JP2006051800A - Flexible laminated board and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible laminated board coping with mounting conditions under high temperature and high pressure while retaining characteristics possessed by the flexible laminated board. <P>SOLUTION: In the flexible laminated board having a metal foil on one surface or both surfaces of an insulating resin layer, the insulating resin layer comprises a plurality of layers of a polyimide resin provided with at least one high elastic modulus resin layer in contact with the metal foil of a polyimide resin with ≥1×10<SP>8</SP>Pa storage elastic modulus at 350°C, and at least one low thermal expansion resin layer of ≤20×10<SP>-6</SP>/K linear expansion coefficient, where the rate of thickness of the high elastic modulus layer in the insulating resin layer is in the range of 3-45%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the field of electronic materials, and more particularly to a flexible laminate comprising a metal foil and a polyimide insulating resin layer used for forming a circuit.

  The polyimide film is excellent in thermal characteristics, insulation, solvent resistance, and the like, and is widely used as a material for electrical / electronic device parts such as mobile phones. In recent years, with the progress of thinning and high functionality of mobile phones and the like, the board mounted on the device component material has shifted from a rigid board to a flexible printed board. A flexible laminate is widely used for such a flexible printed circuit board. In some flexible laminates, an adhesive resin such as an epoxy resin is used for an insulating resin layer in contact with the metal foil, and an insulating resin layer of the base portion is used. The polyimide resin is used. However, it is expected that the temperature and pressure during mounting will increase with the recent lead-free solder compatibility, shortening of semiconductor device mounting time and higher efficiency. In that case, epoxy resin is not suitable for flexible laminates using epoxy resin. Due to the low thermal characteristics such as heat resistance, it has been pointed out that it is difficult to cope with high temperature mounting.

  Therefore, as known in Patent Document 1, a flexible laminated board using a highly heat-resistant polyimide resin for an insulating resin layer in contact with a metal foil has been developed, but two layers composed of this metal foil and a polyimide resin layer. Also in a flexible laminated board, until now, it has been necessary to laminate a metal foil on an insulating resin layer, and thus a thermoplastic polyimide resin has been widely used for a polyimide resin layer in contact with the metal foil. However, even flexible laminates using thermoplastic polyimide resins known so far have excellent thermal characteristics that can withstand mounting of semiconductor elements under high temperature and high pressure conditions, and various properties as flexible laminates. The fact is that there is no one that retains the characteristics.

WO02 / 085616 Publication JP 2003-338525 A JP 2003-264374 A

  On the other hand, with the demand for miniaturization of electronic equipment, a technique for mounting a semiconductor element on a wiring board on which a circuit is formed has been developed. For example, Patent Document 2 relates to a semiconductor device and a method for manufacturing the same. However, techniques similar to the method described here, including the technique described herein, include an interposition when a semiconductor element is mounted on a wiring board via a resin. The semiconductor element is heated to a high temperature together with the sealing jig in order to cure or soften the resin component. With respect to this heating temperature, Patent Document 2 describes that heating is performed at 280 to 300 ° C. or higher, but this temperature is usually also heated to 250 ° C. or higher, although it depends on the resin properties that are present. In addition, there is a method of forming a eutectic with metals that are in contact with each other without interposing a resin. In this case, the eutectic is heated to a higher temperature. As disclosed in Patent Document 2, the mounting of the semiconductor element on the substrate is performed by heating and pressing the bumps of the semiconductor element onto the conductor layer of the wiring board under heating. In this case, the semiconductor element in contact with the conductor circuit of the laminated board is mounted. Since bumps and other protrusions are pressed against and pressed against the board at high temperatures, if the resin layer in contact with the wiring board has low heat resistance or is made of a soft material, pressure will concentrate on the connection part with the temperature. There has been a problem that a part of a circuit or a semiconductor element on the resin layer of the substrate sinks into the insulating resin layer of the substrate and cannot be stably mounted.

