JP5447365B2 - Manufacturing method of laminate - Google Patents

Description

  The present invention relates to a method for producing a laminate by directly applying, drying, and heat-treating a polyimide resin solution on a metal foil, and more particularly to a method for producing a laminate including a drying / heat treatment step using superheated steam. Is.

  In an electronic circuit of an electronic device, a printed wiring board obtained by processing a laminated board made of an insulating material and a conductive material is used. Printed wiring boards can be broadly classified into plate-shaped rigid printed wiring boards and flexible printed wiring boards with great flexibility.

There are a three-layer flexible substrate and a two-layer flexible substrate as flexible substrates used as the material of the flexible printed wiring board. The three-layer flexible substrate is obtained by bonding a base film such as polyimide and a copper foil using an adhesive such as an epoxy resin, an acrylic resin, or a polyester resin. On the other hand, the two-layer flexible substrate is obtained by providing a heat-resistant insulating layer directly on a copper foil without using an adhesive. There are the following three methods for obtaining a flexible substrate without using an adhesive such as epoxy resin, acrylic resin or polyester resin.
(1) A polyimide-based heat-resistant resin solution is applied to a metal foil such as a copper foil, dried, and heat-treated as necessary.
(2) A thermoplastic heat-resistant resin layer is provided on at least one side of a heat-resistant film such as a polyimide film, and the thermoplastic resin layer and a metal foil such as a copper foil are bonded together.
(3) Plating such as copper plating is applied to a heat-resistant film such as a polyimide film.
A method of applying a polyimide-based heat-resistant resin solution to a metal foil such as a copper foil, drying it, and subjecting it to a heat treatment if necessary is called a casting method. Since the flexible wiring board obtained by the casting method has excellent dimensional stability, it is a material corresponding to the recent increase in density and fine pitch of printed wiring boards.

  As the drying method used for drying the solvent of the heat-resistant resin solution during the production of the cast method flexible substrate, hot air drying, hot roll contact drying, infrared heating drying, far infrared heating drying, or the like is used. Examples of the heat resistant resin used at this time include a polyimide precursor resin, a solvent-soluble polyimide resin, and a polyamideimide resin. As these solvents, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone, phenol, cresol and the like are used, but these solvents have a high boiling point and thus have poor drying properties. In particular, amide solvents such as N-methyl-2-pyrrolidone and N, N-dimethylacetamide have low vapor pressure due to intermolecular hydrogen bonding, and the diffusion of the solvent is poor due to the high glass transition temperature of the heat-resistant resin. Yes, it tends to remain in the coating film. Residual solvent causes a decrease in heat resistance and a decrease in dimensional stability. If the drying temperature or heat treatment temperature is too high in order not to leave the solvent, the discoloration or characteristic change of the copper foil, the adhesive strength is reduced due to the deterioration of the resin, or the mechanical characteristics are deteriorated. Drying and heat treatment are performed over time in order to avoid adverse effects caused by an increase in drying and heat treatment temperature and prevent the solvent from remaining. Therefore, there is a problem in productivity.

Superheated steam refers to steam that has been heated by heating saturated steam without increasing the pressure. Since superheated steam has a radiant heat energy significantly higher than that of normal steam at a temperature of 150 ° C. or higher, the substance can be heated in a short time. Superheated steam is used for cooking food, washing resin products and metal products, sterilizing food containers, or treating soil. The use of superheated steam as a heating heat source is not very popular except for cooking food.
However, when superheated steam is compared with general heated air, it has the following characteristics.
(1) Since the heat capacity is larger than that of heated air, rapid heating is possible.
(2) Since it has a constant-pressure specific heat about twice that of heated air, it has excellent heating capacity.
(3) Since it has latent heat energy, its enthalpy is larger than that of heated air.
(4) Although heat transfer by air is limited to convection heat transfer, superheated steam has a high heat efficiency because of the combined heat transfer action from convection heat transfer, radiant heat transfer, and condensation heat transfer.
It is known in Patent Documents 1 to 6 to dry superheated steam as a heating heat source. Patent Documents 1 to 5 propose a method of drying moisture of wet paper mainly composed of cellulose fibers with superheated steam. Patent Document 6 proposes application of superheated steam to a polyolefin film, a polyamide film, a coating film on a polyester film, or a wet cellophane film.

