JPWO2009063742A1 - Metal laminate - Google Patents

Abstract

The present invention provides inexpensively a flexible metal laminate and a flexible printed board that are excellent in flexibility, folding resistance, heat resistance reliability, moisture absorption characteristics, and dimensional accuracy. A flexible metal laminate in which a metal foil is laminated on at least one surface of a two-layer heat-resistant resin film made of polyamideimide resin, and one layer of the heat-resistant resin film has a) a naphthalene group A monomer component having a specific mol% or more, b) a molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio, and c) an imidization ratio of imide bond is 50% or more, A flexible metal laminate comprising: a resin layer having an elastic modulus of 4800 MPa or less; and the other layer formed from a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less.

Description

  The present invention relates to a flexible metal laminate in which a metal foil is laminated on at least one surface of a heat-resistant resin film, and a flexible printed circuit board. More specifically, the present invention is excellent in flexibility, folding resistance, insulation, and solder processing. The present invention relates to a flexible metal laminate and a flexible printed circuit board which are excellent in heat peel reliability such as later peel strength, solder heat resistance after humidification, and dimensional accuracy such as humidity dimensional change rate.

  In the present specification and claims, the term “flexible metal-clad laminate” refers to a laminate formed from a metal foil and a resin layer, and is useful for the production of, for example, a flexible printed circuit board. It is. In addition, the “flexible printed circuit board” can be manufactured by a conventionally known method such as a subtractive method using a flexible metal-clad laminate, and a conductor circuit may be partially or fully covered by a cover as necessary. So-called flexible circuit board (FPC), flat cable, circuit board for tape automated bonding (TAB), or circuit board for mounting TCP (tape carrier package) coated with film or screen printing ink ( Chip-on-flexible board etc.).

  A conventional flexible metal-clad laminate for a flexible printed circuit board is obtained by bonding a polyimide film and a metal foil with an adhesive such as a rubber-modified epoxy resin or acrylic resin. The flexible printed circuit board formed from the flexible metal-clad laminate bonded with this adhesive has significantly lower heat resistance than the polyimide film, so heat resistance reliability, thermal dimensional stability, insulation reliability, etc. There was a problem of being inferior.

In order to solve these problems, a technique for forming a metal-clad laminate (two-layer CCL) having a two-layer structure without an adhesive layer by directly applying a polyimide resin solution to a metal foil has been proposed. (For example, refer to Patent Documents 1 and 2). However, these two-layer CCL
-Since the polyimide resin to be applied is insoluble in an organic solvent, it is necessary to imidize by applying a high temperature heat treatment on the metal foil after applying the precursor polyamic acid solution. Therefore, it is inferior to workability.
-Since the elastic modulus of the resin film layer formed on the metal foil is high, the flexible printed circuit board is inferior in the bending resistance and folding resistance.
There are disadvantages such as.

  In order to improve the processability, bending resistance, and folding resistance as described above, in Patent Document 3, a resin composition that is soluble in an organic solvent and has a low film modulus is directly applied to a metal foil. A technique for forming a two-layer CCL by drying is proposed. However, although the resin composition used here is excellent in workability and bending resistance, it is inferior in heat resistance reliability such as dimensional accuracy such as humidity dimensional change rate, peel strength after soldering, etc. For example, there is a drawback that it is not suitable for a so-called COF substrate (chip-on-flexible substrate) application in which a semiconductor element is mounted (TCP mounting) or a high-density circuit board application in which a fine pitch is required. It was.

JP-A-57-50670 JP-A-57-66690 JP 2001-105530 A

  The object of the present invention was made to solve the above-mentioned problems, and in particular, a flexible metal laminate for a flexible printed circuit board, which can be used for high-density circuit board applications where fine pitch is required, And it is going to manufacture a flexible printed circuit board at low cost. That is, the object of the present invention is excellent in flexibility and folding resistance, low humidity dimensional change rate, high Tg, heat resistance such as peel strength after soldering and solder heat resistance after humidification. The present invention also relates to a flexible metal laminate and a flexible printed circuit board made of an excellent substrate material.

  As a result of intensive studies on a resin composition that is soluble in a solvent and excellent in heat resistance, and a layer structure as a flexible printed board including these materials, a processing method, etc. It has been achieved.

That is, this invention is the following flexible metal-clad laminates and flexible printed boards.
(1)
A flexible metal laminate in which a metal foil is laminated on at least one surface of a heat resistant resin film, the heat resistant resin film having a two-layer structure composed of a polyamide-imide resin soluble in an organic solvent, ,
a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a naphthalene group is 80 mol%.
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) formed from a resin layer having an imidization rate of imide bond of 50% or more and an elastic modulus of 4800 Mpa or less, and the other layer is a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less. A flexible metal laminate which is formed.
(2)
When the heat-resistant resin layer on the side in contact with the metal foil is a) the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the naphthalene group is Has a monomer component of 80 mol%
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) Low humidity expansibility in which the imidization rate of the imide bond is 50% or more and is formed from a resin layer having an elastic modulus of 4800 Mpa or less, and the resin layer on the side not in contact with the metal foil has a humidity expansion coefficient of 20 ppm or less The flexible metal laminate according to (1), wherein the metal foil is laminated only on one side, which is a resin layer.
(3)
A flexible metal laminate according to (1) or (2) in which a metal foil is formed on one side, wherein a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less,
a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a biphenylene group is 100 mol% or more, and b) The molar ratio of imide bond to amide bond is 99/1 to 65/35 molar ratio,
c) A flexible metal laminate having an imidization ratio of imide bonds of 50% or more.
(4)
a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a naphthalene group is 80 mol%.
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) Ratio of the thickness (T1) of the resin layer having an imidization rate of imide bond of 50% or more and an elastic modulus of 4800 Mpa or less to the thickness (T2) of a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less (T1) ) / (T2) is 0.05-5, The flexible metal laminated body in any one of (1)-(3) characterized by the above-mentioned.
(5)
The double-sided flexible metal laminated body obtained by bonding together the flexible metal laminated body in any one of (1)-(4) so that metal foil may be formed in both surfaces.
(6)
A flexible printed circuit board obtained from the flexible metal-clad laminate according to any one of (1) to (5).
Consists of.

  The flexible metal laminate of the present invention is composed of a plurality of resin compositions having excellent flexibility, folding resistance and adhesion, low humidity dimensional change rate, and high Tg. Excellent fold characteristics, heat-resistant reliability such as peel strength after soldering and soldering heat resistance after humidification, and dimensional accuracy. Furthermore, since the resin composition to be used is soluble in an organic solvent, it can be produced at low cost without the need for heat treatment at high temperatures. Therefore, since a flexible substrate that can be used in high-density mounting substrate applications such as a COF substrate can be manufactured at low cost, there are significant industrial advantages.

The resin film layer of the flexible metal laminate of the present invention is composed of two layers, and a metal foil is laminated on at least one surface of the resin film layer. The resin used for the two resin film layers is a polyamide-imide resin soluble in an organic solvent. Of the two resin film layers, one layer is formed from a resin film layer having an elastic modulus of 4800 Mpa or less, preferably 4500 Mpa or less, more preferably 4300 Mpa or less (hereinafter referred to as a low modulus resin layer). And the other layer has a humidity expansion coefficient of 20 ppm or less, preferably 15 ppm or less, more preferably 13 ppm or less, and is formed from a resin film layer (hereinafter referred to as a low humidity expansion resin layer). Yes. When the elastic modulus of the low elastic modulus resin layer exceeds 4800 Mpa, the flexibility and folding resistance of the flexible metal laminate are deteriorated, and the heat resistance reliability such as the adhesive strength, particularly the peel strength after soldering, is deteriorated. In particular, when the elastic modulus of the low elastic modulus resin layer is high, the solder heat resistance is greatly lowered after the humidification treatment, and particularly when the humidity expansion coefficient of the low humidity expandable resin layer is high. Although a clear reason is not known, it is presumed that in the soldering process during the humidification process, the low elastic modulus resin layer plays a cushioning role against moisture release and thermal expansion occurring during the soldering process. On the other hand, when the humidity expansion coefficient exceeds 20 ppm, the humidity dimensional change rate is increased, the dimensional accuracy is deteriorated, and the heat reliability such as solder heat resistance after the humidification process is also deteriorated. The low elastic modulus of the low elastic modulus resin layer is preferably as low as possible, but is preferably 1000 MPa or more. If it is less than 1000 MPa, handling properties and transportability may deteriorate. Further, although it cannot be generally stated depending on the required performance, it may be 2000 MPa or more, and further 2500 MPa or more. The humidity expansion coefficient is preferably as low as possible, but is preferably 1 ppm or more. Although it cannot be generally stated depending on the required performance, it may be 5 ppm or more, and further 7 ppm or more. Since the humidity expansion coefficient of the metal foil is theoretically 0 ppm, the low humidity expansion coefficient of the low-humidity expandable resin layer is preferably as low as possible.
In order to achieve the object of the present invention, of the two resin film layers, the heat-resistant resin layer on the side in contact with the metal foil is a low elastic modulus resin layer. This is preferable because a flexible metal laminate excellent in reliability, flexibility and folding resistance can be obtained. Although the reason is not clearly understood, it is expected that by placing a low elastic modulus resin layer on the side in contact with the metal foil, the layer will exhibit cushioning properties, so that it will be excellent in performance such as flexibility and folding resistance. The
In addition, the low elastic modulus resin layer generally has a relatively high hygroscopic expansion coefficient, but the heat resistance resin layer on the side in contact with the metal foil is the same as the heat resistance on the side not in contact with the low elastic modulus resin layer and the metal foil. By making the resin layer a low humidity expandable resin layer, the low elastic modulus resin layer is sandwiched between the metal foil layer and the low humidity expandable resin layer. Due to the structure of the metal laminate, the low elastic modulus resin layer is Since it is less susceptible to the influence of humidity, it is expected that it will be excellent in heat resistance reliability such as solder heat resistance after the humidification process, but no clear reason is known.

