JP2007099928A - Thermosetting resin paste and flexible wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosetting resin paste excellent in low warpage property, flexibility, adhesion with a sealant, solvent resistance and chemicals resistance, heat resistance, electrical characteristics, humidity resistance, workability and profitability necessary for a protecting film of a flexible wiring board, while maintaining insulation reliability of a fine pitch wiring under a high temperature-high humidity condition; and a flexible wiring board using the same. <P>SOLUTION: This thermosetting resin paste comprising a thermosetting resin and inorganic fine particles and used for a wiring board comprises (A) 100 parts by weight of a thermosetting resin and (B) 10 to 1,000 parts by weight of inorganic fine particles having an average particle diameter less than the half of the distance between two wirings of a wiring board. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermosetting resin paste and a flexible wiring board using the same.

  In recent years, the wiring pitch of flexible wiring boards such as FPC, TAB, and COF has been further refined in response to miniaturization, thinning, and high speed of electronic devices. In order to maintain the insulation reliability between the wirings, an insulating thermosetting resin paste is usually applied and cured on the wirings. However, when fine pitch wiring with a pitch of 40 μm or less is used, even if a conventional thermosetting resin paste is used, if voltage is applied to the wiring under high-temperature and high-humidity conditions, the insulation between the wirings will be reduced and insulation will last for a long time. There is a problem that cannot maintain reliability.

JP 7-304950 A JP-A-8-333455

  The present invention solves the above-mentioned problems of the prior art, maintains the insulation reliability of fine pitch wiring under high temperature and high humidity conditions, and has low warpage, flexibility, sealing required as a protective film for flexible wiring boards. The present invention provides a thermosetting resin paste excellent in adhesion to a stopper, solvent resistance and chemical resistance, heat resistance, electrical characteristics, workability and economy, and a flexible wiring board using the same.

The present invention is as follows.
1. In the thermosetting resin paste used for a wiring board containing a thermosetting resin and inorganic fine particles, (A) 100 parts by weight of the thermosetting resin, (B) 1/2 of the length between wirings of the wiring board. A thermosetting resin paste containing 10 to 1000 parts by weight of inorganic fine particles having an average particle size of less than 1.
2. Item 2. The thermosetting resin paste according to Item 1, wherein the tensile elastic modulus is 1.0 GPa or less at 25 ° C and the tensile elongation is 20% or more at 25 ° C.
3. Item 3. The thermosetting paste according to item 1 or 2, wherein a 5% thermogravimetric temperature reduction temperature of a cured film of the thermosetting paste is 250 ° C or higher.
4). Item 5. A flexible wiring board using the thermosetting resin paste according to any one of Items 1 to 3 as a protective film.

  The thermosetting resin paste of the present invention maintains the insulation reliability of fine pitch wiring under high-temperature and high-humidity conditions, and has low warpage, flexibility, and adhesion with a sealing material required as a protective film for flexible wiring boards. It has excellent properties, solvent resistance and chemical resistance, heat resistance, electrical properties, moisture resistance, workability and economy. Moreover, the flexible wiring board using the thermosetting resin paste of the present invention is a flexible wiring board having the above-described excellent characteristics.

  The thermosetting resin paste of the present invention is a thermosetting resin paste used for a wiring board, wherein (A) 100 parts by weight of the thermosetting resin as described above and (B) the length between wirings of the wiring board is 1 10 to 1000 parts by weight of inorganic fine particles having an average particle diameter of less than / 2 are contained as a component. If the thermosetting resin used as (A) component in this invention is a thermosetting resin which has insulation, there will be no restriction | limiting in particular. Furthermore, when the tensile modulus of the cured film exceeds 0.5 GPa at 25 ° C., the warping property and flexibility tend to decrease, and when the tensile elongation of the cured film is less than 50% at 25 ° C. Tend to decrease, and folding resistance tends to decrease. Although it does not restrict | limit especially as a wiring board of this invention, A thermosetting resin paste is especially suitable with respect to a flexible wiring board.

