JP2866779B2 - Heat resistant adhesive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant adhesive sheet for flexible wiring boards and ICs, which has extremely high adhesive strength and excellent heat resistance.

[0002]

2. Description of the Related Art Conventionally, 1) the role of a solder resist in a soldered portion, 2) bending resistance in a bent portion, 3) securing of electrical insulation and protection of the surface of a flexible wiring board on which a circuit has already been formed. For the purpose, a method of laminating a coverlay film having an adhesive layer on one side by applying heat and pressure to a flexible wiring board is generally performed. When manufacturing a multilayer flexible wiring board or a rigid-flexible wiring board, a laminated board is manufactured by applying heat and pressure with a bond ply having an adhesive layer on both sides interposed therebetween. In addition, relatively recently, a part of a tape for fixing a lead frame (one-sided adhesive layer) and a part of an adhesive tape for a lead-on-chip (double-sided adhesive layer) have begun to be used in ICs.

[0003]

The adhesive sheet of the present invention is:
Although the above four types are included, the conventional adhesive sheet has an adhesive layer in a semi-cured state (B-stage) of epoxy or acrylic, and is a thermosetting type that adheres to the FPC by applying heat and pressure. Therefore, 1) lack of heat resistance due to the material, 2) deterioration of electric insulation during humidification, 3) short life due to B-stage, 4) curing of the adhesive layer of B-stage at the time of pressing There is a drawback that a long time is required because it is necessary to make it work.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned drawbacks, and as a result, have found that the glass transition temperature is 20%.
The present invention has been completed by paying attention to the fact that the above-mentioned disadvantages can be solved by using an adhesive sheet having a thermoplastic polyimide film having an excellent flowability at a temperature of 0 ° C. or lower and having an excellent flow property at a high temperature. That is, in the present invention, the polymer molecule terminal is represented by the formula (1):

[0005]

Embedded image (Wherein, Z is selected from the group consisting of a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-condensed polycyclic aromatic group in which aromatic groups are connected to each other directly or by a bridge member. (Showing a divalent group) with a dicarboxylic anhydride represented by the formula (2):

[0006]

Embedded image (Wherein, Y is the formula (3) or [Formula 6], and X represents a direct bond, -CO- or -O-)

[0007]

Embedded image Is a heat-resistant adhesive sheet formed by forming a thermoplastic polyimide adhesive layer comprising a polymer having a repeating unit represented by the formula (1) on one or both sides of a polyimide support substrate, and is preferably represented by the formula (1). Dicarboxylic anhydride is
A heat-resistant adhesive sheet, which is phthalic anhydride; and
A heat-resistant adhesive sheet which can be bonded by bonding a polyimide having an glass transition temperature of 200 ° C. or less to an adherend at the time of hot pressing at 230 ° C. as an adhesive layer; In the hot press lamination, the bond strength with the copper foil glossy surface is 0.7kg / c
2. The heat-resistant adhesive sheet according to claim 1, which has an elastic modulus at 230 ° C. of 10 ³ dynes / cm.
² is a heat-resistant adhesive sheet having a polyimide as an adhesive layer having a thickness of ² or less, and the thickness of the polyimide support base material is 5 to 2
A heat-resistant adhesive sheet having a thickness of 1 to 50 microns and a thickness of 00 microns.

Further, the present invention provides a polyimide as a polymer having a polymer molecule terminal capped with a dicarboxylic anhydride.
After taking out as a polyimide powder, a method for producing the heat-resistant adhesive sheet, wherein a polyimide varnish dissolved and contained in a solvent for dissolving the same is cast on a polyimide support substrate and then dried to form an adhesive layer. Preferably, a varnish consisting of a reaction mixture obtained by performing end capping of polyamic acid and subsequent thermal imidization, directly cast and applied to a polyimide support substrate and then dried to form a heat-resistant adhesive sheet that forms an adhesive layer In addition, the reaction mixture in which the imidization is not completed and the polyamic acid remains in the range of 0.1 to 10% is directly cast on a polyimide support substrate and then dried to form an adhesive layer. Manufacturing method of heat-resistant adhesive sheet,
Also, here is a method for producing a heat-resistant double-sided adhesive sheet in which a varnish is cast and applied to both sides of a polyimide support substrate and then dried to form an adhesive layer. A method for producing a heat-resistant double-sided adhesive sheet, in which after casting and initial drying, the same method is applied to the second side for casting and initial drying. In addition, when casting and drying on the second surface side and initial drying, to prevent the adhesive layer on the first surface side from sticking to the rolls in the coater dryer, (1) drying the first surface side at a high temperature After sufficiently reducing the residual solvent over a long period of time, transfer to the casting application and initial drying on the second side,
And drying the second surface side at a relatively low temperature for a short time, or (2) a method for producing a heat-resistant double-sided adhesive sheet in which both surfaces are continuously dried in a non-contact manner after casting and application on the second surface side. And a method for producing a heat-resistant double-sided adhesive sheet by a method of continuously drying both surfaces in a non-contact manner when performing final drying on both surfaces simultaneously with the present dryer.

Hereinafter, the present invention will be described in detail. The polyimide forming the adhesive layer of the heat-resistant adhesive sheet of the present invention basically uses 1,3-bis (3-aminophenoxy) benzene (hereinafter abbreviated as APB) as a diamine,
On the other hand, 3,3 ', 4,4 as tetracarboxylic dianhydride
'-Diphenylethertetracarboxylic dianhydride (hereinafter abbreviated as ODPA), 3,3', 4,4'-benzophenonetetracarboxylic dianhydride (hereinafter BTDA)
And 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as BPDA)
Polyimide obtained by polycondensation with at least one tetracarboxylic dianhydride selected from the group consisting of, and heat-resistant having as a bonding layer a thermoplastic polyimide in which polymer molecular ends are sealed with dicarboxylic anhydride The adhesive sheet solves the above-mentioned problems of the conventional adhesive sheet.

