TWI513575B - Thermally conductive polyimide film and a thermally conductive laminate using such thermally conductive polyimide film - Google Patents

Description

Thermally conductive polyimide film and thermally conductive laminate using the same

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

In recent years, the demand for miniaturization and weight reduction of electronic equipment represented by mobile phones, LED lighting fixtures, and parts related to automobile engines has been increasing. A soft circuit board that contributes to miniaturization and weight reduction of the machine can be widely used in the field of electronic technology. Further, a flexible circuit board in which a polyimide resin is used as an insulating layer can be widely used because of its excellent heat resistance and chemical resistance. On the other hand, due to the miniaturization of recent electronic devices, the integration of circuits has been improved, and the speed and reliability of information processing have been increased. The technology for improving the heat dissipation characteristics of heat generated in the machine has been emphasized. .

In order to improve the heat dissipation characteristics of heat generated in an electronic device, it is effective to improve the thermal conductivity of the electronic device. Therefore, a technique of how to include a thermally conductive filler in an insulating layer constituting a circuit board or the like is discussed. More specifically, it is to investigate how a filler having high thermal conductivity such as alumina, boron nitride, aluminum nitride or tantalum nitride can be dispersed and formulated in a resin forming an insulating layer. Further, for example, in Patent Document 1, etc., a technique of blending a thermally conductive filler into a polyimide resin having high heat resistance has been proposed.

Moreover, techniques for formulating a thermally conductive filler in such a resin have been discussed to obtain high thermal conductivity. For example, the proposal of the prior applicant relates to a highly thermally conductive film and a metal foil laminate (PCT/JP2009/065582) in which a plate-shaped thermally conductive filler is combined with a spherical thermally conductive filler and filled with a resin. However, the purpose of the technology proposed in this patent application is mainly applicable to a substrate having flexibility. Therefore, in order to maintain the flexibility of the metal foil laminate, it is necessary to increase the space for the amount of the thermally conductive filler to be a fixed amount or more. At the same time, when a large amount of a filler having a large particle diameter is filled, a stress is generated in the interface between the resin and the filler, and a void is formed in the insulating layer. Therefore, it is also known that the filling amount of the filler has a limit.

When the filling rate of the high thermal conductivity filler is increased or the particle size is increased as described above, a large number of voids are generated in the insulating layer during the formation of the insulating layer, resulting in a problem that the withstand voltage is lowered. In general, when forming an insulating layer containing such a highly thermally conductive filler, a method of applying a resin solution containing a highly thermally conductive filler to a substrate and heat-treating it after drying or the like to form an insulating layer is often employed. In the method of producing a thermally conductive resin sheet, in addition to focusing on the volume ratio, a technique of suppressing generation of voids by compression after drying is also considered (for example, refer to Patent Document 2).

However, the compression of the insulating layer may also affect the insulating layer or other characteristics of the laminated body having the layer due to the conditions.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-162878

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-308576

An object of the present invention is to provide a thermally conductive polyimide film and a thermally conductive laminate using the same, which has heat resistance and dimensional stability even when a large amount of thermally conductive filler is filled in the insulating layer. In addition, it also has excellent thermal conductivity and electrical insulation, and high adhesion to the metal layer.

The thermally conductive laminate of the present invention comprises: an insulating layer having at least one layer of a polyimide-containing resin layer containing a filler; and a metal layer laminated on one or both sides of the insulating layer, and the filler-containing layer The polyimine resin layer is one in which a thermally conductive filler is contained in the polyimide resin. In the thermally conductive laminate, the content of the thermally conductive filler in the polyimine resin layer containing the filler is in the range of 35 to 80 vol%, and the maximum particle diameter of the thermally conductive filler is less than 15 μm. The thermally conductive filler contains a plate-like filler and a spherical filler, and the plate-shaped filler has an average major axis D _L in the range of 0.1 to 2.4 μm, and the thermal conductivity λ _Z of the insulating layer in the thickness direction is 0.8. W/mK or above.

Meanwhile, the thermally conductive polyimide film of the present invention comprises: a film having at least one layer of a polyimide-containing resin layer containing a filler, and the layer of the polyimide-containing resin containing a filler is in a polyimide resin Contains a thermally conductive filler. In the 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%, and the maximum particle size of the thermally conductive filler is less than 15 m, the heat conductive filler contains a plate-like filler and spherical filler, the average long diameter of the plate-shaped filler D _L is in the range 0.1 to 2.4μm, and the thickness direction of the thermally conductive insulating layer The rate λ _Z is 0.8 W/mK or more.

According to the thermally conductive polyimide film and the thermally conductive laminate of the present invention, the polyimide resin which is the matrix of the insulating layer can have excellent heat resistance, dimensional stability, and heat conduction characteristics. At the same time, even when a large amount of the thermally conductive filler is contained in the insulating layer, the occurrence of voids in the insulating layer is suppressed or reduced, and the withstand voltage is also excellent. Further, the thermally conductive polyimide film and the thermally conductive laminate of the present invention are produced by a special step such as coating or heat treatment without a special step such as compression of the insulating layer.

[Formation for implementing the invention] [thermally conductive laminated body]

The thermally conductive laminate of the embodiment of the present invention is composed of an insulating layer and a metal layer provided on one or both sides thereof. The insulating layer is made of a polyimide resin, and at least one layer is a polyimide resin layer containing a filler containing a thermally conductive filler in the polyimide resin. The insulating layer may be formed only of a layer of a polyimide-containing resin containing a filler, or may have a layer of a polyimide resin layer containing no filler. When having a polyimine resin layer containing no filler, the thickness thereof is, for example, in the range of 1/100 to 1/2 of the layer of the polyimide-containing resin containing the filler, and is 1/20 to 1/1 The range of 3 is better. In the case of having a polyimine resin layer containing no filler, if the polyimide layer is bonded to the metal layer, the adhesion between the metal layer and the insulating layer can be 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 polyimine resin layer containing a filler. The volume ratio (also referred to as the content or the content ratio) of the thermally conductive filler in the layer is a total amount of the plate-like filler and the spherical filler to impart excellent thermal conductivity to the thermally conductive laminate. In the range of 80 vol%, it is preferably in the range of 50 to 70 vol%, more preferably in the range of 55 to 65 vol%, and most preferably in the range of 55 to 59 vol%. If the content ratio of the thermally conductive filler is less than 35 vol%, the thermal conductivity is lowered, and sufficient characteristics as a heat dissipating material cannot be obtained. At the same time, if the content of the thermally conductive filler exceeds 80 vol%, the insulating layer becomes brittle, which not only becomes difficult to use, but also varnish when forming an insulating layer from a polyaminic acid solution. The viscosity becomes higher and the workability is lowered.

