JPS5864703A - Conductive paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paste (K) that has a low electrical resistance value and is easy to handle.

For example, in a multilayer circuit wiring board with equal pressure, a conductive paste is used for interconnecting upper and lower wiring.

Conventionally, commonly used conductive pastes include silver paint, carbon paint, and Cu paint. However, conductive pastes containing these resin components have the drawbacks of high specific resistance, low allowable current, and poor heat resistance. In addition to having a high resistance value, it becomes conductive close to that of an insulator unless heat treatment is applied.
It cannot be used for circuit wiring boards that are not heat resistant. −
A conductive paste made of gallium alloy, which has good conductivity and low resistance even without heat treatment, has been proposed, but in this case, after several hours after mixing gallium and metal powder, it is possible to The problem was that the alloying reaction progressed gradually and the paste properties were lost, making handling difficult.

The present invention provides a conductive paste that solves the above-mentioned conventional problems.

Hereinafter, the conductive paste according to the present invention will be explained using the drawings.

In the present invention, as shown in FIG. 1, a liquid metal (1) mainly composed of potassium, which is liquid at room temperature, is added to a liquid metal (1) that does not react with potassium in a sufficient amount to achieve the required viscosity (that is, metal A conductive material, ie, a conductive paste (3), is formed by filling particles (2) having a surface that does not form an intermediate compound and forming a paste.

In this case, in addition to the particles 121, the liquid metal il+ contains a small amount (to the extent that it does not affect the pot life described later).
If desired, a component (4) that forms an intermetallic compound with potassium, such as Cu or N1, may be added.

As the liquid metal (1), potassium alone or potassium (Ga) and eutectic metal (Zn + Sn, In
, AQ, etc.) (Ga-Zn, Ga-Sn%Ga
-In, Ga-AQ, etc.) can be used. This solution of gallium and eutectic metal can be an appropriate amount solution, a saturated melt, or a hypercellulose infusion solution. Particles +X+ that have a surface that does not react with potassium have a viscosity adjustment function, so they need to have good wettability with gallium and good dispersibility for mixing and dispersing in potassium. 3, p
bo3. TiO2, CoO, MoO2% metal oxide powder and fiber, or Ag, Mo, CuAg
, metal powder and fibers such as AgSn, or metals on glass beads (for example, TI (however, the surface is T'1 (J2) - t, etc., NI, Cu, W, A).
etc.) can be used.

The particle size of particles (2) is preferably 5 to 200μ, or preferably 10 to 10
A range of 0μ is good. The amount of particle fraction (mainly particles (2)) is determined by the amount of liquid component (liquid gold nugget 11
1 is the main component) is 100% by volume [7 is 30-70% by volume]
If it is less than 30% by volume, the viscosity is low and the surface tension of the liquid cannot be offset, resulting in poor filling properties. When it exceeds 70%, it is difficult to form a paste.

Here, the liquid component refers to a case of potassium alone or a liquid consisting of potassium and 1m of eutectic gold (Sn, In, Zn, etc.). In addition, the particle component refers to the case of particles having a surface that is non-reactive with potassium, and the case of adding a crystal component of eutectic metal that precipitates at working temperature.
The lli lli and the particles +21 having a surface that does not react with potassium can be mixed using a vibrating mixer, a niegoo, a propeller mixer, or the like.

Since this 4W paste (3) is mainly composed of gallium, its electrical resistance is low even without heat treatment, and the alloying reaction does not occur at a working temperature of 20 to 150°C, and the period until it loses its soft viscosity is Since the ffobot life is semi-permanent, it can be easily handled as a conductive paste.

Next, one embodiment of the present invention will be described.

Example (1) A conductive paste is obtained by mixing 180 g of titanium powder with a particle size of 40/J at liquid gallium 100 °C < SO °C.

This conductive paste had the required viscosity to fill the pores at working temperatures.

