JP2005336264A - Polyimidebenzoxazole film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain polyimidebenzoxazole film suitable as a base material for electronic parts withstanding service at extremely high temperatures, having high rigidity and also having extremely high heat resistance. <P>SOLUTION: The polyimidebenzoxazole film is obtained by polycondensation between an aromatic diamine having benzoxazole structure and an aromatic tetracarboxylic acid anhydride. The polyimidebenzoxazole film thus obtained is characterized by that, after preliminarily dried by holding it in an inert atmosphere at 170°C for 7 min, when it is heated at 500°C for 10 s, the amount of moisture volatilized during the heating at 500°C for 10 s is ≤10,000 ppm based on the film prior to undergoing the preliminary drying. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyimide benzoxazole film that is suitable as a base material for electronic components that can withstand use at extremely high temperatures, has high rigidity, and has extremely high heat resistance.

  Polyimide film has excellent heat resistance, electrical properties, mechanical properties, dimensional stability, etc., so flexible printed wiring boards (FPC), carrier tapes for tape automated bonding (TAB), It is used in a wide range of fields such as various electronic materials including base materials for semiconductor mounting, industrial equipment, and high-performance parts such as aircraft.

  In particular, in circuit boards and semiconductor package base materials associated with high-density mounting in recent years, it has become mainstream to use an insulating resin having a low dielectric constant as an interlayer insulating film in order to increase the speed of signal transmission. . A polyimide film is one of the typical insulating materials.

  Usually, a polyimide film is bonded to a copper foil using an adhesive, or processed into a laminate (a polyimide film with a copper foil) composed of a film layer and a copper foil by vapor deposition, plating, sputtering, or casting. In other words, it is used as a base film of a flexible printed multilayer circuit board.

  In recent years, the required characteristics of such multilayer substrates for use as a base material for semiconductor packages have increased, and the same reliability as that of an IC package using a conventional lead frame has been demanded. In reliability testing of semiconductor packages, stability in harsh environments such as high-temperature and high-humidity tests and thermal shock tests is required, and it has become a problem that conventional polyimide films cannot satisfy these requirements.

  For example, in semiconductor mounting, a polyimide film as a base film is heated to a high temperature (about 220 to 320 ° C.) when bonded to a semiconductor chip via solder bumps or the like on lead portions formed on the base film. Due to the exposure, the polyimide film was swollen and the copper foil was peeled off, and the production efficiency was lowered.

  Furthermore, along with an increase in the amount of heat generated by increasing the density of semiconductor elements, there was a problem that the polyimide film was swollen or peeled off in a thermal shock environment due to repeated use and non-use, resulting in poor contact. .

In order to cope with such a problem, a so-called polyimide benzoxazole film is proposed which is made of polyimide having a benzoxazole ring in the main chain and has high heat resistance and rigidity and little dimensional change due to temperature (see Patent Documents 1 to 3). . However, in applications that are used at extremely high temperatures (for example, inorganic thin film forming base materials), the level that satisfies the requirements for reliability has not been reached, and improvement has been strongly desired.
JP-A-6-56992 Japanese National Patent Publication No. 11-504369 Japanese National Patent Publication No. 11-505184

  An object of the present invention is to provide a polyimide benzoxazole film that is suitable as a base material for electronic components that can withstand use at extremely high temperatures, has high rigidity, and has extremely high heat resistance.

