JP5665846B2 - Thermally conductive polyimide film and thermal conductive laminate using the same - Google Patents

Description

  The present invention relates to a thermally conductive polyimide film containing a filler and a thermally conductive laminate using the same.

  In recent years, there has been an increasing demand for downsizing and weight reduction of electronic devices as represented by parts related to mobile phones, LED lighting fixtures, and automobile engines. Accordingly, flexible circuit boards that are advantageous for reducing the size and weight of devices have been widely used in the electronic technology field. Among them, a flexible circuit board using a polyimide resin as an insulating layer is widely used because of its good heat resistance and chemical resistance. On the other hand, with the recent miniaturization of electronic equipment, the degree of circuit integration has increased, and in order to increase the speed of information processing and improve reliability, technology to improve the heat dissipation characteristics of heat generated in equipment Is attracting attention.

  In order to improve the heat dissipation characteristics of the heat generated in the electronic device, it is considered effective to increase the thermal conductivity of the electronic device. Therefore, a technique in which a thermally conductive filler is contained in an insulating layer constituting a wiring board or the like has been studied. More specifically, it has been studied to disperse and blend a filler having high thermal conductivity such as aluminum oxide, boron nitride, aluminum nitride, and silicon nitride in the resin forming the insulating layer. And the technique which mix | blends a heat conductive filler with respect to polyimide resin with high heat resistance is proposed by patent document 1, etc., for example.

  Furthermore, it has been studied to obtain a high thermal conductivity by applying a technique of blending such a thermally conductive filler into a resin. For example, the applicant has previously proposed a high thermal conductive film and a metal-clad laminate in which a resin is filled with a combination of a plate-like thermal conductive filler and a spherical thermal conductive filler (PCT / JP2009 / 066552). However, the technique proposed in this patent application is mainly intended for application to a flexible substrate. Therefore, there is room for improvement in that the amount of the thermally conductive filler cannot be increased beyond a certain amount in order to maintain the flexibility (flexibility) of the metal-clad laminate. In addition, if a large amount of filler with a large particle size is filled, the stress applied to the interface between the resin and the filler increases, so voids are generated in the insulating layer, and there is a limit to the filling amount of the filler from that point. .

  In this way, when the filling rate of the high thermal conductive filler is increased or the particle size is increased, many voids are generated in the insulating layer during the process of forming the insulating layer, and the withstand voltage is improved. There was a problem of lowering. In general, in many cases of forming an insulating layer containing such a high thermal conductive filler, a method of applying a resin solution containing a high thermal conductive filler on a substrate and forming the insulating layer by heat treatment such as drying Is done by. In the manufacturing method of a heat conductive resin sheet, while devising volume mixing ratio, the technique which suppresses generation | occurrence | production of a space | gap by compressing after drying is examined (for example, refer patent document 2).

  However, the compression of the insulating layer may affect other characteristics of the insulating layer and the laminate including the insulating layer depending on the conditions.

Japanese Unexamined Patent Publication No. 2005-162878 Japanese Unexamined Patent Publication No. 2008-308576

  The object of the present invention is to provide excellent thermal conductivity and electrical insulation in addition to heat resistance and dimensional stability even when the insulating layer is filled with a large amount of thermally conductive filler, and has high adhesion to the metal layer. It is providing the heat conductive polyimide film and the heat conductive laminated body using the same.

The thermally conductive laminate of the present invention includes an insulating layer having at least one filler-containing polyimide resin layer containing a thermally conductive filler in a polyimide resin, a metal layer laminated on one or both sides of the insulating layer, It is what has. In this thermally conductive laminate, the content ratio of the thermally conductive filler in the filler-containing polyimide resin layer is in the range of 35 to 80 vol%, the maximum particle size of the thermally conductive filler is less than 15 μm, and the heat The conductive filler contains a plate-like filler and a spherical filler, the plate-form filler has an average major axis D _L in the range of 0.1 to 2.4 μm, and the thermal conductivity λz in the thickness direction of the insulating layer. Is 0.8 W / mK or more.

The thermally conductive polyimide film of the present invention has at least one filler-containing polyimide resin layer containing a thermally conductive filler in a polyimide resin. In this thermally conductive polyimide film, the content ratio of the thermally conductive filler in the filler-containing polyimide resin layer is in the range of 35 to 80 vol%, the maximum particle size of the thermally conductive filler is less than 15 μm, and the heat contains a plate-like filler and spherical filler as conductive filler, the average long diameter D _L of the plate-like filler is in the range of 0.1～2.4Myuemu, thermal conductivity λz in the thickness direction of the insulating layer Is 0.8 W / mK or more.

  According to the heat conductive polyimide film and the heat conductive laminate of the present invention, in addition to the heat resistance and dimensional stability of the polyimide resin used as the matrix of the insulating layer, the heat conductive characteristics are also excellent. Even when the insulating layer contains a large amount of thermally conductive filler, the withstand voltage is excellent because the generation of voids in the insulating layer is suppressed or reduced. Furthermore, the thermally conductive polyimide film and the thermally conductive laminate of the present invention are advantageous because they can be produced by the usual processes such as coating and heat treatment without requiring a special process such as compression of the insulating layer. is there.

[Thermal conductive laminate]
The heat conductive laminated body which concerns on embodiment of this invention consists of a metal layer which has an insulating layer and the single side | surface or both surfaces. The insulating layer is composed of a polyimide resin, and at least one layer is a filler-containing polyimide resin layer containing a thermally conductive filler in the polyimide resin. The insulating layer may consist only of a filler-containing polyimide resin layer, or may have a polyimide resin layer that does not contain a filler. When having a polyimide resin layer that does not contain a filler, the thickness thereof is, for example, in the range of 1/100 to 1/2 of the filler-containing polyimide resin layer, preferably in the range of 1/20 to 1/3. Good. In the case of having a polyimide resin layer containing no filler, if the polyimide resin layer is in contact with the metal layer, the adhesion between the metal layer and the insulating layer is improved.