  The above problem may be solved if the wiring board is filled with an inorganic material, but in that case, the flexibility of the wiring board cannot be maintained, and the field where flexible laminates are used industrially. Can only be applied in different fields. Patent Document 3 describes a technique relating to a heat resistant resin composition focusing on the elastic modulus of a heat resistant resin at a high temperature (300 ° C.) and a multilayer wiring board using the same. However, Patent Document 3 states that the resin composition described therein can be used for a surface protective film of a semiconductor chip, an interlayer insulating film of a semiconductor package, an interlayer insulating film of a substrate for mounting a semiconductor element, and the like. Although described, there is insufficient study when applying to semiconductor mounting applications while actually maintaining flexible characteristics, and conventional flexible laminates are similarly designed with consideration for application to mounting applications. It wasn't.

  The present invention improves the glass transition temperature (Tg) and storage elastic modulus in the high temperature region (350 ° C.) of the polyimide resin in contact with the metal foil without impairing the adhesiveness to the metal foil, so that the high temperature mounting condition can be achieved. Another object of the present invention is to provide a flexible laminate having excellent heat resistance characteristics that can withstand the heat.

  As a result of studying to solve the above problems, the present inventors can design a flexible laminate having improved heat resistance by designing the insulating resin layer of the flexible laminate to a specific configuration. The present invention has been completed.

That is, the present invention is a flexible laminate having a metal foil on one or both sides of an insulating resin layer, the insulating resin layer is composed of a plurality of polyimide resins, and at least one polyimide resin in contact with the metal foil is 350 ° C. Is formed of a high elastic resin layer having a storage elastic modulus of 1 × 10 ⁸ to 2 × 10 ⁹ Pa and a glass transition temperature of 300 to 400 ° C., and at least one resin layer other than the high elastic resin layer Characterized by having a low thermal expansion resin layer having a linear expansion coefficient of 20 × 10 ⁻⁶ / K or less and a thickness ratio of the highly elastic resin layer in the insulating resin layer in the range of 3 to 45%. It is a flexible laminate.

  Here, 1) both sides of the low thermal expansion resin layer are high elastic resin layers, 2) a polyimide resin constituting the high elastic resin layer in contact with the metal foil is manufactured from pyromellitic dianhydride and diamine, 2,2-bis [4- (4-aminophenoxy) phenyl] propane as a diamine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene and 4,4 Use one containing 5 to 80 mol% of at least one diamine selected from '-bis (4-aminophenoxy) biphenyl, or 3) surface roughness of the metal foil surface in contact with the polyimide resin layer (Rz Satisfying one or more of the requirements in the range of 0.6 to 1.0 μm gives a better flexible laminate.

In addition, the present invention includes the following steps: 1) a storage elastic modulus at 350 ° C. of 1 × 10 ⁸ to 2 × 10 ⁹ Pa on a metal foil surface having a surface roughness (Rz) in the range of 0.6 to 1.0 μm, glass transition A step of applying a polyimide precursor resin to be a highly elastic resin layer having a temperature of 300 to 400 ° C., 2) a low thermal expansion resin layer having a linear expansion coefficient of 20 × 10 ⁻⁶ / K or less on the polyimide precursor resin layer A step of applying a polyimide precursor resin, and 3) a step of thermosetting in a state in which a plurality of polyimide precursor resin layers are provided on a metal foil, at least one layer of metal A method for producing a flexible laminate comprising a foil and at least two layers of polyimide resin.

Hereinafter, the flexible laminated board of this invention is explained in full detail.
The flexible laminated board of this invention is comprised from the insulating resin layer and metal foil, and has metal foil on the single side | surface or both surfaces of an insulating resin layer. Here, the insulating resin layer is composed of a plurality of polyimide resins, and at least one polyimide resin layer in contact with the metal foil has a storage elastic modulus at 350 ° C. of 1 × 10 ⁸ to 2 × 10 ⁹ Pa, glass It is formed of a highly elastic resin layer having a transition temperature in the range of 300 to 400 ° C. And the thickness ratio of this highly elastic resin layer in an insulating resin layer needs to exist in the range of 3-45%. Moreover, it is preferable that the highly elastic resin layer is provided adjacent to both sides of the low thermal expansion resin layer.

