JP4493114B2 - Conductor laminate using solvent-soluble polyimide and its production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductor laminate that can be used for a flexible circuit board and a method for producing the same.
[0002]
[Prior art]
In recent years, the demand for flexible printed circuit (hereinafter referred to as FPC) has been rapidly increasing because its flexibility, light weight, and thinness match the downsizing and weight reduction of electronic devices. Insulating resins used for FPC mainly include polyimide materials and polyester materials, and small amounts of glass / epoxy materials are used. Among them, the polyimide-based material has the most excellent characteristics in heat resistance, electrical characteristics and the like, and is expected to become a mainstream material in the future.
[0003]
At present, there are two types of FPCs known: a three-layer structure and a two-layer structure. The three-layer structure FPC typically has a structure in which a polyimide film and a copper foil are bonded together with an adhesive. On the other hand, the two-layer structure FPC typically has a structure in which only polyimide and copper foil are bonded together.
[0004]
Since the three-layer FPC has an adhesive layer, there is a problem that even if it can withstand a short heat treatment, the adhesive deteriorates when the heat treatment is performed for a long time, and the reliability is lowered. In addition, there is a problem in that copper migration occurs in the adhesive and plating liquid permeates into the adhesive.
[0005]
On the other hand, since the two-layer FPC does not have an adhesive layer, it has many excellent characteristics. Advantages include excellent heat resistance, flame retardancy, low dielectric constant and dielectric loss tangent, low frequency dependence and temperature dependence, high surface resistance and volume resistance, and stability to various treatments. There are few ionic impurities, high reliability, small dimensional change rate, almost the same change rate in the XY directions, and small degradation of peeling strength due to heat. As described above, the two-layer FPC has very excellent characteristics, and is currently used in a hard disk drive, a floppy disk drive, a printer, and the like that require high flexibility. It is also used for parts in the engine compartment of automobiles that require high heat resistance and gasoline tank level sensors that require chemical resistance.
[0006]
The production method of the two-layer FCP having such excellent performance includes a casting method in which a polyimide amic acid varnish is applied on a copper foil, dried and cured, a sputtering method in which copper is folded on a polyimide film, and There is a plating method. The casting method has a problem that refrigerated storage is necessary because the stability of polyamic acid is poor. Moreover, since a dehydration reaction occurs when cured, there are problems such as cracks, poor reliability, and low adhesion. Further, the sputtering method increases the cost because sputtering is performed in a vacuum. Moreover, since the polyimide surface is very smooth, there exists a problem that the adhesiveness between copper-polyimide is bad. Even in the plating method, there is a problem that the adhesion is poor as in the sputtering method.
[0007]
Further, in recent years, warping has become a problem particularly for FPCs used in applications such as hard disk drives. In order to eliminate this warpage, polyimide having a thermal expansion coefficient less than that of copper (20 ppm) may be used. However, the polyimide which can respond to these is limited, and generally there is a problem of poor adhesion.
[0008]
[Problems to be solved by the invention]
The present invention is intended to solve such problems, and an object of the present invention is a conductor laminate comprising a conductor layer and a polyimide layer, which has high electrical reliability and high flexibility. An object of the present invention is to provide a conductor laminate satisfying the above characteristics such as high heat resistance and high chemical resistance and particularly preferably with little warpage, and to provide a method for easily and inexpensively producing the conductor laminate. .
[0009]
[Means for Solving the Problems]
The present inventors have found that the above problems can be solved by using a ring-closed solvent-soluble polyimide having a carboxyl group for a conductor laminate, and have completed the present invention.
[0010]
Here, the conductor laminate of the present invention is a conductor laminate formed by laminating a conductor layer and a resin layer, and the resin layer is a ring-closing solvent-soluble polyimide layer having a carboxyl group. It is characterized by this.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below.
[0012]
Conductor The conductor used in the conductor laminate of the present invention is not particularly limited, and various metal foils such as aluminum and copper, for example, electrolytic copper foil and rolled copper can be used. The film thickness can be arbitrarily selected according to the application.
