JPH0758824B2 - Wiring board - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board useful for a printed wiring board, a hybrid IC, and the like, and more specifically, a heat dissipation measure associated with high-density mounting and mounting of a heat generating device. And a wiring board particularly useful for forming a high frequency circuit.

Conventional technology and its problems In printed wiring boards and wiring boards such as hybrid ICs, heat dissipation is a major problem due to high-density mounting of electronic circuits and mounting of heat-generating devices. As one of the countermeasures, a substrate (commonly referred to as a metal core substrate) in which a metal is used as a core material and which is coated with resin or enamel and which utilizes good thermal conductivity of metal is being put into practical use. Among these conventional metal core substrates, the resin coated type has poor heat resistance, and it is difficult to prevent corrosion of the end faces during external processing, and it is difficult to establish continuity on both sides. When the resin is applied by a general method after the outer shape processing or the through hole is formed, there is a problem that the wall of the through hole cannot be reliably insulated. Further, the enamel-covered metal core substrate has a drawback that it is not suitable for a high frequency circuit because of its low productivity and high permittivity, and it is difficult to cope with the reduction of the diameter of the conduction hole.

Also, in the hybrid IC field, alumina substrates are mainly used, but higher heat dissipation is desired, and when double-sided boards are used, holes are made at the green sheet stage before firing the alumina substrates. There remain various problems to be solved, such as a problem in the positional accuracy of the conductive holes due to shrinkage during firing, and improvement in high frequency characteristics.

Incidentally, Japanese Patent Publication No. 55-24716 discloses a method of performing electrophoresis in an organic solvent, but the structure of the polyamic acid used is not limited at all. Therefore, of course, since it uses an organic solvent, it is not preferable in industrialization from the viewpoint of fire and the environment, but the inventors of the present invention have examined it, and it is completely satisfactory if a mere polyamic acid is used. It was found that the adhesiveness was not obtained, which was a practical problem.

Object of the Invention An object of the present invention is to overcome the drawbacks of the prior art described above, and to realize insulation of a small-diameter conductive wall having excellent heat resistance and dielectric constant, and high reliability, and preventing corrosion of the end surface of the substrate. The present invention is to provide a novel heat-dissipating wiring board using as a core material, and to provide a printed wiring board and a hybrid IC board having excellent performance.

DETAILED DESCRIPTION OF THE INVENTION The present invention has the general formula (Here, R ₁ is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or an aromatic group which is directly or crosslinked with each other. Represents a tetravalent group selected from the group consisting of non-fused polycyclic aromatic groups, R
₂ has a bond at the meta position selected from the group below
Represents a valent aromatic group. ) The carboxyl group of the polyamic acid consisting of the repeating unit represented by is neutralized with a base and diluted with water to form an electrophoretic bath for forming a film, and a metal plate on which a film is to be formed is immersed in the bath.
Electrophoresis is performed using the metal plate as an anode to deposit the polyamic acid on the surface of the metal plate to form a film, and then heat treatment is performed to imidize the film to form a polyimide insulating layer. The present invention resides in a wiring substrate.

Hereinafter, the present invention will be described in detail.

The general formula described above is used in the present invention. It is a specific polyamic acid having a repeating unit represented by: The production method is not particularly limited, but usually, it can be produced by polymerizing various corresponding diamines with tetracarboxylic dianhydride in an organic solvent.

Examples of the diamine used in the present invention include 3,3'-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene and 4,4'-bis (3-aminophenoxy).
Biphenyl, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfone and the like in the meta position. Diamines may be used, and these may be used alone or in admixture of two or more.

The tetracarboxylic dianhydride to be reacted with the diamine in the present invention has the following formula (In the formula, R ₁ is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group,
Represents 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 aromatic groups are connected to each other directly or by a bridging member. ), For example, ethylene tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2 ', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2 ', 3,3'-biphenyletracarboxylic acid Dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxy) Phenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1- Screw (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-naphthalene Tetracarboxylic acid dianhydride, 1,2,3,4-benzenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarumbonic acid dianhydride, 2,3,6,7-anthracene tetra Carboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like are preferable. Of these, particularly preferred tetracarboxylic dianhydride,
Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and bis (3,4- Dicarboxyphenyl) ether dianhydride.