In addition, the inorganic fine particles used as the component (B) in the present invention have an average particle diameter of less than ½ of the inter-wiring length of the wiring board, and the thermosetting resin or thermosetting resin of the component (A) described above. There is no particular limitation as long as it can be dispersed in a resin solution to form a paste. When the average particle diameter of the inorganic fine particles in the present invention is ½ or more of the inter-wiring length of the wiring board, when a voltage is applied to the wiring under a high temperature and high humidity condition, the insulating property between the wirings is reduced There is a tendency that insulation reliability cannot be maintained over time. In this specification, for example, the average particle diameter is a value measured by a laser diffraction method. Examples of such inorganic fine particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), and silicon nitride (Si). ₃ N ₄ ), barium titanate (BaO · TiO ₂ ), barium carbonate (BaCO ₃ ), lead titanate (PbO · TiO ₂ ), lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT) , gallium oxide _{(Ga 2 O} 3), spinel _{(MgO · Al 2 O 3)} , mullite _{(3Al 2 O 3 · 2SiO 2} ), cordierite _{(2MgO · 2Al 2 O 3 /} 5SiO 2), talc (3MgO · 4SiO ₂ · _{H 2} O), aluminum titanate _{(TiO 2 -Al 2 O 3)} , yttria-containing zirconia _(Y 2 _{O 3} ZrO _2), barium silicate (BaO · 8SiO _2), boron nitride (BN), calcium carbonate (CaCO _3), calcium sulfate (CaSO _4), zinc oxide (ZnO), magnesium titanate (MgO · _TiO 2), sulfuric acid Barium (BaSO ₄ ), aluminum hydroxide [Al (OH) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], organic bentonite, carbon (C) and the like can be used, and one or two of these can be used. The above can also be used.

As a method of dispersing the inorganic fine particles in the thermosetting resin solution, roll kneading, mixer mixing, etc., which are usually performed in the paint field, are applied, and any method can be used as long as sufficient dispersion is performed.
In the thermosetting resin paste of the present invention, it is preferable that the viscosity with a rotary viscometer is 0.5 Pa · s to 500 Pa · s at 25 ° C. and the thixotropic coefficient is 1.1 or more. When the viscosity is less than 0.5 Pa · s, the flow of the paste after printing increases and the film thickness tends to be reduced. When the viscosity exceeds 500 Pa · s, the transferability of the paste to the substrate tends to decrease and voids and pinholes in the printed film tend to increase. When the thixotropy coefficient is less than 1.1, the stringing of the paste increases, the flow of the paste after printing increases, and the film thickness also tends to be reduced.

Here, the viscosity of the paste is expressed as a viscosity at a rotation speed of 10 rpm measured with a sample amount of 0.2 ml or 0.5 ml using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80U type). Also, the thixotropy coefficient (TI value) of the paste was applied only to the paste at the rotation speeds of 1 rpm and 10 rpm measured with a sample amount of 0.2 ml or 0.5 ml using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., model RE80U). Viscosity is expressed as the ratio η1 / η10 of η1 and η10.
Moreover, it is preferable that 5% thermogravimetric reduction temperature is 250 degreeC or more of what used the thermosetting resin paste of this invention as the cured film. If the 5% thermal weight loss temperature is less than 250 ° C., the cured film may be deformed and decomposed due to heat applied at the time of connection with a rigid wiring board, IC chip, electronic component or LCD panel.

  In the thermosetting resin paste of the present invention, the amount of the inorganic fine particles used as the component (B) is in the range of 10 to 1000 parts by weight with respect to 100 parts by weight of the thermosetting resin. When it is less than this, the flow of paste after printing becomes large and the film thickness tends to be reduced. Moreover, when more than 1000 weight part, the viscosity of a paste and a thixotropy coefficient become high, and there exists a tendency for the void and pinhole in a printed film to increase while the transferability to the base material of a paste falls.

