper foil. The copper foil can be used in a shape such as a cut sheet shape, a roll shape, or an endless belt shape. In order to obtain productivity, it is effective to make it in the form of a roll shape or an endless belt shape, and to make it a type in which continuous production is possible. Further, from the viewpoint of further expressing the effect of improving the accuracy of the wiring pattern in the printed wiring board, the copper foil is preferably a roll formed in a long shape.

The method of forming a coating film can be formed by directly applying a resin solution of polyamic acid on a copper foil and then drying it. The method of application is not particularly limited, and for example, it is possible to apply with a coater such as a comma, die, knife, or lip.

The polyimide layer may be a single layer or may be formed of a plurality of layers. When the polyimide layer is made into a plurality of layers, it can be formed by sequentially applying different precursors on the layers of precursors composed of different constituent components. When the precursor layer consists of three or more layers, the precursor having the same configuration may be used two or more times. A two-layer or single-layer having a simple layer structure is preferable because it can be obtained industrially advantageously. Further, the thickness of the precursor layer (after drying) is, for example, in the range of 3 to 100 µm, preferably in the range of 3 to 50 µm.

In the case of using a plurality of polyimide layers, it is preferable to form a layer of the precursor so that the polyimide layer in contact with the copper foil becomes a thermoplastic polyimide layer. By using a thermoplastic polyimide, the adhesiveness with copper foil can be improved. As for such a thermoplastic polyimide, it is preferable that the glass transition temperature (Tg) is 360 degreeC or less, More preferably, it is 200-320 degreeC.

In addition, after the layer of a single layer or a plurality of precursors is once imidized to form a single layer or a polyimide layer of a plurality of layers, a layer of the precursor may be further formed thereon.

Step (3):

Step (3) is a step of heat-treating a coating film to imidize it to form a polyimide insulating layer. The method of imidation is not particularly limited, for example, heat treatment such as heating for a time within the range of 1 to 60 minutes at a temperature condition within the range of 80 to 400°C is preferably employed. In order to suppress oxidation of the metal layer, heat treatment in a low oxygen atmosphere is preferable, and specifically, it is preferable to carry out in an inert gas atmosphere such as nitrogen or rare gas, a reducing gas atmosphere such as hydrogen, or in a vacuum. The polyamic acid in the coating film is imidized by heat treatment to form a polyimide.

In the manner described above, a copper-clad laminate having a polyimide layer (single layer or multiple layers) and copper foil can be produced.

Moreover, the manufacturing method of a circuit board can further include the following process (4) in addition to the process of said (1)-(3).

Step (4):

Process (4) is a process of forming a wiring layer by patterning the copper foil of a copper clad laminated board. In this step, a pattern is formed by etching the copper foil into a predetermined shape, and a printed wiring board is obtained by processing it into a wiring layer. Etching can be performed by any method using, for example, a photolithography technique.

In addition, in the above description, only the characteristic steps of the method for manufacturing a printed wiring board have been described. That is, when manufacturing a printed wiring board, processes other than the above, for example, processes such as through-hole processing in the pre-process, terminal plating in the post-process, and external appearance processing can be performed according to a conventional method. have.

As described above, by using the polyimide insulating layer and copper foil of the present embodiment, a copper clad laminate having excellent transmission characteristics can be formed. Moreover, by using the polyimide insulating layer and copper foil of this embodiment, in the circuit board represented by FPC, the transmission characteristic of an electric signal can be improved, and reliability can be improved.

Example

Hereinafter, examples are shown, and the features of the present invention will be described in more detail. However, the scope of the present invention is not limited to the examples. In addition, in the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[Measurement of Coefficient of Thermal Expansion (CTE)]

The coefficient of thermal expansion is a polyimide film having a size of 3 mm × 20 mm, using a thermomechanical analyzer (manufactured by Bruker, brand name: 4000SA) and applying a load of 5.0 g from 30°C to 250°C at a constant temperature increase rate. The temperature was raised and further maintained at that temperature for 10 minutes, and then cooled at a rate of 5°C/min to obtain an average coefficient of thermal expansion (linear thermal expansion coefficient) from 240°C to 100°C.