The reaction for producing a polyamic acid from the above-mentioned diamine and tetracarboxylic dianhydride is usually carried out in an organic solvent. Examples of the organic solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N, N-
Diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, pyridine, dimethyl sulfone, hexamethylphosphoramide, tetramethylurea, N-methylcaprolactam, tetrahydrofuran,
m-dioxane, p-dioxane, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, bis [2- (2-
Methoxyethoxy) ethyl] ether and the like.
These organic solvents may be used alone or in combination of two or more. The reaction temperature is usually about 200 ° C. or lower and −20 ° C. or higher, preferably 50 ° C. or lower and −10 ° C. or higher, and more preferably about 0 ° C. or higher and about room temperature. The reaction pressure is not particularly limited and can be carried out at normal pressure. The reaction time depends on the type of solvent,
Although it may vary depending on the reaction temperature and the diamine or dianhydride used, it is usually 2 to 40 hours, preferably 4 to 24 hours for the reaction to be carried out for a sufficient time to complete the production of polyamic acid.
Time is enough.

The polyamic acid solution of the present invention thus obtained is a solution containing a polyamic acid in an amount of 5 to 40% by weight, particularly preferably 10 to 30% by weight, and a logarithmic viscosity of 0.5 to 4 dl / g (35 ° C, a concentration of 0.
(Value measured with 5 g / ml N, N-dimethylacetamide) Particularly preferably, 0.6 to 2.5 dl / g is preferable since it has excellent water-solubility described later and physical properties of the polyimide film after heat treatment.

In the present invention, the above-mentioned polyamic acid can be diluted with water by adding a base to the solid resin obtained by precipitating and precipitating it from the solution to neutralize its carboxyl group.

The base used for the neutralization is ammonia; secondary amines such as dialkylamine, diethanolamine, morpholine; triethylamine, tributylamine, triethanolamine, triisopropanolamine, dimethylethanolamine, dimethylisopropanolamine, diethylethanolamine. , Tertiary amines such as dimethylbenzylamine; inorganic bases such as caustic soda and caustic potash are used, and the tertiary amines are particularly preferable from the viewpoint of stability after dilution with water and properties of the coating film obtained.

The amount of base required for imparting water-dilutability is generally 30 to 110 mol% and particularly preferably 40 to 100 mol% based on the carboxyl equivalent of the polyamic acid to be neutralized. By carrying out the neutralization in this way, the polyamic acid becomes completely water-soluble or partially becomes water-soluble to be in a suspended state and becomes water-dilutable. In either case, the polyamic acid is neutralized, and by diluting it with water to a resin concentration of the following degree, a polyamic acid aqueous solution that can be electrophoresed to form an electrophoretic bath for forming a film. You can do it.

A metal plate on which a film is to be formed is immersed in an electrophoretic bath (hereinafter, simply referred to as a bath) composed of the thus obtained polyamic acid aqueous solution, and an electrophoretic treatment is performed using the metal plate as an anode.

At this time, a filler such as alumina, boron nitride, silicon nitride, or aluminum nitride may be added to the bath.
The resin concentration of the bath is usually 2 to 30% by weight, more preferably 3
~ 20% by weight. The electrophoretic treatment as described above is performed by immersing a metal plate serving as a core material of the present invention in a bath, using the metal plate as an anode, and a bath wall or an opposing electrode of an inert metal as a cathode, usually at 10 to 300 V. It is performed by applying a voltage. The film-forming component of the neutralized polyamic acid salt dispersed in water is usually negatively charged, moves to the metal plate that is the anode, loses the charge on the surface of the metal plate, and precipitates to form the metal plate. The polyamic acid resin film is formed on the surface.

In the present invention, as the material of the metal plate serving as the core material of the substrate, various metals such as aluminum, iron, copper, silicon steel plate, chromate steel plate, galvanized steel plate are used, and these materials are, of course, flat plates. However, the holes for electrical conduction and component mounting may be pre-drilled, and in this case, the advantage of the coating by electrophoresis described above is particularly great.
Further, the metal plate may be externally processed into a desired shape, and in this case, the rust prevention of the end face is surely performed, which is particularly preferable.

