JPS5842651A - Electrically conductive paste - Google Patents

Abstract

PURPOSE:To provide paste which can form a cured surface having excellent printability and good solder wettability and solder adherability, and is useful for a conductor part of a printed circuit of electronic parts, a terminal part of electrodes etc., by closely filling a curable resin prepolymer having a specified MW with copper powder. CONSTITUTION:A solvent is added to a mixture consisting of 5-10wt% resin (A) composed mainly of a resin prepolymer having a number-average MW of 10,000 or above capable of reticulating after curing and 95-90wt% copper powder to obtain an electrically conductive paste. An insulating substrate is printed with this paste by means of screen printing. The resin component A is reticulated to form a cured surface which is then coated with molten solder to form an electrically conductive surface. Examples of said resin components A are a mixture of an OH group-contg. prepolymer such as a phenoxy resin and an amino resin etherified with a lower alochol, and a mixture of an ultraviolet curing resin prepolymer and a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention improves printability and cures 1i
The electrical conductivity that improves the wettability of ioFi relates to the conductive yeast, and particularly to the electrically conductive yeast whose intended hardening surface is improved to improve solder adhesion and its adhesion.

This conductive yeast is a mixture of copper powder and a prepolymer of a specified curable resin. After printing on the desired substrate and curing the hardened surface, solder is melted onto the hardened surface and used as a conductive surface. Served. □Currently known conductive pastes of this type (synthetic resin prepolymers with a number average molecular weight of 100 to 2000 degrees, such as Da mitsuenol fat, melane m fat, xylene resin, alkyd m fat, and epoxy resin)
3. The resin varnish used is selected from these resins alone or in combination, depending on the purpose of use, such as the physical and chemical stability of the coating film, and a solvent. Ruru is added.

However, leveling agents that improve powder dispersibility and printability,
Some also contain additives such as antifoaming agents.

Such conductive pastes are used in applications where electrical conductivity is increased from the surface, such as in printed circuits for electrodes or conductor parts of electronic components. For example, printed layout [a hybrid integrated circuit board that combines a plate and a thick film resistor], the conductor part, the IT terminal part of the resistor, and the conductor part and electrode terminal part of the variable resistor are targeted. In recent years, there has been a marked trend toward higher performance, higher Width, smaller dimensions, and thinner dimensions of these target members, and even conductive pastes have come to be desired.

These current conductive yeasts have a metal powder loading of 70 to 70% when the mixture with prepolymer is 100% by weight.
It is only 80% by weight. Since the properties as a paste are no longer maintained, the filling volume cannot be increased beyond this value. For this reason, there is dissatisfaction with the solder adhesion of the cured surface formed by heating this paste after intaglio, and the cured surface has a drawback that it is not suitable for applications that require high electrical conductivity. be.

The present invention provides a conductive paste improved to increase the mixing ratio of metal powder, that is, a pre-polymer paste of a resin having a 111 number average molecular weight of 10,000 or more and which is to be reticulated after curing. - A mixture containing resin, which is the main component of the tube, and copper powder, which is a conductive substance and has a particle size of 101 or less and accounts for 90 to 95% by weight of the total amount including the resin content tTo, with the addition of a solvent tS. conductive yeast, and (2) 11 fats and fats as a hydroxyl group crosslinkable functional group, prepoly! - and an adenyl resin etherified with a lower alcohol such as methanol, ethanol, or butanol.

In this invention, the resin component consists only of a prepolymer having a number average molecular weight of 10,000 or more (it may also contain a building resin), and the mixture consists of a resin component and a steel powder, for example, a leveling resin. It is also possible to add antifoaming agents and antifoam additives.

In this case, the prepolymer that is the main resin component is a curable resin type O with a number average molecular weight of 10,000 or more, and it is packed with high density copper powder! While making it possible to improve the ease of printing and the solder adhesion of the cured surface. If this value is less than 10,000, it will not be possible to form a yeast-like dense filling, and the paste will lose its viscosity.
It becomes inappropriate for screen markings, etc. This prepolymer mainly has a number average molecular weight Vt of 10,000 or more, such as phenoxy resin, polybutadiene If Ml sp-
It may be a thermosetting resin such as vinyl phenol polymer or polyester resin. However, this is a pre-poly of the cape! - is made into a resin by mixing or reacting an etherified crosslinking agent with methanol, ethanol, and butanol, and curing at 80°C to 260°C. Moreover, this prepolymer has a number average molecular weight of 10,000.
The above UV-curable MTM resins, such as 1.2 polybutadiene resin, epoxy-modified acrylic resin, insiphenone, etc., may also be used. In this case, the myit portion is pre-policed! - Although there is no 1F in which a crosslinking agent is often added, a catalyst must be added separately. A hardened surface is then obtained by irradiation with ultraviolet rays.

Copper powder can be mixed so as to account for 90 to 95% of the total weight of the resin.

