JP2020113597A - Circuit board, manufacturing method thereof, and semiconductor device - Google Patents

Abstract

To provide a circuit board having an insulating film capable of suppressing the generation of a leak current at the end of a circuit.SOLUTION: A circuit board includes a circuit and an insulating substrate supporting the circuit, and at least a part of an end portion of a circuit on the insulating substrate side is covered with an insulating film, and the insulating film includes a dry coating film or a cured coating film of a coating material including an insulating resin and a resin filler having an average particle size of 0.1 to 5.0 μm.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a circuit board, a manufacturing method thereof, and a semiconductor device.

In the field of semiconductor devices, the power density is increasing year by year with the miniaturization of packages and the increase in current. Leakage current is likely to occur due to the increase in power density, which may make it difficult to secure the insulation reliability of the semiconductor device. Therefore, higher insulation is required between the circuits of the circuit board, the creepage of the circuit board, and the like, where leak current is likely to occur.

As a method for ensuring the insulation between the circuits of the circuit board and the creepage, it is conceivable to widen the gap between the circuits and widen the edge of the insulating board that supports the circuit board. However, these methods hinder the miniaturization of the package.

On the other hand, in order to achieve both the miniaturization of the package and the insulating property, in the insulating substrate that supports the metal circuit, the entire surface or a part of the surface of the insulating substrate extending from the end of the metal circuit is coated with a coating material. There has been reported a method of applying an insulating property by applying (Patent Document 1). Patent Document 1 clarifies that a polyimide resin, an epoxy resin, and a material obtained by adding an inorganic filler to these resins are used as a coating material, and a coating film is provided at a predetermined portion to suppress the generation of leak current. ing.

JP, 2005-116602, A

In a package with high power density, in order to sufficiently suppress the leakage current between the circuits of the circuit board and in the creeping surface of the circuit board, a coating that can be applied with high precision to a predetermined part and has excellent shape retention after application. Materials are needed. The coating material also needs to be able to form a film having excellent insulating properties. However, there is no conventional coating material that can sufficiently satisfy such a demand, and further improvement is desired.

For example, when a polyimide resin is used as a coating material, generally, a polyimide resin or a precursor thereof, polyamic acid, is applied in the form of a varnish dissolved in a solvent and cured to form a film. However, in general, a varnish (coating material) of a polyimide resin has low thixotropy and low viscosity.
When the varnish has a low viscosity, the shape retention after coating is poor and the varnish easily flows. As a result, problems such as the inability to form a target film thickness and application to unintended locations are likely to occur. On the other hand, when the varnish has a high viscosity and a low thixotropic property, the pressure loss is large in the varnish supply step and the coating step with the dispenser, and the coating itself becomes difficult.

As a general method for achieving both the shape-retaining property and the coating property, it is possible to add thixotropy to the coating material. Due to the thixotropic property of the coating material, the coating material has a low viscosity when external force is applied, such as during preparation and during dispensing application. On the other hand, in the state where no external force is applied to the coating material after application, the viscosity becomes high and the shape can be maintained. From such a viewpoint, it is desirable that the coating material has appropriate thixotropy.

On the other hand, as a method for imparting thixotropy to a coating material, it is generally known to add an inorganic filler such as silica filler to a base resin. However, when an inorganic filler is added, the filler is present in the coating film after curing, so that when a voltage is applied, it is easy to energize along the filler in the coating film, and the dielectric breakdown voltage of the film is likely to decrease.

As described above, the conventional coating materials are not sufficiently satisfying various demands, and further improvement is desired. In particular, in order to improve the power density of a package in recent years, a coating material that can further enhance the insulation reliability of the package is desired.
Therefore, in view of the above situation, the present disclosure provides a coating material that can be applied to a predetermined portion with high accuracy, is excellent in shape retention after application, and can form a film having an excellent dielectric breakdown voltage. Provided is a circuit board which is used and in which generation of leakage current is suppressed. Further, a semiconductor device having excellent insulation reliability is provided by using such a circuit board.

Although the embodiments of the present invention relate to the following, the present invention is not limited to the following and includes various embodiments.

One embodiment comprises a circuit and an insulating substrate supporting the circuit,
At least a part of the end portion of the circuit on the insulating substrate side is covered with an insulating film,
The above-mentioned insulating film relates to a circuit board comprising a dry coating film or a cured coating film of a coating material containing an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm.

In the above embodiment, the dielectric breakdown voltage of the insulating film is preferably 50 V/μm or more. The viscosity of the coating material at 25°C is preferably 30 to 500 Pa·s. The thixotropy coefficient at 25° C. of the coating material is preferably 2.0 to 10.0.

In the above embodiment, the insulating resin preferably contains at least one selected from the group consisting of polyamide, polyamideimide, and polyimide.

Another embodiment relates to a semiconductor device having the circuit board of the above embodiment and a semiconductor element mounted on the circuit board.

Another embodiment is a method for manufacturing a circuit board including a circuit and an insulating substrate that supports the circuit,
Preparing an insulating substrate having a circuit,
Applying a coating material containing an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm to at least a part of the end portion of the circuit on the insulating substrate side, and heating the coating material. And a method for producing a circuit board, which comprises forming an insulating film composed of a dry coating film or a cured coating film of the coating material.

Another embodiment is a method of manufacturing a semiconductor device having a circuit and a circuit board including an insulating substrate that supports the circuit, and a semiconductor device mounted on the circuit board,
Preparing an insulating substrate having a circuit,
Applying a coating material containing an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm to at least a part of the end portion of the circuit on the insulating substrate side,
A method for manufacturing a semiconductor device, comprising heating the coating material to form an insulating film made of a dried coating film or a cured coating film of the coating material, and mounting a semiconductor element on the circuit. ..

According to the present invention, a coating material that can be applied to a predetermined portion with high accuracy and is excellent in shape retention after application and capable of forming a film having an excellent dielectric breakdown voltage is used. It is possible to provide a circuit board in which is suppressed. Further, by using such a circuit board, it is possible to provide a semiconductor device having excellent insulation reliability.

FIG. 1 is a plan view schematically showing a partial structure of a circuit board according to an embodiment. FIG. 2 is a side sectional view schematically showing a partial structure of the circuit board according to the embodiment. FIG. 3 is a side sectional view schematically showing a partial structure of the circuit board according to the embodiment.

Hereinafter, embodiments of the present invention will be specifically described.
1. Circuit board One embodiment comprises a circuit and an insulating substrate that supports the circuit, wherein at least a part of an end portion of the circuit on the insulating substrate side is covered with an insulating film, and the insulating film has an insulating property. The present invention relates to a circuit board comprising a dry coating film or a cured coating film of a coating material containing a resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm.