As the thermosetting resin in the present invention, epoxy resin, phenol resin, acrylic resin, polyurethane, polybutadiene, water-added polybutadiene, polyester, polycarbonate, polyether, polysulfone, polytetrafluororesin, polysilicone, melamine resin, polyamide, polyimide There are thermosetting resins in which one or more of these are combined. Among these thermosetting resins, thermosetting resins containing imide bonds having excellent heat resistance, electrical properties, moisture resistance, solvent resistance, and chemical resistance are preferable.
The thermosetting resin containing an imide bond used in the present invention contains an imide bond as an essential component and has a trivalent polycarboxylic acid having an acid anhydride group or a derivative thereof and / or an acid anhydride group. It is obtained by reacting a polyvalent polycarboxylic acid with an isocyanate compound or an amine compound.

  Although there is no restriction | limiting in particular as trivalent polycarboxylic acid or its derivative (a) which has an acid anhydride group, For example, the compound shown by general formula (I) and (II) can be used. In view of heat resistance, cost, etc., trimellitic anhydride is particularly preferable.

（但し、両式中Ｒは水素、炭素数１〜１０のアルキル基又はフェニル基を示し、Ｙは−ＣＨ２−、−ＣＯ−、−ＳＯ２−、又は−Ｏ−を示す。）

(However, in both formulas, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or a phenyl group, and Y represents —CH 2 —, —CO—, —SO 2 —, or —O—).

  Although there is no restriction | limiting in particular as tetravalent polycarboxylic acid (a ') which has an acid anhydride group, For example, the tetracarboxylic dianhydride represented by the following general formula (III) can be used. These can be used alone or in combination of two or more.

（式中、Ｙは、下記式（ＩＩＩａ）から選ばれた４価の基を示す。）

(In the formula, Y represents a tetravalent group selected from the following formula (IIIa).)

  In addition to these, if necessary, aliphatic dicarboxylic acids (succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, sebacic acid, decanedioic acid, dodecanedioic acid, dimer acid, etc.), aromatic dicarboxylic acid Acids (isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, etc.) can be used. The diisocyanate can be obtained, for example, by reacting a carbonate diol represented by the following general formula (IV) and a diisocyanate represented by the general formula (V) in a solvent-free or organic solvent.

（式中、複数個のＲはそれぞれ独立に炭素数１〜１８のアルキレン基を示し、ｍは、１〜２０の整数である）

(In the formula, a plurality of R's each independently represents an alkylene group having 1 to 18 carbon atoms, and m is an integer of 1 to 20).

（式中、Ｘは、炭素数１〜１８のアルキレン基又はフェニレン基等のアリーレン基（これはメチル基等の炭素数１〜５の低級アルキル基を置換基として有していても よい）を示す）

(Wherein X represents an arylene group such as an alkylene group having 1 to 18 carbon atoms or a phenylene group (which may have a lower alkyl group having 1 to 5 carbon atoms such as a methyl group as a substituent). Show)

  Examples of the carbonate diols represented by the above general formula (IV) are commercially available as trade names PLACEL, CD-205, 205PL, 205HL, 210, 210PL, 210HL, 220, 220PL, and 220HL manufactured by Daicel Chemical Industries, Ltd. These can be used, and these can be used alone or in combination of two or more.

  Examples of the diisocyanates represented by the general formula (V) include diphenylmethane-2,4′-diisocyanate, 3,2′- or 3,3′- or 4,2′- or 4,3′-. Or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2 ' -Or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3 '-Or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane- 4,4'-diisocyanate, diphenylmethane-3 3′-diisocyanate, diphenylmethane-3,4′-diisocyanate, diphenyl ether-4, 4′-diisocyanate, benzophenone-4,4′-diisocyanate, diphenylsulfone-4,4′-diisocyanate, tolylene-2,4-diisocyanate, Fragrances such as tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4 ′-[2,2bis (4-phenoxyphenyl) propane] diisocyanate It is preferred to use a group polyisocyanate. These can be used alone or in combination of two or more.

  Hexamethylene diisocyanate, 2,2,4-trimethyl methamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylylene diisocyanate, lysine diisocyanate, etc. Aliphatic or alicyclic isocyanates and tri- or higher functional polyisocyanates may be used, and those stabilized with a blocking agent necessary to avoid changes over time may be used. Examples of the blocking agent include alcohol, phenol and oxime, but there is no particular limitation.