Meanwhile, in the present invention, in order to suppress or reduce the generation of voids in the insulating layer and to improve the withstand voltage characteristics, it is preferable that the volume ratio (A) of the plate-like filler in the polyimide-containing resin layer containing the filler is larger than the spherical filling. Volume ratio of the agent (B). Specifically, it is preferable that (A)/(B) is in the range of 1 to 15, and it is preferable to be in the range of 1.5 to 15.

Here, the plate-shaped filler refers to a filler having a plate shape or a scaly shape, and the average thickness thereof is less than the average long diameter or the average minor diameter of the surface portion (preferably 1/2 or less). The plate-like filler used in the present invention is a filler having an average long diameter D _L in the range of 0.1 to 2.4 μm. When the average long diameter D _{L is} less than 0.1 μm, the thermal conductivity is lowered, the thermal expansion coefficient is increased, and the effect of the plate shape is reduced. When the average long diameter D _L exceeds 2.4 μm, voids are likely to occur due to stress concentration at the time of film formation. Here, the average long diameter D _L means an average value of the long arm diameters of the plate-shaped filler. Preferable specific examples of the plate-like filler include boron nitride, alumina, and the like. These fillers may be used singly or in combination of two or more. Meanwhile, in terms of high heat conduction, the average long diameter D _{L of the} plate-like filler is preferably in the range of 0.5 to 2.2 μm. The platy filler most suitable for use in the present invention is boron nitride having an average major axis D _{L of} from 1 to 2.2 μm. Meanwhile, the average diameter means the intermediate value diameter, and the mode diameter is preferably 1 of the above range, which is also the same on the spherical filler.

Meanwhile, the spherical filler refers to a filler in which the shape of the filler is spherical and approximately spherical, and the ratio of the average major axis to the average minor axis is 1 or close to 1 (preferably 0.8 or more), which is used in the present invention. The average particle diameter D _{R of the} spherical filler is preferably in the range of 0.05 to 5.0 μm. When the average particle diameter D _{R of the} spherical filler is less than 0.05 μm, the effect of improving thermal conductivity is reduced. Meanwhile, when the average particle diameter D _{R of the} spherical filler exceeds 5 μm, it is difficult to control the spherical filler to fill the interlayer of the plate-like filler or the void due to the contraction of the peripheral resin, which is difficult to control. The effect of the invention. Here, the average particle diameter D _R means an average value (median diameter) of the diameters of the spherical filler particles. Preferable specific examples of the spherical filler include alumina, molten cerium oxide, aluminum nitride, and the like. These fillers may be used singly or in combination of two or more. For example, alumina is excellent in moisture resistance, and aluminum nitride is preferable in that it can impart high thermal conductivity to the insulating layer. Therefore, the material of the spherical filler can be selected according to the use of the thermally conductive laminate, and then combined and used as desired. Meanwhile, in terms of improving the filling property, the average filler particle diameter D _{R of the} spherical filler is preferably in the range of 0.1 to 4.0 μm, and is most suitable for the spherical filler of the present invention, and has an average particle diameter D _R of 0.5 to 3.0. Alumina in the range of μm. Although the thermal conductivity of alumina is not good, this disadvantage can be relieved by using two fillers of a plate-like filler and a spherical filler. However, if it is desired to have a high thermal conductivity, it is preferable to use either or both of the plate-like filler and the spherical filler as a filler other than alumina.

Further, the thermally conductive filler in the present invention may have a thermal conductivity of 5.0 W/m‧K or more. If the thermal conductivity of the thermally conductive filler is less than 5.0 W/m‧K, the heat dissipation effect when it is used as a laminate is reduced.

At the same time, the content ratio of the spherical filler in the thermally conductive filler is preferably in the range of 25 to 70% by weight in terms of both the thermal conductivity and the improvement in the withstand voltage. Further, in the case of having a polyimine resin layer containing no filler, the content of the thermally conductive filler in the entire insulating layer is preferably in the range of 30 to 90% by weight, and preferably 30 to 85% by weight. More preferably at 30 to 60% by weight.

The relationship between the average long diameter D _L and the average particle diameter D _R of the thermally conductive filler is D _L &gt; D _R /2, and a thermally conductive filler containing no more than 30 μm is preferred. If the requirement that the relationship between the average long diameter D _L and the average particle diameter D _R is D _L &gt; D _R /2 is not satisfied, a decrease in thermal conductivity is caused. At the same time, when a thermally conductive filler of 30 μm or more is contained, there is a tendency that the appearance of the surface is unfavorable. The relationship between the average long diameter D _L and the average particle diameter D _R is preferably D _L &_gt; D _R . In the range, it is preferable that D _R is a range of 1/3 to 5/3 of D _L .

In the thermal conductive filler to be used, the filler having a particle diameter of 9 μm or more is preferably 50% by weight or less, and particularly preferably, the ratio of the filler having a particle diameter of 9 μm or more in the plate-like filler is 50% by weight or less. In this way, the unevenness on the surface of the insulating layer can be eliminated to form a smooth surface. Here, the particle diameter in the plate-shaped filler means a long diameter.