In view of this situation, as a result of intensive studies, the present inventors have swelled or peeled off the polybenzoxazole film due to high temperature or thermal shock when condensation of slightly remaining amic acid residues on the polybenzoxazole film. Paying attention to the generated moisture, the amount of residual amic acid is made so low that it cannot be detected by infrared absorption spectrum. The inventors found that a film can be obtained and completed the present invention.
That is, the present invention is a polyimide benzoxazole film obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride, and the polyimide benzoxazole film is formed in an inert gas atmosphere. Then, after pre-drying by holding at 170 ° C. for 7 minutes, when heated at 500 ° C. for 10 seconds, the amount of water that volatilizes while heating at 500 ° C. for 10 seconds is the polyimide benzoxazole film before pre-drying The present invention relates to a polyimide benzoxazole film characterized by being 10,000 ppm or less.
Furthermore, the present invention provides (a) a polyamic acid solution by condensing an aromatic diamine having a benzoxazole structure and a tetracarboxylic acid anhydride in a solvent,
(B) A green film is obtained by applying a polyamic acid solution on a support and drying it until self-supporting property is expressed;
(C) A method for producing the polyimide benzoxazole film, comprising the step of peeling from the obtained support and heat-treating the green film with a temperature profile that stays in a temperature region of 400 ° C. or more for 5 minutes or more. .

  According to the present invention, a polyimide benzoxazole film having a very small amount of volatile moisture at high temperature can be obtained by making the amount of residual amic acid of the polyimide benzoxazole film so small that it cannot be detected by an infrared absorption spectrum. Even when used as a base film for various electronic component laminates and used at high temperatures, the occurrence of swelling and peeling can be prevented. Therefore, the polyimide benzoxazole film of the present invention is useful as a base film for use in the production of a carrier tape for flexible printed wiring copper-clad substrates (FPC) and tape automated bonding (TAB) used at extremely high temperatures. is there.

Hereinafter, embodiments of the polyimide benzoxazole film of the present invention will be described in detail.
The polyimide benzoxazole film of the present invention is a substantially flat film made of polyimide benzoxazole obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic anhydride. After pre-drying by holding at 170 ° C. for 7 minutes under an active gas atmosphere,
When heated at 500 ° C. for 10 seconds,
Amount (ppm) of moisture that volatilizes during heating at 500 ° C. for 10 seconds with respect to the polyimide benzoxazole film before preliminary drying (hereinafter, abbreviated as “volatile water content at high temperature” in this specification) The volatile water content at the high temperature is preferably 7000 ppm or less, more preferably 4000 ppm or less, and further preferably 2500 ppm or less.
When the amount of volatile water at a high temperature is greater than 10000 ppm, swelling of the polyimide benzoxazole film due to generation of voids or the like becomes too large, and contact failure due to peeling tends to occur.
“The amount of volatile water at a high temperature” is preferably as small as possible, but considering the ease of production, cost, etc., it is sufficient that the defect does not substantially occur. As the lower limit, specifically, 10 ppm or more.

  In the measurement of “volatile water content at high temperature”, first, polyimide benzoxazole film is preliminarily dried by holding at 170 ° C. for 7 minutes in an inert gas atmosphere. It is for removing. It is considered that the water generated after the preliminary drying by this step is derived from the water generated by the condensation of the remaining amic acid. Here, examples of the inert gas include helium, argon, neon, and the like.

The amount of volatile water at a high temperature in the present invention is measured by a GCMS method using a Curie point type thermal decomposition apparatus. Specifically, the amount of volatile water at high temperature is measured by the following method. In other words, a polyimide benzoxazole film sample is precisely weighed with 8 mg as a guide (weighing value is A (mg)) in foil that has been heat-dried in advance (for example, pyrofoil manufactured by Nihon Analytical Industrial Co., Ltd.), and a curie point type. Set the heat retention temperature in a pyrolysis apparatus (for example, made by HP, JHS-3, etc.) to 170 ° C., introduce a sample foil, purge with an inert gas (preferably helium) for 7 minutes, and in the film Removes moisture adsorbed on the surface. Then, immediately after heating at 500 ° C. for 10 seconds by an oscillation operation, the area of the water ion peak of m / z = 18 detected by volatilization from the film while heating at 500 ° C. for 10 seconds is obtained, and absolute calibration is performed. The amount of volatile water (B (μg)) is obtained by a linear method, and the amount of volatile water at a high temperature is calculated by the following equation.
Volatile water content at high temperature (ppm) = B (μg) / A (mg) × 1000

  The calibration curve is prepared, for example, by preparing a standard solution obtained by adding a certain amount of water to a solvent (eg, methanol) dehydrated with anhydrous sodium sulfate or the like, and using a water ion peak area of m / z = 18 by GCMS. Can be used. The calibration curve at this time can be expressed by, for example, the formula: generated water content B (μg) = ax + b (where, a represents a slope, b represents an intercept, and x represents a peak area). The generated water content B can be obtained by substituting the area value of the water ion peak.

