JPH0436903A - Copper conductive paste - Google Patents

Abstract

PURPOSE:To get copper conductive paste which is good in conductivity and low in the value of volume resistivity and also good in adhesiveness, printability, etc. by using conductive paste which contains copper powder and thermosetting resin and containing an additive selected from a group made up of N- alkylglycine, N-alkenileglycine, N-alkylbetaine, N-alkenilebetaine, amidebetaine, imidazoline and a mixture of them in the conductive paste. CONSTITUTION:The conductive paste contains copper powder and thermosetting resin and the thermosetting resin includes, for example, epoxy resin, methymine resin, phenol resin, alkyl resin, etc. Moreover, the conductive paste contains an additive selected from a group made up of N-alkylglycine, N-alkelnile glycine, N-alkylbetaine, N-alkenile betaine, amidebetaine, imidazoline and a mixture thereof. It is especially preferable that a mixing quantity of the additive is 1.0 - 5.0 parts by weight referring to 100 parts by weight of a total of copper powder and thermosetting resin.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a copper-based conductive paste, and more specifically,
The present invention relates to a copper-based conductive paste that can be used for conductor circuits on printed circuit boards, shields for boards, etc.

<Prior Art> As conductive pastes used in the field of electronic components, pastes made of noble metal powders such as gold and silver and organic binders have been known. It is used by methods such as printing and baking.

However, since noble metal powders such as gold and silver are very expensive, there is a cost problem in view of the recent emphasis on cost reduction in the electronic component industry. In addition, when a printed circuit is formed using a conductive paste using silver powder, for example, when a DC voltage is applied in a humid atmosphere, a migration phenomenon of silver occurs, which increases the resistance of the circuit and even causes a short circuit. There is a drawback.

Therefore, recently, various studies have been made to develop a conductive paste mainly composed of copper, which has the second lowest volume resistivity after silver and is cheaper than silver. The conductive paste is a mixture of copper powder and thermosetting resin, but since the copper powder is more susceptible to oxidation in the atmosphere than other precious metals, it is difficult to store, print, and When forming a circuit by heating, and furthermore when using the formed circuit, the surface of the copper powder is oxidized, the contact resistance between the copper powder particles increases, and sufficient conductivity cannot be obtained. be. Therefore, in order to solve the drawbacks of copper powder, it has been proposed to add various additives to a conductive paste composed of copper powder and resin. Examples of the additive include phosphorous acid or its derivatives in Japanese Patent Publication No. 52-24-936, Japanese Patent Publication No. 61-367
No. 96 uses anthracene or its derivatives, JP-A-57-55974 uses H1-quinone derivatives, JP-A No. 61-211378 uses unsaturated fatty acids, and JP-A No. 61-211378 uses unsaturated fatty acids. ]-14-, ],,
Patent No. 75 proposes fatty acid amides. However, although the conventional conductive pastes 1 to 1 containing the additives have excellent initial stability, they have problems with long-term stability, such as an increase in the absolute value of the volume resistivity.

<Problems to be Solved by the Invention> Therefore, the main object of the present invention is to provide a copper-based conductive paste that has excellent conductivity, low volume resistivity, and good adhesion, printability, etc. be.

<Means for Solving the Problems> According to the present invention, there is provided a conductive paste containing copper powder and a thermosetting resin, the conductive paste further comprising N-alkylglycine, N-alkenylglycine, N- A copper-based conductive paste is provided containing an additive selected from the group consisting of alkylbetaines, N-alkenylbetaines, amyl-betaines, imidazolines, and mixtures thereof.

The present invention will be explained in more detail below.

The copper powder used in the conductive paste of the present invention is not particularly limited, but includes, for example, spherical, dendritic, scale-like electrolytic copper powder, reduced copper obtained by reducing cuprous oxide, cupric oxide, etc. Preferred examples include powder, amylized powder, pulverized metal copper, and the like. The particle size of the copper powder is 0.5 to 100μ
In particular, Q is preferably in the range of 5 to 30μ. When the particle size exceeds 100 μm, problems occur in printability, and when the particle size is less than 0.5 μm, the copper powder is easily oxidized and the conductivity of the resulting coating film is undesirably reduced.

The thermosetting resin used in the conductive composition of the present invention includes:
For example, epoxy resin, melamine resin, phenolic resin,
Preferred examples include alkyd resins.

In the present invention, the blending ratio of the copper powder and the thermosetting resin is preferably 65 to 95% by weight of the copper powder, particularly preferably 75 to 90% by weight, that is, 5 to 35% by weight of the thermosetting resin, particularly preferably is preferably 10 to 25% by weight. If the blending ratio of the copper powder is less than 65% by weight, i
If the specific resistance required for an electric circuit cannot be obtained, and if it exceeds 95% by weight, the physical properties of the paste, such as printability, will deteriorate, which is undesirable.