If the amount of copper powder mixed is less than t90 by weight, the adhesion of the hardened surface to the cured surface will not be good. If the weight exceeds 95%, the adhesion to the substrate becomes poor and the resin becomes brittle after curing. The copper powder shape is dendritic and granular.

It may be flattened like flakes, or it may have a single shape.
Alternatively, they may be used in combination. However, particle size #i-
<-Station [Considering the average particle diameter is set to be less than lOμ.

The conductive material to be printed or coated is made of resin such as phenol resin, epoxy resin, polyimide resin, polyester resin, polyethylene 11 resin, etc., or is made of resin such as phenol resin, epoxy resin, polyimide resin, or resin, glass fiber, or paper.

Is it made of non-woven fabric or fabric-assembled insulating material?

It consists of coating materials such as acrylic resins, epoxy resins, polyethylene llI4m1 capes on metals such as aluminum, iron, stainless steel, copper cladding or films, or silica, aluminum-based, al(nosilicate-based) coatings. The conductive material may be made of an inorganic insulating material.The conductive material is coated on the surface of the substrate by a method such as an EL coater, screen printing, dipping or dipping.

When the resin component is mainly a thermosetting resin, the conductive yeast is cured by raising the temperature to 80 to 250 UK in an inert gas atmosphere such as air or nitrogen. The resin component of this conductive yeast contains, for example, an etherified amino resin as a cross-sulfurizing agent, and polycitaryene M 4111, ? - When the resin is composed of a main resin such as a vinylphenol resin or a polyester resin, heating causes a condensation reaction between the crosslinking agent and the hydroxyl groups of the main resin to form a three-dimensional network structure. In this process, the copper powders are brought into contact with each other and connected 1, and in order to ensure sufficient electrical conductivity, Kii! ! The exposed surface is coated with solder. This hardened surface is solder-
Good solderability and good solder adhesion.

The reason for this is not clear, but it is thought that the interaction between the 7-mino resin as a cross-linking agent and the solder is what surpasses the soldering properties of the guests. Therefore, a good conductive surface is obtained,
For example, various mounted products [combined printed circuits] can be used.

The hardened surface of the conductive yeast is preferably coated with solder in a molten solder bath. Alternatively, solder or solder cream may be heated and melted on the hardened surface. The solder is composed of tin and lead solder, those containing silver and copper fat, and those containing only tin. It is also possible to apply a solder flux tube when coating the cured 1fK#f solder tube.

Below is II! Let's talk about examples.

11) Electrolytic copper powder with an average particle size of 1110JI [-94 parts by weight, 5 parts by weight of phenolic resin with a number average molecular weight of 1400 G as resin component and 1 part by weight of methyl etherified melane resin, combined with phenoxy resin as a solvent] Example conductive yeast was prepared by mixing 15 parts by weight of butyl carpitol acetate (15 parts by weight) using a three-roll roll.

Toshiba Kencal 1MKL-
Width 1sw total length 20a on the base material surface made of 4 epoxy resin
Print 11 patterns. Next, the ambient temperature IJiG℃
Heat and react for 1 hour. After cooling to 1 mK in the chamber, a yeast hardened surface with a thickness of 20 seconds is obtained.

(2) In the resin component, the biological prepoly-r-1r is replaced with isophthalic acid polyester having a number average molecular weight of 20,000,
Regarding the other terms, the conductive ester is formed in exactly the same manner as in the previous example.

In this example as well, a 4-stroke hardened surface is created in the same manner as in the previous example.

After applying a Fuchs tube of solder to the entire hardened surface formed in both examples, solder containing 63 tin and 0.5 copper is melted at 240° C. and adhered. The following table shows the condition of yeast, printability, and solder adhesion.

Conductive yeast (
3] is Example + 1) Kf was used and jitUil's electrolytic copper powder was 94% by weight, *5.5 parts by weight of epoxy resin with a number average molecular weight of 3800 as fat and 0.5 parts by weight of imidazole crosslinking agent. and a small amount of butylcarpitol acetate used as a solvent for epoxy resin. This is an example in which the same prepolymer as in Example (27) was applied as the resin component to 80 weight IsK of electrolytic copper powder filled with conductive 2-stroke (43if Practical Example 11) K.

The state of the yeast, printability, and solder adhesion were also evaluated in the same manner as in the examples. It shows the observation.

table

Claims (1)

[Claims] 11+ A resin component mainly consisting of a resin prepolymer having a number average molecular weight of 10,000 or more and which is to be reticulated upon curing, and a resin with a particle size of 10 μ or less as a conductive container. If a solvent is added to a mixture containing copper powder and a total weight of Q90 to 95 including the divided tubes,
-Characteristic conductive paste (2) 41 Prepoly whose fat content has hydroxyl groups as crosslinkable functional groups! -, methanol, and ethanol. The conductive paste according to claim 1, characterized in that it is made of butanol or an amino resin etherified with a lower alcohol.