JP2016141152A - Low hygroscopic flexible metal-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low hygroscopic metal-clad laminate.SOLUTION: There is provided the flexible metal-clad laminate comprising a metal foil and an insulating layer. The insulation layer includes: a first polyimide layer which is formed on one surface or both surfaces of the metal foil and has a glass transition temperature of 200 to 400°C and a moisture absorptivity of 0.5 wt.% or less; a second polyimide layer which is formed on one surface of the first polyimide layer and has a glass transition temperature of 300 to 500°C and a moisture absorptivity of 0.5 w.t% or less; and a third polyimide layer which is formed on one surface of the second polyimide layer and has a glass transition temperature of 200 to 400°C and a moisture absorptivity of 0.5 wt.% or less. The insulation layer has a moisture absorptivity of 0.5 wt.% or less, and a solder heat resistant temperature of 350°C or more after moisture absorption for 72 hours at a temperature of 40°C and at a relative humidity of 90%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flexible metal clad laminate for use in the manufacture of a flexible printed circuit board, characterized in that it has a low moisture absorption rate and excellent solder-resistance after moisture absorption. To do.

  A flexible metal clad laminate used in the manufacture of a flexible printed circuit board is a laminate of a conductive metal foil and an insulating resin. Since it is possible and can be bent in a narrow space, its use is increasing along with the trend toward smaller and lighter electronic devices. Flexible metal-clad laminates are divided into two-layer and three-layer methods, but the three-layer method using an adhesive is inferior in heat resistance and flame retardancy compared to the two-layer method, and the dimensions during the heat treatment process There is a problem that the change is large. Therefore, in the manufacture of flexible printed circuit boards, a recent trend is generally to use a two-layer flexible metal-clad laminate rather than a three-layer method.

  In recent years, the use of double-sided metal-clad laminates has increased with the trend of thin, light and short circuits. A double-sided metal-clad laminate is generally manufactured by laminating a thermoplastic polyimide formed on the outermost layer of a polyimide resin with a metal foil, but due to the presence of the thermoplastic polyimide resin, the insulation resistance after moisture absorption of the insulating layer is increased. There is a problem that solder-resistance is poor. In particular, the soldering resistance after moisture absorption becomes more important because the temperature of the recent lead-free soldering process is as high as 250 ° C or higher, contrary to the fact that the bonding temperature at the time of existing soldering was 200 ° C. Yes.

  As a conventional technique, Patent Document 1 exemplifies a case where a polyimide resin having a special structure is used as the thermoplastic polyimide resin layer. In this case, the moisture absorption heat resistance temperature is only 260 ° C., which is 300 ° C. or more. Under severe conditions, there is a problem with solder resistance.

Japanese Unexamined Patent Publication No. 2002-363284 (December 18, 2002)

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have laminated polyimides having glass transition temperatures in different ranges in multiple layers, and have improved solder-resistance even after moisture absorption. The inventors have invented an excellent flexible metal-clad laminate having a low moisture absorption rate.

  More specifically, by controlling the moisture absorption rate of the polyimide resin constituting the insulator of the flexible metal-clad laminate to a predetermined level or less, the flexible metal-clad excellent in solder-resistance after moisture absorption (Solder-resistance). It aims at providing a laminated body.

  The present invention relates to a flexible metal-clad laminate. More specifically, the present invention is a flexible metal-clad laminate including a metal foil and an insulating layer, and the insulating layer is formed on one side or both sides of the metal foil and has a glass transition temperature of 200 to 400 ° C. A first polyimide layer having a moisture absorption rate of 0.5 wt% or less, and a second polyimide layer formed on one side of the first polyimide layer, having a glass transition temperature of 300 to 500 ° C. and a moisture absorption rate of 0.5 wt% or less. A polyimide layer and a third polyimide layer formed on one side of the second polyimide layer, having a glass transition temperature of 200 to 400 ° C. and a moisture absorption of 0.5 wt% or less, and the moisture absorption of the insulating layer is The present invention relates to a flexible metal-clad laminate having a solder heat resistance temperature of 350 ° C. or higher after absorbing moisture at 40 ° C. and relative humidity 90% for 72 hours.

  The embodiments described above are not limited to the described contents, and include all matters that can be easily changed by those skilled in the art. As an example, other forms of devices may be used to implement the same technique.

  The flexible metal-clad laminate according to the present invention has a low moisture absorption rate and has a high solder heat resistance even after moisture absorption, so it has excellent solder-resistance and is more stable than existing products. A laminate can be provided.

