JP4169978B2 - Low dielectric adhesive and film-like joining member comprising the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive and a film-like bonding member having a low dielectric constant and excellent workability and heat resistance. The adhesive and the film-like joining member of the present invention are useful in materials that require low dielectric properties, workability, and heat resistance, such as flexible printed circuit boards, composite lead frames, and laminated materials.
[0002]
[Prior art]
In recent years, electronic devices have been improved in function, performance, and size, and accordingly, electronic components used are required to be reduced in size and weight. Therefore, miniaturization and high density of patterns are achieved in electronic components and mounting boards, and high-density mounting methods such as COL and LOC packages, MCM (Multi Chip Module), and multilayer FPC are used. In these fine wiring boards, a circuit laminate material having a low dielectric constant and a low dielectric loss tangent is required in order to maintain the electrical reliability of the wiring and increase the signal transmission speed of the circuit.
As a conventional flexible circuit board, a polymer film having excellent insulating properties, for example, a film in which a conductor layer such as a copper foil is laminated on one or both sides of a polyimide film via an adhesive is generally formed. It is. However, since the adhesive generally used here is an epoxy resin-based material having a relatively large dielectric constant, even if a polyimide film having a low dielectric constant is used as the substrate, the adhesive layer has a high dielectric constant. There was a problem that the dielectric constant as a whole increased.
[0003]
Examples of the adhesive material having excellent dielectric properties include polyimide-based adhesive materials. However, a polyimide-based adhesive material requires a high temperature of about 300 ° C. and a high pressure for bonding, and is greatly inferior to a general-purpose thermosetting resin in terms of workability. There is also a method of improving processability by blending thermoplastic polyimide and epoxy resin (for example, JP-A-2000-109645), but as described above, epoxy resin has a relatively high dielectric constant. Increasing the ratio to some extent results in an increase in the dielectric constant of the adhesive material itself. Therefore, the technique described in the above publication is insufficient for use in reducing the dielectric constant of the adhesive layer. Further, in the future, it is expected that the miniaturization of wiring and the increase in signal speed will be further advanced, and it is considered that a material having a dielectric constant lower than that of polyimide will be required.
[0004]
An example of a material having a dielectric constant lower than that of the polyimide material is benzocyclobutene (BCB). BCB not only has a lower dielectric constant than polyimide (polyimide: ε = approximately 3.3, BCB: ε = approximately 2.7), but also has low hygroscopicity and excellent heat resistance. It is attracting attention as an insulating layer material that can be used. By using this BCB for the adhesive layer, it is possible to improve the dielectric characteristics as compared with conventional epoxy resin-based and polyimide-based adhesive materials. However, since BCB is inferior in flexibility after curing as compared with a polyimide-based material, it may cause a problem depending on the application when it is used as a film-like joining member with a single component.
[0005]
[Problems to be solved by the invention]
Therefore, the present inventors have solved the above-mentioned problems, and have conducted intensive research aimed at providing a film-like joining member and laminated member having excellent dielectric properties, excellent workability, heat resistance, and flexibility. The present invention has been completed.
[0006]
[Means for Solving the Problems]
The gist of the present invention is that an adhesive in which thermoplastic polyimide and BCB are dissolved in an organic solvent, and the adhesive are applied and dried on a polymer film as a support, such as a polyethylene terephthalate (PET) film. It is related with the film-like joining member obtained by making it peel after peeling.
[0007]
Polyimide generally has extremely low solubility in organic solvents, and thermosetting such as BCB. sex Although it is difficult to mix with a resin, thermoplastic polyimide composed of ester dianhydride and diamine is superior in solubility to conventional polyimide. In particular, the general formula ( 1 )
[Chemical 3]
An acid dianhydride represented by the general formula ( 2 )
[Formula 4]
The thermoplastic polyimide which consists of diamine represented by these shows favorable solubility. Thereby, mixing with a thermosetting resin is attained and it becomes possible to obtain the adhesive member which has both physical properties. In addition, the range of solvents that can be selected is widened, and the processability is excellent.
