JP2006328145A - Adhesive composition for coverlay of flexible printed circuit board and the flexible printed circuit board given by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition for a coverlay, free from halogen, excellent in resistance to migration, flame retardancy, and peeling strength, and used in a flexible printed circuit board, and to provide the flexible printed circuit board given by using the same. <P>SOLUTION: This halogen-free adhesive composition is used for the coverlay of the flexible printed circuit board, wherein the adhesive composition for the coverlay contains an elastomer (A), a thermosetting component (B), a metal hydroxide, (D) a curing agent, and (E) a silicone oligomer. The elastomer (A) preferably has one or more functional groups reactive with a thermosetting resin of the thermosetting component (B). Further, a surface of the metal hydroxide (C) is preferably treated with the silicone oligomer (E). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive composition for a coverlay used for a flexible printed wiring board that is halogen-free and excellent in migration resistance, and a flexible printed wiring board using the same.

  In recent years, electronic devices have become smaller, thinner, and higher in performance, and flexible printed wiring boards (hereinafter referred to as FPC) that can be bent are frequently used as printed wiring boards. The FPC is required to have excellent properties such as mechanical properties, thermal properties, chemical resistance, flame retardancy, and adhesiveness. Furthermore, since the wiring pitch is reduced to increase the density of the FPC, high migration is also required.

  A coverlay is an adhesive layer provided on one side of a polyimide film or a polyester film, and is laminated on the FPC via an adhesive layer to strengthen the adhesion between the film and the copper foil, and bend and displace. It is used to prevent disconnection of the circuit when it is exposed, to maintain insulation of the circuit, and to prevent moisture from entering and rusting from the outside.

  Conventionally, in order to impart flame retardancy to an adhesive used for a coverlay, a method using a halogen compound such as bromine in an adhesive composition or a method using an antimony compound as an auxiliary agent is known.

  However, since halogen compounds may generate dioxins during combustion, use restrictions are desired due to recent environmental problems. Similarly, antimony compounds are also being regulated as environmentally hazardous components, and the development of coverlays using halogen-free flame retardants that do not contain them is desired.

For this reason, there is a method of adding a phosphorus compound such as a phosphate ester in order to satisfy the flame retardancy without halogen. However, when a large amount of phosphate ester is added to impart flame retardancy, there is a problem that migration resistance is remarkably lowered. In addition, there is a method of adding a nitrogen compound, a silicone compound, and a metal hydroxide, but the flame retardant effect is lower than that of halogen or phosphorus compounds, and it is necessary to add a large amount to satisfy the flame retardancy. There is a problem that the adhesive strength is lowered. When a metal hydroxide is added, dispersibility is also a problem. As a method for improving the dispersibility of the metal hydroxide, there is a method of using a filler whose surface is previously treated with a surface treatment agent such as a coupling agent (see Patent Documents 1 to 3). However, since the types of commercially available treatment fillers are very limited, it is difficult to select treatment fillers suitable for various resin compounding systems.
For this reason, a method using a combination of a phosphoric acid ester and a plurality of flame retardants such as metal hydroxides and nitrogen compounds has been adopted, but a ratio that sufficiently satisfies adhesiveness, flame retardancy, contamination, and other characteristics. It is difficult to find.

JP-A 63-230729 Japanese Patent Publication No.62-40368 JP-A-61-272243

  The present invention has been made in view of the above-mentioned problems of the prior art. The object of the present invention is to provide a new means for improving the adhesiveness at the interface between an inorganic filler and a resin, thereby It is an object to provide an adhesive composition for a coverlay used for a flexible printed wiring board which is free and excellent in migration resistance, flame resistance and peel strength, and a flexible printed wiring board using the same.

  As a result of intensive research to solve these problems, the surface of the metal hydroxide is treated with a silicone oligomer, so that the decrease in adhesion is reduced and the amount of metal hydroxide added can be increased. It was. That is, the present inventors have found an adhesive composition for an FPC coverlay that has excellent adhesion, flame retardancy, and migration resistance while being halogen-free.

