JP2003082317A - Adhesive composition of flexible printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition having a high glass transition temperature and a long storage period. SOLUTION: The adhesive composition comprises (a) an epoxy resin, (b) an accelerator having a structure of one of formulae (I) and (II) (wherein E is sulfur, nitrogen or phosphorus; Ar is an aromatic ring; R<1> is the same or different and is a substituted or unsubstituted univalent hydrocarbyl group, a hydroxy group, an alkoxy group, a nitro group, a cyano group or a halogen atom; R<2> and R<3> are each a hydrogen atom or a methyl group; R<4> is the same or different and is a substituted or unsubstituted univalent hydrocarbyl group; R<5> is a substituted or unsubstituted pyridinium group; a is an integer of 0-2; and b is an integer of 2-3), (c) a nitrile rubber bearing a carboxy group, and (d) an inorganic filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition for use in flexible printed circuit boards, and more particularly, it has a high glass transition temperature (Tg) and a long storage period, and contains an epoxy resin and an accelerator. , Nitrile rubber having a carboxyl group,
And an adhesive composition containing an inorganic filler and having improved coating and processability on a flexible printed circuit board.

[0002]

2. Description of the Related Art Flexible printed circuit boards (FPC boards) are also called bendable printed circuit boards, and because of their flexibility, they can be assembled in three dimensions depending on the space of the final product. Currently, high-tech products such as cameras, video cameras, hi-fi devices, disk players, printers and mobile phones are light, thin, short and small. Therefore, the flexible printed circuit board has become one of the important parts of high-tech products.

The structure of a flexible printed circuit board is divided into five basic parts: prepreg, copper foil, substrate, surface treatment layer and reinforcing layer. The first three parts are the main parts of the flexible printed circuit board and are assembled by adhesive. Therefore, the quality of flexible printed circuit boards depends on the heat resistance and shelf life of this adhesive. The effectiveness and stability of this adhesive is affected by the heat, ambient temperature and moisture content generated by the operation of the flexible printing plate. Therefore, this adhesive mainly has a high glass transition temperature and a long storage period at room temperature.

Republic of China Patent Publication No. 279255 (Application No.
84105059) discloses an epoxy resin composition applied for packaging semiconductor devices. However, while the above patents are used to package semiconductor devices, they are not used to enhance flexible printed circuit boards. Furthermore, in order to improve the releasability of the epoxy resin composition, silicone oil, a fluorinated type surfactant,
Release agents such as waxes, liquid paraffin and metal salts of stearic acid must be included.

US Pat. No. 5,162,140 discloses flexible printed circuit boards and adhesives. However, the accelerator contained in this adhesive is a Lewis acid salt, not an onium salt of hexafluoroantimonic acid. US Patent No. 5,26
No. 0,130 discloses an adhesive for flexible printed circuit boards, which must contain a curing agent and an accelerator. This accelerator is a boron fluoride of zinc, tin or nickel rather than an onium salt of hexafluoroanthmonic acid.

The above patents are not used to improve the glass transition temperature and shelf life of flexible printed circuit board adhesives.

The present invention discloses an adhesive composition containing an epoxy resin, an accelerator, a nitrile rubber having a carboxyl group, and an inorganic filler in accordance with the market demand for a flexible printed circuit board. The present invention provides an adhesive composition having a high glass transition temperature (140 ° C to 170 ° C) and a long storage period (50 days or more) by using an onium salt of hexafluoroantimonic acid as its accelerator. I will provide a. Therefore, it is avoided that the printed circuit board had limited applications due to the instability of the adhesive.

[0008]

The main object of the present invention is to provide a glass transition temperature (T) for use in flexible printed circuit boards.
It is an object of the present invention to provide an adhesive composition containing an epoxy resin having a high g) and a long storage period, an accelerator such as an onium salt of hexafluoroantimonic acid, a nitrile rubber having a carboxyl group, and an inorganic filler.