[0008]
Since BCB is added as a thermosetting component to the adhesive of the present invention, it is a film-like joint obtained as compared with conventional epoxy resin adhesives, polyimide adhesives, and polyimide / epoxy resin mixed adhesives. The dielectric constant and dielectric loss tangent of the member can be lowered. In addition, the disadvantage of poor flexibility can be overcome by mixing with solvent-soluble thermoplastic polyimide, and it is a film-like bonding agent that combines heat resistance of BCB, dielectric properties and heat resistance of thermoplastic polyimide, and flexibility. Can be obtained.
[0009]
From the above points, the adhesive of the present invention and the film-like joining member obtained using the same are excellent in processability, heat resistance, flexibility and dielectric properties.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic polyimide used in the adhesive of the present invention has the general formula (1) (wherein X is — (CH ₂ ) _k -Or a divalent organic group containing an aromatic ring. k is an integer from 1 to 10. The ester dianhydride represented by this is included as a structural component. Preferred examples of the ester dianhydride used in the present invention include 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ′, 4,4′-tetracarboxylic dianhydride, p- Phenylenebis (trimellitic acid monoester anhydride), 3,3 ′, 4,4′-ethylene glycol benzoate tetracarboxylic dianhydride, 4,4′-biphenylenebis (trimellitic acid monoester anhydride), 1 , 4-Naphthalenebis (trimellitic acid monoester anhydride), 1,2-ethylenebis (trimellitic acid monoester anhydride), 1,3-trimethylenebis (trimellitic acid monoester anhydride), 1, 4-tetramethylenebis (trimellitic acid monoester anhydride), 1,5-pentamethylenebis (trimellitic acid monoester anhydride), 1 6- hexamethylene bis (trimellitic acid monoester anhydride), and the like.
[0011]
Preferable examples of the diamine represented by the general formula (2) include those in which Y is —C (═O) —, —SO 2 —, —O—, —S—, — (CH ₂ ) _m -, -NHCO-, -C (CH _Three ) ₂ -, -C (CF _Three ) ₂ Examples of the compound include-, -C (= O) O-, or a bond, and m and n are integers of 1 or more and 10 or less.
[0012]
Moreover, in General formula (2), several Y may be the same or 2 or more types of substituents. In addition, the hydrogen of each benzene ring can be appropriately substituted with various substituents within the range conceivable by those skilled in the art. For example, hydrocarbon groups such as a methyl group and an ethyl group and halogen groups such as Br and Cl can be given, but the substituent is not limited thereto.
[0013]
Further, as a compound having a structure similar to that of the diamine represented by the general formula (2), there may be one in which an amino group is bonded to an ortho position or a para position other than the meta position. It is preferable that it is attached to the meta position as represented by Due to the presence of the amino group at the meta position, the solubility of the produced polyimide in an organic solvent becomes better, and an adhesive excellent in processability can be obtained.
The diamine represented by the general formula (2) can be used alone or in combination.
[0014]
The polyimide resin contained in the adhesive according to the present invention is obtained by dehydrating and ring-closing the polyamic acid polymer that is a precursor thereof. The polyamic acid solution comprises an ester dianhydride represented by the general formula (1) and other acid dianhydrides, and one or more diamines represented by the general formula (2) and other diamines. The ester dianhydride and the total diamine are used so as to be substantially equimolar and polymerized in an organic polar solvent.
[0015]
The polyamic acid or polyimide is prepared by first, in an inert atmosphere such as argon or nitrogen, the ester dianhydride represented by the general formula (1) and other acid dianhydrides, and the general formula (2). It is obtained from a polyamic acid polymer obtained by dissolving or diffusing one or more diamines represented by the formula (II) and other diamines in an organic polar solvent.
[0016]
The order of addition of each monomer is not particularly limited, and acid dianhydride is added in advance to an organic polar solvent, and a diamine component is added to form a polyamic acid polymer solution. An appropriate amount is added first, then acid dianhydride is added, and finally the remaining diamine component is added to form a polyamic acid polymer solution. There are various other addition methods known to those skilled in the art.