[0013]
Polyimide layer (resin layer)
The resin layer constituting the conductor laminate of the present invention is not particularly limited as long as it is a ring-closing solvent-soluble polyimide layer having a carboxyl group.
[0014]
In the present invention, the solvent-soluble polyimide means NMP, DMF, DMAc, γ-butyrolactone, DMSO, sulfolane and the like, preferably soluble in a solvent such as NMP. Such a soluble polyimide can form an electrodeposition coating, and preferably forms an electrodeposition solution containing such a polyimide and forms a polyimide layer by an electrodeposition method.
[0015]
Further, the ring-closed polyimide means a solvent-soluble polyimide in which an imide ring is already formed in a solution in the present invention.
[0016]
Furthermore, the polyimide having a carboxyl group means a polyimide in which an imide ring has already been formed in a solution and a carboxyl group different from an amic acid is introduced, and preferably, at least a part of a diamine component that is one raw material of the polyimide Can be obtained by containing diaminobenzoic acid. In this case, it is preferably a polyimide having an acid value of 10 to 200 mmol KOH / 100 g resin. Setting the acid value of the polyimide to 10 mmol / KOH or more is preferable for improving the dispersibility when preparing the electrodeposition paint and preventing the occurrence of precipitation, etc., and the acid value to 200 mmol / KOH or less. Is preferable in terms of reducing the water absorption after the polyimide layer is formed, improving the reliability under high temperature and high humidity, and improving the electrodeposition.
[0017]
Furthermore, in the present invention, the polyimide layer after formation is preferably an insulating resin layer that exhibits adhesiveness or adhesiveness at room temperature or by heating, and further preferably at a temperature of 450 to 550 ° C. for 1 hour. As described above, more preferably, heat treatment is performed at 450 to 500 ° C. for 1 to 2 hours. Thereby, generation | occurrence | production of the curvature of a conductor laminated body can be reduced.
[0018]
Furthermore, the polyimide used in the present invention may have a 10% thermal decomposition temperature of preferably 250 ° C. or higher, more preferably 350 ° C. or higher, and particularly preferably 450 ° C. or higher, depending on the application. A material having a high 10% thermal decomposition temperature is preferable from the viewpoint of improving the heat resistance of an electronic member such as a multilayer substrate. In a preferred embodiment of the present invention, when heat treatment at 450 ° C. or higher is performed, polyimide that can withstand the heat treatment temperature is used.
[0019]
The imidation ratio of the polyimide used in the present invention is preferably 85% or more, more preferably 90% or more, and particularly preferably 95% or more. When the imidization rate is 85% or less, there is a problem that the residual amic acid promotes migration of metal ions or the change with time of the polyimide solution becomes large.
[0020]
The weight average molecular weight of the polyimide used in the present invention is preferably 10,000 to 100,000. Especially preferably, it is 50000-80000. When the molecular weight is 10,000 or less, it is difficult to obtain a uniform coating film, and when it is 100,000 or more, gelation tends to occur.
[0021]
The molecular weight measurement can be performed by using, for example, a high-speed GPC device manufactured by Tosoh Corporation. The column that can be used here is TSKgelαM manufactured by Tosoh Corporation, and the solvent is DMF + 10 mmol phosphate buffer (PH 7.0) flow rate of 0.5 cm / min.
[0022]
The polyimide used in the present invention preferably contains a carboxyl group, and such a carboxyl group can be introduced in a required amount using diaminobenzoic acid or the like. The amount of diaminobenzoic acid in the diamine is preferably 10 to 200 mol%. If it is less than 10 mol%, the dispersibility deteriorates, and if it exceeds 200 mol%, the electrodeposition property deteriorates.