[0009]

SUMMARY OF THE INVENTION The present invention provides an adhesive composition for use in flexible printed circuit boards which has the characteristics of heat resistance, high glass transition temperature, long shelf life at room temperature and fast curing reaction. provide. This adhesive composition comprises (a) an epoxy resin, (b) an accelerator having one structure represented by the following formula:

[Chemical 4] (In the above formula, E represents sulfur, nitrogen or phosphorus, Ar represents an aromatic ring, R ¹ is the same or different, and a substituted or unsubstituted monovalent hydrocarbon group, a hydroxyl group, an alkoxy group, a nitro group. Represents a group, a cyano group or a halogen atom, and R
² and R ³ each represent a hydrogen atom or a methyl group, R ⁴ is the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group, R ⁵ represents a substituted or unsubstituted pyridinium group, and a represents Represents an integer of 0 to 2 and b represents an integer of 2 to 3) (c) Carboxyl group-containing nitrile rubber, preferably carboxyl-terminated butadiene acrylonitrile, and (d) inorganic filler, preferably aluminum hydroxide , The mass ratio of accelerator to epoxy resin is 0.008:
The mass ratio of the nitrile rubber to the epoxy resin is 1: 5 to 10: 1, and the mass ratio of the inorganic filler to the epoxy resin is 1: 2 to 2: 1.

The molecular structure of the epoxy resin in component (a) is
There is no limitation as long as each monomer contains two or more epoxy groups. The epoxy resin of the present invention can be used alone or in combination of two or more kinds. Further, the component (a) of the present invention is (1) a curable epoxy resin that is liquid at ambient temperature, or (2) a curable epoxy resin that is liquid at ambient temperature and a solid curable epoxy resin (the curability of this solid is The epoxy resin is a curable liquid mixture that exhibits a liquid state at ambient temperature upon dilution with a diluent. Here, “liquid at ambient temperature” means 25
It means that it has fluidity in the range of ℃ to 40 ℃ and includes a so-called semi-solid state.

The curable epoxy resin (1) is liquid at ambient temperature and has a bisphenol A type epoxy resin having an average molecular weight of about 500 or less, a bisphenol F type epoxy resin, a phenol novolac type epoxy having an average molecular weight of about 500 or less. Resin, 1,2-epoxyethyl-
3,4-epoxycyclohexane, 3,4-epoxycyclohexylcarboxylic acid-3,4-epoxycyclohexylmethyl and bis (3,4-epoxy-6-methylcyclohexylmethyl)
Acyclic epoxy resin such as adipate, diglycidyl hexahydrophthalate, glycidyl ether type epoxy resin such as diglycidyl 3-methylhexahydrophthalate and diglycidyl hexahydroterephthalate, diglycidyl aniline, diglycidyl toluidine,
Glycidylamine-type epoxy resins such as triglycidyl-p-aminophenol, tetraglycidyl-m-xylenediamine and tetraglycidylbis (aminomethyl) cyclohexane, as well as 1,3-diglycidyl-5-methyl-5-ethylhydantoin Includes various hydantoin type epoxy resins.

The curable epoxy resin (2) is a mixture of a liquid curable epoxy resin and a solid curable epoxy resin at ambient temperature. The liquid curable epoxy resin is as described above. Solid curable epoxy resins such as bisphenol F type epoxy resin, novolac type epoxy resin, acyclic epoxy resin, glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, triazine type epoxy resin and hydantoin type epoxy resin are diluents. It can be used in the present invention after dilution. Here, any diluent that can dissolve or disperse the epoxy resin and maintain its fluidity can be used in the present invention.

The component (b) is represented by the following formula (I) or (II).

[Chemical 5] (In the ^{formula, E, Ar, R 1,} R 2, R 3, R 4, R 5, a and b have the same meaning as above) formula (I) of component (b) is -C (R ₂ R ₃₎ - is an onium hexafluoroantimonate having sulfur, an aromatic ring attached to the nitrogen or phosphorus atom through a group. This aromatic ring A
r is a benzene ring, a naphthalene ring, an anthracene ring or a pyrene ring. A benzene ring is preferred because it is easy to synthesize.