That is, the present invention is [1] a halogen-free adhesive composition used for a cover lay of a flexible printed wiring board, comprising an elastomer (A), a thermosetting component (B), a metal hydroxide (C), The present invention relates to an adhesive composition for a coverlay containing a curing agent (D) and a silicone oligomer (E).
The present invention also provides [2] the coverlay as described in [1] above, wherein the elastomer (A) has a functional group capable of reacting with the thermosetting resin of the thermosetting component (B). The present invention relates to an adhesive composition.
The present invention also relates to [3] the adhesive composition for coverlay according to [1] or [2] above, wherein the surface of the metal hydroxide (C) is treated with the silicone oligomer (E). .
[4] The coverlay adhesive according to any one of [1] to [3], wherein [4] the thermosetting component (B) is at least one of an epoxy resin and a phenol resin. Relates to the composition.
In the present invention, [5] silicone oligomer (E) is difunctional siloxane unit (R ₂ SiO _2/2 ), trifunctional siloxane unit (RSiO _3/2 ) and tetrafunctional siloxane unit (SiO _{4). / 2} ) (in the formula, R is an organic group, and the R groups in the silicone oligomer may be the same or different from each other). The coverlay adhesive composition according to any one of [1] to [4] above, which is a silicone oligomer having 2 to 70 and having at least one functional group that reacts with a hydroxyl group at a terminal.
The present invention also relates to [6] a flexible printed wiring board using the coverlay adhesive composition according to any one of [1] to [5].

  According to the present invention, the elastomer (A), the thermosetting component (B), the metal hydroxide (C), the curing agent (D), and the silicone oligomer (E) are contained as essential components. It is possible to provide an FPC adhesive composition excellent in flame retardancy, migration resistance and peel strength, and a flexible printed wiring board having these properties by treating the surface of the oxide (C). it can.

Hereinafter, embodiments of the present invention will be specifically described.
As the elastomer (A) used in the present invention, acrylic rubber, acrylic acid alkyl ester (including methacrylic acid ester, the same shall apply hereinafter) as a main component, vinyl monomer, and acrylonitrile, styrene, etc. Polymer, polyisoprene, polybutadiene, carboxyl group-terminated polybutadiene, hydroxyl-terminated polybutadiene, 1,2-polybutadiene, carboxyl-terminated 1,2-polybutadiene, hydroxyl-terminated 1,2-polybutadiene, styrene-butadiene rubber, hydroxyl-terminated styrene-butadiene Rubber, acrylonitrile-butadiene rubber, carboxyl group, hydroxyl group, acrylonitrile-butadiene rubber containing carboxyl group, (meth) acryloyl group or morpholine group at the polymer end, carboxylated nitrile rubber, hydroxyl group terminated poly (oxy Lopyrene), alkoxysilyl group-terminated poly (oxypropylene), poly (oxytetramethylene) glycol, polyolefin glycol, poly-ε-caprolactone, styrene-butadiene-styrene copolymer, butyl rubber, chloroprene rubber, nitrile rubber, acrylonitrile-butadiene -A methacrylic acid copolymer, a styrene-isoprene copolymer, a styrene-butylene-styrene block copolymer, a styrene-ethylene-butylene-styrene block copolymer, and the like, but are not limited thereto.
These elastomers (A) preferably have a functional group that reacts with either an epoxy resin or a phenol resin, or both. The elastomer (A) used in the present invention can be used without any particular limitation in molecular weight, composition, and the like.

  Examples of the functional group that reacts with either or both of the epoxy resin and phenol resin of the elastomer (A) used in the present invention include a carboxyl group, an epoxy group, and a hydroxyl group. Although it does not restrict | limit to these as a functional group, A carboxyl group is preferable from surfaces, such as reactivity and versatility.

As the thermosetting component (B) used in the present invention, from the viewpoint of reactivity and heat resistance, any one of phenol resin and epoxy resin or a mixture of two or more of these may be used. Molecular weight, softening point, The hydroxyl equivalent is not particularly limited.
Epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins and other bisphenol type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and bisphenol A novolak type epoxy resins. Type epoxy resin, cycloaliphatic epoxy resin, aliphatic chain epoxy resin, diglycidyl etherified product of biphenol, diglycidyl etherified product of naphthalenediol, diglycidyl etherified product of phenol, diglycidyl etherified product of alcohol, and these And alkyl-substituted products, hydrogenated products, and the like. One type of epoxy resin may be used alone, or two or more types may be mixed and used.

