JP2537007B2 - Copper composition for low temperature firing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive coating having good adhesion to a ferrite base material and excellent solder wettability, a method for producing the same, and a copper composition for low temperature firing which can form the coating.

[0002]

2. Description of the Related Art It is widely practiced to form a conductive coating on a base material such as an electrically insulating substrate and use it as a conductor. As one of the methods for forming such a conductive coating, there is known a method in which a copper paste containing metallic copper as a main component and containing glass frit is applied to a base material by screen printing or the like and then baked.

There are a high temperature firing method and a low temperature firing method as a method of firing the copper paste.
Since it is performed at a high temperature of up to 1000 ° C., heat resistance is required for the base material, and it is practically limited to the alumina base material.

On the other hand, the low temperature firing method carried out at 500 to 800 ° C. is advantageous from the viewpoint of selecting a base material, but since the composition contains a large amount of glass components, the obtained conductive coating can hardly be soldered. There are practical problems. Attempts have been made to add CdO, Bi ₂ O ₃ and Sb ₂ O ₃ in order to improve the solder wettability, but they are toxic, they ooze out from the pattern due to their low melting point, and they are volatile. There are drawbacks such as the fact that it contaminates the firing furnace and the fired coating.

[0005]

[0008] The present invention provides a baked film having excellent adhesiveness and solderability of a ferrite <br/> substrate and the low temperature fired copper flawless during firing, such as It is intended to provide a composition.

[0006]

The copper composition for low temperature firing of the present invention contains 100 parts by weight of a metal component consisting of metallic copper powder and nickel powder and 10 to 40 parts by weight of a glass frit having a low glass transition point. Ri Na and tungsten oxide is incorporated into the composition, and oxygen 2 a ferrite substrate
The present invention relates to a copper composition for low temperature firing under an atmosphere containing 50 ppm .

The present invention also provides a conductive material using the above composition.
The present invention relates to a coating and a method for producing the coating.

[0008] In the present invention, the metal component is a component that gives electrical conductivity to the sintered film, is a mixture of gold Shokudo powder and nickel powder <br/> end. The amount of the nickel powder is 40 wt% of the metal components below, particularly 5 to 40% by weight. The above
By blending the nickel powder , the conductivity, adhesiveness, solder wettability, solder erosion resistance and the like are further improved.

The glass frit, which acts as a binder in the fired coating, ensures the adhesion between the coating and the ferrite substrate.
Since the composition of the present invention is applied to the low-temperature firing method, the glass frit is used at least during low-temperature firing (600-
It must be softened or melted to 700 ° C.
As such a glass frit, one having a low glass transition point of 400 to 500 ° C. is preferable. If the glass transition point is too low, flow may occur during firing, and if it is too high, firing tends to be inadequate and adhesion to the ferrite substrate tends to decrease. Examples of preferable glass frits include those known as low-melting glass such as lead borosilicate glass containing lead oxide and zinc oxide, zinc borosilicate glass and lead zinc borosilicate glass. Glass frit is 100 parts of metal component (weight part , the same below)
10 to 40 parts by weight, preferably 10 to 20 parts by weight, and within this range, the fired coating has particularly excellent adhesion and solder wettability.

The composition of the present invention contains tungsten oxide in order to improve the solder wettability of the fired coating.
Tungsten oxide is not toxic, has almost no volatility in the firing temperature range, has a high melting point of 1473 ° C., and does not adversely affect the firing treatment and the firing coating. Tungsten oxide is preferably added in an amount of 0.1 to 5 parts, particularly 0.2 to 1.0 part, per 100 parts of the metal component.

The composition of the present invention is usually made into a paste and applied to a ferrite substrate. An organic vehicle is added for forming a paste. Examples of the organic vehicle include a solution of ethyl cellulose in terpineol,
A conventionally known one such as a butyl carbitol acetic acid ester solution of an acrylic acid ester resin can be used, and the amount thereof is about 30 parts with respect to 100 parts of the metal component, and is added so as to obtain a preferable printability viscosity.

The copper composition of the present invention can be applied and fired by a conventionally known method. For example, an organic vehicle is added and kneaded to form a paste, which is then applied to a ferrite base material. When patterning the fired coating, it may be applied to the ferrite substrate by, for example, a screen printing method. The film thickness is usually 8 μm to 50 μm. Fe
After being applied to the light base material, it is dried and baked. The firing temperature is as low as a peak temperature of 600 to 700 ° C. and the keeping time is 2 to 10
Do it for a minute. Firing atmosphere is preferably nitrogen atmosphere, also an organic vehicle for thermally decomposing the oxygen 2-50
ppm Ru is mixed.