  For the polyimide resin used in the present invention, a known diamino compound and tetracarboxylic acid or anhydride thereof are appropriately selected, and these are combined in an organic solvent so as to meet the characteristics suitable for each layer constituting the insulating resin layer. It can be obtained by reacting in. In the present invention, a polyimide resin is mainly composed of a polyimide resin or polyamide-imide resin having an imide bond in the molecule, and is not necessarily a single polyimide resin. It may be a mixture. In the case of a mixture with other resins, the other resins should be 30% or less, preferably 20% or less. In addition, an inorganic filler may be blended if the amount is small, but these blends may impair the folding resistance and circuit processability of the flexible laminate of the present invention. In practice, the insulating resin layer is advantageously made of a polyimide resin layer.

A high elastic resin layer (hereinafter also simply referred to as a high elastic resin layer) having a storage elastic modulus at 350 ° C. of 1 × 10 ⁸ to 2 × 10 ⁹ Pa and a glass transition temperature of 300 to 400 ° C. in the present invention. The polyimide resin (hereinafter also referred to simply as “highly elastic polyimide resin”) is not limited as long as it satisfies the characteristics, but is preferably a polyimide resin having a structural unit represented by the following general formula (I). is there.

In general formula (I), Ar ₁ and Ar ₃ are divalent aromatic residues having 12 or more carbon atoms, Ar ₂ is a tetravalent aromatic residue having 6 or more carbon atoms, and k and l are k The molar ratio of each structural unit when + l = 100 is represented, k is 20 to 95, and l is a number of 80 to 5.

Here, as Ar ₁ , a divalent group represented by the formula (a) can be mentioned as a preferable one.

Moreover, as Ar ₂ , a tetravalent group represented by the formula (b) can be mentioned as a preferable one.

As Ar ₃ , any one or more of the divalent groups represented by the formulas (c) to (g) can be mentioned as preferred, and more preferably (e), (f) and (g 1) or more.

The high elastic polyimide resin needs to have a storage elastic modulus at 350 ° C. in the range of 1 × 10 ⁸ to 2 × 10 ⁹ Pa, and preferably in the range of 1 × 10 ⁸ to 1 × 10 ⁹ . If this value is less than 1 × 10 ⁸ Pa, for example, when a semiconductor element is mounted at a high temperature, the insulating resin layer in contact with the metal foil becomes fluid at the mounting temperature, and metal wiring sinks. It becomes easy to do. On the other hand, it is desirable that the storage elastic modulus of the high-elastic resin exceeds 2 × 10 ⁹ Pa from the viewpoint of the thermal characteristics at high temperatures, which is the object of the present invention, but it is flexible to develop the bending characteristics of the flexible laminate. May decrease. Further, the high elastic resin layer is required to have a glass transition temperature (Tg) in the range of 300 to 400 ° C, particularly preferably in the range of 325 to 380 ° C. If the glass transition temperature is less than 300 ° C., the metal wiring is likely to sink as described above, and the solder heat resistance of the flexible laminate is also deteriorated. If the glass transition temperature exceeds 400 ° C., good adhesion between the polyimide layer and the metal foil cannot be obtained.

The insulating resin layer of the flexible laminate of the present invention is composed of a plurality of layers, and in addition to the above highly elastic resin layer, the linear expansion coefficient is 20 × 10 ⁻⁶ / K or less, preferably 1 × 10 ⁻⁷ / K˜ It has a low thermal expansion resin layer of 20 × 10 ⁻⁶ / K. The polyimide resin constituting the low thermal expansion resin layer (hereinafter also referred to as low thermal expansion polyimide resin) is not limited as long as it satisfies the characteristics, but is preferably a structural unit represented by the following general formula (II) Is a polyimide resin.

Wherein, R _1, R ₂ represents a lower alkyl group optionally different from one another the same, q, r is the number of each 0-4. Ar ₄ is preferably one or more tetravalent groups represented by the following formulas (h) and (i). In the formula (i), X represents SO ₂ , CO, O or a direct bond.

一般式（II）又は（III）で表される構造単位は低熱膨張性ポリイミド樹脂の全ポリイミド構造単位の50モル％以上であることがよい。 Among the unit structures represented by the general formula (II), a structural unit represented by the following formula (III) is particularly preferable.

The structural unit represented by the general formula (II) or (III) is preferably 50 mol% or more of the total polyimide structural unit of the low thermal expansion polyimide resin.

