JPH05128911A - Conductive paste - Google Patents

Abstract

PURPOSE:To provide conductive paste which has high conductivity and excellent adhesion with copper foil, and is usable as material for a shielding layer showing excellent electromagnetic shielding characteristic. CONSTITUTION:Conductive paste is composed of copper powder and resol type phenol resin as main components. The weight ratio of the copper powder and the solid portion of the resol type phenol resin is 80:20-90:10, and 0.2-7 parts by weight of alicyclic secondary amine and 0.1-5 parts by weight of conductivity adding additive are contained against 100 parts by weight of sum amount of the copper powder and the solid portion of the resol type phenol resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste used as a material for an electromagnetic wave shield layer of a printed wiring board.

[0002]

2. Description of the Related Art In recent years, in order to prevent radiation of electromagnetic waves to a printed wiring board, an electromagnetic wave shield printed wiring board (hereinafter referred to as a shielded wiring board) is formed by forming a shield layer made of a conductive paste on the printed wiring board. Abbreviated) is being developed. This shield wiring board is manufactured by forming a circuit pattern on a substrate by a conventional method and then sequentially forming an insulating layer, a shield layer, and an overcoat layer. At this time, the insulating layer is formed on a portion excluding a part of the ground circuit portion of the circuit pattern made of copper foil so that the shield layer and the ground circuit portion are electrically connected directly.

As a material for forming the shield layer, it has high conductivity in order to exhibit excellent electromagnetic wave shielding characteristics, and migration is required in order to ensure electric insulation between the shield layer and circuit patterns other than the ground circuit section. It is preferable to use a material that has a property that does not easily occur and that has high adhesion to the copper foil in order to secure reliability of electrical connection with the ground circuit section. Conventionally, a copper-based conductive paste containing copper powder and a resol-type phenol resin as main components has been mainly used as a material that satisfies such requirements to some extent. When improving the conductivity of the copper-based conductive paste, a saturated fatty acid, an unsaturated fatty acid, a metal salt thereof, or aminophenol is added as a conductivity-imparting aid.

[0004]

In the conventional copper-based conductive paste, the adhesion and the conductivity with the copper foil, which is a wiring circuit material, are in a mutually conflicting relationship. Conventional conductive paste, the conductivity is adjusted by adjusting the blending amount of the conductivity-imparting auxiliary agent, and when the conductivity is improved by increasing the blending amount of the conductivity-imparting auxiliary agent, with the copper foil. Adhesion tends to decrease. Therefore, the conventional copper-based conductive paste,
If the electrical conductivity is increased to a specific resistance of 10 ⁻⁴ Ω · cm or less, the adhesion with the copper foil becomes insufficient.

The present invention has been made in view of the above points, and has high conductivity and excellent adhesion to a copper foil,
It is an object of the present invention to provide a conductive paste that can be used as a material for a shield layer that can exhibit excellent electromagnetic wave shielding properties.

[0006]

The present invention is a conductive paste containing copper powder and a resole-type phenol resin as main components, wherein the weight ratio of the copper powder and the solid content of the resole-type phenol resin is 80:20. 90 to 90:10, and 0.2 to 7 parts by weight of alicyclic secondary amine and 0.1 to 5 parts by weight of conductivity based on 100 parts by weight of the total amount of the copper powder and the solid content of the resol type phenol resin. Provided is a conductive paste containing a property imparting aid.

The average particle size of the copper powder is 5 to 20 μm.
It is preferably m. This is because if the average particle size of the copper powder is less than 5 μm, it is easily oxidized and difficult to handle.
This is because if the particle size of the copper powder exceeds 20 μm, the screen may be clogged when the conductive paste is screen-printed. The shape of the copper powder may be spherical, dendritic, or scaly.

The weight ratio of the copper powder in the paste to the solid content of the resol-type phenol resin, that is, copper powder: resol-type phenol resin is set to 80:20 to 90:10, that is, the weight ratio is set to 4 to 9. To do. It has a weight ratio of 8
When the weight ratio is less than 0:20, that is, when the weight ratio is less than 4, the density of the copper powder is low, and the weight ratio exceeds 90:10.
That is, when the value of the weight ratio exceeds 9, the function of mixing the copper powder and the function of preventing the oxidation of the copper powder deteriorate, and the specific resistance increases in any case.

In the conductive paste of the present invention, a conductivity imparting aid is added to improve the conductivity. The conductivity-imparting aid is not particularly limited in its type as long as it improves conductivity by addition, for example, saturated fatty acids, unsaturated fatty acids or metal salts thereof (for example,
Stearic acid, oleic acid, palmitic acid, caprylic acid and the like, and metal salts of these with sodium, potassium, copper, zinc, aluminum and the like), aminophenol and the like can be used. These conductivity-imparting aids have poor adhesion to the copper foil if the amount added is too large, and therefore satisfy both conductivity and adhesion to the copper foil depending on the type of conductivity-imparting aid used. It is necessary to adjust such addition amount. For example, when stearic acid is used as the conductivity-imparting aid, the addition amount is 0.5 to 2 with respect to 100 parts by weight of the total amount of the copper powder and the solid content of the resol-type phenol resin.
In the case of using o-aminophenol as the conductivity-imparting aid, the addition amount is 0.5 to 3 parts by weight based on 100 parts by weight of the total amount of the copper powder and the solid content of the resol-type phenol resin. Is preferred.