[0023]
(Acid dianhydride)
Although it does not specifically limit as acid dianhydride used for the synthesis | combination of the polyimide used for this invention, For example, specifically,
3,4,3 ′, 4′biphenyltetracarboxylic dianhydride 3,4,3 ′, 4′benzophenonetetracarboxylic dianhydride 2,3,3 ′, 4′biphenyl ether tetracarboxylic dianhydride 3 , 4,3 ′, 4′biphenylsulfonetetracarboxylic dianhydride bis (dicarboxylphenyl) propane dianhydride 4,4 ′-[2,2,2-trifluoro-1- (trifluoromethyl) ethylidene] Bis (1,2-benzenedicarboxylic acid dianhydride) (6FDA)
Bistrifluoromethylated pyromellitic acid,
Bis (dicarboxyphenyl) sulfone dianhydride bis (dicarboxyphenyl) ether dianhydride thiophenetetracarboxylic dianhydride pyromellitic dianhydride 1,2,5,6 naphthalene tetracarboxylic dianhydride 2,3 Aromatic acid dianhydrides such as 1,5,6-pyridinetetracarboxylic dianhydride 1,2,3,4-butanetetracarboxylic dianhydride cyclopentanetetracarboxylic dianhydride bicyclooctene tetracarboxylic acid bicyclo ( 2,2,2) -Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 5 (2,5-dioxotetrahydrofuryl) 3-methyl-3cyclohexene-1,2-dicarboxylic Examples thereof include aliphatic acid dianhydrides such as acid anhydrides. These are used singly or in combination of two or more kinds, but it is necessary to select one in which a combination of an acid dianhydride and an aromatic diamine becomes a solvent-soluble polyimide.
[0024]
(Diamine)
The diamine used in the polyimide used in the present invention is typically an aromatic diamine, and preferably includes 3,5 diaminobenzoic acid. Other aromatic diamines are not particularly limited. For example, specifically,
2,4 (or 2,5-) diaminotoluene 1,4 benzenediamine 1,3 benzenediamine 6-methyl 1,3-benzenediamine 4,4'-diamino-3,3'-dimethyl-1,1 ' -Biphenyl 4,4'-amino-3,3'-dimethoxy-1,1'-biphenyl 4,4'-methylenebis (benzeneamine)
4,4'-oxybis (benzeneamine)
3,4'-oxybis (benzeneamine)
3,3′-carboquinyl (benzeneamine)
4,4'-thiobis (benzeneamine)
4,4'-sulfonyl (benzeneamine)
3,3′-sulfonyl (benzeneamine)
1-methylethylidine 4,4′-bis (benzeneamine)
3,3′-dichloro-4,4′-diaminobiphenyl 3,3′-dinitro-4,4′-diaminobiphenyl 3,3′-diaminobenzophenone 1,5-diaminonaphthalene 1-trifluoromethyl 2,2, 2-trifluoroethylidine 4,4'-bis (benzeneamine)
1,1,1,3,3,3-hexafluoro-2-bis-4 (4-aminophenyl) propane 4,4′-diaminobenzanilide 2,6-diaminopyridine 4,4′-diamino-3, 3 ′, 5,5′-tetramethylbiphenyl 2,2bis (4 (4-aminophenoxy) phenyl) propanebis (4- (3-aminophenoxy) phenyl) sulfone bis (4- (4-aminophenoxy) phenyl) Sulfonebis (4- (4-aminophenoxy) phenyl) ethyl 1,4-bis (4-aminophenoxy) benzene 1,3bis (3-aminophenoxy) benzene 9,9′-bis (4-aminophenyl) fluorenebenzidine -3,3-dicarboxylic acid 4,4 '-(or 3,4'-, 3,3'-, 2,4'-) diamino-biphenyl ether diaminosilane compound It can be mentioned. Although these can be used alone or in combination of two or more, it is necessary to select a polyimide composition in which a combination of an acid dianhydride and an aromatic diamine is a solvent-soluble polyimide.
[0025]
Method for manufacturing conductor laminate The method for manufacturing a conductor laminate according to the present invention includes a first step of forming a conductor layer and then a ring-closed type having a carboxyl group as described above on the conductor layer. It is characterized by forming a solvent-soluble polyimide layer.
