JP2019204977A - Rigid flexible substrate - Google Patents

Abstract

To solve the problem in which a crack occurs in a stepped portion of a flexible printed circuit board in a hot pressing step, a laser processing step for forming an outer layer circuit and a desmear processing step, in a manufacturing process of rigid flexible printed wiring boards.SOLUTION: A multilayer polyimide film is used in which a temperature showing a maximum value of a loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is 155°C to 185°C and the maximum value is 0.03 to 0.15.SELECTED DRAWING: None

Description

  The present invention relates to a multilayer polyimide film in which generation of cracks when immersed in a desmear liquid after hot pressing is suppressed, a flexible metal foil laminate having a multilayer polyimide resin layer and a metal foil, a method for producing a flexible metal foil laminate, and flexible The present invention relates to a method for manufacturing a rigid flexible wiring board using a metal foil laminate.

  In recent years, electronic devices have been rapidly increasing in performance, functionality, and downsizing, and accordingly, there is an increasing demand for downsizing and weight reduction of electronic components used in electronic devices. . In response to the above request, semiconductor device packaging methods and wiring boards for mounting semiconductor devices are required to have higher density, higher functionality, and higher performance.

  Among them, a rigid flexible wiring board in which a rigid substrate and a flexible substrate as shown in FIG. 1 are combined has come to be used. Since the semiconductor can be stably mounted on the rigid substrate and the flexible substrate can be bent, it is possible to achieve both high performance and downsizing of the rigid flexible wiring board.

  The rigid flexible wiring board is manufactured by a process of laminating a rigid substrate and a flexible substrate (hereinafter also referred to as a flexible metal foil laminate) in a lump by hot pressing, and a laser processing step for forming an outer layer circuit. In addition, there is a manufacturing method including a desmear process, and then a rigid flexible wiring board is manufactured through a copper plating process and an exterior circuit forming process. In the manufacture of a conventional rigid flexible wiring board, a dummy board is used to eliminate the level difference as seen in FIG. 1, thereby equalizing the pressure applied to the rigid flexible wiring board in the manufacturing process. It was possible. However, in recent years, the use of dummy boards has been omitted in order to reduce manufacturing costs. However, in the manufacturing process of such a rigid flexible printed wiring board, a step shown in FIG. 1 is obtained through a process of laminating and integrating by hot pressing, a laser processing process for forming an outer layer circuit, and a desmear process. The problem that a crack will generate | occur | produce in a location generate | occur | produces.

  Conventionally, polyimide with improved laser processability (for example, see Patent Document 1), polyimide with controlled resistance to desmear liquid (for example, see Patent Document 2), stress generated in a substrate resin in a via forming process by laser processing There has been a report on a method for producing a polyimide metal laminate (for example, see Patent Document 3) capable of preventing damage to the substrate resin caused by the above.

Japanese Patent Publication “JP 2002-144476 A (published May 21, 2002)” Japanese Patent Publication “Japanese Patent Laid-Open No. 2010-114358 (published on May 20, 2010)” Japanese Patent Publication “JP 2012-186377 A (published September 27, 2012)”

  However, the materials described in Patent Documents 1 to 3 are not sufficient to withstand the rigid flexible printed wiring board manufacturing process that undergoes the process of laminating and integrating by hot pressing as described above and the process of desmear treatment. No polyimide material has been provided so far that cracks do not occur after both steps.

  The present invention has been made in view of the above, and its purpose is to laminate and integrate a rigid substrate and a flexible substrate with a hot press and a desmear treatment step when manufacturing a rigid flexible wiring board. Is to provide a flexible metal foil laminate that does not cause cracks in the flexible substrate, and a multilayer polyimide film that is a raw material of the flexible metal foil laminate. Another object of the present invention is to provide a method for producing a flexible metal foil laminate and a method for producing a rigid flexible wiring board.

  <1> A multilayer polyimide film having at least one layer of a non-thermoplastic polyimide resin layer, wherein the multilayer polyimide film has a temperature at which the maximum value of loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is from 155 ° C. A multilayer polyimide film having a temperature of 185 ° C. and a maximum value of 0.03 to 0.15.

  <2> The multilayer polyimide film according to <1>, wherein the multilayer polyimide film has a thermoplastic polyimide film on at least one surface of the non-thermoplastic polyimide resin layer.

  <3> The temperature at which the non-thermoplastic polyimide resin layer exhibits a maximum value of loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is 155 ° C. to 185 ° C., and the maximum value is 0.00. The multilayer polyimide film according to <1> or <2>, wherein the multilayer polyimide film is from 05 to 0.15.

  <4> A flexible metal foil laminate comprising a metal foil on at least one surface of the multilayer polyimide film according to any one of <1> to <3>.

  <5> The method for producing a flexible metal foil laminate according to <4>, comprising a step of casting a polyamic acid, which is a raw material of the multilayer polyimide film, onto the metal foil. Manufacturing method of foil laminated body.

  <6> A rigid flexible substrate in which the rigid substrate and the flexible substrate are laminated and integrated by heating and pressurizing the rigid substrate and the flexible metal foil laminate together at a temperature of T ° C. A step of forming, a step of forming a rigid flexible wiring board in which an outer layer circuit is provided on the rigid flexible substrate by performing laser processing on the rigid flexible substrate, and a step of applying a desmear treatment to the rigid flexible wiring board And the flexible metal foil laminate includes a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer and a metal foil, and the multilayer Polyimide film is derived from β relaxation by dynamic viscoelasticity measurement Manufacturing of a rigid flexible wiring board characterized in that the temperature at which the maximum value of the coefficient of inelasticity is T-25 ° C to T + 5 ° C and the maximum value is 0.03 to 0.15. Method.

  The flexible metal foil laminate obtained by the present invention can suppress the generation of cracks in the process of processing the flexible metal foil laminate into a rigid flexible wiring board.