<Thermal conductive filler>
In the present invention, a plate-like filler and a spherical filler are used as the thermally conductive filler in the filler-containing polyimide resin layer. The volume ratio (also referred to as “content” or “content ratio”) of the thermally conductive filler in this layer is 35 to 35 in terms of the total amount of the plate-like filler and the spherical filler in order to impart excellent thermal conductivity to the thermally conductive laminate. It is in the range of 80 vol%, preferably in the range of 50 to 70 vol%, more preferably in the range of 55 to 65 vol%, most preferably in the range of 55 to 59 vol%. If the content rate of a heat conductive filler is less than 35 vol%, a heat conductive characteristic will become low and sufficient characteristics as a thermal radiation material cannot be obtained. In addition, when the content ratio of the heat conductive filler exceeds 80 vol%, the insulating layer becomes brittle and difficult to handle, and when the insulating layer is formed from a polyamic acid solution, the viscosity of the varnish increases, The nature is also reduced.

  Further, in the present invention, the volume ratio (A) of the plate-like filler in the filler-containing polyimide resin layer is spherical in order to suppress or reduce the occurrence of voids in the insulating layer and increase the withstand voltage characteristics. It is preferable to make it larger than the volume ratio (B) of the filler. Specifically, (A) / (B) is more preferably in the range of 1 to 15, and most preferably in the range of 1.5 to 15.

Here, the plate-like filler is a filler having a plate-like or flake-like filler shape and having an average thickness sufficiently smaller than the average major axis or minor axis (preferably 1/2 or less) of the surface portion. . The plate-like filler used in the present invention has an average major axis D _L in the range of 0.1 to 2.4 μm. If the average major axis D _L is less than 0.1 μm, the thermal conductivity is low, the thermal expansion coefficient is increased, and the plate-like effect is reduced. If the average major axis D _L exceeds 2.4 μm, voids are likely to occur due to stress concentration during film formation. Here, the average major axis D _L means the average value of the longitudinal diameters of the plate-like fillers. Preferable specific examples of the plate-like filler include boron nitride, aluminum oxide and the like, and these can be used alone or in combination of two or more. The average long diameter D _L of the plate-like filler is preferable from the viewpoint of high thermal conductivity in the range of 0.5～2.2Myuemu. The most suitable plate-like filler used in the present invention is boron nitride having an average major axis D _{L of 1} to 2.2 μm. The average diameter means the median diameter, and the mode diameter is preferably one in the above range, and this is the same for the spherical filler.

In addition, the spherical filler refers to a filler having a spherical shape or a spherical shape, and a ratio of an average major axis to an average minor axis close to 1 or 1 (preferably 0.8 or more). The average particle diameter D _R of the spherical filler used in the present invention is preferably in the range of 0.05 to 5.0 μm. When the average particle diameter D _R is less than 0.05 .mu.m, the effect of thermal conductivity enhancement is reduced. If the average particle diameter D _R of the spherical filler exceeds 5 [mu] m, may become spherical filler is difficult to enter between the layers of the plate-like filler, the void with increasing stress due periphery of the resin shrinkage is or generated, the invention effects It becomes difficult to control. Here, the average particle diameter D _R, means the average value of the diameters of spherical filler particles (median diameter). Preferable specific examples of the spherical filler include, for example, aluminum oxide, fused silica, and aluminum nitride, and these can be used alone or in combination of two or more. For example, aluminum oxide is preferable in terms of excellent moisture resistance, and aluminum nitride is preferable in terms of imparting high thermal conductivity to the insulating layer. Therefore, the material of the spherical filler can be selected according to the use of the heat conductive laminate, and can be used in combination as necessary. The average particle diameter D _R of the spherical filler is preferred from the viewpoint of filling improvement within the scope of 0.1～4.0Myuemu. The most suitable spherical filler used in the present invention is aluminum oxide having an average particle diameter D _R in the range of 0.5 to 3.0 μm. Aluminum oxide has poor thermal conductivity, but this drawback is eliminated by using both plate-like fillers and spherical fillers. However, when a higher thermal conductivity is desired, either or both of the plate-like filler and the spherical filler are preferably fillers other than aluminum oxide.

  The heat conductive filler referred to in the present invention preferably has a thermal conductivity of 5.0 W / m · K or more. When it becomes less than 5.0 W / mK of a heat conductive filler, the heat dissipation effect at the time of setting it as a laminated body will fade.

  Moreover, it is preferable to make the content rate of a spherical filler into the range of 25-70 wt% from a viewpoint of coexistence of a heat conductivity improvement and a withstand voltage improvement in a heat conductive filler. In addition, when it has the polyimide resin layer which does not contain a filler, the content rate of the heat conductive filler in all the insulation layers becomes like this. Preferably it is the range of 30-90 wt%, More preferably, it is 30-85 wt%, More preferably, it is 30-60 wt% It is good to do.

The heat conductive filler _preferably has a relationship between the average major axis D _L and the average particle diameter D _R of D _L > D _R / 2, and does not contain a heat conductive filler of 30 μm or more. If the relationship between the average major axis D _L and the average particle diameter D _R does not satisfy the requirement of D _L > D _R / 2, the thermal conductivity will be reduced. Moreover, when a heat conductive filler of 30 μm or more is contained, the appearance of the surface tends to be poor. The relationship between the average major axis D _L and the average particle diameter D _R is more preferably D _L > D _R. The range is preferably D _R is in the range of 1 / 3-5 / 3 of D _L.

  Further, the filler having a particle size of 9 μm or more in the heat conductive filler to be used is preferably 50 wt% or less of the whole, and in particular, the proportion of the filler having a particle size of 9 μm or more in the plate-like filler is 50 wt% or less. It is preferable to do. This eliminates the irregularities on the surface of the insulating layer and makes the surface smooth. Here, the particle diameter in the case of a plate-like filler means a major axis.