FIG. 1 is a plan view showing an example of a circuit board. In FIG. 1, reference numeral 1 is an insulating substrate, 2 is a circuit, and 3 is an insulating film. In the circuit board shown in FIG. 1, the entire surface of the insulating substrate other than the circuit portion is covered with an insulating film. The insulating film may cover at least the end of the circuit on the side of the insulating substrate, and may cover the end of part or all of the circuit in the circuit board.

The point on the circuit board where the leak current is most likely to occur is the end of the circuit on the side of the insulating board. Therefore, for example, as shown in FIG. 2, the insulating film 3 may cover at least the edge of the insulating substrate extending from the end 2a of the circuit on the insulating substrate side. For example, a thick copper substrate having circuits on both sides of an insulating substrate handles a large current, so that a leak current is likely to occur via the edge of the insulating substrate. Therefore, the generation of leak current is usually suppressed by increasing the edge width of the insulating substrate. However, as shown in FIG. 2, at least the edge of the insulating substrate extending from the end portion 2a on the insulating substrate side of the circuit is covered with an insulating film, so that the leakage current of the leakage current can be increased without increasing the edge width of the insulating substrate. It is possible to suppress the occurrence. Further, since leakage current may occur at the other end 2b of the circuit (end on the circuit upper surface side), even if a part of the end 2b is covered with an insulating film in addition to the end 2a of the circuit. Good.
The insulating film may cover the surface of the insulating substrate other than the circuit portion, for example, the surface of the insulating substrate between at least some circuits. For example, as shown in FIG. 3, the insulating film 3 may cover at least two adjacent end portions 2a on the insulating substrate side of the circuit (that is, between the circuits). Furthermore, the insulating film may cover a part of two adjacent end portions 2b on the circuit upper surface side.

In one embodiment, the insulating substrate may be, for example, a ceramic substrate, a resin substrate, or a metal base substrate. In one embodiment, the insulating substrate may be a silicon carbide (SiC) substrate and a gallium nitride (GaN) substrate. The SiC substrate and the GaN substrate are preferably used for power semiconductor devices. In the circuit board of the present embodiment, at least the end of the circuit on the side of the insulating board is covered with the insulating film, so that the generation of leak current is effectively suppressed. Therefore, excellent insulation reliability can be provided even when a power semiconductor is formed using the circuit board.

The circuit on the circuit board may be made of a metal film of Cu, Au, Ni or the like, or a conductive paste. The circuit may be in direct contact with the insulating substrate or may be in contact with the insulating substrate via a bonding layer or the like. In one embodiment, the circuit is preferably a metal circuit obtained by etching a metal film provided on an insulating substrate. The circuit may be formed not only on one surface of the insulating substrate but also on the other surface.

From the viewpoint of insulation reliability, the insulation breakdown voltage of the insulating film in the circuit board is preferably 50 V/μm or more, more preferably 100 V/μm or more, and further preferably 150 V/μm or more. .. When the insulation breakdown voltage of the insulating film is 50 V/μm or more, excellent insulation reliability can be easily obtained even in a semiconductor device having a higher power density than before.

Generally, an insulating film formed by using a coating material containing an inorganic filler is likely to be energized along the filler existing in the film when a voltage is applied, and the dielectric breakdown voltage of the film is likely to be lowered. On the other hand, in the present embodiment, by using the resin filler, it is possible to suppress a decrease in the dielectric breakdown voltage and easily obtain a desired value of the dielectric breakdown voltage at a constant film thickness. This is not bound by theory, but is considered to be due to the following. First, the resin filler tends to be more compatible with the resin than the inorganic filler. Further, since at least a part of the resin filler is melted during heating for forming the insulating film, the interface between the resin and the resin filler is less likely to occur, and the uniformity is improved. When the uniformity of the film is improved, the value of the current flowing along the filler interface in the film is reduced, so that the reduction of the dielectric breakdown voltage can be suppressed. Details of the resin filler will be described later.

In one embodiment, the coating material forming the insulating film preferably has a viscosity at 25°C of 30 to 500 Pa·s. The viscosity is more preferably 50 to 400 Pa·s, further preferably 100 to 300 Pa·s.
Here, the viscosity is the coating material (varnish) obtained by dissolving the solid component in a solvent so that the content of the nonvolatile component (solid component) is 1 to 20% based on the total mass of the coating material. It is the value measured by using. The measurement is performed using an E-type viscometer, for example, at 25° C. and 0.5 rpm. More specifically, the viscosity can be measured using a viscometer (RE type) manufactured by Toki Sangyo Co., Ltd., for example. The measurement value is a value obtained by setting the measurement temperature to 25° C.±0.5° C., then putting 1 mL to 1.5 mL of coating material (varnish) in the viscometer, and recording the viscosity 10 minutes after the start of measurement. You can

When the viscosity measured at 0.5 rpm is 30 Pa·s or more, there is an appropriate viscosity at the time of application and it is easy to maintain the shape of the coating film. Further, when the viscosity is 500 Pa·s or less, defects such as coating defects during coating are less likely to occur. Therefore, by adjusting the viscosity within the above range, excellent coatability and film formability can be easily obtained.
In one embodiment, the viscosity is preferably more than 50 Pa·s, and more preferably more than 100 Pa·s, from the viewpoint of easily obtaining excellent coatability. If the viscosity is too low, the varnish may spread more easily than the prescribed coating range, and may be difficult to handle.

In one embodiment, the thixotropy coefficient of the coating material (varnish) at 25° C. is preferably 2.0 to 10.0. The thixotropy coefficient is more preferably 2 to 7, and even more preferably 2 to 5. When the thixotropy coefficient is in the above range, it becomes easy to achieve both applicability and shape retention after application. The thixotropy coefficient is a viscosity (Pa·s) measured at a cone rotation speed of 10 rpm using a E-type viscometer at a cone rotation speed of 1 rpm and a viscosity (Pa·s) measured at a cone rotation speed of 10 rpm. When s) is the viscosity B, it is obtained as the value of viscosity A/viscosity B.

In one embodiment, the shape retention of the coating material after application can be evaluated, for example, from the aspect ratio (=coating thickness/coating width) of a dried coating film obtained by dispensing coating. The aspect ratio is preferably 0.02 or more, more preferably 0.03 or more, and more preferably 0.07 or more, from the viewpoint of forming a film thickness with which sufficient insulation can be easily obtained. Is more preferable. The aspect ratio can be measured using, for example, a Dektak 6M surface profiler manufactured by ULVAC, Inc. The aspect ratio may be, for example, a value calculated as a ratio of the coating film thickness to the dry coating film having a coating film width of 100 to 2000 μm.