It is sectional drawing which shows an example of a rigid flexible wiring board. In an embodiment of the present invention, a sample pressed at the time of measuring crack resistance during immersion of a desmear liquid of a flexible metal foil laminate, and a sample having a laminate and a test piece derived from the flexible metal foil laminate It is sectional drawing which shows an example.

  Embodiments of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications can be made within the scope shown in the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention. In addition, all the academic literatures and patent literatures described in this specification are incorporated by reference in this specification. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more (including A and greater than A) and B or less (including B and less than B)”.

  A rigid flexible wiring board is a process of integrating a rigid substrate and a flexible substrate in a laminated state by collectively hot pressing (hereinafter also referred to as a heat pressing step), a laser processing step for forming an outer layer circuit, a desmear It is manufactured through a copper plating step and an exterior circuit forming step after a manufacturing step including a processing step. At this time, when a conventional flexible substrate was used, it was revealed that cracks occurred in the stepped portion shown in FIG. 1 in the obtained rigid flexible wiring board. Therefore, the present inventors diligently investigated which process is a cause of crack generation in the process of manufacturing a rigid flexible wiring board. First, in the step of integrating the rigid substrate and the flexible substrate in a state of being laminated by hot pressing in a lump (hot pressing step), the boundary between the rigid substrate and the flexible substrate is as shown in FIG. Since there is a step, a strong thermal strain is applied to the flexible substrate. After this, the laser processing step for forming the outer layer circuit and the desmear treatment step are combined with the reduction in the strength of the resin film used for the flexible substrate by the alkaline solution used for the desmear treatment, and the above heat I found out that cracks would occur in the strained areas. That is, it has been found that the occurrence of cracks is caused by a desmear treatment step using an alkaline solution after the hot pressing step. Therefore, a material designed to withstand the thermal strain applied to the flexible metal foil laminate during the hot pressing process is not sufficient to suppress cracks, and a material designed to withstand desmear treatment is not sufficient for cracking. It was found to be insufficient for suppression.

  Therefore, the present inventors think that it is sufficient to use a film that relieves stress in a hot pressing step in a process of manufacturing a rigid flexible wiring board as a film for use in a flexible substrate. We focused on the dynamic viscoelastic behavior. And, the film that relieves stress in the hot press process is considered that it can be achieved by a material having β dispersion near the temperature condition of the hot press process when dynamic viscoelasticity is measured. As a result of studying these materials, the present invention has been achieved.

  The multilayer polyimide film according to the present invention is a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer, and the multilayer polyimide film has a maximum value of loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement. The temperature is 155 ° C. to 185 ° C., and the maximum value of the loss elastic modulus derived from β relaxation is 0.03 to 0.15.

  As a method for confirming β relaxation, attention can be given to the relationship (temperature curve) between the loss elastic modulus (hereinafter also referred to as tan δ) based on dynamic viscoelasticity measurement and temperature. The loss elastic modulus is a ratio (storage elastic modulus / loss elastic modulus) of storage elastic modulus and loss elastic modulus obtained by dynamic viscoelasticity measurement. Specifically, the dynamic viscoelasticity measurement of the resin sample is performed by defining the frequency of the applied stress and the temperature rising rate, and the value of tan δ is plotted against the temperature. When β relaxation occurs, tan δ increases and shows a maximum value. Thereby, β relaxation can be confirmed. In the present invention, dynamic viscoelasticity measurement is performed under the measurement conditions of a frequency of 5 Hz and a temperature increase rate of 3 ° C./min.

  The multilayer polyimide film in the present invention is set so that the temperature at which the maximum value of tan δ derived from β relaxation (hereinafter also referred to as the maximum temperature) is in the range of 155 ° C to 185 ° C. The reason for setting in this way is that the maximum temperature of tan δ derived from β relaxation is within this temperature range, assuming that the temperature often used in the hot press process when manufacturing a rigid flexible wiring board is around 180 ° C. This is because it was considered that the stress could be relaxed. If the maximum temperature deviates from the above temperature range, the temperature region where β relaxation occurs deviates from the temperature of the hot press process, and there is a possibility that sufficient thermal strain is not removed during the hot press process. Accordingly, β relaxation is controlled to set the maximum temperature within the above temperature range. Preferably, the maximum temperature of tan δ derived from β relaxation is in the range of 160 ° C to 170 ° C. Within this range, the amount of stress relaxation is greater than the stress during the hot press process, enabling a hot press process at a higher pressure and lower temperature, and a process window in the hot press process. Is wide and preferable. Furthermore, the maximum value is in the range of 0.03 to 0.15, preferably 0.04 to 0.12. When the maximum value of tan δ derived from β relaxation is smaller than the above range, sufficient thermal strain may not be relaxed during hot pressing. Conversely, when larger than the said range, the relaxation effect of a thermal strain is too strong and there exists a possibility that the dimensional stability and flatness of a flexible metal foil laminated body may deteriorate. The temperature range showing the maximum value of tan δ and the maximum value can be controlled by molecular design of polyimide as described later. In the case of the flexible metal foil laminate described later, the dynamic viscoelasticity measurement of the multilayer polyimide film obtained by etching the metal foil is performed, and the maximum value of tan δ derived from β relaxation and the temperature thereof are measured. Is possible. Further, by physically or chemically removing the multilayer polyimide film other than the non-thermoplastic polyimide resin layer, the temperature range showing the maximum value of tan δ of the non-thermoplastic polyimide resin layer and the maximum value thereof can be measured. .

  The multilayer polyimide film and the flexible metal foil laminate according to the present invention have a resin layer that expresses the above β relaxation, and thus are laminated and integrated in a hot pressing process when manufacturing a rigid flexible wiring board. At the same time, it is possible to remove thermal strain.