Meanwhile, the maximum particle diameter of the thermally conductive filler used in the present invention must be less than 15 μm. When the maximum particle diameter is 15 μm or more, irregularities are formed on the surface of the insulating layer, or voids are easily formed at the interface between the filler and the resin. Here, the maximum particle diameter at the time of a plate-shaped filler means a long diameter. Further, in the above-described thermally conductive filler in the present invention, commercially available products can be appropriately selected.

<insulation layer>

The polyimine resin which is a matrix resin of the insulating layer in the present invention is generally represented by the following general formula (1). Such a polyimide resin is produced by using a substantially monomolar diamine component and an acid dianhydride component, and can be produced by a known polymerization method in an organic polar solvent. At this time, the molar ratio of the acid dianhydride component to the diamine component may also be adjusted so that the viscosity reaches a desired range, and the adjustment range is preferably, for example, a molar ratio range of 0.980 to 1.03.

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. Further, Ar ₁ may be referred to as a residue of an acid dianhydride, and Ar ₂ may be referred to as a residue of a diamine. Meanwhile, n represents the number of repetitions of the constituent unit of the general formula (1), and is preferably 200 or more, and preferably 300 to 1,000.

The acid dianhydride is preferably, for example, an aromatic tetracarboxylic dianhydride represented by O(OC) ₂ -Ar ₁ -(OC)O ₂ , and the following aromatic acid anhydride residue can be exemplified as Ar ₁ .

The acid dianhydride may be used singly or in combination of two or more. Among these acid dianhydrides, it is preferred to use pyromellitic dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3, 3', 4, 4'-benzophenone tetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenylphosphonium tetracarboxylic acid dianhydride (DSDA) and 4,4'-oxydicarboxylic acid dianhydride (ODPA) acid dianhydride.

The diamine is, for example, preferably an aromatic diamine represented by H ₂ N-Ar ₂ -NH ₂ , and the following aromatic diamine residue can be exemplified as an aromatic diamine of Ar ₂ .

Among such diamines, preferred examples thereof include diaminodiphenyl ether (DAPE) and 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB). ), p-phenylenediamine (p-PDA), 1,3-bis(4-aminophenoxy)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).

The solvent used in the polymerization of the diamine component and the acid dianhydride component may, for example, be dimethylacetamide, N-methylpyrrolidone, 2-butanone or diethylene glycol dimethyl dimethyl ether (diglyme). In the case of xylene or the like, one type of these solvents may be used, or two or more types may be used at the same time. Meanwhile, the resin viscosity of the poly-proline (polyimine precursor) obtained by the polymerization is preferably in the range of 500 cps to 35,000 cps, and particularly preferably in the range of 1,000 cps to 10,000 cps.

The method of forming the insulating layer of the thermally conductive laminate of the present invention is not particularly limited, and a known method can be employed. Here is the most representative method of illustration. First, a resin solution of a polyamic acid containing a thermally conductive filler as a raw material of an insulating layer is directly cast-coated on a metal foil such as a copper foil as a metal layer to form a coating film. Here, poly-proline is a precursor resin of polyimine. Next, a part of the solvent of the coating film is dried and removed at a temperature of 150 ° C or lower. Then, for the coating film, heat treatment is performed for about 5 to 30 minutes at 100 to 400 ° C in a temperature range of preferably 130 to 360 ° C for further oxime imidization. Thus, an insulating layer made of a polyimide resin containing a thermally conductive filler can be formed on the metal layer. If the insulating layer is a layer of two or more polyimide layers, the second polyamic acid resin solution may be coated after the first polyamic acid resin solution is applied and dried. Cloth, dry. Thereafter, the resin solution of the poly-proline acid for the third time, and then the resin solution of the poly-proline for the fourth time, the resin solution of the poly-proline is sequentially coated as required. ,dry. Then, after finishing, heat treatment is carried out at a temperature ranging from 100 to 400 ° C for about 5 to 30 minutes to imidize the oxime. If the temperature of the heat treatment is lower than 100 ° C, the dehydration ring-closure reaction of the polyimide may not be sufficiently carried out. Conversely, if the temperature exceeds 400 ° C, the polyimine resin and the copper foil may be deteriorated due to oxidation or the like. .

Meanwhile, another example of forming an insulating layer is mentioned. First, a resin solution of a polyacrylic acid containing a thermally conductive filler as a raw material of an insulating layer is cast-coated on an arbitrary supporting substrate to be formed into a film shape. After heating and drying on the support, the film-like formed product can be made into a self-supporting gel film. Then, after the film is peeled off from the support, heat treatment is performed at a high temperature to imidize the oxime to obtain a polyimide film. In the case of forming a thermally conductive laminated body in which the polyimide film is formed as an insulating layer, a general method is, for example, a method of heating and plating a metal foil directly on a polyimide film or through an adhesive; or A method of forming a metal layer on a polyimide film by metal evaporation or the like.

In the case of preparing a resin solution of a polyacrylic acid containing a thermally conductive filler in the formation of the above-mentioned insulating layer, for example, a thermally conductive filler can be directly formulated in a resin solution of polyamic acid. Alternatively, after considering the dispersibility of the filler, the thermal conductive filler may be prepared in advance in a reaction solvent of a component of the raw material (acid dianhydride component or diamine component) of the resin solution into which the polyaminic acid has been charged. Then, another raw material component was put in and stirred to carry out polymerization. When directly arranging, the full amount of the filler can be put in one at a time, or it can be divided into several times and added in a small amount. At the same time, the raw materials of the resin solution may be added all at once, or may be divided into several times and mixed in a small amount.