[0026]
As a method of coating polyimide on the conductor layer, which is preferably copper, there are several existing methods such as die coating method, curtain coating method, and electrodeposition method, and there is no particular limitation. From the viewpoint of easy control, the electrodeposition method is desirable.
[0027]
The electrodeposition method can be performed, for example, by immersing a copper foil and a counter electrode in an electrodeposition paint, applying a DC voltage, and forming an electrodeposition coating film on copper. At that time, the film thickness can be arbitrarily controlled by the voltage to be applied and the application time. In this electrodeposition, a mask is usually provided on the surface opposite to the surface on which the copper polyimide is electrodeposited, and the polyimide is not electrodeposited on the masked surface. After the electrodeposition of polyimide, the mask is peeled off, dried and cured by heat. At that time, in order to reduce the thermal expansion coefficient of the polyimide and eliminate the warpage of the substrate, it is preferable to perform the heat treatment at a high temperature as described above. By such a manufacturing method, a conductor laminate can be obtained at low cost, with high reliability, and without warping.
[0028]
【Example】
Hereinafter, details of the present invention will be described based on examples.
[0029]
(Manufacture of polyimide electrodeposition solution)
Usually, polyimide is synthesized by dehydration condensation polymerization reaction of acid dianhydride and diamine. At that time, polyimide is produced in a form through a polyamic acid. However, this reaction is an equilibrium reaction, and reactions in both directions from polyamic acid to polyimide and from polyimide to polyamic acid occur simultaneously. For this reason, the polyimide which passed the polyamic acid will be in a random state, and will not become a block copolymer. In general, it is said that a random copolymer is inferior in physical and chemical properties to a block copolymer and an alternating copolymer. Therefore, in this invention, the method of manufacturing the polyimide which consists of a block copolymer was employ | adopted by the method of performing an imidation in one step, using an acid catalyst and removing dehydrated water one by one.
[0030]
A 10-liter three-necked separable flask was equipped with a stainless steel squid stirrer, a nitrogen condenser and a reflux condenser with a ball condenser on a trap with a stopcock. While flowing a nitrogen stream, a separable flask was attached to a silicone bath equipped with a temperature controller and heated. The reaction temperature is indicated by bath temperature.
[0031]
3,4,3'4'-benzophenonetetracarboxylic dianhydride (hereinafter referred to as BDTA) 322.2 g (1 mol), bis (4- (3-aminophenoxy) phenyl) sulfone (m-BAPS) 216 .3 g (0.5 mol), valerolactone 15 g (0.15 mol), pyridine 24 g (0.3 mol), NMP (abbreviation of N-methyl-2-pyrrolidone) 2000 g, toluene 300 g, and adding silicon through nitrogen The mixture was stirred at 200 rpm in a bath at room temperature for 30 minutes, then heated to 180 ° C. and reacted for 1 hour with stirring at 200 rpm. Remove 150 ml of toluene-water distillate, air-cool, add BDTA 61.1 g (0.5 mol), 3,5 diaminobenzoic acid (hereinafter referred to as DABz) 152.16 g (1 mol), NMP 1190 g, toluene 300 g After stirring and stirring at 200 rpm for 30 minutes at room temperature, the temperature was then raised to 180 ° C., and the reaction was terminated by heating and stirring for 3 hours. A 20% polyimide varnish was obtained. The acid equivalent (the amount of polymer per COOH was 1554) was 70.
[0032]
1000 g of 20% polyimide varnish, 1500 g of 3SN (mixed solution of NMP: tetrahydrothiophene-1,1-dioxide = 1: 3 (weight)), 750 g of benzyl alcohol, 50 g of methylmorpholine (neutralization rate 200%), 300 g of water An aqueous electrodeposition solution was prepared by stirring. The obtained aqueous electrodeposition solution was a polyimide 7.4%, pH 7.8, dark reddish brown transparent solution.
[0033]
(Formation of polyimide layer)
The copper foil with the mask on the back was immersed in the above electrodeposition solution, and the electrodeposition was performed by changing the voltage application time from 3 to 15 minutes at an applied voltage of 150V. The masking tape on the back of the copper foil was peeled off and dried on a hot plate at 150 ° C. for 3 minutes. Heat curing was performed at 450 ° C. for 60 minutes to obtain a conductor laminate.
