JP2755768B2 - Imide adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bismaleimide-based resin adhesive. More specifically, the present invention relates to a bismaleimide adhesive used as an adhesive for printed circuit boards and the like.

(Prior Art) In recent years, with the development of the electronics industry, simplification, miniaturization, and high reliability of mounting methods for communication and consumer devices have been demanded.
The use of printed circuit boards is desired. Particularly, the use of a flexible printed circuit board which is lightweight and can be mounted three-dimensionally is advantageous and attracts attention.

Conventional flexible printed circuit boards are mainly made of copper foil and plastic film typified by polyimide bonded together with an adhesive such as NBR / phenol resin, phenol resin / butyral resin, or NBR / epoxy resin. However, these adhesives have problems with heat resistance such as solder heat resistance, long-term thermal deterioration, adhesive strength when heated, and the like, and even if heat-resistant polyimide was used as a film, the performance could not be fully utilized. .

(Problems to be Solved by the Invention) As a result of intensive studies to overcome the above-mentioned drawbacks, the present invention uses a bismaleimide / diamine / acrylic resin-based adhesive to provide a flexible adhesive property and flexibility. The inventors have found that the heat resistance can be improved without impairing other characteristics required for the printed circuit board, and have completed the present invention.

(Means for Solving the Problems) An excellent flexible printed circuit board is obtained by using an adhesive composed of the following (a) and (b) for bonding a metal foil such as a copper foil and a plastic film such as a polyimide. Is obtained.

(A) 100 parts by weight of aminobismaleimide obtained by heating and reacting a diamine having a molar ratio of 1: 0.5 to 1.5 with bismaleimide in an organic polar solvent; (b) acrylonitrile 15 to 35% by weight, having 5 or less carbon atoms 10 to 1000 parts by weight of acrylic resin obtained by copolymerization of 55 to 83% by weight of an ester of alcohol and acrylic acid and / or methacrylic acid and 2 to 10% by weight of acrylic acid and / or methacrylic acid In order to obtain good results, it is indispensable to mix the adhesive components in the compositions and ratios as shown in the above (a) and (b).

That is, the present invention provides a compound represented by the general formula (I): (Wherein R represents a divalent group containing at least two carbon atoms) and a general formula (II) H ₂ N—R′—NH ₂ (II) wherein R ′ is (Representing a divalent group containing at least 2 carbon atoms) with a bismaleimide compound in a molar ratio of 1: 0.5 to 1.5 in an organic polar solvent by heating reaction. Amino bismaleimide 10
0 to 10 parts by weight of the acrylic resin specified in (b)
An imide-based adhesive characterized by adding 000 parts by weight.

In the present invention, the bismaleimide represented by the general formula (I) includes, for example, N, N′-m-phenylenebismaleimide, N, N ′-{γ, γ ′-(dipropyl) spiroacetal} bismaleimide, N , N'-p-phenylenebismaleimide, N, N'-oxy (di-p-phenylene) bismaleimide, N, N'-methylene (di-p-phenylene) bismaleimide, N, N'-sulfo (di -P-phenylene) bismaleimide, N, N'-m-phenylenebis (p-oxyphenylene) bismaleimide, N, N'-hexamethylenebismaleimide, N, N'-decamethylenebismaleimide, N, N ' -Oxydipropylene bismaleimide, ethylenedioxybis (n-propylmaleimide), N, N'-methylene (di-1,4-cyclohexylene)
Bismaleimide, N, N'-isopropylidene (di-1,
4-cyclohexylene) bismaleimide, 2,6-xylylenebismaleimide, 2,5-oxadiazolylenebismaleimide, N, N'-p-phenylene (dimethylene) bismaleimide, N, N'-thio (diphenylene) Discitraconimide, N, N'-methylene (di-p-phenylene) bis (chloromaleimide), N, N'-hexamethylenebis (cyanomethylmaleimide) and the like can be mentioned alone or in combination of two or more. They can be mixed and used.