  Although the temperature of the said hot press is not specifically limited, 170 degreeC or more and 190 degrees C or less (or 170 degreeC or more and less than 190 degreeC) may be sufficient, and 175 degreeC or more and 190 degrees C or less (or 175 degreeC or more and less than 190 degreeC) ), 180 ° C. or higher and 190 ° C. or lower (or 180 ° C. or higher and lower than 190 ° C.), 180 ° C. or higher and 185 ° C. or lower, or 180 ° C. Good. The multilayer polyimide film and flexible metal foil laminate according to the present invention can be intended for use in the hot press described above.

  The multilayer polyimide film according to the present invention has at least one non-thermoplastic polyimide resin layer. The polyimide here is a polyamic acid produced by polymerizing aromatic diamine (hereinafter also referred to as diamine) and aromatic tetracarboxylic dianhydride (hereinafter also referred to as acid dianhydride) by a conventionally known method. The polyamic acid is obtained by imidization.

  In the present invention, the temperature at which the multilayer polyimide film has a maximum value of the loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is 155 ° C. to 185 ° C., and the maximum value is 0.03 to 0.00. The temperature at which the non-thermoplastic polyimide resin layer contained in the multilayer polyimide film further exhibits a maximum value of the loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is 155 ° C to 185 ° C. It is preferable that the maximum value is 0.05 to 0.15 because it is easy to control β dispersion of the entire multilayer polyimide film to a target value.

  Although it does not specifically limit about the diamine used for manufacture of a non-thermoplastic polyimide resin layer, Since the polyimide finally obtained needs to express beta relaxation, at least 1 type of diamine which is easy to express beta relaxation is used. It is preferable to use it. Since it depends on the structure of the acid dianhydride, a diamine that exhibits β relaxation cannot be uniquely determined. However, a biphenyl skeleton containing an alkyl group or a diamine having a phenyl skeleton, that is, an alkyl group-containing diaminobiphenyl component When a diamine containing is used, the resulting polyimide tends to exhibit β relaxation. Specifically, as the diamine, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-3,3′-dimethylbiphenyl, 4,4′-diamino-3,3′- Examples include hydroxybiphenyl, 1,4-diaminobenzene, 1,3-diaminobenzene, 4,4′-bis (4-aminophenoxy) biphenyl, and 4,4′-diamino-2,2′-dimethylbiphenyl. Particularly preferred. In order to control various properties such as mechanical strength, a diamine other than the above can be used as a part of the raw material as long as the finally obtained polyimide exhibits β relaxation. Specific examples of diamines other than the above include 4,4′-diaminodiphenyl ether, 2,2-bis {4- (4-aminophenoxy) phenyl} propane, 1,3-bis (4-aminophenoxy) benzene, 1 , 4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, and the like.

  The acid dianhydride is not particularly limited, but it is preferable to use at least one acid dianhydride that easily exhibits β relaxation. Although it depends on the structure of the diamine, the acid dianhydride also tends to exhibit β relaxation when an acid dianhydride having a biphenyl skeleton or a phenyl skeleton is used. Specific examples of the structure include 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and the like. As for the acid dianhydride, it is possible to use an acid dianhydride other than the above as a part of the raw material as long as the finally obtained polyimide exhibits β relaxation. Specific examples include 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, and the like.

  More specifically, in the multilayer polyimide film of the present invention, the non-thermoplastic polyimide resin layer is preferably composed of an acid dianhydride and a diamine containing an alkyl group-containing diaminobiphenyl component. Furthermore, in the multilayer polyimide film of the present invention, the diamine containing an alkyl group-containing diaminobiphenyl component is preferably 4,4'-diamino-2,2'-dimethylbiphenyl.

  The polyamic acid which is a precursor of polyimide is obtained by mixing and reacting diamine and acid dianhydride in an organic solvent so as to be substantially equimolar. Any organic solvent may be used as long as it dissolves polyamic acid, but amide solvents, that is, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, etc. N, N-dimethylformamide and N, N-dimethylacetamide can be used particularly preferably. The solid content concentration of the polyamic acid is not particularly limited, and a polyamic acid having sufficient mechanical strength when obtained as a polyimide can be obtained as long as it is within the range of 5 wt% to 35 wt%.

  The order of addition of the raw material diamine and acid dianhydride is not particularly limited, but it is possible to control the properties of the resulting polyimide by controlling not only the chemical structure of the raw material but also the order of addition. . In particular, in the present invention, since polyimide that exhibits β relaxation is essential, it is preferable to set the addition order so that a diamine that easily exhibits β relaxation and an acid dianhydride react preferentially. For example, a method of reacting diamine and acid dianhydride that are likely to exhibit β relaxation first, and then adding and reacting at least one of diamine and acid dianhydride for adjusting various properties, or various Examples include a method in which a diamine for adjusting properties and an acid dianhydride are reacted in advance, and then a diamine and an acid dianhydride that easily develop β relaxation are added and reacted.

  In addition, when 1,4-diaminobenzene and pyromellitic dianhydride are used as raw materials, the polyimide structure obtained by combining both has low durability against desmear liquid, so both are directly adjusted by adjusting the order of addition. It is preferred not to form a bonded structure.

  A filler may be added to the polyamic acid for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

  In addition, the polyamic acid is mixed with a thermosetting resin such as an epoxy resin or a phenoxy resin, or a thermoplastic resin such as polyether ketone or polyether ether ketone, as long as the properties of the resulting resin layer as a whole are not impaired. May be. Examples of a method for adding these resins include a method in which the resin is added to the polyamic acid if the resin is soluble in a solvent. If the polyimide is also soluble in the solvent, the resin may be added to the polyimide solution. If the resin is insoluble in a solvent, there may be mentioned a method in which the polyamic acid is first imidized and then the polyimide and the resin are combined by melt kneading. However, since the solder heat resistance and the heat shrinkage rate of the obtained flexible metal foil laminate may be deteriorated, it is desirable not to use a meltable polyimide in the present invention. Therefore, it is desirable to use a resin that is soluble with the polyimide.

