JP3400236B2 - Thermosetting carbon-based conductive paint - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] The present invention relates to a printed circuit board.
Thermosetting carbon-based conductive coating to form printed conductive circuit on board
It is about fees. 2. Description of the Related Art Paper phenol laminates and polyester fiber
Conductive paints that form circuits by printing on substrates such as
Conductive particles such as metal or carbonaceous powder and heat as a binder
Main component is curable resin and organic solvent as coating solvent
The conductive particles are dispersed in an organic solvent using a dispersant.
I'm making it. For example, Japanese Patent Publication No. 60-58268 discloses
Copper powder, thermosetting resin, unsaturated fatty acid and organic titanium compound
A conductive copper paste made of a material is disclosed. However, conductive coatings for printed circuit boards
As for the cost, from the viewpoint of cost and migration, copper
Carbonaceous powder than paint using metallic conductive particles of silver or silver
The carbon-based paint used is often used. sand
That is, as conductive particles, noble metals such as silver and copper and gold of base metals
Carbonaceous materials such as graphite and carbon black
Powder is cheaper and uses copper conductive paint.
Printed circuit boards, because copper is easily oxidized,
Special oxidation protection for formed copper printed conductive circuit coatings
Processing needs to be performed. Also, with electrochemical metal corrosion
Silver with a remarkable migration as metal powder
Printed circuit board, formed silver printed conductive circuit
Keep moisture and halogen substances away from the
Use of metallic conductive particles, such as the need to form a protective coating
In the case of paints that have been
The cost of the circuit board increases. In recent years, carbon-based conductive paints have
However, the resistance of the printed conductive circuit film to be formed has been reduced.
And the sheet resistance value representing the conductivity of this type of coating is 3
Paints of about 0 to 50 Ω / □ are commercially available. like this
Carbon conductive paints include graphite and carbon black
Conductive particles made of carbonaceous powder and thermosetting resin
Butyl resin in a ratio of 1 to 1.5: 1.
Losolve, butyl carbitol, butyl carbitol
Dissolves ethylene glycol-based organic solvents such as acetate
Used as a medium, in which conductive particles of carbonaceous powder are dispersed
It is. Screen-print this paint on the printed circuit board
Printing at a temperature of 160 ° C or less to prevent substrate deterioration.
Conduct a thermosetting treatment for 5 to 30 minutes and print conductive circuit on the substrate
Is formed. [0005] Subsequent substrate manufacturing steps include soldering.
And hot water cleaning treatments.
During these steps, a large voltage of about ± 20 to 100%
A change in the air resistance value causes a change in the electric resistance value at the time of circuit design.
There is a problem of not being satisfied. This is a printed conductive circuit
Cracking, shrinkage, and conduction inside the coating
Changes in particle distribution or formation of coatings on printed conductive circuits
Phenomena such as denaturation of materials that work complexly
It is. SUMMARY OF THE INVENTION [0006] The present invention solves the above problems.
To solve the problem, we need to improve the composition of the paint material.
Printed conductive circuit cover formed from more carbon-based conductive paint
It is intended to suppress a change in the electric resistance value of the film. [0007] The thermosetting car of the present invention
Bon-based conductive paint is made of resole type phenol resin, polyvinyl chloride
Titanium consisting of nilbutyral and organotitanium compounds
In a solution of a catenate coupling agent dissolved in a paint solvent
In addition, carbonaceous powder of graphite and carbon black is used as conductive particles.
In the thermosetting carbon-based conductive paint dispersed by
(A) 12 to 18% by weight of the graphite and carbon black
30% by weight of carbonaceous powder consisting of 12-18% by weight
25 to 30% by weight of the resole type phenol resin,
0.6 to 1.8% by weight of a vinyl butyral resin, the organic
Titanate-based coupling agent composed of a titanium compound
7-2.5% by weight, and butyl cellosolve, butyl
From carbitol and butyl carbitol acetate
Paint solution consisting of selected single or mixed organic solvents
In this configuration, the medium is contained as the remaining amount. Furthermore, (b) before
Of the resol type phenolic resin at 180 ° C
Amount of free phenol per minute is resol type phenol resin
(C) the carbonaceous powder
Is a natural phosphorous or flaky graphite particle
The average particle diameter is 10 to 30 μm,
(D) The polyvinyl butyral resin has a degree of polymerization of 10
Containing in the range of 00 to 1800 at least 60% by weight
It is characterized by having. [0008] The present invention is achieved by the above configuration.