In one embodiment, the thickness of the insulating film formed of the coating material is not particularly limited, but is preferably 5 μm or more. From the viewpoint of obtaining more excellent insulation reliability, the film thickness is more preferably 20 μm or more, further preferably 50 μm or more. In one embodiment, considering the relationship with the thickness of a general circuit, the film thickness is preferably 5 to 200 μm. From the viewpoint of easily obtaining a thick film by coating, the coating material preferably has a high viscosity. On the other hand, if the viscosity is increased, the coating property tends to be lowered. On the other hand, in this embodiment, since the insulating film is formed using the coating material having appropriate viscosity and thixotropic property, the thick film can be obtained with high accuracy.

The coating material forming the insulating film includes an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm. The components of the coating material will be described below.
(Insulating resin)
As the insulating resin, a resin known in the art as an insulating resin can be used. In one embodiment, the insulating resin preferably contains at least one selected from the group consisting of a polyamide resin, a polyamide-imide resin, and a polyimide resin. Polyamide resin, polyamide-imide resin, and polyimide resin are also preferable in that they have excellent heat resistance and chemical resistance. Among them, polyamide resins and polyamide-imide resins are more preferable in that high-temperature treatment for imidization is not required during film formation, and polyamide-imide resins are more preferable in terms of high heat resistance.

Polyamide resin, polyamide-imide resin, and polyimide resin are, for example, resins obtained by reacting an aromatic, aliphatic, or alicyclic diamine compound with a polyvalent carboxylic acid having 2 to 4 carboxyl groups. Good. The polyimide resin and the polyamide-imide resin can be obtained by forming a precursor (polyamic acid) by the above reaction and dehydrating and ring-closing the precursor.

As the aromatic, aliphatic, or alicyclic diamine compound, an arylene group, an alkylene group which may have an unsaturated bond, or a cycloalkylene group which may have an unsaturated bond, or these Diamine compounds having combined groups are mentioned. These groups may be bonded via a carbon atom, an oxygen atom, a sulfur atom, a silicon atom, or a group combining these atoms. Further, the hydrogen atom bonded to the carbon skeleton of the alkylene group may be replaced with a fluorine atom. From the viewpoint of heat resistance and mechanical strength, aromatic diamines are preferable.

Examples of the polycarboxylic acid having 2 to 4 carboxyl groups include dicarboxylic acid or its reactive acid derivative, tricarboxylic acid or its reactive acid derivative, and tetracarboxylic dianhydride. These compounds include an aryl group, a dicarboxylic acid having a carboxyl group bonded to a cycloalkyl group which may have a crosslinked structure or an unsaturated bond in the ring, a tricarboxylic acid or a reactive acid derivative thereof, or an aryl group. It may be a tetracarboxylic dianhydride in which a carboxyl group is bonded to a group or a cycloalkyl group which may have a crosslinked structure or an unsaturated bond in the ring. Such a dicarboxylic acid, a tricarboxylic acid, or a reactive acid derivative thereof, and a tetracarboxylic acid dianhydride, through a single bond, or a carbon atom, an oxygen atom, a sulfur atom, a silicon atom, or these It may be bonded via a group combining atoms. Further, the hydrogen atom bonded to the carbon skeleton of the alkylene group may be replaced with a fluorine atom.
Among these compounds, tetracarboxylic dianhydride is preferable from the viewpoint of heat resistance and mechanical strength. The combination of the aromatic, aliphatic, or alicyclic diamine compound and the polyvalent carboxylic acid having 2 to 4 carboxyl groups can be appropriately selected depending on the reactivity and the like.

Polyamide resins, polyamideimide resins, and polyimide resins can be manufactured according to methods well known in the art. For example, as an example, a method for producing a polyamide-imide resin or a polyimide resin will be described below.
The reaction can be carried out without using a solvent or in the presence of an organic solvent. The reaction temperature is preferably 25° C. to 250° C., and the reaction time can be appropriately selected depending on the scale of the batch, the reaction conditions adopted, and the like.

The method of dehydrating and ring-closing the polyimide resin precursor or the polyamide-imide resin precursor to form the polyimide resin or the polyamide-imide resin is not particularly limited, and a general method can be used. For example, a thermal ring-closing method of dehydrating and ring-closing by heating under normal pressure or reduced pressure, a chemical ring-closing method using a dehydrating agent such as acetic anhydride in the presence or absence of a catalyst, and the like can be used.

The thermal cyclization method is preferably carried out while removing water generated by the dehydration reaction outside the system. During the dehydration reaction, the reaction solution may be heated to a temperature of 80 to 400°C, preferably 100 to 250°C. Further, a solvent such as benzene, toluene, xylene, etc. that is azeotropic with water may be used together to remove water azeotropically.
The thermal cyclization method can also be carried out in a film state (solvent-free state). The ring-closing reaction by heating proceeds at a temperature of 250° C., for example, but when carried out at a temperature of about 350° C. to 400° C., physical properties such as glass transition temperature can be improved. Therefore, it is preferable to appropriately adjust the heating temperature in consideration of the heat resistance of the resin and influence on other members such as occurrence of warpage.

In the case of the chemical ring closure method, it is preferable to carry out the reaction in the presence of a chemical dehydrating agent at a temperature of 0 to 120°C, preferably 10 to 80°C. As the chemical dehydrating agent, it is preferable to use, for example, acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride and benzoic anhydride, and carbodiimide compounds such as dicyclohexylcarbodiimide. At this time, it is preferable to use a substance that promotes the cyclization reaction such as pyridine, isoquinoline, trimethylamine, triethylamine, aminopyridine, and imidazole together. The chemical dehydrating agent is used in an amount of 90 to 600 mol% with respect to the total amount of the diamine compound, and the substance that promotes the cyclization reaction is used in an amount of 40 to 300 mol% with respect to the total amount of the diamine compound. In addition, a dehydration catalyst such as triphenyl phosphite, tricyclohexyl phosphite, triphenyl phosphate, phosphoric acid, a phosphorus compound such as phosphorus pentoxide, and a boron compound such as boric acid and boric anhydride may be used.

In one embodiment, the heat resistant resin may include, for example, a resin having a structural unit represented by the following formulas (1) to (10).

式（１）中、Ｘは、−ＣＨ_２―、−Ｏ−、−ＣＯ−、−ＳＯ_２−、又は、下記式（ａ）〜（ｉ）で表される基であり、式（ｉ）中、ｐは、１〜１００の整数である。

In formula (1), _{X, -CH 2 -, - O -} , - CO -, - SO 2 -, or a group represented by the following formula (a) ~ (i), formula (i) Inside, p is an integer of 1-100.

