JP2009146679A - Conductive paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive paste which is capable of forming a layer having suitability for solder and excellent in curability even if it is not subjected to plating. <P>SOLUTION: The conductive paste contains 100 parts by weight of conductive particles, 2-10 parts by weight of Lysol type phenol-modified xylene resin and 0.01-0.7 part by weight of a polyvalent carboxylic acid, wherein the conductive particles contain 60% by weight of nickel powder coated with silver. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive paste, and more particularly to a conductive paste suitable for use in a terminal electrode of an electronic component.

  For terminal electrodes of chip electronic components such as chip capacitors, chip inductors, chip resistors, etc. that are surface-mounted on the substrate, conduction with internal electrodes, low electrical resistance, adhesion to surrounding materials, suitability for solder, etc. A wide variety of required performance is required. In order to satisfy these various required performances, the terminal electrode usually has a multilayer structure in which a plurality of layers are laminated.

  As a typical terminal electrode structure, as shown in the sectional view of the terminal electrode of the conventional chip capacitor in FIG. 1, the metal layer 5 is formed as a first layer by sputtering, thermal spraying and sintering, and the second layer is nickel. The structure provided with the tin plating layer 7 as the plating layer 6 and the 3rd layer is mentioned.

  In this structure, the first layer mainly exhibits continuity with internal electrodes, low electrical resistance, and plating suitability, the second layer mainly exhibits solder heat resistance, and the third layer mainly exhibits solder wettability. Take charge.

  As described above, the second layer and the third layer have been indispensable processes for ensuring the suitability for the solder as described above. It is necessary to dispose of the waste liquid. Therefore, there is an increasing demand for terminal electrodes that are not plated not only from the viewpoint of improving productivity by omitting processes but also from the viewpoint of environmental problems.

In order to meet this requirement, there has been proposed a technique for forming a terminal electrode without providing the second layer and the third layer by imparting suitability to solder to the conductive paste. For example, the conductive paste which disperse | distributed the electroconductive particle which coat | covered copper and copper-nickel alloy powder with silver to the phenol resin is mentioned (refer patent documents 1-5). However, these curing reactions are thermal condensation reactions of phenol resins, and there is a problem that a large amount of heat is required and the curing conditions are high temperature and long time. Naturally, when the curing conditions are high or for a long time, the energy cost increases, and in addition to being unsuitable for film capacitors using materials with relatively poor heat resistance, oxidation of conductive particles is more likely. It is expected that the suitability for solder will deteriorate. Attempts have also been made to improve the suitability for solder by adding acids, metal salts, phenolic compounds, metal chelate forming agents and the like for the purpose of removing the oxide film of the conductive particles (see Patent Document 6). However, as a matter of course, these additions do not contribute to improving the curability of the resin itself.
JP-A-4-77547 JP-A-8-64469 JP-A-8-311304 JP-A-8-217955 JP-A-9-92031 JP-A-4-345701

  An object of the present invention is to provide a conductive paste capable of forming a layer having suitability for solder without plating, and having excellent curability in response to the above situation. It is to be.

  The present invention includes 100 parts by weight of conductive particles, 2 to 10 parts by weight of a resole type phenol-modified xylene resin, and 0.01 to 0.7 parts by weight of polyvalent carboxylic acid, and is coated with silver in the conductive particles. It is related with the electrically conductive paste whose nickel powder is 60 weight% or more.

  Moreover, this invention relates to the terminal electrode provided with the layer obtained using the said electrically conductive paste.

  According to the present invention, a conductive paste that can form a layer having suitability for solder without plating and has excellent curability is provided. When the conductive paste of the present invention is a conductive paste layer on the metal layer of the terminal electrode, in addition to good suitability for solder, it has good conduction with the internal electrode, low electrical resistance, ambient Good adhesion to the material can be expected.

  The conductive paste of the present invention contains 60% by weight or more of nickel powder containing conductive particles and coated with silver in the conductive particles. By using nickel powder coated with silver as conductive particles, compared to conventional copper powder or nickel powder coated with copper, it can be used for solder heat resistance and solder corrosion resistance. Suitability can be improved. From the viewpoint of suitability for solder, the nickel powder coated with silver in the conductive particles is preferably 75% by weight or more, and more preferably 90% by weight or more. The total amount of the conductive particles may be nickel powder coated with silver.