  Specific examples of aromatic diamines having a benzoxazole structure include the following.

Among these, amino (aminophenyl) benzoxazole isomers are preferable from the viewpoint of ease of synthesis. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above.
Even if this diamine is individual, it is also possible to use 2 or more types.

  In the present invention, one or two or more diamines having no benzoxazole structure exemplified below may be used as long as they are 30 mol% or less of the total diamine. For example, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (3 -Aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3 , 3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3′-diaminodiphenyl ether, 3,4′-diamino Diphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3, '-Diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [ 4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1, 1-bis [4- (4-aminophenoxy) phenyl Propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-amino) Phenoxy) phenyl] propane, 1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4 -(4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphen Nyl] propane, 2- [4- (4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4- Aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,4- Bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis [ 4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide Bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4 ′ -Bis (3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3, 4'-diaminodiphenyl sulfide, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexaph Oropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] Ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 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- ( -Aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4 -Amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1, 3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α, α-dimethyl Benzyl] benzene, 3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamy -4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4 ' -Diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4, 5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4 ' -Diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phen Noxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-) 5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4 -Amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy ] Some or all of the hydrogen atoms on the aromatic ring of benzonitrile and the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms, or alcohols. Examples thereof include an aromatic diamine substituted with a halogenated alkyl group having 1 to 3 carbon atoms in which part or all of the hydrogen atoms of the xyl group, cyano group, or alkyl group or alkoxy group are substituted with a halogen atom, or an alkoxy group. It is done.

  The tetracarboxylic acid anhydrides used in the present invention are aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

  These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are 30 mol% or less of the total tetracarboxylic dianhydrides. Examples of the tetracarboxylic anhydride used include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3,5 , 6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1 -(2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ', 4'-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane -2,3,5,6-tetracarboxylic dianhydride, Cyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid Dianhydrides and the like. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

In the polyimide benzoxazole film of the present invention, first, (a) diamines and tetracarboxylic anhydrides are condensed in a solvent to obtain a polyamic acid solution (hereinafter also referred to as step (a)), and then. (B) A green film is obtained by applying a polyamic acid solution on a support and drying until self-supporting property is developed so that the residual solvent amount is 50% by weight or less based on the total amount of the green film. (Hereinafter also referred to as step (b)), and then (c) the obtained green film is peeled from the support and heat-treated with a temperature profile that stays in a temperature region of 400 ° C. or higher for 5 minutes or longer (hereinafter referred to as “step (b)”). (Also referred to as step (c)).
Hereinafter, the manufacturing method of the polyimide benzoxazole film of the present invention (hereinafter simply referred to as the manufacturing method of the present invention) will be described in detail.

<Process (a)>
The solvent used when polymerizing diamines and aromatic tetracarboxylic acid anhydrides to obtain polyamic acid is not particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. Polar organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexa Examples include methylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the weight of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by weight, The amount is preferably 10 to 30% by weight.

  Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for min to 80 hours. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited, but it is preferable to add aromatic tetracarboxylic acid anhydrides to the solution of aromatic diamines. The weight of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, and the viscosity of the solution is measured with a Brookfield viscometer (25 ° C.). From the viewpoint of the stability of liquid feeding, it is preferably 10 to 2000 Pa · s, and more preferably 100 to 1000 Pa · s.

  Vacuum defoaming during the polymerization reaction is effective for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end-capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.