That is, as graphite particles of carbonaceous powder that is conductive particles
Is a natural phosphorous or scaly
Can be used to obtain printed conductive circuit coatings with low electrical resistance.
Is preferred. Is natural graphite different in crystallinity?
Are classified into scaly, phosphorous and earthy graphite.
Natural graphite suitable for the invention of No. 1 has the highest crystallinity of true graphite.
Near flaky graphite, followed by phosphite graphite with high crystallinity
It is. The average particle size of the graphite particles is 10 to 30 μm.
A range is preferred. When the average particle size is less than 10 μm
Of the printed conductive circuit
The electrical resistance of the film increases. Get more printed conductive circuits
The temperature of the thermosetting treatment to be performed is higher than 150 ° C.
And the rate of change of the electrical resistance value increases. This is the grain in the coating
The child is in a filling state where movement is likely to occur.
You. When the average particle diameter of the graphite particles exceeds 30 μm,
Also, the filling rate of the conductive particles in the printed conductive circuit coating is lower.
As a result, the electrical resistance of the conductive coating increases, and the electrical resistance changes.
Conversion rate increases. In addition, this type of conductive paint is mainly
And transfer it to the substrate to be printed by screen printing method,
Heat-cured to form a printed conductive circuit film.
Prevents clogging of screen mesh used for lean printing
From the viewpoint of stopping, the maximum particle size of graphite particles
90 μm or less, which is smaller than the opening diameter of the lean mesh
It is necessary to [0009] Carbon black particles are finer than graphite particles.
Because graphite particles are used as conductive particles of carbonaceous powder
In comparison with the case of a single graphite particle,
The electrical resistance of the resulting printed conductive film with improved packing
Decrease. Among several types of carbon black, conductive paint
Preferred is acetylene black for conductivity. black
The compounding weight ratio of lead to carbon black is
Carbon black = 40/60 to 60/40 is preferred.
That is, when the amount of conductive particles in the paint is 30% by weight,
Indicates that the amount of graphite particles is 12 to 18% by weight,
The amount of particles is 12 to 18% by weight. This mixing ratio is
The average particle size of the graphite particles is determined from the packing state of the aforementioned particles.
When the particle diameter is coarse and about 30 μm,
Due to the large intergranular volume, it is necessary to fill
The amount of carbon black increases. On the other hand, graphite particles
When the average particle size is as small as about 10 μm, the graphite particle phase
Necessary to fill the space between grains because the volume between grains is small
Less carbon black. The graphite particles
When the average particle size of
When mixed in a large amount, the contact resistance between particles increases,
Causes an increase in the value. [0010] The dispersed state of the conductive particles in the paint is obtained.
Close relationship with the rate of change of electrical resistance of printed conductive circuit coating
Yes, the better the dispersion state of the conductive particles in the paint,
The rate of change of the electric resistance value decreases. Dispersion state of conductive particles
In order to improve the polyvinyl butyral (hereinafter referred to as
"PVB") resin and organic titanium compound.
It is desirable to use a titanate coupling agent
No. These materials are also obtained by heat-curing paint.
Can impart flexibility to the coating of a printed conductive circuit
Therefore, the stress due to thermal shock is reduced, and the electrical resistance changes.
Is shown. Formulation of PVB resin
The amount is preferably 2 to 6% by weight based on the conductive particles of the carbonaceous powder.
And preferably 3-5% by weight, more preferably 4% by weight.
% By weight. These values indicate that the amount of conductive particles in the paint is 3
When expressed as the composition of the entire coating as 0% by weight,
0.6-1.8% by weight, 0.9-1.5% by weight and 1.