  The heat-resistant resin film used in the present invention is classified into the category of so-called engineering plastics that are excellent in heat resistance, such as polyimide, polyamideimide, polyetherimide, polyesterimide, polyparabanic acid, polyarylate, and aramid. Any resin can be used. From the viewpoint of heat resistance, dimensional accuracy, etc., preferably polyimide and polyamideimide, and from the viewpoint of workability, more preferred are polyimide and polyamideimide soluble in organic solvents, and more preferred solubility in organic solvents. This is a polyamide imide.

[Low elastic modulus resin layer]
In the low elastic modulus resin layer, one necessary condition for satisfying the implementation requirements of the present invention is that the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total amount of the acid component and the amine component is 200 mol%. In this case, the monomer component having a naphthalene group is a polyamideimide resin having 80 mol% or more. The monomer component having a naphthalene group is preferably 90 mol% or more, more preferably 100 mol% or more. If the naphthalene group is less than 80 mol%, the moisture absorption characteristics deteriorate, the dimensional accuracy such as the rate of change in humidity does not satisfy the requirements of the present invention, and the heat resistance also decreases. Heat resistance reliability such as solder heat resistance after the humidification process also decreases. Moreover, it is preferable that the monomer component which has a naphthalene group is 170 mol% or less, More preferably, it is 160 mol% or less, More preferably, it is 150 mol% or less. When it exceeds 170 mol%, the elastic modulus increases and the solubility tends to decrease.
The molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio. Preferably the molar ratio of imide bond to amide bond is 99/1 to 75/25, more preferably 90/10 to 80/20. When the molar ratio of the imide bond to the amide bond is less than 60/40, the heat resistance and the heat resistance reliability are poor, and particularly the peel strength after soldering is lowered. On the other hand, if it exceeds 99/1, the elastic modulus increases, and the folding resistance and bending characteristics deteriorate. Furthermore, since the solubility is poor, the workability of the flexible metal laminate is deteriorated.
When showing one preferable embodiment of the low elastic modulus resin layer having an elastic modulus of 4800 MPa or less used for achieving the object of the present invention, it is preferable that the unit represented by the general formula (1) is an essential component. Furthermore, there is provided a polyamide-imide resin containing, as a repeating unit, at least one unit selected from the group represented by the general formula (2), the general formula (3), and the general formula (4) in the molecular chain. preferable. Here, in the general formula (2), X is particularly SO2 or direct connection (biphenyl) from the viewpoint of low elastic modulus (flexibility and folding resistance), Tg, heat resistance reliability, and adhesion to copper foil. Alternatively, n = 0 is preferable, more preferably direct connection (biphenyl), or n = 0. In general formula (3), Y is preferably a benzophenone type (CO) or a direct connection type (biphenyl) from the viewpoint of low elastic modulus, Tg, heat resistance reliability, and adhesion to copper foil, as described above. The units represented by the following general formula (2) and general formula (3) may be one type or two or more types, respectively. A substituent may be bonded to the naphthalene skeleton or the benzene skeleton. The lower the elastic modulus, the better. For that purpose, the ratio of the general formula (1) to the {general formula (2) + the general formula (3) + the general formula (4)} is increased, and the imide bond to the amide bond is increased. It is desirable to take measures such as reducing the ratio.

  The content ratio of the general formula (1), the general formula (2), the general formula (3), and the general formula (4) is a molar ratio of {general formula (1)} / {general formula (2) + general formula ( 3) + General formula (4)} = 1/99 to 40/60 (molar ratio), and the molar ratio of the imide bond to the amide bond is 99/1 to 60/40 molar ratio. It is. Furthermore, preferably {general formula (1)} / {general formula (2) + general formula (3) + general formula (4)} = 10/90 to 30/70, and the molar ratio of imide bond to amide bond is 99. / 1 to 75/25, most preferably general formula (1)} / {general formula (2) + general formula (3) + general formula (4)} = 10/90 to 20/80 and imide bond and amide bond The molar ratio is 90/10 to 80/20. If the content ratio of {general formula (1)} / {general formula (2) + general formula (3) + general formula (4)} exceeds 40/60 or is lower than 1/99, heat resistance It tends to be difficult to achieve both compatibility (Tg), low elastic modulus, and adhesion with copper foil. In particular, when the content ratio of {general formula (1)} / {general formula (2) + general formula (3) + general formula (4)} exceeds 40/60, the heat resistance deteriorates. When it is lower, the solubility in a solvent becomes poor, and the elastic modulus of the resin film increases, so that the bending resistance and folding resistance tend to decrease. On the other hand, when the molar ratio of the imide bond to the amide bond is less than 60/40, the heat resistance and heat resistance reliability are poor, and particularly the peel strength after soldering is lowered. When the molar ratio of the imide bond to the amide bond exceeds 99/1, the elastic modulus increases, and the folding resistance and bending characteristics deteriorate. Furthermore, since the solubility is poor, the workability of the flexible metal laminate is deteriorated.

  Further, from the viewpoint of heat resistance and moisture absorption characteristics, a preferred embodiment is a molar ratio of the content ratio of the amide-forming component of the general formula (2) and the imide-forming component of the general formula (3) and / or the general formula (4). It is preferable to adjust to {General Formula (2)} / {General Formula (3) + General Formula (4)} = 5/95 to 95/5. If the content of {general formula (2)} in general formula (2) and general formula (3) and / or general formula (4) is less than 5 mol%, the moisture absorption properties tend to be poor. On the other hand, if it exceeds 95 mol%, the heat resistance tends to deteriorate. As an example of one preferred embodiment, general formula (1) is a repeating unit from trimellitic anhydride and 1,5-naphthalene diisocyanate, and general formula (2) is a repeating unit from terephthalic acid and 1,5-naphthalene diisocyanate. The unit, the general formula (3) is a repeating unit from biphenyltetracarboxylic dianhydride and / or benzophenonetetracarboxylic dianhydride and 1,5-naphthalene diisocyanate, and the content ratio thereof is the general formula (1) / {General Formula (2) + General Formula (3) + General Formula (4)} = 1/99 to 40/60 molar ratio, and General Formula (2) / General Formula (3) = 10/90 to 90 / 10 molar ratio is preferred

  In the above, when the content of general formula (1) in general formula (1), general formula (2), general formula (3), and general formula (4) exceeds 40 mol%, Hygroscopic properties are lowered, and if it is less than 1 mol%, the solvent solubility of the resin tends to be poor and the film modulus tends to be high. In addition, when the content of the general formula (2) in the general formula (2), the general formula (3), and the general formula (4) is less than 10 mol%, the moisture absorption characteristics may be reduced, and 90 mol If it exceeds 100%, the solvent solubility of the resin tends to deteriorate.

  In the above embodiment, common preferred embodiments will be described. In the general formula (2), it is particularly preferable that the bond ratio of the ratio in which the amide bond is in the para position and the ratio in the meta position satisfies para position / meta position = 5/95 to 100/0 mol%. More preferably, the bond ratio of the ratio in which the amide bond is in the para position and the ratio in the meta position satisfies the para position / meta position = 20/80 to 100/0 mol%, most preferably the para position. / Meta position = when satisfying 50/50 to 100/0 mol%. When the para position is 5 mol% or less, the effect of improving the heat resistance tends to decrease.

  Further, these polyamide-imide resins are preferably non-halogen-based resins that do not contain halogens such as fluorine, chlorine, bromine, and iodine from the viewpoint of environmental considerations.