<Step (b)>
The support on which the polyamic acid solution is applied needs only to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and a drum or belt whose surface is made of metal, plastic, glass, porcelain, etc. And the like. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

  Examples of the support instead of the above include metal plates (foil, film, plate). That is, as a manufacturing method when using a polyimide benzoxazole film, which will be described later, for manufacturing a base substrate for a printed wiring board, a metal plate to be a metal layer of the base substrate is used as a support and a polyamic acid solution is applied thereto. is there. In this case, the means for applying the polyamic acid solution is not particularly limited, and examples thereof include known application means such as a comma coater, a knife coater, a roll coater, a reverse coater, a die coater, a gravure coater, and a wire bar.

  In the step (b), the residual solvent amount (% by weight) with respect to the total weight of the obtained green film is preferably 50% by weight or less, more preferably 40% by weight or less, and still more preferably 35% by weight. It is as follows. When the residual solvent amount is more than 50% by weight, the handling property is inferior, which is not preferable. The lower limit of the residual solvent amount is not particularly limited, but is preferably 25% by weight or more and more preferably 30% by weight or more in order to prevent film breakage in the imidation reaction step. The amount of the residual solvent can be measured (calculated) by TGA (thermogravimetric analysis) or gel permeation chromatograph (GPC).

  As drying conditions for obtaining a green film in which the amount of residual solvent relative to the total weight of the film is within a predetermined range, for example, when N-methylpyrrolidone is used as a solvent, the drying temperature is preferably 70 to 130 ° C., more preferably Is 75 to 125 ° C, more preferably 80 to 120 ° C. When the drying temperature is higher than 130 ° C., the molecular weight is lowered and the green film tends to be brittle. In addition, imidization partially proceeds during the production of the green film, and it becomes difficult to obtain desired physical properties during the imidization process. On the other hand, when the temperature is lower than 70 ° C., the drying time becomes long, the molecular weight tends to decrease, and the handling property tends to be poor due to insufficient drying. The drying time is preferably 10 to 90 minutes, more preferably 15 to 80 minutes, although it depends on the drying temperature. When the drying time is longer than 90 minutes, the molecular weight is lowered and the film tends to be brittle. When the drying time is shorter than 10 minutes, the drying property is insufficient and the handling property tends to be poor. Further, in order to improve the drying efficiency or suppress the generation of bubbles at the time of drying, the temperature may be raised stepwise in the range of 70 to 130 ° C. for drying. A conventionally known drying apparatus that satisfies such conditions can be applied, and examples thereof include hot air, hot nitrogen, far infrared rays, and high frequency induction heating.

<Step (c)>
A polyimide benzoxazole film having a volatile water content at a high temperature of 10,000 ppm or less can be obtained by imidizing the green film obtained in the step (b) under predetermined conditions.
As a specific method of imidization, a conventionally known imidation reaction can be appropriately used. For example, a method (so-called thermal ring closure method) in which an imidization reaction proceeds by subjecting to a heat treatment after performing a stretching treatment if necessary using a polyamic acid solution containing no ring-closing catalyst or a dehydrating agent, or a polyamic acid solution There may be mentioned a chemical ring closing method in which a ring closing catalyst and a dehydrating agent are contained in the catalyst and an imidization reaction is performed by the action of the ring closing catalyst and the dehydrating agent.

In order to obtain a polyimide benzoxazole film with a low amount of volatile moisture at a high temperature, it is necessary to perform heat treatment with a temperature profile that stays for 5 minutes or more in a temperature region of 400 ° C. or higher in both the thermal ring closure method and the chemical ring closure method. Yes, preferably at a temperature range of 400 ° C. to 430 ° C. for 20 minutes or more, more preferably at a temperature range of 430 to 460 ° C. for 10 minutes or more, more preferably at a temperature range of 460 to 500 ° C. for 5 minutes or more. It is. By heat-treating the green film with such a temperature profile, the imidization reaction can proceed so that the amount of volatile water at a high temperature falls below a predetermined range.
The upper limit of the temperature and time of the temperature profile is not particularly limited, but in order to avoid the decomposition of the film, the temperature is 600 ° C. or less, preferably 550 ° C. or less. If considering the productivity, the time is 60 minutes. Hereinafter, it is preferably 40 minutes or less, more preferably 30 minutes or less.