The following are already known as polyimides using APB as a diamine component. For example, (1) polyimide oligomer having a terminal acetylene group produced from APB, BTDA and 3-aminophenylacetylene (N, Bilow et al., US Pat.
45,018 and USP 3,879,349),
(2) Polycondensation type polyimide composed of APB and pyromellitic anhydride (TP Gannett et al., USP 4,48)
5,140), and (3) a heat-resistant polyimide comprising APB and various tetracarboxylic dianhydrides (JP-A-61-143).
477 and JP-A-61-291670).

However, these polyimides (1)
Is an addition-type thermosetting polyimide in which the oligomer terminals are sealed with 3-aminophenylacetylene, but these terminal acetylene groups undergo a crosslinking reaction by heat treatment, and the condensation-type thermoplastic polyimide of the present invention. The heat-resistant polyimide consisting of belongs to a completely different category. Further, (2) is a condensation type polyimide using APB as a raw material monomer, characterized in that pyromellitic dianhydride is used as a tetracarboxylic dianhydride component, and has a completely different structure from the heat-resistant polyimide in the present application. It is different. (3) is APB
And various tetracarboxylic dianhydrides, but a reactive end group at the polymer molecule end remains, and high-temperature, high-pressure bonding conditions are required compared to the heat-resistant polyimide in the present application. Is what is done.

The polyimide according to the present invention contains the above-mentioned aromatic diamine component and aromatic tetracarboxylic dianhydride as main components, but the formula is within a range that does not impair the properties of the heat-resistant adhesive sheet of the present invention. (4), [Chemical formula 7]

[0013]

Embedded image (Wherein, R represents an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group,
A tetravalent group selected from the group consisting of a monocyclic aromatic group, a condensed polycyclic aromatic group, and a non-condensed polycyclic aromatic group in which the aromatic groups are connected to each other directly or by a crosslinking member; There is no problem if the tetracarboxylic dianhydride represented by the formula (1) is contained in the range of 0 to 30% as an alternative to the aromatic tetracarboxylic dianhydride.

That is, examples of tetracarboxylic dianhydrides that can be partially substituted include, for example, ethylene tetracarboxylic dianhydride, cyclopentanecarboxylic dianhydride, pyromellitic dianhydride, 2,2 ′ , 3,3'-benzophenonetetracarboxylic dianhydride, 2,2 ', 3,3'
-Biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride,
2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone Dianhydride, 1,1-bis (2,3
-Dicarboxyphenyl) ethane dianhydride, bis (2,
3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1, 2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,2 7,8-phenanthrenetetracarboxylic dianhydride and the like can be mentioned.

The polyimide according to the present invention has no problem even if it contains another aromatic diamine in the range of 0 to 30% as long as the properties of the heat-resistant adhesive sheet are not impaired.
Examples of diamines that can be partially substituted include, for example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, bis (3-aminophenyl) sulfide, (3- Aminophenyl) (4-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfoxide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) Sulfone, (3-aminophenyl) (4-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3 , 3'-diaminodiphenylmethane, 3,4 '
-Diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, 3,3'-
Diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (3- Aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4 −
(4-aminophenoxy) phenyl] ethane, 2,2-bis [4- (3-aminophenoxy) phenylpropane,
2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3- (3-aminophenoxy) Phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoro Propane, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (3- Aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy)
Biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy)
Phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (aminophenoxy) phenyl] sulfoxide, bis [4-
(3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone,
Bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3- Bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4-bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,
4-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4- (4-amino-
α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4
-{4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4 -Aminophenoxy) -α, α-dimethylbenzyl] benzene and the like.

Further, in the present invention, in order to obtain a polyimide which forms a heat-resistant adhesive sheet capable of bonding at low temperature / low pressure, the following formula (1) , [Chemical Formula 8]

[0017]

Embedded image (Wherein, Z is a monocyclic aromatic group, a condensed polycyclic aromatic group,
A dicarboxylic acid anhydride represented by a divalent group selected from the group consisting of non-fused polycyclic aromatic groups in which aromatic groups are connected to each other directly or by a bridging member) is used.

Examples of the dicarboxylic anhydride used as a terminal blocking agent include phthalic anhydride, 2,3-benzophenone dicarboxylic anhydride, 3,4-benzophenone dicarboxylic anhydride, and 2,3-dicarboxyphenylphenyl. Ether anhydride, 3,4-dicarboxyphenylphenyl ether anhydride, 2,3-biphenyldicarboxylic anhydride, 3,4-biphenyldicarboxylic anhydride, 2,3
-Dicarboxyphenylphenylsulfone anhydride, 3,4
-Dicarboxyphenylphenylsulfone anhydride, 2,3
-Dicarboxyphenylphenyl sulfide anhydride,
1,2-naphthalenedicarboxylic anhydride, 1,8-naphthalenedicarboxylic anhydride, 1,2-anthracenedicarboxylic anhydride, 2,3-anthracenedicarboxylic anhydride, and 1,9-anthracenedicarboxylic anhydride No. These dicarboxylic anhydrides may be substituted with a group having no reactivity with amine or dicarboxylic anhydride.