[0017]
Examples of the organic polar solvent used for the reaction for forming the polyamic acid solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N. -Acetamide solvents such as dimethylacetamide, N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone, phenol, o-, m- or p-cresol, xinol, halogenated phenol, catechol, etc. Phenol solvents, hexamethylphosphoramide, γ-butyrolactone and the like can be mentioned. Further, if necessary, these organic polar solvents can be used in combination with an aromatic hydrocarbon such as xylene or toluene.
[0018]
The polyamic acid polymer obtained above is dehydrated and closed by a thermal or chemical method to obtain a polyimide resin. As the imidization method, any one of a thermal method in which a polyamic acid solution is heat-treated and dehydrated, and a chemical method in which a dehydrating agent is used for dehydration are used.
Examples of the dehydrating agent by the chemical method include aliphatic acid anhydrides such as acetic anhydride, and aromatic acid anhydrides. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine and isoquinoline.
The thermoplastic polyimide obtained as described above can be used as a solution as it is. Alternatively, the solvent used in the polymerization of the polyamic acid dissolves well, but the polyimide solution is poured into a poor solvent in which the polyimide is difficult to dissolve, and the polyimide resin is precipitated and the unreacted monomer is removed and purified, dried and solid The polyimide resin can be used as appropriate for the adhesive of the present invention.
[0019]
Examples of the poor solvent include, but are not limited to, acetone, methanol, ethanol, isopropanol, benzene, methyl cellosolve, methyl ethyl ketone, and the like.
[0020]
As a thermal method, for example, after polyamic acid is polymerized, it is put into a vacuum oven, heated under reduced pressure, imidized and solvent removed, and taken out as a solid polyimide resin.
[0021]
Since the adhesive according to the present invention contains BCB in its components, it has an excellent low dielectric property compared to conventional epoxy resin adhesives, polyimide adhesives, and polyimide / epoxy resin mixed adhesives. It is possible to obtain the applied film-like joining member. BCB can be purchased from Dow Chemical Company.
[0022]
The mixing ratio of thermoplastic polyimide and BCB is used within a range of 95: 5 to 50:50 by weight. When the amount is too small, low dielectric properties after curing of the obtained film-like joining member are not sufficiently exhibited. That is, the dielectric constant is less than 3.0 and the dielectric loss tangent is not less than 0.01. If the amount is too large, the resulting film-like joining member is inferior in flexibility.
[0023]
The adhesive of the present invention is obtained by dissolving the thermoplastic polyimide resin and BCB in an organic solvent. Examples of the organic solvent include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, N, N-dimethylacetamide, and N, N-diethylacetamide. And acetamide solvents such as The kind of solvent to be combined, the number, and the order of mixing are not particularly limited. Moreover, when it is desired to set the drying temperature after coating low due to problems in the process, it is also possible to use a low boiling ether solvent. Examples of ether solvents include tetrahydrofuran (THF), 1,4-dioxane, dioxolane and the like. When these ether solvents are used, in order to lower the drying temperature, it is assumed that the ether solvent is contained at least 30% by weight or more based on the total amount of the solvent. An adhesive is obtained by dissolving the thermoplastic polyimide resin and BCB in these solvents. At this time, after dissolving the thermoplastic polyimide in the solvent, BCB may be added and used as an adhesive, or each component may be dissolved in the solvent and then the solutions may be mixed and used. . If it is difficult to dissolve the thermoplastic polyimide resin, heating is performed as necessary. However, when an ether solvent is used, the boiling point is low and it is likely to volatilize.
[0024]
The film-like joining member of the present invention is obtained by applying and drying the above adhesive on a polymer film serving as a support, such as a polyethylene terephthalate (PET) film, and then peeling it off. The thickness of the adhesive layer is preferably about 10 to 50 μm. The film-like joining member according to the present invention obtained as described above has characteristics that can be suitably used for flexible printed circuit boards, composite lead frames, laminated materials and the like. Specifically, it exhibits low dielectric properties and excellent heat resistance. Further, it can be bonded at a temperature of about 250 ° C. or less, and is excellent in workability.