The blending amount of the carbonate diols represented by the general formula (IV) and the diisocyanate represented by the general formula (V) is such that the ratio of the number of hydroxyl groups to the number of isocyanate groups is isocyanate group / hydroxyl group = 1.01 or more. It is preferable to make it.
The reaction can be carried out without solvent or in the presence of an organic solvent. The reaction temperature is preferably 60 to 200 ° C., and the reaction time can be appropriately selected depending on the scale of the batch, the reaction conditions employed, and the like.

The number average molecular weight of the diisocyanate thus obtained is preferably 500 to 10,000, more preferably 1,000 to 9,500, and particularly preferably 1,500 to 9,000. preferable. When the number average molecular weight is less than 500, the warping property tends to deteriorate, and when it exceeds 10,000, the reactivity of diisocyanate is lowered and it tends to be difficult to obtain a polyimide resin.
In the present specification, the number average molecular weight is a value measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve.

  In the present invention, it is preferable to use a polyisocyanate compound other than the above-mentioned isocyanate from the viewpoint of heat resistance. There is no restriction | limiting in particular as such a polyisocyanate component, For example, diisocyanate represented by general formula (V) or polyisocyanate (c) more than trivalence is used individually or in combination of 2 or more types. be able to.

  As the polyisocyanate compound of component (c), 50 to 100% by weight of the total amount is preferably aromatic polyisocyanate, and considering the balance of heat resistance, solubility, mechanical properties, cost, etc., 4 4,4'-diphenylmethane diisocyanate is particularly preferred.

  In the present invention, the diisocyanate (b) obtained by reacting the above general formula (IV) and the diisocyanate represented by the above general formula (V) in the absence of a solvent or in an organic solvent, and the above general formula (V) The blend ratio of the diisocyanates or polyisocyanates (c) having a valence of 3 or more is 0.1 / 0.9 to 0.9 / 0.1 in terms of the equivalent ratio of component (b) / component (c). It is preferable to set it to 0.2 / 0.8 to 0.8 / 0.2, and it is particularly preferable to set it to 0.3 / 0.7 to 0.7 / 0.3. If the equivalent ratio is less than 0.1 / 0.9, the elastic modulus cannot be lowered, and the warpage and adhesion tend to decrease. If the equivalent ratio exceeds 0.9 / 0.1, film properties such as heat resistance can be obtained. Tends to decrease.

  The blending ratio of the trivalent polycarboxylic acid having an acid anhydride group or a derivative thereof (a) and / or the tetravalent polycarboxylic acid having an acid anhydride group (a ′) is as follows: c) The ratio of the total number of carboxyl groups and / or acid anhydride groups of component (a) and / or component (a ′) to the total number of isocyanate groups in the component is 0.6 to 1.4. Is more preferable, 0.7 to 1.3 is more preferable, and 0.8 to 1.2 is particularly preferable. When this ratio is less than 0.6 or exceeds 1.4, it tends to be difficult to increase the molecular weight of the resin containing polyimide bonds.

  The reaction in the process for producing a resin containing an imide bond according to the present invention is carried out by heat condensation in the presence of an organic solvent, preferably a non-nitrogen-containing polar solvent, while removing the generated carbon dioxide gas from the reaction system. It can be carried out.

  Examples of the non-nitrogen-containing polar solvent include ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, and sulfur-containing solvents such as dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, and sulfolane. , Ester solvents such as γ-butyrolactone, cellosolve acetate, ketone solvents such as cyclohexanone, methyl ethyl ketone, aromatic hydrocarbon solvents such as toluene and xylene, and these may be used alone or in combination of two or more. Can be used. It is preferable to select and use a solvent that dissolves the resin to be formed. After the synthesis, it is preferable to use a suitable paste solvent as it is. Γ-Butyrolactone is the most preferable because it is highly volatile, can impart low-temperature curability, and reacts efficiently in a homogeneous system. It is preferable that the usage-amount of a solvent shall be 0.8 to 5.0 times (weight ratio) of resin containing the imide bond to produce | generate. If it is less than 0.8 times, the viscosity at the time of synthesis is too high, and the synthesis tends to be difficult due to the inability to stir. If it exceeds 5.0 times, the reaction rate tends to decrease.