It is the figure which illustrated the cross section of the metal-clad laminated body by an example of this invention. It is the figure which illustrated the cross section of the metal-clad laminated body by an example of this invention. It is the figure which illustrated the cross section of the metal-clad laminated body by an example of this invention.

  Hereinafter, the flexible metal-clad laminate according to the present invention will be described in detail with reference to specific examples and comparative examples. At this time, unless otherwise defined in the technical terms and scientific terms used, it has the meaning normally understood by a person having ordinary knowledge in the technical field to which the present invention belongs. Descriptions of known functions and configurations that may obscure the gist of are omitted.

  When the polyimide resin is immersed in a high-temperature solder bath after absorbing moisture, the absorbed moisture rapidly volatilizes and layer separation, foaming, expansion, etc. occur at the polyimide resin layer or at the interface between the polyimide resin layer and the metal foil layer. Defects occur. The reason why such a defect occurs is that when the moisture absorbed in the polyimide resin is immersed in a high-temperature solder bath, rapid vaporization occurs and the rigidity of the resin cannot overcome the vapor pressure of moisture. Therefore, in order to improve solder heat resistance due to moisture absorption, it is necessary to maintain the rigidity of the resin even at high temperatures. For this reason, methods such as adjusting the storage elastic modulus at high temperatures and increasing the crystallinity are used. I came. However, the solder heat resistance temperature after moisture absorption embodied by such a method is 300 ° C. inside or outside, and it is difficult to realize solder heat resistance higher than that. Therefore, it is necessary to limit the amount of moisture absorbed by the polyimide-based resin to a predetermined level, and if the polyimide main chain contains fluorine atoms by continuing experiments and studies from such a viewpoint, the moisture absorption rate is significantly reduced. The headline and the present invention were completed.

  First, a flexible metal-clad laminate according to an embodiment of the present invention includes a metal foil and an insulating layer, the insulating layer is formed on one or both sides of the metal foil, and has a glass transition temperature of 200 to 400 ° C. A first polyimide layer having a moisture absorption rate of 0.5 wt% or less and a second polyimide formed on one surface of the first polyimide layer, having a glass transition temperature of 300 to 500 ° C. and a moisture absorption rate of 0.5 wt% or less. And a third polyimide layer formed on one surface of the second polyimide layer, having a glass transition temperature of 200 to 400 ° C. and a moisture absorption of 0.5 wt% or less.

  At this time, the moisture absorption rate of the insulating layer may be 0.5 wt% or less, and the solder heat resistance temperature after moisture absorption for 72 hours at 40 ° C. and 90% relative humidity may be 350 ° C. or more.

Further, the first polyimide layer or the third polyimide layer may include 50 to 100 mol% of a polyimide resin having a structure represented by the following chemical formula 1.
(In Chemical Formula 1, n is an integer of 1 to 100,000,000.)

In addition, the second polyimide layer may include 50 to 100 mol% of a polyimide resin including any one selected from the following chemical formulas 2 to 3 or a copolymer thereof.
(In Chemical Formulas 2 to 3, m or l are each independently an integer of 1 to 100,000,000.)

  In the present invention, the flexible metal-clad laminate can be laminated in the order of metal foil / first polyimide layer / second polyimide layer / third polyimide layer / second polyimide layer / first polyimide layer / metal foil.

  The first polyimide layer or the third polyimide layer may have a glass transition temperature of 300 to 400 ° C., and the solder heat resistance temperature after absorbing moisture for 72 hours at 40 ° C. and relative humidity 90% of the insulating layer is 350 ° C. or more. It may be.

  The present invention provides a flexible metal-clad laminate in which a metal foil is formed on one or both sides of an insulating layer, and a multilayered flexible metal-clad laminate in which the insulating layer is composed of a plurality of polyimide resins.

  The insulating layer according to the present invention has a structure in which a plurality of polyimide-based resins are laminated, and can be composed of two or more layers. As an example, as shown in FIGS. A three-layer structure of polyimide layer 200 / third polyimide layer 300 (FIG. 1) or five layers of first polyimide layer 100 / second polyimide layer 200 / third polyimide layer 300 / second polyimide layer 200 / third polyimide layer 300 The structure (FIG. 2) or the six-layer structure (FIG. 3) of the first polyimide layer 100 / second polyimide layer 200 / third polyimide layer 300 / first polyimide layer 100 / second polyimide layer 200 / third polyimide layer 300 There may be.