  The multilayer polyimide film of the present invention preferably has a thermoplastic polyimide film on at least one surface of the non-thermoplastic polyimide resin layer. The aromatic diamine and aromatic tetracarboxylic dianhydride used for the thermoplastic polyimide film are the same as those used for the non-thermoplastic polyimide resin layer, but to make a thermoplastic polyimide film. It is preferable to react a flexible diamine with an acid dianhydride. Examples of flexible diamines include 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis (4-aminophenoxyphenyl) ) Propane and the like. Examples of acid dianhydrides that can be suitably combined with these diamines include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4, 4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, etc. are mentioned.

To obtain the multilayer polyimide film of the present invention, the following steps:
i) a step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution;
ii) casting a film-forming dope containing the polyamic acid solution on a support to form a resin layer;
iii) a step of peeling the gel film from the support after heating the resin layer on the support;
iv) further heating the gel film to imidize and dry the remaining amic acid, and
It is preferable to contain.
ii) Subsequent steps are roughly classified into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is used as a film-forming dope without using a dehydrating ring-closing agent or the like, and imidation is advanced only by heating and heating. One chemical imidization method is a method in which imidization is promoted by using a polyamic acid solution to which at least one of a dehydrating cyclization agent and a catalyst is added as an imidization accelerator as a film-forming dope. Either the thermal imidization method or the chemical imidization method may be used, but the chemical imidization method is superior in productivity.

  As the dehydrating ring-closing agent, acid anhydrides typified by acetic anhydride can be suitably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be suitably used.

  As the support for casting the film-forming dope, a glass plate, aluminum foil, endless stainless steel belt, stainless steel drum or the like can be suitably used. From the support after setting the heating conditions of the film-forming dope according to the thickness of the film finally obtained, the production rate, and performing at least one of imidization and drying partially on the film-forming dope It peels and a polyamic acid film (henceforth a gel film or a gel film) is obtained.

  Fix the end of the gel film and dry while avoiding shrinkage during curing, remove water, residual solvent, imidization accelerator from the gel film, and completely imidize the remaining amic acid, A film containing polyimide is obtained. About a heating condition, what is necessary is just to set suitably according to the thickness and production rate of the film finally obtained.

  In the present invention, as a method of providing a plurality of polyimide layers, a plurality of resin layers may be formed simultaneously using a co-extrusion die having a plurality of flow paths in the step ii), or the above i) to iv. ) After proceeding to the process and collecting the non-thermoplastic polyimide resin layer once, a new resin layer may be formed thereon by coating or the like. For example, when a multilayer polyimide film having a thermoplastic polyimide film on at least one surface of a non-thermoplastic polyimide resin layer is obtained, a non-thermoplastic polyimide precursor and a thermoplastic polyimide precursor are coextruded using a die. It can be obtained by casting on a support and carrying out the steps after iii). Since a very high temperature is required for imidization, when the resin layer other than polyimide is provided, it is preferable to take the latter means in order to suppress thermal decomposition. In addition, when providing a thermoplastic polyimide film by coating, a precursor of a thermoplastic polyimide may be applied on a non-thermoplastic polyimide film and then imidized, or a thermoplastic polyimide solution may be applied to a non-thermoplastic polyimide film. You may apply | coat and dry on a film.

  Moreover, a thermoplastic polyimide film may be obtained by casting a polyimide solution and cooling it instead of casting a polyamic acid solution on a support in the above-described steps.

The flexible metal foil laminate according to the present invention is composed of a multilayer polyimide film and a metal foil. As a means of forming a multilayer polyimide film on a metal foil,
a) Means (thermal laminating method) for obtaining a flexible metal foil laminate by bonding a metal foil to the multilayer polyimide film by heating and pressing after obtaining the multilayer polyimide film as described above,
b) Casting an organic solvent solution containing polyamic acid on the metal foil, and heating to remove the solvent from the organic solvent solution and imidize to obtain a flexible metal foil laminate (casting method),
c) On the metal foil, a means for obtaining a flexible metal foil laminate by casting a melt containing polyimide and cooling the melt (casting method),
Is mentioned.

  When the means a) or b) is used, the flexible metal foil laminate is produced by a production method having a step of casting polyamic acid, which is a raw material for the multilayer polyimide film, on the metal foil. In this case, the polyamic acid that is a raw material of the multilayer polyimide film cast on the metal foil may be (i) only a non-thermoplastic polyamic acid for forming a non-thermoplastic polyimide resin layer, or (ii) ) It may be only a thermoplastic polyamic acid for forming a thermoplastic polyimide film, or (iii) a non-thermoplastic polyamic acid and a thermoplastic polyimide film for forming a non-thermoplastic polyimide resin layer. Both of these thermoplastic polyamic acids may be used.

  Among these, if the polyimide is made meltable, the heat resistance and the heat shrinkage rate of the obtained flexible metal foil laminate may be deteriorated. Therefore, it is preferable to use the means a) or b). If the polyimide is solvent-soluble, an organic solvent solution containing polyimide may be used instead of the organic solvent solution containing polyamic acid. Details of a) and b) will be described below.

  In the means a), the flexible metal foil laminate of the present invention is obtained by laminating a metal foil to the obtained multilayer polyimide film by heating and pressing. The means and conditions for bonding the metal foil may be appropriately selected from conventionally known ones.

  In the means of b), the means for casting the organic solvent solution containing polyamic acid on the metal foil is not particularly limited, and conventionally known techniques such as a die coater, comma coater (registered trademark), reverse coater, knife coater, etc. Means can be used. Conventionally known means can be used as the heating means for removing the solvent and imidizing, and examples thereof include a hot air furnace and a far infrared furnace.

