JPH06184409A - Electrically conductive curable composition - Google Patents

Abstract

PURPOSE:To provide an electrically conductive curable composition free from crack-generation in curing and giving a cured material exhibiting electrical conductivity stable over a long period. CONSTITUTION:This electrically conductive curable composition contains an epoxy resin, a curing agent and 300-2,000 pts.wt. (based on 100 pts.wt. of the sum of the epoxy resin and the curing agent) of dendritic metal powder having an average particle diameter of 10-15mum and containing <=0.05vol.% of powder having particle diameter of >40mum. The epoxy resin is composed of a bisphenol A diglycidyl ether having an epoxy equivalent of <=200g/equivalent and at least one kind of monoglycidyl compound selected from 11-13C straight-chain alkyl monoglycidyl ether and 9-11C straight-chain alkyl monoglycidyl ester. The amount of the monoglycidyl compound is 20-60wt.% based on the bisphenol A diglycidyl ether.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel curable conductive composition. In detail, even when a conductive cured body having a large thickness is obtained, such as a case where a through hole for a through hole of a circuit forming substrate is filled and cured to form a conductive through hole, cracks do not occur during curing. 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 many fields such as IC circuits, conductive adhesives, and electromagnetic wave shields in the field of electronics. In particular, recently, there is also a technology that fills and cures a through hole for forming a through hole with a curable conductive composition to form a conductive through hole, fills the through hole, and enables mounting of a component on the through hole. Proposed.

In the use of the above-mentioned curable conductive composition, the generation of cracks in the cured product due to cold heat shock during or after the curing of the curable conductive composition becomes a problem.
That is, the curable conductive composition exhibits conductivity by contact between metal powders due to curing shrinkage of the curable resin, and is accompanied by shrinkage during curing. Therefore, it has been pointed out that the curable conductive composition generally causes cracks inside the cured body during curing. Further, even after curing, the problem that cracks occur due to thermal shock remains.

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

[0005]

However, the curable conductive composition to which the above-mentioned flexibility-imparting agent is added is resistant to thermal shock when used for applications such as IC circuits, conductive adhesives and electromagnetic wave shields. Has a certain degree of effect, but at the time of curing when obtaining a conductive cured body having a thickness, such as when filling the through holes for through holes to form conductive through holes, or at the time of cooling after curing. It is not possible to prevent the occurrence of cracks on impact. Further, when the addition 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 decreases, and the conductivity of the obtained cured product is reduced. Has the problem of sacrificing. Such a problem is remarkable when copper powder is used as the metal powder.

Therefore, even when a thick conductive cured body is formed, cracks do not occur during curing, and
It has been desired to develop a curable conductive composition in which the obtained cured product exhibits a high degree of conductivity over a long period of time.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, as the epoxy resin constituting the curable conductive composition, using an epoxy resin containing a specific amount of a monoglycidyl compound having a specific structure, and using a dendritic metal powder having a specific particle size distribution as the metal powder By doing so, the effects of these constitutions act synergistically, excellent in the occurrence of cracks during curing, and the resulting cured product is a curable conductive composition that 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 relates to 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, and the resinous metal powder has an average particle size of 10 to 15 μm.
The ratio of metal powder with a particle size exceeding 40 μm is 0.05% by volume
The standard deviation log defined below and by the logarithmic distribution function
σ is 0.26 or less, the epoxy resin is an epoxy equivalent of 200 g / equivalent or less of bisphenol A diglycidyl ether, a straight chain alkyl monoglycidyl ether having 11 to 13 carbon atoms, and / or a straight chain having 9 to 11 carbon atoms. Curable, characterized by comprising at least one monoglycidyl compound selected from chain alkyl monoglycidyl esters, wherein the monoglycidyl compound is contained in a proportion of 20 to 60% by weight with respect to 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 mean particle size and logarithmic distribution function
The ratio of σ and the metal powder having a particle size exceeding 40 μm was 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 includes 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 group having 9 to 11 carbon atoms. It is important to have a composition consisting of a monoglycidyl compound of a monoglycidyl ester.

That is, the epoxy resin used in the present invention is
During the curing of the curable conductive composition or the cooling of the cured product, due to the interaction by using a composition in which bisphenol A diglycidyl ether, which is a crosslinking component, and a monoglycidyl compound are combined, and by using a specific metal powder described below. The effect of preventing the occurrence of cracks due to impact can be exhibited.