That is, the insulating layer further includes a fourth polyimide layer laminated on the third polyimide layer, and the fourth polyimide layer has the same characteristics as the second polyimide layer. The fifth polyimide layer further includes a fifth polyimide layer laminated on the fourth polyimide layer, and the fifth polyimide layer has the same characteristics as the third polyimide layer (structure in FIG. 2).
As another form, the insulating layer further includes a fourth polyimide layer laminated on the third polyimide layer, and the fourth polyimide layer has the same characteristics as the first polyimide layer. The fifth polyimide layer further includes a fifth polyimide layer laminated on the fourth polyimide layer, and the fifth polyimide layer has the same characteristics as the second polyimide layer. The sixth polyimide layer further includes a sixth polyimide layer laminated on the fifth polyimide layer, and the sixth polyimide layer has the same characteristics as the third polyimide layer (structure of FIG. 3).

  In general, a flexible metal-clad laminate can be produced by forming a single polyimide resin layer on a metal foil layer, but in this case, there are the following problems. First, when using a single thermosetting polyimide resin layer, the adhesive strength to the metal foil is low, and there is no thermoplastic polyimide resin layer, making the lamination process impossible. The body cannot be manufactured, and there is a problem that the product warps before and after etching. On the other hand, when a single layer of thermoplastic polyimide resin is used, there is a problem that the rate of dimensional change after heat treatment is high due to the high coefficient of linear thermal expansion of the insulating layer, and the product warps before and after etching. . Therefore, the present invention has an effect of improving the adhesion to the metal foil and the solder resistance by making the insulating layer a multilayer structure and adjusting the moisture absorption rate of the polyimide layer.

  The first polyimide layer or the third polyimide layer according to the present invention may include 50 to 100 mol% of a polyimide resin having a structure represented by the following chemical formula 1. The polyimide resin having such a structure is a thermoplastic resin to which a metal layer can be added by a laminating process, and has a low moisture absorption rate and a high solder heat resistance after moisture absorption.

(In Chemical Formula 1, n is an integer of 1 to 100,000,000.)

  The first polyimide layer or the third polyimide layer according to the present invention may have a glass transition temperature of 200 to 400 ° C, more preferably 300 to 400 ° C. If the glass transition temperature is less than 200 ° C, it may cause a decrease in solder heat resistance after moisture absorption by thermal decomposition of the insulating layer. If it exceeds 400 ° C, a stable adhesion to the metal layer is ensured. Can not do it.

  The second polyimide layer according to the present invention may include 50 to 100 mol% of a polyimide resin including any one selected from the following chemical formulas 2 to 3 or a copolymer thereof. The polyimide resin having the structure of Chemical Formula 2 or 3 is characterized by low thermal expansion, low moisture absorption, and high solder heat resistance after moisture absorption.

(In Chemical Formulas 2 to 3, m or l are each independently an integer of 1 to 100,000,000.)

  The second polyimide layer according to the present invention may have a glass transition temperature of 300 to 500 ° C. When the glass transition temperature is less than 300 ° C., the solder heat resistance may decrease after moisture absorption of the second polyimide layer. When the glass transition temperature exceeds 500 ° C., the glass transition temperature is high, and thus during the curing process. Imidization can be difficult. The second polyimide layer may have a low coefficient of thermal expansion measured at 100 to 250 ° C. of 20 ppm / K or less, preferably 1 to 10 ppm / K.

  In the polyimide resin according to the present invention, the moisture absorption rate of the insulating layer may be 0.5 wt% or less, and the solder heat resistance temperature after moisture absorption for 72 hours at 40 ° C. and 90% relative humidity may be 350 ° C. or more.

  The production method of the polyimide resin according to the present invention is not limited, and a polyimide precursor solution can be obtained by reacting a diamine and an acid dianhydride in an organic solvent which is a production method usually used. Under an inert atmosphere such as argon or nitrogen, diamine is dissolved or diffused in a slurry state in an organic solvent, and acid dianhydride is dissolved in an organic solvent and added in a slurry state or in a solid state.

  The solvent used in the synthesis of the polyimide precursor solution is not particularly limited as long as the polyimide precursor is soluble. For example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide , Pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, diglyme, Ether solvents such as triglyme, tetraglyme, tetrahydrofuran and dioxane, alcohol solvents such as methanol, ethanol and butanol, cellosolve such as butyl cellosolve or hexamethylphosphoramide, γ-buty , Lactone and the like, it is preferable to use them alone or as a mixture, further, xylene, aromatic hydrocarbons such as toluene can be used.