[0025]
The film-like laminated member of the present invention can be obtained by heating and pressing a metal foil, another film, a printed circuit board, or the like to the film-like joining member. Examples of the metal foil include copper foil, aluminum foil, 42 alloy and the like. The kind of film is not specifically limited, For example, a polyimide film, a polyester film, etc. are mentioned. Conventional polyimide adhesives require high temperature and pressure in order to develop adhesion to metals such as copper foil and resin films such as polyimide. Moreover, improvement of workability by mixing with an epoxy resin has been difficult due to its poor solubility. Even in an adhesive that can be mixed with an epoxy resin by using a soluble polyimide resin, the dielectric constant is increased, and the advantages of the polyimide-based adhesive are impaired. The film-like joining member according to the present invention can be bonded to a metal foil such as a copper foil or a polyimide film at a relatively low temperature, and is excellent in workability when used. The bonding conditions in this case may be the bonding conditions that are necessary and sufficient for adhesive curing. Specifically, the heating temperature is 150 to 250 ° C., the pressure is 0.1 to 10 MPa, and the heating time is about 5 to 20 minutes. It is preferable to heat and press under these conditions. Moreover, in order to fully advance the hardening reaction of a BCB component, it is preferable to perform heat processing on the conditions of heating temperature 150-250 degreeC and heating time about 1-3 hours after adhesion | attachment.
[0026]
【Example】
(Example 1) 263 g of dimethylformamide (hereinafter referred to as DMF) and 0.112 mol of 3,3′-bis (aminophenoxyphenyl) sulfone (hereinafter referred to as BAPS-M) were added to a glass flask having a capacity of 1000 ml and a nitrogen atmosphere. While stirring under, 0.112 mol of 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ′, 4,4′-tetracarboxylic dianhydride (hereinafter referred to as ESDA) was gradually added. did. The mixture was stirred for 30 minutes in an ice bath, and when the viscosity reached 1500 poise, the stirring was stopped to obtain a polyamic acid solution.
[0027]
300 g of this polyamic acid solution was transferred to a Teflon (R) -coated vat and heated under reduced pressure in a vacuum oven at 200 ° C. for 3 hours at a pressure of 5 mmHg (about 0.007 atm). Taking out from the vacuum oven, 84 g of thermoplastic polyimide was obtained. 30 g of this polyimide powder was added to 70 g of DMF and stirred and dissolved to obtain a polyimide solution (SC = 30%).
[0028]
70 g of the polyimide solution obtained above and 14 g of BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) were mixed and stirred to obtain an adhesive (SC = 36%). The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0029]
(Example 2) 263 g of DMF and 0.112 mol of 1,3-bis (3-aminophenoxy) benzene (hereinafter referred to as APB) were added to a glass flask having a capacity of 1000 ml, and ESDA was stirred while stirring in a nitrogen atmosphere. 0.112 mol was gradually added. The mixture was stirred for 30 minutes in an ice bath, and when the viscosity reached 1500 poise, the stirring was stopped to obtain a polyamic acid solution.
[0030]
300 g of this polyamic acid solution was transferred to a Teflon (R) -coated vat and heated under reduced pressure in a vacuum oven at 200 ° C. for 3 hours at a pressure of 5 mmHg (about 0.007 atm). Taking out from the vacuum oven, 82 g of thermoplastic polyimide was obtained. 30 g of this polyimide powder was added to 70 g of DMF and stirred and dissolved to obtain a polyimide solution (SC = 30%).