The production reaction of the polyimide (or polyimide varnish) according to the present invention is usually carried out in an organic solvent. As the organic solvent used in this reaction, for example, N-
Methyl-2-pyrrolidone, N, N-dylmethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide , Pyridine, dimethyl sulfone, hexamethylphosphoramide, tetramethylurea, N-methylcaprolactam, ptyrrolactam, tetrahydrofuran, m-dioxane, p-dioxane, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether,
1,2-bis (2-methoxyethoxy) ethane, bis 2
-(2-methoxyethoxy) ethyl ether, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane,
Examples include pyridine, picoline, dimethyl sulfoxide, dimethyl sulfone, O-cresol, m-cresol, p-cresol, cresylic acid, p-chlorophenol, anisole and the like.

The heat-resistant adhesive sheet of the present invention can be obtained by synthesizing a polyimide varnish by the following method, and then coating and drying one or both sides of the polyimide support substrate. The polyimide varnish for coating is manufactured as follows. (1) After synthesizing the polyamic acid, the terminal of the polymer molecule is sealed with a dicarboxylic anhydride and chemically imidized with an imidizing agent. The obtained reaction mixture is discharged into a poor solvent such as methanol under strong stirring, and the precipitate is dried. Method for dissolving this polyimide in a solvent that dissolves it to obtain a polyimide varnish for coating (2) After synthesizing the polyamic acid, the polymer molecule ends are sealed with dicarboxylic anhydride, and thermal imidization is performed by heating. The obtained reaction mixture is discharged into a poor solvent such as methanol under strong stirring, and the precipitate is dried. Method of dissolving this polyimide in a solvent that dissolves it to obtain a polyimide varnish for coating. (3) After synthesizing the polyamic acid, the polymer molecule ends are sealed with dicarboxylic anhydride, and thermal imidization is performed by heating. Method of Directly Using the Obtained Reaction Mixture as a Polyimide Varnish for Coating Further, the above method (3) can be carried out by the following method. (A) After the synthesis of the polyamic acid, the polymer molecule ends are sealed with a dicarboxylic anhydride, a ring-closing catalyst is charged, thermal imidization is performed, and the water generated by the imidization is converted into N-methyl-2-pyrrolidone by a nitrogen stream. And the reaction solvent. (Ii) After the synthesis of the polyamic acid, the polymer molecule ends are sealed with dicarboxylic anhydride, a ring-closing catalyst and an azeotropic solvent such as xylene are charged, and then heated to heat to perform thermal imidization. The water produced by the imidization is distilled off azeotropically with xylene and the like and by a nitrogen stream. (C) Diamine and tetracarboxylic dianhydride are added at once and stirred for a short time, then dicarboxylic anhydride, ring closing catalyst,
An azeotropic solvent is charged, and heating and heating are started. Thermal imidization is carried out while simultaneously proceeding with synthesis of polyamic acid, sealing of polymer molecule terminals and azeotropic distillation of produced water.

The amount of the aromatic tetracarboxylic dianhydride used is 0.8 to 0.999 mol per mole of APB, and the amount of the aromatic dicarboxylic anhydride used is the mole of APB and tetracarboxylic dianhydride. Assuming that the number difference is a, it is preferable to use a mole number of 2a or more and 8a or less.

When the number of moles of the aromatic tetracarboxylic dianhydride used is less than 0.8 mol per 1 mol of APB, the degree of polymerization of the polymer is not sufficient, heat resistance is impaired, and 0.999 mol If it exceeds, it becomes difficult to seal the terminal of the polymer, and bonding at low temperature / low pressure becomes impossible. If the amount of the aromatic dicarboxylic acid anhydride is less than 2 mol, the terminal end of the polymer cannot be sufficiently sealed, making it difficult to adhere at low temperature / low pressure, and if it exceeds 8 mol, the heat resistance is impaired. .

Particularly preferably, the amount of the aromatic tetracarboxylic dianhydride used is 0.9 to 0.9 mol per mole of APB.
0.997 mol, and the amount of the aromatic dicarboxylic anhydride used is 3a to 6a mol when the difference in the number of moles between the APB and the aromatic tetracarboxylic dianhydride is a.
The concentration during the synthesis of polyamic acid is usually 15 to 35%.
Perform within the range. Particularly preferably, it is 20 to 30%.

In the case of shifting to amidation in a reactor after completing the synthesis of the polyamic acid, the reaction temperature for producing the polyamic acid is usually 60 ° C. or lower, preferably 30 ° C. to 50 ° C. It is below ° C. The reaction pressure is not particularly limited, and the reaction can be carried out at normal pressure. The reaction time varies depending on the type of tetracarboxylic dianhydride to be used, the type of solvent, the reaction temperature and the like, and the reaction is usually carried out for a time sufficient to complete the formation of the polyamic acid. Usually, the reaction is carried out for 2 to 24 hours. The logarithmic viscosity (measured by N-methyl-2
-0.5% concentration in pyrrolidone, 35 ° C) 0.3 to
1.5 dl / g of polyamic acid is obtained.

When the obtained polyamic acid is chemically imidized, an acid anhydride such as acetic anhydride, propionic anhydride or benzoic anhydride is used as a chemical imidizing agent. In the imidation reaction in this case, if necessary, pyridine,
There is no problem even if tertiary amines such as γ-picoline, imidazole and triethylamine are added as a base catalyst. The reaction temperature when chemically imidizing is usually from room temperature to 2
The temperature is not higher than 00 ° C., preferably not higher than room temperature and not higher than 100 ° C., and a reaction time of 0.5 to 24 hours is sufficient.