  The reaction temperature is preferably 80 to 210 ° C, more preferably 100 to 190 ° C, and particularly preferably 120 to 180 ° C. If it is less than 80 ° C., the reaction time becomes too long, and if it exceeds 210 ° C., a three-dimensional reaction occurs during the reaction and gelation tends to occur. The reaction time can be appropriately selected depending on the scale of the batch and the reaction conditions employed. If necessary, the reaction may be performed in the presence of a catalyst such as a tertiary amine, an alkali metal, an alkaline earth metal, a metal such as tin, zinc, titanium, cobalt, or a metalloid compound.

The number average molecular weight of the resin containing an imide bond thus obtained is preferably 4,000 to 40,000, more preferably 5,000 to 38,000, and 6,000 to 36. Is particularly preferred. When the number average molecular weight is less than 4,000, film properties such as heat resistance tend to be lowered. When the number average molecular weight is more than 40,000, it is difficult to dissolve in a non-nitrogen-containing polar solvent and easily insolubilizes during synthesis. . In addition, workability tends to be inferior.
In addition, the isocyanate group at the end of the resin can be blocked with a blocking agent such as alcohols, lactams, or oximes after completion of the synthesis.

Various epoxy resins can also be added to the thermosetting resin paste of the present invention in order to improve curability. Examples of the epoxy resin include a bisphenol A type epoxy resin such as Yuka Shell Epoxy Co., Ltd. trade name Epicoat 828, a bisphenol F type epoxy resin such as a trade name YDF-170 manufactured by Tohto Kasei Co., Ltd., and an oiled shell epoxy. Phenol novolac epoxy resins such as trade name Epicoat 152, 154, trade name EPPN-201 manufactured by Nippon Kayaku Co., Ltd., trade name DEN-438 manufactured by Dow Chemical Co., Ltd., and products manufactured by Nippon Kayaku Co., Ltd. Names EOCN-125S, 103S, 104S, etc. o-cresol novolac type epoxy resin, product name Epon 1031S manufactured by Yuka Shell Epoxy Co., Ltd., product name Araldite 0163 manufactured by Ciba Specialty Chemicals Co., Ltd. Product name Denacol EX-611, Multifunctional epoxy resins such as X-614, EX-614B, EX-622, EX-512, EX-521, EX-421, EX-411, EX-321, and trade name Epicoat 604 manufactured by Yuka Shell Epoxy Co., Ltd. Tohoku Kasei Co., Ltd. trade name YH434, Mitsubishi Gas Chemical Co., Ltd. trade name TETRAD-X, TERRAD-C, Nippon Kayaku Co., Ltd. trade name GAN, Sumitomo Chemical Co., Ltd. trade name ELM-120 Amine-type epoxy resins such as Ciba Specialty Chemicals Co., Ltd., trade name Araldite PT810 and other heterocyclic ring-containing epoxy resins, and UCC ERL4234, 4299, 4221 and 4206 such as alicyclic epoxy resins. These can be used alone or in combination of two or more.
Among these epoxy resins, amine-type epoxy resins having 3 or more epoxy groups in one molecule are particularly preferable in terms of improving solvent resistance, chemical resistance, and moisture resistance.

  The epoxy resin used for the thermosetting resin paste of the present invention may contain an epoxy compound having only one epoxy group in one molecule. Such an epoxy compound is preferably used in the range of 0 to 20% by weight with respect to the total amount of the resin including imide bonds. Examples of such an epoxy compound include n-butyl glycidyl ether, phenyl glycidyl ether, dibromophenyl glycidyl ether, and dibromocresyl glycidyl ether. In addition, alicyclic epoxy compounds such as 3,4-epoxycyclohexyl and methyl (3,4-epoxycyclohexane) carboxylate can be used.