  In nickel powder coated with silver, silver contributes to preventing nickel oxidation and maintaining solderability and ensuring electrical conductivity inside the cured product. In addition, the adhesiveness may be lowered due to solder erosion. In the nickel powder coated with silver, the coating amount with silver is not particularly limited. However, in consideration of these circumstances, the coating amount with silver is sufficient in that both conductivity and solderability are exhibited in a sufficient and balanced manner. It is preferable that it is 5 to 20 weight% of the whole, More preferably, it is 6 to 12 weight%. Further, the shape of the nickel powder coated with silver is not particularly limited, and examples thereof include a spherical shape, a flake shape, and an indeterminate shape, but preferably a spherical shape because it is easily available. . The average particle diameter is preferably 1 μm or more, more preferably 2 to 20 μm, from the viewpoint of suppressing the amount of expensive silver covered. Specifically, it is preferable to use a spherical powder having an average particle diameter of 2 to 20 μm and a silver coating amount of 5 to 20% by weight as the nickel powder coated with silver.

  In the conductive paste of the present invention, conductive particles other than nickel powder coated with silver can be used as long as the effects of the present invention are not impaired. Specifically, silver powder, copper powder, tin powder, etc. Is mentioned. Also, nickel powder coated with copper, copper powder coated with silver, and copper-nickel alloy powder coated with silver can be used. These shapes are not particularly limited, and examples thereof include flakes, spheres, needles, and irregular shapes, and the average particle diameter is preferably 0.1 to 30 μm, more preferably 1 to 20 μm. In particular, when there is a high demand for electrical characteristics such as low electrical resistance and conduction with internal electrodes, silver powder can be contained at 0.5 to 40% by weight in the conductive particles, and more preferably 4 to 40%. It can be contained by weight%. From the viewpoint of electrical characteristics, the silver powder preferably contains scaly silver powder, and the scaly silver powder and spherical silver powder can be used in combination. In the present specification, the average particle diameter is the average of the particle diameter in the case of a sphere, the long diameter of a particle flake in the case of flakes, the length in the case of needles, and the maximum length in the case of an indefinite shape. Say.

  From the viewpoint of electrical characteristics, the conductive particles preferably include a combination of flake shaped silver powder and spherical powder, for example, as a conductive particle, a combination of flake shaped silver powder and nickel powder coated with spherical silver, Alternatively, a combination of scaly silver powder, spherical silver powder, and nickel powder coated with spherical silver can be used. In this case, the scale-like silver powder is preferably 0.5 to 10 parts by weight, more preferably 1.5 to 8 parts by weight with respect to 100 parts by weight of the spherical powder contained in the conductive particles. The flaky silver powder is preferably a flaky silver powder having an average particle diameter of 7 to 20 μm, more preferably a flaky silver powder having an average particle diameter of 10 to 18 μm.

  The conductive paste of the present invention contains a resol type phenol-modified xylene resin. By using a resol type phenol-modified xylene resin as a binder, the solder wettability can be improved.

  Examples of the resol-type phenol-modified xylene resin include a resol-type phenol-modified xylene resin obtained by reacting m-xylene with phenol and formaldehyde or reacting xylene resin with phenol. Specifically, the formula:

A resol type phenol-modified xylene resin represented by

  The conductive paste of the present invention contains a polyvalent carboxylic acid. By blending a polyvalent carboxylic acid, curability can be improved without impairing suitability for solder.

  The polyvalent carboxylic acid is not particularly limited, and may be an aliphatic carboxylic acid or an aromatic carboxylic acid. Moreover, if it is carboxylic acid more than bivalence, it will not specifically limit, Trivalent or more carboxylic acid can also be used. Examples of divalent carboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, pimelic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, malic acid, etc. Examples of the trivalent carboxylic acid include propanetricarboxylic acid, citric acid, trimellitic acid, and trimesic acid. Examples of the tetravalent carboxylic acid include benzene-1,2,3,5-tetracarboxylic acid. , Benzene-1,2,4,5-tetracarboxylic acid and the like. The polyvalent carboxylic acid may be used alone or in combination of two or more.