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

In the present invention, when the linear alkyl monoglycidyl ether used as one component of the epoxy resin has more than 13 carbon atoms or the linear alkyl monoglycidyl ester has more than 11 carbon atoms, Since the β-dispersion temperature of the obtained epoxy resin becomes high, the thermal shock resistance of the cured product of the obtained curable conductive composition is lowered, and especially the crack resistance at low temperatures is lowered. Further, the effect of alleviating the stress concentration generated by the shrinkage of the curable conductive composition at the time of curing is reduced, and this also tends to cause cracks at the time of curing.

The above-mentioned monochrysidyl compound having carbon number or less is generally a liquid having a low viscosity, and the viscosity of bisphenol A diglycidyl ether can be adjusted by this.

On the other hand, when the linear alkyl monoglycidyl ether has a carbon number of less than 11, and when the linear alkyl monoglycidyl ester has a carbon number of less than 9, the boiling point is lowered and the volatilization amount during heat curing is reduced. Since the size of the cured product becomes large, the cured product abnormally contracts during curing, and the resulting cured product is likely to be cracked.

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

In the present invention, the epoxy resin contains 20 to 60% by weight, preferably 30 to 60% by weight of a monoglycidyl compound with respect to the bisphenol A diglycidyl ether.
It is compounded at a ratio of 50% by weight.

20% by weight of monoglycidyl compound
If it is less, the effect of lowering the β dispersion temperature of the epoxy resin becomes insufficient, and the crack resistance decreases. Also,
If the proportion of the monoglycidyl compound exceeds 60% by weight, the crosslink density is lowered with the curing of the epoxy resin, and good conductivity cannot be obtained.

In the present invention, a known curing agent for epoxy resin can be used as the curing agent. For example, amines such as metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride,
Acid anhydrides such as succinic anhydride, trimellitic anhydride, pyromellitic anhydride, and tetrahydrophthalic anhydride, compound-based curing agents such as imidazoles and dicyandiamide, resin-based curing agents such as phenol resins, polyamide resins, and urea resins Can be mentioned. In particular, novolac-type phenol resin or novolac-type cresol resin has excellent moisture resistance, heat resistance, and reducibility, long pot life, and appropriate curing temperature for printed wiring boards. It is most suitable as the curing agent of the present invention because the amount of by-products that cause voids is extremely small.
The addition amount of the above-mentioned curing agent may be selected from the amount usually used according to the kind of the curing agent used. Generally, the amount is 0.3 to 2.0 equivalents, preferably 0.5 to 1.3 equivalents, relative to 1 equivalent of the epoxy group of the epoxy resin. When the curing agent is less than 0.3 equivalent or more than 2.0 equivalent to 1 equivalent of epoxy group of the epoxy resin,
The crosslinked density of the obtained cured product tends to be small, and good conductivity may not be obtained in some cases.

In the present invention, the use of a resinous metal powder having conductivity as the metal powder has good adhesiveness with the epoxy resin and causes cracks due to peeling at the interface between the metal powder and the binder. In order to prevent the above, and by adjusting to a specific particle size distribution described later and by combining with the epoxy resin, there is no occurrence of cracks during curing, and the resulting cured product exhibits stable conductivity over a long period of time. It is necessary to obtain the curable conductive composition.

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

In the present invention, the resinous metal powder needs to have 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 can be 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 range described above. Even if it does, the generation of cracks during curing cannot be suppressed, and the object of the present invention cannot be achieved. If the average particle size exceeds 15 μm, cracks are likely to occur at the interface between the epoxy resin and the metal powder.

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

That is, the inventors of the present invention have conducted various studies on the cause 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, the metal powder It was found that cracks preferentially occur at the interface between and. And, the standard deviation log defined by the logarithmic distribution function for the large-sized particles of the metal powder.
By limiting the σ to be 0.26 or less and reducing the metal powder having a particle size of more than 40 μm, a synergistic effect with the action of the above monoglycidyl compound is exerted. We succeeded in effectively preventing the occurrence of cracks.

The commercially available resinous copper powder is 40
When the metal powder having a particle size exceeding μm is not included 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
A metal powder having a particle diameter of σ of more than 0.30 or more than 40 μm is included.

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

In the present invention, the resinous metal powder is 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 ratio 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 proportion of the resinous metal powder is more than 2000 parts by weight, the fluidity is lowered, and not only the handling such as printability is problematic but also the binding force of the metal powder of the obtained cured product is weakened. However, the conductivity is lowered, which is not preferable. In addition, in order to obtain a curable conductive composition having both stable conductivity and good handleability, the amount of the resinous metal powder added is 100 parts by weight based on the total amount of the epoxy resin and the curing agent. It is particularly preferable that the amount is 400 to 700 parts by weight.