  Moreover, the maximum particle diameter of the heat conductive filler used by this invention needs to be less than 15 micrometers. When the maximum particle diameter is 15 μm or more, irregularities on the surface of the insulating layer are generated, and voids are easily generated at the interface between the filler and the resin. Here, the maximum particle diameter in the case of a plate-like filler means a long diameter. In the present invention, any of the thermal conductive fillers can be selected from commercially available products.

<Insulating layer>
The polyimide resin that serves as the matrix resin of the insulating layer in the present invention is generally represented by the following general formula (1). Such a polyimide resin can be produced by a known method in which a diamine component and an acid dianhydride component are used in substantially equimolar amounts and polymerized in an organic polar solvent. In this case, in order to make a viscosity into a desired range, you may adjust the molar ratio of the acid dianhydride component with respect to a diamine component, and the range has a preferable molar ratio range of 0.980 to 1.03, for example.

ここで、Ａｒ₁は芳香族環を１個以上有する４価の有機基であり、Ａｒ₂は芳香族環を１個以上有する２価の有機基である。そして、Ａｒ₁は酸二無水物の残基ということができ、Ａｒ₂はジアミンの残基ということができる。また、ｎは、一般式（１）の構成単位の繰返し数を表し、２００以上、好ましくは３００〜１０００の数である。

Here, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is a divalent organic group having one or more aromatic rings. Ar ₁ can be referred to as an acid dianhydride residue, and Ar ₂ can be referred to as a diamine residue. Moreover, n represents the repeating number of the structural unit of General formula (1), and is 200 or more, Preferably it is a number of 300-1000.

As the acid dianhydride, for example, an aromatic tetracarboxylic dianhydride represented by O (OC) ₂ —Ar ₁ — (CO) ₂ O is preferable, and the following aromatic acid anhydride residue is represented by Ar _1. Examples are given.

  An acid dianhydride can be used individually or in mixture of 2 or more types. Among these, pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4'-benzophenone tetracarboxylic acid Use one selected from anhydride (BTDA), 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), and 4,4'-oxydiphthalic dianhydride (ODPA) Is preferred.

As the diamine, for example, an aromatic diamine represented by H ₂ N—Ar ₂ —NH ₂ is preferable, and an aromatic diamine giving the following aromatic diamine residue as Ar ₂ is exemplified.

  Among these diamines, diaminodiphenyl ether (DAPE), 2,2′-dimethyl-4,4′-diaminobiphenyl (m-TB), paraphenylenediamine (p-PDA), 1,3-bis (4-amino) Phenoxy) benzene (TPE-R), 1,3-bis (3-aminophenoxy) benzene (APB), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), and 2,2-bis [ 4- (4-Aminophenoxy) phenyl] propane (BAPP) is exemplified as a suitable one.

  Examples of the solvent used for the polymerization of the diamine component and the acid dianhydride component include dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene, and the like. It can also be used in combination. The resin viscosity of the polyamic acid (polyimide precursor) obtained by polymerization is preferably in the range of 500 cps to 35000 cps, particularly preferably in the range of 1000 cps to 10000 cps.

  The method for forming the insulating layer of the thermally conductive laminate of the present invention is not particularly limited, and a known method can be adopted. Here, the most typical example is shown. First, a polyamic acid resin solution containing a heat conductive filler, which is a raw material for the insulating layer, is directly cast applied onto a metal foil such as a copper foil as a metal layer to form a coating film. Here, the polyamic acid is a polyimide precursor resin. Next, the solvent is removed to some extent by drying the coating film at a temperature of 150 ° C. or lower. Thereafter, the coating film is further subjected to heat treatment at 100 to 400 ° C., preferably 130 to 360 ° C. for about 5 to 30 minutes for imidization. In this way, an insulating layer made of a polyimide resin containing a thermally conductive filler can be formed on the metal layer. When the insulating layer is composed of two or more polyimide layers, the first polyamic acid resin solution is applied and dried, and then the second polyamic acid resin solution is applied and dried. Thereafter, the third polyamic acid resin solution, the fourth polyamic acid resin solution, and so on in the same manner are sequentially applied as many times as necessary. And dry. Then, it is good to perform imidation by collectively performing heat treatment for about 5 to 30 minutes in a temperature range of 100 to 400 ° C. If the temperature of the heat treatment is lower than 100 ° C., the dehydration ring closure reaction of polyimide does not proceed sufficiently. On the other hand, if it exceeds 400 ° C., the polyimide resin layer and the copper foil may be deteriorated due to oxidation or the like.

  Another example of forming an insulating layer is given. First, a polyamic acid resin solution containing a heat conductive filler, which is a raw material of an insulating layer, is cast-coated on an arbitrary support substrate and molded into a film shape. This film-like molded product is heated and dried on a support to obtain a gel film having self-supporting properties. Then, after peeling a gel film from a support body, it heat-processes further at high temperature, is imidized, and is set as a polyimide film. In order to obtain a thermally conductive laminate using this polyimide film as an insulating layer, for example, a polyimide film by a method such as heat-pressing a metal foil directly or via an arbitrary adhesive on a polyimide film or a method such as metal vapor deposition A method of forming a metal layer is generally used.

  When preparing the polyamic acid resin solution containing the heat conductive filler used in the formation of the insulating layer, for example, the heat conductive filler may be directly blended into the polyamic acid resin solution. Alternatively, in consideration of filler dispersibility, a heat conductive filler is added in advance to a reaction solvent in which one of the raw materials (acid dianhydride component or diamine component) of the polyamic acid resin solution is added, and then the other is stirred. Polymerization may be carried out by introducing raw materials. In the case of direct blending, the whole amount of filler may be added at once, or may be added little by little in several times. Moreover, the raw material of the resin solution may be put in a lump or may be mixed little by little in several times.