The insulating layer may be composed of a single layer or a plurality of layers. For example, in order to obtain the dimensional stability of the thermally conductive laminate or the adhesion strength to the copper foil, a plurality of layers can be formed. In this case, when the insulating layer is formed as a plurality of layers, it is preferable to include a thermally conductive filler in all of the layers in consideration of thermal conductivity. However, by forming the adjacent layer of the polyimine resin layer containing the filler as a layer containing no filler or by forming a layer having a low content, it is possible to have an advantageous effect of preventing the filler from slipping during processing or the like. Further, the present invention does not use an adhesive which can bond the polyimide-containing resin layer containing a filler to the metal foil. However, when the thermal conductive laminate having a metal layer on both sides of the insulating layer is interposed with an adhesive, the thickness of the adhesive layer is less than 30 of the thickness of the entire insulating layer without damaging the thermal conductivity as much as possible. % is better, and it is better when it is less than 20%. Meanwhile, if the thermal conductive laminate having a metal layer on only one side of the insulating layer is interposed with an adhesive, the thickness of the adhesive layer is less than 15% of the thickness of the entire insulating layer without impairing thermal conductivity. Time is better, and it is better when it is less than 10%. Further, since the adhesive layer is a partial structure of the insulating layer, it is preferably a polyimide film. The glass transition temperature of the polyimide resin which is a main material of the insulating layer is preferably 300 ° C or more from the viewpoint of imparting heat resistance. When the glass transition temperature is 300 ° C or higher, the above-mentioned acid dianhydride or diamine component constituting the polyimine resin must be appropriately selected.

In the thermally conductive laminate of the present invention, the thickness of the insulating layer is preferably in the range of, for example, 10 to 100 μm, and preferably in the range of 12 to 50 μm. When the thickness of the insulating layer is less than 10 μm, in the step of transporting the thermally conductive laminate, it is easy to cause wrinkles or the like on the gold foil. On the other hand, when the thickness of the insulating layer exceeds 100 μm, there is a tendency that the appearance or the bendability of high thermal conductivity is disadvantageous. The withstand voltage of the insulating layer is preferably 2 kV or more.

The coefficient of thermal expansion (CTE) of the insulating layer is preferably in the range of, for example, 5 × 10 ^-6 to 30 × 10 ^-6 /K (5 to 30 ppm / K), and is 10 × 10 ^-6 to 25 × 10 ^-6 / It is preferably in the range of K (10 to 25 ppm/K). When the thermal expansion coefficient of the insulating layer is less than 5 × 10 ^-6 /K, the heat conductive laminated body is formed, and curling is likely to occur, and workability is deteriorated. On the other hand, when the thermal expansion coefficient of the insulating layer exceeds 30 × 10 ^-6 /K, dimensional stability of an electronic material such as a flexible substrate is deteriorated, and heat resistance tends to be lowered.

The thermal conductivity λ _Z of the insulating layer of the present invention in the thickness direction must be 0.8 W/mK or more, more preferably 1.0 W/mK or more, and more preferably 1.5 W/mK or more. When the thermal conductivity λ _{Z is} less than 0.8 W/mK, the heat conductive layered body of the present invention which is mainly used for heat dissipation use cannot achieve its purpose. Under the thermal conductivity characteristics and other constituent elements, a thermally conductive laminate that satisfies other characteristics at the same time can be obtained. In particular, when the thermal conductivity λ _Z is 1.0 W/mK, excellent heat dissipation characteristics can be obtained, and it can be used as, for example, a heat dissipation substrate, and can be used as a heat conductive laminate suitable for various applications. Meanwhile, the thermal conductivity of the insulating layer is preferably 1.0 W/mK or more in the planar direction, and more preferably 2.0 W/mK or more.

As described above, the thermally conductive laminate of the present invention may have a metal layer only on one side of the insulating layer, or may have a metal layer on both sides of the insulating layer. Further, the thermally conductive laminated body having the metal layer on both sides may be formed by, for example, forming a laminated body of a single-sided metal layer, and then bonding the polyimide layers to each other and then die-casting by a hot press, or It is obtained by a method of forming a metal foil by laminating a polyimide foil of a laminate of a single-sided metal layer.

<metal layer>

The metal layer may be a layer formed of a metal foil as described above or a layer obtained by vapor-depositing a metal on the film. At the same time, the polyimide-containing precursor containing the thermally conductive filler can be directly coated, and the metal foil or the metal plate can be a metal layer, of which copper foil or copper plate is preferred. The thickness of the metal layer is preferably in the range of, for example, 5 μm to 3 mm, and more preferably in the range of 12 μm to 1 mm. When the thickness of the metal layer is less than 5 μm, it may easily cause wrinkles or the like during transportation of a laminated substrate or the like. On the other hand, when the thickness of the metal layer exceeds 3 mm, the workability is deteriorated because it is too hard. In terms of the thickness of the metal layer, it is generally suitable for in-vehicle use, and in the case of LED use, it is preferably a thin metal layer.

[Thermal conductive polyimide film]

The thermally conductive polyimide film according to the embodiment of the present invention is the same as the insulating layer in the thermally conductive laminate of the present invention. For details, refer to the insulating layer in the thermally conductive laminate of the present invention. Description. In other words, the film of the insulating layer obtained by removing the metal layer from the thermally conductive laminate described above has the same configuration as the thermally conductive polyimide film of the present invention. Meanwhile, the thermally conductive laminate of the present invention can also be said to have a thermal conductive polyimide film of the present invention as a laminate of an insulating layer.

In the method for producing a thermally conductive laminate, it has been described that the formation of the insulating layer can be performed by forming a metal layer as a supporting substrate and forming an insulating layer thereon, but it is used in the production of the thermally conductive polyimide film of the present invention. The support substrate is not particularly limited, and a substrate of any material can be used. At the same time, in the formation of the thermally conductive polyimide film, it is not necessary to form a resin film which has been completely polyimidized on the substrate. For example, the resin film in the semi-hardened polyimine precursor state may be separated from the support substrate, and after separation, the ruthenium imidization may be completed to form a thermally conductive polyimide film. In addition to the above description, as described above, since the description of the insulating layer in the thermally conductive laminate of the present invention can be referred to, the description thereof will be omitted.

[Examples]

Hereinafter, the present invention is specifically described in accordance with the embodiments, but the scope of the present invention is not limited to the embodiments.

The abbreviations used in this embodiment are as follows.

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

Meanwhile, the characteristics evaluated in the examples were evaluated in accordance with the following evaluation methods.