The imide bond of the polyamide-imide resin needs to have an imidization ratio of 50% or more. Preferably it is 90% or more, More preferably, it is 95% or more. The higher the imidization rate, the better. The upper limit is 100%. If the imidization rate of the imide bond is less than 50%, the adhesion between the low elastic modulus resin film and the low hygroscopic resin film tends to be low, and the peeling between the resin layers tends to occur. Will fall. As a result, reliability such as folding resistance, bendability, heat resistance reliability (peel strength), etc. becomes poor.
The reason for this is that if the second layer is laminated before the imidization reaction of the first layer is completed, the imidization reaction accompanying the heating proceeds in the subsequent heating step, and it occurs accordingly. It is presumed that condensed water adversely affects properties such as folding resistance at the resin layer or at the interface between the resin and the metal foil. Therefore, the production of the resin composition used in the present application is preferably carried out by a method such as an isocyanate method described later so that the imidization rate of the obtained resin varnish is completed after polymerization. Since it is calculated | required to melt | dissolve in a solvent, it is preferable that a composition is soluble in an organic solvent. In addition, even in the production by the isocyanate method, the imidization reaction after polymerization may not necessarily be completed after the polymerization due to the influence of the purity of the monomer or the solvent type, and therefore it is necessary to pay attention to the production conditions. In order to increase the imidization ratio to 50% or more, in the case of the amine method, a precursor is synthesized by a usual method, and after film formation, the temperature is gradually raised to Tg or more, and the temperature is increased to around Tg (plus or minus 10 ° C.). It is preferable to heat for about an hour and perform sufficient imidization treatment. In the isocyanate method, it is preferable to reduce the moisture content to 50 mol% or less of the number of moles of the monomer or to increase the purity of the monomer during the polymerization. For example, it is desirable that the monomer purity is high, such as using a trimellitic anhydride having a high cyclization rate and a small amount of the diamine component which is an impurity in the diisocyanate component.
In addition, the measurement of imidation rate can be calculated | required by the method as described in the below-mentioned Example.

  Moreover, these polyamideimide resins must be soluble in an organic solvent from the viewpoint of processability when a flexible metal-clad laminate or a laminated film with an adhesive layer described later is used. The organic solvent mentioned here is, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane. Or at least one selected from the group consisting of dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and cyclopentanone, or a part thereof from toluene, xylene, diglyme, triglyme, tetrahydrofuran, methyl ethyl ketone and methyl isobutyl ketone. It shall be replaced with at least one selected from the group consisting of In the present invention, being soluble in an organic solvent means that any one of the above-mentioned single solvents or a mixed organic solvent containing 20% or more of at least one of them is 10% by weight or more. It means to dissolve. Preferably, it is 15% by weight or more, more preferably 20% by weight or more. In addition, when the resin is in a solid state, whether or not it has been dissolved is determined by adding a specified weight of resin powder passing through 80 mesh into a 200 ml beaker and gently stirring at 25 ° C. for 24 hours. Is allowed to stand at 25 ° C. for 24 hours, and it can be determined that a solution that was not gelled, non-uniformized, clouded, or precipitated is dissolved.

In order to be soluble in a solvent, (1) the above-mentioned preferred resin composition is made (2) the ratio of imide group / amide group is lowered (3) polycarboxylic acid component and polyamine component having an alicyclic group described later (4) A polycarboxylic acid component having an aliphatic group, which will be described later, and a copolymerized as a polyamine component (5) A flexible group is introduced into the aromatic ring.
(6) A bulky compound is introduced into the polymer chain.
(7) The polymer is modified with an epoxy compound described later.
Etc. can be achieved.

  As described above, with the naphthalene skeleton as the main skeleton and the bond ratio set to a specific ratio, the rigidity / flexibility of the polymer chain itself, the intermolecular force between the polymer chains, the plane orientation, etc. are well balanced. In addition, the objects of the present invention such as solvent solubility, low elastic modulus, and heat resistance can be achieved.

・・・一般式（１）

... General formula (1)

・・・一般式（２）

... General formula (2)

(X represents an oxygen atom, CO, SO2, or direct connection, and n represents 0 or 1)

・・・一般式（３）

... General formula (3)

(Y represents an oxygen atom, CO, or OOC-R-COO, n represents 0 or 1, and R represents a divalent organic group.)

・・・一般式（４）

... General formula (4)

[Low humidity expandable resin layer]
The low-humidity expandable resin layer needs to be formed from a polyamideimide resin having a humidity expansion coefficient of 20 ppm or less. Preferably, it is formed from a polyamide-imide resin film layer (low humidity expandable resin) having a humidity expansion coefficient of 15 ppm or less, more preferably 13 ppm or less.
In the low-humidity expandable resin layer, when the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total amount of the acid component and the amine component is 200 mol%, the monomer having a biphenylene group is 100 mol. % Or more, more preferably 120 mol% or more, and most preferably 140 mol% or more. When the biphenylene group is less than 100 mol%, the moisture absorption characteristics are deteriorated, and the dimensional accuracy such as the moisture absorption dimensional change rate and the heat reliability such as the solder heat resistance after the humidification treatment tend to be deteriorated. The monomer having a biphenylene group is preferably 180 mol% or less, more preferably 170 mol% or less, and most preferably 160 mol% or less. If it exceeds 180 mol%, the solubility tends to decrease.
Here, the molar ratio of imide bond to amide bond is preferably 99/1 to 65/35 molar ratio, and more preferably 90/10 to 70/30 molar ratio.
If the molar ratio of imide bond to amide bond is less than 65/35, the dimensional accuracy such as peel strength after soldering and moisture absorption dimensional change rate deteriorates, peel strength after humidifying, solder heat resistance after humidifying, etc. The heat resistance reliability and moisture resistance of the steel tend to deteriorate. If the molar ratio of the imide bond to the amide bond exceeds 99/1, the solubility tends to be poor, and further, the elastic modulus is increased, and the folding resistance and bending characteristics tend to be deteriorated.
One preferred embodiment of the low-humidity expansive resin layer having a humidity expansion coefficient of 20 ppm or less used for achieving the object of the present invention is given by general formula (5), general formula (6), and general formula (7). ) As an essential component, and the copolymerization ratio thereof is {general formula (5)} / {general formula (6)} / {general formula (7)} = 30 to 75/10 to 50/10 to 50 It is a polyamideimide resin having a (molar ratio). More preferably, {general formula (5)} / {general formula (6)} / {general formula (7)} = 35 to 65/10 to 30/20 to 50 (molar ratio), most preferably General formula (5)} / {General formula (6)} / {General formula (7)} = 40 to 50/10 to 25/25 to 40 (molar ratio). Here, the molar ratio of imide bond to amide bond is preferably 99/1 to 65/35 molar ratio, and more preferably 90/10 to 70/30 molar ratio. When the general formula (5) is more than 75 mol% and the general formula (6) and the general formula (7) are lower than the lower limit, respectively, the dimensional accuracy such as the moisture absorption dimensional change rate is increased, and the peel after the humidification treatment Strength, heat resistance reliability such as solder heat resistance after humidification, and moisture resistance tend to deteriorate. Further, when the general formula (5) is less than 30 mol% and the general formula (6) and the general formula (7) are more than the upper limit, respectively, the solubility is poor, and the elastic modulus of the resin film is increased, It tends to be difficult to ensure flexibility and folding resistance, which is one of the objects of the present invention. In addition, when the molar ratio of imide bond to amide bond is less than 65/35, the dimensional accuracy such as peel strength after soldering and moisture absorption dimensional change rate is deteriorated, peel strength after humidifying, and solder heat resistance after humidifying. There is a tendency that the heat resistance reliability such as the property and the moisture resistance are also deteriorated. If the molar ratio of the imide bond to the amide bond exceeds 99/1, the solubility tends to be poor, and further, the elastic modulus is increased, and the folding resistance and bending characteristics tend to be deteriorated.
In particular, among the acid component and the amine component, the most preferable combination is when a monomer having a bisubstituted biphenylene group such as dimethyldiaminobiphenyl is used, and the acid component is trimellitic anhydride, 3, 3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and the amine component is 3,3′-dimethyl- This is the case for 4,4′-diaminobiphenyl.
This layer is formed from a resin film layer (low-humidity expansible resin) having a humidity expansion coefficient of 20 ppm or less. However, it is preferable that the humidity expansion coefficient is lower, and for this purpose, the amount of biphenylene groups is increased. It is desirable to increase the ratio of imide bonds and increase the imidization rate.

  Here, in the general formula (7), Y is preferably a direct bond (biphenyl bond) or an ether bond, and more preferably a direct bond (biphenyl bond), particularly from the viewpoint of dimensional accuracy such as low moisture absorption dimensionality. In addition, each of the units represented by the following general formula (7) may be one type or two or more types.

  Further, these polyamide-imide resins are preferably non-halogen-based resins that do not contain halogens such as fluorine, chlorine, bromine, and iodine from the viewpoint of environmental considerations.