  Examples of the metal foil used in the present invention include copper foil, stainless steel foil, and alloy foil. Here, the alloy foil refers to a metal foil containing a copper foil as an essential component and containing at least one element such as chromium, nickel, zinc, silicon and the like, and means a metal foil having a copper content of 90% or more. When using metal foil, surface treatment with zinc plating, nickel plating, silane coupling agent or the like may be performed.

  With the fine pitch of metal wiring, thin metal foil is preferred and used. From such a viewpoint, the preferred metal foil thickness is in the range of 5 to 35 μm, more preferably 8 to 18 μm. Moreover, it is preferable that the metal foil to be used has a surface roughness (Rz) of the surface in contact with the polyimide resin in the range of 0.6 to 1.0 μm. When the surface roughness (Rz) is less than 0.6 μm, the adhesion between the metal foil and the polyimide resin layer is not ensured. When the surface roughness is 1.0 μm or more, the transparency of the polyimide film is lowered and hinders the mounting of semiconductor elements. . In addition, by setting the surface roughness (Rz) of the metal foil within the above range, it is possible to reduce the root residue of the metal component in the polyimide resin layer generated during circuit processing. From the above, a metal foil having a surface roughness (Rz) in the above range is suitable for fine pitch metal wiring.

  The flexible laminate of the present invention has a multilayer structure in which the insulating resin layer is composed of a plurality of layers of polyimide resin, and the at least one polyimide resin layer in contact with the metal foil is the above highly elastic resin layer in a specific thickness range. A flexible laminate that can withstand high temperature and high pressure mounting conditions can be obtained. Here, by setting the thickness of the metal foil and its surface roughness (Rz) within the above ranges, the metal foil can be particularly suitable for high-density mounting applications.

In the flexible laminate of the present invention, the insulating resin layer is composed of a plurality of polyimide resins and has a multi-layer structure. Preferred layer structures include the layer structures as shown in the following 1) to 5). Here, M represents a metal foil, H represents a highly elastic polyimide resin, L represents a low thermal expansion polyimide resin, and P represents a polyimide resin other than those satisfying the storage elastic modulus or linear expansion coefficient of H or L. Show.
1) M / H / L, 2) M / H / L / H / M, 3) M / H / L / H, 4) M / H / L / P / M, 5) M / H / L / P,
The thickness ratio of H in the insulating resin layer is 3 to 45%, preferably 5 to 20%. As other polyimide resin P, when it is provided to control warpage after metal foil etching, it is preferable that the physical characteristics are similar to H, and in particular, the difference between H and the linear expansion coefficient is 10 ×. It should be within 10 ^-6 / K. In order to make a flexible laminate having metal foil on both sides of the insulating resin layer, it is advantageous to use a method in which the metal foil is later heat-pressed. In this case, polyimide resin P laminated in contact with L Is preferably a thermoplastic polyimide resin having a linear expansion coefficient of 30 × 10 ⁻⁶ / K or more.

Next, although the manufacturing method of the flexible laminated board of this invention is described, the content similar to what was already demonstrated with the flexible laminated board is only limited description.
The flexible laminate of the present invention can be a laminate in which a polyimide resin layer is laminated on one side of a metal foil by applying and drying a polyimide precursor resin on the metal foil and drying. The polyimide precursor resin applied on the metal foil is preferably in a solution state, and is usually applied in a state dissolved in an appropriate solvent. The metal foil surface to which the polyimide precursor resin is applied preferably has a surface roughness (Rz) in the range of 0.6 to 1.0 μm. In the method for producing a flexible laminate of the present invention, the polyimide precursor resin applied directly on the metal foil has a storage elastic modulus at 350 ° C. after curing of 1 × 10 ⁸ to 2 × 10 ⁹ Pa, a glass transition temperature. Becomes a highly elastic resin layer of 300 to 400 ° C. By applying the precursor resin to be the highly elastic resin layer directly on the metal foil, a stable adhesive strength of the metal-polyimide resin can be obtained. The means for applying is not particularly limited, and for example, a known method such as a barcode method, a gravure coating method, a roll coating method, or a die coating method can be appropriately selected and employed.