The conductive paste of the present invention further contains N-alkylglycine, N-alkenylglycine, N-alkylbetaine, N-alkenylbetaine, amidobetaine, imidazoline, and mixtures thereof in order to prevent oxidation of the copper powder. 9 additives selected from the group consisting of: The N
- As the alkylglycine, for example, N-alkylglycine having an alkyl group having 8 to 22 carbon atoms, N-coco alkylglycine, etc., and as N-alkenylglycine, for example, N-alkylglycine having an alkenyl group having 8 to 22 carbon atoms, etc. −
Alkenylglycine, N-alkylo, ylglycine, etc., as N-alkylbetaine, have 8 to 2 carbon atoms, for example.
N-furkylbetaine having 2 alkyl groups, 5N-dimethylalkyl coconut oil betaine, N-dimethylalkyllaurylbetaine, etc., N-alkenylbetaine etc., for example, N-furkylbetaine having an alkenyl group having 8 to 22 carbon atoms.
Alkenyl betaine, N-alkyloyl betaine, etc.
Preferred examples of amidobetaine include coconut oil amide betaine and amidopropyl betaine, and examples of imidazoline include imidazoline and coconut oil imidazoline, and commercially available products can also be used. The amount of the additive is preferably 0.5 to 10 parts by weight, particularly preferably 1.0 to 5.0 parts by weight, based on the total amount of the copper powder and thermosetting resin of 3-00 parts by weight.
Parts by weight are preferred. If the amount is less than 0.5 parts by weight, various effects cannot be obtained by addition, and if the amount is less than 0.5 parts by weight,
If it exceeds 1 part by weight, it is not preferable because it will adversely affect the physical properties of the conductive paste.

The conductive paste of the present invention can be prepared, for example, by a method of mixing the copper powder, thermosetting resin, and additives with an organic solvent.

The organic solvent is a viscosity modifier for adjusting the viscosity of the conductive paste of the present invention to such a level that it can be printed, for example, on circuits, etc., and in view of its compatibility with the conductive paste and its relationship with drying speed. Preferably, it is a polyhydric alcohol or a derivative thereof. Specifically, known organic solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, etc. These can be preferably mentioned, and they can be used alone or as a mixture.

Further, when preparing the conductive paste of the present invention, it is also possible to add an antifoaming agent, a thickening agent, an anti-scaling agent, etc. as necessary.

<Effects of the Invention> Since the conductive paste of the present invention mainly contains copper and a thermosetting resin, it is cheaper in cost than conventional conductive pastes mainly composed of silver or gold. Moreover, since it contains specific additives, the paste has a low volume resistivity value and also has good adhesion, printability, etc.

<Examples> The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In addition, parts in the examples indicate parts by weight.

85 parts of atomized copper powder with an average particle size of 5 to 20μ, 15 parts of phenol resin (product name rBLS-364, manufactured by HJ Showa Kobunshi Co., Ltd., non-volatile content 60%), N-dimethylalkyl lauryl betaine (product name) Name: “Nitsan Anon BLJ”
(manufactured by NOF Corporation) and ethylene glycol monobutyl ether were mixed and dispersed in an automatic mortar for 2 hours. The resulting paste was then screen printed on a glass-epoxy substrate with a stainless steel plate of 250 meshes and an emulsion thickness of 20 μm, f@2 mm, length 368 μm.
Printing was performed to create a zigzag pattern.

After that, it was heated for 30 minutes in a constant temperature bath kept at 160 ° C.
The coating was cured. Various properties of the resulting coating film were measured by the methods shown below. The results are shown in Table 1.

(Electroconductivity of coating film) The value of the volume resistivity of the coating film after heat curing was measured using a digital multimeter.

(Adhesion of coating film) JIS K54. According to OO, 11 vertical and horizontal parallel lines that are perpendicular to each other are drawn at intervals of 1+ nm on the coating film baked on the glass fiber-reinforced epoxy resin substrate, cuts are made in the shape of the substrate, and cellophane tape is pasted on top of them. Next, when the cellophane tape was removed from the coating surface, the number of base lines of the coating film remaining on the substrate was investigated. (Printability) Screen printing was performed using the obtained conductive paste, and the ease of printing was observed and evaluated as follows.

O mark: Good conductive circuit formation.

×: Difficult to form a conductive circuit.

Examples 2-7. Ratios 1 and 2 Conductive pastes 1 to 1 were prepared in the same manner as in Example 1, except that the additives shown in Table 1 were used instead of N-dimethylalkyl lauryl betaine, and each measurement was performed. The results are shown in Table 1.

(Margin below)

Claims (1)

[Claims] A conductive paste comprising copper powder and a thermosetting resin, the conductive paste further comprising N-alkylglycine,
N-alkenylglycine, N-alkylbetaine, N-
A copper-based conductive paste comprising an additive selected from the group consisting of alkenylbetaine, amidobetaine, imidazoline and mixtures thereof.