[Thickness direction thermal conductivity (λ _Z )]

The film (insulation film, the same applies hereinafter) of the measurement object was cut into a size of 20 mm × 20 mm, and the thermal diffusivity in the thickness direction by the Laser Flash method (LFA 447 Nanoflash device manufactured by Bruker AXS) was applied. After measuring the specific heat of the DSC (differential scanning calorimetry) and the density of the applied gas substitution method, the thermal conductivity was calculated from the results.

[Coefficient of Thermal Expansion (CTE)]

In a thermomechanical analyzer (TMA), a 3 mm × 15 mm insulating film is added to a load of 5 g while a tensile test is carried out at a fixed temperature increase rate (20 ° C / min) from 30 ° C to 260 ° C. The coefficient of thermal expansion (ppm/K) was determined from the elongation of the insulating film with respect to temperature.

[Glass transfer temperature (Tg)]

In a dynamic thermomechanical analyzer, the dynamic viscoelasticity of the insulating film (10 mm × 22.6 mm) at a temperature of 20 ° C to 500 ° C at 5 ° C / min was measured, and the glass transition temperature (tan δ maximum value: ° C) was determined.

[Continue strength]

When the copper foil and the resin layer are adhered to a level that can withstand the sample processing (circuit processing) when the withstand voltage is measured, the sample is ○ (good), and the resin layer is peeled off from the copper foil during processing or evaluation. The sample at the time was × (bad). Meanwhile, the adhesion force of Examples 4 to 6 was that a resin tester of a copper foil having a width of 1 mm was fixed on an aluminum plate with a double-sided tape using a tension tester, and copper was 50 mm/min in a 180° direction. After the speed was peeled off, the peel strength was obtained.

[withstand voltage]

The thermally conductive laminate was cut into a size of 5 cm × 5 cm, and the single-sided copper foil was processed into a circular shape having a diameter of 2 cm, and the unnecessary portion was removed by a copper foil etching solution. According to JIS C2110, the TOS 5101 device manufactured by KIKUSUI was used to measure the withstand voltage in the insulating oil by the application phase boosting method. The voltage was raised in the 0.2 kV scale phase, maintained for 20 seconds in each voltage, and the leakage current was set to 8.5 mA, and one value before the broken voltage was used as the initial withstand voltage. The size of the electrode is 2 cmφ. After the sample was kept in an environment of 120 ° C / 95 RH % humidity for 24 hours, the withstand voltage measured was taken as the withstand voltage after moist heat.

Synthesis Example 1

M-TB (12.4591 g, 0.0587 mol) and DAPE (9.6152 g, 0.0480 mol) were stirred in a 500 ml separation flask under a nitrogen gas stream, and dissolved in 255 g of DMAc. Next, PMDA (22.9258 g, 0.1051 mol) was added to this solution. Then, the solution was continuously stirred at room temperature for 3 hours to carry out polymerization to obtain a brownish-colored viscous polyamine solution (P1).

Synthesis Example 2

BAPP (23.2045 g, 0.0565 mol) was stirred in a 500 ml separation flask under a nitrogen gas stream, and dissolved in 264 g of DMAc. Next, PMDA (11.9473 g, 0.0548 mol) and BPDA (0.8482 g, 0.0029 mol) were added. Then, the solution was continuously stirred at room temperature for 3 hours to carry out polymerization to obtain a brownish-colored viscous polyamine solution (P2).

Synthesis Example 3

Under a nitrogen gas stream, m-TB (19.1004 g, 0.08997 mol) and TPE-R (2.9224 g, 0.0100 mol) were stirred in a 500 ml separation flask while being dissolved in 255 g of DMAc. Next, PMDA (17.1827 g, 0.07878 mol) was added, and after stirring for 10 minutes, BPDA (5.7944 g, 0.0197 mol) was added. Then, the solution was continuously stirred at room temperature for 4 hours to carry out a polymerization reaction to obtain a brownish-colored viscous polyamine solution (P3).

Example 1

65.242 g of polyamic acid solution (P1), commercially available boron nitride (scaly shape, average long diameter 2.2 μm, maximum particle diameter 11 μm) as a plate-like filler, 18.16 g as a spherical filler, and a spherical filler Commercially available alumina (spherical, average particle diameter 3 μm, maximum particle diameter 10 μm) 3.55 g was mixed until homogeneous. Then, DMAc 13.048 g was added to adjust the viscosity, and the mixture was mixed until uniform by a centrifugal stirrer to obtain a polyamine acid solution (P4) containing a thermally conductive filler.

On the electrolytic copper foil having a thickness of 35 μm, a polyamine acid solution (P2) not filled with a filler was applied so as to have a thickness of 2.0 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Next, a polyamic acid solution (P4) containing a thermally conductive filler mixed with a plate-like filler and a spherical filler was applied so as to have a thickness of 22 μm after hardening, and dried by heating at 130 ° C to remove Solvent. Further, on the same, a polyacrylic acid solution (P2) to which a filler was not formulated was applied so as to have a thickness of 2.0 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Then, in a temperature range of 130 to 300 ° C, after heating at a stepwise temperature of 20 minutes, a thermally conductive laminate M1 having an insulating layer made of a three-layer polyimide layer on a copper foil was prepared (P2). /P4/P2).

In order to evaluate the characteristics of the insulating layer of the thermally conductive laminate M1, an insulating film was formed by etching and removing the copper foil, and the thermal conductivity, CTE, and Tg were evaluated. The results are shown in Table 2. Then, the bonding strength of the metal-insulating resin layer in the thermally conductive laminate, the initial voltage, and the withstand voltage after the moist heat were measured. The results are shown in Table 3.

Further, the insulating film and the thermally conductive laminate obtained in the examples and comparative examples shown below were also evaluated in the same manner as in Example 1 unless otherwise specified.