The diamine represented by the general formula (II) is, for example, 4,
4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, m-phenylenediamine, p-phenylenediamine, 2,2'-bis (4 -Aminophenyl) propane, benzidine, 2,2-
Bis {4- (4-aminophenoxy) phenyl} propane, 4,4'-diaminodiphenyl sulfide, bis (4
-Aminophenyl) methylphosphinoxide, bis (4
-Aminophenyl) phenylphosphinoxide, bis (4-aminophenyl) methylamine, 1,5-diaminonaphthalene, 1,1-bis (p-aminophenyl) phthalane, 4,4'-diaminobenzophenone, 4,4 '-Diaminoazobenzene, bis (4-aminophenyl) phenylmethane, 1,3-bis (3-aminophenoxy) benzene,
Examples thereof include 1,1-bis (4-amino-3-methylphenyl) cyclohexane and the like, and these can be used alone or as a mixture of two or more.

The bismaleimide and the diamine are heated and reacted in an organic polar solvent. Examples of such a solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monopropyl ether, and ethylene glycol monoethyl. Ether acetate, N-methyl-2-pyrrolidone and the like can be used, and these can be used alone or as a mixed solvent of two or more kinds. Other acetone, methyl ethyl ketone and the like may be used in combination as long as the aminobismaleimide is dissolved in these ether polar solvents.

The molar ratio of diamine to bismaleimide is 1: 0.5.
The range is preferably from 1.5 to 1.5, and more preferably from 0.98 to 1.05. If the molar ratio of the diamine is less than 0.5, precipitation of the bismaleimide tends to occur in the aminobismaleimide solution, and if it exceeds 1.5 mol, the heat resistance of the cured adhesive is unfavorably affected.

Above, the reaction temperature of bismaleimide and diamine,
The temperature is preferably in the range of 80 to 120 ° C. At 80 ° C or lower, the reaction does not proceed sufficiently, and at 120 ° C or higher, a side reaction occurs and it is difficult to control. The reaction time is preferably in the range of 20 to 300 minutes. If the reaction time is less than 20 minutes, the reaction does not proceed sufficiently.

The acrylic resin is added under a heated atmosphere at 80 to 120 ° C. after the reaction between the bismaleimide and the diamine to obtain the adhesive of the present invention.

The ratio of the acrylic resin to the aminobismaleimide is preferably in the range of 100 to 10 to 1000 parts by weight. If the amount is less than 10 parts by weight, the adhesiveness is not sufficient, and if it is more than 1000 parts by weight, the heat resistance of the adhesive is reduced.

The acrylic resin (b) used in the present invention needs to contain 15 to 35% by weight of acrylonitrile in the components. Fifteen
When the content is less than the weight%, the adhesive strength and the solder heat resistance decrease. As the acrylonitrile component increases, the adhesive strength and solder heat resistance improve, but if it exceeds 35% by weight, the flexibility decreases. 15-35 to achieve sufficient adhesive strength and flexibility
% By weight is desirable. Examples of the ester of an alcohol having 5 or less carbon atoms with acrylic acid or methacrylic acid include 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate. Acrylic acid and / or methacrylic acid should be 2 to 10% by weight. If it is less than 2% by weight,
Adhesive strength and solder heat resistance decrease. If it exceeds 10% by weight, the flexibility decreases.

The above imide-based adhesive may be used as it is, but a flame retardant such as antimony trioxide, aluminum hydroxide, barium borate, brominated epoxy, or silica alumina, mica, titanium oxide, zirconia, magnesium oxide, etc. Of inorganic filler to 100 parts by weight of adhesive
It may be added in a proportion of 0 parts by weight or less. If it exceeds 40 parts by weight, the adhesive strength will decrease.

The adhesive of the present invention can be applied to one or both sides of a metal foil such as a copper foil or an aluminum foil or a heat-resistant plastic film such as a polyimide or a polyester, and bonded to each other to obtain a printed circuit board. Alternatively, a prepreg can be obtained by impregnating a substrate such as a glass cloth.

The drying temperature of the adhesive applied to these substrates is usually 60 to
200 ° C., after removing the solvent, after applying and drying the adhesive, the metal foil and the film are superimposed on each other in a range of 130 to 280 ° C. for 1 to 3 hours, and then heat and pressure cured, or at the above temperature or lower. The printed circuit board can be obtained by heating at 130 to 280 ° C. for 1 to 3 hours after pressing and pressing.