  In view of reactivity, a linear divalent aliphatic carboxylic acid is preferable, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid are preferable, and adipic acid and sebacic acid are particularly preferable.

  The conductive paste of the present invention contains 2 to 10 parts by weight of a resole type phenol-modified xylene resin and 0.01 to 0.7 parts by weight of a polyvalent carboxylic acid with respect to 100 parts by weight of conductive particles. By blending in this range, sufficient curability can be obtained while ensuring suitability for solder. More preferably, it contains 3 to 8 parts by weight of a resol-type phenol-modified xylene resin and 0.02 to 0.5 parts by weight of a polyvalent carboxylic acid. When the polyvalent carboxylic acid is a divalent carboxylic acid, the blending amount is more preferably 0.08 to 0.5 parts by weight. When the polyvalent carboxylic acid is a trivalent or higher carboxylic acid, the blending amount is 0.02 to 0.08. Part by weight is more preferred.

（式中、Ｒ_１は、メトキシ基であり、Ｒ_２は、直接結合又は炭素数１〜４の２価の炭化水素基である）で示される化合物を配合することが半田適性劣化の防止の点から好ましい。Ｒ_２は、直接結合、Ｃ_１〜Ｃ_４アルキレン基、Ｃ_２〜_４アルケニレン基が好ましく、より好ましくは直接結合又はビニレン基である。式（１）の化合物は、単独でも、２種以上を組み合わせて使用してもよい。 The conductive paste of the present invention has the formula (1):

(In the formula, R ₁ is a methoxy group, and R ₂ is a direct bond or a divalent hydrocarbon group having 1 to 4 carbon atoms). It is preferable from the point. R ₂ is preferably a direct bond, a C _{1 to} C ₄ alkylene group, or a C ₂ to ₄ alkenylene group, and more preferably a direct bond or a vinylene group. The compounds of formula (1) may be used alone or in combination of two or more.

  Of these, p-methoxycinnamic acid or p-methoxybenzoic acid is preferable from the viewpoint of preventing deterioration in solderability. When the curing conditions are as high as 180 ° C. or higher, or when the curing time is prolonged, p-methoxycinnamic acid is particularly preferred because it can effectively prevent the deterioration of solder suitability associated therewith.

  The compound of the formula (1) is preferably 0.05 to 5.0 parts by weight, more preferably 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the conductive particles.

  The conductive paste of the present invention can contain conventional additives as long as the effects of the present invention are not impaired. These additives include curing aids (eg hexamethylenetetramine), oxide film removers (eg lauric acid, capric acid etc.), inorganic and organic pigments, surfactants (eg sorbitan monooleate) , Silane coupling agents, titanium coupling agents (for example, titanate esters such as isopropyl triisostearoyl titanate), leveling agents, thixotropic agents, antifoaming agents, and the like. The effects of the present invention include an aluminum chelate compound such as diisopropoxy (ethylacetoacetato) aluminum; an aliphatic polycarboxylic acid ester; an unsaturated fatty acid amine salt; or a polymer compound such as a polyesteramine salt and polyamide. In the range which does not impair this, you may make it contain in the electrically conductive paste of this invention.

  The conductive paste of the present invention can be prepared to have an appropriate viscosity by blending an organic solvent. Organic solvents include aromatic hydrocarbons such as toluene, xylene, mesitylene and tetralin; ethers such as tetrahydrofuran; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone; 2-pyrrolidone, 1-methyl- Lactams such as 2-pyrrolidone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and corresponding ethers such as propylene glycol derivatives Alcohols; corresponding esters such as acetates; and dicarboxylic acids such as malonic acid and succinic acid Methyl ester, diesters, such as ethyl esters. The amount of the organic solvent used is arbitrarily selected depending on the type and amount ratio of the conductive particles and resin used, the method of printing or applying the conductive paste, and the like.

  The conductive paste of the present invention can be prepared by uniformly mixing the components by mixing means such as a raking machine, a propeller stirrer, a kneader, a roll, and a pot mill.

  The conductive paste of the present invention has good curability and can be cured by heating at 150 to 190 ° C. for 10 to 30 minutes. From the viewpoint of suppressing the influence of heat on electronic components and the like, heating at 150 to 170 ° C. for 10 to 20 minutes is preferable.