The amount of the epoxy resin used in the present invention is preferably 1 to 50 parts by weight, more preferably 2 to 45 parts by weight, and still more preferably 3 to 40 parts by weight with respect to 100 parts by weight of the resin including a polyimide bond. When the compounding amount of the epoxy resin is less than 1 part by weight, the curability, solvent resistance, chemical resistance and moisture resistance tend to decrease, and when it exceeds 50 parts by weight, the heat resistance and viscosity stability tend to decrease. is there.
As an addition method of the epoxy resin, the epoxy resin to be added may be added after dissolving in advance in the same solvent as the solvent contained in the resin containing an imide bond, or may be added directly.

  In the thermosetting resin paste of the present invention, surfactants such as antifoaming agents and leveling agents, and colorants such as dyes or pigments are used to improve the workability during coating and the film properties before and after coating formation. Further, a heat stabilizer, an antioxidant, a flame retardant, a lubricant, and an inorganic ion exchanger can be added.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
Example 1
In a 5-liter four-necked flask equipped with a stirrer, a cooling pipe with an oil / water separator, a nitrogen inlet pipe and a thermometer, PLACEL CD-220 (1,6-hexanediol polycarbonate manufactured by Daicel Chemical Industries, Ltd.) as component (b) Trade name of diol) 1000.0 g (0.50 mol) and 4,4′-diphenylmethane diisocyanate 250.27 g (1.00 mol) and γ-butyrolactone 833.51 g were charged and heated to 140 ° C. Reaction was carried out at 140 ° C. for 5 hours to obtain a diisocyanate [in the general formula (I), R represents all hexamethylene groups, X represents a diphenylmethane group, and m = 13 and n = 1].

  Furthermore, 358.29 g (1.00 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as component (a ′) was added to this reaction solution, and 4,4′- 125.14 g (0.50 mol) of diphenylmethane diisocyanate and 584.97 g of γ-butyrolactone were charged, and the temperature was raised to 160 ° C., followed by reaction for 7 hours to obtain a resin having a number average molecular weight of 30,000. The obtained resin was diluted with γ-butyrolactone to obtain a polyimide resin solution having a viscosity of 65 Pa · s and a nonvolatile content of 40% by weight. The molar ratio of component (b) / component (c) is 0.5 / 0.5.

  To 1000 g of the obtained polyimide resin solution, 600 g of B-30 (trade name, manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 0.3 μm, barium sulfate fine particles) and 900 g of γ-butyrolactone are added, first roughly kneaded, and then 3 high speeds. This kneading was repeated three times using a roll to obtain a polyimide resin paste in which fine particles were uniformly dispersed. 10 parts by weight of YH-434 (trade name of amine type epoxy resin manufactured by Tohto Kasei Co., Ltd., epoxy equivalent of about 120, 4 epoxy groups / molecule) is added to 100 parts by weight of the resin content of this polyimide resin paste, and γ- Dilution with butyrolactone gave a polyimide resin paste having a viscosity of 36 Pa · s, a TI value of 2.0, and a nonvolatile content of 40% by weight.

Example 2
In Example 1, in place of B-30 and 600 g, B-2 (trade name, average particle diameter 2 μm, barium sulfate fine particles) 600 g was used in the same manner as Example 1 except that B-2 (trade name, Sakai Chemical Industry Co., Ltd.) was used. Operation was performed to obtain a polyimide resin paste having a viscosity of 31 Pa · s, a TI value of 1.8, and a nonvolatile content of 40% by weight.

Example 3
In Example 1, instead of B-30 and 600 g, SG-2000 (trade name, average particle diameter 5 μm, talc fine particles) 600 g instead of SG-2000 was used, exactly the same operation as in Example 1. And a polyimide resin paste having a viscosity of 32 Pa · s, a TI value of 2.0, and a nonvolatile content of 40% by weight was obtained.

Comparative Example 1
In Example 1, instead of B-30 and 600 g, the same operation as in Example 1 was performed except that 600 g of BA (trade name, manufactured by Sakai Chemical Industry Co., Ltd., average particle diameter: 8 μm, barium sulfate fine particles) was used. And a polyimide resin paste having a viscosity of 28 Pa · s, a TI value of 1.7, and a nonvolatile content of 40% by weight was obtained.