[0034]
The obtained polyimide-copper foil was baked under a nitrogen atmosphere while changing the heat treatment conditions as follows.
[0035]
The obtained copper foil-polyimide was etched using a ferric chloride 40 baume at 60 ° C. to obtain polyimide films having different heat treatment conditions. The polyimide film was cut into a width of 5 mm and a length of 1.5 cm, and the thermal expansion coefficient of the film was determined using TMA7 manufactured by PerkinElmer. The tensile load at the time of measuring the thermal expansion coefficient was measured at 10 mN. Further, a conductor laminate was actually formed and the occurrence of warpage was observed. The observation results of each heat treatment condition, linear expansion coefficient and warpage are shown.
Heat treatment conditions Linear expansion coefficient (× 10 ^-5 / K) Warpage occurrence
300 ° C 1 hour 58 Warp 350 ° C 1 hour 56 Warp 350 ° C 8 hours 59 Warp 400 ° C 1 hour 58 Warp 400 ° C 2 hours 51 Warp 450 ° C 5 minutes 73 Warp 450 ° C 30 minutes 68 Warp 450 ℃ 1 hour 24 No warping
500 ° C 1 hour 23 No warpage
From this result, it was confirmed that the linear expansion coefficient decreased under the heat treatment conditions of 450 ° C. for 1 hour and 500 ° C. for 1 hour. Moreover, it was confirmed that the conductor laminated body without a curvature can be obtained by heat-processing for 1 hour or more at the temperature of 450-500 degreeC.
[0036]
When the insulation resistance was measured for this conductor laminate in a constant temperature and humidity chamber of 85 ° C. and 85% RH by applying a DC voltage, it was possible to retain the insulation for 3 hours at a thickness of 3 μm.
[0037]
【The invention's effect】
According to the present invention, it is possible to provide a conductor laminate that satisfies characteristics such as high electrical reliability, high flexibility, high heat resistance, and high chemical resistance and particularly preferably has little warpage. Furthermore, according to the method of the present invention, such a conductor laminate can be manufactured easily and at low cost.

Claims (6)

A conductor laminate in which a conductor layer and a resin layer are laminated, wherein the resin layer is a ring-closing solvent-soluble polyimide layer having a carboxyl group,
The polyimide layer is a polyimide that is a reaction product of a tetracarboxylic dianhydride and a diamine, and at least a part of the diamine component contains diaminobenzoic acid, and has an acid value of 10 to 200 mmol KOH / 100 g resin. A conductor laminate formed by an electrodeposition method using an electrodeposition solution containing a certain polyimide and subjected to a heat treatment at a temperature of 450 to 500 ° C. for 1 hour or longer.   The conductor laminate according to claim 1, wherein the polyimide is a solvent-soluble type before curing and forms an insulating resin layer exhibiting adhesiveness or adhesiveness at room temperature or by heating.   The conductor laminate according to claim 1, wherein the conductor is copper. A method for producing a conductor laminate in which a conductor layer and a resin layer are laminated, wherein a ring-closing solvent-soluble polyimide layer having a carboxyl group is formed on the conductor layer after the conductor layer is formed. Forming an electrodeposition method using an electrodeposition solution containing, and subjecting the polyimide layer to a heat treatment at a temperature of 450 to 500 ° C. for 1 hour or more ,
The polyimide is a polyimide that is a reaction product of tetracarboxylic dianhydride and a diamine, and at least a part of the diamine component contains diaminobenzoic acid, and has an acid value of 10 to 200 mmol KOH / 100 g resin. , wherein the method for producing a conductive laminate. The manufacturing method of the conductor laminated body of Claim 4 in which the said polyimide is a solvent soluble type before hardening, and forms the insulating resin layer which shows adhesiveness or adhesiveness by normal temperature or a heating. The manufacturing method of the conductor laminated body of Claim 4 whose said conductor is copper.