Phenol resins are phenols and aldehydes that are reacted with acid or alkali as a catalyst. Phenols, such as phenol, metacresol, paracresol, orthocresol, isopropylphenol, and nonylphenol are used as aldehydes. , Formaldehyde, paraformaldehyde, acetaldehyde, paraacetaldehyde, butyraldehyde, octylaldehyde, benzaldehyde and the like, and are not particularly limited. In general, formaldehyde or paraformaldehyde is used. In addition, a vegetable oil-modified phenol resin can also be used. The vegetable oil-modified phenol resin is obtained by reacting phenols and vegetable oil in the presence of an acid catalyst, and then reacting aldehydes in the presence of an alkali catalyst. Examples of the acid catalyst include p-toluenesulfonic acid. Examples of the alkali catalyst include amine catalysts such as ammonia, trimethylamine, and triethylamine.
Further, as the thermosetting component (B), xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyimide resin, polyurethane resin, cyanate resin, maleimide resin, benzocyclobutene resin, etc. Can be used.

  There is no restriction | limiting in particular as a metal hydroxide (C) used by this invention, If it is an electrical insulation essentially, it can be used. Examples thereof include aluminum hydroxide, magnesium hydroxide, dolomite, hydrotalcite, calcium hydroxide, barium hydroxide, zirconium hydroxide and the like. In the present invention, aluminum hydroxide is particularly preferable. Aluminum hydroxide is preferable because it has few ionic impurities and is low in cost, and is widely used for electronic materials including FPC. These can be used alone or in combination of two or more as required. There is no restriction | limiting in particular about the shape of a inorganic filler, and a particle size, Usually, the particle size of 0.01-50 micrometers, Preferably 0.1-15 micrometers is used suitably. The compounding amount of these metal hydroxides is preferably in the range of 50 to 200 parts by weight with respect to 100 parts by weight of the total resin solids (A) + (B). If it is less than 50 parts by weight, there is a tendency that sufficient flame retardancy cannot be obtained, and if it exceeds 200 parts by weight, the normal peel adhesion strength tends to decrease.

  In the coverlay adhesive composition of the present invention, a flame retardant other than a metal hydroxide and a compounding agent for additives can be added as necessary.

  Examples of flame retardants used in combination with metal hydroxides include phosphorus flame retardants, nitrogen flame retardants, silicone flame retardants, and inorganic flame retardants, which can be added within a range that does not deteriorate the characteristics.

As the phosphorus-based flame retardant, both inorganic and organic compounds can be used as long as they are compounds containing phosphorus atoms. Examples of the inorganic compound include phosphoric acids such as red phosphorus, monoammonium phosphate, diammonium phosphate, triammonium phosphate, and ammonium polyphosphate, which may be surface-treated for the purpose of preventing hydrolysis and the like. Examples thereof include inorganic nitrogen-containing phosphorus compounds such as ammonium and phosphoric acid amide.
Examples of the organic phosphorus compound include a phosphate ester compound, a phosphonic acid compound, a phosphinic acid compound, a phosphine oxide compound, a phosphorane compound, and an organic nitrogen-containing phosphorus compound.

  The nitrogen-based flame retardant is not particularly limited as long as it is a compound containing a nitrogen atom, and examples thereof include triazine compounds, cyanuric acid compounds, isocyanuric acid compounds, phenothiazines, triazine compounds, cyanuric acid compounds, Isocyanuric acid compounds are preferred.

  The silicone flame retardant is not particularly limited as long as it is an organic compound containing a silicon atom, and examples thereof include silicone oil, silicone rubber, and silicone resin.

  Examples of inorganic flame retardants include metal carbonate compounds, boron compounds, and low-melting glass.

  The curing agent (D) used in the present invention acts as a curing agent and a curing catalyst for the resin. As these, various conventionally known ones can be used, for example, diaminodiphenylmethane, diaminodiphenylsulfone, pyromellitic anhydride, aromatic polyamine, boron trifluoride amine complex such as boron trifluoride triethylamine complex, Imidazole derivatives such as 1-alkyl-2-phenylimidazole, 2-alkyl-4-methylimidazole, 2-phenyl-4-alkylimidazole, organic acids such as phthalic anhydride and trimellitic anhydride, dicyandiamide, triphenylphosphine Known compounds such as diazabicycloundecene, hydrazine, polyfunctional phenols such as phenol novolac and cresol novolak, organic phosphorus compounds, tertiary amines, and quaternary ammonium salts can be used. In addition, these hardening | curing agents (curing catalyst) may be used independently, and may use 2 or more types together as needed.