[0031]
70 g of the polyimide solution obtained above and 14 g of BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) were mixed and stirred to obtain an adhesive (SC = 36%). The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0032]
(Example 3) 263 g of DMF and 0.112 mol of BAPS-M were added to a glass flask having a capacity of 1000 ml, and while stirring under a nitrogen atmosphere, 3,3 ′, 4,4′-ethylene glycol benzoate tetracarboxylate Anhydrous anhydride (hereinafter referred to as TMEG) was gradually added in an amount of 0.112 mol. The mixture was stirred for 30 minutes in an ice bath, and when the viscosity reached 1500 poise, the stirring was stopped to obtain a polyamic acid solution.
[0033]
300 g of this polyamic acid solution was transferred to a Teflon (R) -coated vat and heated under reduced pressure in a vacuum oven at 200 ° C. for 3 hours at a pressure of 5 mmHg (about 0.007 atm). Taking out from the vacuum oven, 82 g of thermoplastic polyimide was obtained. 30 g of this polyimide powder was added to 70 g of DMF and stirred and dissolved to obtain a polyimide solution (SC = 30%).
[0034]
70 g of the polyimide solution obtained above and 14 g of BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) were mixed and stirred to obtain an adhesive (SC = 36%). The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0035]
Example 4 To a glass flask having a capacity of 1000 ml, 263 g of DMF and 0.112 mol of APB were added, and 0.112 mol of TMEG was gradually added while stirring in a nitrogen atmosphere. The mixture was stirred for 30 minutes in an ice bath, and when the viscosity reached 1500 poise, the stirring was stopped to obtain a polyamic acid solution.
[0036]
300 g of this polyamic acid solution was transferred to a Teflon (R) -coated vat and heated under reduced pressure in a vacuum oven at 200 ° C. for 3 hours at a pressure of 5 mmHg (about 0.007 atm). Taking out from the vacuum oven, 83 g of thermoplastic polyimide was obtained. 30 g of this polyimide powder was added to 70 g of DMF and stirred and dissolved to obtain a polyimide solution (SC = 30%).
[0037]
70 g of the polyimide solution obtained above and 14 g of BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) were mixed and stirred to obtain an adhesive (SC = 36%). The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0038]
(Example 5) A polyimide powder obtained in the same manner as in Example 1 was added to a mixed solvent of 30 g, 35 g of DMF and 35 g of 1,4-dioxolane, and dissolved by stirring to obtain a polyimide solution (SC = 30). %).
70 g of the polyimide solution obtained above and 14 g of BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) were mixed and stirred to obtain an adhesive (SC = 36%). The obtained solution was cast on a 25 μm thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes, and then at 160 ° C. for 10 minutes to obtain a thickness. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0039]
(Comparative Example 1) 35 g of polyimide powder obtained in the same manner as in Example 1, 15 g of Epicoat 1032H60 (manufactured by Yuka Shell), 4.5 g of 4,4′-diaminodiphenyl sulfone, and 127 g of DMF were added. The mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0040]
(Comparative Example 2) 35 g of polyimide powder obtained in the same manner as in Example 3, 15 g of Epicoat 1032H60 (manufactured by Yuka Shell), 4.5 g of 4,4′-diaminodiphenylsulfone, and 127 g of DMF were added. The mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0041]
(Comparative Example 3) 35 g of polyimide powder obtained in the same manner as in Example 4, 15 g of Epicoat 1032H60 (manufactured by Yuka Shell), 4.5 g of 4,4′-diaminodiphenyl sulfone, and 127 g of DMF were added. The mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0042]
(Comparative Example 4) 35 g of polyimide powder obtained in the same manner as in Example 4, 15 g of Epicoat 1032H60 (manufactured by Yuka Shell), 4.5 g of 4,4′-diaminodiphenyl sulfone, and 127 g of DMF were added. The mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0043]
(Comparative Example 5) The polyimide powder obtained in the same manner as in Example 1 was added to 60 g and 140 g of DMF, and dissolved by stirring to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0044]
Comparative Example 6 The polyimide powder obtained in the same manner as in Example 2 was added to 60 g and 140 g of DMF, and the mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0045]
Comparative Example 7 The polyimide powder obtained in the same manner as in Example 3 was added to 60 g and 140 g of DMF, and the mixture was stirred and dissolved to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0046]
Comparative Example 8 The polyimide powder obtained in the same manner as in Example 4 was added to 60 g and 140 g of DMF, and dissolved by stirring to obtain a varnish (SC = 30%).