  The dianhydride contained in the plurality of polyimide resin layers according to the present invention is not particularly limited as long as it is an acid dianhydride. For example, 2,2 ′ hexafluoropropylidenediphthalic dianhydride, 2, 2-bis (4-hydroxyphenyl) propanedibenzoate-3,3′4,4′tetracarboxylic dianhydride, butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride 3,5,6-tricarboxynorbornane-2-acetic acid dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxyte Lahydrofuran) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride Aliphatic or alicyclic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3′4,4′benzophenonetetracarboxylic dianhydride, 3,3′4,4′biphenylsulfonetetracarboxylic Acid dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3'4,4'biphenyl ether tetracarboxylic acid Dianhydride, 3,3′4,4′dimethyldiphenylsilanetetracarboxylic dianhydride, 3,3′4,4′tetraphenylsilanetetracarboxylic dianhydride, 1,2,3,4-fura Tetracarboxylic dianhydride, 4,4′bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4 '-Bisphenol A dianhydride, 3,3'4,4' perfluoroisopropylidenediphthalic dianhydride, 3,3'4,4'-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenyl Phosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4 ′ diphenyl ether Anhydrides, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and bis (triphenylphthalic acid) -4,4 ′ dipheny And aromatic tetracarboxylic dianhydrides such as methane dianhydride and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride.

  The diamine contained in the plurality of polyimide resin layers according to the present invention is not particularly limited. For example, p (para) -phenylenediamine, m-phenylenediamine, 4,4′diaminodiphenylmethane, 4,4′diaminodiphenylethane. 4,4′diaminodiphenyl ether, 4,4′diaminophenyl sulfide, 4,4′diaminophenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4′diaminobiphenyl, 3,5-diaminobenzoic acid Acid, 5-amino-1- (4′aminophenyl) -1,3,3-trimethylindane, 6-amino-1- (4′aminophenyl) -1,3,3-trimethylindane, 4,4 ′ Diaminobenzamide, 3,5-diamino-3′trifluoromethylbenzamide, 3,5-diamino-4 Trifluoromethylbenzamide, 3,4'diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4'methylene-bis (2-chloroaniline), 2, 2′5,5′tetrachloro-4,4′-diaminobiphenyl, 2,2′dichloro-4,4′diamino-5,5′dimethoxybiphenyl, 3,3′dimethoxy-4,4′diaminophenyl, 4 , 4′diamino-2,2′bis (trifluoromethyl) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 4,4-bis (4-aminophenoxy) -biphe 1,3-bis (4-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 4,4 ′ (p-phenyleneisopropylidene) bisaniline, 4,4 ′ (m-phenyleneisopropyl Riden) bisaniline, 4,4′-oxydianiline, 2,2′bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4′bis [4- (4 -Amino-2-trifluoromethyl) phenoxy] -octafluorophenyl and other aromatic diamines; diaminotetraphenylthiophene and other aromatic groups having two amino groups bonded to an aromatic ring and heteroatoms other than nitrogen atoms of the amino group Group diamine; 1,1-metaxylenediamine, 1,3-propanediamine, tetramethylenediamine, pen Tamethylenediamine, Octamethylenediamine, Nonamethylenediamine, 4,4-Diaminoheptanemethylenediamine, 1,4-Diaminocyclohexane, Isophoronediamine, Tetrahydrodicyclopentadienylenediamine, Hexahydro-4,7-methanoin danylylene Examples include aliphatic diamines and alicyclic diamines such as methylene diamine and 4,4 ′ methylene bis (cyclohexylamine).

  In the flexible metal-clad laminate according to the present invention, the metal foil is formed only on one side of the first polyimide layer (single-sided flexible metal-clad laminate), or formed on each side of the first polyimide layer and the third polyimide layer. (Double-sided flexible metal-clad laminate).

  The metal foil according to the present invention means a conductive metal such as copper, aluminum, silver, palladium, nickel, chromium, molybdenum and tungsten, and can include an alloy or a mixture thereof. In general, copper is widely used, but is not necessarily limited to this, a physical or chemical surface on the surface of the metal layer to increase the bond strength between the metal foil and the polyimide layer Those subjected to treatment are also included in the metal layer of the present invention.

  Examples of the coating method applicable to the present invention include knife coating, roll coating, die coating, curtain coating, and the like, which satisfy the object pursued by the present invention. As long as the method is not limited. As the coating solution, it is possible to use not only the polyimide precursor solution but also a polyimide solution in a semi-cured or fully cured state that has been pre-cured.