The adhesive of the present invention is composed of a polyimide having no adhesive layer and a metal foil because it has excellent adhesiveness and heat resistance between metal and plastic, in addition to mutual adhesion between metal and plastic such as polyimide. By laminating the polyimide sides of the flexible printed circuit boards of the layers together, a double-sided board can also be obtained. Further, it can be used as a structural adhesive for bonding metal and plastic.

(Example) Example 1 First, 32 parts by weight of acrylonitrile, n-butyl acrylate in a four-neck separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a dry nitrogen gas inlet.
A mixture of 100 parts by weight, 3 parts by weight of acrylic acid, and 400 parts by weight of toluene was reacted while stirring at 60 ° C. for 16 hours in a nitrogen atmosphere to obtain a viscous acrylic resin solution having a resin content of 25% by weight.

Next, a 4-neck separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a dry nitrogen gas inlet was placed in a 4-neck separable flask with 1,3-bis / mole of N, N'-methylene (di-p-phenylene) bismaleimide. (3-aminophenoxy)
One mole of benzene was added to make a total of 100 parts by weight, and 100 parts by weight of ethylene glycol monomethyl ether was further taken. After reacting at 100 ° C. for 3 hours, 400 parts by weight of the acrylic resin obtained earlier (resin content 25% by weight) Was added, and the mixture was stirred at a temperature of 100 ° C. for 1 hour and then cooled to obtain a bismaleimide-based adhesive. The dry nitrogen gas was allowed to flow over the entire process from the preparation of the reaction to the removal of the product.

Example 2 After synthesizing the same acrylic resin as in Example 1, the same apparatus and method were used to prepare 2,2 ′-{γ, γ ′-(dipropyl) spiroacetal} bismaleimide per mole of 2,
0.6 mol of 2-bis {4- (4-aminophenoxy) phenyl} propane is added to make a total of 100 parts by weight, and 100 parts by weight of N-methyl-2-pyrrolidone is taken. After reacting at a temperature of 100 ° C. for 3 hours, Then, 400 parts by weight of the acrylic resin obtained above (resin content: 25% by weight) was added, and the mixture was stirred at a temperature of 100 ° C. for 1 hour and then cooled to obtain a bismaleimide-based adhesive. The dry nitrogen gas was allowed to flow over the entire process from the preparation of the reaction to the removal of the product.

(Comparative Example) Comparative Example 1 In Example 1, 0.3 mol of 1,3-bis (3-aminophenoxy) benzene was added to 1 mol of N, N'-methylene (di-p-phenylene) bismaleimide, and a total of 100 weight was added. And 100 parts by weight of ethylene glycol monomethyl ether, and reacted at a temperature of 100 ° C. for 3 hours. After cooling the solution, bismaleimide was precipitated and a uniform adhesive was not obtained.

Comparative Example 2 The aminobismaleimide obtained in Example 1 was used as an adhesive without adding an acrylic resin.

The above-mentioned bismaleimide-based adhesive solution was cast and applied on a 25 μm polyimide film (Kapton, manufactured by DuPont) so that the thickness after drying was 25 μm, and then dried in a dryer at 150 ° C. for 1 hour. , 35μm thick copper foil is superimposed on the surface coated with adhesive, temperature 250 ℃, pressure 20k
Pressing was performed at g / cm ² for 1 hour to obtain a flexible printed circuit board. Table 1 shows the results of evaluating the obtained circuit boards.

(Effects of the Invention) Conventional adhesives such as NBR / phenolic resin, phenolic resin / butyral resin, and NBR / epoxy resin cannot achieve both heat resistance and adhesiveness. By using this, the heat resistance can be improved without impairing other characteristics required for the flexible printed circuit board such as adhesiveness and flexibility.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-4682 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 133/00-133/22 C09J 179 / 08 H05K 3/38 C08L 33/00-33/22 C08L 79/08

Claims (1)

(57) [Claims] An imide adhesive containing the following (a) and (b): (A) 100 parts by weight of aminobismaleimide obtained by heating and reacting a diamine having a molar ratio of 1: 0.5 to 1.5 with bismaleimide in an ether-based polar solvent; (b) acrylonitrile 15 to 35% by weight, having 5 or less carbon atoms 10 to 1000 parts by weight of an acrylic resin obtained by copolymerizing 55 to 83% by weight of an ester of alcohol and acrylic acid and / or methacrylic acid and 2 to 10% by weight of acrylic acid and / or methacrylic acid