The aromatic ring Ar may be unsubstituted or 1
R above¹May be replaced with. R¹Group is straight-chain or
Branched chain alkyl groups such as methyl, ethyl, propyl,
Butyl, pentyl, octyl, decyl, dodecyl and te
Tradecyl, cycloalkyl groups such as cyclohexyl
Group, aryl group such as phenyl and naphthyl, alka
Reel groups such as tolyl and xylyl, aralkyl groups,
For example, benzyl and 2-phenylethyl, alkenyl groups,
For example vinyl, allyl and butenyl, monovalent substituted hydrocarbons
Groups such as chloromethyl, hydroxyl, alkoxy
Group such as methoxy, ethoxy, propoxy and t-bu
Toxy, nitro, cyano, and halogen atoms, eg
For example, selected from the group consisting of fluorine, chlorine, bromine and iodine.
It Phosphonium salts and pyridiniums with relatively low activity
When salt is used, R¹Is an electron-withdrawing group or halogen atom
Is preferred. Because it gives a high cure speed
is there. R¹The introduction position of the group is arbitrary. But Ar
When it is a benzene ring, R¹Is preferably 2nd
And / or 4th place. This is because they are easy to synthesize. R ¹
Is a bulky group, this position is
Is preferred. Does steric hindrance reduce activity?
It is.

The R ² and R ³ groups are independently a hydrogen atom or a methyl group, preferably a hydrogen atom. This is because they are easy to synthesize. When the catalytic activity must be increased, R
^At least one of the ² and R ³ groups is a methyl group.

The R ⁴ group is a linear or branched alkyl group,
For example, methyl, ethyl, propyl, butyl, pentyl,
Octyl, decyl, dodecyl and tetradecyl, cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl and naphthyl, alkaryl groups such as tolyl and xylyl, aralkyl groups such as benzyl and 2-phenylethyl, alkenyl groups such as vinyl,
Selected from the group consisting of allyl and butenyl, monovalent substituted hydrocarbon groups such as hydroxyphenyl, methoxyphenyl, ethoxyphenyl, cyanophenyl, chlorophenyl, acetoxyphenyl, propanoylphenyl, methoxycarbonylphenyl and ethoxycarbonylphenyl.

R ⁵ is a substituted or unsubstituted pyridinium group such as pyridinium, 2- or 4-methylpyridinium, 2,4-dimethylpyridinium, 2- or 4-cyanopyridinium, 2- or 4-methoxycarbonylpyridinium and 2- Alternatively, it is 4-ethoxycarbonylpyridinium. R ⁵ preferably has a nucleophilic group such as a cyano group at the 2-position or 4-position.

Component (b) is a sulfonium salt such as methyl
(4-Methoxybenzyl) (1-naphthylmethyl) sulfonium hexafluoroantimonate, methyl (4-hydroxyphenyl) benzylsulfonium hexafluoroantimonate, dimethylbenzylsulfonium hexafluoroantimonate, dimethyl (4-methylbenzyl) sulfonium hexafluoro Antimonate, dimethyl (4-methoxybenzyl) sulfonium hexafluoroantimonate, dimethyl (4-ethoxybenzyl) sulfonium hexafluoroantimonate, dimethyl (4-t-butoxybenzyl) sulfonium hexafluoroantimonate, dimethyl (4-nitrobenzyl ) Sulfonium hexafluoroantimonate, dimethyl (4-cyanobenzyl) sulfonium hexafluoroantimonate, dimethyl (4
-Chlorobenzyl) sulfonium hexafluoroantimonate, methylphenylbenzylsulfonium hexafluoroantimonate, (4-hydroxyphenyl) benzylsulfonium hexafluoroantimonate, dimethyl (1-naphthylmethyl) sulfonium hexafluoroantimonate, methyl (4-hydroxy) ) (1-Naphthylmethyl)
Sulfonium hexafluoroantimonate, dimethyl
(α-methylbenzyl) sulfonium hexafluoroantimonate, ammonium salts such as trimethylbenzylammonium hexafluoroantimonate, dimethylphenylbenzylammonium hexafluoroantimonate, dimethylphenyl (4-nitrobenzyl) ammonium hexafluoroantimonate, (4 -Cyanobenzyl) ammonium hexafluoroantimonate,
(4-chlorobenzyl) ammonium hexafluoroantimonate and the like, phosphonium salts such as triphenylbenzylphosphonium hexafluoroantimonate, triphenyl (4-nitrobenzyl) phosphonium hexafluoroantimonate and the like, and pyridinium salts such as (4
-Methylbenzyl) -4-cyanopyridinium hexafluoroantimonate, (4-t-butylbenzyl) -4-cyanopyridinium hexafluoroantimonate, (4-methoxybenzyl) -4-cyanopyridinium hexafluoroantimonate, (4 -Chlorobenzyl) -4-cyanopyridinium hexafluoroantimonate, (α-methylbenzyl) -4-cyanopyridinium hexafluoroantimonate, benzyl-2-cyanopyridinium hexafluoroantimonate, (α-methylbenzyl) -2- Examples include cyanopyridinium hexafluoroantimonate and 4-methoxycarbonylpyridinium hexafluoroantimonate.