  Similarly to the means a), the heating time can be shortened by the chemical imidization method, and the productivity can be improved. However, since an acid is generated from an acid anhydride, which is a dehydrating ring-closing agent, in the imidization process, oxidation may proceed depending on the type of the metal foil. The addition of the dehydrating ring-closing agent is preferably selected as appropriate according to the type of metal foil and heating conditions.

  When a polyimide layer is provided in multiple layers, or when a resin layer other than polyimide is also provided, the above casting and heating steps are repeated multiple times, or the cast layer is formed once by co-extrusion or continuous casting. A means for heating to the above can be suitably used.

  By means of b), the immobilization is completed and the flexible metal foil laminate of the present invention is obtained at the same time. When providing a metal foil layer on both surfaces of the resin layer, the metal foil may be bonded to the surface of the resin layer opposite to the surface on which the metal foil layer is already provided by heating and pressing.

  The total thickness of the multilayer polyimide film according to the present invention is preferably 7 μm to 60 μm. Even within that range, it is preferable that the thickness is small, since the bendability of the rigid flexible wiring board is improved. However, if the thickness is less than 7 μm, handling during processing may be difficult. When the thickness exceeds 60 μm, the bendability when a rigid flexible wiring board is obtained may be lowered.

  Although it does not specifically limit as metal foil which can be used in this invention, When using the flexible metal-clad laminated board of this invention for an electronic device and an electric equipment use, for example, copper or copper alloy, stainless steel Or the foil which consists of the alloy, nickel or a nickel alloy (a 42 alloy is also included), aluminum, or an aluminum alloy can be mentioned. In general flexible laminates, copper foil such as rolled copper foil and electrolytic copper foil is frequently used, but it can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil. Moreover, it does not specifically limit about the thickness of the said metal foil, According to the use, what is necessary is just the thickness which can exhibit a sufficient function.

(Rigid flexible wiring board manufacturing method)
By using the flexible metal foil laminate according to the present invention as a flexible substrate and combining the flexible substrate and a rigid substrate such as a glass epoxy substrate, a rigid flexible wiring board is obtained. In the flexible metal foil laminate of the present invention, the maximum temperature of tan δ derived from β relaxation of the laminated polyimide film or the non-thermoplastic polyimide resin layer is controlled within the range of 155 ° C. to 185 ° C. The effect of mitigating thermal strain is exhibited within the temperature range of the process. Furthermore, in order to effectively exhibit this thermal strain mitigating effect, the temperature of the hot press (T ° C), which is a process of laminating and integrating the rigid substrate and the flexible substrate together by heating and pressing, contains polyimide. It is preferable that the tan δ derived from β relaxation of the resin layer be equal to or higher than the temperature at which the maximum value is obtained. By performing hot pressing at a temperature at which the tan δ derived from β relaxation is at or above the maximum value, the effect of relaxing the thermal strain applied to the material during pressing acts particularly effectively, and the effect of suppressing the occurrence of cracks in the desmear process is enhanced. . However, if the temperature of the hot press process is too high, it will be out of the temperature range that exhibits β relaxation, so it is preferable to keep it at + 20 ° C. or lower than the temperature that shows the maximum value.

  More specifically, in the method for manufacturing a rigid flexible wiring board according to the present embodiment, a rigid substrate and a flexible metal foil laminate (in other words, a flexible substrate) are heated together under a temperature condition of T ° C. And pressurizing to form a rigid flexible substrate in which the rigid substrate and the flexible substrate are laminated and integrated, and applying laser processing to the rigid flexible substrate to provide an outer layer circuit on the rigid flexible substrate. Forming the rigid flexible wiring board and applying a desmear treatment to the rigid flexible wiring board. At this time, the flexible metal foil laminate (in other words, the flexible substrate) can include a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer and a metal foil. Furthermore, the temperature at which the multilayer polyimide film exhibits a maximum value of the loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is T-25 ° C to T + 5 ° C (more preferably T-10 ° C to T ° C). In addition, the maximum value may be 0.03 to 0.15 (more preferably 0.04 to 0.12).

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In addition, the loss elastic modulus (tan-delta) in the dynamic viscoelasticity measurement of the polyimide in a synthesis example, an Example, and a comparative example and the crack resistance evaluation method at the time of desmear liquid immersion of a flexible metal foil laminated body are as follows.

(Dynamic viscoelasticity measurement)
The dynamic viscoelasticity was measured in an air atmosphere using DMS6100 manufactured by SII Nanotechnology, and a graph in which the loss elastic modulus (tan δ) was plotted against the measurement temperature was created. The tan δ maximization near the temperature at which the storage modulus rapidly decreases is considered to be due to α relaxation, and the tan δ maximization at lower temperatures is due to β relaxation, based on the maximization due to β relaxation, The maximum temperature and the maximum value were read. For polyimides that did not exhibit α relaxation, the observed maximization of tan δ was considered to be due to β relaxation.

・ Sample measurement range: width 9mm, distance between grips 20mm
・ Measurement temperature range: 0 ℃ ～ 440 ℃
・ Temperature increase rate: 3 ° C./min ・ Strain amplitude: 10 μm
・ Measurement frequency: 5Hz
・ Minimum tension / compression force: 100mN
・ Tension / compression gain: 1.5
-Initial value of force amplitude: 100mN
(Evaluation of crack resistance when desmear liquid is immersed in flexible metal foil laminate)
A laminate having a size of 20 cm in the longitudinal direction and 25 cm in the width direction was cut from the flexible metal foil laminate obtained in the examples and comparative examples. The metal foil layer on one side of the cut laminate was etched to form a pattern having a wiring width of 250 μm and a wiring interval of 250 μm. All the metal foils on the non-patterned side were removed by etching. A test piece having a length of 10 cm and a width of 1.5 cm was cut out from the laminate, with the direction parallel to the wiring as the longitudinal direction. As shown in FIG. 2, the test piece was sandwiched between laminated materials and subjected to hot pressing (first time) for 60 minutes under the conditions of 180 ° C. and 3.8 kgf / cm ² .