[Measurement of glass transition temperature (Tg)]

The glass transition temperature is a polyimide film having a size of 5 mm × 20 mm, using a viscoelasticity measuring device (DMA: manufactured by TA Instruments, brand name: RSA3), from 30° C. to 400° C. at a heating rate of 4° C./min, frequency It implemented at 1 Hz, and the temperature at which the elastic modulus change became the largest (tanδ change rate was largest) was evaluated as a glass transition temperature.

[Measurement of peel strength]

Peel strength was measured using a Tensilon tester (manufactured by Toyo Seiki Co., Ltd., brand name: strograph VE-10), and the resin layer side of a sample having a width of 1 mm (a laminate composed of a base material/resin layer) by a double-sided tape. It was fixed to an aluminum plate, and the force at the time of peeling the resin layer and the base material at a rate of 50 mm/min in the 180° direction was calculated.

[Measurement of permittivity and dielectric tangent]

The dielectric constant and the dielectric tangent were measured for the dielectric constant and the dielectric tangent of the resin sheet (resin sheet after curing) at a predetermined frequency using a cavity resonator perturbation method dielectric constant evaluation device (manufactured by Agilent, brand name; Vector Network Analyzer E8363B). . In addition, the resin sheet used for measurement is temperature; 24-26 degreeC, humidity; It left to stand for 24 hours under the conditions of 45-55%.

[Measurement of surface roughness of copper foil]

1) Measurement of mean square roughness (Rq)

Using a stylus type surface roughness meter (manufactured by Kosaka Research Institute, brand name; Surfcoder ET-3000), Force; 100 μN, Speed; 20 µm, Range; It was calculated|required by 800 micrometers measurement conditions. In addition, the calculation of the surface roughness was calculated by the method conforming to JIS-B0601: 2001.

2) Measurement of arithmetic mean height (Ra)

Using a stylus type surface roughness meter (manufactured by Kosaka Research Institute, brand name; Surfcoder ET-3000), Force; 100 μN, Speed; 20 µm, Range; It was calculated|required by 800 micrometers measurement conditions. In addition, the calculation of the surface roughness was calculated by the method conforming to JIS-B0601:1994.

3) Measurement of 10-point average illuminance (Rz)

Using a stylus type surface roughness meter (manufactured by Kosaka Research Institute, brand name; Surfcoder ET-3000), Force; 100 μN, Speed; 20 µm, Range; It was calculated|required by 800 micrometers measurement conditions. In addition, the calculation of the surface roughness was calculated by the method conforming to JIS-B0601:1994.

[Evaluation of transmission characteristics]

In the evaluation of the transmission characteristics, the transmission characteristics of the circuit-processed side (transmission line side) were evaluated using an evaluation sample in which a copper clad laminate was circuit-processed and a microstrip line having a characteristic impedance of 50 Ω was circuit-processed. The vector network analyzer calibrated by the SOLT method (SHORT-OPEN-LOOD-Thru) was used to measure the S parameter in a predetermined frequency domain, thereby evaluating in S21 (insertion loss).

The abbreviations used in Examples and Comparative Examples represent the following compounds.

(A) Polyimide raw material

DDA: Dimer acid type diamine (Kuroda Japan Co., Ltd. make, brand name: PRIAMINE1074, carbon number: 36, amine value: 205 mgKOH/g, content of dimer component: 95% by weight or more)

m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl

BAPP: 2,2-bis(4-aminophenoxyphenyl)propane

TPE-R: 1,3-bis(4-aminophenoxy)benzene

Wondamine: 4,4'-diaminodicyclohexylmethane

BAFL: 9,9-bis(4-aminophenyl)fluorene

TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl

PMDA: pyromellitic dianhydride

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

DMAc: N,N-dimethylacetamide

(B) copper foil

Copper foil (1): Electrolytic copper foil, thickness; 12 µm, surface roughness Rq on the resin lamination side; 0.14 µm, Rz; 0.64 µm, Ra; 0.10 μm)

Copper foil (2): Electrolytic copper foil, thickness; 12 µm, surface roughness Rq on the resin lamination side; 0.19 µm, Rz; 1.06 µm, Ra; 0.16 μm)