  The polyimide precursor resin layer applied to the metal foil is dried to an appropriate range when it contains a solvent. In this case, the drying temperature is preferably such that the imidization of the polyimide precursor resin layer does not proceed. Specifically, the drying temperature is preferably 150 ° C. or less, and preferably in the range of 110 to 140 ° C. In addition, it is desirable that the amount of the solvent contained in the polyimide precursor resin layer in this drying step is 50 parts by weight or less with respect to 100 parts by weight of the polyimide precursor resin.

The flexible laminated board of this invention has the polyimide resin layer of the low thermal expansion resin layer whose linear expansion coefficient is ^20x10 < ^-6 > / K or less other than the polyimide resin layer of the above-mentioned high elastic resin layer. The low thermal expansion resin layer is preferably formed by applying the precursor precursor layer on the polyimide precursor resin layer to be a highly elastic resin layer formed as described above. This low thermal expansion resin precursor resin is also preferably applied in a solution state, and when applied in a state containing a solvent, it is preferably dried under the same conditions as described above.

On the metal foil, a precursor resin layer that becomes a high-elasticity resin layer and a low thermal expansion resin layer is sequentially applied and dried, and then another layer of polyimide precursor resin is used to control warpage after etching the metal foil. It is desirable to provide a layer. Here, the layer to be laminated is preferably the same as the above-described highly elastic resin layer or the one having similar physical characteristics, and in particular, the difference in linear expansion coefficient from the highly elastic resin layer is 10 × 10 ⁻⁶ / K. The one within is good. In order to obtain a flexible laminate having metal foil on both sides of the insulating resin layer, it is advantageous to use a method in which the metal foil is subsequently heat-pressed. In this case, polyimide laminated on the low thermal expansion resin layer The layer is preferably a thermoplastic polyimide resin having a linear expansion coefficient of 30 × 10 ⁻⁶ / K or more. The polyimide resin layer optionally provided in the flexible laminate of the present invention can also be formed by coating and drying in the same manner as the two polyimide layer forming methods described above.

  As described above, when two or more polyimide precursor resin layers are applied and dried on the metal foil, the plurality of polyimide precursor resin layers on the metal foil are heat-treated and thermally cured. The heat treatment is preferably carried out through a plurality of curing chambers. In this case, the temperature is raised stepwise from around 150 ° C. in stages, and finally heated until reaching 250 ° C. or higher, preferably 300 ° C. or higher. Imidized. If the maximum heating temperature for imidization is too high, the resin may be decomposed. Therefore, it is desirable not to heat to a temperature 20 ° C. lower than the decomposition start temperature. Note that this heat treatment may be performed using the same apparatus following the drying step. In this step, the polyimide precursor resin is substantially imidized.

  If necessary, a metal foil is laminated on the resin layer that has been imidized. As a laminating method, a method in which a predetermined metal foil is pressed under pressure or heated between rolls is simple. The heating temperature here is preferably equal to or higher than the glass transition temperature of the polyimide resin layer in contact with the laminated metal foil. In addition, the metal foil laminated here may be the same as the metal foil described above, but when laminated by heat and pressure treatment, Rz is larger than 1.0 μm in order to maintain adhesive strength with polyimide. It is advantageous.

  The polyimide resin in contact with the metal layer of the present invention has a high Tg and a high storage elastic modulus at 350 ° C. that are not found in conventional adhesive polyimide resins, while maintaining high adhesion to the metal foil. Therefore, since the flexible laminate of the present invention has excellent heat resistance characteristics of the insulating resin layer, it can be suitably used as a COF (chip-on-film) flexible laminate for use in high-temperature mounting of semiconductor elements. it can. In addition, the flexible laminate of the present invention is composed of a plurality of insulating resin layers, and not only the thermal characteristics of the polyimide resin, which is the insulating resin layer, are high, but also required for bent portions of mobile phones and the like. Since it also has high flexibility, it can be used for small electronic devices such as mobile phones and is an industrially valuable invention.

  An embodiment of the present invention will be described below. Each physical property value of the film is measured by the following method.