Japanese Patent No. 2907265 Japanese Patent No. 2907266 Japanese Patent No. 3007542 Japanese Patent Publication No. 2003-41495 Japanese Patent Publication No. 2005-15924 Japanese Patent Publication No. 2007-276283

  An object of the present invention is to increase the heating and drying efficiency by using superheated steam when producing a laminate by a casting method. Furthermore, it is providing the manufacturing method of a laminated body which does not have the harmful | toxic effect by a residual solvent or overheating.

As a result of intensive studies on a method for producing a cast laminate, the present inventors have arrived at the present invention by the following means.
(Claim 1)
A method for producing a laminate of the polyimide resin solution was coated and dried on a metal foil having an insulating resin layer, viewed including the step of heat treatment using the superheated steam, the polyimide resin is, is a polyamide-imide resin The manufacturing method of the laminated body characterized by the above-mentioned.
(Section 2)
The manufacturing method of the laminated body of claim | item 1 which heat-processes at 150-400 degreeC using superheated steam.
(Section 3)
Item 3. The method for producing a laminate according to Item 1 or 2, wherein the residual solvent concentration in the polyimide resin layer after the heat treatment is 0.7% by weight or less.
(Section 4 )
Item 4. The method for producing a laminate according to any one of Items 1 to 3 , wherein the polyimide resin solution is applied onto the metal foil such that the thickness after the heat treatment is 5 μm to 100 μm.
(Section 5 )
Item 5. The method for producing a laminate according to any one of Items 1 to 4 , wherein primary drying is performed before the heat treatment.
(Claim 6 )
Item 6. The method for producing a laminate according to Item 5 , wherein primary drying is performed at 60 to 150 ° C.

  According to the present invention, a laminate composed of a metal foil and a heat-resistant insulating layer can be produced efficiently. In addition, the laminate obtained by the present invention can improve the adverse effects caused by the solvent remaining in the heat-resistant insulating layer, such as a decrease in heat resistance and a deterioration in dimensional stability. Furthermore, adverse effects caused by excessive heating, such as a decrease in peel strength between the metal and the resin layer and a deterioration in the physical properties of the resin, can be improved at the same time.

  Examples of the polyimide resin used in the present invention include a polyimide precursor resin, a solvent-soluble polyimide resin, and a polyamideimide resin. The polyimide resin can be polymerized by a usual method. For example, a method of obtaining a polyimide precursor solution by reacting tetracarboxylic dianhydride and diamine in a solution at low temperature, and a method of obtaining a solvent-soluble polyimide solution by reacting tetracarboxylic dianhydride and diamine in a high temperature solution. There are a method using isocyanate as a raw material and a method using acid chloride as a raw material.

  The raw materials used for the polyimide precursor resin and the solvent-soluble polyimide resin include the following. Examples of acid components include pyromellitic acid, benzophenone-3,3 ', 4,4'-tetracarboxylic acid, biphenyl-3,3', 4,4'-tetracarboxylic acid, diphenylsulfone-3,3 ', 4, 4'-tetracarboxylic acid, diphenyl ether-3,3 ', 4,4'-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, naphthalene-1,2,4,5-tetracarboxylic acid , Monoanhydrides, dianhydrides, esterified products such as naphthalene-1,4,5,8-tetracarboxylic acid, hydrogenated pyromellitic acid, hydrogenated biphenyl-3,3 ', 4,4'-tetracarboxylic acid Etc. can be used alone or as a mixture of two or more. Examples of the amine component include p-phenylenediamine, m-phenylenediamine, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 3,4'-diaminobiphenyl, 3,3-diaminobiphenyl, 3,3'-diaminobenzanilide, 4,4'-diaminobenzanilide, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 3 , 4'-diaminobenzophenone, 2,6-tolylenediamine, 2,4-tolylenediamine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylhexafluoropropane, 3,3'-diaminodiphenylhexafluoropropane, 4,4 ' -Diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylhexafluoroisopropylidene, p-xylenediamine, m-xylenediamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 2, 6-naphthalenediamine, 2,7-naphthalenediamine, o-tolidine, 2,2'-bis (4-aminophenyl) propane, 2,2'-bis (4-aminophenyl) hexafluoropropane, 1,3- Bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl ] Propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- ( 3-aminofe Noxy) phenyl] hexafluoropropane, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) Phenyl] hexafluoropropane, cyclohexyl-1,4-diamine, isophoronediamine, hydrogenated 4,4'-diaminodiphenylmethane, 4,4'-diamino-2,2'-dimethylbiphenyl, 3,3'-dimethyl- 4,4'-diaminobiphenyl or the like, or a diisocyanate compound corresponding to these, or a mixture of two or more thereof can be used. In addition, a resin separately polymerized by a combination of these acid component and amine component can be mixed and used.