  The insulating layer may be composed of a single layer or may be composed of a plurality of layers. For example, in order to make the dimensional stability of a heat conductive laminated body and the adhesive strength with copper foil excellent, it can also be made into multiple layers. Here, when making an insulating layer into multiple layers, when heat conductivity is considered, it is preferable to make a heat conductive filler contain in all the layers. However, by making the adjacent layer of the filler-containing polyimide resin layer a layer that does not contain a filler or a layer that has a low content, the filler can be prevented from slipping off during processing, etc. Can do. In addition, this invention does not exclude using the adhesive agent for adhere | attaching a filler containing polyimide resin layer and metal foil. However, when an adhesive layer is interposed in a thermally conductive laminate having metal layers on both sides of the insulating layer, the thickness of the adhesive layer is less than 30% of the thickness of the entire insulating layer so as not to impair the thermal conductivity. And preferably less than 20%. In the case where an adhesive layer is interposed in a thermally conductive laminate having a metal layer only on one side of the insulating layer, the thickness of the adhesive layer is 15% of the thickness of the entire insulating layer so as not to impair the thermal conductivity. Preferably, the content is less than 10%, and more preferably less than 10%. And since an adhesive bond layer comprises a part of insulating layer, it is preferable that it is a polyimide resin layer. The glass transition temperature of the polyimide resin as the main material of the insulating layer is preferably 300 ° C. or higher from the viewpoint of imparting heat resistance. In order to set the glass transition temperature to 300 ° C. or higher, it is possible to appropriately select the above acid dianhydride or diamine component constituting the polyimide resin.

  In the thermally conductive laminate of the present invention, the thickness of the insulating layer is preferably in the range of 10 to 100 μm, for example, and more preferably in the range of 12 to 50 μm. If the thickness of the insulating layer is less than 10 μm, defects such as wrinkles in the metal foil are likely to occur in the transport process during the production of the heat conductive laminate. On the other hand, when the thickness of the insulating layer exceeds 100 μm, it tends to be disadvantageous in terms of high thermal conductivity and flexibility. The withstand voltage of the insulating layer is preferably 2 kV or more.

The thermal expansion coefficient (CTE) of the insulating layer is preferably in the range of 5 × 10 ⁻⁶ to 30 × 10 ⁻⁶ / K (5 to 30 ppm / K), for example, and 10 × 10 ^{−6 to} 25 × 10. ^-6 / K (10-25 ppm / K) is more preferable. When the thermal expansion coefficient of the insulating layer is smaller than 5 × 10 ⁻⁶ / K, curling is likely to occur after the heat conductive laminate is formed, and handling properties are poor. On the other hand, when the thermal expansion coefficient of the insulating layer exceeds 30 × 10 ⁻⁶ / K, the dimensional stability as an electronic material such as a flexible substrate is inferior, and the heat resistance tends to decrease.

  The thermal conductivity λz in the thickness direction of the insulating layer in the present invention needs to be 0.8 W / mK or more, preferably 1.0 W / mK or more, and more preferably 1.5 W / mK or more. More preferred. If the thermal conductivity λz is less than 0.8 W / mK, the objective cannot be achieved in the thermally conductive laminate of the present invention whose main purpose is application to heat dissipation. By satisfying this thermal conductivity characteristic and other structural requirements, a thermally conductive laminate that satisfies other characteristics at the same time can be obtained. In particular, when the thermal conductivity λz is 1.0 W / mK, excellent heat dissipation characteristics can be obtained. For example, in addition to the heat dissipation substrate, a heat conductive laminate applicable to many uses can be obtained. Further, the thermal conductivity of the insulating layer is advantageously 1.0 W / mK or more in the plane direction, and preferably 2.0 W / mK or more.

  As described above, the thermally conductive laminate of the present invention may be provided with a metal layer only on one side of the insulating layer, or may be provided with metal layers on both sides of the insulating layer. . In addition, the heat conductive laminated body provided with the metal layer on both surfaces is formed by, for example, a method of forming a laminated body of single-sided metal layers and then pressing and pressing the polyimide resin layers to each other by hot pressing, or a single-sided metal layer It can obtain by the method etc. which press-fit and form metal foil to the polyimide resin layer of this laminated body.

<Metal layer>
The metal layer may be made of a metal foil as described above, or may be a metal vapor deposited on a film. Moreover, from the point which can apply | coat the polyimide precursor containing a heat conductive filler directly, a metal foil or a metal plate is possible, and a copper foil or a copper plate is especially preferable. The thickness of the metal layer is preferably in the range of 5 μm to 3 mm, for example, and more preferably in the range of 12 μm to 1 mm. If the thickness of the metal layer is less than 5 μm, there is a possibility that problems such as wrinkles occur during conveyance in the production of laminated substrates and the like. On the contrary, if the thickness of the metal layer exceeds 3 mm, it is hard and the workability is deteriorated. As for the thickness of the metal layer, generally, a thick metal layer is suitable for in-vehicle use, and a thin metal layer is suitable for LED use.

[Thermal conductive polyimide film]
The thermally conductive polyimide film according to the embodiment of the present invention adopts the same configuration as the insulating layer in the thermally conductive laminate of the present invention, and details thereof are the insulating layer of the above-described thermally conductive laminate of the present invention. Reference is made to the description. That is, the insulating layer film obtained by removing the metal layer from the above-described thermally conductive laminate has the same configuration as the thermally conductive polyimide film of the present invention. Moreover, it can be said that the heat conductive laminated body of this invention has the heat conductive polyimide film of this invention as an insulating layer.

  In the manufacturing method of the heat conductive laminate, the formation of the insulating layer was explained that the insulating layer can be formed on the metal layer as a supporting base material, but in the manufacture of the heat conductive polyimide film of the present invention. The support base material to be used is not particularly limited, and a base material of any material can be used. In forming the thermally conductive polyimide film, it is not necessary to form a resin film that has been completely imidized on the substrate. For example, the resin film in a semi-cured polyimide precursor state can be separated from the support substrate by means such as peeling, and after separation, imidization can be completed to obtain a heat conductive polyimide film. Except for these points, as described above, the description of the insulating layer of the thermally conductive laminate of the present invention is referred to, and thus the description thereof is omitted.