A curing accelerator may be added to the curable conductive composition of the present invention, if necessary. For example, tertiary amines and imidazoles can be preferably used for acid anhydrides, dicyandiamide, phenolic resins, aromatic amines and the like. An appropriate amount of the curing accelerator added is 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 require a solvent in particular, but it may be used by adjusting the viscosity by adding a solvent depending on the application. As the solvent, known solvents can be used without particular limitation. For example,
Examples thereof include alcohols such as isopropanol and butanol, esters such as ethyl acetate and butyl acetate, and carbitols such as ethyl carbitol and butyl carbitol. You may use the said solvent individually or in mixture of 2 or more types.

Known additives may be added to the curable conductive composition of the present invention within a range that does not significantly deteriorate the properties thereof. Examples of such additives include a defoaming agent, a dispersant, a thixotropic agent, a leveling agent, a rust preventive, and a reducing agent.

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

The curable conductive composition of the present invention is a spray,
Coating, printing or filling can be performed by a known method such as brush coating, 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 uses it as a metal powder. Due to the synergistic effect of using resinous metal powder having a specific particle size distribution,
It exhibits an excellent effect in preventing the occurrence of cracks during curing and in preventing the occurrence of cracks due to the thermal shock of the resulting cured product. It also has the characteristic of exhibiting a high degree of conductivity over a long period of time.

Therefore, the curable conductive composition of the present invention is suitably used in the application of forming a thick cured body such as through hole filling, 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 contained 0.25 × 10 5 per surface area of the metal powder as a dispersant.
^-5 mmol / cm ² of linoleic acid, and 3 wt% of B. H. T was added to perform premixing.

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

Among the various metal powders shown in Table 1, A,
Commercially available dendritic copper powders were used for B, G, and H, and all other powders were classified using a sieve to remove large-diameter metal powders.

In addition, Example 7, Comparative Examples 8, 10, 12,
14, the curable conductive composition has a viscosity of 300 to 3
To adjust to 000 poise, an appropriate amount of butyl cellosolve was added as a solvent during kneading.

The curable conductive composition thus obtained was printed on a glass epoxy substrate by a screen printing method, as shown in FIG.
The circuit patterns shown in FIGS. 2 and 3 were created. The substrate in the through hole patterns of FIGS. 2 and 3 had a thickness of 1.6 mm and a through hole diameter of 0.8 mmφ. The through-hole pattern was cured by drying in a hot air drying oven at 80 ° C. for 2 hours and then in a far infrared oven controlled at 180 ° C. for 6 minutes. On the other hand, the pattern of FIG. 1 was cured by a far-infrared furnace whose temperature was controlled at 180 ° C. for 6 minutes.

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

Regarding the through-hole pattern, a cooling / heating cycle test was carried out at 10,000 holes for each example and comparative example at -65 ° C. for 30 minutes to 125.
500 cycles were performed under conditions of 30 ° C. and 30 ° C. After the cooling / heating cycle test, the ones in which the through-hole resistance increased by 30% or more were counted and expressed as the defective rate after the cooling / heating test.

The results are summarized in Table 3.

The cured product of the curable conductive composition in the through hole obtained by the present invention was observed for the presence of cracks and voids. As a result, no cracks or voids were found.

Comparative Example 17 The 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. It was The results are also shown in Table 3.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[Brief description of 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.

3 is a cross-sectional view of FIG.

[Explanation of symbols]

 1 Through hole 2 Copper foil 3 Board

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01B 1/22 A 7244-5G H05K 1/09 D 6921-4E 3/40 K 7511-4E

Claims (1)

[Claims] 1. An epoxy resin, a curing agent, and 300 parts by weight per 100 parts by weight of the total amount of the epoxy resin and the curing agent.
˜2000 parts by weight of dendritic metal powder, wherein the resinous metal powder has an average particle size of 10 to 15 μm, the ratio of the metal powder having a particle size of more than 40 μm is 0.05% by volume or less, and a logarithmic distribution function. Has a standard deviation log σ of 0.26 or less, 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 ether having 11 to 13 carbon atoms and linear alkyl monoglycidyl ester having 9 to 11 carbon atoms A curable conductive composition comprising a monoglycidyl compound in a proportion of 20 to 60% by weight based on bisphenol A diglycidyl ether.