  The electrically conductive paste of this invention can be used as follows for manufacture of a terminal electrode. In chip electronic components such as chip capacitors, chip inductors, chip resistors, etc., they are printed or applied by any method such as screen printing, transfer, dip coating, etc. on the metal layer provided by sputtering, thermal spraying, sintering, etc. Curing can be performed by heating at 150 to 190 ° C. for 10 to 30 minutes. From the viewpoint of suppressing the influence of heat on electronic components and the like, heating at 150 to 170 ° C. for 10 to 20 minutes is preferable. The layer thus obtained is excellent in suitability for soldering, and functions as a terminal electrode with the metal thin film layer or the metal film layer and this layer, as in the prior art, without going through a plating process. be able to. However, the use of the conductive paste of the present invention is not limited to terminal electrode manufacture, and can be widely used in electronic component manufacture.

  Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited by these examples. In these examples, parts indicate parts by weight.

(Preparation of conductive paste)
The composition of the conductive paste used in Examples and Comparative Examples is as shown in Table 1 below. It was prepared as follows. The weighed additive and the resin were dispersed with a roll mill or the like, and the measured conductive particles were added to the resin base and dispersed with a roll mill or the like until uniform. The viscosity was adjusted to 20 to 30 Pa · s / 10 rpm (Brookfield DV-II viscometer) by diluting with a solvent as necessary.

Each characteristic was measured as follows.
[Solder wettability]
As a guide for the thickness of one Nichiban cello tape (registered trademark) (CT405AP-18) on a 20 mm square alumina substrate, each paste was applied 20 × 15 mm at a thickness of about 20 μm and cured under the conditions shown in Table 1. After curing, the cured film was heated at about 70 ° C. for about 1 minute and immersed in a flux heated to 40 ° C. for about 1 second. After the flux immersion, it was immersed in a solder bath at 235 ° C. at a speed of 3.5 mm / second and held for 6 seconds. The flux used was Senju Metal Gamma Lux 360, and the solder used was Nippon Superior's SN96CI (Sn-3.8Ag-1.0Cu). Determination of solder wettability is as follows, and the results are shown in Table 1. The conductive paste of the present invention preferably has a solder wet area of 90% or more (judgments 5, 4 and 3).
5 ... 100% solder wetting area.
4: Solder wetting area is 98% or more.
3 ... Solder wetting area 90% or more.
2 ... Solder wet area 70% or more and less than 90%.
1 ... Solder wetting area is less than 70% or solder erosion occurs.

[Shear strength]
Using a 250 mesh stainless steel screen on a 20 mm square alumina substrate, 1.5 mm square 5 × 5 block pattern printing was performed for each paste, and 3216 alumina chips were placed in 10 locations and cured under the conditions in Table 1. . After curing, the shear strength at a load rate of 12 mm / min was measured using a desktop strength tester 1605HTP (manufactured by Aiko Engineering). The results are shown in Table 1.

[Vertical conduction]
Using a 250-mesh stainless steel screen on a 20 mm square copper-clad FR4 substrate, each paste was subjected to 1.5 mm square 5 × 5 block pattern printing and cured under the conditions shown in Table 1. After curing, the resistance value between the substrate and each block pattern was measured at a temperature of 20 ± 3 ° C. and a relative humidity of 50 ± 15% by the LCR meter 4-terminal method. The results are shown in Table 1.

[Specific resistance value]
On a 20 mm square alumina substrate, a 71 mm × 1 mm zigzag pattern was printed using a 250 mesh stainless steel screen and cured under the conditions shown in Table 1. After curing, it was measured at a temperature of 20 ± 3 ° C. and a relative humidity of 50 ± 15% by the LCR meter 4-terminal method. The specific resistance value was determined from the resistance value and the thickness of the cured film. The results are shown in Table 1. The conductive paste of the present invention preferably has a specific resistance value of 1 × 10 ⁻³ or less by the above measurement.