The imidization rate of the polyamide-imide resin is preferably 50% or more, more preferably 90% or more, and most preferably 95% or more. The higher the imidization rate, the better. The upper limit is 100%. If the imidization rate of the imide bond is less than 50%, the adhesion between the low elastic modulus resin film and the low hygroscopic resin film tends to be low, and the peeling between the resin layers tends to occur. Will fall. As a result, reliability such as folding resistance, flexibility, heat resistance reliability (peel strength) tends to be poor.
The reason for this is that if a molding process such as heat treatment is performed in a laminated structure before the imidization reaction of the second layer is completed, the imidization reaction proceeds with the heat treatment, and the condensation that occurs along with that proceeds. It is estimated that water adversely affects the adhesiveness at the resin layer or at the interface between the resin and the metal foil. Therefore, the production of the resin composition used in the present application is a method such as the isocyanate method described later, in which the imidation ratio of the obtained resin varnish is completed after polymerization even in the second layer resin composition. Preferably, the composition is soluble in an organic solvent because it is essential to dissolve in a polymerization solvent. In addition, even in the production by the isocyanate method, the imidization reaction after polymerization may not necessarily be completed after the polymerization due to the influence of the purity of the monomer or the solvent type, and therefore it is necessary to pay attention to the production conditions.
In order to increase the imidization ratio to 50% or more, in the case of the amine method, a precursor is synthesized by a usual method, and after film formation, the temperature is gradually increased to Tg or more and around Tg (plus or minus 10 ° C.). It is preferable to heat for about 1 hour and perform sufficient imidization treatment. In the isocyanate method, it is preferable to reduce the moisture content to 50 mol% or less of the number of moles of the monomer or to increase the purity of the monomer, for example, using a trimellitic anhydride having a high cyclization rate in the diisocyanate component. It is desirable that the monomer purity is high, for example, the amount of the diamine component which is an impurity is small.
In addition, the measurement of imidation rate can be calculated | required by the method as described in the below-mentioned Example.

  Moreover, these polyamideimide resins must be soluble in an organic solvent from the viewpoint of processability when a flexible metal-clad laminate or a laminated film with an adhesive layer described later is used. The organic solvent mentioned here is, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane. Or at least one selected from the group consisting of dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and cyclopentanone, or a part thereof from toluene, xylene, diglyme, triglyme, tetrahydrofuran, methyl ethyl ketone and methyl isobutyl ketone. It shall be replaced with at least one selected from the group consisting of In the present invention, being soluble in an organic solvent means that any one of the above-mentioned single solvents or a mixed organic solvent containing 20% or more of at least one of them is 10% by weight or more. It means to dissolve. Preferably, it is 15% by weight or more, more preferably 20% by weight or more. In addition, when the resin is in a solid state, whether or not it has been dissolved is determined by adding a specified weight of resin powder passing through 80 mesh into a 200 ml beaker and gently stirring at 25 ° C. for 24 hours. It can be determined that it was dissolved at 25 ° C. for 24 hours and was dissolved in any of gelation, non-uniformity, white turbidity, and precipitation.

In order to be soluble in a solvent, (1) the above-mentioned preferred resin composition is made (2) the ratio of imide group / amide group is lowered (3) polycarboxylic acid component and polyamine component having an alicyclic group described later (4) A polycarboxylic acid component having an aliphatic group, which will be described later, and a copolymerized as a polyamine component (5) A flexible group is introduced into the aromatic ring.
(6) A bulky compound is introduced into the polymer chain.
(7) The polymer is modified with an epoxy compound described later.
Etc. can be achieved.

・・・一般式（５）

... General formula (5)

(In the formula, R5 and R6 may be the same or different and each represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group.)

・・・一般式（６）

... General formula (6)

(In the formula, R 3 and R 4 may be the same or different and each represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group.)

・・・一般式（７）

... General formula (7)

(In the formula, R1 and R2 may be the same or different and each represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group. Y is a direct bond (biphenyl bond), or Indicates an ether bond (—O—).)

One example of means for achieving the desired low-humidity expandable resin layer of the present invention has been described above, but the achievement means is not limited to this. In other words, if appropriate molecular design such as introduction of hydrophobic substituents such as methyl group, ethyl group, fluorine type, or lowering the polarity of the bond to lower the inherent water absorption rate, low humidity expandable resin Is obtained. In order to reduce the polarity of the bond, for example, there are means such as increasing the ratio of the imide bond to the amide bond.

[Production of polyamide-imide resin]
The production of the polyamideimide resin can be synthesized by an ordinary method. For example, an isocyanate method, an amine method (an acid chloride method, a low temperature solution polymerization method, a room temperature solution polymerization method, etc.), etc., but the polyamideimide resin used in the present invention must be soluble in an organic solvent, In order to ensure the above-mentioned folding resistance, bending characteristics, heat resistance reliability, etc., or industrially, an isocyanate method in which a solution at the time of polymerization can be applied as it is is preferable.

  In the case of the isocyanate method, a resin used in the present invention by reacting aromatic tricarboxylic acid anhydride, aromatic dicarboxylic acid, aromatic tetracarboxylic dianhydride and the like as aromatic raw materials with an aromatic stoichiometric amount in an organic solvent. A composition can be obtained. Here, as the aromatic tricarboxylic acid anhydride, trimellitic acid anhydride and the like are used, and as the aromatic tetracarboxylic acid anhydride, pyromellitic acid dianhydride, benzophenone tetracarboxylic dianhydride, biphenyltetracarboxylic acid dianhydride. Anhydrides, diphenyl ether-3,3 ′, 4,4′-tetracarboxylic acid, etc., and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, biphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc. As the diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 2,7-naphthalene diisocyanate, orthotolidine diisocyanate and the like can be used.

  The reaction is preferably carried out in an organic solvent usually at 10 ° C. to 200 ° C. for 1 hour to 24 hours, and the reaction is a catalyst for the reaction of an isocyanate and an active hydrogen compound, for example, tertiary amines, alkali metal compounds, alkaline earth metals You may carry out in presence of a compound etc.

  As a polymerization solvent for producing the polyamideimide resin of the present invention, an organic solvent capable of dissolving the polyamideimide resin can be used. Typical examples of such organic solvents include, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane. Dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, cyclopentanone, etc., preferably N-methyl-2-pyrrolidone. Some of these can be replaced with hydrocarbon organic solvents such as toluene and xylene, ether organic solvents such as diglyme, triglyme and tetrahydrofuran, and ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone.

  The molecular weight of the polyamideimide resin of the present invention is the molecular weight corresponding to 0.3 to 2.5 dl / g in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / dl) and logarithmic viscosity at 30 ° C. Those having a molecular weight corresponding to 0.5 to 2.0 dl / g are more preferable. If the logarithmic viscosity is less than 0.3 dl / g, mechanical properties may be insufficient when formed into a molded product such as a film, and if it exceeds 2.0 dl / g, the solution viscosity becomes high, so that molding processing is performed. May be difficult.

  The polyamide-imide resin of the present invention has the target characteristics of the present invention for the purpose of balancing various performances such as heat resistance, adhesiveness, dimensional stability, flexibility, insulation (migration resistance), and moisture absorption characteristics. It is possible to copolymerize the acid component and amine component shown below in addition to the acid component, isocyanate component, or amine component shown above as long as they are not impaired. Also, a resin separately polymerized by a combination of these acid component and amine component can be mixed and used. Of course, the above-described acid component and the resin component separately polymerized in combination with the amine component may be mixed together. In addition to the acid component described above, the acid component described below and the amine component described above are described below. A separately polymerized resin may be mixed in combination with the amine component.

Examples of the acid component include the following.
a) Tricarboxylic acid; diphenyl ether-3,3 ′, 4′-tricarboxylic acid, diphenylsulfone-3,3 ′, 4′-tricarboxylic acid, benzophenone-3,3 ′, 4′-tricarboxylic acid, naphthalene-1,2 , 4-tricarboxylic acid, monoanhydrides such as tricarboxylic acid such as butane-1,2,4-tricarboxylic acid, esterified compounds, or a mixture of two or more.
b) Tetracarboxylic acid; diphenylsulfone-3,3 ′, 4,4′-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, naphthalene-1,2,4,5-tetracarboxylic acid , Naphthalene-1,4,5,8-tetracarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid monoanhydride, dianhydride , Esterified product alone or a mixture of two or more.
c) Dicarboxylic acid; adipic acid, azelaic acid, sebacic acid, dicarboxylic acid of cyclohexane-4,4′-dicarboxylic acid, and monoanhydrides and esterified products thereof.