Copper foil (3): Electrolytic copper foil, thickness; 12 µm, surface roughness Rq on the resin lamination side; 0.27 µm, Rz; 1.36 µm, Ra; 0.21 μm)

Copper foil (4): Electrolytic copper foil, thickness; 12 µm, surface roughness Rq on the resin lamination side; 0.35 µm, Rz; 1.51 µm, Ra; 0.28 μm)

Copper foil (5): Electrolytic copper foil, 12 µm in thickness, and surface roughness Rq on the resin lamination side; 0.5 µm, Rz; 1.65 µm, Ra; 0.36 μm)

Copper foil (6): Rolled copper foil, 12 µm in thickness, and surface roughness Rq on the resin lamination side; 0.24 µm, Rz; 1.30 µm, Ra; 0.18 μm)

Synthesis Example 1

Under a nitrogen stream, 2.196 g of DDA (0.0041 mol), 16.367 g of m-TB (0.0771 mol), and 212.5 g of DMAc were added to a 300 ml separable flask, followed by stirring at room temperature to dissolve. Next, after adding 4.776 g of BPDA (0.0162 mol) and 14.161 g of PMDA (0.0649 mol), stirring was continued at room temperature for 3 hours to carry out a polymerization reaction to obtain a polyamic acid solution a. The solution viscosity of the polyamic acid solution a was 26,000 cps.

Synthesis Examples 2 to 13

Polyamic acid solutions b to m were prepared in the same manner as in Synthesis Example 1 except that the composition of the raw materials shown in Tables 1 and 2 was used.

[Production Example 1]

On one side of an electrolytic copper foil having a thickness of 18 μm (surface roughness (Rz); 2.1 μm), the polyamic acid solution a prepared in Synthesis Example 1 was uniformly applied so that the thickness after curing became about 25 μm, and then heated at 120°C. Dry to remove the solvent. Further, heat treatment was performed in stages from 120°C to 360°C to complete the imidation. About the obtained metal-clad laminate, the copper foil was etched away using an aqueous ferric chloride solution, and the polyimide film 1 was obtained. In addition, the polyimide constituting the polyimide film 1 was non-thermoplastic.

The coefficient of thermal expansion, glass transition temperature, dielectric constant, and dielectric tangent of the polyimide film 1 were determined. Table 3 shows the results of each measurement.

[Production Examples 2 to 6]

Except having used the polyamic acid solution shown in Table 3, it carried out similarly to Production Example 1, and obtained the polyimide films 2-6 of Production Examples 2-6. The coefficient of thermal expansion (CTE), glass transition temperature, dielectric constant, and dielectric tangent of the obtained polyimide films 2 to 6 were determined. Table 3 shows the results of each measurement.

The results of Production Examples 1-6 are put together and shown in Table 3.

[Production Example 7]

On one side of an electrolytic copper foil having a thickness of 12 µm (surface roughness (Rz): 1.39 µm), a polyamic acid solution h is uniformly applied so that the thickness after curing becomes about 2 to 3 µm, and then the step is from 85°C to 110°C. The solvent was removed by drying by a gentle heat treatment. Next, the polyamic acid solution b was uniformly applied thereon so that the thickness after curing became about 42 to 46 µm, and the solvent was removed by heating in steps from 85°C to 110°C. Further, the polyamic acid solution h was uniformly applied thereon so that the thickness after curing became about 2 to 3 µm, and then the solvent was removed by stepwise heat treatment from 85°C to 110°C. After thus forming a three-layer polyamic acid layer, a stepwise heat treatment was performed from 120°C to 320°C to complete imidation, and a metal-clad laminate 7 was obtained. With respect to the obtained metal-clad laminate 7, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film 7 having a thickness of about 50 µm. _{The dielectric constant (ε 1} ) and dielectric tangent ( _{Tanδ 1} ) in 3 GHz of the obtained polyimide film 7 are 3.06 and 0.0029 (E ₁ = 0.0051), respectively, and the dielectric constant and dielectric tangent in 10 GHz are 2.86, respectively, It was 0.0036.