  EXAMPLES Hereinafter, although this invention is shown concretely based on an Example, this invention is not limited to these Examples.

Abbreviations used in this example are shown below.
m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl
TPE-R: 1,3-bis (4-aminophenoxy) benzene
BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane
PMDA: pyromellitic dianhydride
BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride
DMAc: N, N-dimethylacetamide
DAPE: 4,4'-diaminodiphenyl ether

Moreover, the following evaluation method was followed about each characteristic evaluated in the Example.
[Thickness direction thermal conductivity (λz)]
A film to be measured (insulating film, hereinafter the same) is cut into a size of 20 mm × 20 mm, and the thermal diffusivity in the thickness direction by a laser flash method (LFA 447 Nanoflash device manufactured by Bruker AXS), DSC (differential scanning calorimetry) ) And the density by the gas displacement method were measured, and the thermal conductivity was calculated based on these results.

[Coefficient of thermal expansion (CTE)]
A tensile test was performed on a 3 mm x 15 mm size insulating film in a temperature range from 30 ° C to 260 ° C at a constant temperature increase rate (20 ° C / min) while applying a 5 g load with a thermomechanical analysis (TMA) device. The thermal expansion coefficient (ppm / K) was measured from the amount of elongation of the insulating film with respect to temperature.

[Glass transition temperature (Tg)]
When an insulating film (10 mm × 22.6 mm) was heated from 20 ° C. to 500 ° C. at a rate of 5 ° C./min using a dynamic thermomechanical analyzer, the glass transition temperature (tan δ maximum value) was measured. : ° C.).

[Adhesive strength]
The sample in which the copper foil and the resin layer are in close contact with each other to withstand the sample processing (circuit processing) for measuring the withstand voltage is evaluated as “Good”, and the resin layer is peeled off from the copper foil during processing or evaluation. The sample was x (defect). Moreover, the adhesive force of Examples 4-6 uses a tension tester, fixes the resin side of a copper-clad product with a width of 1 mm to an aluminum plate with a double-sided tape, and peels copper in a 180 ° direction at a speed of 50 mm / min. The peel strength was determined.

[Withstand voltage]
The thermally conductive laminate was cut to a size of 5 cm × 5 cm, the copper foil on one side was processed into a 2 cm diameter circle, and unnecessary portions were removed with a copper foil etchant. Based on JIS C2110, withstand voltage was measured in insulating oil by a step-up method using a TOS 5101 apparatus manufactured by KIKUSUI. The voltage was stepped up in steps of 0.2 kV, held at each voltage for 20 seconds, a leakage current of 8.5 mA, and the value immediately before the broken voltage was the initial withstand voltage. The size of the electrode is 2 cmφ. The sample was held in an environment of 120 ° C./95 RH% humidity for 24 hours, and the measured withstand voltage was taken as the withstand voltage after wet heat.

Synthesis example 1
Under a nitrogen stream, m-TB (12.4591 g, 0.0587 mol) and DAPE (9.6152 g, 0.0480 mol) were dissolved in 255 g of solvent DMAc with stirring in a 500 ml separable flask. Next, PMDA (22.9258 g, 0.1051 mol) was added thereto. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a brownish brown viscous polyamic acid solution (P1).

Synthesis example 2
Under a nitrogen stream, BAPP (23.2045 g, 0.0565 mol) was dissolved in 264 g of solvent DMAc with stirring in a 500 ml separable flask. PMDA (11.9473 g, 0.0548 mol) and BPDA (0.8482 g, 0.0029 mol) were then added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a brownish brown viscous polyamic acid solution (P2).

Synthesis example 3
Under a nitrogen stream, m-TB (19.1004 g, 0.08997 mol) and TPE-R (2.9224 g, 0.0100 mol) were dissolved in 255 g of solvent DMAc with stirring in a 500 ml separable flask. Next, PMDA (17.1827 g, 0.07878 mol) was added, and after stirring for 10 minutes, BPDA (5.7944 g, 0.0197 mol) was further added. Thereafter, the solution was stirred at room temperature for 4 hours to carry out a polymerization reaction, thereby obtaining a brownish brown viscous polyamic acid solution (P3).

Example 1
65.242 g of a polyamic acid solution (P1), 18.16 g of commercially available boron nitride (scalar shape, average major axis 2.2 μm, maximum particle size 11 μm) as a plate-like filler, and commercially available alumina (spherical, average particles) as a spherical filler (3 μm diameter, maximum particle diameter 10 μm) and 3.55 g were mixed with a centrifugal stirrer until uniform. Thereafter, 13.048 g of DMAc was added for viscosity adjustment, and mixed with a centrifugal stirrer until uniform again to obtain a polyamic acid solution (P4) containing a thermally conductive filler.
A polyamic acid solution (P2) containing no filler was applied onto an electrolytic copper foil having a thickness of 35 μm so as to have a thickness after curing of 2.0 μm, and dried by heating at 130 ° C. to remove the solvent. Next, a solution of a polyamic acid (P4) containing a thermally conductive filler obtained by mixing a plate filler and a spherical filler was applied so that the thickness after curing was 22 μm, and the solvent was removed by heating at 130 ° C. . Further, a polyamic acid solution (P2) containing no filler was applied thereon so that the thickness after curing was 2.0 μm, and dried by heating at 130 ° C. to remove the solvent. Thereafter, the temperature is raised in a temperature range of 130 to 300 ° C. over 20 minutes, and the thermally conductive laminate M1 (P2 / P4 / P) having an insulating layer made of three polyimide layers on the copper foil. P2) was prepared.
In order to evaluate the characteristics of the insulating layer in the obtained thermal conductive laminate M1, the copper foil was removed by etching to produce an insulating film, and the thermal conductivity, CTE, and Tg were evaluated. The results are shown in Table 2. Furthermore, the adhesive strength of the metal-insulating resin layer in the thermally conductive laminate, the withstand voltage after initial heat treatment, and wet heat were measured. The results are shown in Table 3.