Example 2

54.092 g of the polyaminic acid solution (P1), 12.71 g of the same boron nitride as the plate-like filler as the plate-like filler, and 22.38 g of the same alumina as the example 1 as the spherical filler were mixed by a centrifugal mixer. To even. Then, DMAc 10.818g was added to adjust the viscosity, and the mixture was mixed until uniform by a centrifugal mixer to obtain a polyacrylic acid solution (P5) containing a thermally conductive filler.

Using a copper foil having a thickness of 500 μm, the same operation as in Example 1 was carried out to prepare a thermally conductive laminate M2 (P2/P5/P2) having a thickness of 2.0 μm/24 μm/2.0 μm after curing.

Using the obtained thermally 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 thermally conductive laminate was also evaluated. The individual evaluation results are shown in Table 2 and Table 3.

Example 3

78.98 g of a polyaminic acid solution (P2), 17.58 g of the same boron nitride as the plate-like filler as in the form of a plate-like filler, and 3.44 g of the same alumina as in Example 1 as a spherical filler were mixed by a centrifugal mixer. After homogenization, a polyaminic acid solution (P6) containing a thermally conductive filler was obtained.

Using a copper foil having a thickness of 35 μm, the same operation as in Example 1 was carried out to prepare a thermally conductive laminated body M3 (P2/P6/P2) having a thickness of 2.0 μm/21 μm/2.0 μm after curing.

Comparative example 1

86.96 g of polyamic acid solution (P3), boron nitride (commercial product: scaly, average long diameter: 4.5 μm, maximum particle diameter: 20 μm) as a plate-like filler, 6.52 g, and as a spherical filling After the agent 6.52 g of the same alumina as in Example 1 was mixed and homogenized, a polyamine acid solution (P7) containing a thermally conductive filler was obtained.

The copper foil having a thickness of 12 μm was used in the same manner as in Example 1 to prepare a thermally conductive laminate M4 (P2/P7/P2) having a thickness of 2.0 μm/21 μm/2.0 μm after curing.

Comparative example 2

86.96 g of polyamic acid solution (P3), boron nitride (commercial product: scaly, average long diameter 2.5 μm, maximum particle diameter 11 μm) as a plate-like filler, 6.52 g, and spherical filling After the agent 6.52 g of the same alumina as in Example 1 was mixed and homogenized, a polyacrylic acid solution (P8) containing a thermally conductive filler was obtained.

Using a copper foil having a thickness of 12 μm, the same operation as in Example 1 was carried out to prepare a thermally conductive laminate M5 (P2/P8/P2) having a thickness of 2.0 μm/21 μm/2.0 μm after curing.

Comparative example 3

61.467 g of a polyaminic acid solution (P3), 9.50 g of boron nitride which is the same as that of Comparative Example 1 as a plate-like filler, and 16.74 g of alumina which is the same as that of Example 1 as a spherical filler were mixed by a centrifugal mixer. After uniformization, 12.293 g of DMAc was added to adjust the viscosity, and the mixture was mixed until uniform by a centrifugal mixer to obtain a polyacrylic acid solution (P9) containing a thermally conductive filler.

Using a copper foil having a thickness of 12 μm, the same operation as in Example 1 was carried out to prepare a thermally conductive laminate M6 (P2/P9/P2) having a thickness of 2.0 μm/20 μm/2.0 μm after curing.

Synthesis Example 4

Under a nitrogen gas stream, m-TB (10.38 g, 0.049 mol) and DAPE (8.01 g, 0.040 mol) were stirred in a 500 ml separation flask while being dissolved in 262.50 g of DMAc. Next, PMDA (19.10 g, 0.088 mol) was added. Then, the solution was continuously stirred at room temperature for 3 hours to carry out polymerization to obtain a brownish-colored viscous polyamine solution (P10).

Synthesis Example 5

Under a nitrogen gas stream, BAPP (23.20 g, 0.057 mol) was stirred in a 500 ml separation flask while being dissolved in 264 g of DMAc. Next, PMDA (11.9473 g, 0.0548 mol) and BPDA (0.8482 g, 0.0029 mol) were added. Then, the solution was continuously stirred at room temperature for 3 hours to carry out polymerization to obtain a brownish-colored viscous polyamine solution (P11).

Example 4

In a centrifugal mixer, 72.71 g of a polyglycine solution (P10) having a solid concentration of 12.5 wt% and a classifier as a plate-like filler were used to remove boron nitride of particles exceeding 11 μm (manufactured by Electric Chemical Industry Co., Ltd.). Name: SP-3', scaly, average long diameter 2.2 μm) 7.49 g and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle diameter 3 μm, 19.80 g of the maximum particle diameter of 11 μm) was mixed until uniform, and a polyacrylic acid solution (P10') containing a thermally conductive filler was obtained.

On the electrolytic copper foil having a thickness of 35 μm which had been subjected to rustproof treatment, a polyamine acid solution (P11) not filled with a filler was applied so as to have a thickness of 1.5 μm after hardening, and dried by heating at 130 ° C. To remove the solvent. Then, a polyamic acid solution (P10') containing the above thermally conductive filler was applied thereto so as to have a thickness of 21 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Further, on the above, a polyacrylic acid solution (P11) not filled with a filler was applied so as to have a thickness of 1.5 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Then, in a temperature range of 130 to 300 ° C, the stepwise heating is carried out for 20 minutes, and then a thermally conductive laminated body M7 having an insulating layer made of a three-layer polyimide layer on a copper foil is produced. (P11/P10'/P11). The insulating layer constitution in this thermally conductive laminate M7 is as shown in Table 4.

In order to evaluate the characteristics of the insulating layer (film) in the obtained thermally conductive laminate M7, an insulating film (F3) was formed by etching and removing a copper foil, and CTE, tear propagation resistance, glass transition temperature, and Evaluation of thermal conductivity. The results are shown in Table 5. Further, the bonding strength between the insulating layer and the copper foil in the thermally conductive laminate M7 was as shown in Table 6.