Separately, a 10 cm × 12 cm glass epoxy substrate (FR4 substrate: thickness 0.4 mm) was used as a rigid substrate, and the central portion thereof was cut out so as to form a 1 cm × 10 cm opening. Then, double-sided tape was affixed to the remaining edge portion. The test piece is placed on the opening of the FR4 substrate so that the end of the test piece after the hot pressing is overlapped with the double-sided tape, and the rigid substrate and the flexible substrate are batched under the conditions of 180 ° C. and 30 kgf / cm ^2. Heating and pressurization (hot pressing step (second time)) were performed for a minute.

  After the second hot pressing process, the test piece was peeled off from the FR4 substrate, and the test piece was dessed in a swelling liquid maintained at 50 ° C. (Securigant P, manufactured by Atotech) for 90 seconds at 65 ° C. The film was sequentially immersed in a neutralizing solution (securigant P500, manufactured by Atotech) for 40 seconds in a securigant P500 P-Etch (manufactured by Atotech) under a condition of 40 seconds. After immersion, the test piece was washed with water and then dried at 60 ° C. for 10 minutes.

  About the test piece after drying, the location which overlapped with FR4 board | substrate at the time of the 2nd heat press was observed with the optical microscope, and the presence or absence of the generation | occurrence | production of a crack was confirmed. In crack resistance, “◎” indicates that no crack is observed, “◯” indicates that a crack is confirmed but the crack size (longitudinal direction) is less than 1 μm, and crack is confirmed and crack size (longitudinal direction). ) Of 1 μm or more was designated as “x”. In addition, the crack (cracking, tearing) confirmed using the optical microscope was determined to be a crack regardless of its size. The magnification of the optical microscope was set to an optimum magnification for judging a portion that seems to be a crack.

(Synthesis Example 1)
With the inside of the reaction system kept at 20 ° C., 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter referred to as “DMF”) was added to 159.4 kg of N, N-dimethylformamide (hereinafter also referred to as “DMF”). 17.7 kg (also referred to as BPDA) was added, and 6.1 kg of 1,4-diaminobenzene (hereinafter also referred to as p-PDA) was gradually added while stirring under a nitrogen atmosphere. After visually confirming that BPDA and p-PDA were dissolved, stirring was performed for 30 minutes. Subsequently, 2.1 kg of 4,4′-oxyphthalic dianhydride (hereinafter also referred to as ODPA) was added and stirring was continued. After visually confirming that ODPA was dissolved, 2,2′-bis {4 -(4-Aminophenoxy) phenyl} propane (hereinafter also referred to as BAPP) 3.3 kg was added and stirred for 30 minutes.

  Finally, a solution prepared by dissolving 0.8 kg of BAPP in DMF so as to have a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.8) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 2)
While maintaining the reaction system at 20 ° C., 16.0 kg of BPDA was added to 164.7 kg of DMF, and 2.8 kg of BAPP and 4.8 kg of p-PDA were gradually added while stirring in a nitrogen atmosphere. After visually confirming that BPDA, BAPP, and p-PDA were dissolved, stirring was performed for 30 minutes. Subsequently, 3.0 kg of pyromellitic dianhydride (hereinafter also referred to as PMDA) was added and stirring was continued. After visually confirming that PMDA was dissolved, 4,4′-diaminodiphenyl ether (hereinafter also referred to as ODA). 3.0 kg) was added and stirred for 30 minutes.

  Finally, a solution in which 0.4 kg of ODA is dissolved in DMF to a solid content concentration of 7% is prepared, and this solution is gradually added to the reaction solution while paying attention to increase in viscosity, and the viscosity is 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.7) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 3)
While maintaining the reaction system at 20 ° C., 13.8 kg of 4,4′-diamino-2,2′-dimethylbiphenyl (hereinafter also referred to as m-TB) was added to 164.5 kg of DMF, and under a nitrogen atmosphere. Stirring was performed. After visually confirming dissolution of m-TB, 7.7 kg of BPDA and 8.1 kg of PMDA were added and stirring was continued. After visually confirming that BPDA and PMDA were dissolved, stirring was performed for 30 minutes. .

  Finally, a solution in which 0.4 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 3.0) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 4)
With the reaction system kept at 20 ° C., 14.3 kg of m-TB was added to 164.3 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming dissolution of m-TB, 4.0 kg of BPDA and 11.3 kg of PMDA were added and stirring was continued. After visually confirming that BPDA and PMDA were dissolved, stirring was performed for 30 minutes. .

  Finally, a solution in which 0.4 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.8) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 5)
While maintaining the reaction system at 20 ° C., 12.0 kg of m-TB was added to 167.6 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming the dissolution of m-TB, 17.9 kg of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA) was added and stirring was continued, and BTDA was dissolved. After visually confirming that this was done, stirring was performed for 30 minutes.

  Finally, a solution in which 0.2 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to the increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 3.8) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 6)
With the reaction system maintained at 20 ° C., 8.8 kg of PDA and 4.5 kg of m-TB were added to 162.5 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming dissolution of PDA and m-TB, 9.79 kg of BPDA and 10.61 kg of PMDA were added and stirring was continued. After visually confirming that BPDA and PMDA were dissolved, stirring was performed for 30 minutes.

