JP2006307232A - Siloxane polyimide and heat-resistant adhesive containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a siloxane polyimide soluble in an ordinary organic solvent, and showing distinguished heat-resistant adhesiveness when used as a main component of an adhesive for bonding a base material and a copper foil of a flexible printed substrate. <P>SOLUTION: The solvent-soluble siloxane polyimide comprises a copolymer obtained by the reaction of a diaminopolysiloxane (95-5 mol%) -1,3-bis(aminomethyl)cyclohexane (5-95 mol%) mixture and an aromatic tetracarboxylic acid dianhydride. The resulting siloxane polyimide forms a heat-resistant adhesive by the addition of an epoxy resin, a diamine-based curing agent and an organic solvent thereto. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a siloxane polyimide and a heat resistant adhesive containing the same. More particularly, the present invention relates to a solvent-soluble siloxane polyimide and a heat-resistant adhesive containing the same.

  Conventionally, a heat-resistant adhesive mainly composed of aromatic polyimide or the like has been used for bonding between a base material and a copper foil in a flexible printed circuit board. However, since aromatic polyimide is generally not soluble in general-purpose organic solvents, it is used as a solution of its precursor aromatic polyamic acid. Specifically, following application and drying of the solution, high temperature is used. In this case, an imidization process step of heating for a long time is required. At this time, there are problems such as generation of a void phenomenon and thermal deterioration of the electronic component itself.

On the other hand, the following patent documents 1 and 2 disclose solvent-soluble siloxane polyimides, but these prior arts have a problem that heat resistance is low, and solubility in various organic solvents is not necessarily sufficient. There are problems, such as a problem that the substrate curls greatly when applied to a flexible printed circuit board and dried.
JP 61-118424 A Japanese Patent Laid-Open No. 1-121325

  An object of the present invention is a siloxane polyimide that is soluble in a general-purpose organic solvent, and has excellent heat resistance when used as a main component of an adhesive for bonding between a base material and a copper foil of a flexible printed circuit board. Is to provide.

  The object of the present invention is to provide a copolymer of a mixture of diaminopolysiloxane (95-5 mol%)-1,3-bis (aminomethyl) cyclohexane (5-95 mol%) and an aromatic tetracarboxylic dianhydride. This is achieved by a solvent-soluble siloxane polyimide.

  The adhesive comprising the novel siloxane polyimide provided by the present invention as an effective adhesive component is a mild adhesive coating in which aromatic polyimide, which is insoluble even in aprotic polar solvents, is soluble in general-purpose low-boiling organic solvents. It does not require high-temperature and long-time pressure bonding as in the case of conventional aromatic polyimide adhesives, and allows not only low-temperature and short-time bonding, but also heat resistance. But it shows an excellent effect. Furthermore, the flexible printed circuit board in which the base material and the copper foil are effectively bonded using this heat-resistant adhesive does not show a phenomenon that the board is largely curled.

R：炭素数2〜6、好ましくは3〜5の2価の炭化水素基
R₁〜R₄：炭素数1〜5の低級アルキル基、フェニル基
n：2〜30の整数、好ましくは4〜12の整数 As the diaminopolysiloxane that is one component of the diamine compound that reacts with the aromatic tetracarboxylic dianhydride, a compound represented by the following general formula is used.

R: a divalent hydrocarbon group having 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms
R _{1 to} R ₄ : lower alkyl group having 1 to 5 carbon atoms, phenyl group
n: an integer from 2 to 30, preferably an integer from 4 to 12

Examples of this compound include compounds in which R and R _{1 to} R ₄ are combinations of the following substituents.
R R ₁ R ₂ R ₃ R ₄
(CH ₂ ) ₃ CH ₃ CH ₃ CH ₃ CH ₃
(CH ₂ ) ₄ CH ₃ CH ₃ CH ₃ CH ₃
(CH ₂ ) ₃ CH ₃ C ₆ H ₅ CH ₃ C ₆ H ₅
pC ₆ H ₄ CH ₃ CH ₃ CH ₃ CH ₃

  Actually, commercially available products such as Toshiba silicone products TSL9386, TSL9346, TSL9306, Toray Dow Corning product BY16-853U, Shin-Etsu Chemical X-22-161AS, Nihon Unicar product F2-053-01, etc. can be used.