＊６ 群栄化学工業製 レヂトップ ＰＬ２４０７ * 1 Shape: spherical, average particle size 7μm, silver coverage 10% by weight
* 2 Shape: flake, average particle size 15μm
* 3 Shape: spherical, average particle size 1.5μm
* 4 Shape: almost spherical, average particle size 7μm, copper-nickel alloy (Cu70: Ni30), silver coating amount 10% by weight
* 5 The following formula:

* 6 Gunei Chemical Industry's Resid Top PL2407

  As shown in Table 1, Comparative Example 1 containing no polyvalent carboxylic acid had low shear strength and poor electrical characteristics. Even in the case of using a polyvalent carboxylic acid, the suitability for solder was not ensured in Comparative Example 2 in which the blending amount was outside the scope of the present invention. In Comparative Example 3 in which dicyandiamide, which is a conventional curing agent, was used in place of the polyvalent carboxylic acid, the shear strength was low and the electrical characteristics were inferior. Moreover, in the comparative example 4 using a resole type phenol resin, the specific resistance value was high and the electrical characteristics were inferior. Furthermore, in Comparative Example 4 using the copper-nickel alloy powder coated with silver on the conductive particles, suitability for solder was not obtained, and the electrical characteristics were inferior.

  On the other hand, Examples 1 to 14 in Table 1 were all suitable for solder, and were excellent in shear strength and electrical characteristics. In Examples 5-6 with many compounding quantities of silver powder, it turns out that it is excellent in up-and-down conduction and specific resistance, and when the demand for an electrical property is high, the compounding of silver powder is effective. Examples 13 to 14 are examples in which the curing conditions were 180 ° C. and 20 minutes, but the suitability for the solder of Example 14 was particularly excellent, and the p-methoxycinnamic acid was added to the solder. It turns out that it is effective in maintaining aptitude.

  ADVANTAGE OF THE INVENTION According to this invention, the electroconductive paste which can form the layer suitable for solder even if it does not perform plating, and was excellent in sclerosis | hardenability is provided. When the conductive paste of the present invention is a conductive paste layer on the metal layer of the terminal electrode, in addition to good suitability for solder, it has good conduction with the internal electrode, low electrical resistance, ambient Since it can be expected to exhibit good adhesion to the material, it is highly useful in the production of various electronic components.

It is sectional drawing of the terminal electrode of the conventional chip capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Chip capacitor 2 ... Ceramic dielectric 3 ... Internal electrode 4 ... Terminal electrode 5 ... Metal layer 6 ... Nickel plating layer 7 ... Tin plating layer

Claims (11)

  100% by weight of conductive particles, 2 to 10 parts by weight of a resol-type phenol-modified xylene resin, and 0.01 to 0.7 parts by weight of polyvalent carboxylic acid, and nickel powder coated with silver in the conductive particles is 60% by weight. That is the conductive paste.   The conductive paste according to claim 1, wherein the nickel powder coated with silver is a spherical powder having an average particle diameter of 2 to 20 μm and a coating amount of silver of 5 to 20 wt%. Resole type phenol-modified xylene resin has the formula:

The electrically conductive paste of Claim 1 or 2 which is resin shown by these.   The conductive paste according to claim 1, wherein the polyvalent carboxylic acid is a divalent carboxylic acid.   The conductive paste according to claim 4, wherein the polyvalent carboxylic acid is a linear divalent aliphatic carboxylic acid.   The conductive paste according to claim 5, wherein the linear divalent aliphatic carboxylic acid is at least one selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. Furthermore, Formula (1):

(In the formula, R ₁ is methoxy group, R ₂ is a direct bond or a divalent hydrocarbon group having 1 to 4 carbon atoms) containing a compound represented by any one of claims 1 to 6 The conductive paste according to item 1.   The conductive paste according to claim 7, wherein the compound of the formula (1) is at least one selected from the group consisting of p-methoxycinnamic acid and p-methoxybenzoic acid.   The electroconductive paste of any one of Claims 1-8 in which electroconductive particle contains silver powder.   The conductive paste according to claim 9, wherein the silver powder is a flake-shaped silver powder having an average particle diameter of 7 to 20 μm, and is 0.5 to 10 parts by weight with respect to 100 parts by weight of the spherical powder contained in the conductive particles.   The terminal electrode provided with the layer obtained using the electrically conductive paste of any one of Claims 1-10.

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