JP2000021235A - Copper-base conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve oxidation resistance and to improve conductivity by including copper powder or copper powder coated with silver and a thermosetting resin and including at least one kind of substance in an anthranilic ester group. SOLUTION: From a standpoint of conductivity, silver-plated copper powder is used as copper powder preferably. As a thermosetting resin, epoxy resin or the like is available. As to a mixing ratio between the copper powder and the resin, 75-90 wt.% of copper powder is mixed with 25-10 wt.% of resin and a setting agent. As anthranilic ester, methyl anthranilate or the like is available. A desirable ester content is 0.1-10 pts.wt. to 100 pts.wt. of conductive paste. After the surface of copper powder or copper powder coated with silver is treated with anthranilate ester and the like, the copper powder and thermosetting resin are preferably mixed together so as to form conductive paste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-based conductive paste, and more particularly, to a copper-based conductive paste that can be used for filling via holes for interlayer connection of a double-sided wiring film carrier and the production of the conductive paste. And a copper powder having a surface coated with silver.

[0002]

2. Description of the Related Art Metal powders such as gold, silver, and copper are frequently used as conductive powders used in conductive pastes in the field of electronic components, but they have advantages and disadvantages. Is an undeniable fact. That is,
The gold-based conductive paste has excellent reliability but is very expensive. The silver-based conductive paste has excellent conductivity, but is also expensive. In the case of a silver-based conductive paste, for example, when a current is applied experimentally in a humid atmosphere, a silver migration phenomenon (migration) occurs, and even during actual use, an increase in resistance and a short circuit are likely to occur. There is anxiety about this. On the other hand, the copper-based paste is inexpensive, but has a disadvantage that it is easily oxidized as compared with the above-mentioned noble metals, and it is difficult to obtain sufficient conductivity.

In consideration of the advantages and disadvantages of the metal powder and the recent emphasis on costs in the electronic component industry, a method of using silver-plated copper powder as a raw material for a conductive paste is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-69313. Have been. When this copper-plated copper powder is used, of course, although there is a corresponding effect, a conductive paste using silver-plated copper powder that is currently commercially available as a raw material is obtained, and a via hole for interlayer connection of a double-sided wiring film carrier is obtained. When filled, additional conductivity was required.

Accordingly, an object of the present invention is to provide an inexpensive copper-based conductive paste having improved oxidation resistance and, consequently, improved conductivity.

[0005]

Means for Solving the Problems As a result of investigations, the present inventors have found that anthranilate esters are contained in a copper-based conductive paste, or copper powder coated with copper or silver on the surface is replaced with anthranilate esters. It has been found that the above object can be achieved by using the material subjected to the surface treatment as a raw material of the copper-based conductive paste.

The present invention has been made based on the above findings, and comprises copper powder or copper powder coated on its surface with silver and a thermosetting resin, and further contains at least one anthranilate ester. A copper-based conductive paste is provided.

Further, the present invention is characterized in that a copper powder or silver coated on its surface is surface-treated with at least one kind of anthranilic acid ester, and the surface is coated with copper powder or silver. It provides copper powder.

Further, the present invention provides a copper-based conductive paste comprising a copper powder treated with the above-mentioned anthranilic acid ester or copper powder coated on the surface with silver and a thermosetting resin. It is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The copper powder used for the conductive paste of the present invention or the copper powder whose surface is coated with silver (hereinafter sometimes collectively referred to as copper powder) is not particularly limited, but the shape is, for example, spherical or resinous. , Scaly and the like, electrolytic copper powder, reduced copper powder obtained by reducing copper oxide, atomized copper powder, and silver-plated copper powder whose surface is coated with silver are preferably used. In particular, silver-plated copper powder is preferred from the viewpoint of conductivity.

Further, it is preferable that the particle size distribution of the copper powder contains a slightly large particle if attention is paid only to the conductivity. However, the conductive paste in the electronic component field is required to have not only the conductivity but also the fineness of printing. In view of this, it is preferable that a component having a size of 50 μm or more is not contained. In addition, when a component having a particle diameter of 0.1 μm or less is contained, such ultrafine particles have a large specific surface area, and the amount of anthranilates to be added for improving oxidation resistance increases. It is not preferable from the viewpoint of the storage stability of the paste.

The thermosetting resin used in the present invention includes, for example, epoxy resin, phenol resin, melamine resin and the like.

The mixing ratio of the above-mentioned copper powder and the thermosetting resin is such that when the copper powder is increased with an emphasis on the conductivity, the printability and adhesion deteriorate, and the emphasis is placed on the thermosetting resin with emphasis on the printability and adhesion. When it is increased, the conductivity is deteriorated. Therefore, copper powder 75-90% by weight,
The thermosetting resin and the curing agent are preferably 25 to 10% by weight.

The copper-based conductive paste of the present invention contains at least one anthranilate for improving oxidation resistance. Examples of the anthranilates include methyl anthranilate and ethyl anthranilate. However, when anthranilic acid itself is contained, a sufficient effect cannot be obtained. Although the reason is not clear, while anthranilic acid esters are liquid at room temperature, anthranilic acid is solid at room temperature (melting point: 144 to 146 ° C.), and dispersibility when added to the paste, that is, copper It is conceivable that the transfer to the powder surface is insufficient or aggregation due to poor dispersion hinders the formation of the conductive path of the copper powder.