[Example 1]

After the polyamic acid solution h was uniformly applied to the copper foil 2 so that the thickness after curing became about 2 to 3 µm, it was dried by a stepwise heat treatment to 85°C to 110°C to remove the solvent. Next, the polyamic acid solution b was uniformly applied thereon so that the thickness after curing became about 42 to 46 µm, and the solvent was removed by heating in steps from 85°C to 110°C. Further, the polyamic acid solution h was uniformly applied thereon so that the thickness after curing became about 2 to 3 µm, and then the solvent was removed by stepwise heat treatment from 85°C to 110°C. After thus forming a three-layer polyamic acid layer, a stepwise heat treatment was performed from 120°C to 320°C to complete the imidation to obtain a copper clad laminate 1'. Copper foil 1 was superimposed on the polyimide insulating layer side of the obtained copper-clad laminate 1', and thermocompression bonding was performed for 15 minutes on the condition of temperature 380 degreeC and pressure 6.7 MPa, and the copper clad laminated plate 1 was obtained. The peel strength of the copper foil 1 on the thermocompression bonding side and the polyimide insulating layer in the obtained copper-clad laminate 1 was 0.96 kN/m. Circuit processing was performed with the copper foil 1 side as a ground surface and the copper foil 2 side as a signal surface, and transmission characteristics were evaluated. This result is shown in FIG.

[Reference Example 1]

A laminated plate obtained by thermocompressing copper foil 4 on both surfaces of a commercially available liquid crystal polymer film 1 (thickness: 50 µm) was obtained. Circuit processing was performed using copper foils on both sides of this laminated plate as a ground surface and a signal surface, and transmission characteristics were evaluated. This result is shown in FIG.

[Reference Example 2]

A laminated plate obtained by thermocompressing copper foil 5 on both surfaces of a commercially available liquid crystal polymer film 2 (thickness: 50 µm) was obtained. Circuit processing was performed using copper foils on both sides of this laminated plate as a ground surface and a signal surface, and transmission characteristics were evaluated. This result is shown in FIG.

[Reference Example 3]

A laminated plate obtained by thermocompressing copper foil 5 on both surfaces of a 50 µm-thick commercially available polyimide film (dielectric constant in 3 GHz: >3.1, dielectric tangent in 3 GHz; >0.005). Circuit processing was performed using copper foils on both sides of this laminated plate as a ground surface and a signal surface, and transmission characteristics were evaluated. This result is shown in FIG.

The results of Example 1 and Reference Examples 1 to 3 are shown in Fig. 1. From Fig. 1, it is confirmed that Example 1 exhibits equal or higher transmission characteristics in a frequency range of 1 to 20 GHz in comparison with Reference Example 1.

[Example 2]

The polyamic acid solution h was uniformly applied to the copper foil 3 so that the thickness after curing became about 2 to 3 µm, and then dried by a stepwise heat treatment to 85°C to 110°C to remove the solvent. Next, the polyamic acid solution b was uniformly applied thereon so that the thickness after curing became about 42 to 46 µm, and the solvent was removed by stepwise heating treatment to 85°C to 110°C. Further, the polyamic acid solution h was uniformly applied thereon so that the thickness after curing became about 2 to 3 µm, and then the solvent was removed by stepwise heat treatment from 85°C to 110°C. After thus forming a three-layer polyamic acid layer, heat treatment was performed in stages from 120°C to 320°C to complete the imidation to obtain a copper-clad laminate 2'. Copper foil 1 was superimposed on the polyimide insulating layer side of the obtained copper-clad laminate 2', and thermocompression bonding was performed for 15 minutes on the condition of temperature 380 degreeC and pressure 6.7 MPa, and the copper-clad laminate 2 was obtained. The peel strength of the copper foil 1 on the thermocompression bonding side and the polyimide insulating layer in the obtained copper-clad laminate 2 was 0.96 kN/m. Circuit processing was performed with the copper foil 3 side as a ground surface and the copper foil 1 side as a signal surface, and transmission characteristics were evaluated. This result is shown in FIG. 2.