  Raw materials used for polyamideimide resins include trimellitic anhydride, diphenyl ether-3,3 ', 4'-tricarboxylic acid anhydride, diphenylsulfone-3,3', 4'-tricarboxylic acid anhydride, benzophenone as acid components Tricarboxylic acid anhydrides such as -3,3 ′, 4′-tricarboxylic acid anhydride, naphthalene-1,2,4-tricarboxylic acid anhydride, and hydrogenated trimellitic acid anhydride may be used alone or as a mixture. In addition to tricarboxylic acid anhydrides, tetracarboxylic acids mentioned in the polyimide resin, their anhydrides, dicarboxylic acids and the like can also be used in combination. Examples of the amine component include diamines mentioned for polyimide resins, or diisocyanates alone or as a mixture. In addition, a resin separately polymerized by a combination of these acid component and amine component can be mixed and used.

  The solvent of the polyimide resin solution used in the present invention is that the solubility of the polyimide resin is good, the formation of water and an azeotropic compound in the gas layer, and the compatibility with water is the effect of superheated steam To increase. Further, if the solvent is compatible with water, the evaporated solvent can be easily recovered, which is industrially advantageous. Specifically, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, cyclopentanone and the like can be mentioned. Of these, N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferred. Further, a solvent such as toluene, xylene, diglyme, tetrahydrofuran, methyl ethyl ketone, etc. may be added as long as the solubility is not inhibited.

 Although the concentration of the polyimide resin in the polyimide resin solution can be selected from a wide range, it is generally preferably about 5 to 60% by weight, particularly preferably about 8 to 30% by weight from the viewpoint of workability.

  Examples of the metal foil used in the present invention include copper foil, aluminum foil, stainless steel foil, steel foil, and nickel foil. You may use the composite metal foil which compounded these metal foils, and the metal foil processed with other metals, such as zinc and chromium. Moreover, you may perform the surface treatment of metal foil with a silane coupling agent or a titanium coupling agent. The thickness of the metal foil is not particularly limited, but a 1 mm metal sheet can be used from an ultrathin copper foil with a carrier of 2 μm.

  In the present invention, other resins and various additives may be blended or reacted for the purpose of improving various properties of the metal laminate, such as mechanical properties, electrical properties, slipperiness, and flame retardancy. Examples of the lubricant include silica, talc, and silicone compounds. Examples of the flame retardant include phosphorus-containing compounds, triazine compounds, aluminum hydroxide, and magnesium hydroxide. Also included are stabilizers such as antioxidants and UV absorbers, plating activators, and organic and inorganic fillers. Moreover, you may mix | blend other resins, such as hardening | curing agents, such as an isocyanate compound, an epoxy resin, and a phenol resin, a polyester resin, a polyurethane resin, and a polyamide resin.