  Unless otherwise specified, the same items as in Example 1 were evaluated for the insulating films and thermally conductive laminates obtained in the following Examples and Comparative Examples.

Example 2
54.092 g of the polyamic acid solution (P1), 12.71 g of the same boron nitride as in Example 1 as a plate-like filler, and 22.38 g of the same alumina as in Example 1 as a spherical filler were mixed with a centrifugal stirrer until uniform. . Thereafter, 10.818 g of DMAc was added to adjust the viscosity, and mixed again with a centrifugal stirrer until uniform, to obtain a polyamic acid solution (P5) containing a thermally conductive filler.
Using a copper foil having a thickness of 500 μm, a thermally conductive laminate M2 (P2 / P5 / P2) having a thickness structure of 2.0 μm / 24 μm / 2.0 μm after curing was produced in the same manner as in Example 1. .
Using the obtained heat conductive laminate M2, an insulating film was produced in the same manner as in Example 1, and the properties of the insulating film were evaluated, and the heat conductive laminate was also evaluated. The respective evaluation results are shown in Table 2 and Table 3.

Example 3
78.98 g of the polyamic acid solution (P2), 17.58 g of the same boron nitride as in Example 1 as a plate-like filler, and 3.44 g of the same alumina as in Example 1 as a spherical filler were mixed with a centrifugal stirrer until uniform. A polyamic acid solution (P6) containing a thermally conductive filler was obtained.
A heat conductive laminate M3 (P2 / P6 / P2) having a thickness structure of 2.0 μm / 21 μm / 2.0 μm after curing was prepared in the same manner as in Example 1 by using a copper foil having a thickness of 35 μm. .

Comparative Example 1
Polyamide acid solution (P3) 86.96 g, boron nitride (commercial product: scale shape, average major axis 4.5 μm, maximum particle size 20 μm) 6.52 g as plate-like filler, and alumina 6 as in Example 1 as spherical filler Was mixed with a centrifugal stirrer until uniform to obtain a polyamic acid solution (P7) containing a thermally conductive filler.
A heat conductive laminate M4 (P2 / P7 / P2) having a thickness structure of 2.0 μm / 21 μm / 2.0 μm after curing was prepared in the same manner as in Example 1 using a copper foil having a thickness of 12 μm.

Comparative Example 2
86.96 g of polyamic acid solution (P3), boron nitride as a plate-like filler (commercial product: scale shape, average major axis 2.5 μm, maximum particle size 11 μm) 6.52 g, and the same alumina as in Example 1 as a spherical filler 6.52 g was mixed with a centrifugal stirrer until uniform to obtain a polyamic acid solution (P8) containing a thermally conductive filler.
Using a copper foil having a thickness of 12 μm, a thermally conductive laminate M5 (P2 / P8 / P2) having a thickness structure of 2.0 μm / 21 μm / 2.0 μm after curing was produced in the same manner as in Example 1.

Comparative Example 3
61.467 g of the polyamic acid solution (P3), 9.50 g of boron nitride as in Comparative Example 1 as a plate-like filler, and 16.74 g of alumina as in Example 1 as a spherical filler were mixed with a centrifugal stirrer until uniform. Then, 12.293 g of DMAc was added for viscosity adjustment and mixed with a centrifugal stirrer until uniform again to obtain a polyamic acid solution (P9) containing a thermally conductive filler.
Using a copper foil having a thickness of 12 μm, a thermally conductive laminate M6 (P2 / P9 / P2) having a thickness structure after curing of 2.0 μm / 20 μm / 2.0 μm was produced in the same manner as in Example 1.

Synthesis example 4
Under a nitrogen stream, m-TB (10.38 g, 0.049 mol) and DAPE (8.01 g, 0.040 mol) were dissolved in 262.50 g of the solvent DMAc with stirring in a 500 ml separable flask. PMDA (19.10 g, 0.088 mol) was then added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction to obtain a brownish brown viscous polyamic acid resin solution (P10).

Synthesis example 5
Under a nitrogen stream, BAPP (23.20 g, 0.057 mol) was dissolved in 264 g of solvent DMAc with stirring in a 500 ml separable flask. PMDA (11.9473 g, 0.0548 mol) and BPDA (0.8482 g, 0.0029 mol) were then added. Thereafter, the solution was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a brownish brown viscous polyamic acid solution (P11).

Example 4
72.71 g of a polyamic acid solution (P10) having a solid content concentration of 12.5 wt% and boron nitride (made by Denki Kagaku Kogyo Co., Ltd., trade name: SP-3 ′, scale shape, average major axis 2. 2 μm) with particles exceeding 11 μm removed by a classifier and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle size 3 μm, maximum particle size) 11 μm) and 19.80 g were mixed with a centrifugal stirrer until uniform to obtain a polyamic acid resin solution (P10 ′) containing a thermally conductive filler.

  On an electrolytic copper foil having a thickness of 35 μm subjected to rust prevention treatment, a polyamic acid resin solution (P11) containing no filler is applied so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. The solvent was removed. Next, the polyamic acid resin solution (P10 ') containing the above heat conductive filler was applied thereon so that the thickness after curing was 21 µm, and the solvent was removed by heating at 130 ° C. Further, a polyamic acid resin solution (P11) containing no filler is applied thereon so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. to remove the solvent. In the temperature range of ° C., the temperature is raised and heated stepwise over 20 minutes to produce a thermally conductive laminate M7 (P11 / P10 ′ / P11) having an insulating layer composed of three polyimide layers on the copper foil. did. Table 4 shows the configuration of the insulating layer in the thermally conductive laminate M7.

  In order to evaluate the characteristics of the insulating layer (film) in the obtained heat conductive laminate M7, the copper foil was removed by etching to produce an insulating film (F3). CTE, tear propagation resistance, glass transition temperature, heat conduction Each rate was evaluated. The results are shown in Table 5. Furthermore, Table 6 shows the adhesive strength between the insulating layer and the copper foil in the thermally conductive laminate M7.

