JP2742190B2 - Curable conductive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel curable conductive composition. In detail, even in the case of obtaining a thick conductive hardened body, such as a case where a through hole for a through hole of a circuit forming substrate is filled and hardened to form a conductive through hole, no crack is generated during hardening. Moreover, the obtained cured product is a curable conductive composition that exhibits stable conductivity over a long period of time.

[0002]

2. Description of the Related Art Curable conductive compositions are used in the electronics field for many applications such as IC circuits, conductive adhesives, and electromagnetic wave shields. In particular, recently, there is a technology that fills and cures a curable conductive composition into a through-hole for forming a through-hole, forms a conductive through-hole, fills the through-hole, and allows components to be mounted thereon. Proposed.

In the use of the above-mentioned curable conductive composition, there is a problem that cracks are generated in the cured product due to thermal shock during or after curing of the curable conductive composition.
That is, the curable conductive composition exhibits conduction performance due to contact between metal powders due to curing shrinkage of the curable resin, and is accompanied by shrinkage during curing. For this reason, it has been pointed out that the above-mentioned curable conductive composition generally tends to generate cracks inside the cured product during curing. Further, even after curing, there remains a problem that cracks occur due to thermal shock.

As a method for solving such a problem, attempts have been made to suppress the occurrence of cracks by adding a flexibility-imparting agent such as a modified organosiloxane to the curable conductive composition.

[0005]

However, the curable conductive composition to which the above-described flexibility-imparting agent has been added is resistant to thermal shock when used in applications such as IC circuits, conductive adhesives, and electromagnetic wave shields. Although it has a certain degree of effect, it can be used at the time of curing to obtain a thick conductive cured body as in the case of forming a conductive through-hole by filling the through-hole for through-hole, or cooling after curing. The generation of cracks due to impact cannot be prevented. When the amount of the flexibility-imparting agent is increased to an amount sufficient to prevent the above-mentioned phenomenon, the shrinkability of the curable conductive composition is reduced, and the conductivity of the obtained cured product is reduced. It has the problem of sacrificing. Such a problem is remarkable when copper powder is used as the metal powder.

Accordingly, even when a thick conductive cured body is formed, no crack is generated during curing, and moreover,
It has been desired to develop a curable conductive composition in which the obtained cured product exhibits high conductivity for a long period of time.

[0007]

Means for Solving the Problems The present inventors have intensively studied to solve the above problems. As a result, as the epoxy resin constituting the curable conductive composition, an epoxy resin containing a specific amount of a monoglycidyl compound having a specific structure is used, and a dendritic metal powder having a specific particle size distribution is used as a metal powder. By doing so, the effects of these configurations act synergistically, and the curable conductive composition is excellent in preventing cracks from occurring during curing, and the resulting cured product exhibits high conductivity over a long period of time. It was found that a product was obtained, and the present invention was completed.

That is, the present invention provides an epoxy resin, a curing agent,
And, based on 100 parts by weight of the total amount of the epoxy resin and the curing agent, 300 to 2000 parts by weight of dendritic metal powder, the resinous metal powder has an average particle size of 10 to 15 μm,
The ratio of the metal powder having a particle size exceeding 40 μm is 0.05% by volume.
The standard deviation log, defined below, and defined by a logarithmic distribution function
σ is 0.26 or less, and the epoxy resin is a bisphenol A diglycidyl ether having an epoxy equivalent of 200 g / equivalent or less, and a straight-chain alkyl monoglycidyl ether having 11 to 13 carbon atoms and / or a straight chain having 9 to 11 carbon atoms. Curability characterized by comprising at least one monoglycidyl compound selected from linear alkyl monoglycidyl esters and containing the monoglycidyl compound in a proportion of 20 to 60% by weight based on bisphenol A diglycidyl ether. It is a conductive composition.

In the present invention, the average particle size of the metal powder and the standard deviation logσ defined by the logarithmic distribution function, and 4
The ratio of the metal powder having a particle size exceeding 0 μm is measured by a laser scattering method. That is, based on the measurement data of the particle size distribution of the metal powder measured by the laser scattering method,
Standard deviation log defined by average particle size and logarithmic distribution function
σ and the ratio of metal powder having a particle size exceeding 40 μm were calculated. In addition, the average particle diameter of the metal powder in the present invention indicates a volume average particle diameter.

The epoxy resin used in the present invention comprises bisphenol A diglycidyl ether having an epoxy equivalent of 200 g / equivalent or less, a linear alkyl monoglycidyl ether having 11 to 13 carbon atoms and / or a linear alkyl having 9 to 11 carbon atoms. It is important to have a composition consisting of a monoglycidyl ester and a monoglycidyl compound.