1) The storage elastic modulus of glass transition temperature (Tg) and high temperature range (350 ° C) is the dynamic viscoelasticity of rheometric scientific company made from polyimide film obtained by polyimide precursor resin of each synthesis example. The dynamic viscoelasticity when the temperature was raised at 5 ° C./min was measured with a measuring device, and the Tg (maximum value of tan δ) and the storage elastic modulus at 350 ° C. were determined.

2) The coefficient of thermal expansion was measured from 100 ° C to 240 ° C during temperature reduction using a TMA100 thermomechanical analyzer manufactured by Seiko Instruments Inc. at a temperature increase rate of 20 ° C / min and a temperature decrease rate of 5 ° C / min. Obtained from change.

3) The adhesive strength with copper foil was measured by pulling the copper foil in the direction of 180 degrees at room temperature, load cell 2 kg, crosshead speed 50 mm / min, using Toyo Seiki's Strograph R-1. Asked.
Evaluation criteria were determined as follows according to adhesive strength.
○: Adhesive force 0.8 kN / m or more △: Adhesive force 0.5 kN / m or more and less than 0.8 kN / m ×: Adhesion force 0.5 kN / m or less

4) The surface roughness (Rz) of the metal foil was measured according to JIS B 0651 using a high-sensitivity surface profiler (KLA Tencor P-15) with a measurement speed of 0.02 mm / sec and a radius of curvature of 2 μm. Measured under conditions.

5) Solder heat resistance of the flexible laminate was immersed in a solder bath at a predetermined temperature for 10 seconds, and the highest temperature among the temperatures at which there was no peeling of the metal foil or swelling of the resin was defined as the solder heat resistance temperature.

Abbreviations in the examples will be described.
DMAc: N, N'-dimethylacetamide
PMDA: pyromellitic dianhydride
BPDA: 3,3'4,4'-biphenyltetracarboxylic dianhydride
DSDA: Diphenylsulfone-3,4,3 ', 4',-tetracarboxylic dianhydride
BTDA: Benzophenone-3,4,3 ', 4'-tetracarboxylic dianhydride
BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane
BAPB: 4,4'-bis (4-aminophenoxy) biphenyl
TPE-Q: 1,4-bis (4-aminophenoxy) benzene
TPE-R: 1,3-bis (4-aminophenoxy) benzene
m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl

Synthesis Examples 1 to 3
BAPP and BAPB were supplied and dissolved in DMAc, and then PMDA was supplied and stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of components having the compositions shown in Table 1.
In all synthesis examples, the ratio of the tetracarboxylic dianhydride component and the diamine component was about 100 mol% stoichiometry. Moreover, the numerical value of the resin raw material composition column in Table 1 represents a molar ratio.
Apply the resulting polyimide precursor resin solution on copper foil, dry at a temperature of 140 ° C or less until the surface of the precursor resin layer is tack-free, and then in several stages at a temperature range of 150 to 360 ° C Separately, the mixture was heated and heated to imidize to obtain a polyimide film having a thickness of 25 μm. About this polyimide film, the storage elastic modulus in 350 degreeC, the glass transition temperature (Tg), and the linear expansion coefficient were measured. The results are shown in Table 1.

Synthesis Examples 4 and 5
BAPP and TPE-Q were supplied and dissolved in DMAc, and then PMDA was supplied and stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution having the components shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis Examples 6 and 7
BAPP and TPE-R were supplied and dissolved in DMAc, then PMDA was supplied, and stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of the components shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis example 8
BAPP was supplied and dissolved in DMAc, then PMDA and DSDA were sequentially supplied, and the mixture was stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of the components shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis Example 9
BAPP was supplied and dissolved in DMAc, then PMDA and BTDA were sequentially supplied, and the mixture was stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of the components shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis Example 10
BAPP was supplied and dissolved in DMAc, and then PMDA was supplied and stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of components having the compositions shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis Example 11
BAPB was supplied and dissolved in DMAc, and then PMDA was supplied and stirred at room temperature for about 3 hours to prepare a polyimide precursor resin solution composed of components having the compositions shown in Table 1. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film, and its physical properties were evaluated. The results are shown in Table 1.