  The step of drying and curing the insulating layer after coating can be selectively applied, and known methods such as hot air curing method, IR curing method, batch curing method, continuous curing method and chemical curing method are known. Various methods can be applied.

  Hereinafter, the present invention will be described in detail by experimental examples. However, the present invention is not necessarily limited to these examples.

  Abbreviations used in the examples are as follows.

DMAc: N, N-dimethylacetamide (N, N-dimethylacetamide)
PMDA: Pyromellitic dianhydride
BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (3,3 ′, 4,4′-biphenyltetracarboxylic acid dianhydride)
TPE-R: 1,3-bis (4-aminophenoxy) benzene (1,3-bis (4-aminophenoxy) benzene)
p-PDA: para-phenylenediamine (p-phenylenediamine)
p-ODA: 4,4′-oxydianiline (4,4′-oxydianiline)
HFBAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane (2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane)
TFMB: 2,2-bis (trifluoromethyl) benzidine (2,2-bis (trifluoromethyl) benzidine)

  The physical properties of the test pieces manufactured according to the synthesis examples or the examples were measured as follows.

(Glass transition temperature, moisture absorption rate-synthesis example)
The polyamic acid solution produced according to Synthesis Example 1 was cast on a DFF-NA copper foil (thickness 15 μm, surface roughness Rz = 0.6 μm) manufactured by Mitsui Kinzoku so that the thickness after final curing was 20 μm. Thereafter, it was dried at 140 ° C. for 20 minutes to form a copper foil / gel film composite. The copper foil / gel film composite thus formed was heated to 380 ° C. for 60 minutes under a nitrogen atmosphere, then maintained at that temperature for 30 minutes for complete imidization, and then the copper foil was removed to obtain polyimide. A film was obtained. The test piece thus produced was used to measure the glass transition temperature and moisture absorption rate of the polyimide resin, and are shown in Table 1.

(Glass transition temperature-Examples)
Using a Mettler-Toledo DMA / SDTA861e, measurement was performed while increasing the temperature in a nitrogen atmosphere at a rate of 5 ° C. per minute from 30 ° C. to 500 ° C. under conditions of a tensile force of 0.1 N, a frequency of 10 Hz and a displacement of 30 μm . At this time, the maximum value of Tan δ obtained was defined as the glass transition temperature.

(Hygroscopic rate-Examples)
The metal foil was removed from the manufactured test piece by etching, and the remaining polyimide layer was cut into a square having a size of 5 cm × 5 cm. The cut specimen was dried in a convection oven at 150 ° C. for 1 hour or longer, and the weight after drying was measured. This was defined as the dry weight (W1). The test piece whose dry weight was measured was pretreated for 72 hours on a constant temperature and humidity chamber of 40 ° C./90% relative humidity to absorb moisture, and then the weight was measured to obtain the weight after moisture absorption (W2). Based on the measured data, calculation was performed by substituting into the following equation 1.

[Formula 1]
Moisture absorption rate (%) = (W2-W1) / W1

(Determination of solder heat resistance temperature after moisture absorption)
After producing a single-sided flexible metal-clad laminate with a metal layer formed on one side of the insulating layer, the metal layer is patterned into a square of 2.5 cm x 2.5 cm, and a size of 4 cm x 4 cm along the surrounding polyimide layer The test piece was manufactured by cutting into pieces. The manufactured test piece was pretreated for 72 hours on a constant temperature and humidity chamber of 40 ° C./90% relative humidity to absorb moisture, and then floated in a solder bath having an initial temperature of 250 ° C. It was observed whether there was any abnormality on the top. Moreover, when there was no abnormality in the external appearance at the initial temperature, the temperature of the solder bath was increased in units of 10 ° C., and it was observed whether there was a defect by the same method as described above. The highest temperature at which appearance defects such as expansion, bubbles, and layer separation do not occur is defined as the solder temperature after moisture absorption. After evaluating up to 400 ° C, when there is no abnormality at that temperature, it is expressed as 400 ° C or higher (≧ 400 ° C) did.

(Synthesis Example 1)
After TPE-R, which is a diamine, was added to DMAc, this was stirred and completely dissolved, and then equimolar BPDA was added in several portions to 100 mol% of the total diamine. Thereafter, the reaction was carried out at room temperature for 24 hours to produce a polyamic acid solution having a solid content concentration of 13% by weight and an average viscosity of 12500 cp measured at an average temperature of 23 ° C. The viscosity of the polyamic acid was adjusted by adjusting the equivalent ratio of dianhydride and diamine.