  If the silicone oligomer (E) used by this invention has one or more functional groups which react with a hydroxyl group at the terminal, there will be no restriction | limiting in particular in the molecular weight, a structure, etc.

The silicone oligomer (E) used in the present invention is preferably preliminarily three-dimensionally cross-linked, and accordingly, a bifunctional siloxane unit (R ₂ SiO _2/2 ), a trifunctional siloxane unit (RSiO _3/2 ). And tetrafunctional siloxane units (SiO _4/2 ) (wherein R is an organic group, for example, an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group, or an aryl having 6 to 12 carbon atoms such as a phenyl group) R group in the silicone oligomer may be the same as or different from each other, and at least one siloxane unit selected from 2 to 70 (converted from the weight average molecular weight by GPC). For example, a bifunctional siloxane unit, a trifunctional siloxane unit, a tetrafunctional siloxane unit, a bifunctional siloxane unit and a trifunctional siloxane unit, a trifunctional siloxane unit, Examples thereof include those composed of tetrafunctional siloxane units, those composed of bifunctional siloxane units and tetrafunctional siloxane units, and those composed of bifunctional siloxane units, trifunctional siloxane units and tetrafunctional siloxane units. Moreover, although the polymerization degree of a silicone oligomer is a thing of 2-70, Preferably, it is a polymerization degree 6-70, More preferably, it is 10-50. If the degree of polymerization is less than 2, a sufficient three-dimensional crosslinked structure cannot be obtained, and if a silicone oligomer having a degree of polymerization of more than 70 is used, uneven treatment may occur during surface treatment and heat resistance may be reduced.

Here, the bifunctional siloxane unit (R ₂ SiO _2/2 ), the trifunctional siloxane unit (RSiO _3/2 ), and the tetrafunctional siloxane unit (SiO _4/2 ) each have the following structure.
R R O-
｜ ｜ ｜
-O-Si-O- -O-Si-O- -O-Si-O-
｜ ｜ ｜
R O- O-

R ₂ SiO _2/2 , RSiO _3/2 , SiO _4/2

As for the compounding quantity of the silicone oligomer (E) used by this invention, 0.01 to 50 weight% is preferable with respect to a metal hydroxide (C). If it is less than 0.01% by weight, the effect of improving the interfacial adhesion may be insufficient, and if it exceeds 50% by weight, the heat resistance and the like tend to decrease.
The treatment with the silicone oligomer (E) on the surface of the metal hydroxide (C) is performed by blending the silicone oligomer (E) into the dispersion of the metal hydroxide (C) and treating the surface of the metal hydroxide (C) in advance. And you may mix | blend another elastomer (A), a thermosetting component (B), and a hardening | curing agent (D) to this. Further, (A), (B), (C), (D), and (E) may be blended in any order.

  The FPC coverlay adhesive composition of the present invention can be used by dissolving or dispersing in an organic solvent. The organic solvent is not particularly limited, and examples thereof include ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, aromatic solvents such as toluene, alcohol solvents such as methanol and ethanol, N-methylpyrrolidone, N, N-dimethylformamide. An amide solvent such as may be used.

  The adhesive solution of the FPC coverlay adhesive composition of the present invention can be directly coated on a polyimide film, a polyester film, a liquid crystal polymer film, etc., and dried with an organic solvent to form a coverlay. Although it does not restrict | limit especially as a coating method, It can carry out by well-known methods, such as a roll coater, a reverse roll coater, a comma coater, a gravure coater, an air knife coater, a die coater, a bar coater. Moreover, drying can be performed at 60-150 degreeC and about 5 to 30 minutes.

Although it does not restrict | limit especially as a polyimide film used for said use, For example, Kapton (brand name, Toray DuPont Co., Ltd. product), Apical (brand name, Kaneka Co., Ltd. product), Upilex (brand name: Ube Industries, Ltd.) can be used.
Although it does not restrict | limit especially as a polyester film used for said use, For example, a polyethylene terephthalate, a polybutylene terephthalate, a polyethylene naphthalate etc. can be used.
Although it does not restrict | limit especially as a liquid crystal polymer film used for said use, For example, a polyacrylate type liquid crystal polymer etc. can be used.
The polyimide film, polyester film, and liquid crystal polymer film are not particularly limited in film thickness, but those having a thickness of 10 to 100 μm are usually used.