Synthesis Example 12
m-TB was supplied and dissolved in DMAc, and then PMDA was supplied, followed by stirring at room temperature for about 3 hours to prepare a polyimide precursor resin solution. This polyimide precursor resin solution was treated in the same manner as in Synthesis Example 1 to form a polyimide film. The linear expansion coefficient was measured and found to be 2.5 ppm.

The polyimide precursor resin solution prepared in Synthesis Example 1 is applied onto a copper foil having a thickness of 12 μm and a surface roughness Rz of 0.7 μm so that the thickness after curing is 6 μm and dried at less than 140 ° C. for 5 minutes. did. From this, the polyimide precursor resin solution prepared in Synthesis Example 12 was applied so that the thickness after curing was 29 μm, and dried at less than 140 ° C. for 15 minutes. Further, on the two polyimide precursor resin layers, the polyimide precursor resin solution prepared in Synthesis Example 1 was applied so that the thickness after curing was 6 μm, and dried at less than 140 ° C. for 5 minutes. It was divided into several stages in a temperature range of 150 to 360 ° C., and heated and heated stepwise over 15 minutes to obtain a flexible laminate having a copper foil on one side of the insulating resin layer.
The copper foil of the obtained flexible laminate was processed into a predetermined circuit by etching. When this flexible laminate was evaluated for adhesion to copper foil and solder heat resistance, it showed good results with adhesion to copper foil of 0.8 kN / m or higher and solder heat resistance of 400 ° C or higher. It was. The evaluation results are shown in Table 2.

Examples 2-7
In Example 1, the type of the polyimide precursor resin layer formed as the first and third high-elasticity resin layers was changed to those of Synthesis Examples 2 to 7 to produce flexible laminates. About the highly elastic resin layer surface of this flexible laminated board, adhesiveness with copper foil and solder heat resistance were evaluated. The evaluation results are shown in Table 2.

Comparative Examples 1-4
In Example 1, the type of the polyimide precursor resin layer formed as the first layer and the third layer resin layer was changed to those of Synthesis Examples 8 to 11 to produce flexible laminates. This flexible laminate was evaluated for adhesion to copper foil and solder heat resistance using the first layer of resin as an evaluation surface. The evaluation results are shown in Table 2.

Claims (4)

A flexible laminate having a metal foil on one or both sides of an insulating resin layer, the insulating resin layer comprising a plurality of polyimide resins, and at least one polyimide resin in contact with the metal foil has a storage elastic modulus at 350 ° C. of 1 × 10 ^{8 to} 2 × 10 ⁹ Pa, formed of a highly elastic resin layer having a glass transition temperature of 300 to 400 ° C. Further, as a resin layer other than the highly elastic resin layer, the linear expansion coefficient of at least one layer is 20 A flexible laminate having a low thermal expansion resin layer of × 10 ^-6 / K or less and a thickness ratio of a highly elastic resin layer in an insulating resin layer in a range of 3 to 45%.   A polyimide resin constituting a highly elastic resin layer in contact with the metal foil is produced from pyromellitic dianhydride and diamine, and 2,2-bis [4- (4-aminophenoxy) phenyl] propane as the diamine, 5 to 80 mol of at least one diamine selected from 4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene and 4,4′-bis (4-aminophenoxy) biphenyl The flexible laminate according to claim 1, wherein the one containing% is used.   The flexible laminate according to claim 1 or 2, wherein the surface roughness (Rz) of the surface of the metal foil in contact with the polyimide resin layer is in the range of 0.6 to 1.0 µm. The following process,
1) High elasticity with a storage elastic modulus of 1 × 10 ⁸ to 2 × 10 ⁹ Pa and a glass transition temperature of 300 to 400 ° C. at 350 ° C. on the surface of the metal foil having a surface roughness (Rz) of 0.6 to 1.0 μm. A step of applying a polyimide precursor resin to be a resin layer;
2) A step of applying a polyimide precursor resin to be a low thermal expansion resin layer having a linear expansion coefficient of 20 × 10 ⁻⁶ / K or less on the polyimide precursor resin layer, and 3) a plurality of layers of polyimide on the metal foil. A step of thermosetting with the precursor resin layer provided,
A method for producing a flexible laminate comprising at least one metal foil and at least two polyimide resins.