JPS63228525A - Electron beam hardening type conducting 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] [Purpose of the invention] (Industrial application field) The present invention relates to an electron beam curable conductive paste.

More specifically, the present invention relates to a conductive paste that is cured by applying electron beams after coating or printing on base materials such as electronic device parts and printed wiring boards.

(Prior art) Conventionally, conductive pastes have been used to form conductor circuits in the manufacturing process of printed wiring circuits or hybrid thick film circuits, and those with low conductivity have been used to form resistive parts. is used for the purpose of

Furthermore, it is well known that this type of paste is used not only for the above-mentioned purpose of circuit formation, but also for various electronic components such as membrane switches and resistors, or for shielding electromagnetic waves. These pastes.

Since a thermosetting resin and/or an inorganic substance such as glass frit is used as a binder, it is necessary to apply it to a substrate or print it and then heat it to a high temperature to harden and bake it. However, hardening and firing requires a lot of energy and time for heating.

Not only is it uneconomical because it requires floor space for installing a heating device, but it also has major constraints as shown below. In other words, conductive pastes using inorganic substances such as glass frit as binders cannot be applied to synthetic resin base materials because they usually require firing at temperatures of 800°C or higher.
Conductive paste using a thermosetting resin binder can also be applied to synthetic resin base materials, but the base material is deformed by heating during curing of the paste. This was a major problem, as it interfered with the mounting of parts in subsequent processes.

In order to improve these drawbacks, a method has been developed in which the conductive paste is cured at or near room temperature by irradiation with active energy rays such as ultraviolet rays and electron beams.

However, conductive pastes cured by these methods generally have the disadvantage that their adhesion to the substrate is significantly reduced in environments of high temperature or high humidity, and their conductivity is also significantly reduced. .

(Problems to be Solved by the Invention) The present invention improves the various drawbacks described above, and can be cured by electron beam irradiation at or near room temperature.
An object of the present invention is to provide an electron beam-curable conductive paste that does not deteriorate in adhesion to a substrate and conductivity even under high temperature or high humidity environments after curing. In addition, the present invention can be applied to both inorganic and synthetic resin base materials, and has the same performance as a conductive paste using glass flift as a binder, which has been conventionally used for inorganic base materials. The present invention provides a line-curable conductive paste.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides: (A) a silane compound having an electron beam-reactive group; (B) a compound having one or more electron beam-reactive groups other than the above (A); An electron beam curable conductive paste comprising one or more of the following, and (C) conductive fine powder, and at least one of (B) having a hydroxyl group. It is.

In the present invention, (A) the silane compound having an electron beam-reactive group is not particularly limited, and includes divinyldimethoxysilane, divinyldi-β-methoxyethoxysilane,
Vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane.

Examples include allyltriethoxysilane.

In the present invention, (B) the compound having one or more electron beam reactive groups other than the above (A) is not particularly limited, and is diallyl orthophthalate.

Polyallyl compounds such as diallyl isophthalate.

Unsaturated polyesters, polyester poly(meth)acrylates, epoxy poly(meth)acrylates, polyurethane poly(meth)acrylates.

Polyol poly(meth)acrylates, polyether poly(meth)acrylates, divinyl compounds.

Phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylic acid alkyl ester, oligoester mono(meth)acrylate, styrene, α-alkylstyrene, etc. can be used, and among these, As a compound having a hydroxyl group, tetramethylolmethane tri(meth)
acrylate, pentaerythritol tri(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloxypropane.

2-Hydroxy-1-acroxy-3-methacryloxypropane, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2 -Hydroxypropyl (meth)acrylate, etc.

In order to further improve the adhesion between the conductive paste and the base material after electron beam curing, it is particularly preferable that at least one type of (B) has a hydroxyl group.

In the present invention, the conductive fine powder (C) is not particularly limited, and carbon black, graphite conductive metal fine powder, conductive metal oxide fine powder, or a mixture thereof can be used.

There are no particular restrictions on the carbon blank (eg, acetylene blank, furnace black, thermal black, channel black, or those obtained by graft polymerization of vinyl monomers or oxidation treatment on these).

There are no particular restrictions on graphite, including flaky graphite,
Refined natural graphite such as earthy graphite and artificial graphite are used.

There are no particular restrictions on the conductive metal fine powder, including gold and silver.

Metal fine powder made of platinum, metal, nickel, chromium, palladium, aluminum, tungsten, molybdenum, or an alloy thereof, or inorganic fine powder coated with these metals or alloys can be used.

Further, there are no particular restrictions on the metal oxide fine powder.

Fine powder of oxides such as tin, titanium, iron, etc., or a mixture thereof can be used.

The content of the conductive fine powder (C) in the conductive paste of the present invention is preferably in the range of 5 to 90% by weight.