  In the chemical ring closure method, after the polyamic acid solution is applied to a support, the imidization reaction is partially advanced to form a self-supporting film, and then imidization can be performed completely by heating. In this case, the condition for causing the imidization reaction to partially proceed is a heat treatment for 3 to 20 minutes at 100 to 200 ° C., and then the heat treatment may be performed with the above temperature profile.

  The timing for adding the ring-closing catalyst to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline. Among them, heterocyclic tertiary amines are mentioned. At least one amine selected from is preferred. Although the usage-amount of a ring-closing catalyst with respect to 1 mol of polyamic acids does not have limitation in particular, Preferably it is 0.5-8 mol.

  The timing of adding the dehydrating agent to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. Among them, acetic anhydride, benzoic anhydride, etc. Acids or mixtures thereof are preferred. Moreover, the usage-amount of the dehydrating agent with respect to 1 mol of polyamic acids is not particularly limited, but is preferably 0.1 to 4 mol. When a dehydrating agent is used, a gelation retarder such as acetylacetone may be used in combination.

  Although the thickness of a polyimide benzoxazole film is not specifically limited, When considering using it for the base substrate for printed wiring boards mentioned later, it is 5-150 micrometers normally, Preferably it is 8-50 micrometers. This thickness can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.

Next, a printed wiring board base substrate using the above-described polyimide benzoxazole film will be described.
Here, the “base substrate for a printed wiring board” is a substantially flat substrate having a structure in which a metal layer is laminated on at least one surface of an insulating plate. The metal layer to be laminated may be a metal layer for a circuit that is intended to form a circuit by processing such as etching or the like. It may be a metal layer used for the purpose.
As the use of “base substrate for printed wiring board”, FPC, TAB carrier tape, and the like are preferable because the characteristics of the polyimide benzoxazole film of the present invention that the swelling and peeling in a high temperature environment are small can be utilized.

The metal laminated on at least one surface of the polyimide benzoxazole film is not particularly limited, and is preferably copper, aluminum, stainless steel, or the like. The lamination means is not particularly limited, and the following means are exemplified.
-Means for attaching a metal plate to the polyimide benzoxazole film using an adhesive,
-Means for forming a film by applying a polyamic acid solution to a metal plate as a support and imidizing as described above,
-Means for forming a metal layer on the polyimide benzoxazole film using vacuum coating techniques such as vapor deposition, sputtering, ion plating,
-Means for forming a metal layer on a polyimide benzoxazole film by a wet plating method such as electroless plating or electroplating.
A metal layer can be laminated on at least one surface of the polyimide benzoxazole film by using these means alone or in combination.

  The thickness of the metal layer is not particularly limited, but when the metal layer is used for circuit (conductive), the thickness of the metal layer is preferably 1 to 35 μm, more preferably 3 to 18 μm. is there. When using the polyimide benzoxazole film which bonded the metal layer as a heat dissipation board, the thickness of a metal layer becomes like this. Preferably it is 50-3000 micrometers. The surface roughness of the surface of the metal layer bonded to the polyimide is not particularly limited, but the center line average roughness (hereinafter referred to as Ra) and ten points in JIS B 0601 (definition and display of surface roughness). A value represented by average roughness (hereinafter referred to as Rz) is preferably 0.1 μm or less for Ra and 1.00 μm or less for Rz because the effect of improving the adhesion between the film and the metal layer is great. . Of these, those satisfying these conditions are preferred. Although Ra and Rz are preferably as small as possible, the lower limit of Ra is 0.0001 μm and the lower limit of Rz is 0.001 μm because of ease of acquisition and processing.