  Finally, a solution in which 0.4 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.9) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T-die, and cast on a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 7)
With the reaction system kept at 20 ° C., 2.6 kg of ODA and 8.1 kg of BAPP were added to 164.5 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming dissolution of ODA and BAPP, 4.2 kg of BTDA and 3.6 kg of PMDA were added and stirring was continued. After visually confirming that BTDA and PMDA were dissolved, stirring was performed for 30 minutes. It was.

  Subsequently, 3.6 kg of p-PDA was added and stirring was continued. After visually confirming dissolution, 7.5 kg of PMDA was added, and after visually confirming that PMDA was dissolved, stirring was performed for 30 minutes.

  Finally, a solution in which 0.4 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.9) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 8)
While maintaining the reaction system at 20 ° C., 4.0 kg of p-PDA was added to 163.7 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming the dissolution of p-PDA, 7.3 kg of PMDA was added and stirring was continued. After visually confirming that PMDA was dissolved, stirring was performed for 30 minutes.

  Subsequently, 7.5 kg of ODA was added and stirring was continued. After visually confirming dissolution, 8.8 kg of BPDA and 2.0 kg of PMDA were added, and after visually confirming that BPDA and PMDA were dissolved, Stirring was performed for 30 minutes.

  Finally, a solution in which 0.5 kg of PMDA is dissolved in DMF so as to have a solid content concentration of 7% is prepared, and this solution is gradually added to the above reaction solution while paying attention to increase in viscosity. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.2) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 9)
While maintaining the reaction system at 20 ° C., 4.3 kg of m-TB and 5.5 kg of BAPP were added to 163.4 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming dissolution of m-TB and BAPP, 7.9 kg of BPDA was added and stirring was continued. After visually confirming that BPDA was dissolved, stirring was performed for 30 minutes.

  Subsequently, 3.6 kg of p-PDA was added and stirring was continued. After visually confirming dissolution, 8.3 kg of PMDA was added, and after visually confirming that PMDA was dissolved, stirring was performed for 30 minutes.

  Finally, a solution in which 0.5 kg of PMDA is dissolved in DMF so as to have a solid content concentration of 7% is prepared, and this solution is gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity is 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.6 / 2.8) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip, and dried and imidized at 250 ° C. × 15 seconds, 350 ° C. × 87 seconds, A polyimide film having a thickness of 12.5 μm was obtained.

(Synthesis Example 10)
With the reaction system kept at 20 ° C., 5.62 kg of PDA was added to 165.8 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming dissolution of PDA, 9.91 kg of BPDA and 2.15 kg of BTDA were added and stirring was continued. After visually confirming that BPDA and BTDA were dissolved, stirring was performed for 30 minutes.

  Subsequently, 4.46 kg of ODA was added and stirring was continued. After visually confirming dissolution, 5.66 kg of PMDA was added, and after visually confirming that PMDA was dissolved, stirring was performed for 30 minutes.

  Finally, a solution in which 0.5 kg of PMDA is dissolved in DMF so as to have a solid content concentration of 7% is prepared, and this solution is gradually added to the above reaction solution while paying attention to increase in viscosity, and the viscosity is 3000 poise. The polymerization was terminated when the value reached.

(Synthesis Example 11)
With the reaction system kept at 20 ° C., 21.8 kg of BAPP was added to 161.5 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming the dissolution of BAPP, 2.3 kg of BPDA and 9.5 kg of PMDA were added and stirring was continued. After visually confirming that BPDA and PMDA were dissolved, stirring was performed for 30 minutes.

  Finally, a solution in which 0.4 kg of PMDA was dissolved in DMF to a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to increase in viscosity. The polymerization was terminated when the value reached.

Example 1
The polyamic acid solution obtained in Synthesis Example 11 was applied to both sides of the polyimide film obtained in Synthesis Example 1 so that the final thickness per side was 3.0 μm, and dried at 140 ° C. for 2 minutes. Subsequently, imidization was performed by heating at 350 ° C. for 1 minute to obtain a laminated polyimide film having a total thickness of 18.5 μm.

  An electrolytic copper foil (3EC-M3S-HTE, manufactured by Mitsui Metals) having a thickness of 12.5 μm is disposed on both surfaces of the obtained laminated polyimide film, and a protective film (Apical 125 NPI) is provided on the outside of both electrolytic copper foils. A flexible metal foil laminate from the outside of the protective film, with a laminating temperature of 360 ° C., a laminating pressure of 265 N / cm (27 kgf / cm), and a laminating speed of 1.0 m / min. Was made.

(Example 2)
A bar coater with the polyamic acid solution obtained in Synthesis Example 11 on a 12.5 μm thick electrolytic copper foil (3EC-M3S-HTE, manufactured by Mitsui Metals) as a metal foil so that the final thickness after imidization is 3 μm. And dried at 120 ° C. for 2 minutes. Further, the polyamic acid solution obtained in Synthesis Example 1 was applied from above the dried polyamic acid solution using a bar coater so that the thickness after imidization was 12.5 μm, and dried at 130 ° C. for 5 minutes. Furthermore, the polyamic acid solution obtained in Synthesis Example 11 was applied onto the dried polyamic acid solution using a bar coater so that the final thickness after imidization was 3 μm, and dried at 120 ° C. for 2 minutes. The temperature was raised to 350 ° C. over a period of time to complete imidization to obtain a single-sided flexible metal foil laminate. An electrolytic copper foil having a thickness of 12.5 μm (3EC-M3S-HTE, manufactured by Mitsui Metals) is disposed on the surface of the single-sided flexible metal foil without the electrolytic copper foil, and a protective film (Apical 125 NPI; From the outside of the protective film, heat lamination is performed under conditions of a laminating temperature of 360 ° C., a laminating pressure of 265 N / cm (27 kgf / cm), and a laminating speed of 1.0 m / min. Was made.

Example 3
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 2 was used instead of the polyimide film obtained in Synthesis Example 1.