  Further, a 12 μm-thick electrolytic copper foil subjected to rust prevention treatment on the heat-resistant resin layer of the obtained heat-conductive laminate M7 is pressed at a maximum temperature of 380 ° C., and a heat-conductive laminate of double-sided metal M7 'was obtained. This was used for withstand voltage measurement. The results are shown in Table 6.

Example 5
74.54 g of a polyamic acid solution (P11) having a solid content concentration of 12.0 wt% and boron nitride (made by Denki Kagaku Kogyo Co., Ltd., trade name: SP-3 ′, scale shape, average major axis 2. 2 μm) by removing particles over 11 μm with a classifier and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle size 3 μm, maximum particle size) 11 μm) and 16.24 g were mixed with a centrifugal stirrer until uniform to obtain a polyamic acid resin solution (P11 ′) containing a thermally conductive filler.

  On an electrolytic copper foil having a thickness of 35 μm subjected to rust prevention treatment, a polyamic acid resin solution (P11) containing no filler is applied so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. The solvent was removed. Next, the polyamic acid resin solution (P11 ') containing the above heat conductive filler was applied thereon so that the thickness after curing was 21 μm, and the solvent was removed by heating at 130 ° C. Further, a polyamic acid resin solution (P11) containing no filler is applied thereon so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. to remove the solvent. In the temperature range of ° C., the temperature was raised and heated stepwise over 20 minutes to produce a thermally conductive laminate M8 having an insulating layer composed of three polyimide layers on the copper foil. Table 4 shows the configuration of the insulating layer in the thermally conductive laminate M8.

  In order to evaluate the characteristics of the insulating layer (film) in the obtained thermal conductive laminate M8, the copper foil was removed by etching to produce an insulating film (F4), and CTE, tear propagation resistance, glass transition temperature, thermal conductivity Each rate was evaluated. The results are shown in Table 5. Furthermore, Table 6 shows the adhesive strength between the insulating layer and the copper foil in the thermally conductive laminate M8.

  Moreover, on the heat-resistant resin layer of the obtained heat conductive laminate M8, a 12 μm thick electrolytic copper foil subjected to rust prevention treatment is pressed at a maximum temperature of 380 ° C., and the heat conductive laminate of double-sided metal The body M8 ′ was obtained. This was used for withstand voltage measurement. The results are shown in Table 6.

Example 6
57.60 g of a polyamic acid solution (P10) with a solid content concentration of 12.5 wt%, and boron nitride as a plate-like filler (trade name: SP-3 ′, scale shape, average major axis 2. 15.7 g obtained by removing particles exceeding 11 μm with a classifier, and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle size 3 μm, maximum particle size) 11 μm) and 3.1 g were mixed with a centrifugal stirrer until uniform to obtain a polyamic acid resin solution (P10 ″) containing a thermally conductive filler.

  On an electrolytic copper foil having a thickness of 35 μm subjected to rust prevention treatment, a polyamic acid resin solution (P11) containing no filler is applied so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. The solvent was removed. Next, the polyamic acid resin solution (P10 ″) containing the above heat conductive filler was applied thereon so that the thickness after curing was 23 μm, and the solvent was removed by heating at 130 ° C. Further, a polyamic acid resin solution (P11) containing no filler is applied thereon so that the thickness after curing is 1.5 μm, and dried by heating at 130 ° C. to remove the solvent. In the temperature range of ° C., the temperature was raised and heated stepwise over 20 minutes to produce a thermally conductive laminate M9 having an insulating layer composed of three polyimide layers on the copper foil. Table 4 shows the configuration of the insulating layer in the thermally conductive laminate M9.

  In order to evaluate the characteristics of the insulating layer (film) in the obtained heat conductive laminate M9, the copper foil was removed by etching to produce an insulating film (F5). CTE, tear propagation resistance, glass transition temperature, heat conduction Each rate was evaluated. The results are shown in Table 5. Furthermore, Table 6 shows the adhesive strength between the insulating layer and the copper foil in the thermally conductive laminate M9.

  Moreover, on the heat-resistant resin layer of the obtained heat conductive laminate M9, a 12 μm thick electrolytic copper foil subjected to rust prevention treatment is pressed at a maximum temperature of 380 ° C., and the heat conductive laminate of double-sided metal The body M9 ′ was obtained. This was used for withstand voltage measurement. The results are shown in Table 6.

Example 7
79.5 g of a polyamic acid solution (P10) having a solid content concentration of 12.5 wt%, and boron nitride (made by Denki Kagaku Kogyo Co., Ltd., trade name: SP-3 ′, scale shape, average major axis 2. 8.4 g obtained by removing particles exceeding 11 μm with a classifier, and aluminum nitride as a spherical filler (trade name: AlN-H, spherical, average particle diameter 1.1 μm, manufactured by Tokuyama Corporation) 12 0.09 g was mixed with a centrifugal stirrer until uniform to obtain a polyamic acid resin solution (P10 ′ ″) containing a thermally conductive filler.

  The polyamic acid resin solution (P10 ′ ″) containing the above-mentioned heat conductive filler is applied onto an electrolytic copper foil having a thickness of 35 μm subjected to rust prevention treatment so that the thickness after curing becomes 25 μm, and 130 The solvent was removed by heating at 0 ° C. Then, it heated up and heated in steps in the temperature range of 130-300 degreeC over 20 minutes, and produced the heat conductive laminated body M10 which has an insulating layer which consists of one polyimide layer on copper foil. Table 4 shows the configuration of the insulating layer in the thermally conductive laminate M10.

  In order to evaluate the characteristics of the insulating layer (film) in the obtained heat conductive laminate M10, the copper foil was removed by etching to produce an insulating film (F6), and CTE, tear propagation resistance, glass transition temperature, heat conduction Each rate was evaluated. The results are shown in Table 5. Furthermore, Table 6 shows the adhesive strength between the insulating layer and the copper foil in the thermally conductive laminate M10.