  An inorganic coating film such as a single metal or a metal oxide may be formed on the surface of the metal layer used in the present invention. Further, the surface of the metal layer may be subjected to treatment with a coupling agent (aminosilane, epoxysilane, etc.), sand plast treatment, hole treatment, corona treatment, plasma treatment, etching treatment, and the like. Similarly, the surface of the polyimide benzoxazole film may be subjected to honing treatment, corona treatment, plasma treatment, etching treatment, and the like.

  Hereinafter, the effectiveness of the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, the evaluation method of the physical property in the following examples is as follows.

1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. using an Ubbelohde type viscosity tube.

2. Method for measuring residual solvent amount Using a TGA apparatus (TG-DTA2000S manufactured by MAC Science), the precursor film was heated from room temperature to 400 ° C. at 10 ° C./min in a nitrogen stream, and 30 ° C. at 400 ° C. The weight loss by heating after holding for a minute was measured, and the weight loss rate was defined as the amount of residual solvent (% by weight) assuming that all the weight loss was volatilized by the residual solvent.

3. Film thickness of the polyimide benzoxazole film The thickness of the film was measured using a micrometer (manufactured by Fine Reef, Millitron 1245D).

4). Tensile modulus, tensile breaking strength and breaking elongation of polyimide benzoxazole film Cut the dried film into strips of length 100mm and width 10mm in the longitudinal direction (MD direction) and width direction (TD direction), respectively. And using a tensile tester (manufactured by Shimadzu Autograph (R) model name AG-5000A) under the conditions of a tensile speed of 50 mm / min and a distance between chucks of 40 mm. The tensile strength and elongation at break were determined.

5). Linear expansion coefficient (CTE) of polyimide benzoxazole film
About the polyimide benzoxazole film to be measured, the stretch rate in the MD direction and the TD direction is measured under the following conditions, and the stretch rate / temperature at intervals of 30 ° C. to 45 ° C., 45 ° C. to 60 ° C.,. Was measured up to 300 ° C., and the average value of all measured values was calculated as CTE. The meanings of the MD direction and the TD direction are the same as in the measurement of “3.” above.
Device name: TMA4000S manufactured by MAC Science
Sample length; 20mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

6). The melting point and glass transition temperature of the polyimide benzoxazole film were subjected to DSC measurement under the following conditions, and the melting point (melting peak temperature Tpm) and glass transition point (Tmg) were determined under the following measurement conditions in accordance with JIS K7121.
Device name: DSC3100S manufactured by MAC Science
Pan ： Aluminum pan (non-airtight)
Sample weight; 4mg
Temperature rising start temperature: 30 ° C
Temperature increase rate: 20 ° C / min
Atmosphere: Argon

7). Thermal decomposition temperature of polyimide benzoxazole film The thermal decomposition temperature was defined by 5% weight loss by TGA measurement (thermobalance measurement) of a fully dried sample under the following conditions.
Device name: TG-DTA2000S manufactured by MAC Science
Pan ： Aluminum pan (non-airtight)
Sample weight: 10mg
Temperature rising start temperature: 30 ° C
Temperature increase rate: 20 ° C / min
Atmosphere: Argon

8). Volatile water content of polyimide benzoxazole film at high temperature The volatile water content was determined from the GCMS method using a Curie point thermal decomposition apparatus.
A sample (guideline 8 mg) is precisely weighed in a pyrofoil for use at 500 ° C. manufactured by Nihon Analytical Industries in advance (weighing value is A (mg)), and the temperature inside the thermal decomposition apparatus is set to 170 ° C. The sample foil was introduced and purged with helium for 7 minutes to preliminarily remove the water adsorbed in the film. Immediately thereafter, heating was performed at 500 ° C. for 10 seconds by an oscillation operation. A water ion peak at m / z = 18 was detected by GCMS for the water volatilized from the film during the heating at 500 ° C. for 10 seconds. This peak area was determined, and the amount of generated water B (μg) was determined by an absolute calibration curve method. A calibration curve was prepared by preparing a standard solution to which a predetermined amount of water was added in two or more levels using dehydrated methanol with anhydrous sodium sulfate as a preparation reagent, and using a peak area of m / z = 18 by GCMS. At this time, the calibration curve was set as y = ax + b (a: slope, b: intercept, y: generated water amount B (μg), x: peak area). The amount of volatile water at a high temperature relative to the polyimide benzoxazole film was calculated by the following formula.
Volatile water content at high temperature (ppm) = B (μg) / A (mg) × 1000
Pyrolysis GCMS conditions Equipment: HP5971A (HPMS GCMS),
JHS-3 (Nippon Analytical Industrial Pyrolysis System)
Column: PORAPLOT-Q (manufactured by GL Sciences Inc.), φ0.32 mm × 10 m
Column temperature: 60 ° C constant Flow rate: He 0.7 ml / min, split introduction