It becomes 2% by weight. PVB resin is doubled based on the amount of conductive particles
If the amount is less than%, the electric resistance value of the obtained printed conductive circuit film
And the rate of change of the electric resistance value is also large. This is a paint
The dispersion state of the conductive particles in the material is poor,
The required flexibility of the printed conductive circuit coating
Because there is not. Conversely, even if it exceeds 6% by weight, it can be obtained.
The electrical resistance of the printed conductive circuit film is high and the electrical resistance changes.
Conversion rate increases. This is the conversion of resin to carbonaceous conductive particles.
The coating amount is large and thermoplastic such as PVB resin
The effect of thermal denaturation, a characteristic of the conductive resin, cannot be ignored.
It is due to. [0011] PVB resin is a thermoplastic synthetic resin,
Graded according to the difference in molecular weight, ie degree of polymerization
It is commercially available. PVB compounded in the conductive paint of the present invention
As the resin, a single resin having a certain degree of polymerization may be used.
By mixing PVB resins with different degrees of polymerization as appropriate
May be used, but those having a polymerization degree of 1000 to 1800
At least 60% by weight or more of the entire PVB resin.
Is preferred. Uses low molecular weight PVB resin
And the amount of conductive particles of carbonaceous powder coated
As a result, the electrical resistance of the printed printed circuit
You. Also, the lower the molecular weight of the thermoplastic resin, the more heat-denatured.
Because of the ease, the rate of change of the electric resistance value also increases. High molecular weight
When PVB resin is used, conductive particles of carbonaceous powder,
The dispersed state of the graphite particles deteriorates and the resulting printed conductive
The electric resistance of the road coating increases. Titanate-based cups used with PVB resin
The coupling agent is an organic titanium compound having a benzene ring on the hydrophobic group side.
Compound is appropriate, and the compounding amount is carbonaceous conductive particles.
6-14% by weight based on carbon black
And more preferably 8 to 12% by weight.
10% by weight. This value is 12 ~
In terms of the composition of the entire coating material blended at 18% by weight,
0.7-2.5% by weight, 1.0-2.2% by weight and 1.0% by weight.
It becomes 2 to 1.8% by weight. Carbon black
When the compounding amount of the tanate coupling agent is less than 6% by weight
Has a large rate of change in electric resistance. This is in the paint
It is difficult to obtain a good dispersion state of carbon black
And flexibility of the printed conductive circuit film to be formed.
It is because it cannot be obtained. Meanwhile, carbon bra
The amount of the titanate-based coupling agent is 1
If it exceeds 4% by weight, the coating amount of the carbonaceous conductive particles is large.
Increases the electrical resistance of printed conductive circuit coatings
It is not preferable. Furthermore, titanate coupling
Since the boiling point of the agent is 250 ° C or higher,
In addition to the thermosetting treatment for obtaining the film,
In the temperature range of the substrate manufacturing process such as cleaning
Even in a liquid state. For this reason, titanate coupling
In the case of paints containing a large amount of chemicals, the heat history
The adhesion of the printed conductive circuit film to be formed
Significantly worsens. An organic solvent used as a solvent for the conductive paint;
As a solvent for this type of paint,
Recall butyl cellosolve, butyl carbitol
Or butyl carbitol acetate alone or mixed
It is appropriate to use it. Solvent screen
Dries on the plate during printing or produces a peculiar pungent odor
The printed conductive coating after the thermosetting process.
It is required that no paint solvent remains inside the film
However, the above solvent satisfies these conditions. The resole type phenol tree used in the present invention
Some of the fats used in the phenolic resin
At least about 2% of the released phenol remains. This liberation
The boiling point of phenol is about 180 ° C,
Even if the thermosetting treatment is performed at a temperature of 160 ° C. or less,
Remains inside the printed conductive circuit coating. In this state
250 ° C or lower, such as soldering in the circuit board manufacturing process
When exposed to the above temperature atmosphere, free phenol rapidly
Cracks in the printed conductive circuit film
Causes a value change. Therefore, non-volatile at 180 ° C
In the analysis of the emission, the content of free phenol in the nonvolatile
It is desirable that the amount is as small as possible, but 10% by weight
If it is below, it is large even if it remains in the coating of the printed conductive circuit.