  The manufacturing method of the laminated body of this invention is demonstrated. It is desirable to apply a polyimide resin solution to a metal foil and perform primary drying, followed by drying and heat treatment at a higher temperature. The polyimide resin solution is preferably applied so that the thickness after application, drying, and heat treatment is 5 μm to 100 μm, and more preferably 10 μm to 50 μm. By adjusting the residual solvent ratio in the coat layer after primary drying to preferably 5 to 35% by weight, more preferably 15 to 30% by weight, it is possible to reduce the influence of volume shrinkage due to solvent evaporation. Effective in improving peel strength and curl. The primary drying conditions are preferably 60 to 150 ° C. and 1 to 10 minutes. Superheated steam may be used during the primary drying.

After the primary drying, the next heat treatment (secondary heat treatment) is performed. When the polyimide resin is a polyimide precursor resin, a heat treatment involving an imidization reaction is performed. When the polyimide resin is a solvent-soluble polyimide resin or polyamideimide resin, the solvent is removed by heating. The secondary heat treatment always includes heat treatment with superheated steam. The treatment with superheated steam may be used in combination with hot air drying or infrared or far infrared drying. The temperature of the superheated steam used is preferably 150 to 400 ° C, more preferably 200 to 350 ° C. It is preferable to adjust the treatment time so that the residual solvent concentration in the polyimide resin layer after the secondary heat treatment is preferably 0.7% by weight or less, more preferably 0.5% by weight or less. If it is less than 150 ° C., sufficient effects may not be obtained. If it exceeds 400 ° C., the solvent may suddenly boil and a good laminate may not be obtained, and the resin may be deteriorated. Since the temperature is higher than 150 ° C. during the secondary heat treatment, discoloration of metal foil and changes in physical properties may occur. If necessary, it is necessary to lower the oxygen concentration. When copper foil is used, it is desirable to reduce the oxygen concentration to 5% or less, preferably 0.5% or less.
Although it is desirable to perform primary drying and secondary heat treatment separately from the adhesive force and curling, etc., when the thickness of the polyimide resin layer is 15 μm or less, it can be continuously performed without dividing both steps.
After the secondary heat treatment, the laminate may be heat-treated or solvent-removed in a roll shape. The heat treatment in the form of a scroll is preferably performed under reduced pressure or in an inert gas.

  In order to describe the present invention in more detail, examples are given below, but the present invention is not limited to the examples. In addition, the measured value described in the Example is measured by the following method.

  Residual solvent: Residue in polyimide resin layer due to weight reduction from 150 ° C to 350 ° C (heating rate 30 ° C / min) using differential thermal and thermogravimetric simultaneous measurement device EXSTAR6000TG / DTA manufactured by Seiko Instruments Inc. The solvent concentration was determined. It is preferably 0.7% by weight or less, particularly preferably 0.5% by weight or less.

  Solder heat resistance: The copper foil of the copper foil laminate was etched by a subtractive method to create a circuit pattern having a width of 1 mm. After humidity conditioning at 40 ° C. and 65% RH for 24 hours and flux cleaning, the sample was immersed in a jet solder bath at 320 ° C. for 20 seconds, and the presence or absence of peeling or swelling was observed with a microscope. The thing in which abnormality was not seen was set as (circle), and the thing in which peeling or swelling was seen was set as x.

  Adhesive force: The above-mentioned sample on which a circuit pattern having a width of 1 mm was measured was measured at a pulling speed of 50 mm / min, a measurement temperature of 20 ° C., and a peeling angle of 90 degrees.

  Dimensional stability: The dimensional change rate in the MD and TD directions by heat treatment at 150 ° C. for 30 minutes was determined by IPC-FC241 (IPC-TM-650, 2.2.4 (c)). The average values in the MD and TD directions are shown in the table.

Synthesis example 1
In a reaction vessel, 192 g of trimellitic anhydride, 211 g of 3,3′-dimethyl-4,4′-biphenyl diisocyanate, 35 g of 2,4-tolylene diisocyanate, 0.5 g of sodium methylate and N-methyl-2-pyrrolidone 5 kg was added, and the temperature was raised to 150 ° C. over 1 hour, and further reacted at 150 ° C. for 5 hours. The obtained polyamideimide resin had a logarithmic viscosity of 1.6 dl / g and a glass transition temperature of 320 ° C.