At the same time, on the heat-resistant resin layer of the obtained thermally conductive laminated body M7, the electrodeposited copper foil having a thickness of 12 μm which has been subjected to the rust-preventing treatment is hot-pressed at a temperature of up to 380 ° C to obtain a thermally conductive laminated body M7' of a double-sided metal. . It is used for withstand voltage measurement. The results are shown in Table 6.

Example 5

A 74.54 g of a polyglycine solution (P11) having a solid content of 12.0% by weight in a centrifugal mixer was used to remove boron nitride in excess of 11 μm by a classifier as a plate-like filler (manufactured by Electric Chemical Industry Co., Ltd.). Name: SP-3', scaly, average long diameter 2.2 μm) 9.22 g and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle diameter 3 μm, After the maximum particle diameter of 11 μm) and 16.24 g were mixed, the polyamic acid resin solution (P11') containing the thermally conductive filler was obtained.

On the electrolytic copper foil having a thickness of 35 μm to which rustproof treatment has been applied, a polyamine acid solution (P11) not filled with a filler is applied so as to have a thickness of 1.5 μm after hardening, and dried by heating at 130 ° C. Remove solvent. Then, a polyamic acid solution (P11') containing the above thermally conductive filler was applied thereto so as to have a thickness of 21 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Further, on the above, a polyacrylic acid solution (P11) not filled with a filler was applied so as to have a thickness of 1.5 μm after hardening, and dried by heating at 130 ° C to remove the solvent. Then, in a temperature range of 130 to 300 ° C, the stepwise heating was carried out for 20 minutes, and then a thermally conductive laminate M8 having an insulating layer composed of a three-layer polyimide layer on the copper foil was produced. The composition of the insulating layer in this thermally conductive laminate M8 is as shown in Table 4.

In order to evaluate the characteristics of the insulating layer (film) in the obtained thermally conductive laminate M8, an insulating film (F4) was formed by etching and removing a copper foil, and CTE, tear propagation resistance, glass transition temperature, and thermal conductivity were evaluated. The results are shown in Table 5. Further, the adhesion strength between the insulating layer and the copper foil in the thermally conductive laminate M8 was measured, and the results are shown in Table 6.

At the same time, on the heat-resistant resin layer of the obtained heat-conductive laminated body M8, the electrodeposited copper foil having a thickness of 12 μm which was subjected to rust-proof treatment was hot-pressed at a temperature of up to 380 ° C to obtain a thermally conductive laminated body M8' having a double-sided metal. It is used for withstand voltage measurement. The results are shown in Table 6.

Example 6

In a centrifugal mixer, 57.60 g of a polyglycine solution (P10) having a solid concentration of 12.5 wt% and a classifier as a plate-like filler were used to remove boron nitride exceeding 11 μm (manufactured by Electric Chemical Industry Co., Ltd., a product Name: SP-3', scaly, average long diameter 2.2 μm) 15.7 g and alumina as a spherical filler (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3, spherical, average particle diameter 3 μm, After the maximum particle diameter of 11 μm) was mixed to 3.1 g, a polyamic acid solution (P10") containing a thermally conductive filler was obtained.

On the electrolytic copper foil having a thickness of 35 μm to which rustproof treatment has been applied, a polyamine acid solution (P11) not filled with a filler is applied so as to have a thickness of 1.5 μm after hardening, and dried by heating at 130 ° C. Remove solvent. Then, a polyamic acid solution (P10") containing the above thermally conductive filler was applied thereto so as to have a thickness of 23 μm after hardening, and dried by heating at 130 ° C to remove the solvent. A polyamine acid solution (P11) not prepared with a filler was applied in such a manner that the thickness after hardening became 1.5 μm, and dried by heating at 130 ° C to remove the solvent. Then, in a temperature range of 130 to 300 ° C, After heating at a stepwise temperature for 20 minutes, a thermally conductive laminate M9 having an insulating layer composed of a three-layer polyimide layer on a copper foil is formed. The composition of the insulating layer in the thermally conductive laminate M9 It is as shown in Table 4.

In order to evaluate the characteristics of the insulating layer (film) in the obtained thermally conductive laminate M9, an insulating film (F5) was formed by etching and removing a copper foil, and CTE, tear propagation resistance, glass transition temperature, and thermal conductivity were evaluated. The results are shown in Table 5. Further, the adhesion strength between the insulating layer and the copper foil in the thermally conductive laminate M9 was measured, and the results are shown in Table 6.

At the same time, on the heat-resistant resin layer of the obtained thermally conductive laminated body M9, the rust-prevented electrolytic copper foil edge having a thickness of 12 μm is hot-pressed at a temperature of up to 380 ° C to obtain a thermally conductive laminated body M9 having a double-sided metal. '. It is used for withstand voltage measurement. The results are shown in Table 6.

Example 7

79.5 g of a polyglycine solution (P10) having a solid concentration of 12.5 wt%, and a boron nitride having a particle size exceeding 11 μm as a plate-like filler by a centrifugal mixer (manufactured by Electric Chemical Industry Co., Ltd.) Name: SP-3', scaly, average long diameter 2.2 μm) 8.4 g and aluminum nitride as a spherical filler (manufactured by Toyama Co., Ltd., trade name: A1N-H, spherical, average particle diameter After 1.1 μg of 1.1 μg was mixed until homogeneous, a polyaminic acid solution (P10'') containing a thermally conductive filler was obtained.

The polyacrylic acid solution (P10'') containing the above-mentioned thermally conductive filler was applied to the electrolytic copper foil having a thickness of 35 μm to which the rust-preventing treatment was applied so as to have a thickness of 25 μm after the curing, and was carried out at 130 ° C. Heat to dry to remove the solvent. Then, in a temperature range of 130 to 300 ° C, the stepwise heating is carried out for 20 minutes, and then a thermally conductive layered product M10 having an insulating layer composed of a layer of a polyimide layer on a copper foil is produced. The composition of the insulating layer in this thermally conductive laminate M10 is as shown in Table 4.