Has no significant effect. Thus, non-volatile at 180 ° C
Phenolic Tree with Limited Free Phenol Content in Minerals
The use of fat is one of the requirements to achieve the object of the present invention.
is there. BEST MODE FOR CARRYING OUT THE INVENTION Natural phosphorous or scaly
12 to 18% by weight of graphite having an average particle size of 10 to 30 μm and
Powder consisting of carbon black and 12 to 18% by weight
30% by weight of powder, free
The amount of the phenol is 3 to 1 with respect to the resole type phenol resin.
0 to 30% by weight of resol type phenol resin 25 to 30% by weight
%, Polymerization degree of 1000 to 1800 is 60% by weight or more
0.6-1.8 weight of polyvinyl butyral resin present
%, Titanate-based coupler consisting of an organic titanium compound
0.7-2.5% by weight of a bulking agent, and butyl cellosolve,
Butyl carbitol and butyl carbitol acetate
Consisting of a single or a mixture of organic solvents selected from
Raw materials containing paint solvent as the balance are thoroughly mixed and mixed.
Using a thermosetting carbon-based conductive paint
The resulting printed conductive circuit coating is applied to the printed circuit board.
And has good electrical properties. The present invention will now be described with reference to Examples shown in Tables 1-4.
A specific description will be given using a comparative example. [Preparation of paint] Samples of Examples and Comparative Examples
After thoroughly mixing the mixture with a raikai machine, the mixture is
The mixture was sufficiently kneaded with a mill to form a coating, which was used in the study. This
Here, if the mixing and kneading are insufficient, the resulting printing
Note that the rate of change in the electrical resistance of the conductive circuit coating increases.
It takes care. [Preparation of Samples] Various samples prepared as described above
On a printed circuit board using a screen printing machine
50mm length, 10mm width solid surface pattern printed on
And after leveling, heat curing at 150 ° C for 15 minutes
Processing was performed. [Evaluation of Sample] (1) Sheet resistance The electric resistance of the printed conductive circuit film formed by the above method.
Is measured by the two-needle method, and the electrical resistance during formation of the printed conductive circuit film is measured.
Resistance (R ₀ ). The sheet resistance value (R _S )Box's
From the measured electrical resistance of the solid surface pattern,
Calculated. ## EQU1 ## Usually, in this formula, the printed conductive circuit is used.
Although it is necessary to consider the thickness of the road coating, in the present invention
Formed with the paints listed as working and comparative samples.
The thickness of all printed conductive circuit coatings is in the range of 19 to 21 μm
Therefore, the comparison was performed without correcting the film thickness. (2) Rate of change in resistance Further, the sample was immersed in a solder bath at 260 ° C. for 5 seconds.
Later, the electrical resistance is measured again, and the rate of change of the electrical resistance is determined.
I asked. The rate of change of electrical resistance (ΔR) is calculated by the printed conductive circuit.
Electric resistance (R ₀ ) And electricity after receiving heat
It was calculated from the air resistance value (R) according to the following equation. ## EQU2 ## (3) Adhesion Adhesion of Printed Conductive Film Formed to Printed Circuit Board
To determine the condition, use a cellophane pattern on the solid surface pattern.
After attaching the tape, peel it off and cover it with cellophane tape.
The state of adhesion of the film was observed. <Example 1> (Examples 1 to 4, comparative sample)
1-3) -Characteristics of graphite- Using acetylene black as carbon black,
The compounding ratio of lead and carbon black was 50/50.
PVB resin with a polymerization degree of 1000 (manufactured by Sekisui Chemical Co., Ltd.