  Further, a 12 μm-thick electrolytic copper foil subjected to a rust prevention treatment on the heat-resistant resin layer of the obtained heat-conductive laminate M10 is pressed at a maximum temperature of 380 ° C. to obtain a double-sided metal heat-conductive laminate. M10 ′ was obtained. This was used for withstand voltage measurement. The results are shown in Table 6.

From the above results, at least,
a) The content ratio of the thermally conductive filler in the filler-containing polyimide resin layer is in the range of 35 to 80 vol%,
b) The maximum particle size of the thermally conductive filler is less than 15 μm,
c) The heat conductive filler contains a plate-like filler and a spherical filler, and the average major axis D _L of the plate-like filler is in the range of 0.1 to 2.4 μm.
The heat conductive laminates and the heat conductive polyimide films of Examples 1 to 7 that satisfy the above requirements are excellent in heat conduction characteristics in addition to the heat resistance and dimensional stability of the polyimide resin that is the matrix of the insulating layer. It was. Moreover, it was excellent also in withstand voltage property by the generation | occurrence | production of the space | gap in an insulating layer being suppressed or reduced. Furthermore, the heat conductive polyimide films and heat conductive laminates of Examples 1 to 7 can be produced by a process such as coating or heat treatment that is normally performed without requiring a special process such as compression of the insulating layer. It was. Therefore, various characteristics required as an insulating layer such as a wiring board are not impaired and can be applied to various electronic devices.

  On the other hand, in Comparative Example 1 that does not satisfy the requirements a) to c) and Comparative Example 2 that does not satisfy the requirement a), the thermal conductivity λz in the thickness direction of the insulating layer is 0.8 W / The result was lower than mK and the thermal conductivity was low. In Comparative Example 3 that did not satisfy the requirements of b) and c), the withstand voltage was low. This was presumed that in Comparative Example 3, the blending ratio was increased without controlling the particle size of the thermally conductive filler, so that voids were generated in the insulating layer and the voltage resistance was lowered.

As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible. This international application claims priority based on Japanese Patent Application No. 2010-53873 filed on March 10, 2010 and Japanese Patent Application No. 2010-75684 filed on March 29, 2010. And the entire contents thereof are incorporated herein.

Claims (12)

An insulating layer having at least one filler-containing polyimide resin layer containing a thermally conductive filler in the polyimide resin;
A metal layer laminated on one or both sides of the insulating layer;
In the thermally conductive laminate having
The content ratio of the heat conductive filler in the filler-containing polyimide resin layer is in the range of 50 to 70 vol%,
The maximum particle size of the thermally conductive filler is less than 15 μm,
The thermally conductive filler contains a plate-like filler and the spherical filler, the plate-like average length D _L is der within the 0.1~2.4μm Rutotomoni filler, the average particle diameter D of the spherical filler _R is in the range of 0.05 to 5.0 μm,
The relationship (A) / (B) between the volume ratio (A) of the plate-like filler in the filler-containing polyimide resin layer and the volume ratio (B) of the spherical filler is in the range of 1 to 15,
A thermal conductive laminate having a thermal conductivity λz in the thickness direction of the insulating layer of 1.0 W / mK or more.   The thermally conductive laminate according to claim 1, wherein a volume ratio of the plate-like filler in the filler-containing polyimide resin layer is larger than a volume ratio of the spherical filler. The plate-like filler is at least one selected from the group consisting of aluminum oxide and boron nitride;
It said spherical filler is aluminum oxide, at least one kind of claim 1 thermally conductive laminate according selected from the group consisting of fused silica and aluminum nitride.   The thermally conductive laminate according to claim 1, wherein the insulating layer has a thickness in a range of 10 to 100 μm and a withstand voltage of 2 kV or more.   The thermally conductive laminate according to claim 1, wherein the thermal expansion coefficient of the insulating layer is in the range of 5 to 30 ppm / K.   The thermally conductive laminate according to claim 1, wherein a content ratio of the thermally conductive filler in the filler-containing polyimide resin layer is within a range of 55 to 65 vol%. In the thermally conductive polyimide film having at least one filler-containing polyimide resin layer containing a thermally conductive filler in the polyimide resin,
The content ratio of the heat conductive filler in the filler-containing polyimide resin layer is in the range of 50 to 70 vol%,
The maximum particle size of the thermally conductive filler is less than 15 μm,
The heat contained and the plate-like filler and spherical filler as conductive filler, wherein the plate-like average length D _L is der within the 0.1~2.4μm Rutotomoni filler, the average particle diameter D of the spherical filler _R is in the range of 0.05 to 5.0 μm,
The relationship (A) / (B) between the volume ratio (A) of the plate-like filler in the filler-containing polyimide resin layer and the volume ratio (B) of the spherical filler is in the range of 1 to 15,
A heat conductive polyimide film having a thermal conductivity λz in the thickness direction of the insulating layer of 1.0 W / mK or more. The thermally conductive polyimide film according to claim 7 , wherein a volume ratio of the plate-like filler in the filler-containing polyimide resin layer is larger than a volume ratio of the spherical filler. The plate-like filler is at least one selected from the group consisting of aluminum oxide and boron nitride;
It said spherical filler is aluminum oxide, at least one thermally conductive polyimide film of claim 7 wherein is selected from the group consisting of fused silica and aluminum nitride. The thermally conductive polyimide film according to claim 7 , wherein the insulating layer has a thickness in a range of 10 to 100 μm and a withstand voltage of 2 kV or more. The thermally conductive polyimide film according to claim 7, wherein the thermal expansion coefficient of the insulating layer is in the range of 5 to 30 ppm / K. The thermally conductive polyimide film according to claim 7 , wherein a content ratio of the thermally conductive filler in the filler-containing polyimide resin layer is within a range of 55 to 65 vol%.