On the other hand, when the obtained polyamic acid is subjected to thermal imidization, a tertiary amine such as pyridine, γ-picoline, imidazole, triethylamine or the like is usually added as an essential component as a ring closing catalyst. The water produced by this thermal imidization is removed from the system by azeotropic removal by adding an azeotropic solvent such as toluene or xylene to the reaction system, or
It does not matter which of the two methods is employed to remove the reaction solvent such as methyl-2-pyrrolidone out of the system together with a nitrogen gas stream.
The reaction temperature in this case can be from 80 ° C. to the reflux temperature of the solvent used at that time, but is preferably from 100 ° C. to 200 ° C. Particularly preferred reaction temperatures are from 150 ° C to 195 ° C. The reaction time may be in the range of 1 hour to 24 hours. Particularly preferably 3 hours to 10 hours
Time.

The above method is based on the premise that the polyamic acid is synthesized and then the process proceeds to imidization. However, as shown in (c) above, diamine and tetracarboxylic dianhydride are reacted in a reaction solvent. After suspending or dissolving in, at the stage where the synthesis of polyamic acid has not sufficiently proceeded, all the dicarboxylic anhydride, ring-closing catalyst and azeotropic solvent are charged,
There is no problem even if the method of starting heating and heating is adopted. The reaction temperature and reaction time in this case are 150 to 195 as described above.
C. for 3 to 10 hours is preferred. In the case of this method, synthesis of polyamic acid, capping of polymer molecule terminals, and azeotropic distillation of produced water proceed simultaneously.

When chemical imidization or thermal imidization is carried out in a reactor, a method may be employed in which imidization is not completed and polyamic acid is left in a range of 0.1 to 10%. This is because the remaining polyamic acid changes into a stable polyimide in a drying step after coating the polyimide supporting substrate. By leaving a small amount of polyamic acid, it is possible to increase the adhesion to the copper foil and the storage stability (precipitation resistance) of the polyimide varnish. As a method for increasing the precipitation resistance, it is effective to employ a copolymerization method using two or several kinds of tetracarboxylic dianhydrides.

The polyimide varnish thus obtained is coated on one or both sides of a polyimide support substrate and dried to produce a heat-resistant adhesive sheet. When the adhesive layer is a single-sided adhesive sheet on one side, it can be used for coverlay film and lead frame fixing tape,
On the other hand, when the adhesive layer is a double-sided adhesive sheet on both sides, it can be used for a multilayer flexible substrate, a bond ply for rigid flex and an adhesive tape for lead-on-chip. As the polyimide support substrate, any of commercially available polyimides such as Kapton (Dupont Toray), Apical (Kanebuchi Chemical), and Upilex (Ube Industries) may be used. The thickness of the polyimide support substrate is usually 5 to 20.
Use a 0 micron object. If the thickness is less than 5 microns, the film is liable to be cut and is difficult to handle. On the other hand, a film exceeding 200 microns is not suitable for a coverlay film requiring folding resistance. Particularly preferably, it is 10 to 50 microns. Further, in order to increase the adhesiveness with the adhesive layer after drying, a physical treatment such as a mat treatment or an electric treatment such as plasma or corona may be applied to the polyimide support substrate.

The coating and drying of the polyimide varnish is performed by a combination of coating and initial drying with a usual coater drier and subsequent drying with the present drier. As the coater dryer, any of a commonly used comma coater, die coater, three-reverse, and wire bar may be used. Depending on the coating method, the final thickness of the adhesive layer should be 1 to 5
In order to obtain 0 micron, a polyimide varnish having a resin content of 15 to 30% is coated with a thickness of 10 to 400 micron by a coater drier, and the drying temperature is gradually increased within a temperature range of 90 to 180 ° C. to 3 to 15 μm. The initial drying is performed over a period of minutes, the remaining solvent in the adhesive layer is reduced to 25% or less, and the film is wound while drying until there is no tack at the time of winding. .

Next, the temperature is gradually increased by the present dryer, and finally drying is performed at a temperature equal to or higher than the glass transition temperature of the polyimide forming the adhesive layer.
0% or less. Since the glass transition temperature of the polyimide forming the adhesive layer of the adhesive sheet of the present application is 175 to 200 ° C., a final drying temperature of about 240 ° C. can be used. 2
Dry to 50 to 400 ° C. In this case, there is no problem in performance even if the far-infrared heater is additionally used.

When a double-sided adhesive sheet is produced, the first side is coated with a coater drier and dried initially, then the second side is coated and dried in the same manner as described above, and then dried at a high temperature with this drier. Final drying is performed on both sides simultaneously. When the coating is dried on the second side after the initial drying, the adhesive layer on the first side, which has the property that the solvent remains about 10 to 30% and is easy to tack, is inevitably formed on the roll in the coater dryer. Because of the contact, the problem of sticking to the roll is likely to occur. In particular, the present inventors have found that this problem is likely to occur when a large amount of solvent remains in the adhesive layer on the first surface side and the drying on the second surface side is performed at a high temperature for a long time. As countermeasures against this, 1) sufficiently dry after coating on the first side, and 2) dry after coating on the second side at a relatively low temperature for a short time as long as the residual solvent is 25% or less. Do. As another countermeasure against the problem caused by the tack, a method can be adopted in which after coating on the second side, both sides are continuously dried without contacting the roll. That is, in one method, after coating on the second surface side, the air flow from above and below is balanced by a floating dryer, and 90 to 1
This is a method of continuous drying at a temperature range of 80 ° C. Another method is to set up an unwinding winding device at an interval of 3 to 5 m, prepare a drying device in which a drying furnace is installed during this time, and install the unwinding device in the unwinding device. After coating on the second surface side with an attached coater, the film is continuously wound up while applying tension so as not to sag, and is continuously dried in a temperature range of 90 to 180 ° C.