The obtained solution was cast on a 25 μm-thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, further dried at 120 ° C. for 10 minutes and 180 ° C. for 10 minutes. A 20 μm single-layer film-like joining member was obtained. This film-like joining member had sufficient flexibility even after heat treatment at 220 ° C. for 3 hours.
[0047]
(Comparative Example 9) BCB (manufactured by Dow Chemical Co., SC 63% mesitylene solution) was cast on a 25 μm thick PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.), dried at 60 ° C. for 10 minutes, and further 120 ° C. For 10 minutes and at 180 ° C. for 10 minutes to obtain a single-layer film-like joining member having a thickness of 20 μm. This film-like joining member was brittle after heat treatment at 220 ° C. for 3 hours and was insufficient in flexibility.
[0048]
(Characteristic evaluation of film-like laminated member)
The film-like joining members obtained in each Example and Comparative Example were subjected to heat treatment at 220 ° C. for 3 hours, and then the dielectric constant was evaluated.
・ Measurement device: KS Systems MOA-2012A type molecular orientation meter
・ Measurement frequency: 12 GHz
・ Measurement angle: 0, 45, 90 degrees
Table 1 shows the evaluation results of the characteristics of the film-like joining members of Examples and Comparative Examples.
[0049]
[Table 1]
[0050]
【The invention's effect】
Since the adhesive of the present invention uses thermoplastic polyimide and BCB, the film-like joining member obtained therefrom is excellent in heat resistance and dielectric properties. Conventional polyimide-based adhesive members require high temperature and high pressure to develop adhesiveness, and thus have poor workability. On the other hand, BCB adhesive members have insufficient flexibility after curing. By combining both components, the adhesive of the present invention can obtain a film-like bonding agent having a lower dielectric property than that of a conventional polyimide system while maintaining flexibility.
[0051]
Moreover, since the thermoplastic polyimide used for the adhesive of the present invention has a glass transition temperature lower than that of the conventional one, it can be bonded at a lower temperature and has excellent workability. By using polyimide and BCB, heat resistance is also excellent. From the above points, the adhesive of the present invention and the film-like joining member using the adhesive exhibit excellent heat resistance, workability, and dielectric properties.

Claims (6)

In an organic solvent, general formula (1)
(Wherein, X represents — (CH ₂ ) _k — or a divalent organic group containing an aromatic ring, k is an integer of 1 or more and 10 or less), General formula ( 2 )
(In the formula, Y represents —C (═O) —, —SO ₂ —, —O—, —S—, — (CH ₂ ) _m —, —NHCO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (═O) O—, or a bond. M and n are integers of 1 or more and 5 or less.) A low dielectric adhesive obtained by dissolving benzocyclobutene (BCB) and having a weight ratio of thermoplastic polyimide to benzocyclobutene of 95: 5 to 50:50. The thermoplastic polyimide is obtained by using 50 mol% or more of each component of the ester dianhydride represented by the general formula (1) and the diamine represented by the general formula (2). The low dielectric adhesive according to claim 1, wherein: The low dielectric adhesive according to claim 1 or 2, wherein at least one of a sulfoxide solvent, a formamide solvent, and an acetamide solvent is used as the organic solvent. The low dielectric adhesive according to claim 1 or 2, comprising at least 30% by weight or more of an ether solvent selected from tetrahydrofuran (THF ), 1,4-dioxane, and dioxolane as the organic solvent. Film-like bonding member obtained by peeling the low dielectric adhesive according to claim 1, in after coating and drying on a polymer film serving as a supporting bearing member. 6. The film-like bonding member according to claim 5, wherein the cured product has dielectric properties of a frequency of 12 GHz, a dielectric constant of less than 3.0, and a dielectric loss tangent of 0.01 or less.