In the present invention, the coated metal plate on which the coating film pulled up from the bath is formed, is usually subjected to water washing (since the resin film has already been insolubilized in water, the polyamic acid is not detached from the metal plate), usually 100 ~ 380 ° C, preferably 18
At a temperature of 0 to 350 ° C, the required time, usually 10 minutes to 15 hours,
The polyamic acid forming the coating is imidized by heat treatment for preferably 15 minutes to 10 hours, more preferably 30 minutes to 8 hours, whereby the extremely strong insulating layer of the polyimide resin coating is applied to the metal surface. To form. In the heat treatment, it is not preferable to rapidly raise the temperature because firing or the like is involved, and it is preferable to raise the temperature gradually or stepwise.
An ordinary dryer can be used as an apparatus for performing the heat treatment, and for example, a hot air dryer, a far infrared dryer, or the like can be preferably used at normal pressure or reduced pressure.

The thickness of the imide film formed on the surface of the metal plate is usually 2 to 60
It is about μ, and preferably about 5 to 40 μ.

The thus obtained wiring board of the present invention is used as a wiring board by forming a conductor circuit or a resistance printed circuit as necessary on the board, and various known methods per se are used for forming these circuits. Applied. For example, the above wiring board is subjected to a pretreatment for imparting plating acceptability as necessary, and after coating the non-circuit portion with a resist material, electroless plating,
Further, a method of forming a circuit by electrolytic plating if necessary, or a method of printing a conductive paste and a resistance paste by a screen printing method and heating and drying to form a circuit is generally used. In the plating method, the holes are also plated on the wall of the hole at the same time, so it is possible to electrically connect double-sided circuits. Also, in the screen printing method, a conductive paste is embedded in the holes to electrically connect the circuits on both sides. It is possible to

The wiring board of the present invention obtained as described above is excellent in heat resistance and dielectric characteristics, and more reliable circuit connection on both sides is possible, and corrosion does not occur even if the end surface treatment of the board is not performed. It is a very useful heat dissipation wiring board, and its industrial applicability is extremely large.

Examples and Embodiments Hereinafter, embodiments of the present invention will be described with reference to Examples.

The logarithmic viscosity in the examples is a value measured at 35 ° C. with 0.5 g / 100 ml N, N-dimethylacetamide. The characteristic evaluations shown in Examples and Comparative Examples were performed according to the following methods.

(A) Adhesiveness When the circuit is formed by plating, JIS-C-6481 5.7
The peeling strength is in accordance with the above, and when the circuit is formed by the conductive paste, it is the result of the gooseneck tape test in accordance with JIS-Z-5400 6.1.

(B) Withstand voltage In accordance with JIS-C-2110, it was judged whether or not the AC voltage was 1 KV.

(C) Dielectric constant According to JIS-C-6481 5.12, the dielectric constant at 1 KHz of the insulating layer formed by electrodeposition between the conductive pattern formed on the insulating layer and the metal as the core material was measured. .

(D) Solder heat resistance It was floated on solder at 260 ° C for 180 seconds and visually checked for blisters and peeling.