Component (c) is a nitrile rubber containing carboxyl groups, which is a copolymer rubber of acrylonitrile and butadiene that is carboxylated at the molecular chain ends. The carboxyl group of this carboxyl-containing nitrile rubber is 2 to 8 wt%. For example, component (c) of the present invention is a carboxyl terminated butadiene acrylonitrile.

Component (d) of the present invention is an inorganic filler that reduces shrinkage during the curing process, including finely divided silica, spherical silica, fumed silica and precipitated silica, aluminina, titania, zirconia, antimony oxide, water. Powders of aluminum oxide, calcium carbonate, glass beads, boron nitride, aluminum carbide, aluminum nitride, silicon carbide, silicon nitride, silicon nitrocarbide, titanium carbide, titanium nitride and the like are included.

The mixing ratio of the component (c) to the component (a) is 1/5.
It is ~ 10/1. When this ratio is higher than 10/1, the heat resistance of the adhesive composition is lowered, but when this ratio is lower than 1/5, the adhesive strength of the adhesive composition is also lowered. Therefore, the preferred ratio of component (c) to component (a) of the present invention is 1 / 2-2.
It is / 1. Furthermore, the mixing ratio of the component (b) to the component (a) is 0.05 to 10 wt%. The ratio of component (b) to component (a) is
If it is less than 0.05 wt%, the curing speed of the adhesive composition will decrease, but if it is more than 10 wt%, the storage stability of the adhesive composition will decrease and the physical properties after the adhesive composition will be deteriorated. . Therefore, the preferred ratio of component (b) to component (a) is 0.
It is 8 to 3 wt%.

No curing agent is included in the adhesive composition of the present invention, such as novolac type epoxy resins, amines or anhydride compounds. Therefore, disadvantages due to the curing agent, such as non-uniformity, toxicity, and water absorption can be avoided. Further, the present invention may further include a flame retardant, a flame retardant additive, a silane compound or a titanium coupling agent, a pigment, a dye and the like.

The components used in the following examples and comparative examples are shown below.

[Table 1]

First, the components (a), (c) and (d) are mixed and a solvent such as methyl ethyl ketone is added to this mixture.
This mixture is then finely ground with a fine grinder to obtain the compound of formula (I)
To form a solution of. Component (b) is mixed with methyl ethyl ketone and then a solution of formula (II) is formed. The solution of formula (I) and the solution of formula (II) are mixed and milled in a mill, then the formula
Form the adhesive solution of (III).

A viscosity test of this adhesive solution is carried out under the conditions of Brookfield (LVT type). The time at which the viscosity of the adhesive solution increases to twice the initial viscosity at room temperature is called the pot life. Further, the glass transition temperature of this adhesive solution is measured by Du Pont TMA2940.

Example 1 Step 1: Preparation of a solution of formula (I) A-1 50g A-2 50g C 100g D 20g Methyl ethyl ketone (MEK) 210g The above ingredients were mixed and pulverized with a pulverizer for 4 hours. formula
A solution of (I) was obtained.