For the production of the single-sided adhesive layer type product, a conventional drying furnace that conveys the roll while contacting the polyimide support base material side with the roll can be used at a temperature of 250 to 400 ° C. Dry in range. On the other hand, in the production of a double-sided adhesive layer type product, it is preferable to dry at a temperature in the range of 250 to 400 ° C. using the two types of double-sided non-contact drying furnace in view of the tack problem described above.

In the present invention, a polyimide varnish in which the polymer molecular ends are capped and imidized is used as a coating varnish. Conventionally, a polyamide acid varnish is generally coated on a polyimide support substrate and dried. This is a method of sometimes imidizing. The major differences in performance between the two methods in the final product are described below.

When a polyamic acid varnish is used as a coating varnish, after coating, imidization and solvent removal are carried out while drying on a polyimide support substrate. We have found that when the product is hot pressed onto a flexible wiring board, the flowability of the adhesive layer is not sufficient, resulting in insufficient adhesive strength. In addition, when imidization is performed on a polyimide supporting substrate, water is easily generated due to the water generated by the imidization, and surface defects are likely to occur. As a result, they have found that the solder heat resistance after lamination tends to be insufficient.

On the other hand, when the polyimide varnish of the present invention, in which the polymer molecular terminals are sealed and imidized, is used as a coating varnish, a simple step of simply removing the solvent is required, and the above-mentioned polyamic acid varnish is used. In this case, there is no problem of cross-linking or surface defects, so that the adhesive strength to the flexible wiring board and the solder heat resistance after lamination are extremely good.

The heat-resistant adhesive sheet according to the present invention can be laminated with a flexible wiring board by using a usual electric heat press, and can obtain an adhesive strength of 0.7 kg / cm or more as a bonding strength with a copper foil glossy surface. The value of 0.7 kg / cm itself is a value that has been difficult to obtain by the conventional method, but according to the present invention, it is 0.7 kg / cm.
In addition to the fact that cm is easily obtained, as shown in the examples below, 0.9 kg / cm and sometimes 1.1 kg / c
It is possible to obtain a surprisingly high adhesive strength of m.

The pressing temperature is sufficient at 210 to 230 ° C. since the glass transition temperature of the thermoplastic polyimide forming the adhesive layer is as low as 175 to 200 ° C. Note that 23
Although the product after lamination has no problem in performance even at 0 ° C or more, since the performance is excellent, the maximum repeated use temperature of the silicone cushion material often used when laminating a coverlay film on a flexible wiring board is 230 ° C.
Therefore, the maximum press temperature is set to 230 ° C. (2
Pressing at a temperature exceeding 30 ° C. significantly shortens the service life). The heat-resistant adhesive sheet according to the present invention is excellent in that it can be laminated in a temperature range in which the general-purpose silicone cushion material can be repeatedly used.

The pressing is usually performed at a pressure in the range of ^{20 to} 75 kg / cm ² . If it is less than 20 kg / cm ² , the expression of adhesive force will be slow or the embedding property will be poor. On the other hand, 75k
At a pressure exceeding g / cm ² , the life of the silicone cushion material is shortened. Pressing is performed 2 to 60 minutes after reaching a predetermined temperature of 210 to 230 ° C. Usually, sufficient adhesive strength can be obtained in 5 to 20 minutes. In the case of a commercially available thermosetting type coverlay film, it is necessary to cure the B-stage adhesive layer at the time of pressing, so that it takes a relatively long time (one hour or more). In the case of an adhesive sheet containing a coverlay film having the following properties, essentially only a time sufficient for fusion is required,
Excellent productivity because only a short press of about a minute is required. Incidentally, the polyimide constituting the adhesive layer in the present invention is 23
The elastic modulus at 0 ° C. is sufficiently small, for example, 10 ³ dynes / cm ² or less. Therefore, when laminating by hot pressing with a copper foil at 230 ° C., a sufficient flow can be obtained because of sufficient flow.

As a set configuration for laminating the coverlay film on the flexible wiring board, a stainless steel plate, a silicone cushion material, a polyimide release film,
The method of laying up a coverlay film, a flexible wiring board, a polyimide release film, a silicon cushion material, and a stainless steel plate in this order is superior in terms of adhesive strength and dimensional change of the flexible wiring board due to lamination.

Polyimide generally absorbs moisture easily, and so does the adhesive layer of the adhesive sheet of the present application. According to the results of studies by the present inventors, a high adhesive strength to a copper foil is exhibited by pre-drying the adhesive sheet and reducing the water content of the adhesive layer. Therefore, the coverlay film must be 100 to 150 in advance.
It is preferable to transfer to a laminate after pre-drying for 0.5 to 5 hours in a temperature range of ° C. Usually 120-130
Drying at about 0.5 ° C. for about 0.5 hour is sufficient.

[0042]

The present invention will be described in more detail with reference to the following examples. Example 1 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube was charged with A
292.2 g (1.0 mol) of PB and 1802.9 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. 308.5 g of ODPA under stirring
(0.995 mol) was added in portions.
Stirred for hours. Then, 4.434 g of phthalic anhydride
(0.03 mol), and the mixture was further stirred at 50 ° C. for 2 hours. The logarithmic viscosity of the polyamic acid thus obtained was 0.69 dl / g (measured by N-methyl-2-
0.5% concentration in pyrrolidone at 35 ° C.).