式（２）中、Ｒ^１及びＲ^２は、それぞれ水素原子又は炭素数１〜６の炭化水素基であり、互いに同じでも異なっていてもよい。Ｘは、式（１）のＸと同じである。

In formula (2), R ¹ and R ² are each a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and may be the same or different from each other. X is the same as X in formula (1).

式（３）中、Ｍは、下記式（ｃ）、（ｈ）、（ｉ）又は（ｊ）で表される基であり、式（ｉ）中、ｐは、１〜１００の整数である。

In formula (3), M is a group represented by the following formula (c), (h), (i) or (j), and in formula (i), p is an integer of 1 to 100. ..

式（４）中、Ｘは、式（１）のＸと同じである。

In formula (4), X is the same as X in formula (1).

式（５）中、Ｘは、式（１）のＸと同じである。

In formula (5), X is the same as X in formula (1).

式（６）中、Ｒ^３及びＲ^４は、それぞれメチル基、エチル基、プロピル基、又はフェニル基であり、互いに同じでも異なっていてもよく、Ｘは、式（１）のＸと同じである。

In formula (6), R ³ and R ⁴ are each a methyl group, an ethyl group, a propyl group, or a phenyl group, and they may be the same or different, and X is the same as X in formula (1). is there.

式（８）中、ｘ_１は、０又は２であり、Ｘは、式（１）のＸと同じである。

In formula (8), x ₁ is 0 or 2, and X is the same as X in formula (1).

In one embodiment, the insulating resin used to form the coating material is preferably soluble in the solvent at room temperature. On the other hand, the resin filler is preferably insoluble in the solvent at least at room temperature during application. This makes it easy to obtain excellent coatability and excellent shape retention after coating.
Here, "soluble in a solvent at room temperature" means that at room temperature, when a solution obtained by adding a solvent to a resin and shaking is visually observed, there is no precipitate, no turbidity, and a transparent state. Means that. Further, "insoluble in solvent at room temperature" means that the resin does not dissolve in the solvent at room temperature and the solid component remains in the solvent.
The room temperature may be in the range of 10 to 40°C, preferably 20 to 30°C. In one embodiment, the solution may be, for example, a solution obtained by adding 100 ml of the solvent to 0.5 to 25 mg of the resin and manually shaking the container containing these for several tens of seconds. The solvent will be described later.

When the above resin is a solvent at room temperature, the coating material can be easily prepared at room temperature. On the other hand, even when the solubility of the resin in the solvent at room temperature is low, the resin can be effectively dissolved in the solvent by heating as necessary. For example, in order to dissolve a resin such as a polyamide resin, a polyamideimide resin, and a polyimide resin in a solvent, a process of putting the resin and the solvent in a flask and heating them to 100° C. or higher in an oil bath or the like can be applied.

(Resin filler)
In one embodiment, the resin filler contained in the coating material may be resin particles composed of an insulating resin and having an average particle diameter of 0.1 to 5.0 μm. The average particle diameter of the resin filler is preferably 0.5 to 4.5 μm, more preferably 0.6 to 4.0 μm. The maximum particle size of the organic filler is preferably 10 μm or less, more preferably 5.0 μm or less. When a resin filler having an average particle diameter within the above range is used, it is easy to uniformly disperse it in the insulating resin, and a varnish having excellent characteristics such as thixotropy and film formability can be obtained. The average particle size and the maximum particle size of the resin filler can be measured by using a particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation.

The insulating resin forming the resin filler may be the same as or different from the insulating resin used as the base resin. However, it is premised that the form of the resin particles can be maintained in the coating material at the time of application.
In one embodiment, the resin filler is preferably composed of a resin containing at least one selected from the group consisting of a polyamide resin, a polyamideimide resin, and a polyimide resin. These resins can be manufactured by the same method as described above. In one embodiment, the resin filler is preferably composed of a polyimide resin.

For example, the resin filler may be composed of a resin having a structural unit represented by the following formulas (11) to (20).

式（１１）中、Ｙは、下記式（ａ）、（ｃ）又は（ｈ）で表される基である。

In formula (11), Y is a group represented by the following formula (a), (c), or (h).

式（１２）中、Ｙは、式（１１）のＹと同じである。なお、＊の部分は、互いに結合している（以下、同様）。

In formula (12), Y is the same as Y in formula (11). Note that the * portions are connected to each other (the same applies hereinafter).

式（１４）中、Ｚは、−ＣＨ_２―、−Ｏ−、−ＣＯ−、−ＳＯ_２−、又は、下記式（ａ）あるいは（ｄ）で表される基である。

Wherein (14), Z _{is, -CH 2 -, - O -} , - CO -, - SO 2 -, or a group represented by the following formula (a) or (d).

式（１６）中、Ｚは、式（１４）のＺと同じである。

In formula (16), Z is the same as Z in formula (14).

式（２０）中、Ｘは、式（１）のＸと同じであり、ｎ及びｍはそれぞれ独立に１以上の整数を示す。ｎとｍの比（ｎ／ｍ）は、８０／２０〜３０／７０であることが好ましく、７０／３０〜５０／５０であることがより好ましい。

In formula (20), X is the same as X in formula (1), and n and m each independently represent an integer of 1 or more. The ratio of n to m (n/m) is preferably 80/20 to 30/70, and more preferably 70/30 to 50/50.

The compounding ratio of the insulating resin and the resin filler is not particularly limited and may be any compounding amount. In one embodiment, the blending amount of the resin filler is preferably 10 to 300 parts by mass with respect to 100 parts by mass of the insulating resin. The amount of the resin filler blended is more preferably 10 to 200 parts by mass. When the compounding amount of the resin filler is more than 10 parts by mass with respect to 100 parts by mass of the insulating resin, it becomes easy to obtain preferable thixotropy in the varnish. On the other hand, when the compounding amount of the resin filler is less than 300 parts by mass, it is possible to easily suppress deterioration of the physical properties of the insulating film formed from the varnish.

(solvent)
In one embodiment, the coating material may be a varnish obtained by adding a solvent to the insulating resin and the resin filler. Various solvents can be selected on the assumption that the insulating resin is soluble in the solvent and the resin filler is insoluble in the varnish at the time of application. In one embodiment, the solvent forming the varnish may be the same as the reaction solvent used during the production of the insulating resin such as the polyamide-imide resin. By using two or more kinds of solvents in combination, it becomes easy to appropriately adjust the solubility of the insulating resin and the resin filler in the varnish.

In one embodiment, the insulating resin is soluble in a mixed solvent of the first solvent (A1) and the second solvent (A2) at room temperature, and the resin filler is the first solvent (A1) at room temperature. ) And the second solvent (A2) are insoluble in the mixed solvent, it is preferable to select and use two or more kinds of solvents.