9. Solder heat resistance and contact failure rate of polyimide benzoxazole film <Preparation of adhesive>
As an adhesive, (A) polyamide resin (acid content: dimer acid, amine component: hexamethylenediamine, acid value 1.0, amine value 0), (B) epoxy resin I: 4,4′-bis (2, 3-epoxypropoxy) -3,3 ′, 5,5′-tetramethylbiphenyl (epoxy equivalent: 190) (C) epoxy resin II. Bisphenol A type epoxy resin (epoxy equivalent: 186), (D) phenol resin resol phenol "CKM-1282" (manufactured by Showa Polymer Co., Ltd.), (E) additive 2-heptadecylimidazole, 50.0: It mix | blended in the ratio (mass ratio) of 8.0: 12.0: 29.5: 0.5, and obtained the adhesive agent.

<Manufacture of build-up multilayer wiring boards>
A four-layer printed wiring board of FR4 was used as a core layer, and a build-up multilayer printed wiring board shown in FIG. 1 was prototyped. The copper foil thickness on the core layer surface is 25 μm. First, an adhesive solution was applied to one side of a polyimide film and dried at 80 ° C. for 40 minutes. The dry film thickness of the adhesive was 25 μm. Next, polyimide films coated with an adhesive on both surfaces of the core substrate were stacked and temporarily pressure-bonded with a vacuum laminator, and then pressed with a hot plate press heated to 150 ° C. to an actual load of 20 kgf / cm ² for 30 minutes. A YAG laser was used for drilling. The via diameter is 150 μm. After drilling, desmear treatment, washing with water, plasma treatment of the entire surface of the substrate, conditioning, catalyst application, activation, electroless copper plating of 0.8μm thickness in formalin reducing bath, then copper sulfate plating The thickness of the copper foil at the stage where electric thickening plating and via fill plating were performed in a bath and the surface was buffed to ensure flatness was 15 μm. Pattern formation was performed by laminating, exposing and developing a dry film resist having a thickness of 25 μm, etching with a cupric chloride solution, and then removing the resist and washing with diluted sulfuric acid to form a conductor pattern with a thin line width of 70 μm.

<Solder heat resistance>
The second buildup layer was formed in the same manner as the first buildup layer except that the adhesive applied to the polyimide film was 15 μm. Through the above steps, a total of 8 multilayer printed wiring boards having two build-up layers on each side were obtained.
The obtained multilayer printed wiring board was immersed in a tin-copper-silver-based lead-free solder bath heated to 280 ° C. for 10 seconds, and the presence or absence of peeling or swelling was observed visually.
Next, the ETC (R) temperature cycle test device (manufactured by Enomoto Kasei Co., Ltd.) is charged, and the heating / cooling cycle test is performed by repeatedly heating and cooling between a low temperature of -50 ° C and a high temperature of 150 ° C every 30 minutes. The sample was immersed in a tin-copper-silver-based lead-free solder bath heated to 280 ° C. for 10 seconds after the test, and the presence or absence of peeling or swelling was visually observed.