Example-1 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
53.0 g (0.25 mol) of 3'-diaminobenzophenone was added to N, N
It was dissolved in 240 ml of -0 dimethylacetamide. Powder of 78.6 g (0.244 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride was added to this solution, and the mixture was stirred at 10 ° C. for 24 hours to obtain a polyamic acid solution. The polyamic acid thus obtained had an inherent viscosity of 0.6 dl / g. To this polyamic acid solution was gradually added 39.1 g of dimethylethanolamine (90 mol% relative to carboxyl equivalent) and stirred for 20 minutes at room temperature,
905.3 g of water was gradually added with stirring at room temperature and diluted with water to prepare a polyamic acid solution (resin concentration 10% by weight). This aqueous solution is placed in a plastic bath to form an electrophoretic bath for film formation, the aluminum plate to be coated is immersed as the anode, the lead plate is immersed as the cathode, and a voltage of 100 V is applied for 10 minutes for electrophoresis. went. After that, the aluminum plate was taken out, washed with water, and dried and imidized by heating at 150 ° C. for 2 hours and 280 ° C. for 2 hours. The thickness of the polyimide acid resin coating after the heat treatment was 24μ. This was used as a test piece, and the test piece was subjected to electroless copper plating and electrolytic copper plating. The thickness of the copper plating was 30 μm. The result of the adhesion test was 1.8 Kg / cm, the withstand voltage and the solder heat resistance were also pass, and the dielectric constant was 3.3. Furthermore, this test plate is 300 ℃
It was confirmed that the same result was obtained when the same test was performed after high temperature exposure for 240 hours.

Example 2 A container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube was used for 2,2
-Bis [4- (3-aminophenoxy) phenyl] propane 41.0 g (0.1 mol) and N, N-dimethylacetamide 2
00 ml was charged, the mixture was cooled to around 0 ° C., 21.8 g (0.1 mol) of pyromellitic dianhydride powder was added under a nitrogen atmosphere, and the mixture was stirred at around 0 ° C. for 2 hours. Next, the solution was returned to room temperature and stirred under a nitrogen atmosphere for about 20 hours. The polyamic acid solution thus obtained had an inherent viscosity of 1.5 dl / g. Triethylamine 2 in this polyamic acid solution
Slowly add 0.2g (100mol% of carboxyl equivalent) to 1
After stirring at room temperature for an hour, 973 g of water was gradually added with stirring to dilute the polyamic acid aqueous solution (resin concentration 5% by weight). This aqueous solution was placed in a stainless steel bath to form an electrophoretic bath for film formation, the galvanized steel sheet to be coated was immersed as an anode, and the bath was used as a cathode to apply a voltage of 150 V for 5 minutes for electrophoresis. Then, the galvanized steel sheet was taken out, washed with water, and then imidized by heating at 120 ° C. for 1 hour, 180 ° C. for 2 hours, and 280 ° C. for 2 hours. The thickness of the polyimide acid resin film after the heat treatment was 20μ. Using this as a test piece, MSP-1 as a conductive paste on the test piece
Circuits were formed by screen printing using 00 and MCP-1606 (both manufactured by Mitsui Toatsu Chemicals, Inc.) and the paste was cured at 150 ° C. The results of the adhesion test were 100/100 for both pastes, and the withstand voltage and solder heat resistance were also good. The dielectric constant was 3.1. Further, it was confirmed that the same result was obtained by subjecting the test plate to high temperature exposure at 300 ° C. for 240 hours and performing the same test.

Example 3 In a container equipped with a stirrer, a reflux condenser and a nitrogen introducing tube, 2,
2-bis [4- (3-aminophenoxy) phenyl] propane 41.0 g (0.1 mol) and N, N-dimethylacetamide 219.6 g were added, and at room temperature under a nitrogen atmosphere, 3,3 ′, 4,
4'-benzophenone tetracarboxylic acid dianhydride 31.6 g
(0.098 mol) was added as a dry solid little by little while paying attention to the rise in solution temperature, and the mixture was reacted at room temperature for 23 hours. The polyamic acid thus obtained had an inherent viscosity of 0.70 dl / g. Triethanolamine 1 in this polyamic acid solution
Slowly add 4.6 g (50 mol% of carboxyl equivalent) to 2
The mixture was stirred at 40 ° C. for an hour, and 177.2 g of water was gradually added while stirring to prepare a polyamic acid aqueous solution (resin concentration 15% by weight). Using this aqueous solution, a diameter of 0.4
200V5 with aluminum plate with ~ 3.0mm hole as anode
Electrophoresis was performed for a minute. After washing with water, 150 ℃ for 1 hour, then 260
Dry imidation was carried out by heat treatment at 2 ° C. for 2 hours. The thickness of the polyimide resin coating after heat treatment is 25μ, and
The thickness of the insulating layer on the inner wall of the hole was also the same from the measurement of the cross section. This test piece was plated with 33 μm of copper in the same manner as in Example-1. The result of the adhesion test in the state of the plating layer is 2.
It was 0 kg / cm, and the withstand voltage and solder heat resistance were also good.
Furthermore, this test plate was exposed to a high temperature of 300 ° C. for 240 hours and subjected to the same test, and the same result was obtained, and no voids or cracks were found by the cross-section measurement of the hole after plating. .