Step 2: Preparation of solution of formula (II) (accelerator) B-1 2g Methyl ethyl ketone (MEK) 12g

Step 3: The solution of formula (I) and the solution of formula (II) were mixed in a ratio of 1: 1 and pulverized with a pulverizer for 1 hour to obtain 50 wt.
% Adhesive solution was formed.

Example 2 The steps of preparing the adhesive solution are the same as in Example 1, but 2 g of methyl (4-methoxybenzyl) (1-naphthylmethyl) sulfonium hexafluoroantimonate is used as the accelerator for the solution of formula (II). Added to (B-2).

Example 3 The procedure for preparing the adhesive solution is the same as in Example 1, but 2 g of methyl (4-hydroxybenzyl) benzylsulfonium hexafluoroantimonate (B) is added to the solution of formula (II) as a promoter.
-3).

Example 4 The steps for preparing the adhesive solution are the same as in Example 1, but the amount of component A-1 in the solution of formula (I) is 45 g and 5 g of component A-3 is added.

Comparative Example 1 The steps of preparing the adhesive solution were the same as in Example 1, but the accelerator of the solution of formula (II) was 8 g DICY and 1 g 2MI.

COMPARATIVE EXAMPLE 2 The procedure for preparing the adhesive solution is the same as in Example 1, except that 8 g of DICY and 1 g of C ₁₁ Z-2AZ accelerator are added to the solution of formula (II).
INE.

Comparative Example 3 The procedure for preparing the adhesive solution is the same as in Example 1, but the accelerator of the solution of formula (II) is 8 g DICY and 3 g C ₁₁ Z-2AZ.
INE.

Example 5 The adhesive solution prepared in Example 1 is used as an example. Apply this adhesive solution on a 25 μm polyamide film and
A copper foil having a smooth surface was laminated at 20 ° C. and 20 kg / cm ² for 10 minutes. The adhesive overflow is 50 ~ 75μm,
The thickness of the adhesive after lamination was 30 μm.

Brookfield (LVT) at 25 ° C.
Type) to measure the viscosity. In nitrogen gas, 20 ℃
The glass transition temperature was measured by Du Pont TMA at an increasing rate of / min.

The results are shown below.

[Table 2]

The results in the above table show that the adhesive compositions of the present invention have higher glass transition temperatures and longer shelf life than commercial adhesives.

The method and features of the present invention have been described above.
It should be understood that modifications or variations which do not depart from the spirit of the present invention protect the protection scope of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Chen Ching-Pin             Taiwan, Kaohsiung, Chang-Ustri             To Lane 2, Allie 25 6 (72) Inventor Hunting Ching             Taiwan, Changfu County, Shef               Town, Yuan Le Road, Lane             Foot 41 (72) Inventor Fan Sen-Chen             Taiwan, Shinchu County, Chutun               Town, Ho Chang Street, Leh             N 487, Ally 53 20 (72) Inventor Equa-Hour             Taiwan, Elaine County, Yuan-             Shan Country, Tar Unload             12 (72) Inventor Shaquan Shun             Taiwan, Taichung City, South Day             Strict, Khun-li Street, Nan             Bar 36, 16 floor-9 (72) Inventor Ryuenchi             Taiwan, Kaohsiung, Nanz Distri             Kuto, Hung-I Second Road, Leh             South South 44 F term (reference) 4J036 AA01 DC38 FA03 FB03 FB05                       GA02 GA03 JA06                 4J040 CA071 DF082 EC031 EC051                       EC061 EC071 EC121 EC151                       EC161 GA05 HA136 HA196                       HA306 HA326 HA346 HD40                       KA17 KA36 KA42 LA08 NA20

Claims (17)