For example, the following are mentioned as an amine component.
d) Amine component 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-diethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2 , 2′-diethyl-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-diethoxy-4,4′-diaminobiphenyl, p-phenylenediamine, m -Phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminobiphenyl, 3,3 ' -Diaminobiphenyl, 3,3'-diaminobenzanilide, 4,4'-diaminobenzanilide, 4,4'-diaminobenzophenone, 3,3'-diamy Nobenzophenone, 3,4'-diaminobenzophenone, 2,6-tolylenediamine, 2,4-tolylenediamine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4 ' -Diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, p-xylenediamine, m-xylenediamine, 2,2'-bis (4-amino) Phenyl) propane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4 -(4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3 -Aminophenoxy) biphenyl, tetramethylenediamine, hexamethylenediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, cyclohexane-1,4-diamine, diaminosiloxane, or the corresponding diisocyanate alone or two The above mixture is mentioned. Of course, the monomer component used in the first layer can be used in a part of the second layer, and vice versa.

[Polyamideimide resin solution]
If necessary, for the purpose of improving various properties of the flexible metal-clad laminate or flexible printed circuit board, for example, mechanical properties, electrical properties, slipperiness, flame retardancy, etc., the polyamideimide resin solution of the present invention is used. In addition, other resins, organic compounds, and inorganic compounds may be mixed or reacted to be used in combination. For example, lubricant (silica, talc, silicone, etc.), adhesion promoter, flame retardant (phosphorus, triazine, aluminum hydroxide, etc.), stabilizer (antioxidant, UV absorber, polymerization inhibitor, etc.), plating activity Agents, organic and inorganic fillers (talc, titanium oxide, silica, fluorine polymer fine particles, pigments, dyes, calcium carbide, etc.), silicone compounds, fluorine compounds, isocyanate compounds, blocked isocyanate compounds, acrylic resins, urethanes Resin, polyester resin, polyamide resin, epoxy resin, phenolic resin and organic compounds, or these curing agents, silicon oxide, titanium oxide, calcium carbonate, iron oxide and other inorganic compounds do not hinder the purpose of this invention Can be used together in a range. In addition, if necessary, a catalyst for polyimide formation such as aliphatic tertiary amine, aromatic tertiary amine, heterocyclic tertiary amine, aliphatic acid anhydride, aromatic acid anhydride, hydroxy compound, etc. It may be added. For example, triethylamine, triethylenediamine, dimethylaniline, pyridine, picoline, isoquinoline, imidazole, undecene, hydroxyacetophenone and the like are preferable, and pyridine compound, imidazole compound and undecene compound are particularly preferable. Among them, benzimidazole, triazole, 4 -Pyridinemethanol, 2-hydroxypyridine and diazabicyclo [5.4.0] undecene-7 are preferred, and 2-hydroxypyridine and diazabicyclo [5.4.0] undecene-7 are more preferred.

The concentration of the polyamideimide resin in the polyamideimide resin solution thus obtained can be selected from a wide range, but is generally preferably about 5 to 40% by weight, and more preferably about 8 to 20% by weight. When the concentration is out of the above range, the coatability tends to be lowered. Solvents for the polyamideimide resin solution include N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, and dimethylsulfoxide because of coating properties and the like. , Γ-butyrolactone, cyclohexanone, cyclopentanone and the like are preferable, and N-methyl-2-pyrrolidone is particularly preferable. Some of these can be replaced with hydrocarbon organic solvents such as toluene and xylene, ether organic solvents such as diglyme, triglyme and tetrahydrofuran, and ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone. In addition, since these solvents can also be applied as solvents during polymerization, the polymerization solution can be applied as it is, so that a resin solution having excellent processability can be easily obtained.

  As an appropriate solution viscosity, the B-type viscosity at 25 ° C. is preferably in the range of 1 to 1000 poise. When the viscosity is out of the above range, the coatability may be lowered.

[Metal foil]
A flexible metal-clad laminate can be obtained by laminating with a metal foil using the polyamide-imide resin or resin composition of the present invention. As the metal foil used in the present invention, copper foil, aluminum foil, steel foil, nickel foil, and the like can be used. Composite metal foil obtained by combining these, and metal foil treated with other metals such as zinc and chromium compounds Can also be used. Although there is no limitation in particular about the thickness of metal foil, For example, metal foil of 3-50 micrometers can be used suitably. In particular, for finer circuit pitches, the thickness is preferably 3 to 12 μm, and the surface roughness Rz of the coated surface is preferably in the range of 0.5 to 2.0 μm. If each copper foil characteristic is lower than the lower limit, the peel strength is low, and if it is higher than the upper limit, it tends to be difficult to make a fine pitch.
The metal foil is usually in the form of a ribbon, and its length is not particularly limited. Further, the width of the ribbon-like metal foil is not particularly limited, but is generally preferably about 25 to 300 cm, and particularly preferably about 50 to 150 cm.
As the copper foil, a commercially available electrolytic foil or a rolled foil can be used as it is. For example, “HLS” manufactured by Nippon Electrolytic Co., Ltd., “F0-WS”, “U-WZ” manufactured by Furukawa Circuit Foil Co., Ltd., “NA-VLP”, “DFF” manufactured by Mitsui Mining & Smelting Co., Ltd. Can be mentioned.

[Method for producing flexible metal laminate]
In the present invention, the polyamide-imide resin film layer of the metal laminate having the metal foil only on one side is, for example, the two types of polyamide-imide resins (low elastic modulus resin, The solution can be formed by sequentially applying a solution of low humidity expansible resin), drying the coating (hereinafter referred to as initial drying), and optionally heat treatment and solvent removal (hereinafter referred to as secondary drying).

  As a method of laminating two kinds of resins on the metal foil, the first layer can be applied, and after the initial drying, the second layer can be applied and initially dried, and in some cases, it can be produced by secondary drying. Alternatively, the first layer may be applied, initially dried and secondarily dried, and then the second layer may be applied, initially dried and secondarily dried. Furthermore, after the first layer is applied, the second layer may be applied, and initial drying and secondary drying may be performed. In this case, the first layer and the second layer can be applied simultaneously.

(Coating)
In the present invention, the polyamideimide resin solution is applied directly to the metal foil or via an adhesive layer and dried. The application method is not particularly limited, and a conventionally well-known method can be applied. For example, after adjusting the viscosity of the polyamide-imide resin solution, which is the coating solution, using a roll coater, knife coater, doctor, blade coater, gravure coater, die coater, reverse coater, etc., either directly on the metal foil or with an adhesive layer Can be applied. The adhesive composition when applied through the adhesive layer is not particularly limited, and acrylonitrile butadiene rubber (NBR) adhesive, polyamide adhesive, polyester adhesive, polyester urethane adhesive, epoxy resin Type, acrylic resin type, polyimide resin type, polyamideimide resin type, polyesterimide resin type and other adhesives can be used, but in terms of heat resistance, adhesiveness, bending resistance, etc., polyimide resin type, polyamideimide resin type, or A resin composition in which an epoxy resin is blended with these resins is preferable, and the thickness of the adhesive layer is preferably about 5 to 30 μm.
In addition, for the purpose of improving various properties of the flexible printed circuit board, the polyamideimide resin solution, which is the coating liquid of the present invention, is applied directly to the metal foil or through the adhesive layer, or after application / drying, It is also possible to further apply an adhesive. The adhesive composition and thickness are the same as described above from the viewpoints of heat resistance, adhesion, bending resistance, curling properties of the flexible printed wiring board, and the conditions for coating and drying are the same as those of the polyamideimide resin solution of the present invention. The same conditions can be applied.

(Dry)
In the present invention, there is no particular limitation on the drying conditions after coating, but generally, after initial drying at a temperature 70 ° C. to 130 ° C. lower than the boiling point (Tb (° C.)) of the solvent used in the polyamideimide resin solution, It is preferable to further dry (secondary drying) at a temperature near the boiling point of the solvent or at a temperature equal to or higher than the boiling point.

  When the initial drying temperature is higher than (Tb-70) ° C., foaming occurs on the coated surface, or unevenness of the residual solvent in the thickness direction of the resin layer increases, so that the metal laminate is warped (curl). There is also a large warp of a flexible printed circuit board obtained by processing the circuit.

  Moreover, when drying temperature is lower than (Tb-130) degreeC, drying time will become long and productivity will fall. The initial drying temperature varies depending on the type of solvent, but is generally about 60 to 150 ° C, preferably about 80 to 120 ° C. The time required for the initial drying is generally preferably an effective time at which the solvent remaining rate in the coating film is about 5 to 40% under the above temperature conditions, and generally about 1 to 30 minutes is preferable. Preferably, it is about 2 to 15 minutes.

  The secondary drying conditions are not particularly limited, and may be dried near the boiling point of the solvent or at a temperature equal to or higher than the boiling point, but is generally 120 ° C to 400 ° C, preferably 200 ° C to 300 ° C. If it is less than 120 degreeC, drying time will become long and productivity will fall, and if it exceeds 300 degreeC, degradation reaction may advance depending on resin composition, and a resin film may become brittle. The time required for the secondary drying may be an effective time that generally eliminates the solvent remaining rate in the coating film under the above temperature conditions, but is generally about several minutes to several tens of hours.