[0013] coatings for example after firing is electrically conductive, Fe
It has excellent adhesion to the light base material and excellent solder wettability.

The ferrite base material has a firing temperature of 6
Those capable of withstanding a temperature of 00 to 700 ° C. are preferable .

Next, the present invention will be described based on examples, but the present invention is not limited to such examples.

Reference Example 1 The metal components shown in Table 1, tungsten oxide (WO ₃ ) and glass frit having a glass transition point of 490 ° C. were blended in the amounts shown in Table 1, ethyl cellulose solution was added, and the viscosity was 250,000 with a three-roll mill. A copper paste of cPs was obtained. This copper paste was printed by screen printing on a 93% alumina substrate to a thickness of 30 μm, and after drying, a nitrogen atmosphere (O ₂
(containing ppm) was fired at 700 ° C. for 10 minutes to obtain a conductive fired film.

The solder wettability and the adhesion to the substrate of the obtained fired coating were examined by the following methods.

The results are shown in Table 1.

(Solder wettability) After immersing the sample in a flux (R5003, manufactured by Nippon Alpha Metals Co., Ltd.), it was placed in a static solder bath (using JIS Z 3238 H60A solder) at a temperature of 230 ± 5 ° C. for 10 ± 2 seconds. Immerse and check the hiding ratio of the sample surface with solder.

◎ indicates a hiding rate of 95% or more, and ○ indicates a hiding rate of 90%
It is not on more than less than 95%, △ it is to no contrast ratio of 70% or more 9
Less than 0%, x indicates less than 70% hiding rate.

(Adhesion) The sample was pre-soldered under the condition of solder wettability evaluation,
Use a soldering iron with a temperature of 310 ± 20 ° C to measure φ0.
A 6 mm tin-plated annealed copper wire is soldered vertically to the substrate. Next, the annealed copper wire is pulled perpendicular to the substrate and the strength at peeling is recorded. Tensile speed is 10mm / min
And The measurement location is a 2 mm × 2 mm square.

[0022]

[Table 1]

[0023] Reference Example 2 except for using a glass frit having a glass transition point of 410 ° C. or 490 ° C. was prepared copper paste viscosity 250,000 cPs from in the same manner as in Reference Example 1 composition shown in Table 2, Example 1
In the same manner as above, a 96% alumina substrate was printed to have a thickness of 25 μm, dried and baked (700 ° C., keep time 5 minutes) to obtain a baked coating.

The solder wettability and adhesion of the obtained fired coating were examined in the same manner as in Reference Example 1.

The results are shown in Table 2.

[0026]

[Table 2]

Example 1 A glass frit having a glass transition point of 410 ° C. was used, and a metal component and a base material shown in Table 3 were used.
A fired film was obtained from the composition shown in Table 3 in the same manner as in Reference Example 1 except that the firing temperature was 600 ° C.

The solder wettability and adhesion of the obtained fired coating were examined in the same manner as in Reference Example 1.

The results are shown in Table 3.

[0030]

[Table 3]

[0031]

Low temperature fired copper compositions of the present invention according to the present invention can be formed safely and easily solder wettability and excellent conductivity of the fired film adhesion to the ferrite substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H05K 1/09 7511-4E H05K 1/09 Z 3/12 7511-4E 3/12 B (56) References Japanese Unexamined Patent Publication No. Sho 64-81106 (JP, A) Actual Development Sho 59-117672 (JP, U) Japanese Patent Publication Sho 43-12858 (JP, B1)

Claims (6)

(57) [Claims] 1. A composition containing 100 parts by weight of a metal component consisting of metallic copper powder and nickel powder and 10 to 40 parts by weight of a glass frit having a low glass transition point, and 0.1 to 5 parts by weight of tungsten oxide. Ferrite
A copper composition for low temperature firing for a base material . 2. A glass frit having a glass transition point of 400.
Ru to 500 ° C. der composition of claim 1. 3. Nickel powder is 5 to 40 parts by weight of metal component.
The composition according to claim 1 or 2, wherein the composition comprises% . 4. Low temperature firing according to claim 1, 2 or 3.
Copper composition in a nitrogen atmosphere containing 2 to 50 ppm of oxygen
Conductive firing on ferrite substrate at 600-700 ° C
Method of forming a protective film . 5. A ferrite base material comprising a copper composition for low temperature firing
Apply by screen printing to form a pattern,
The method according to claim 4, wherein the baking is performed . 6. A manufacturing method according to claim 4 or 5.
A conductive coating obtained by firing on a light base material .