In order to evaluate the characteristics of the insulating layer (film) in the obtained thermally conductive laminate M10, an insulating film (F6) was formed by etching and removing a copper foil, and CTE, tear propagation resistance, glass transition temperature, and thermal conductivity were evaluated. The results are shown in Table 5. Further, the bonding strength between the insulating layer and the copper foil in the thermally conductive laminate M10 was as shown in Table 6.

At the same time, on the heat-resistant resin layer of the obtained thermally conductive laminated body M10, the rust-prevented electrolytic copper foil edge having a thickness of 12 μm was hot-pressed at a temperature of up to 380 ° C to obtain a thermally conductive laminated body M10' of a double-sided metal. . It is used for withstand voltage measurement. The results are shown in Table 6.

From the above results, at least: a) the content of the thermally conductive filler in the polyimine resin layer containing the filler is in the range of 35 to 80 vol%; b) the maximum particle diameter of the thermally conductive filler is not Up to 15 μm; c) the thermally conductive filler contains a plate-like filler and a spherical filler, and the average long diameter D _{L of the} plate-like filler is in the range of 0.1 to 2.4 μm, and the heat conduction of the embodiments 1 to 7 of the element The thermal laminate and the thermally conductive polyimide film have excellent heat conduction characteristics in addition to the heat resistance and dimensional stability of the polyimide resin having a matrix which serves as an insulating layer. At the same time, since the occurrence of voids in the insulating layer can be suppressed or reduced, the withstand voltage is also excellent. Further, the thermally conductive polyimide film and the thermally conductive laminate of Examples 1 to 7 do not require a special step such as compression of the insulating layer, and can be produced by a usual coating or heat treatment. Therefore, the characteristics required for the insulating layer as a circuit board or the like are not impaired, and thus it is applicable to various electronic devices.

On the other hand, in Comparative Example 1 which cannot satisfy the requirements of the above a) to c) and Comparative Example 2 which does not satisfy the requirements of the above a), the thermal conductivity λ _Z in the thickness direction of the insulating layer is less than 0.8 W/mK. As a result, the thermal conductivity is low. Further, in Comparative Example 3 which did not satisfy the requirements of the above b) and c), the voltage resistance was low. It is presumed that this is because the particle size of the thermally conductive filler is not controlled in Comparative Example 3, and the blending ratio is large, and voids are generated in the insulating layer, so that the withstand voltage is lowered.

Although the above described exemplary embodiments of the present invention have been described in detail, the present invention is not limited to the embodiments described above, and various modifications are possible. The international application of the present invention claims the priority of Japanese Patent Application No. 2010-53873, filed on March 10, 2010, and Japanese Patent Application No. 2010-75684, filed on March 29, 2010. The medium aid uses all of its contents.

Claims (12)

A thermally conductive laminated body comprising: an insulating layer having at least one layer of a polyimide-containing resin layer containing a filler; and a metal layer laminated on one or both sides of the insulating layer, and the filler-containing polyfluorene The imide resin layer contains a thermally conductive filler in the polyimide resin, and the ratio of the thermally conductive filler contained in the polyimine resin layer containing the filler is in the range of 50 to 70 vol%. the maximum particle size, the heat conductive filler of less than 15 m, the heat conductive filler contains a plate-like filler and spherical filler, the average long diameter of the plate-shaped filler D _L is in the range of 0.1 to 2.4μm And the average particle diameter D _R of the spherical filler is in the range of 0.05 to 5.0 μm, and the volume ratio (A) of the plate-shaped filler in the filler-containing polyimide resin layer is the same as the foregoing The relationship (A)/(B) of the volume ratio (B) of the spherical filler is in the range of 1 to 15, and the thermal conductivity λ _z in the thickness direction of the insulating layer is 1.0 W/mK or more. The thermally conductive laminate according to claim 1, wherein a volume ratio of the plate-shaped filler in the filler-containing polyimide resin layer is larger than a volume ratio of the spherical filler. The thermally conductive laminate according to claim 1, wherein the plate-shaped filler is at least one selected from the group consisting of alumina and boron nitride, and the spherical filler is selected from the group consisting of alumina. , molten cerium oxide and nitrogen At least one of the group of aluminum. The thermally conductive laminate according to claim 1, wherein the insulating layer has a thickness of 10 to 100 μm and a withstand voltage of 2 kV or more. The thermally conductive laminate according to claim 1, wherein the insulating layer has a thermal expansion coefficient in the range of 5 to 30 ppm/K. The thermally conductive laminate according to the first aspect of the invention, wherein the content of the thermally conductive filler in the polyimine resin layer containing the filler is in the range of 55 to 65 vol%. A thermally conductive polyimide film comprising: a film having at least one layer of a polyimide-containing resin layer containing a filler, and the polyimide-containing resin layer containing a filler contains thermal conductivity in a polyimide resin In the filler, the content of the thermally conductive filler in the filler-containing polyimide resin layer is in the range of 50 to 70 vol%, and the maximum diameter of the thermally conductive filler is less than 15 μm. the heat conductive filler contains a plate-like filler and spherical filler, and the average long diameter D _L of the plate-shaped filler is in the range 0.1 to 2.4μm, and the average particle size of said spherical filler D _R The relationship 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 in the range of 0.05 to 5.0 μm (A) And (B) in the range of 1 to 15, the thermal conductivity λ _z in the thickness direction of the film is 1.0 W/mK or more. The thermally conductive polyimide film according to claim 7, wherein the volume ratio of the plate-shaped filler in the filler-containing polyimine resin layer is larger than the volume of the spherical filler ratio. The thermally conductive polyimide film according to claim 7, wherein the plate-shaped filler is at least one selected from the group consisting of alumina and boron nitride, and the spherical filler is selected. At least one of a group of free alumina, molten cerium oxide, and aluminum nitride. The thermally conductive polyimide film according to claim 7, wherein the film has a thickness in the 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 film has a coefficient of thermal expansion in the range of 5 to 30 ppm/K. The thermally conductive polyimide film according to claim 7, wherein the content of the thermally conductive filler in the polyimine resin layer containing the filler is in the range of 55 to 65 vol%. .