In the varnish according to the above-mentioned embodiment, the resin filler is dispersed in the mixed solution of the first solvent (A1), the second solvent (A2) and the insulating resin, and acts as a filler. This makes it possible to easily adjust a varnish having an appropriate thixotropy value in order to realize highly accurate application and shape retention after application. Furthermore, if the coating material is heated to a temperature at which the insulating resin dissolves after application, it is considered that the resin filler will also dissolve and the morphology of the filler will disappear, so even if the coating material contains a filler, the dielectric breakdown of the film will occur. The voltage drop is suppressed. From such a viewpoint, in one embodiment, after the varnish is applied, for example, when heated to 60° C. or higher, preferably 60 to 200° C., more preferably 100 to 180° C., the resin filler in the varnish is the mixed solvent. It is preferably soluble in water.

As specific examples of the solvent that can be used as the first solvent (A1) and the second solvent (A2),
Polyether alcohol solvents such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether,
Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dipropyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether Ether solvent such as tetraethylene glycol dipropyl ether, tetraethylene glycol dibutyl ether,
Sulfur-containing solvents such as dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone and sulfolane,
Ester solvents such as ethyl acetate, butyl acetate, cellosolve acetate, ethyl cellosolve acetate, butyrocellosolve acetate,
Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and acetophenone,
Nitrogen-containing systems such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 1,3-dimethyl-2-imidazolidinone solvent,
Aromatic hydrocarbon solvents such as toluene and xylene,
lactone solvents such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-heptalactone, α-acetyl-γ-butyrolactone and ε-caprolactone,
Alcohol solvents such as butanol, octyl alcohol, ethylene glycol, glycerin,
Phenol-based solvents such as phenol, cresol and xylenol can be used.

In one embodiment, the following (a)-(c) are mentioned as an example of the combination (mixed solvent) of the 1st solvent (A1) and the 2nd solvent (A2).
(A) First solvent (A1): Nitrogen-containing solvent such as N-methylpyrrolidone and dimethylacetamide; Sulfur-containing solvent such as dimethyl sulfoxide; Lactone solvent such as γ-butyrolactone; and Xylenol and the like Phenol-based solvent and second solvent (A2): ether solvent such as diethylene glycol dimethyl ether; ketone solvent such as cyclohexanone; ester solvent such as butyl cellosolve acetate; alcohol solvent such as butanol; xylene etc. Combination with the above-mentioned aromatic hydrocarbon solvent.
(B) First solvent (A1): the above ether solvent such as tetraethylene glycol dimethyl ether; the above ketone solvent such as cyclohexanone; and the second solvent (A2): the above ester solvent such as butyl cellosolve acetate and ethyl acetate. A combination with the above alcohol solvent such as butanol, the above polyether alcohol solvent such as diethylene glycol monoethyl ether, and the above aromatic hydrocarbon solvent such as xylene.
(C) First solvent (A1): the above nitrogen-containing solvent such as 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, and the second solvent (A2): Combination with γ-butyrolactone solvent.

The combination of the first solvent (A1) and the second solvent (A2) is not limited to the above examples, and is appropriately selected from the above-mentioned various solvents according to the types of the insulating resin and the resin filler. Can be used.
In one embodiment, the first solvent (A1) is preferably N-methylpyrrolidone, dimethylacetamide, dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone. , A nitrogen-containing solvent such as 1,3-dimethyl-2-imidazolidinone, a sulfur-containing solvent such as dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, sulfolane, γ-butyrolactone, γ-valerolactone , Γ-caprolactone, γ-heptalactone, α-acetyl-γ-butyrolactone, ε-caprolactone and other lactone solvents, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetophenone and other ketone solvents, butanol, octyl alcohol, ethylene glycol, Examples thereof include alcohol solvents such as glycerin.
In one embodiment, when the insulating resin and the resin filler are each independently at least one selected from a polyamide resin, a polyimide resin, a polyamideimide resin, or a precursor of a polyimide resin and a polyamideimide resin, As the solvent (A1) of No. 1, γ-butyrolactone is particularly preferable.

In one embodiment, the second solvent (A2) is preferably diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dipropyl ether. Ether solvent such as triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dipropyl ether, tetraethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether Polyether alcohol solvent such as triethylene glycol monoethyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, etc., ester solvent such as ethyl acetate, butyl acetate, cellosolve acetate, ethyl cellosolve acetate, butyrocellosolve acetate Etc.
In one embodiment, when the insulating resin and the resin filler are each independently at least one selected from a polyamide resin, a polyimide resin, a polyamideimide resin, or a precursor of a polyimide resin and a polyamideimide resin, As the second solvent (A2), a polyether alcohol solvent, an ester solvent, or an ester solvent is preferable.

In one embodiment, from the viewpoint of improving the handleability of the varnish, in the varnish, the difference between the boiling point of the first solvent (A1) and the boiling point of the second solvent (A2) is 10 to 100°C. Is preferable, 10° C. to 50° C. is more preferable, and 10° C. to 30° C. is further preferable. Further, the boiling points of both the first solvent (A1) and the second solvent (A2) are preferably 100° C. or higher, and 150° C. or higher, from the viewpoint that the pot life of the varnish at the time of application can be lengthened. Is more preferable.

In one embodiment, the mixing ratio of the first solvent (A1) and the second solvent (A2) is the type of the insulating resin and the resin filler, the first solvent (A1) and the second solvent (A2). It depends on the solubility or the amount used. Therefore, it is preferable to appropriately adjust in consideration of these. For example, the mixing ratio (A1:A2) is preferably 6:4 to 9:1 from the viewpoint of obtaining the fluidity of the varnish, the resolution of the resin film, the shape retaining property, and the flatness of the surface in a highly balanced manner. You can The mixing ratio may be more preferably 6.5:3.5 to 8.5:1.5, and further preferably 7:3 to 8:2.

In one embodiment, 100 to 3500 parts by mass of a mixed solvent of a first solvent (A1) and a second solvent (A2) is mixed with 100 parts by mass of an insulating resin and a resin filler in a varnish. It is preferable to mix it, and it is more preferable to mix it in 150 to 1000 parts by mass. When the compounding amount of the solvent in the varnish is adjusted within the above range, an appropriate viscosity can be easily obtained from the viewpoint of coatability.

As an embodiment, the following are specific examples of the combination of the insulating resin, the resin filler, and the solvent in the varnish.
First solvent (A1): contains a lactone solvent or a nitrogen-containing solvent.
Second solvent (A2): Contains an ether solvent or an ester solvent.
Insulating resin: Includes the resin represented by the formula (1).
Resin filler: Includes a resin having a structural unit represented by formula (20) or formula (16).