Example 4
A flexible metal foil laminate was produced in the same manner as in Example 2 except that the polyamic acid obtained in Synthesis Example 2 was used instead of the polyamic acid obtained in Synthesis Example 1.

(Example 5)
A flexible metal foil laminate was prepared in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 3 was used instead of the polyimide film obtained in Synthesis Example 1.

(Example 6)
A flexible metal foil laminate was produced in the same manner as in Example 2 except that the polyamic acid obtained in Synthesis Example 3 was used instead of the polyamic acid obtained in Synthesis Example 1.

(Example 7)
A flexible metal foil laminate was prepared in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 4 was used instead of the polyimide film obtained in Synthesis Example 1.

(Example 8)
A flexible metal foil laminate was produced in the same manner as in Example 2 except that the polyamic acid obtained in Synthesis Example 4 was used instead of the polyamic acid obtained in Synthesis Example 1.

Example 9
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 5 was used instead of the polyimide film obtained in Synthesis Example 1.

(Example 10)
A flexible metal foil laminate was produced in the same manner as in Example 2 except that the polyamic acid obtained in Synthesis Example 5 was used instead of the polyamic acid obtained in Synthesis Example 1.

(Example 11)
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 6 was used instead of the polyimide film obtained in Synthesis Example 1.

(Example 12)
A flexible metal foil laminate was produced in the same manner as in Example 2 except that the polyamic acid obtained in Synthesis Example 6 was used instead of the polyamic acid obtained in Synthesis Example 1.

(Comparative Example 1)
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 7 was used instead of the polyimide film obtained in Synthesis Example 1.

(Comparative Example 2)
A flexible metal foil laminate was prepared in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 8 was used instead of the polyimide film obtained in Synthesis Example 1.

(Comparative Example 3)
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 9 was used instead of the polyimide film obtained in Synthesis Example 1.

(Comparative Example 4)
Instead of the polyimide film obtained in Synthesis Example 1, a flexible metal foil laminate was produced by performing the same operation as in Example 1 except that a polyimide film having a thickness of 12.5 μm (Apical NPI, manufactured by Kaneka Corporation) was used. .

(Comparative Example 5)
A flexible metal foil laminate was produced in the same manner as in Example 1 except that the polyimide film obtained in Synthesis Example 10 was used instead of the polyimide film obtained in Synthesis Example 1.

(Reference Example 1)
The same operation as in Comparative Example 1 was performed to produce a flexible metal foil laminate. At the time of evaluation of crack resistance, the cut test piece was immersed in the evaluation solution as it was without passing through the two hot pressing steps.

  Table 1 shows the maximum temperature and maximum value of tan δ derived from β relaxation of the non-thermoplastic polyimide resin layers and laminated polyimide films used in Examples, Comparative Examples and Reference Examples, and crack resistance results of flexible metal foil laminates. Show.

  The flexible metal foil laminates of Comparative Examples 1 to 5 were cracked when immersed in a desmear solution. In the reference example 1 in which the same flexible metal foil laminate as that in the comparative example 1 was used and the hot press was omitted, no crack was generated, and the thermal strain generated in the test piece by the hot press promoted the crack generation. It is shown that.

  On the other hand, in the flexible metal foil laminated body of Examples 1-12, it resulted in a crack not generating. The fact that the resin layer exhibits β relaxation indicates that thermal strain during hot pressing is relaxed. In addition, Examples 3 to 10 had a higher evaluation of crack resistance than Examples 1, 2, 11, and 12.

  The present invention can be used in the field of manufacturing flexible printed wiring boards.

1. Metal foil 1 '. Metal foil (inner layer circuit)
2. Glass epoxy board (FR4 board)
3. Adhesive 4. 4. Coverlay film Adhesive 6. 6. Multilayer polyimide film Nonwoven fabric 8. Metal plate 9. Craft 10. Vinyl chloride 11. Release film 12. Electrolytic copper foil 100. Rigid substrate 101. Flexible substrate 200. Laminate (7, 8, 9, 10, 11)
201. Flexible metal foil laminate

Claims (6)

A rigid flexible substrate formed by laminating a flexible metal foil laminate having a multilayer polyimide film and a metal foil, and a rigid substrate,
The multilayer polyimide film is a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer,
The multilayer polyimide film has a temperature at which the maximum value of loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement is 155 ° C to 185 ° C, and the maximum value is 0.03 to 0.15. Is,
The aromatic diamine used in the production of the non-thermoplastic polyimide resin layer includes 4,4′-diamino-2,2′-dimethylbiphenyl,
The aromatic tetracarboxylic dianhydride used in the production of the non-thermoplastic polyimide resin layer is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3, A rigid flexible substrate comprising 3 ′, 4,4′-benzophenonetetracarboxylic dianhydride or 4,4′-oxydiphthalic dianhydride.   The aromatic tetracarboxylic dianhydride used for manufacturing the non-thermoplastic polyimide resin layer includes 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride. The rigid flexible substrate according to claim 1, wherein:   The rigid flexible substrate according to claim 1 or 2, wherein the multilayer polyimide film has a thermoplastic polyimide film on at least one surface of the non-thermoplastic polyimide resin layer.   The multilayer polyimide film has a temperature at which the non-thermoplastic polyimide resin layer exhibits a maximum value of loss elastic modulus derived from β relaxation by dynamic viscoelasticity measurement at 155 ° C. to 185 ° C., and the maximum value. The rigid flexible substrate according to any one of claims 1 to 3, wherein the thickness is 0.05 to 0.15.   The rigid flexible substrate according to any one of claims 1 to 4, wherein the flexible metal foil laminate has a metal foil on at least one surface of the multilayer polyimide film.   The rigid flexible substrate according to claim 5, wherein the flexible metal foil laminate is formed by casting polyamic acid, which is a raw material of the multilayer polyimide film, on the metal foil.

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