Synthesis example 2
850 g of N, N-dimethylacetamide, 47.7 g of 4,4′-diamino-2,2′-dimethylbiphenyl and 20.7 g of 4,4′-bis (3-aminophenoxy) biphenyl are put into a reaction vessel and stirred. And dissolved. Next, 80.4 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added, and stirring was continued at room temperature for 5 hours to obtain a polyimide precursor.

<Example 1>
Using an applicator, the polyamideimide solution prepared in Synthesis Example 1 is applied by hand to a copper foil (35 μm electrolytic copper foil manufactured by Mitsui Mining & Mining Co., Ltd.) so that the thickness after drying is 25 μm. Primary dried. Further, a steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High Frequency Industrial Co., Ltd.) was used as a generator for generating normal pressure superheated steam, and heat treatment was performed with superheated steam. As evaluation of the obtained copper-clad laminate, the amount of residual solvent, solder heat resistance, adhesive strength, and dimensional stability were measured. The results are shown in Table-1.

<Example 2>
Using an applicator, the polyimide precursor solution prepared in Synthesis Example 2 was applied by hand to a copper foil (electrolytic copper foil made by Mitsui Mining & Mining Co., Ltd. 35 μm) so that the thickness after dry ring closure would be 25 μm. Primary drying for 5 minutes. Further, heat treatment was performed for 30 minutes from 100 ° C. to 310 ° C. at a heating rate of 7 ° C./min. Further, a steam superheater (“DHF Super-Hi 10” manufactured by Daiichi High Frequency Industrial Co., Ltd.) was used as a generator for generating normal pressure superheated steam, and heat treatment was performed with superheated steam. As evaluation of the obtained copper-clad laminate, the amount of residual solvent, solder heat resistance, adhesive strength, and dimensional stability were measured. The results are shown in Table-1.

<Comparative Example 1>
Using an applicator, the polyamideimide solution prepared in Synthesis Example 1 is applied by hand to a copper foil (35 μm electrolytic copper foil manufactured by Mitsui Mining & Mining Co., Ltd.) so that the thickness after drying is 25 μm. Primary dried. Only hot air drying was performed as the secondary heat treatment. As evaluation of the obtained copper-clad laminate, the amount of residual solvent, solder heat resistance, adhesive strength, and dimensional stability were measured. The results are shown in Table-1.

<Comparative Example 2>
Using an applicator, the polyimide precursor solution prepared in Synthesis Example 2 was applied by hand to a copper foil (35 μm electrolytic copper foil manufactured by Mitsui Mining & Mining Co., Ltd.) so that the thickness after dry ring closure would be 25 μm. Primary drying for 5 minutes. Further, heat treatment was performed for 30 minutes from 100 ° C. to 310 ° C. at a heating rate of 7 ° C./min. Subsequently, hot air drying was performed. No heat treatment with superheated steam was performed. As evaluation of the obtained copper-clad laminate, the amount of residual solvent, solder heat resistance, adhesive strength, and dimensional stability were measured. The results are shown in Table-1.

  The present invention relates to a simple method for producing a metal laminate, and by using this production method, the productivity can be improved, and a metal laminate excellent in heat resistance, durability and dimensional stability is provided. be able to.

Claims (6)

A method for producing a laminate of the polyimide resin solution was coated and dried on a metal foil having an insulating resin layer, viewed including the step of heat treatment using the superheated steam, the polyimide resin is, is a polyamide-imide resin The manufacturing method of the laminated body characterized by the above-mentioned. The manufacturing method of the laminated body of Claim 1 which heat-processes at 150-400 degreeC using superheated steam. The method for producing a laminate according to claim 1 or 2, wherein the residual solvent concentration in the polyimide resin layer after the heat treatment is 0.7 wt% or less. The method for producing a laminate according to any one of claims 1 to 3 , wherein the polyimide resin solution is applied onto the metal foil so that the thickness after the heat treatment is 5 µm to 100 µm. The method for producing a laminate according to any one of claims 1 to 4 , wherein primary drying is performed before the heat treatment. The method for producing a laminate according to claim 5 , wherein primary drying is performed at 60 to 150 ° C.