  These diaminopolysiloxanes and 1,3-bis (aminomethyl) cyclohexane are about 95 to 5 mol%, preferably about 80 to 40 mol% in the former, and about 5 to 95 mol% in the latter, Preferably, it is used at a ratio of about 20 to 60 mol%. If the ratio of the latter is less than this, the heat resistant adhesive effect intended by the present invention cannot be obtained, while if it is used in a ratio higher than this, the adhesive composition lacks flexibility.

  Aromatic tetracarboxylic dianhydrides that react with these diamine compound mixtures include 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetra Carboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-biphthalic dianhydride, 2,2'-diphthalic dianhydride propane, diphthalic dianhydride methane, pyromellitic acid The dianhydride, 2,2 ′-(hexafluoroisopropylidene) diphthalic dianhydride, and the like are used in an equimolar ratio with respect to the diamine compound mixture.

  The reaction between the diamine compound mixture and the aromatic tetracarboxylic dianhydride is preferably carried out in an aprotic polar solvent such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone. It is also carried out in a polar solvent. In practice, the diamine compound mixture is dropped into a polar solvent solution of aromatic tetracarboxylic dianhydride at about 0 to 10 ° C.

  Since this reaction product is a polyamic acid which is a polyimide precursor, a dehydration reaction is performed to convert it into a polyimide. The dehydration reaction is preferably performed by using a dehydrating agent such as acetic anhydride at about 100 to 200 ° C.

および

Ar：芳香族テトラカルボン酸残基 Siloxane polyimide, which is a product of the polyimidation reaction, is also considered to be a block copolymer having repeating units (a) and (b) represented by the following general formula, and its weight average molecular weight Mw (measured by GPC) ; In terms of polystyrene) is about 10,000 to 100,000, preferably about 25,000 to 75,000.

and

Ar: Aromatic tetracarboxylic acid residue

  The resulting siloxane polyimide forms a heat resistant adhesive by adding an epoxy resin, a diamine-based curing agent and an organic solvent thereto.

  As the epoxy resin, any one of bisphenol A type, biphenyl type, glycidylamine type, novolac type, etc. is used. Used. These epoxy resins are used in a proportion of about 0.1 to 30 parts by weight, preferably about 0.1 to 10 parts by weight, based on 100 parts by weight of the siloxane polyimide. When the proportion of the epoxy resin used is less than this, the adhesiveness is lowered, whereas when it is used in a proportion larger than this, the heat resistance is lowered.

  The diamine curing agent is used as a curing agent for an epoxy resin, such as 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, m-phenylenediamine, m-xylylenediamine, isophoronediamine, Diethylenetriamine, triethylenetetramine, etc. are used in a proportion of about 0.1-30 parts by weight, preferably about 0.1-10 parts by weight, per 100 parts by weight of the siloxane polyimide.

  Each of the above components is dissolved in a general low-boiling organic solvent such as methyl ethyl ketone, chloroform, tetrahydrofuran, and toluene at a solid concentration of about 10 to 50% by weight, preferably about 20 to 40% by weight. A product solution is formed.

  This adhesive composition solution is effectively used for adhesion between the base material of the flexible printed circuit board and the copper foil. In use, this solution is applied to a flexible base material such as a polyimide film, and a copper foil constituting the printed wiring is bonded thereto and heated at about 185 ° C. for about 100 seconds, for example, to achieve effective adhesion. Is called.

  Next, the present invention will be described with reference to examples.

Examples 1-4
A 100 ml separable flask was charged with 1.61 g (5 mmol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 15 ml of N-methylpyrrolidone under a nitrogen atmosphere, and the solution was cooled with ice. To do. In each of them, a predetermined amount of diaminopolysiloxane [Toshiba silicone product TSL9386; in the above general formula, R is (CH ₂ ) ₃ groups, R _{1 to} R ₄ are all CH ₃ groups] and 1,3-bis (aminomethyl) ) Cyclohexane was added while maintaining a temperature of about 0 to 10 ° C., and then stirred and dissolved at room temperature for 30 minutes. Thereafter, the temperature was raised to 50 ° C. and further stirred for 3 hours, and then heated to 200 ° C. and stirred for 3 hours for dehydration reaction. After completion of the reaction, siloxane polyimide was obtained by reprecipitation in water.