Example (2) A conductive paste was prepared by mixing 100 g of titanium powder with a particle size of 4011 at 50°C into a liquid potassium-zinc alloy in which potassium 70 (wt%) and zinc 30 (wt%) were completely melted. obtain.

This conductive paste had the same viscosity as Example (1), although 15 g of zinc was deposited at an operating temperature of 50°C.

Next, an example in which the conductive paste of the present invention described above is applied to the LLI structure of a multilayer circuit board will be described with reference to FIG. First, as shown in Figure 2, a 5K insulating substrate (I+3) made of, for example, phenol resin, epoxy resin, etc., is coated with steel foil 03 on both sides, respectively, and a steel-clad laminate (l) is prepared. Next, the upper and lower steel foils Q21 of the laminate 03 are selectively etched to form the first and second wiring patterns 0 and OS on both sides of the substrate αυ, respectively.
ll position fltK both wiring patterns Q41 and α51
Through-holes H (corresponding to the respective connection parts in this case) are carefully formed (FIG. 2B and C). After that,
As shown in the second diagram, 5 is a conductive paste (3) made by mixing the above-mentioned potassium-based liquid gold [K particles with a surface that does not react with potassium] in the through hole ue.
and electrically connect both wiring patterns (+41 and (151) with this conductive paste (3). Furthermore, as shown in Fig. 2 E, the surface of the conductive paste (3) is coated with, for example, epoxy resin, Cover and seal with a top coat (protective layer) such as acrylic resin or polyester resin.

According to such a circuit wiring board, the conductive paste maintains its soft viscosity for a long time, so even if the conductive paste (3) is used for a long time, the connection part made of the conductive paste (3) will follow the bending and will not be electrically conductive. It won't damage the connection.

In the example shown in Fig. 3, the first
A wiring pattern a8 is formed, and an insulating adhesive layer α is formed thereon.
In the multilayer circuit wiring board ainc formed by forming the wiring pattern (A) of 11!2 through the wire 9, insert the second wiring pattern ■ into the hole punched at the connection part with the first wiring pattern (II). Fill with the above conductive paste (3) and
and the second wiring pattern a81 and ■ and electrically connect the conductive paste (3)! ! ! This is a case where the surface is coated with the above-mentioned top coat anK. In this multilayer circuit wiring board Qv, the first wiring pattern 08
In other words, steel (CU) from the steel foil diffuses and alloys with potassium (Ga) in the potassium-based conductive paste.
It is also possible to form a -Cu compound and partially or completely harden it.

According to the present invention described above, a conductive paste (3) having a desired viscosity, for example, the optimum viscosity for printing, K11l, is obtained by mixing particles having a surface that does not react with potassium with a liquid metal mainly composed of potassium. This conductive paste has a low electrical resistance value and does not lose its paste properties at working temperatures of 20 to 150°C. Therefore, when applied to the wiring pattern connection of a multilayer circuit wiring board, good conductivity can be obtained by printing the connection part, filling it with the above-mentioned conductive paste, and covering the surface with a topcoat. Therefore, the conductive paint (3) of the present invention is a conductive material used for through-hole conduction of a multilayer circuit wiring board,
Alternatively, it can be suitably applied to a conductive paste (K) used for a flexible circuit board (S) with a high degree of flexibility.

[Brief explanation of the drawing]

Figure m1 is a cross-sectional view showing the form of the conductive paste of the present invention,
Figure 2 is a process diagram showing an example in which the conductive paste of the present invention is applied to the production of a multilayer circuit wiring board, and Figure m3 is another example in which the conductive paste of the present invention is applied to a multilayer circuit wiring board. FIG. (1; is a liquid metal mainly composed of gallium, 12j is a particle with a surface that does not react with potassium, and (3) is a conductive paste. Fig. 1 Fig. 3 Fig. 11 15 Fig. 2

Claims (1)

[Claims] A conductive paste comprising a liquid metal mainly composed of gallium filled with particles having a surface that does not react with the gallium in an amount sufficient to adjust the liquid to a required viscosity.