That is, the epoxy resin used in the present invention is:
Due to the interaction by using a bisphenol A diglycidyl ether and a monoglycidyl compound as a cross-linking component and the use of a specific metal powder described later, the curable conductive composition can be cooled or heated at the time of curing. The effect of preventing generation of cracks due to impact can be exhibited.

In the present invention, the reason why the bisphenol A type epoxy resin is used as a cross-linking component of the epoxy resin is that the water absorption rate is low and the cross-link density due to curing is high. When the bisphenol A diglycidyl ether has an epoxy equivalent exceeding 200 g / equivalent,
The crosslink density accompanying the curing of the curable conductive composition decreases, and good conductivity cannot be obtained.

In the present invention, when the number of carbon atoms of the linear alkyl monoglycidyl ether used as one component of the epoxy resin exceeds 13, or when the number of carbon atoms of the linear alkyl monoglycidyl ester exceeds 11, Since the β-dispersion temperature of the obtained epoxy resin is high, the cured product of the obtained curable conductive composition has low thermal shock resistance, and in particular, low crack resistance at low temperatures. In addition, the effect of alleviating stress concentration caused by shrinkage during curing of the curable conductive composition is reduced, which also tends to cause cracks during curing.

The above-mentioned monocricidyl compound having a carbon number of less than 1 is generally a liquid having a low viscosity, whereby the viscosity of bisphenol A diglycidyl ether can be adjusted.

On the other hand, when the carbon number of the straight-chain alkyl monoglycidyl ether is smaller than 11, and when the carbon number of the straight-chain alkyl monoglycidyl ester is smaller than 9, the boiling point decreases, and the volatilization amount during heat curing is reduced. Since the size of the cured product increases, the cured product undergoes abnormal shrinkage during curing, and cracks easily occur in the obtained cured product.

It is important that the monoglycidyl compound has a linear alkyl chain. That is, when a monoglycidyl compound having a structure in which the alkyl chain is branched is used, the β dispersion temperature of the epoxy resin tends to increase.

In the present invention, the epoxy resin contains the monoglycidyl compound in an amount of 20 to 60% by weight, preferably 30 to 60% by weight based on the bisphenol A diglycidyl ether.
It is blended at a ratio of 50% by weight.

The proportion of the monoglycidyl compound is 20% by weight.
If the amount is smaller, the effect of lowering the β dispersion temperature of the epoxy resin becomes insufficient, and the crack resistance is reduced. Also,
If the proportion of the monoglycidyl compound exceeds 60% by weight, good conductivity cannot be obtained because the crosslink density accompanying the curing of the epoxy resin decreases.

In the present invention, as the curing agent, those known as curing agents for epoxy resins can be used. For example, metaphenylene diamine, diaminodiphenylmethane, amines such as diaminodiphenylsulfone, phthalic anhydride,
Acid anhydrides such as succinic anhydride, trimellitic anhydride, pyromellitic anhydride, and tetrahydrophthalic anhydride, compound-based curing agents such as imidazoles, dicyandiamide, and resin-based curing agents such as phenolic resins, polyamide resins, and urea resins. No. In particular, novolak-type phenolic resin or novolak-type cresol resin is excellent in moisture resistance, heat resistance, and has reducibility, long pot life, and appropriate curing temperature for printed wiring boards and the like. Since the amount of by-products that cause voids is extremely small, it is most suitable as the curing agent of the present invention.
What is necessary is just to select the amount normally used according to the kind of hardening agent used as the addition amount of the said hardening | curing agent. Generally, it is preferably 0.3 to 2.0 equivalents, more preferably 0.5 to 1.3 equivalents, per equivalent of epoxy group of the epoxy resin. When the curing agent is less than 0.3 equivalent or more than 2.0 equivalents relative to 1 equivalent of epoxy group of the epoxy resin,
The crosslinked density of the obtained cured product tends to be low, and good conductivity may not be obtained in some cases.

In the present invention, the use of electrically conductive resinous metal powder as the metal powder provides good adhesion to the epoxy resin and the occurrence of cracks at the interface between the metal powder and the binder. By preventing the occurrence of cracks and by adjusting to a specific particle size distribution described below and combining with the epoxy resin, no crack is generated at the time of curing, and the obtained cured product exhibits stable conductivity for a long period of time. It is necessary to obtain a curable conductive composition.

As the material of the resinous metal powder, a known material having conductivity is used without any particular limitation. For example, copper,
Silver, nickel, iron and the like.