In the present invention, drying may be performed under an inert gas atmosphere or under reduced pressure. Examples of the inert gas include nitrogen, carbon dioxide, helium, and argon, but it is preferable to use easily available nitrogen. Moreover, when performing under reduced pressure, it is preferable to carry out under the pressure of about 10 < ^-5 > -10 < ³ > Pa, preferably about 10 < ^-1 > -200 Pa.

  In the present invention, there are no particular limitations on the drying method for both initial drying and secondary drying, but it can be performed by a conventionally known method such as a roll support method or a floating method. Further, continuous heat treatment in a heating furnace such as a tenter type, winding in a wound state, and heat treatment in a batch type oven may be performed. In the case of a batch type, it is preferable to wind up so that a coating surface and a non-coating surface do not contact. As a heating method, a conventionally known electric furnace, IR heater, far infrared heater, or the like can be applied.

  In the present invention, the ratio (T1) of the thickness (T1) of the resin layer (low elastic modulus resin layer) having an elastic modulus of 4800 Mpa or less and the thickness (T2) of the resin layer (low humidity expandable resin layer) having a humidity expansion coefficient of 20 ppm or less. / (T2) is preferably 0.05 to 5, more preferably 0.1 to 5, and even more preferably 0.15 to 5. When (T1) / (T2) is less than 0.05, the flexibility, folding resistance, and heat resistance are inferior, and when it exceeds 5, the dimensional stability is inferior. Further, from the viewpoint of achieving both heat resistance, flexibility, folding resistance, and dimensional stability, a more preferable lamination method is a low elastic modulus in which the heat resistant resin layer on the side in contact with the metal foil has an elastic modulus of 4800 Mpa or less. The resin layer that is not in contact with the metal foil is a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less.

  The flexible metal-clad laminate of the present invention thus obtained is characterized by being excellent in heat resistance, dimensional stability, and adhesiveness because it has a metal foil directly on at least one surface of the polyamideimide resin film layer. In addition, the isocyanate method does not require an imidization step and can be molded only by drying the solvent, or because it does not require heat treatment at high temperatures, so it can be manufactured at low cost, and has flexibility, folding resistance, and heat resistance. It is characterized by excellent properties.

The film thickness of the low elastic modulus resin layer is preferably 3 to 50 μm, more preferably 5 to 30 μm, and most preferably 7 to 20 μm. If it is less than 3 μm, the peel strength, flexibility and folding resistance after soldering tend to be lowered. If it exceeds 50 μm, the hygroscopic dimensional change rate tends to decrease.
The film thickness of the low-humidity expandable resin layer is preferably 10 to 60 μm, more preferably 20 to 50 μm, and most preferably 25 to 40 μm. If it is less than 10 μm, the hygroscopic dimensional change rate tends to increase. If it exceeds 60 μm, the flexibility and folding resistance tend to be lowered.
In the flexible metal-clad laminate of the present invention consisting of a polyamide-imide resin film layer and a metal foil, the thickness of the entire polyamide-imide resin film layer can be selected from a wide range, but in general the thickness after absolutely dry About 5-100 micrometers is preferable, More preferably, it is about 10-50 micrometers. When the thickness is less than 5 μm, the mechanical properties such as film strength and handling properties are inferior. On the other hand, when the thickness exceeds 100 μm, the properties such as flexibility and workability (drying property, coating property) are deteriorated. Tend to. In addition, the flexible metal-clad laminate of the present invention may be subjected to a surface treatment as necessary. For example, surface treatment such as hydrolysis, low-temperature plasma, physical roughening, and easy adhesion coating treatment can be performed.

The double-sided flexible metal laminate of the present invention is a metal laminate having metal foils on both sides. For example, the resin surfaces of a metal laminate in which metal foils are laminated only on one side molded as described above are heated. It can be produced by a conventionally known method such as laminating or by a conventionally known method through an adhesive layer.
The method of laminating is not particularly limited, and conventionally known methods such as roll laminating, press laminating, belt press laminating and the like can be adopted, and the laminating temperature is usually Tg of the resin or more, for example, low humidity expansive resin ( Tg of the resin layer on the surface to be bonded), which is preferably 300 ° C. to 500 ° C., more preferably 350 ° C. to 450 ° C., and still more preferably 380 ° C. to 430 ° C. If it is less than 300 ° C., the adhesiveness is insufficient, and if it exceeds 500 ° C., the resin is deteriorated and the mechanical properties tend to be lowered. The laminating time is not particularly limited, but is usually 10 seconds to 10 hours, preferably 1 minute to 1 hour, more preferably 3 minutes to 30 minutes. If it is less than 10 seconds, the adhesiveness is insufficient, and if it exceeds 10 hours, the resin layer is deteriorated and the mechanical properties tend to be lowered.
The adhesive composition when applied through the adhesive layer is not particularly limited, and acrylonitrile butadiene rubber (NBR) adhesive, polyamide adhesive, polyester adhesive, polyester urethane adhesive, epoxy resin Type, acrylic resin type, polyimide resin type, polyamideimide resin type, polyesterimide resin type and other adhesives can be used, but in terms of heat resistance, adhesiveness, bending resistance, etc., polyimide resin type, polyamideimide resin type, or A resin composition in which an epoxy resin is blended with these resins is preferable, and the thickness of the adhesive layer is preferably about 5 to 30 μm. From the viewpoint of insulation performance, polyester or polyester urethane resin, or a resin composition in which an epoxy resin is blended with these resins is preferable, and the thickness of the adhesive layer is preferably about 5 to 30 μm. The thickness of the adhesive is not particularly limited as long as it does not hinder the performance of the flexible printed circuit board, but if the thickness is too thin, sufficient adhesiveness may not be obtained. If the thickness is too thick, processability (drying property, coating property) and the like may be deteriorated. As a means for forming a laminated structure through the adhesive layer, a heat-resistant film molded using the heat-resistant resin of the present invention described later and a metal foil are bonded together by the above-mentioned adhesive by a method such as heat lamination. You can also.

[Flexible printed circuit board]
Using the flexible metal-clad laminate of the present invention, a flexible printed circuit board can be produced by a method such as a subtractive method. When the circuit surface is coated for the purpose of protecting the solder resist of the conductor circuit or from dirt and scratches, a heat-resistant film such as polyimide is bonded to the wiring board (the conductor circuit is formed by an adhesive) by a conventionally known method. A method of bonding to a formed base substrate) or a method of applying a liquid coating agent to a wiring board by a screen printing method can be applied. As the liquid coating agent, conventionally known epoxy-based or polyimide-based inks can be used, but polyimide-based inks are preferable. It is also possible to directly bond an epoxy or polyimide adhesive sheet to the wiring board. The flexible printed circuit board obtained in this way has excellent heat resistance, dimensional stability, and adhesiveness, as well as excellent flexibility, folding resistance, moisture absorption, and insulation. Since it can be used for applications, there are significant industrial advantages.

(Method for manufacturing flexible printed circuit board)
The flexible printed circuit board of the present invention can be manufactured using a conventionally known process except that the material of each layer described above is used.
In one preferred embodiment, a cover film with an adhesive is produced by laminating an adhesive layer on a polyimide film. On the other hand, a semi-finished product in which a desired circuit pattern is formed on the base film layer (hereinafter referred to as “base film-side semi-finished product”) is manufactured. A flexible printed wiring board can be obtained by bonding the cover film with adhesive and the base film side semi-finished product thus obtained.

(Manufacturing method of base film side semi-finished product)
A base film side semi-finished product is manufactured by forming a circuit in a metal foil layer using the above-mentioned flexible metal-clad laminate. A conventionally known method can be used to form the circuit. An additive method may be used and a subtractive method may be used. The subtractive method is preferable.
An arbitrary pattern can be formed as the circuit wiring pattern. In particular, the flexible printed circuit board of the present invention exhibits a high level of performance even in a circuit having a fine wiring pattern, and therefore the flexible printed circuit board of the present invention is particularly advantageous in a circuit having a fine wiring pattern.

Specifically, the wiring thickness of the circuit can be 100 μm or less, the wiring thickness can be 50 μm or less, and the wiring thickness can be 30 μm or less. It is also possible to make the thickness of the wiring 10 μm or less.
The interval between the wirings can be 100 μm or less, can be 50 μm or less, can be 30 μm or less, and can be 10 μm or less. The sum of the thickness of the wiring and the wiring interval (circuit pitch) can be 100 μm or less, can be 60 μm or less, and can also be 20 μm or less.