[Example 3]

In the same manner as in Example 2, a copper-clad laminate 3 was obtained. Circuit processing was performed with the copper foil 1 side as the ground surface and the copper foil 3 side as the signal surface, and transmission characteristics were evaluated. This result is shown in FIG. 2.

[Simulation test]

Next, the result of the simulation test confirming the effect of the present invention will be described. Fig. 2 shows the results when the dielectric constant and the dielectric tangent at 3 GHz of the polyimide insulating layer were fixed to 3.0 and 0.003, respectively, and Rq was changed from 0 to 1.0. Further, Fig. 3 shows the results when the dielectric constant and dielectric tangent of the polyimide insulating layer at 3 GHz were fixed to 3.4 and 0.006, respectively, and Rq was changed to 0 to 1.0. In addition, in the simulation test, Rq of the ground plane and the signal plane are set equally.

Simulations (1) and (7): Rq = 0 µm

Simulations (2) and (8): Rq = 0.1 µm

Simulations (3) and (9): Rq = 0.2 µm

Simulations (4) and (10): Rq = 0.3 µm

Simulations (5) and (11): Rq = 0.5 µm

Simulations (6) and (12): Rq = 1.0 µm

The results of Examples 2 and 3 and the simulations (1) to (6) are shown in Fig. 2, and the results of the simulations (7) to (12) are shown in Fig. 3. From Fig. 2, it is confirmed that the transmission loss is large in the simulations (5) and (6) in which Rq is 0.5 µm or more in Examples 2 and 3 and simulations (1) to (4) in which Rq is less than 0.5 µm. Further, from Fig. 3, it is confirmed that the smaller the value of Rq is, the better the transmission characteristic is in an almost proportional relationship, but from Fig. 2, a slight gap between the simulations (4) and (5) is confirmed. Therefore, it is considered that there is a synergistic effect of the dielectric properties of the polyimide insulating layer and the surface roughness (Rq) of the copper foil.

As mentioned above, although the embodiment of the present invention has been described in detail for the purpose of illustration, the present invention is not limited to the above embodiment, and various modifications are possible.

Claims (8)

A copper clad laminate comprising a polyimide insulating layer and a copper foil on at least one surface of the polyimide insulating layer,
The polyimide insulating layer has the following configurations Ia and Ib:
Ia) The coefficient of thermal expansion is in the range of 0 ppm/K or more and 30 ppm/K or less;
Ib) the following equation (i),
E ₁ = √ε ₁ × Tanδ ₁ … (i)
[Here, ε ₁ represents the dielectric constant at 3 GHz by the cavity resonator perturbation method, and Tanδ ₁ represents the dielectric tangent at 3 GHz by the cavity resonator perturbation method.]
_{The E 1} value, which is an index indicating the dielectric property, calculated on the basis of is less than 0.009, the dielectric constant is 3.1 or less, and the dielectric tangent is less than 0.005;
And, in addition, the copper foil, the following configuration c:
c) The average square roughness (Rq) of the surface in contact with the polyimide insulating layer is in the range of 0.1 µm or more and 0.4 µm or less;
At the same time,
The copper clad laminated board in which at least one copper foil among the copper foils has a 10-point average roughness (Rz) of 1.06 µm or more on a surface in contact with the polyimide insulating layer. The method of claim 1,
A copper clad laminate having an arithmetic mean height (Ra) of a surface of the copper foil in contact with the polyimide insulating layer of 0.2 µm or less. The method of claim 1,
A copper-clad laminate having a 10-point average roughness (Rz) of 1.5 µm or less on a surface of the copper foil in contact with the polyimide insulating layer. The method of claim 1,
The copper-clad laminate, wherein the polyimide insulating layer has a dielectric constant at 10 GHz of 3.0 or less and a dielectric tangent of 0.005 or less. A printed wiring board obtained by processing the copper foil of the copper clad laminate according to any one of claims 1 to 4 into a wiring circuit. The method of claim 5,
The printed wiring board is used in a frequency range within a range of 1 GHz to 40 GHz. The method of claim 5,
The printed wiring board is used in a frequency range within a range of 1 GHz to 20 GHz. delete

Images