Product name: Eslek BH-S) with conductive particles (graphite and graphite)
4% by weight of titanium black
Pulling agent (manufactured by Ajinomoto Co., Inc., trade name: Prenact K)
R9SA) 10% by weight based on carbon black
did. In addition, free ferrous
4% by weight of resole phenol resin with conductive particles
And add butyl cellosolve to the same weight as
30% by weight of the composition,
Prepare conductive paint with different graphite properties according to
A sample was prepared using the sample. Graphite properties and each black
Features of printed conductive circuit coatings obtained from paints made with lead
Table 1 shows the evaluation results. [Table 1] [0027] Phosphorus or flaky graphite particles,
Conductive paint having a uniform particle size of 10 to 30 μm (samples 1 to 3)
The sheet resistance of the printed conductive circuit film obtained in 4) was 3
0Ω / □ or less, and the rate of change in electrical resistance is ± 10% or less
Is within. On the other hand, even phosphorous graphite particles
When the average particle size is less than 10 μm (Comparative Sample 1),
Sheet resistance of printed conductive circuit film is as high as 35Ω / □
In addition, the rate of change of the electric resistance value is as large as 15%. This is graphite
Large contact resistance between conductive particles due to small particle size
And transfer of conductive particles when exposed to a high-temperature atmosphere.
This is because movement is likely to occur. In addition, the average particle diameter is 30μ.
The sheet resistance of Comparative Sample 2 of 40 μm larger than
The resistance value is as high as 32Ω / □, and the rate of change of the electric resistance value is-
It is as large as 25%. This is the conductive particles in the printed conductive circuit coating
Filling rate is low, and film shrinks when immersed in a solder tank
Is caused. Furthermore, the average particle size is 20 μm.
However, the comparative sample 3 using the ground graphite has a low sheet resistance.
The value was 72 Ω / □, and the electrical conductivity of the film was poor. this is
Graphite with low crystallinity, such as clay, has a high specific electrical resistance.
The electrical resistance of the resulting printed conductive circuit coating
It depends. <Example 2> (Examples 5 to 7, Comparative sample)
4-5)-About the compounding ratio of graphite and carbon black-Graphite is a natural phosphorus-like material having an average particle diameter of 16 µm.
Other materials are the same as in Example 1,
Producing paints with different blending ratios of lead and carbon black
Then, a sample was prepared using this. Considered graphite and car
Bon Black Black
Of Printed Conductive Circuit Coatings Obtained from Paints Prepared
Table 2 shows the results. [Table 2] When the mixing ratio of graphite and carbon black is 4
Conductive paint in the range of 0/60 to 60/40
The sheet resistance of the printed conductive film obtained from 5) to 7) is 3
0Ω / □ or less, and the rate of change in electrical resistance is ± 10% or less
Is within. In contrast, a comparison with a lower graphite blending ratio
Sample 4 (graphite / carbon black = 30/70)
The heat resistance is 40Ω / □, and the rate of change of the electric resistance is
It is as high as 40%. With graphite / carbon black = 30/70
Is the amount of fine particles occupying in the conductive carbonaceous powder
And the contact resistance between conductive particles increases, resulting in
And the transfer of conductive particles inside the printed conductive coating
Large change in electrical resistance value
Become. On the other hand, the comparative sample 5 (black
(Lead / carbon black = 70/30)
Although the resistance value is low, the rate of change of the electrical resistance value is large. this
Indicates that the filling rate of the conductive particles is low as in Comparative Sample 2 of Example 1.
This is because the printed conductive circuit film shrinks due to heat.
You. <Example 3> (Examples 8 to 12 and comparative samples)
6-7)-About the compounding amount of PVB (polyvinyl butyral) resin
The graphite used is a natural phosphorous material with an average particle size of 16 μm.
For other materials, the same as in Example 1,
Prepare paints with different blending amounts of VB resin and use them
A sample was prepared. The amount of PVB resin studied (vs. carbon)
Powders) and paints prepared according to their respective amounts
Table 3 shows the results of evaluating the characteristics of the printed conductive circuit film obtained from Example 1.
You. [Table 3] The amount of the PVB resin to be mixed with the conductive particles
2-6% by weight of the conductive paint based on the base powder
8-12) Sheet resistance value of printed conductive film obtained from
Is 30Ω / □ or less, and the rate of change of the electric resistance value is ± 10.
%. On the other hand, when the amount of PVB is 1% by weight,
In Comparative Sample 6, the dispersion of the conductive particles, particularly graphite, was insufficient.