As the alicyclic secondary amine, morpholine, piperidine, piperazine and the like can be used alone or in combination. Further, the addition amount thereof is set to 0.2 to 7 parts by weight with respect to 100 parts by weight of the total amount of the copper powder and the solid content of the resol type phenol resin. A shield formed by using the conductive paste obtained when the amount of the alicyclic secondary amine added is less than 0.2 parts by weight based on 100 parts by weight of the total amount of the copper powder and the resol-type phenol resin solid content. This is because it does not contribute to the improvement of the adhesiveness between the layer and the copper foil, and when it exceeds 7 parts by weight, the effect of the adhesiveness with the copper foil becomes saturated and the odor becomes strong, which is not preferable in the working environment.

The conductive paste of the present invention is used by diluting it with an organic solvent in order to obtain a viscosity suitable for printing when screen printing or the like. The organic solvent is preferably a calvete or cellosolve solvent having a high boiling point in order to prevent an increase in viscosity due to evaporation of the solvent during printing.

[0012]

In the conductive paste of the present invention, the weight ratio of the copper powder to the solid content of the resole-type phenol resin is defined, and the alicyclic secondary amine is mixed in a predetermined amount.

By prescribing the weight ratio of the copper powder and the solid content of the resol type phenol resin, when the copper powder is dispersed in the resol type phenol resin and cured by heating and mixed, the oxidation of the surface of the copper powder is prevented at the same time. It has a function to prevent the specific resistance from increasing.

By blending a predetermined amount of the alicyclic secondary amine, the hydrogen ion concentration of the conductive paste can be adjusted within the preferable range.

As a result, both high conductivity and excellent adhesion with the copper foil can be exhibited at the same time.

[0016]

EXAMPLES Examples of the present invention will be specifically described below.

Example 1 85 parts by weight of electrolytic copper powder having an average particle size of 10 μm and resol type phenol resin PL-4348 (manufactured by Gunei Chemical Co., Ltd.,
Product name) 21.4 parts by weight (15 parts by weight as solid content) is mixed to prepare a paste, and the alicyclic second
0.2 parts by weight of morpholine as a primary amine, 1.0 part by weight of stearic acid as a conductivity-imparting aid, and ethyl carbitol as a solvent were added and mixed thoroughly, and then 3
The conductive paste of Example 1 was prepared by kneading with this roll.

The electroconductivity of the obtained electroconductive paste of Example 1 and the adhesion to the copper foil were examined. The results are shown in Table 1 below.
Shown in. The conductivity was evaluated by printing the obtained conductive paste on an electrically insulating substrate using a 180-mesh screen to form a zigzag-shaped circuit pattern of 384 mm × 2 mm and applying 160 ° C. After firing for 30 minutes, the film thickness and electric resistance of the circuit pattern were measured to calculate the specific resistance. The adhesiveness was evaluated by printing the obtained conductive paste on a copper foil using a 180-mesh screen to form a solid pattern, baking this at 160 ° C. for 30 minutes, and then using a cutter knife to 1 mm. It was performed by making scratches in a grid pattern at intervals to make 100 squares, and performing a peeling test with cellophane tape to count the number of squares that were not peeled off.

Examples 2 to 8 and Comparative Examples 1 and 2 The types of alicyclic secondary amines and their addition amounts, and the types of conductivity-imparting aids and their addition amounts are as shown in Table 1 below. Example 2 is the same as Example 1 except that
8. The conductive pastes of Comparative Examples 1 and 2 were prepared.

The conductivity of the conductive pastes obtained in Examples 2 to 8 and Comparative Examples 1 and 2 and the adhesion with the copper foil were measured in Example 1
It investigated similarly to. The results are also shown in Table 1 below.

Conventional Examples 1 to 6 85 parts by weight of electrolytic copper powder having an average particle size of 10 μm and a resol type phenol resin PL-4348 (manufactured by Gunei Chemical Co., Ltd.,
(Product name) 21.4 parts by weight (15 parts by weight as solid content) are mixed to prepare a paste, and stearic acid or o-aminophenol is added to the paste as a conductivity-imparting aid as shown in Table 1 below. Ethyl carbitol was added as a solvent and mixed sufficiently, and kneaded with a three-roll mill to prepare conductive pastes of Conventional Examples 1 to 6.

The conductivity of the obtained conductive pastes of Conventional Examples 1 to 6 and the adhesion to the copper foil were examined in the same manner as in Example 1. The results are also shown in Table 1 below.

[0023]

[Table 1]

As is clear from Table 1, the conductive pastes of the present invention (Examples 1 to 8) exhibited high conductivity and excellent adhesion to copper foil.

On the other hand, the conductive paste (Comparative Example 1) containing an alicyclic secondary amine in an amount less than the range of the present invention is inferior in adhesiveness to the copper foil, and thus falls within the range of the present invention. The conductive paste (Comparative Example 2) in which an alicyclic secondary amine was blended in excess of the above adversely affected the working environment.

Further, conventional conductive pastes (conventional examples 1 to 1)
In 6), either the conductivity or the adhesion to the copper foil was poor.

[0027]

As described above, the conductive paste of the present invention has high conductivity and excellent adhesion with copper foil,
Since it can be used as a material for a shield layer that can exhibit excellent electromagnetic wave shielding properties, it has a remarkable industrial effect.

Claims (1)

[Claims] 1. A conductive paste containing copper powder and a resol-type phenol resin as main components, wherein the weight ratio of the copper powder and the solid content of the resol-type phenol resin is 80: 20-9.
0:10, 0.2 to 7 parts by weight of alicyclic secondary amine and 0.1 to 5 parts by weight of electrical conductivity, based on 100 parts by weight of the total amount of copper powder and resol-type phenol resin solids. A conductive paste containing an application aid.