Acetic anhydride 40 was added to the above polyamic acid solution.
8 g (4.0 mol) and 186.2 g of γ-picoline (2.
(0 mol) was added dropwise and stirring was continued at room temperature for 10 hours. The obtained reaction mixture was discharged into 10 kg of methanol under vigorous stirring, and the precipitate was separated by furnace. The obtained powdery precipitate was further washed with methanol and then dried at 150 ° C. for 12 hours to obtain 556.4 g of a polyimide powder (yield 9).
8.5%). The glass transition temperature of the obtained polyimide powder was 177 ° C. (measured by DSC). 500 g of the polyimide powder thus obtained was dissolved in 1500 g (25% concentration) of N-methyl-2-pyrrolidone to obtain a polyimide varnish for coating.

Using a 25-micron thick apical (manufactured by Kaneka Chemical Co., Ltd.) with a matte treatment on one side as a polyimide support substrate, the above-mentioned polyimide varnish was continuously coated to a thickness of about 100 microns with a usual coater drier. Drying was performed while increasing the temperature stepwise. 90
As a result of drying at １４０140 ° C. for a residence time of about 5 minutes, the residual solvent in the adhesive layer was about 20%. Further drying this at about 300 ℃ with this dryer,
The residual solvent was 0.3%, and the thickness of the adhesive layer was 25 microns.

The cover lay film thus obtained is
After drying at 130 ° C. for 30 minutes, BHY-13-T, 1 Oz
Laminated on the glossy surface of copper foil (manufactured by Nikko Kyoishi). Lamination is performed by using a normal electric heating press, setting the press at room temperature at normal temperature, applying a pressure of 50 kg / cm ² , starting the temperature rise at a set temperature of 230 ° C., and after reaching a predetermined temperature, 20 minutes.
Pressed for minutes. When this laminate was evaluated, the adhesive strength to the copper foil glossy surface was 0.9 kg / cm (3 m
m width, 90 degree peel). It also passed the solder float test at 288 ° C. for 10 seconds (test method was IPC-TM-650, 2.4.13).

Example 2 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube was charged with A
292.2 g (1.0 mol) of PB and 1802.9 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. 308.5 g of ODPA under stirring
(0.995 mol) was added in portions.
Stirred for hours. Then, 4.434 g of phthalic anhydride
(0.03 mol), and the mixture was further stirred at 50 ° C. for 2 hours. Γ is added to the polyamic acid solution thus obtained.
-93.1 g (0.1 mol) of picoline was charged, and the mixture was heated and heated while stirring under a nitrogen stream. During the heating, water produced by the imidization reaction was removed from the system. After the temperature was raised to 180 ° C., thermal imidization was carried out for 5 hours, and during that time, the produced water and the reaction solvent carried by the nitrogen stream were partially removed from the system. After the thermal imidization was performed for 5 hours, the heating was stopped, the mixture was cooled to room temperature in about 2 hours with stirring, and then stirring was continued for 10 hours.

The viscosity of the obtained polyimide varnish is 100
Poise (E-type viscometer, 25 ° C.). The logarithmic viscosity was 0.55 dl / g (measurement was performed by diluting a part of the polyimide varnish with N-methyl-2-pyrrolidone,
% At 35 ° C. ). The glass transition temperature by DSC was 175 ° C. Using the polyimide varnish of the reaction mixture obtained in this example as a varnish for direct coating, a coverlay film was produced in the same manner as in Example 1, and laminated with a copper foil glossy surface at 230 ° C. with an electric heating press. . When evaluated by the same method as in Example 1, the adhesive strength was 1.1 kg / cm, and the solder float test was passed.

Example 3 After a polyamic acid varnish having a polymer end capped was synthesized in the same manner as in Example 2, 93.1 γ-picoline was added.
g (0.1 mol) and 601 g of xylene were heated and heated while stirring under a nitrogen stream. During the temperature rise, water produced by the imidization reaction was removed from the system as an azeotrope with xylene. After the temperature was raised to 180 ° C., thermal imidization was carried out for 5 hours, during which the water distilled off, xylene and N-methyl-2 were distilled off.
-The azeotrope of pyrrolidone was removed out of the system.

The polyimide varnish of the reaction mixture obtained in this example was used as a varnish for direct coating in Example 1.
A coverlay film was produced in the same manner as described above, and laminated with a copper foil glossy surface at 230 ° C. using an electric heating press.
Evaluation was performed in the same manner as in Example 1. As a result, the adhesive strength was 1.0 kg / cm, and passed the solder float test.

Example 4 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet was charged with A
292.2 g (1.0 mol) of PB and 1802.9 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. 308.5 g of ODPA under stirring
(0.995 mol) was charged all at once, followed by stirring for 30 minutes. 4.434 g of phthalic anhydride were added to the obtained suspension.
(0.03 mol), 93.1 g (0.1 mol) of γ-picoline and 601 g of xylene were all charged, and heated and heated while stirring under a nitrogen stream. During the temperature rise, water produced by the imidization reaction was removed from the system while azeotropically coexisting with xylene. After the temperature was raised to 180 ° C., thermal imidization was carried out for 5 hours, and during that time, generated water, xylene and a part of the reaction solvent carried by a nitrogen gas stream were partially removed from the system. After the thermal imidization was performed for 5 hours, the heating was stopped, the mixture was cooled to room temperature in about 2 hours with stirring, and then stirring was continued for 10 hours.