Yes, the filling state of the particles in the obtained printed conductive circuit coating is
The sheet resistance is high and the sheet resistance is as high as 55Ω / □. Also,
Because the printed conductive circuit coating is not flexible
In addition, when immersed in a solder bath, the coating
The difference in thermal expansion of
Occurs, and the change in the electric resistance value increases. On the other hand, PV
In Comparative Sample 7 where the B content exceeds 6% by weight and 7% by weight
In the case of PVB resin, the surface of carbonaceous powder
The electrical resistance of the resulting printed conductive film
Became higher. Also, PVB resin is a thermoplastic resin
From high temperatures, it is susceptible to thermal denaturation at high temperatures.
The rate of change of the air resistance also increased to 35%. <Example 4> (Examples 13 to 17, Comparative Examples
Samples 8-9)-About the compounding amount of the titanate-based coupling agent-The graphite used is a natural phosphorus having an average particle diameter of 16 µm.
The other materials are the same as in the first embodiment.
Producing paints with different blending amounts of tantalate coupling agents
Then, a sample was prepared using this. Titanate studied
-Based coupling agent (to carbon black particles)
And obtained from paints prepared according to the respective loadings
Table 4 shows the results of evaluating the properties of the printed conductive circuit film. [Table 4] Titanate based organic titanium compound
The amount of the coupling agent depends on the carbon black particles.
6-14% by weight of the conductive paint (Examples 13-1
The sheet resistance of the printed conductive film obtained from 7) is 30Ω.
/ □ or less, and the rate of change in electrical resistance is within ± 20%
Conductive paint (in fact, the blending amount is 8 to 12% by weight)
The electrical resistance of the printed conductive film obtained from Application Samples 14 to 16)
The change rate of the resistance value is as good as within ± 5%. Carbon bra
5% by weight (comparative sample 8)
Means that the sheet resistance is high and the rate of change of the electrical resistance is large
No. This is due to insufficient dispersion of the carbon black particles.
Because there is. On the other hand, if the compounding amount exceeds 14% by weight,
At 5% by weight (Comparative Sample 9), the rate of change in
Same as Sample 17 except that the sheet resistance is 40Ω / □
And high printed conductive film for printed circuit boards
Poor adhesion, and the formed film adheres to the cellophane tape side.
I wore it. This is because the amount of titanate-based coupling agent
The amount of conductive particles coated is too large due to too much
Heat treatment at 150 ° C to obtain printed and printed conductive film
The titanate-based coupling agent remains
The printed conductive circuit coating is sufficiently hard
It is because it could not be converted. <Example 5> (Examples 18-21, Comparative
Samples 10 to 12)-About the degree of polymerization of PVB (polyvinyl butyral) resin
The graphite used is a natural phosphorous material with an average particle size of 16 μm.
The other materials are the same as in the first embodiment.
Producing paints with different amounts of PVB resin
Then, a sample was prepared using this. Difference in degree of polymerization studied
Depending on the amount of PVB resin
Of the characteristics of printed conductive circuit coatings obtained from paints prepared in
The results are shown in Table 5. [Table 5] The degree of polymerization of the PVB resin to be blended is 1000 to
1800, and the PVB resin is 60% by weight or less.
In the conductive paint (Examples 18 to 21) included above,
The sheet resistance value of the obtained printed conductive film is 30Ω / □ or less.
And the rate of change of the electric resistance value is also within ± 10%. I
However, 50% by weight of PVB resin having a polymerization degree of 1000 and the polymerization degree
800 conductive powder containing 50% by weight of PVB resin (comparative test
10) and only a PVB resin having a degree of polymerization of 800.
In the case of the conductive paint (Comparative Sample 11), the sheet resistance value is 53
Ω / □ and 97Ω / □ are high, and the rate of change of electric resistance value is also high.
In Comparative Sample 10, it is as large as 85%. This is a low degree of polymerization
Resin has too many active sites, so it is excessively covered with conductive particles.
To impair the electrical conductivity of the resulting coating; and
Thermoplastic resin with low degree of polymerization has poor heat resistance,
If exposed to a high temperature environment such as immersion in a solder bath,
This is because the change in resistance value is likely to occur. one
On the other hand, a conductive paint containing only a PVB resin having a polymerization degree of 2100
In (Comparative Sample 12), carbonaceous powder as conductive particles,
Sheet resistance is large due to poor dispersibility of graphite particles
Become. Example 6 (Examples 22 to 25, Comparative
Samples 13 to 14)-Free pheno in non-volatile content of resole type phenol resin
-The amount of graphite used is natural phosphorus with an average particle size of 16 μm.