<Contact failure rate>
A 7 mm × 7 mm semiconductor chip was mounted on the obtained multilayer printed wiring board (25.4 mm × 25.4 mm) by face-down bonding. The number of contacts is 256.
A cycle test in which the package is loaded into an ETAC (R) temperature cycle test apparatus (manufactured by Enomoto Kasei Co., Ltd.) and repeatedly cooled and heated between a low temperature of −50 ° C. and a high temperature of 150 ° C. every 30 minutes is performed. Time done. A continuity test was conducted after the test to determine the defect rate at the connection point.

(Example 1)
<Polymerization and Film Production Example 1>
The inside of a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was purged with nitrogen, and then 500 parts by weight of 5-amino-2- (p-aminophenyl) benzoxazole was charged. Next, 5000 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved, and then 485 parts by weight of pyromellitic dianhydride was added and stirred at a reaction temperature of 25 ° C. for 15 hours. A polyamic acid solution was obtained. Ηsp / C of this product was 4.0.

  Subsequently, this polyamic acid solution was coated on a stainless steel belt with a squeegee / belt gap of 650 μm and dried at 90 ° C. for 60 minutes. The polyamic acid film that became self-supporting after drying was peeled off from the stainless steel belt to obtain a green film having a thickness of 40 μm. The residual solvent amount of the green film at this time was 39%. The obtained green film was passed through a continuous drying furnace and heat-treated at 170 ° C. for 3 minutes, then heated to 450 ° C. at a rate of about 70 ° C./minute, and heat-treated at 450 ° C. for 10 minutes. After cooling to room temperature over a period of 25 minutes, a brown polyimide benzoxazole film (film 1) having a thickness of 25 μm was obtained. The characteristic value of the obtained polyimide benzoxazole film was evaluated. Moreover, a buildup multilayer wiring board was manufactured using the obtained polyimide benzoxazole film, and solder heat resistance and contact failure rate were evaluated. The results are shown in Table 1.

(Example 2, Comparative Examples 1 and 2)
A polyimide benzoxazole film and a build-up multilayer wiring board were obtained and evaluated in the same manner as in Example 1 except that the temperature profile of the heat treatment was as shown in Table 1. The results are shown in Table 1.

  Solder heat resistance and contact failure of the polyimide benzoxazole films of Examples 1 and 2 having a volatile water content of 10000 ppm or less at high temperatures were good, but in Comparative Examples 1 and 2, soldering was performed after the heating / cooling cycle test. In the heat test, a leak occurred and the contact failure rate was poor.

  Since the polyimide benzoxazole film of the present invention has an extremely small amount of volatile water at high temperatures, it can be prevented from being swollen or peeled off when used at various temperatures as a base film for various electronic component laminates. Therefore, the polyimide benzoxazole film of the present invention is useful as a base film for use in the production of copper-clad substrates for flexible printed wiring (FPC) and tape automated bonding (TAB) used at extremely high temperatures. .

It is the schematic which shows the process of forming the 1st buildup layer in buildup multilayer wiring board manufacture. It is the schematic which shows the process of forming the 2nd buildup layer in buildup multilayer wiring board manufacture.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core substrate 2 Core substrate conductor pattern 3 Adhesive layer 4 Heat-resistant film (polyimide benzoxazole film)
5 Build-up conductor layer

Claims (2)

A polyimide benzoxazole film formed by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid anhydride,
The polyimide benzoxazole film is preliminarily dried by holding at 170 ° C. for 7 minutes in an inert gas atmosphere, and then volatilized during heating for 10 seconds at 500 ° C. A polyimide benzoxazole film, characterized in that the amount is 10,000 ppm or less with respect to the polyimide benzoxazole film before preliminary drying. (A) A polyamic acid solution is obtained by condensing an aromatic diamine having a benzoxazole structure and a tetracarboxylic acid anhydride in a solvent,
(B) A green film is obtained by applying a polyamic acid solution on a support and drying it until self-supporting property is expressed;
(C) The polyimide benzoxazole film according to claim 1, comprising a step of peeling the obtained green film from the support and heat-treating with a temperature profile that stays in a temperature region of 400 ° C. or more for 5 minutes or more. Manufacturing method.

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