In the present invention, it is necessary that the resinous metal powder has an average particle size of 10 to 15 μm. That is, when the average particle size of the resinous metal powder is smaller than 10 μm, good conductivity is obtained because the number of contact points between the resinous metal powders increases, but the particle size distribution of the metal powder is limited to the above range. Even if it does, the generation of cracks during curing cannot be suppressed, and the object of the present invention cannot be achieved. On the other hand, if the average particle size exceeds 15 μm, cracks tend to occur at the interface between the epoxy resin and the metal powder.

Further, in the present invention, the resinous metal powder comprises 4
The ratio of metal powder having a particle size exceeding 0 μm is 0.05% by volume or less, and a standard deviation logσ defined by a logarithmic distribution function
Needs to be 0.26 or less.

That is, the present inventors have conducted various studies on the causes of cracks in the curable conductive composition during curing. As a result, when metal powder having a relatively large particle size is present in the metal powder, Cracks are preferentially generated at the interface between the resin and the resin. Then, the large-diameter particles of the metal powder are subjected to a standard deviation log defined by a logarithmic distribution function.
σ is limited to 0.26 or less, and by reducing the metal powder having a particle size exceeding 40 μm, by the synergistic effect with the action of the monoglycidyl compound, the curable conductive composition at the time of curing This has succeeded in effectively preventing the occurrence of cracks.

[0025] The commercially available resinous copper powder is 40
When no metal powder having a particle size exceeding μm is contained and the standard deviation logσ defined by the logarithmic distribution function is 0.26 or less,
The average particle size is less than 10 μm, and the average particle size is 10 to 15
In the case of μm, the standard deviation log defined by the logarithmic distribution function
Includes metal powder having a particle diameter of σ exceeding 0.30 or exceeding 40 μm.

The method for producing the resinous copper powder having the above specific average particle diameter and particle size distribution used in the present invention is not particularly limited. For example, rake classifier, spiral classifier, wet classification method such as hydrocyclone, sieve,
A method using a dry classification method such as a rotary classifier, a centrifugal classifier, or an air separator is preferable.

In the present invention, the resinous metal powder is used in an amount of 30 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent.
It is used in a proportion of 0 to 2000 parts by weight, preferably 400 to 700 parts by weight.

If the proportion of the resinous metal powder is less than 300 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent, good conductivity cannot be obtained. When the ratio of the resinous metal powder exceeds 2,000 parts by weight, not only does the fluidity deteriorate, causing problems in handling such as printability, but also weakening the bonding force of the obtained hardened metal powder. This is not preferred because the conductivity is reduced. Further, in order to obtain a curable conductive composition having both stable conductivity and good handleability, the amount of the resinous metal powder to be added is based on 100 parts by weight of the total amount of the epoxy resin and the curing agent. It is particularly preferable that the content be 400 to 700 parts by weight.

The curable conductive composition of the present invention may optionally contain a curing accelerator in addition to the above-mentioned curing agent. For example, tertiary amines and imidazoles can be suitably used for acid anhydrides, dicyandiamide, phenol resins, aromatic amines and the like. The addition amount of such a curing accelerator is suitably from 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent.

The curable conductive composition of the present invention does not particularly require a solvent, but may be used by adjusting the viscosity by adding a solvent as appropriate according to the use. As the solvent, known solvents can be used without any particular limitation. For example,
Examples include alcohols such as isopropanol and butanol, esters such as ethyl acetate and butyl acetate, and carbitols such as ethyl carbitol and butyl carbitol. The above solvents may be used alone or in combination of two or more.

The curable conductive composition of the present invention may contain known additives as long as the properties are not significantly reduced. Examples of such additives include an antifoaming agent, a dispersant, a thixotropic agent, a leveling agent, a rust inhibitor, a reducing agent, and the like.

The method for producing the curable conductive composition of the present invention comprises:
Although not particularly limited, the above-described epoxy resin, a curing agent, a metal powder and various additives that are blended as necessary are mixed, and a known dispersing device such as a disper, a ball mill,
It can be manufactured by kneading using a three-roll mill, a Hoover muller or the like.

The curable conductive composition of the present invention comprises a spray,
It can be painted, printed or filled by a known method such as brushing, dipping, offset printing, screen printing and the like.

[0034]

The curable conductive composition of the present invention uses an epoxy resin containing a specific amount of a monoglycidyl compound having a specific structure as an epoxy resin constituting the curable conductive composition, and as a metal powder. Due to the synergistic effect of using resinous metal powder having a specific particle size distribution,
It has an excellent effect of preventing the occurrence of cracks during curing and preventing the occurrence of cracks due to thermal shock of the obtained cured product. It also has the feature of exhibiting high conductivity for a long time.