The polyimide varnish of the reaction mixture obtained in this example was directly used as a coating varnish in Example 1.
A coverlay film was produced in the same manner as described above, and laminated with a copper foil glossy surface at 230 ° C. using an electric heating press.
The evaluation was performed in the same manner as in Example 1. As a result, the adhesive strength was 0.9 kg / cm, and passed the solder float test.

Comparative Example 1 A was placed in a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube.
292.2 g (1.0 mol) of PB and 1802.9 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. 308.5 g of ODPA under stirring
(0.995 mol) was added in portions.
Stirred for hours. Then, 4.434 g of phthalic anhydride
(0.03 mol), and the mixture was further stirred at 50 ° C. for 4 hours. The logarithmic viscosity of the polyamic acid thus obtained was 0.69 dl / g (measured by N-methyl-2-
0.5% concentration in pyrrolidone at 35 ° C.). Using the varnish not imidized in this way, that is, the obtained polyamic acid as a coating varnish, a coverlay film was produced in the same manner as in Example 1, and the copper foil glossy surface and 230 var. Laminated at ℃.
When evaluated by the same method as in Example 1, the solder float test was passed, but the adhesive strength was 0.6 kg /
cm.

Comparative Example 2 A was placed in a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube.
292.2 g (1.0 mol) of PB and 1802.9 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. 308.5 g of ODPA under stirring
(0.995 mol) was added in portions.
Stirred for hours. The logarithmic viscosity of the polyamic acid thus obtained was 0.68 dl / g (measured by N-methyl-2-
0.5% concentration in pyrrolidone at 35 ° C.).

Varnish not imidized in this way,
That is, a coverlay film was produced in the same manner as in Example 1 using the obtained polyamic acid as a coating varnish. After drying, surface defects due to foaming were observed on the surface of the adhesive layer. Copper foil glossy surface with electric heating press machine and 230
Laminated at ℃. When evaluated by the same method as in Example 1, the adhesive strength was as low as 0.45 kg / cm, and swelling occurred in the solder float test.

Example 5 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet was charged with A
292.2 g (1.0 mol) of PB and 1838.4 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. BTDA 320.59 was added to this with stirring.
g (0.995 mol) was added in portions, the temperature was raised to 50 ° C., and the mixture was stirred for 1 hour. Then, 4.434 g of phthalic anhydride
(0.03 mol), and the mixture was further stirred at 50 ° C. for 2 hours. 93.1 g (0.1 mol) of γ-picoline was charged into the polyamic acid solution thus obtained, and the mixture was heated and heated while stirring under a nitrogen stream. During the heating, water produced by the imidization reaction was removed from the system. After the temperature was raised to 180 ° C., thermal imidization was carried out for 5 hours, and during that time, the produced water and the reaction solvent carried by the nitrogen stream were partially removed from the system. After the thermal imidization was performed for 5 hours, the heating was stopped, the mixture was cooled to room temperature in about 2 hours with stirring, and then stirring was continued for 10 hours. The viscosity of the obtained polyimide varnish was 60 poise (E-type viscometer, 25 ° C.). The logarithmic viscosity was 0.55 dl / g (measurement was performed using N-methyl-2-
Dilution with pyrrolidone was carried out at 35% at a concentration of 0.5%. ). The glass transition temperature by DSC was 190 ° C.

The polyimide varnish of the reaction mixture obtained in this example was directly used as a coating varnish in Example 1.
A coverlay film was produced in the same manner as described above, and laminated with a copper foil glossy surface at 230 ° C. using an electric heating press.
Evaluation was performed in the same manner as in Example 1. As a result, the adhesive strength was 1.0 kg / cm, and passed the solder float test.

Comparative Example 3 A was placed in a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube.
292.2 g (1.0 mol) of PB and 1838.4 g of N-methyl-2-pyrrolidone were charged and dissolved by stirring at room temperature under a nitrogen atmosphere. BTDA 320.59 was added to this with stirring.
g (0.995 mol) was added in portions, the temperature was raised to 50 ° C., and the mixture was stirred for 4 hours. Using the obtained polyamic acid as a coating varnish, a coverlay film was produced in the same manner as in Example 1, and a copper foil glossy surface was produced using an electric heating press.
Laminated at 0 ° C. When evaluated by the same method as in Example 1, the solder float test was passed.
The bond strength was only 0.4 kg / cm.

Example 6 A polyimide varnish was synthesized in the same manner as in Example 2,
The reaction mixture was directly used as a coating varnish to produce the following double-sided adhesive tape (bond ply). That is, using a 25-micron apical (manufactured by Kanegafuchi Chemical Co., Ltd.) treated with a double-sided mat, usually coats the first surface side with a coater dryer to a thickness of about 100 microns, and gradually increases the temperature by 90-130. About 1 in the temperature range of ℃
After drying so as to have a residence time of 5 minutes, the second surface side is similarly coated with a thickness of about 100 μm, and
Drying was carried out in a temperature range of 20 ° C. so that the residence time was about 6 minutes. Furthermore, it dried so that residence time might be about 20 minutes in the temperature range of 160-270 degreeC under the situation of both sides non-contact in a floating dryer.

The residual solvent in the adhesive layer of the obtained bond ply was 0.5% on average. The thickness of each of the adhesive layers was 25 microns. The thus obtained bond ply is dried at 130 ° C. for 30 minutes, and BHY-13-T, 1 Oz copper foil (manufactured by Nikko Kyoishi) is set on the upper and lower sides of the bond ply, and laminated on the glossy surface of the copper foil. did. Lamination was performed using a normal electrothermal press machine, and after setting in the press machine at room temperature, a pressure of 50 kg / cm ² was applied, the temperature was raised at a set temperature of 230 ° C, and pressing was performed for 20 minutes after reaching the predetermined temperature. . When this laminate was evaluated, the adhesive strength to the copper foil glossy surface was 1.0 kg / cm on the first surface side and 0.9 kg / cm on the second surface side.