(Synthesis Examples 2 to 6)
Manufactured in the same manner as in Synthesis Example 1 except that the composition and content shown in Table 1 below were used.

Example 1
The polyamic acid solution produced by Synthesis Example 2 was cast on F2WS copper foil (thickness 12 μm, surface roughness Rz = 2.0 μm) manufactured by Furuka Circuit Foil so that the thickness after final curing was 3 μm. Then, it dried at 140 degreeC for 20 minute (s), and the 1st polyimide precursor layer was formed. Thereafter, the polyamic acid solution produced according to Synthesis Example 4 is cast on the formed first polyimide precursor layer so that the thickness after final curing is 20 μm, and then dried at 140 ° C. for 20 minutes to be second. A polyimide precursor layer was formed. In addition, the polyamic acid solution produced in Synthesis Example 2 was cast on the formed second polyimide precursor layer so that the final cured thickness would be 3 μm, and then dried at 140 ° C. for 20 minutes. Three polyimide precursor layers were formed.

  The copper foil / precursor film composite thus formed was heated to 380 ° C. for 60 minutes under a nitrogen atmosphere, and then maintained at that temperature for 30 minutes to completely imidize to complete a test piece. After moisture absorption of the completed test piece, the heat resistance temperature of the solder and the moisture absorption rate of the entire insulating layer after removal of the metal layer were measured, and the results are shown in Table 2.

(Examples 2-4 and Comparative Examples 1-2)
A test piece was manufactured in the same manner as in Example 1 except that the test piece was manufactured using the polyamic acid solution shown in Table 2. The solder heat resistance temperature after moisture absorption of the completed test piece and the moisture absorption rate of the entire insulating layer after removal of the metal layer were measured. The results are shown in Table 2.

As mentioned above, although the preferable Example of this invention is described, a various change, a change, and an equivalent may be used for this invention, and an Example can be changed suitably and can be applied similarly. It is clear. Therefore, the contents described in the examples do not limit the scope of the present invention defined by the limitations of the claims.

Claims (6)

A flexible metal-clad laminate including a metal foil and an insulating layer,
The insulating layer is
A first polyimide layer formed on one or both sides of the metal foil and having a glass transition temperature of 200 to 400 ° C .;
A second polyimide layer formed on one side of the first polyimide layer, having a glass transition temperature of 300 to 500 ° C. and a moisture absorption of 0.5 wt% or less;
A third polyimide layer formed on one side of the second polyimide layer and having a glass transition temperature of 200 to 400 ° C.,
A flexible metal-clad laminate having a heat resistant solder temperature of 350 ° C. or higher after absorbing moisture at 40 ° C. and 90% relative humidity for 72 hours. The insulating layer is
A first polyimide layer formed on one or both sides of the metal foil, having a glass transition temperature of 200 to 400 ° C. and a moisture absorption of 0.5 wt% or less;
A second polyimide layer formed on one side of the first polyimide layer, having a glass transition temperature of 300 to 500 ° C. and a moisture absorption of 0.5 wt% or less;
A third polyimide layer formed on one side of the second polyimide layer, having a glass transition temperature of 200 to 400 ° C. and a moisture absorption of 0.5 wt% or less,
The flexible metal-clad laminate according to claim 1, wherein the moisture absorption rate of the insulating layer is 0.5 wt% or less, and the solder heat resistance temperature after absorbing moisture for 72 hours at 40 ° C and 90% relative humidity is 350 ° C or more. 2. The flexible metal-clad laminate according to claim 1, wherein the first polyimide layer or the third polyimide layer contains 50 to 100 mol% of a polyimide resin having a structure of the following chemical formula 1.
(In the chemical formula 1, n is an integer of 1 to 100,000,000.) 2. The flexible metal-clad laminate according to claim 1, wherein the second polyimide layer includes 50 to 100 mol% of a polyimide resin including any one of the following chemical formulas 2 to 3 or a copolymer thereof.
(In the chemical formulas 2 to 3, m or l are each independently an integer of 1 to 100,000,000.)   The insulating layer constituting the flexible metal-clad laminate is laminated in the order of first polyimide layer / second polyimide layer / third polyimide layer / second polyimide layer / third polyimide layer, or first polyimide layer / first polyimide layer. The flexible metal-clad laminate according to claim 1, which is laminated in the order of 2 polyimide layer / third polyimide layer / first polyimide layer / second polyimide layer / third polyimide layer.   The flexible metal-clad laminate according to claim 1, wherein the first polyimide layer or the third polyimide layer has a glass transition temperature of 300 to 400 ° C.