  Next, the present invention will be specifically described using examples and comparative examples.

Example 1
(1) Production of silicone oligomer solution A glass flask equipped with a stirrer, condenser and thermometer was charged with a solution containing 40 g of tetramethoxysilane and 93 g of methanol, and then 0.47 g of acetic acid and 18.9 g of distilled water were added. The mixture was stirred at 50 ° C. for 8 hours to synthesize a silicone oligomer having a degree of polymerization of siloxane units of 20 (converted from a weight average molecular weight by GPC, the same applies hereinafter). The obtained silicone oligomer has a methoxy group and / or a silanol group as a terminal functional group that reacts with a hydroxyl group.
Methanol was added to the obtained silicone oligomer solution to prepare a silicone oligomer treatment liquid having a solid content of 10% by weight.
(2) Preparation of adhesive composition solution for coverlay After dispersing 100 parts by weight of Heidilite H-42M (aluminum hydroxide; manufactured by Showa Denko KK) in methyl ethyl ketone, Example 1 (1) as a silicone oligomer The silicone oligomer treatment solution prepared in (1) was added to 15 parts by weight, and the mixture was stirred for 30 minutes at room temperature (25 ° C.) to treat the surface of aluminum hydroxide with the silicone oligomer. To this solution, 50 parts by weight of WS023DR (acrylic rubber; manufactured by Teikoku Chemical Industry Co., Ltd.), 30 parts by weight of YDCN703 (cresol novolac type epoxy resin; manufactured by Tohto Kasei Co., Ltd.), and 2anol (resole type phenol resin; Hitachi Chemical Co., Ltd.) 20 parts by weight) was added. Further, a mixture of the above mixed solution and 0.5 part by weight of dicyandiamide as a curing agent for epoxy resin was used as an adhesive composition solution for coverlay.
(3) Preparation of coverlay Using a comma coater, apply and dry the adhesive solution to apical NPI (12.5 μm thickness, manufactured by Kaneka Corporation) so that the thickness of the adhesive layer after drying is 25 μm. A coverlay was prepared.

(Example 2)
In Example 1, as a flame retardant, aromatic phosphate ester condensation type flame retardant PX-200 (phosphorus content 9% by weight, manufactured by Daihachi Chemical Industry Co., Ltd.) is 10 parts by weight, and the number of parts of aluminum hydroxide is 70. A coverlay was produced in the same manner as in Example 1 except that the amount was 10 parts by weight and the silicone oligomer treatment solution was 10 parts by weight.

(Example 3)
A coverlay was produced in the same manner as in Example 1 except that the acrylic rubber WS023DR was changed to PNR-1H (made by Nippon Zeon Co., Ltd.) as the acrylic rubber.

Example 4
A coverlay was produced in the same manner as in Example 1 except that 80 parts by weight of the acrylic rubber WS023DR, 17 parts by weight of the epoxy resin YDCN703, and 3 parts by weight of the phenolic resin H2181S were used.

(Comparative Example 1)
In Example 1, a coverlay was produced in the same manner as in Example 1 except that the silicone oligomer treatment liquid was changed to 0 part by weight.

(Comparative Example 2)
A coverlay was produced in the same manner as in Example 1 except that aluminum hydroxide was 0 parts by weight, silicone oligomer treatment liquid was 0 parts by weight, and PX-200 was 50 parts by weight.

(Comparative Example 3)
A coverlay was prepared in the same manner as in Example 1 except that WS023DR was 100 parts by weight, YDCN703 was 0 parts by weight, Hitanol 2181 was 0 parts by weight, and dicyandiamide was 0 parts by weight.

(Evaluation methods)
(1) Peeling adhesive strength A coverlay film and a 35 μm-rolled copper foil were bonded to each other with a 100 ° C. laminating roll (linear pressure 5 kgf / cm, laminating speed 1 m / min). Then, it hardened using the press (temperature 170 degreeC, pressure 1MPa, 60 minutes), and it was set as the test piece. The cured specimen was measured in accordance with JIS K 6854-3, and the T-peeling adhesive strength was measured. The peeling temperature was 23 ° C., and the peeling speed was 50 mm / min.