If it is less than 5% by weight, it tends to be difficult to form a conductive path due to contact between the conductive fine powders in the conductive paste after curing, and if it exceeds 90% by weight, the conductive fine powders may not be fixed by the binder. It tends to be less effective. In the present invention, when (C) consists only of carbon black, the resulting conductive paste acts as a so-called resistance paste with relatively low conductivity after curing, and (C) is a conductive metal fine powder 2, e.g. When it is made only of silver powder, it becomes a conductive paste with high conductivity after curing.

As described above, in the present invention, a desired conductive paste can be obtained by appropriately adjusting the composition and content of type 9 (C).

The conductive paste of the present invention includes the above (A) and (B).
In addition to (C), if necessary, a thixotropic agent such as finely divided silica, as long as it does not impair its performance.
Silica, calcium carbonate, magnesium carbonate, clay,
Inorganic fillers such as talc, mica, barium sulfate, volatile solvents, adhesion improvers such as titanate compounds, etc. can be added.

Although volatile solvents can be added to the conductive paste of the present invention, removal of these volatile solvents is difficult.

The drying process can be performed at a much lower temperature than the drying process required for curing conventional thermosetting conductive pastes, for example, in a short time at room temperature.

The conductive paste of the present invention can be easily produced by mixing the above (A), (B) and (C), and then using a method 2 which is commonly used in the production of conductive pastes, such as a method using a three-roll device. be able to.

Although screen printing is the most suitable method for applying the conductive paste of the present invention to a substrate, it is also possible to use other printing and coating methods such as roller coating.

The conductive paste of the present invention is printed and painted on a base material.

When the conductive paste of the present invention contains a volatile solvent,
If necessary, the volatile solvent is removed at room temperature or by heating at a low temperature for a short time, and then it is cured by irradiation with an electron beam in air or an inert gas atmosphere. The conditions for electron beam irradiation include an accelerating voltage of 150 to 300 KV;
The absorbed dose is preferably in the range of 3 to 30 Mrad.

The conductive paste of the present invention can be put to practical use as it is after being cured by electron beam irradiation, but if necessary,
It is also possible to perform a heat aging treatment or to coat it with a paint for protection.

(Function) (A) By using a silane compound having an electron beam-reactive group, the reliability of the conductivity of the conductive paste after curing is improved, and furthermore, at least one of (B) has a hydroxyl group. The reason why the reliability of the conductivity of the cured conductive paste is further improved by setting the above-described conditions is not sufficiently clear. The resistance value of the conductive paste after curing is the sum of the resistance value of the conductive paste itself after curing and the contact resistance value between the base conductor part and the conductive paste after curing. If the adhesion between the conductive paste and the hardened conductive paste is poor, the contact resistance value will increase, and as a result, the resistance value of the hardened conductive paste will increase. In other words, the conductivity decreases, and in environments of high temperature or high humidity, the adhesiveness further decreases and the resistance value increases.

Conductivity becomes less reliable. By using (A) a silane compound having an electron beam-reactive group, and by using at least one of (B) having a hydroxyl group, the base conductor portion and the conductive paste after curing can be bonded together. It is thought that the adhesiveness of the material is increased, and the conductivity and reliability thereof are improved.

(Examples) The present invention will be explained in more detail below using Examples. In the examples, 1 part represents parts by weight.

Example I T-methacryloxypropyltrimethoxysilane 1 part Trimethylolpropane triacrylate (TMPT
A) l Q part Tris (
2~acryloyloxyethyl) isocyanurate
Part 4 Furnace Black “UK-VULCAN PJ (manufactured by CABOT,
Product name) 2.8 parts Acetylene black "Denka Black" (manufactured by Denki Kagaku Kogyo ■, trade name) 0.6 parts Graphite rPOG-10j (manufactured by Sumitomo Aluminum Smelting ■, trade name) 2.2 parts Electron of the above composition 200 m of line-curing conductive paste
Using an esh nylon screen plate, printing was carried out on a single-sided copper-clad paper phenol laminate on which a copper foil electrode portion had been previously formed by etching and polishing. The dimensions between the copper foil electrodes of the printed conductive paste were 4 dragons (vertical) and 4 (horizontal) cranes. Next, an electron beam irradiation device (Energy
150B-15 (manufactured by Science) in a nitrogen gas atmosphere with an acceleration voltage of 160 KV and an absorbed dose of 10 Mrad.
An electron beam is irradiated from the printed side of this laminate under the conditions of
The conductive paste was cured. Furthermore, a 200 mesh nylon screen plate is used on top of the hardened conductive paste to apply ultraviolet curable solder resist (Tamura Kaken).
(manufactured by USR-2B) and ultraviolet irradiation equipment (ozone-less high-pressure mercury lamp, 2 KW, 80 W/am, lamp sample distance 1 OCI 11, conveyor speed 1.0 m/
The solder resist was cured using 10 minutes). Using the laminate sample obtained in this way, the following three types of tests were conducted, and the adhesion before and after the test was evaluated by peeling off the cross-cut cellophane adhesive tape, and the resistance value before and after the test was measured. The rate of change in sheet resistance was calculated.