To 100 parts by weight of the resulting siloxane polyimide, 1 part by weight of an epoxy resin (Epicoat 604) and 1 part by weight of 4,4′-diaminodiphenylsulfone are added to form an adhesive as a methyl ethyl ketone solution having a solid content concentration of 40% by weight. Prepared. This adhesive solution was applied to a polyimide film, dried at 140 ° C for 5 minutes, preheated at 37 kg / cm ² G, 185 ° C for 30 seconds, then pressed for 70 seconds to bond with copper foil, Further, it was cured at 180 ° C. for 12 hours, and a 90 ° peel strength at 150 ° C. was measured.

Examples 5-8
In Example 1, diaminopolysiloxane was changed to Toray Dow Corning product BY16-853U.

Examples 9-12
In Example 1, diaminopolysiloxane was changed to Shin-Etsu Chemical product X-22-161AS.

Examples 13-16
In Example 1, 5 parts by weight of Epicoat 154 was used as the epoxy resin, and the amount of 4,4′-diaminodiphenyl sulfone was changed to 5 parts by weight.

Examples 17-20
In Examples 5 to 8, 5 parts by weight of Epicoat 154 was used as the epoxy resin, and the amount of 4,4′-diaminodiphenyl sulfone was changed to 5 parts by weight.

Examples 21-24
In Examples 9 to 12, 5 parts by weight of Epicoat 154 was used as the epoxy resin, and the amount of 4,4′-diaminodiphenyl sulfone was changed to 5 parts by weight.

Comparative Example In the production of the siloxane polyimide of Example 1, the same amount of 1,3-bis (4-aminophenoxy) benzene was used instead of 1,3-bis (aminomethyl) cyclohexane. The obtained siloxane polyimide was insoluble in general-purpose low-boiling solvents such as methyl ethyl ketone.

  The measurement results are shown in the following Table 1, together with the amounts of diaminopolysiloxane and 1,3-bis (aminomethyl) cyclohexane [BAMC] used, the weight average molecular weight Mw of the resulting siloxane polyimide, and the 90 ° peel strength at room temperature. . In either case, the curl phenomenon was not observed.

Table 1
Diaminopoly BAMC Weight average 90 ° pi at room temperature 90 ° pi at 150 ° C
Example Siloxane (g) (g) Molecular Weight Mw Strength (kg / cm) Strength (kg / cm)
1 0.802 0.568 44000 0.83 0.64
2 1.203 0.497 69000 0.95 0.55
3 1.604 0.426 60000 1.08 0.61
4 2.005 0.355 31000 1.05 0.83
5 0.88 0.568 29000 1.03 0.53
6 1.32 0.497 25000 0.91 0.74
7 1.76 0.426 29000 1.00 0.93
8 2.20 0.355 21000 1.16 1.16
9 0.90 0.568 41000 1.16 0.55
10 1.35 0.497 50000 1.00 0.59
11 1.80 0.426 36000 1.04 0.71
12 2.25 0.355 29000 1.19 0.85

13 0.802 0.568 44000 0.94 0.63
14 1.203 0.497 69000 1.03 0.63
15 1.604 0.426 60000 1.19 0.66
16 2.005 0.355 31000 1.18 0.75

17 0.88 0.568 29000 1.03 0.66
18 1.32 0.497 25000 0.91 0.71
19 1.76 0.426 29000 0.99 0.66
20 2.20 0.355 21000 1.23 0.70

21 0.90 0.568 41000 1.13 0.51
22 1.35 0.497 50000 1.03 0.58
23 1.80 0.426 36000 1.03 0.75
24 2.25 0.355 29000 1.25 0.80

The siloxane polyimide obtained in the comparative example was dissolved in dimethylformamide, and adhesive coating was performed with the same composition as in Example 1. The 90 ° peel strength at room temperature and the 90 ° peel strength at 150 ° C. were as follows: Both were only 0.2 kg / cm.

Claims (3)

  A solvent-soluble siloxane polyimide comprising a copolymer of a diaminopolysiloxane (95-5 mol%)-1,3-bis (aminomethyl) cyclohexane (5-95 mol%) and an aromatic tetracarboxylic dianhydride.   A heat-resistant adhesive comprising 100 parts by weight of the siloxane polyimide according to claim 1, 0.1 to 30 parts by weight of an epoxy resin, 0.1 to 30 parts by weight of a diamine-based curing agent, and an organic solvent. The heat-resistant adhesive according to claim 2, which is used for adhesion between a base material of a flexible printed board and a copper foil.