Comparative Example-1 The 2,2-bis [4- (3-aminophenoxy) phenyl] propane obtained in Example-3 was replaced with 2,2-bis [4- (4-
By the same procedure as in Example 3 except that aminophenoxy) phenyl] propane was used, 1.16 dl / g of polyamic acid was obtained. Neutralization, water solubilization, electrodeposition, washing with water and dry imidization were carried out in the same manner as in Example-3 to obtain a polyimide-coated aluminum plate. The thickness of the polyimide resin coating was 23μ. Copper plating was performed in the same manner as in Example-1. The withstand voltage in the normal state was pass, but the result of the adhesion test was 0.
It was a remarkably low value of 4 kg / cm, and blistering occurred in the solder heat resistance test. Furthermore, this test plate was exposed to a high temperature of 300 ° C. for 240 hours, and the same test was performed. As a result, the withstand voltage passed, the adhesion test was 0.2 kg / cm, and blisters were generated in the solder heat resistance test.

As described above, unlike the present invention, there is no bond at the meta position,
It was shown that the one using the para-position diamine had extremely poor adhesion.

Comparative Example-2 All the examples except that 12.8 g (0.1 mol) of 4,4'diaminodiphenyl ether was used in place of 2,2-bis [4- (3-aminophenoxy) phenyl] propane in Example-3.
By the same operation as in 3, 1.25 dl / g of polyamic acid was obtained. Neutralization, water solubilization, electrodeposition, washing with water and dry imidization were carried out in the same manner as in Example-3 to obtain a polyimide-coated aluminum plate. The thickness of the polyimide resin coating was 25μ.
Copper plating was performed in the same manner as in Example-1. The withstand voltage in the normal state was pass, but the result of the adhesion test was 0.2 Kg / cm.
Markedly low, and blistering occurred in the solder heat resistance test. Furthermore, this test plate was exposed to a high temperature of 300 ° C. for 240 hours, and the same test was conducted. As a result, the withstand voltage passed, the adhesion test was 0.1 Kg / cm, and blistering occurred in the solder heat resistance test.

As described above, unlike the present invention, there is no bond at the meta position,
It was shown that the one using the para-position diamine had extremely poor adhesion.

Examples 4 to 19 Type and amount of diamine, amount of N, N-dimethylacetamide, type and amount of tetracarboxylic dianhydride The same operation as in Example-1 was carried out except that the amount of dimethylethanolamine used for neutralization and the amount of water used for dilution were changed, and the results shown in Table-1 were obtained. The amount of dimethylethanolamine used for neutralization is the equivalent of carboxyl.
The amount of water used for dilution shall be calculated so that the resin concentration will be 10% by weight. In the table, PMDA is pyromellitic dianhydride, BTDA is 3,3 ',
4,4'-benzophenone tetracarboxylic dianhydride, ODP
A is bis (3,4-dicarboxyphenyl) ether dianhydride, and BPDA is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride.

Claims (1)

[Claims] 1. A general formula (Here, R ₁ is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or an aromatic group which is directly or crosslinked with each other. Represents a tetravalent group selected from the group consisting of non-fused polycyclic aromatic groups, R
₂ represents a divalent aromatic group selected from the following group. ) The carboxyl group of the polyamic acid consisting of the repeating unit represented by is neutralized with a base and diluted with water to form an electrophoretic bath for forming a film, and a metal plate on which a film is to be formed is immersed in the bath.
Electrophoresis is performed using the metal plate as an anode to deposit the polyamic acid on the surface of the metal plate to form a film, and then heat treatment is performed to imidize the film to form a polyimide insulating layer. A wiring board characterized by the above.