Comparative Example 2
In Example 1, instead of B-30 and 600 g, the same operation as in Example 1 was performed except that 600 g of SSS (trade name manufactured by Nippon Talc Co., Ltd., average particle diameter 12 μm, talc fine particles) was used. A polyimide resin paste having a viscosity of 30 Pa · s, a TI value of 1.8, and a nonvolatile content of 40% by weight was obtained.

The characteristics of the polyimide resin pastes obtained in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 1.
(1) Warpage property A two-layer flexible substrate made of a polyimide film having a thickness of 38 μm and Cu having a thickness of 12 μm is Sn-plated and cut into a size of 35 mm in length and 20 mm in width. The obtained polyimide resin paste is printed on this substrate, heated at 120 ° C. for 120 minutes in an air atmosphere, and the obtained test piece (coating thickness: 15 μm) is fixed with the coated surface facing down. The warp height was evaluated by placing on the board.
(2) Adhesiveness to the sealing material (1) The polyimide resin paste obtained is printed on the base material used for warpage, and heated at 120 ° C. for 120 minutes in an air atmosphere. 0.06 g potting epoxy type sealing material [trade name CEL-C-5020 manufactured by Hitachi Chemical Co., Ltd.] on the film thickness: 15 μm), 120 minutes at 120 ° C. in air atmosphere, and 150 ° C. Heat for 120 minutes. The obtained test piece was bent so that the sealing material side was the outside, and the peeling mode was evaluated according to the following criteria.
: Interfacial peeling of substrate / coating film: Interfacial peeling of coating film / encapsulant ×: No adhesion (3) Migration resistance The wiring pitch of a polyimide film with a thickness of 38 μm and a Cu comb electrode with a thickness of 8 μm Sn-plating is performed on a two-layer flexible base material having a pitch of 30 μm (inter-wiring length: 15 μm). The obtained polyimide resin paste is printed on this substrate and heated at 120 ° C. for 120 minutes in an air atmosphere. A voltage of 60 V was applied to the wiring of the obtained test piece (coating thickness: 15 μm) in an environment of 85 ° C./85% RH, and the insulation resistance value after 1000 hours was evaluated according to the following criteria.
: Insulation resistance 10 ⁸ or more ×: after insulation resistance less than 10 ⁸ (4) Tensile modulus and elongation obtained polyimide resin paste was dried for 15 minutes at 90 ° C., under an air atmosphere, 120 minutes or 160 ° C. at 120 ° C. For 60 minutes to form a cured film having a thickness of about 30 μm, a width of 10 mm, and a length of 60 mm. Using the obtained cured film, a tensile test was performed under the conditions of a length between chucks of 20 mm and a pulling speed of 5 mm / min to obtain a tensile elastic modulus and a tensile elongation.
(5) 5% weight loss temperature After the obtained polyimide resin paste was dried at 90 ° C. for 15 minutes, it was heated in an air atmosphere at 120 ° C. for 120 minutes or 160 ° C. for 60 minutes to form a cured film having a thickness of about 30 μm. Form. Using the obtained cured film, a 5% weight reduction temperature was measured by a TG-DTA method in an air atmosphere at a heating rate of 10 ° C./min.

As shown in Table 1, it can be seen that all of Examples 1 to 3 have better tensile elongation and better migration resistance than the comparative examples.

Claims (4)

  In the thermosetting resin paste used for a wiring board containing a thermosetting resin and inorganic fine particles, (A) 100 parts by weight of the thermosetting resin, (B) 1/2 of the length between wirings of the wiring board. A thermosetting resin paste containing 10 to 1000 parts by weight of inorganic fine particles having an average particle size of less than 1.   The thermosetting resin paste according to claim 1, wherein the tensile elastic modulus is 1.0 GPa or less at 25 ° C and the tensile elongation is 20% or more at 25 ° C.   The thermosetting paste according to claim 1 or 2, wherein the thermosetting paste has a 5% thermogravimetric reduction temperature of 250 ° C or higher. The flexible wiring board which used the thermosetting resin paste in any one of Claim 1 to 3 as a protective film.