(2) Reflow soldering heat resistance The coverlay film and 35 μm rolled copper foil were bonded together with a laminating roll (linear pressure 5 kgf / cm, laminating speed 1 m / min) at 100 ° C. Then, it hardened using the press (temperature 170 degreeC, pressure 1MPa, 60 minutes), and it was set as the test piece. According to JIS C 6481, the test piece was left in a humidified condition (temperature 40 ° C., humidity 80%) for 12 hours, and then the sample surface maximum temperature 260 was measured using a reflow soldering apparatus (RF430 manufactured by Nippon Pulse Laboratories). The test piece was heated so that it might become degree C, and the presence or absence of the swelling of the adhesive bond layer was observed.
(3) Migration resistance The test apparatus used was a migration apparatus manufactured by IMV Co., Ltd. and a constant temperature and humidity chamber manufactured by Hirayama Manufacturing Co., Ltd. For the test piece, a comb-shaped electrode having a circuit width and a circuit interval of 75 μm was prepared for testing on a flexible copper-clad laminate, and the coverlay film prepared above was laminated, under the conditions of 170 ° C., pressure 1 MPa, 60 minutes. Pressed and cured samples were used. The sample was placed in a constant temperature and humidity chamber having a temperature of 85 ° C. and a humidity of 85% RH, a 50 V DC voltage was continuously applied between the electrodes for 1000 hours, and the resistance value in humidity was continuously measured. The evaluation was performed by observing the presence or absence of a decrease in resistance value and the presence or absence of dendrite between the electrodes after the test.
(4) Flame resistance test The flame resistance of the coverlay was evaluated by a method based on UL94 VTM-0.
Table 1 summarizes the measurement results of peel adhesion strength, reflow solder heat resistance, migration resistance, and flame resistance test according to the evaluation method described above.

Parts in the table are parts by weight excluding the solvent. Reflow solder heat resistance: ○: No swelling, ×: Migration resistance: ◎: No decrease in resistance, no dendrite, ○: No decrease in resistance, There is a small amount of dendrite (no continuity between anode and cathode), x: There is a decrease in resistance value, and dendrite is generated.

In Comparative Example 1 which does not contain the elastomer (A) and the silicone oligomer (E), the peel adhesion strength and the migration resistance are inferior. Further, Comparative Example 2 which does not contain the elastomer (A), the silicone oligomer (E) and the metal hydroxide (C) is excellent in peel adhesion strength, but is inferior in reflow soldering heat resistance and migration resistance. And the comparative example 3 which does not contain a thermosetting component (B) and a hardening | curing agent (D) is inferior to reflow solder heat resistance, migration resistance, and a flame retardance. On the other hand, the adhesive for coverlay of a flexible printed wiring board containing the elastomer (A), thermosetting component (B), metal hydroxide (C), curing agent (D) and silicone oligomer (E) of the present invention. The agent composition and the flexible printed wiring board using the same are excellent in peel adhesion strength, reflow soldering heat resistance, migration resistance, and flame retardancy.

Claims (6)

A coverlay adhesive composition comprising an elastomer (A), a thermosetting component (B), a metal hydroxide (C), a curing agent (D), and a silicone oligomer (E). 2. The coverlay adhesive composition according to claim 1, wherein the elastomer (A) has a functional group capable of reacting with the thermosetting resin of the thermosetting component (B). The coverlay adhesive composition according to claim 1 or 2, wherein the surface of the metal hydroxide (C) is treated with the silicone oligomer (E). The coverlay adhesive composition according to any one of claims 1 to 3, wherein the thermosetting component (B) is one or more of an epoxy resin and a phenol resin. The silicone oligomer (E) is difunctional siloxane unit (R ₂ SiO _2/2 ), trifunctional siloxane unit (RSiO _3/2 ) and tetrafunctional siloxane unit (SiO _4/2 ) (wherein R is It is an organic group, and R groups in the silicone oligomer may be the same or different from each other) and contain at least one siloxane unit selected from 2 to 70. The coverlay adhesive composition according to any one of claims 1 to 4, which is a silicone oligomer having at least one functional group that reacts with. The flexible printed wiring board using the adhesive composition for coverlays in any one of Claims 1 thru | or 5.