The content of the anthranilates is preferably 0.1 to 100 parts by weight of the conductive paste.
10 to 10 parts by weight, particularly preferably 0.2 to 6 parts by weight. When the content of the anthranilates is less than 0.1 part by weight, the effect of the content is insufficient, and when the content exceeds 10 parts by weight, not only the inhibition of the formation of the conductive path but also the storage stability of the conductive paste and the printing are prevented. This is because it starts to have an adverse effect on the pot life at the time.

As described above, as a conventional technique using a so-called integral blending method in which a specific amount of a specific compounding agent is contained in a conductive paste, for example, JP-A-3-71508, JP-A-5-174612, etc. In any case, anthranilates such as methyl anthranilate and ethyl anthranilate are not contained.

In the present invention, the surface of the copper powder or copper powder coated with silver is treated with at least one of anthranilates. The shape, type, particle size and the like of the copper powder are the same as described above. Then, copper powder surface-treated with the anthranilates and a thermosetting resin are blended to form a copper-based conductive paste. The type of thermosetting resin and the mixing ratio of copper powder and thermosetting resin are the same as described above.

The amount of the anthranilates to be applied to the copper powder is preferably 0.05 to 5 parts by weight, particularly preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the conductive paste. The reason why the preferable range is different from the case where the anthranilate ester is contained in the conductive paste as described above is considered to be based on the direct surface treatment of the anthranilate ester on the copper powder.

As a conventional technique for surface-treating or coating copper powder or the like with a treating agent or a coating agent, see Japanese Patent Application Laid-Open No. 4-190.
No. 502, JP-A-5-174612 and the like, none of which is to treat or coat copper powder or the like with anthranilates.

[0019]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

Example 1 87 parts by weight of copper powder coated on the surface with silver having an average particle diameter of about 10 μm, 13 parts by weight of an epoxy resin and a curing agent, and 3 parts by weight of 1 part by weight of methyl anthranilate
This roll mill thoroughly mixed and dispersed. Next, the obtained conductive paste was applied on a polyimide tape by a screen printer to a width of 1 mm, a length of 20 cm, and a thickness of 50 μm.
m thin line was printed. After curing, the volume resistivity of the conductive paste coating film was determined, and the results are shown in Table 1.

Example 2 87 parts by weight of copper powder coated with silver having an average particle diameter of about 10 μm on the surface were introduced with methyl anthranilate from a vaporizer into a reaction vessel with nitrogen gas, and subjected to surface treatment. 0.5 parts by weight was coated.
87.5 parts by weight of the copper powder treated with this methyl anthranilate, 13 parts by weight of the same epoxy resin as in Example 1, and a hardener were thoroughly mixed and dispersed by a three-roll mill. Next, the obtained conductive paste was subjected to the same operation as in Example 1, and after curing, the volume resistivity of the conductive paste coating film was determined. The result is shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed except that methyl anthranilate was not used. After curing, the volume resistivity of the conductive paste coating film was determined. The results are shown in Table 1. Indicated.

Comparative Example 2 Example 1 was repeated except that 1 part by weight of anthranilic acid was used instead of methyl anthranilate.
After curing, the volume resistivity of the conductive paste coating film was determined, and the results are shown in Table 1.

Comparative Example 3 The same operation as in Example 1 was carried out except that 1 part by weight of a silane coupling agent (γ-glycidoxypropyltrimethoxysilane) was used instead of methyl anthranilate. The volume resistivity of the conductive paste coating film was determined, and the results are shown in Table 1.

Comparative Example 4 A total of 1 part by weight of 0.5 parts by weight of a hindered phenolic antioxidant and 0.5 part by weight of a phosphorus antioxidant was used instead of methyl anthranilate.
The same operation as in Example 1 was performed, and after curing, the volume resistivity of the conductive paste coating film was determined. The result is shown in Table 1.

[0026]

[Table 1]

As is clear from the results in Table 1, Example 1
2 are superior to Comparative Examples 1 to 4 in volume resistivity.

[0028]

The copper-based conductive paste of the present invention contains copper powder or copper powder whose surface is coated with silver as a main component, and the content or treatment amount of anthranilates is relatively small. While remaining superior to gold-based and silver-based conductive pastes,
It satisfies the properties required for a conductive paste such as improved conductivity and further printability and adhesion. That is, the copper-based conductive paste of the present invention is inexpensive and has excellent properties.

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Claims (3)

[Claims] 1. A copper-based conductive paste comprising copper powder or copper powder coated on its surface with silver and a thermosetting resin, and further comprising at least one anthranilic acid ester. 2. A copper powder or silver-coated copper powder obtained by subjecting a copper powder or silver-coated copper powder to a surface treatment with at least one kind of anthranilates. 3. A copper-based conductive paste comprising a copper powder treated with the anthranilic acid ester according to claim 2 or a copper powder having a surface coated with silver, and a thermosetting resin.