(Manufacturing method of cover film with adhesive)
The cover film with an adhesive is manufactured, for example, by applying an adhesive to a polyimide film and drying it. The adhesive is not particularly limited, and acrylonitrile butadiene rubber (NBR) adhesive, polyamide adhesive, polyester adhesive, polyester urethane adhesive, epoxy resin, acrylic resin, polyimide resin, polyamideimide Resin-based and polyesterimide resin-based adhesives can be used, but from the viewpoint of heat resistance, adhesiveness, bending resistance, etc., polyimide resin-based, polyamide-imide resin-based, or a resin composition in which an epoxy resin is blended with these resins Is preferred. As a method of laminating the adhesive, a general method can be applied, and there is no particular limitation. It can be applied to an insulating film, dried and laminated. In some cases, it is possible to form an adhesive layer on the releasable film by the above application method and to laminate the adhesive layer on the insulating film by a transfer method. Drying conditions are set as appropriate according to the adhesive used. Usually, it is about 30 to 150 ° C. Further, if necessary, a crosslinking reaction can be performed in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

  The obtained cover film with adhesive may be used as it is for pasting with the base material-side semi-finished product, and after sticking and storing the release film, it is pasted with the base film-side semi-finished product. They may be used together.

(Lamination of base film side semi-finished product and cover film with adhesive)
Any method can be used as a method of bonding the base film side semi-finished product and the cover film with adhesive. For example, it can bond together using a press or a roll. Moreover, both can also be bonded together, heating by the method of using a heating press or a heating roll press apparatus.

  For example, if the adhesive layer in the semi-finished product is in an uncured or semi-cured state, it can be cured by proceeding with the crosslinking reaction of the adhesive layer by heating at the time of bonding. It is also possible to easily obtain a final product in which the agent layer is completely cured. When the crosslinking reaction is insufficient, or when it is necessary to precisely control the crosslinking reaction, post-curing can be performed as necessary after pasting by any of the above methods.

[How to use flexible printed circuit board]
The flexible printed circuit board of the present invention can have any laminated structure that can be employed as a flexible printed circuit board. For example, as above-mentioned, it can be set as the flexible printed circuit board comprised from four layers, a base film layer, a metal foil layer, an adhesive bond layer, and a cover film layer.

  Further, if necessary, a configuration in which two or three or more of the above-mentioned flexible printed boards are laminated may be employed. For example, it is possible to laminate a plurality of the above-mentioned four-layer type flexible printed boards and bond the flexible printed board and the flexible printed board with an adhesive as necessary. More specifically, for example, the base film layer of the first flexible printed circuit board, the metal foil layer of the first flexible printed circuit board, the adhesive layer of the first flexible printed circuit board, and the cover of the first flexible printed circuit board A film layer; an adhesive layer that bonds the first flexible printed circuit board and the second flexible printed circuit board; a base film layer of the second flexible printed circuit board; a metal foil layer of the second flexible printed circuit board; A total of nine layers of the adhesive layer of the flexible printed circuit board and the cover film layer of the second flexible printed circuit board can be sequentially laminated.

In addition, for example, the four-layer type flexible printed circuit board can be formed in such a manner that the bottoms of two base film films are bonded to each other by an adhesive layer and bonded back to back. In this case, for example, if the 4-layer type flexible printed circuit board is used,
A cover film layer of a first flexible printed circuit board;
An adhesive layer of the first flexible printed circuit board;
A metal foil layer of the first flexible printed circuit board;
A base film layer of a first flexible printed circuit board;
An adhesive for adhering the base films of the first flexible printed circuit board and the second flexible printed circuit board;
A base film layer of a second flexible printed circuit board;
The metal foil layer of the second flexible printed circuit board A total of 9 layers of the adhesive layer of the second flexible printed circuit board and the cover film layer of the second flexible printed circuit board can be laminated in order.

[Applications of flexible printed circuit boards]
The flexible printed circuit board of the present invention can be used for various products in which a flexible printed circuit board has been conventionally used. In addition, the flexible printed circuit board of the present invention is excellent in heat resistance, dimensional stability, flexibility, folding resistance, insulation, and the like, and therefore, applications where particularly thin wiring is required and the wiring interval is narrow. It can be suitably used for applications that need to be performed. For example, it is suitable for products whose wiring thickness is 30 μm or less. Further, for example, it is suitable for a product having a wiring interval of 60 μm or less, more suitable for a product having a wiring interval of 30 μm or less, and further suitable for a product having a wiring interval of 10 μm or less. Therefore, it can be suitably used for applications in which the sum of the thickness of the wiring and the wiring interval (circuit pitch) is narrow. It is suitable for products having a circuit pitch of 100 μm or less, more suitable for products having a circuit pitch of 60 μm or less, more suitable for products having a circuit pitch of 30 μm or less, and particularly suitable for products having a circuit pitch of 20 μm or less.

  Examples of specific final products in which the flexible printed circuit board of the present invention is used include flat panel displays, drive modules for liquid crystal monitors such as mobile phones, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not particularly limited by the examples.
The evaluation method of the characteristic value in each example is as follows. The powdered polyamideimide resin sample used for evaluation was prepared by reprecipitation and purification of the polymer dope obtained in each synthesis example with a large amount of acetone. Moreover, unless otherwise indicated, the resin film (base film) used for various measurements and evaluations is obtained by using 35% of second chloride chloride as the metal foil of the flexible metal-clad laminate obtained in each of Examples and Comparative Examples. Etching was removed with iron (40 ° C.) to obtain a resin film.

<Logarithmic viscosity>
Using a powdered polymer sample, it was dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.5 g / dl. The solution viscosity of the solution and the solvent viscosity were 30 ° C., and an Ubbelohde viscosity. It measured with the pipe | tube and it calculated by the following formula.
Logarithmic viscosity (dl / g) = [ln (V1 / V2)] / V3

  In the above formula, V1 represents the solution viscosity measured with an Ubbelohde type viscosity tube, V2 represents the solvent viscosity measured with an Ubbelohde type viscosity tube, and V1 and V2 represent a polymer solution and a solvent (N-methyl-2-pyrrolidone). Was determined from the time taken to pass through the capillary of the viscosity tube. V3 is the polymer concentration (g / dl).

<Tg>
The polyamideimide resin sample shown in Table 1 was applied to a metal foil and dried, and then the metal foil was etched away with 35% ferric chloride (40 ° C.) to obtain a single-layer resin film. Using this resin film (sample size 4 mm width × 15 mm length) with a dynamic viscoelasticity measuring device (Leobibron manufactured by Orientec Co., Ltd.) under the conditions of a frequency of 1 Hz and a heating rate of 10 ° C./min, from the peak top of Tan δ Tg was determined.

<Coefficient of thermal expansion (CTE)>
The polyamideimide resin sample shown in Table 1 was applied to a metal foil and dried, and then the metal foil was etched away with 35% ferric chloride (40 ° C.) to obtain a single-layer resin film. The thermal expansion coefficient of this resin film was measured by the TMA (Thermal Mechanical Analysis / Rigaku Corporation) tensile load method under the following conditions.
The film was measured for a film that was once heated to an inflection point in nitrogen at a heating rate of 10 ° C./min and then cooled to room temperature.
Load: 5g
Sample size: 4 (width) x 20 (length) mm
Temperature increase rate: 10 ° C./min Atmosphere: Nitrogen measurement temperature range: 100 ° C. to 200 ° C.

<Dimensional change rate>
The average value was obtained by measuring the MD direction and the TD direction with IPC-FC241 (IPC-TM-650, 2.2.4 (c)) at 150 ° C. for 30 minutes.

<Adhesive strength>
According to IPC-FC241 (IPC-TM-650, 2.4.9 (A)), the adhesive strength between the circuit pattern and the heat-resistant resin layer was measured using a sample in which the circuit pattern was created by the subtractive method.

<Peel strength after soldering>
In accordance with IPC-FC241 (IPC-TM-650, 2.4.9 (A)), a circuit pattern was created by a subtractive method, and the sample after floating in a solder bath at 350 ° C. for 30 seconds was used. The adhesive strength was measured. The sample was floated on the solder bath in such a manner that the resin base material surface was in contact.

<Humidity expansion coefficient (CHE)>
First, a polyamide-imide resin sample shown in Table 1 was coated on a metal foil and dried to prepare a metal-clad laminate. And it measured by the following.
(1) A hole is made in a certain position of the metal-clad laminate according to IPC-FC 241 (IPC-TM-650, 2.2.4 (c)), and humidity is adjusted at 25 ° C. and 65% for 4 hours. Measure the distance between holes.
(2) The front surface of the metal layer of the metal-clad laminate was removed with ferric chloride (etching), and the resulting resin film was subjected to 25% relative humidity in an atmosphere of 20%, 40%, 65%, and 90%. Condition at 24 ° C for 24 hours.
(3) According to IPC-FC 241 (IPC-TM-650, 2.2.4 (c)), the distance between holes in the resin film is measured, and the distance between holes in the metal foil laminate in (1). The dimensional change rate is obtained based on the above.
(4) The rate of dimensional change in (3) was plotted against each relative humidity, and the slope with respect to that humidity was defined as the humidity expansion coefficient (CHE).