Solder immersion test: Molten solder bath (Tin 60/
Immerse in lead 40) for 10 seconds.

Humidity resistance test: Left for 500 hours in a constant temperature room at a temperature of 40°C and a relative humidity of 90 to 95%.

Temperature cycle test: Tabai Espec ■ constant temperature incubator P
Using L-2CP type - 40℃ 30 minutes, room temperature 15 minutes, 8
A cycle of 30 minutes at 5°C and 15 minutes at room temperature was repeated 5 times.

The sheet resistance value is determined by measuring the resistance value between the copper foil electrodes using a wide range digital ohmmeter DR-1 manufactured by Sansho Keiki Seisakusho.
The conductivity was measured using 000 CU and expressed in the unit Ω/mouth.

In addition, the resistance change rate in each test was calculated using the following formula.

Resistance change rate (X)・Resistance value before test - Resistance value after test x
Table 1 shows the resistance values obtained before 100 tests.

Example 2 Vinyltrimethoxysilane 1 part TM
PTA 8 parts Polyester diacrylate rOE-A410J (manufactured by Nippon Shokubai Chemical Co., Ltd., trade name) 8 parts 2-hydroxyethyl methacrylate 4 parts rUK-VULCAN
PJ Part 3 “Denka Blank J
Part 1 rPOG-10J
2 parts The electron beam curable conductive paste having the above composition was printed and cured in the same manner as in Example 1, and the adhesiveness and rate of change in resistance were determined and the results are shown in Table 1.

Example 3 T-methacryloxypropylmethoxysilane 1 part TMPTA 8 parts Tris(
2-Hydroxyethyl) isocyanate diacrylate 8 parts Tetrahydrofurfuryl acrylate 4 parts Silver powder rD-25J
(manufactured by Degussa Japan ■, trade name) 50 parts The electron beam curable conductive paste having the above composition was printed and cured in the same manner as in Example 1, and the adhesion and the rate of change in resistance were determined. It is shown in Table 1.

Although the resistance change rate showed a slightly large value in the humidity resistance test and the temperature cycle test, there was no problem in practical use because it was in the direction of increasing the conductivity.

Example 4 γ-methacryloxypropyltrimethoxysilane 1 part TMATA 12 parts Tris(
2-Hydroxyethyl) isocyanate diacrylate 12 parts Diaryl isophthalate 12 parts rUK-VUL
CAN PJ Part 17 “Denka Black” Part 3 rPOG-10J
14 parts carpitol acetate
30 parts of the electron beam curable conductive paste having the above composition was heated at 100°C for 2 hours after printing and before irradiation with the electron beam.
Table 1 shows the results of determining the rate of change in adhesiveness and resistance after printing and curing in the same manner as in Example 1, except that the print was dried for 0 minutes.

Example 5 Vinyltrimethoxysilane 1 part Phenoxyethyl acrylate 10 parts 2-hydroxyethyl methacrylate 10 parts rUK-V
ULCAN PJ Part 3 “Denka Black” Part 1 rPOG-10
Table 1 shows the results of determining the adhesion and the rate of change in resistance after printing and curing the electron beam curable conductive paste having the above composition in the same manner as in Example 1.

Comparative Example 1 After printing and curing in the same manner as in Example 1 except that tris(2-hydroxyethyl) L;) isocyanurate diacrylate was used instead of γ-methacryloxypropyltrimethoxysilane. Table 1 shows the results of determining the rate of change in adhesiveness and resistance.

Comparative Example 2 The same method as in Example 2 was used except that 2-hydroxyethyl methacrylate was used instead of vinyltrimethoxysilane, and the results of determining the rate of change in adhesion and resistance after printing were cured. It is shown in Table 1.

Comparative Example 3 The rate of change in adhesion and resistance after printing and curing was measured in the same manner as in Example 4, except that 2-hydroxyethyl methacrylate was used instead of γ-methacryloxypropyltrimethoxysilane. The obtained results are shown in Table 1.

Comparative Example 4 Adhesion and resistance values after printing and curing were performed in the same manner as in Example 1, except that γ-glycidoxypropyltrimethoxysilane was used instead of T-methacryloxypropyltrimethoxysilane. The results of determining the rate of change are shown in Table 1.

(Margins below) [Effects of the Invention] According to the present invention, even after being cured, there is little deterioration in adhesiveness to the base material and conductivity even if the product is kept in a high temperature or high humidity environment for a long period of time, and the quality of the product improves over time. Electron beam-curable conductive paste with high reliability can now be obtained.

Claims (1)

[Claims] 1. (A) a silane compound having an electron beam-reactive group, (B
) An electron beam-curable conductive paste comprising one or more compounds having one or more electron beam-reactive groups other than (A) above, and (C) conductive fine powder. 2. The electron beam curable conductive paste according to claim 1, wherein at least one of (B) has a hydroxyl group.