Moreover, the following is mentioned as another specific example.
First solvent (A1): Contains an ether solvent or a ketone solvent.
Second solvent (A2): Contains an ester solvent, an alcohol solvent, a polyether alcohol solvent, or an aromatic carbon hydrogen solvent.
Insulating resin: A resin having a structural unit represented by the following formulas (21) and (22), or a polysiloxane imide having a structural unit represented by the above formula (6) is included.

式（２２）中、Ｚ^１は、−Ｏ−、−ＣＯ−、又は、下記式（ｄ）、（ｅ）、（ｋ）あるいは（ｌ）で表される基である。Ｒ^５及びＲ^６は、それぞれ下記式（ｍ）又は（ｎ）で表される基であり、互いに同じでも異なっていてもよい。ｐは、１〜１００の整数である。

In formula (22), Z ¹ is —O—, —CO—, or a group represented by the following formula (d), (e), (k), or (l). R ⁵ and R ⁶ are groups represented by the following formula (m) or (n), and may be the same or different from each other. p is an integer of 1 to 100.

Resin filler: a polyether amide imide having a structural unit in which X of the above-mentioned formula (1) is a group represented by the following formula (a) or (b) described below, or the above-mentioned. Polyimides represented by the formulas (5) to (9) (excluding the case where X in the above formulas (5), (6) and (8) is the following formula (a)) are included.

In addition to the above-mentioned raw materials, the coating material (varnish) may be added with additives such as a coupling agent and additional components such as a resin modifier, if necessary. When the varnish contains an additional component, the amount of the additional component is preferably 50 parts by mass or less based on 100 parts by mass of the resin (solid component) in the varnish. By setting the amount of the additional component to be 50 parts by mass or less, it becomes easy to suppress deterioration of the physical properties of the obtained coating film.

(Method of preparing coating material (varnish))
The coating material can be produced by mixing the raw materials according to methods well known in the art. The order of introducing the raw materials at the time of manufacturing the coating material is not particularly limited. For example, the raw materials of the coating material may be mixed together, or first, the second solvent (A1) and the second solvent (A2) are mixed, and the insulating resin is added to the mixed solvent. A resin filler may be added to a mixed solution of the first solvent (A1), the second solvent (A2), and the insulating resin after mixing. In one embodiment, the raw materials are mixed by heating the mixed solution of the first solvent (A1), the second solvent (A2), and the insulating resin to a temperature at which the resin filler is sufficiently dissolved, and further stirring or the like. It can also be implemented by. In this case, the desired coating material can be obtained by sufficiently cooling the raw materials and then slowly cooling to precipitate the resin.

2. TECHNICAL FIELD One embodiment relates to a method of manufacturing a circuit board including a circuit and an insulating substrate that supports the circuit. In the above-mentioned manufacturing method, an insulating substrate having a circuit is prepared, and an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm are included in at least a part of an end portion of the circuit on the insulating substrate side. It includes applying a coating material and heating the coating material (coating film) to form an insulating film composed of a dry coating film or a cured coating film of the coating material.

Insulating substrates with circuits can be manufactured according to methods well known in the art. For example, it can be formed by processing a metal film provided on an insulating substrate into a predetermined circuit pattern by etching. Alternatively, it can be formed by printing a conductive paste on an insulating substrate in a predetermined circuit pattern by a printing method. It is also possible to use a commercially available circuit board.

The coating method of the coating material is not particularly limited, and examples thereof include a spray coating method, a potting method, a dipping method, a spin coating method, and a dispensing method. From the viewpoint of workability and the like, coating by a dipping method or a dispensing method is preferable. It is preferable to adjust the coating amount of the coating material in consideration of the thickness of the circuits and the width between the circuits. For example, in one embodiment, it is preferable to adjust the pressure using a syringe so that the discharge amount of the coating material is 0.2 to 0.3 g in 5 seconds.

The heating after applying the coating material is not particularly limited, and can be performed by a method such as an explosion-proof dryer or a hot plate.

In one embodiment, the heating during drying is preferably performed in two stages of heating at a temperature of 100°C and further at a temperature of, for example, 180 to 250°C. In another embodiment, the heating during drying is preferably carried out in two stages of heating at a temperature of 100°C and further at a temperature of, for example, 250°C to 350°C.

3. Semiconductor device and method for manufacturing the same One embodiment relates to a semiconductor device having the circuit board of the above-described embodiment and a semiconductor element mounted on the circuit board. The semiconductor device preferably further has a sealing layer that covers the semiconductor element. In the semiconductor device of the present embodiment, the generation of leak current is suppressed in the circuit board, so high insulation reliability can be obtained.
The semiconductor device can be configured according to a technique well known to those skilled in the art, except that the circuit board of the above-described embodiment is used. For example, when mounting a semiconductor element on a circuit board, the semiconductor element can be fixed to the circuit board using an adhesive or an adhesive film. Further, the semiconductor element can be electrically connected to the circuit board by wire bonding. The semiconductor element can be composed of, for example, a silicon wafer, a silicon carbide wafer, or the like.

Semiconductor devices can be manufactured according to methods well known in the art. In one embodiment, the manufacturing method may include preparing the circuit board of the above embodiment.
Therefore, in one embodiment, the method for manufacturing a semiconductor device includes
Preparing an insulating substrate having a circuit,
Applying a coating material containing an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm to at least a part of the end portion of the circuit on the insulating substrate side;
The method may include heating the coating material to form an insulating film composed of a dry coating film or a cured coating film of the coating material, and mounting a semiconductor element on the circuit.
The manufacturing method may further include providing a sealing layer that covers the semiconductor element. The sealing layer can be formed using, for example, a resin sealing material.

Hereinafter, the present invention will be described more specifically, but the present invention is not limited to these and may include various embodiments.

1. Synthesis of heat resistant resin and resin filler (Synthesis example 1)
In a 5-liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube with an oil/water separator, under a nitrogen stream, 2,2-bis[4-(4-aminophenoxy)phenyl]propane. (Hereinafter, referred to as BAPP) 650.90 g (1.59 mol), and 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter referred to as BY16-871) 43.80 g (0.18 mol) ) Was further added, and 3609.86 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) was added and dissolved to obtain a solution. Next, 384.36 g (1.83 mol) of trimellitic anhydride chloride (hereinafter referred to as TAC) was added to this solution while cooling so as not to exceed 20°C.
After stirring the resulting solution at room temperature for 1 hour, 215.90 g (2.14 mol) of triethylamine (hereinafter referred to as TEA) was added to the solution while cooling so that the temperature did not exceed 20° C. The reaction was carried out at (° C.) for 1 hour to prepare a polyamic acid solution. Furthermore, the polyamic acid solution was dehydrated at 180° C. for 6 hours to produce a polyamideimide resin solution. A polyamideimide resin powder (PAI-1) was obtained by pouring this polyamideimide resin solution into water, separating the precipitate, pulverizing, and drying. The Mw of the obtained polyamide-imide resin (PAI-1) was 77,000.