<Folding resistance>
A resin film (sample size; 25.4 mm × 88.9 mm) obtained by etching away the metal foil is flexible according to JIS L 1096 using a Gurley type flexibility tester manufactured by Toyo Seiki Seisakusho Co., Ltd. The degree (a measure of repulsive force) was measured. The determination of the measurement result was evaluated as “x” when the value of the flexibility was 120 mg or more and “◯” when it was lower than 120 mg.

<Strength, elongation and elastic modulus of resin film>
The polyamideimide resin sample shown in Table 1 was applied to a metal foil and dried, and then the metal foil was etched away with 35% ferric chloride (40 ° C.) to obtain a single-layer resin film. A sample having a width of 10 mm and a length of 100 mm was prepared from this resin film, and measured with a tensile tester (trade name “Tensilon tensile tester”, manufactured by Toyo Baldwin) at a tensile speed of 20 mm / min and a distance between chucks of 40 mm. did.

<Imidization rate>
Using a powdered polymer sample, the absorbance ratio was determined from the absorption of imide (1380 cm-1) and the absorption of benzene (1510 cm-1) by the infrared spectrophotometer (manufactured by Shimadzu Corporation) KBr method. Asked.
The calculation of the imidization rate was carried out in the same manner using a powdered sample prepared by scraping the resin surface of a copper-clad laminate film prepared from the varnish of the same resin composition under the following conditions. The absorbance ratio between 1) and the benzene nucleus (1510 cm −1) was determined, and this absorbance ratio was calculated as 100%.
<Copper-clad laminated film making method>
Using a knife coater, an electrolytic copper foil having a thickness of 12 μm (trade name “HLS”, manufactured by Nihon Denki Co., Ltd.) was coated to a thickness of 20 μm after solvent removal, and dried at a temperature of 100 ° C. for 5 minutes. . Next, vacuum drying conditions: 200 ° C. × 24 hr (the degree of vacuum varied between 10 and 100 Pa due to the volatilization of the solvent)
Heating under nitrogen (flow rate; 20 L / min); 260 ° C. × 10 hr
And heat treated.
<Solder heat resistance after humidification>
In accordance with IPC-FC241 (IPC-TM-650, 2.4.9 (A)), a circuit pattern was prepared by a subtractive method, and humidified at 40 ° C. in an atmosphere of 90% RH for 24 hours. Next, the sample after floating in a solder bath at 280 ° C. for 30 seconds was visually observed for the presence or absence of swelling or peeling. A sample that did not swell or peel was rated as ◯, and a sample that did swell or peeled off was rated as x.

Synthesis example 1 (resin 1)
In a reaction vessel, 192 g of trimellitic anhydride (manufactured by Mitsubishi Gas Chemical Co., Inc.), 209 g of 1,5-naphthalene diisocyanate (100 mol%, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 1 g of diazabicycloundecene (San Apro Co., Ltd.) And 1836 g of N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) (manufactured by Mitsubishi Chemical Corporation) (polymer concentration: 15%), heated to 100 ° C. in 2 hours, The reaction was continued for 5 hours. Subsequently, NMP534g (polymer concentration 12 weight%) was added, and it cooled to room temperature. The obtained polymer dope was yellowish brown transparent and the polymer was dissolved in NMP. The logarithmic viscosity and imidation ratio were as shown in Table 1. In addition, a resin film (single layer) obtained by etching and removing the metal foil of the metal laminate formed by the method described in Example 1 with 35% ferric chloride (40 ° C.) using this resin solution. Table 1 shows Tg, strength, elongation, elastic modulus, CHE, and CTE.
The purity of each monomer was 99% or more.

Synthesis Examples 2-13
A resin varnish was prepared under the same polymerization conditions as in Synthesis Example 1 except that the monomer composition was changed to the contents shown in Table 1. The logarithmic viscosity, imidization rate, Tg, strength, elongation, and elastic modulus were as shown in Table 1.

Examples 1, 2, 5-9, Comparative Examples 1-6
Using the polymer solution obtained as described above, a flexible metal-clad laminate was prepared under the following molding process conditions, and various properties with the contents shown in Tables 1 and 2 were evaluated.
(A) Initial drying A flexible metal-clad laminate with the base resin layer having a two-layer configuration and an initial drying was obtained with the layered configuration shown in Table 2 for the resin solution obtained above.
That is, using a knife coater on a 12 μm thick electrolytic copper foil (trade name “NA-VLP”, manufactured by Mitsui Kinzoku Mine Co., Ltd.), the thickness after desolvation is as shown in Table-2. The layer was coated and dried at a temperature of 100 ° C. for 5 minutes. Next, in the same manner, the coating is further coated and dried at a temperature of 100 ° C. for 10 minutes so that the thickness after solvent removal is as shown in Table 2. Thus, an initially dried flexible metal-clad laminate is obtained. It was.
(B) Secondary drying The above initially dried laminate was wound around an aluminum can with an outer diameter of 16 inches so that the coated surface was on the outside, and was heat-treated with a vacuum dryer or an inert oven under the conditions shown below. . The solvent in the coating film of the obtained laminate was completely removed.
Drying conditions under reduced pressure: 200 ° C. × 24 hr (the degree of reduced pressure varied between 10 and 100 Pa due to volatilization of the solvent)
Heating under nitrogen (flow rate; 20 L / min); 260 ° C. × 10 hr

Examples 3 and 4
Example 2 except that the copper foil was changed to an electrolytic copper foil “U-WZ” made by Furukawa Circuit Foil Co., Ltd. having a thickness of 12 μm and an electrolytic copper foil “HLS” made by Nippon Electrolytic Co., Ltd. having a thickness of 12 μm. A flexible metal laminate was prepared by each method, and various properties having the contents shown in Tables 1 and 2 were evaluated.

Meaning of abbreviation
TMA: trimellitic anhydride
BTDA; 3, 3, '4, 4'-benzophenone tetracarboxylic dianhydride
BPDA; 3, 3, '4, 4'-biphenyltetracarboxylic dianhydride
PMA: pyromellitic anhydride
TPA; terephthalic acid
NDI: 1,5-naphthalene diisocyanate
TODI; O-tolidine diisocyanate
DSDA; 3, 3, '4, 4'-diphenylsulfone tetracarboxylic dianhydride
CHE: Humidity expansion coefficient, CTE: Thermal expansion coefficient

As described above, the flexible metal laminate of the present invention is composed of a plurality of resin compositions having good flexibility, folding resistance, heat resistance, low humidity dimensional change rate, and high Tg. Excellent folding resistance, flexibility, dimensional accuracy and heat resistance reliability depending on conditions. Furthermore, since the resin composition to be used is soluble in an organic solvent, it can be produced at low cost without the need for heat treatment at high temperatures. Therefore, since a flexible substrate that can be used even for high-density mounting substrate applications can be manufactured at low cost, there are significant industrial advantages.

Claims (6)

A flexible metal laminate in which a metal foil is laminated on at least one surface of a heat resistant resin film, the heat resistant resin film having a two-layer structure composed of a polyamide-imide resin soluble in an organic solvent, ,
a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a naphthalene group is 80 mol%.
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) formed from a resin layer having an imidization rate of imide bond of 50% or more and an elastic modulus of 4800 Mpa or less, and the other layer is a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less. A flexible metal laminate which is formed. When the heat-resistant resin layer on the side in contact with the metal foil is a) the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the naphthalene group is Has a monomer component of 80 mol%
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) Low humidity expansibility in which the imidization rate of the imide bond is 50% or more and is formed from a resin layer having an elastic modulus of 4800 Mpa or less, and the resin layer on the side not in contact with the metal foil has a humidity expansion coefficient of 20 ppm or less The flexible metal laminate according to claim 1, wherein the metal foil is laminated only on one side, which is a resin layer. The flexible metal laminate according to claim 1 or 2, wherein a metal foil is formed on one side, wherein a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less,
a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a biphenylene group is 100 mol% or more, and b) The molar ratio of imide bond to amide bond is 99/1 to 65/35 molar ratio,
c) A flexible metal laminate having an imidization ratio of imide bonds of 50% or more. a) When the total amount of the acid component is 100 mol%, the total amount of the amine component is 100 mol%, and the total of the acid component and the amine component is 200 mol%, the monomer component having a naphthalene group is 80 mol%.
And b) the molar ratio of imide bond to amide bond is 99/1 to 60/40 molar ratio,
c) Ratio of the thickness (T1) of the resin layer having an imidization rate of imide bond of 50% or more and an elastic modulus of 4800 Mpa or less to the thickness (T2) of a low-humidity expandable resin layer having a humidity expansion coefficient of 20 ppm or less (T1) ) / (T2) is 0.05-5, The flexible metal laminated body in any one of Claims 1-3 characterized by the above-mentioned. The double-sided flexible metal laminated body obtained by bonding together the flexible metal laminated body in any one of Claims 1-4 so that metal foil may be formed in both surfaces. A flexible printed circuit board obtained from the flexible metal-clad laminate according to claim 1.