Example 7 A polyimide varnish was synthesized in the same manner as in Example 5, and the reaction mixture was directly used as a coating varnish to produce a double-sided adhesive tape (bond ply) in the same manner as in Example 6. The residual solvent in the adhesive layer of the obtained bond ply was 0.6% on average. The thickness of each of the adhesive layers was 24 microns. When the bond ply thus obtained was pressed and evaluated in the same manner as in Example 6, the adhesive strength to the glossy side of the copper foil was 0.9 kg / cm on both the first side and the second side. .

[0061]

The heat-resistant adhesive sheet of the present invention is an all-polyimide heat-resistant adhesive sheet comprising a thermoplastic polyimide adhesive layer and a polyimide support substrate, and has a glass transition temperature of 200 ° C. or less and a high temperature. Since it is particularly excellent in flowability at the time, it can be adhered to an adherend at a low temperature in a short time. In addition, there is no problem in life due to the B-stage as in the thermosetting type, and it is excellent in that it is easy to handle.

The heat-resistant adhesive sheet according to the present invention can be used for a coverlay film and a lead frame fixing tape when the adhesive layer is on one side, and for a multi-layer flexible substrate or a rigid flexible bond ply when the adhesive layer is on both sides. And it is extremely useful as an adhesive tape for lead-on-chip.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-112761 (JP, A) JP-A-5-105850 (JP, A) JP-A-2-27,077 (JP, A) JP-A-61- 291670 (JP, A) JP-A-61-143477 (JP, A) JP-A-5-320339 (JP, A) JP-A-5-5033 (JP, A) JP-A-57-94016 (JP, A) JP-A-4-279662 (JP, A) JP-A-4-198320 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 7/00-7/04 C09J 179/08 H05K 3/28 C08G 73/10

Claims (13)

(57) [Claims] 1. A polymer molecule having a terminal represented by the formula (1): (Wherein, Z is selected from the group consisting of a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-condensed polycyclic aromatic group in which aromatic groups are connected to each other directly or by a bridge member. Embedded image with a dicarboxylic anhydride represented by the following formula (2): (Wherein, Y represents the formula (3) or [Formula 3], and X represents a direct bond, -CO- or -O-). A heat-resistant adhesive sheet formed by forming a thermoplastic polyimide adhesive layer comprising a polymer having a repeating unit represented by the formula on one or both sides of a polyimide support base material. 2. The heat-resistant adhesive sheet according to claim 1, wherein the dicarboxylic anhydride represented by the formula (1) is phthalic anhydride. 3. The heat resistance according to claim 1, wherein polyimide having a glass transition temperature of 200 ° C. or lower is used as an adhesive layer, and can be bonded by fusing to an adherend during hot pressing at 230 ° C. Adhesive sheet. 4. The heat-resistant adhesive sheet according to claim 1, wherein the adhesive strength to the glossy surface of the copper foil is 0.7 kg / cm or more in lamination by hot pressing at 230 ° C. 5. The heat-resistant adhesive sheet according to claim 1, wherein a polyimide having an elastic modulus at 230 ° C. of 10 ³ dynes / cm ² or less is used as the adhesive layer. 6. The polyimide supporting substrate has a thickness of 5 to 200.
The heat-resistant adhesive sheet according to claim 1, wherein the adhesive layer has a thickness of 1 to 50 microns. 7. A polyimide support substrate comprising a polyimide varnish obtained by taking out a polyimide as a polymer, in which the polymer molecular end is sealed with a dicarboxylic anhydride, as a polyimide powder, and then dissolving the polyimide powder in a solvent for dissolving the polyimide powder. The method for producing a heat-resistant adhesive sheet according to claim 1, wherein the adhesive layer is formed by coating and drying the composition. 8. A varnish comprising a reaction mixture obtained by end-blocking polyamic acid and subsequently imidizing the polyamic acid, is directly applied to a polyimide support substrate, and then dried to form an adhesive layer. A method for producing the heat-resistant adhesive sheet according to the above. 9. The method according to claim 8, wherein the reaction mixture in which the imidization is not completed and the polyamic acid remains in the range of 0.1 to 10% is directly cast on a polyimide support substrate and then dried to form an adhesive layer. Production method of heat-resistant adhesive sheet. 10. The method for producing a heat-resistant double-sided adhesive sheet according to claim 7, wherein a varnish is cast on both sides of the polyimide support substrate and dried to form an adhesive layer. 11. After coating and initial drying on the first side with a coater drier, cast and apply on the second side in the same manner to perform initial drying, and then final dry both sides simultaneously with this dryer. The method for producing a heat-resistant double-sided adhesive sheet according to claim 10, wherein 12. To prevent the adhesive layer on the first side from sticking to the rolls in the coater dryer when casting and drying on the second side and initial drying, (1) the first side is dried. After sufficiently reducing the residual solvent over a long period of time at a high temperature, the process proceeds to the casting and the initial drying on the second surface side, and the drying on the second surface is performed at a relatively low temperature in a short time, or (2) 12. The method for producing a heat-resistant double-sided adhesive sheet according to claim 11, wherein, after casting and application on the second side, both sides are continuously dried without contact. 13. The method for producing a heat-resistant double-sided adhesive sheet according to claim 11, wherein when the final drying is carried out simultaneously on both sides by the present dryer, both sides are continuously dried without contact.