The other materials are the same as in the first embodiment.
Resol with different amount of free phenol in non-volatile matter at 80 ℃
A paint is made using a phenolic resin
To prepare a sample. The amount of free phenol studied and
Characteristics of the printed conductive circuit film obtained from each coating
Table 6 shows the results of the sex evaluation. [Table 6] The reaction at 180 ° C. with phenol resin
The amount of free phenol in volatiles is 2% even after purification
The degree remains. 10% by weight of this free phenol
For conductive paints up to (samples 22 to 25), the electrical resistance
The rate of change of the value can be suppressed within ± 10%. I
However, the amount of free phenol exceeds 10% by weight
In the case of the conductive paints (Comparative Samples 13 and 14), the electric resistance
Conversion rate increases. This is a printed guide cured at 150 ° C.
Because there is much free phenol remaining in the coating of the electric circuit
In a high temperature environment such as when immersing the sample in a solder bath
, Free phenol volatilizes from the coating, and print conductivity
Cracks occur in the circuit coating, causing conductive particles to make conductive contact
It is due to cutting off. According to the present invention, natural phosphorous or flaky average grains
12 to 18% by weight of graphite having a diameter of 10 to 30 μm and car
Carbonaceous powder 3 containing bon black in an amount of 12 to 18% by weight
0% by weight, free phenol in nonvolatile matter at 180 ° C.
10% by weight or less based on the resole type phenol resin
Lower resole type phenolic resin 25-30% by weight, polymerization
60% by weight or more with a degree of 1000-1800
Polyvinyl butyral resin 0.6-1.8% by weight, organic
Titanate-based coupling agent composed of a titanium compound
7-2.5% by weight, and butyl cellosolve, butyl
From carbitol and butyl carbitol acetate
Paint solution consisting of selected single or mixed organic solvents
Thoroughly mix and knead raw materials containing medium as the remaining amount
The thermosetting carbon-based conductive paint obtained from
Print on printed circuit board by printing method,
At least 10 minutes at a time
With sufficient adhesion to the printed circuit board
A coating of the printed conductive circuit is formed. In addition, this printed conductive
The sheet resistance value representing the electrical conductivity of the circuit coating is 15 to 30.
Low value of Ω / □, printing such as dipping in solder bath
In an environment that is higher than the temperature at which the conductive circuit coating is formed
In this case, the rate of change of the electric resistance value is ± 10% or less.
Printed conductive circuit with stable electrical characteristics
You. For this reason, carbon with little variation in circuit design
It is possible to obtain a printed circuit board with a coating.

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Claims (1)

(57) [Claim 1] A solution obtained by dissolving a titanate coupling agent comprising a resole type phenol resin, polyvinyl butyral, and an organic titanium compound in a coating solvent,
In a thermosetting carbon-based conductive paint in which carbonaceous powder of graphite and carbon black is dispersed as conductive particles,
(A) 30% by weight of carbonaceous powder composed of 12 to 18% by weight of the graphite and 12 to 18% by weight of carbon black, 25 to 30% by weight of the resole phenol resin, 0.6 to 1.8% by weight of the polyvinyl butyral resin %, Titanate-based coupling agent comprising the above-mentioned organotitanium compound 0.1%.
7 to 2.5% by weight and a coating solvent consisting of a single or a mixture of organic solvents selected from butyl cellosolve, butyl carbitol and butyl carbitol acetate as a residual amount; The amount of free phenol in the nonvolatile matter at 180 ° C. is 3 to 10% by weight based on the resol type phenol resin, and (c) the graphite of the carbonaceous powder is natural phosphorous or flaky graphite particles. The thermosetting resin has an average particle size of 10 to 30 μm, and (d) the polyvinyl butyral resin contains at least 60% by weight of a polymer having a degree of polymerization of 1,000 to 1,800. Carbon-based conductive paint.