Accordingly, the curable conductive composition of the present invention is preferably used in applications where a thick cured product such as through-hole plugging is formed by utilizing the above characteristics.
High reliability can be obtained.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Examples 1 to 14 and Comparative Examples 1 to 16 Various metal powders shown in Table 1 were prepared. The metal powder was added as a dispersant in an amount of 0.25 × 10
^-5 mmol / cm ² of linoleic acid and 3 wt. H. Premixing was performed by adding T.

On the other hand, a monoglycidyl compound of the type shown in Table 2 was blended with bisphenol A diglycidyl ether having an epoxy equivalent of 173 g / equivalent so as to have a ratio (% by weight) shown in Table 2 to constitute an epoxy resin. In addition, the metal powder was blended at a ratio (parts by weight) shown in Table 2 with respect to 100 parts by weight of the total amount of the epoxy resin and the curing agent, and the curing agent shown in Table 2 was further added to 100 parts by weight of the epoxy resin. Parts by weight as shown in Table 2 (parts by weight), and further, 1 part by weight of 2 ethyl 4-methylimidazole is added as a curing accelerator to 100 parts by weight of the epoxy resin,
These were mixed by a three-roll mill for 30 minutes to obtain a curable conductive composition.

In addition, among the various metal powders shown in Table 1, A,
For B, G and H, commercially available dendritic copper powder was used, and for all others, classification was performed using a sieve (sieve) to remove metal powder having a large particle diameter.

Further, Example 7, Comparative Examples 8, 10, 12,
In No. 14, the viscosity of the curable conductive composition was 300 to 3
To adjust to 000 poise, an appropriate amount of butyl cellosolve was added as a solvent during kneading.

The obtained curable conductive composition was printed on a glass epoxy substrate by a screen printing method.
The circuit patterns shown in FIGS. 2 and 3 were created. In addition, the board | substrate in the through-hole pattern of FIG.2, FIG.3 used the thing of thickness 1.6mm and the through-hole diameter 0.8mm (phi). The through-hole pattern was cured by drying in a hot-air drying furnace at 80 ° C. for 2 hours, and then cured in a far-infrared furnace controlled at 180 ° C. for 6 minutes. On the other hand, the pattern of FIG. 1 was cured in a far-infrared furnace controlled at 180 ° C. for 6 minutes.

After curing, the resistance of each circuit pattern was measured with a digital multimeter, and the average value of the volume resistivity and the through-hole resistance was calculated. 2 through-hole resistance
Those exceeding 00 mΩ / hole were counted as defective rates after curing. The through-hole resistance was represented by an average value excluding defective through-holes.

As for the through-hole pattern, a cooling / heating cycle test was performed on 10,000 holes of each example and comparative example at -65 ° C. for 30 minutes to 125 hours.
500 cycles were performed at 30 ° C. for 30 minutes. After the cooling / heating cycle test, the number of through-hole resistances increased by 30% or more was counted and expressed as a defective rate after the cooling / heating test.

The results are summarized in Table 3.

In addition, as a result of observing the occurrence of cracks and voids in the cured product of the curable conductive composition in the through-hole obtained according to the present invention, no cracks or voids were found.

Comparative Example 17 A paste was kneaded in the same manner as in Example 1 except that bisphenol A diglycidyl ether having an epoxy equivalent of 280 g / equivalent was used, and the obtained curable conductive composition was evaluated in the same manner. Was. The results are shown in Table 3.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[Brief description of the drawings]

FIG. 1 is a pattern for measuring volume resistivity.

FIG. 2 is a plan view of a through-hole substrate for measuring a through-hole resistance.

FIG. 3 is a sectional view of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Through hole 2 Copper foil 3 Substrate

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/09 H05K 1/09 D 3/40 3/40 K (C08K 13/04 5:15 7:00)

Claims (1)

(57) [Claims] An epoxy resin, a curing agent, and 300 parts by weight based on a total amount of 100 parts by weight of the epoxy resin and the curing agent.
2,000 parts by weight of dendritic metal powder, wherein the resinous metal powder has an average particle size of 10 to 15 μm, a ratio of metal powder having a particle size exceeding 40 μm is 0.05% by volume or less, and a logarithmic distribution function Is less than or equal to 0.26, and the epoxy resin has an epoxy equivalent of 200 g
/ Equivalent or less of bisphenol A diglycidyl ether and at least one monoglycidyl compound selected from linear alkyl monoglycidyl ethers having 11 to 13 carbon atoms and linear alkyl monoglycidyl esters having 9 to 11 carbon atoms. A curable conductive composition comprising a monoglycidyl compound in an amount of 20 to 60% by weight based on bisphenol A diglycidyl ether.