[Claims] 1. An (a) epoxy resin, (b) a promoter having one structure represented by the following formula: (In the above formula, E represents sulfur, nitrogen or phosphorus, Ar represents an aromatic ring, R ¹ is the same or different, and a substituted or unsubstituted monovalent hydrocarbon group, a hydroxyl group, an alkoxy group, a nitro group. Represents a group, a cyano group or a halogen atom, and R
² and R ³ each represent a hydrogen atom or a methyl group, R ⁴ is the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group, R ⁵ represents a substituted or unsubstituted pyridinium group, and a represents It represents an integer of 0 to 2, and b represents an integer of 2 to 3) (c) A nitrile rubber having a carboxyl group, and (d) an inorganic filler, and the mass ratio of the accelerator to the epoxy resin is 0.05:
1 to 0.1: 1, the mass ratio of nitrile rubber to epoxy resin is 1: 5 to 10: 1, and the mass ratio of inorganic filler to epoxy resin is 1: 2 to 2: 1. object. 2. The adhesive composition according to claim 1, wherein the nitrile rubber is carboxyl-terminated butadiene acrylonitrile. 3. The adhesive composition according to claim 1, wherein the inorganic filler is aluminum hydroxide. 4. The adhesive composition of claim 1, applied to a flexible printed circuit board. 5. The adhesive composition according to claim 1, wherein the epoxy resin in the component (a) contains two or more epoxy groups in one monomer. 6. The adhesive composition according to claim 1, wherein b in the component (b) represents 2 when E is sulfur and 3 when E is nitrogen or phosphorus. 7. A flame retardant and a flame retardant additive are further included.
The adhesive composition according to claim 1. 8. (a) Epoxy resin, (b) Accelerator having one structure of the following formula: (In the above formula, E represents sulfur, nitrogen or phosphorus, Ar represents an aromatic ring, R ¹ is the same or different, and a substituted or unsubstituted monovalent hydrocarbon group, a hydroxyl group, an alkoxy group, a nitro group. Represents a group, a cyano group or a halogen atom, and R
² and R ³ each represent a hydrogen atom or a methyl group, R ⁴ is the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group, R ⁵ represents a substituted or unsubstituted pyridinium group, and a represents It represents an integer of 0 to 2, and b represents an integer of 2 to 3) (c) A nitrile rubber having a carboxyl group, and (d) an inorganic filler, and the mass ratio of the accelerator to the epoxy resin is 0.008:
1 to 0.03: 1, the mass ratio of the nitrile rubber to the epoxy resin is 1/2 to 2/1, and the mass ratio of the inorganic filler to the epoxy resin is 1: 2 to 2: 1. object. 9. The adhesive composition of claim 8, wherein the nitrile rubber is carboxyl terminated butadiene acrylonitrile. 10. The adhesive composition according to claim 8, wherein the epoxy resin in the component (a) contains two or more epoxy groups in one monomer. 11. The adhesive composition according to claim 8, wherein b in the component (b) represents 2 when E is sulfur and 3 when E is nitrogen or phosphorus. 12. The adhesive composition of claim 8, further comprising a flame retardant and a flame retardant additive. 13. (a) Epoxy resin, (b) Accelerator having one structure of the following formula: (In the above formula, E represents sulfur, nitrogen or phosphorus, Ar represents an aromatic ring, R ¹ is the same or different, and a substituted or unsubstituted monovalent hydrocarbon group, a hydroxyl group, an alkoxy group, a nitro group. Represents a group, a cyano group or a halogen atom, and R
² and R ³ each represent a hydrogen atom or a methyl group, R ⁴ is the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group, R ⁵ represents a substituted or unsubstituted pyridinium group, and a represents It represents an integer of 0 to 2, and b represents an integer of 2 to 3) (c) A nitrile rubber having a carboxyl group, and (d) an inorganic filler, and the mass ratio of the accelerator to the epoxy resin is 0.008:
1 to 0.03: 1, the mass ratio of nitrile rubber to epoxy resin is 1: 5 to 10: 1, and the mass ratio of inorganic filler to epoxy resin is 1: 2 to 2: 1. object. 14. The adhesive composition of claim 13, wherein the nitrile rubber is carboxyl terminated butadiene acrylonitrile. 15. The epoxy resin in component (a) contains two or more epoxy groups in one monomer.
The adhesive composition described. 16. The adhesive composition according to claim 13, wherein b in the component (b) represents 2 when E is sulfur and 3 when E is nitrogen or phosphorus. 17. The adhesive composition of claim 13, further comprising a flame retardant and a flame retardant additive.