The detailed conditions for measuring Mw are as follows.
Detector: JASCO Corporation UV detector 875-UV
Column: Showa Denko KK Shodex solvent displacement separation column GPC KD-806M
Eluent: H ₃ PO ₄ (0.06 mol/L)-containing NMP
Temperature: 25°C
Flow rate: 1.0 mL/min

(Synthesis example 2)
In a 1-liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube equipped with an oil/water separator, under a nitrogen stream, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride. (Hereinafter referred to as BTDA) 96.7 g (0.3 mol), 4,4′-diaminodiphenyl ether (hereinafter referred to as DDE) 55.4 g (0.285 mol), and BY16-871 3.73 g (0 .015 mol) and 363 g of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (hereinafter referred to as DMPU) were added to obtain a solution. This solution was stirred at 70 to 90° C. for about 6 hours, then cooled to stop the reaction, and a heat resistant resin solution (PI-1) of a polyimide resin precursor was obtained. The Mw of the polyimide resin precursor (PI-1) in the obtained solution was 15,000. The Mw was measured in the same manner as in Synthesis Example 1.

(Synthesis example 3)
In a 1-liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube with an oil/water separator, 69.72 g (170.1 mmol) of BAPP and BY16-871 under a nitrogen stream. 4.69 g (18.9 mmol) was added, and 693.52 g of NMP was added and dissolved to obtain a solution. Next, while cooling the solution so as not to exceed 20° C., 25.05 g (119.0 mmol) of TAC and 3,4,3′,4′-benzophenonetetracarboxylic dianhydride (hereinafter referred to as BTDA). ) 25.47 g (79.1 mmol) was added.
After stirring the above solution at room temperature for 1 hour, 14.42 g (142.8 mmol) of TEA was added while cooling so as not to exceed 20° C. and reacted at room temperature for 1 hour to prepare a polyamic acid solution. The resulting polyamic acid solution was further dehydrated at 180° C. for 6 hours to produce a polyimide resin solution. A precipitate obtained by pouring this polyimide resin solution into water was separated, pulverized, and dried to obtain a polyimide resin powder (PAIF-1). The Mw of the obtained polyimide resin (PAIF-1) was 42,000.

(Synthesis example 4)
In a 1-liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube with an oil/water separator, under nitrogen stream, 96.7 g (0.3 mol) of BTDA and 61.5 g of BAPP ( 0.15 mol), DDE 27.0 g (0.135 mol), BY16-871 3.73 g (0.015 mol), DMPU 133.25 g, and γ-BL 308.59 g were charged, and the solution was charged. Obtained. When this solution was stirred at 70 to 90° C. for 5 hours, a polyimide precursor filler was precipitated in the solution. Then, the solution was cooled to stop the reaction, and a heat resistant resin filler solution (PIF-1) of a polyimide resin precursor was obtained. The Mw of the polyimide resin precursor (PIF-1) in the obtained solution was 34,000.

3. Preparation of coating material (varnish) (Preparation example 1)
Γ-butyrolactone (hereinafter referred to as γ-BL) as a first solvent (A1) in a 0.5 liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube. 92.4 g, triethylene glycol dimethyl ether (hereinafter referred to as DMTG) 39.6 g as the second solvent (A2), and the polyamideimide resin powder (PAI-1) obtained in Synthesis Example 1 as the insulating resin 30 A solution was obtained by adding 0.8 g and 13.2 g of the polyimide resin powder (PAIF-1) obtained in Synthesis Example 3 as a resin filler. The temperature of this solution was raised to 180° C. with stirring, and the heating was stopped after stirring at 180° C. for 2 hours.
Next, the above solution was allowed to cool with stirring, 16.8 g of γ-BL and 7.2 g of DMTG were added at 60° C., and the mixture was stirred for 1 hour. When the obtained solution was cooled and then visually confirmed at room temperature (25° C.), it was yellow.
The above yellow solution was filled in a filter KST-47 (manufactured by Advantech Co., Ltd.), a silicone rubber piston was inserted, and pressure filtration was performed at room temperature (25° C.) at a pressure of 3.0 kg/cm ² , A coating material (varnish) 1 was obtained. The mass ratio (A1):(A2) of the first solvent (A1) to the second solvent (A2) in the varnish 1 was 7:3.

(Preparation example 2)
In a 1-liter four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a cooling tube equipped with an oil/water separator, under a nitrogen stream, the heat-resistant resin solution (PI- 1) 300 g and 400 g of the heat-resistant resin filler solution (PIF-1) obtained in Synthesis Example 4 as a resin filler were charged and stirred at 50 to 70° C. for 2 hours to dissolve the heat-resistant resin and disperse the resin filler. A coating material (varnish) 2 was obtained. When this varnish was visually confirmed at room temperature (25° C.), it was yellow.
The varnish 2 contains DMPU as the first solvent (A1) and γ-BL as the second solvent (A2), and the mass ratio of (A1):(A2) is derived from each resin solution. , 1:2.

(Preparation example 3)
A 150 mL ointment container was charged with 15 g of the polyamideimide powder (PAI-1) obtained in Synthesis Example 1 and 85 g of diethylene glycol dimethyl ether (hereinafter referred to as DMDG), and the mixture was stirred at room temperature (25° C.) to completely remove PAI-1. Dissolved. After that, silica (AEROSILR972, manufactured by Nippon Aerosil Co., Ltd.) (23.2 g) was added to this solution, and after stirring with a glass rod, stirring was performed with a disper under conditions of 2000 rpm/10 minutes, and further, a revolving mixer (Sinky Corporation). Manufactured by ARV-930) was stirred under the condition of 1400 rpm/20 seconds to obtain a yellow solution.
The obtained yellow solution was filled in a filter KST-47 (manufactured by Advantech Co., Ltd.), a silicone rubber piston was inserted, and pressure filtration was performed at a pressure of 3.0 kg/cm ² to obtain a coating material (varnish) 3. Got

(Preparation example 4)
To a 150 mL ointment container, 85 g of DMDG and 15 g of the polyamideimide resin powder (PAI-1) obtained in Synthesis Example 1 as an insulating resin were added. These were shaken for one day using a shaker to completely dissolve the insulating resin. When the resulting solution was visually confirmed at room temperature (25°C), it was yellow and transparent.
The above yellow transparent solution was filled in a filter KST-47 (manufactured by Advantech Co., Ltd.), a silicone rubber piston was inserted, and the coating material (varnish) 4 was obtained by pressure filtration at a pressure of 3.0 kg/cm ^2. Obtained.

4. Characteristics of coating material (varnish) The varnishes obtained in Preparation Examples 1 to 4 were measured according to the following. The results obtained in each measurement are shown in Table 1.

(Measurement method of average particle diameter)
(1) Preparation of Sample First, two slide glasses (manufactured by MATSUNAMI Co., Ltd., size: 76 mm×26 mm, thickness: 1.2 mm) were stacked, placed on a cell holder, and a blank measurement was performed. Then, about 1.0 mL of the resin paste is placed on the measuring portion of the high-concentration sample measuring cell (cell thickness: 1.7 mm, measuring portion depth: 0.3 mm), and slide glass is used to spread the resin paste. It was sandwiched and placed in the cell holder so that the laser hits the measurement part.

(2) Measurement A particle size distribution was measured under the following conditions using a laser diffraction particle size distribution analyzer “SALD-2200” manufactured by Shimadzu Corporation.
Refractive index: 1.70 to 0.20i, maximum value of measurement absorbance range: 0.200 and minimum value: 0.010, setting value of sensor use start position: 20, temperature: 25°C

(3) Calculation of average particle diameter The integrated value 50% (volume basis) in the particle size distribution was taken as the average particle diameter.

(Viscosity and TI)
The viscosity was measured at 25° C. using an E-type viscometer manufactured by Toki Sangyo. The thixotropy coefficient (TI) was calculated from the ratio of these viscosities measured at 25° C. using an E-type viscometer manufactured by Toki Sangyo Co., Ltd. when the cone rotation speed was measured at 1 rpm and 10 rpm. Specifically, when the viscosity (Pa·s) measured under the condition of a cone rotation speed of 1 rpm is the viscosity A and the viscosity (Pa·s) measured under the condition of a cone rotation speed of 10 rpm is the viscosity B, the viscosity is The value of A/viscosity B was defined as TI.

(Measurement of non-volatile components)
The non-volatile component was calculated from the mass ratio before and after heating each varnish at 150° C. for 1 hour and further at 250° C. for 2 hours.

(Coating film profile)
Each varnish was applied on a silicon mirror wafer by air dispensing. Next, the varnishes of Preparation Examples 1 and 2 were dried at 80° C. for 10 minutes and further at 200° C. for 1 hour. On the other hand, the varnishes of Preparation Examples 3 and 4 were dried at 50° C. for 10 minutes and then at 200° C. for 1 hour. The film thickness and line width of each film obtained after drying were measured by using a Dektak manufactured by Bruker. The film thickness was measured at the thickest part in the profile.
The conditions for the above air dispensing are as follows.
Syringe: 50 mL syringe PSY-50F manufactured by Musashi Engineering
Syringe nozzle: SNA-18GB manufactured by Musashi Engineering
Pressure: The discharge amount of each varnish was set to 0.2 to 0.3 g in 5 seconds.
Moving speed of syringe: 20 mm/sec.
Clearance: The clearance is set so that the application is not interrupted and the shape is not disturbed.

(Dielectric breakdown voltage)
Each varnish was applied on a conductive metal plate (Ni) so that the dry film thickness was 10 μm, and then dried to prepare a measurement sample.
The varnish 1 was dried under conditions of 80° C. for 10 minutes and 200° C. for 1 hour. The varnish 2 was subjected to conditions of 100° C. for 30 minutes and 350° C. for 1 hour. On the other hand, the varnishes 3 and 4 were dried under the conditions of 50° C. for 10 minutes and 200° C. for 1 hour.
Each measurement sample produced as described above was sandwiched between a pair of electrodes, and the dielectric breakdown voltage value was measured. The measurement was performed in oil with reference to JIS C2110 under the conditions that the pressure rising rate was 0.5 kV/sec, the measurement temperature was room temperature (25° C.), and the electrode shape was a sphere with φ20 mm.

As can be seen from Table 1, the varnish 1 and the varnish 2 corresponding to the examples of the present invention have an appropriate viscosity and thus are excellent in coating properties. Further, as shown by the aspect ratio, these varnishes retain the applied shape without being greatly spread after application, and are excellent in shape retention. Further, it is possible to realize a breakdown voltage exceeding 230 V/μm. On the other hand, the varnish 3 and the varnish 4 correspond to comparative examples. In the case of varnish 3 containing an inorganic filler instead of a resin filler, the value of insulation breakdown voltage was remarkably reduced. Further, in the varnish 4 containing no filler, the value of the dielectric breakdown voltage was high, but the viscosity was significantly reduced, and it was difficult to maintain the shape of the coating film.

From the above, according to the present invention, it is possible to form an insulating film with high precision using a specific coating material containing a resin filler at a predetermined position of an insulating substrate having a circuit, and as a result, It can be seen that a circuit board having excellent insulation reliability can be provided.

1 Insulating Substrate 2 Circuit 2a End 2b of Circuit on Insulating Substrate Side 2b End of Circuit 3 Insulating Film

Claims (8)

A circuit and an insulating substrate supporting the circuit,
At least a part of the end portion of the circuit on the insulating substrate side is covered with an insulating film,
The said insulating film is a circuit board which consists of a dry coating film or a cured coating film of the coating material containing an insulating resin and the resin filler whose average particle diameter is 0.1-5.0 micrometers. The circuit board according to claim 1, wherein a dielectric breakdown voltage of the insulating film is 50 V/μm or more. The circuit board according to claim 1, wherein the coating material has a viscosity at 25° C. of 30 to 500 Pa·s. The circuit board according to claim 1, wherein the thixotropy coefficient of the coating material at 25° C. is 2.0 to 10.0. The circuit board according to claim 1, wherein the insulating resin contains at least one selected from the group consisting of polyamide, polyamide-imide, and polyimide. A semiconductor device comprising: the circuit board according to claim 1; and a semiconductor element mounted on the circuit board. A method of manufacturing a circuit board comprising a circuit and an insulating substrate supporting the circuit,
Preparing an insulating substrate having a circuit,
Applying a coating material containing an insulating resin and a resin filler having an average particle size of 0.1 to 5.0 μm to at least a part of the end portion of the circuit on the insulating substrate side, and heating the coating material. And forming an insulating film made of a dry coating film or a cured coating film of the coating material. A method for manufacturing a semiconductor device having a circuit and a circuit board including an insulating substrate supporting the circuit, and a semiconductor device mounted on the circuit board,
Preparing an insulating substrate having a circuit,
Applying a coating material containing an insulating resin and a resin filler having an average particle diameter of 0.1 to 5.0 μm to at least a part of the end portion of the circuit on the insulating substrate side;
A method of manufacturing a semiconductor device, comprising heating the coating material to form an insulating film made of a dried coating film or a cured coating film of the coating material, and mounting a semiconductor element on the circuit.

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