JP2589433B2 - Plateable thick film copper conductor paste composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick-film copper conductor paste composition which can be plated, and more particularly to an electroless or electrolytic plating on a baked copper conductor after baking on an inorganic dielectric such as alumina. In addition, the plated inorganic dielectric and the baked copper conductor have excellent adhesion,
The present invention relates to a thick-film copper conductor paste composition that can be plated.

[0002]

2. Description of the Related Art A thick film conductor composition is a composition in which a conductive metal and an inorganic binder are dispersed in a fine powder form in an organic medium, and further, if necessary, other additives are blended. It is used as a component material for various electronic components such as hybrid circuits. The conductor is required to have electrical conductivity, solder wettability, solder dissolution resistance, adhesion to a substrate, and the like, and various additives are selectively used in accordance with the required characteristics.

A thick film conductor using copper as a conductive metal has been introduced for the purpose of reducing the cost of a thick film conductor using an expensive noble metal such as gold, silver, platinum or palladium as a conductive metal. Recently, the properties of copper itself,
In particular, attention has been paid to high-frequency characteristics, which are applied to various fields by various methods.

However, when copper is used as a conductive metal, there is an inconvenience as compared with a conventional thick film conductor using a noble metal such as gold, silver, platinum and palladium. For example, the surface of a copper-baked substrate is easily oxidized in air in the air, which may result in poor solder wettability or difficulties in wire bonding of gold wires or aluminum wires. As a measure to avoid these problems, plating that is difficult to oxidize on the copper conductor is considered,
In the conventional copper conductor paste, the adhesion between the copper conductor and the inorganic dielectric was greatly deteriorated by the plating solution at the time of plating.

In connection with this thick film copper conductor paste composition, reference is made to US Pat. No. 2,993,815 to Treptow.
The number includes "5 to 50 parts by weight of copper or copper oxide and 1 part by weight of reduction-resistant glass frit,
A conductor composition for a printed circuit, which is formed by firing at 050 ° C. in two steps to form a copper conductor layer, is disclosed by Friedman.
U.S. Pat. No. 3,674,532 to n) discloses "copper and glass compositions using lead borosilicate glass containing cadmium oxide as a binder" and U.S. Pat. No. 4,070,518 to Hoffman discloses "particularly dielectric materials. 85-97 parts by weight of copper powder used on the body, 3-15 parts by weight of Cd,
US Pat. No. 4,072,771 to Grier et al. Discloses "a conductor composition comprising Bi-free alumina borate glass frit" which discloses "a copper powder having a pre-oxidized surface and lead alumina borosilicate glass, Copper is 1 to 5 parts by weight of solids, and glass frit is 1 to 5 parts by weight of solids.
To 10 parts by weight of a conductive composition ".

Mitchell, US Pat. No. 4,182,919, discloses 86 to 97 parts by weight of copper, 1 to 7 parts by weight of copper oxide, and 1 to 7 parts by weight of a glass frit containing at least 75 parts by weight of bismuth oxide. US Patent No. 4 of Provance.
No. 322316 discloses "A conductor composition comprising 7 to 27 parts by weight of boron, 0 to 35 parts by weight of a glass frit and the balance of copper oxide", and is disclosed in Rellick U.S. Pat.
No. 23483 discloses a "conductor composition comprising copper, copper oxide, lead oxide and bismuth oxide and requiring no glass frit", and is disclosed in U.S. Pat.
No. 5,321,329 states that “Copper powder having an oxide coating and 3
A conductor composition comprising an inorganic binder having a softening point of from 00 to 700 ° C.,
Mick) et al., EP-A-0068167,
"65 to 80 parts by weight of copper, 0 to 6 parts by weight of copper oxide and Bi
And a conductor composition comprising 3 to 8 parts by weight of a low softening point glass containing no. As noted above, numerous documents are known about copper conductor compositions, none of which consider plating on copper conductors.

On the other hand, with respect to plating on a thick film paste, for example, Japanese Patent Application Laid-Open No. 56-125889 discloses that "a paste containing a Pd and Pt compound is applied on a heat-resistant insulating substrate, and after baking, Ni, Cu Or a method of forming a circuit by electroless plating of Co ", and a method of manufacturing a thick-film printed board is disclosed in JP-A-3-124091.
"A method of printing a copper paste on an alumina ceramic substrate and providing a Ni-Au layer on an electrode portion of a baked thick copper film by an electroless plating method" is disclosed.
No. 89, "A plating layer made of a substance containing Ni or Co is formed on a conductor pattern by electroless plating,
Method for Obtaining Thick Film Circuit Board ". As described above, various methods for forming a plating layer on a conductor by electroless plating have been proposed, but the composition of the copper conductor paste related to the present invention is not disclosed.

[0008] As described in detail above, a useful technique relating to a copper conductor paste composition that can be plated is not disclosed.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method for performing electroless or electrolytic plating on a baked copper conductor. It is an object of the present invention to provide a thick-film copper conductor paste composition that can be plated with less deterioration in adhesive strength between the inorganic dielectric and the inorganic dielectric.

[0010]

In order to achieve the above object, the present inventor has conducted various studies. As a result, the present inventors have found that a glass frit having a specific component is used, and that titanium oxide powder and zinc oxide powder are used in combination. Thus, a thick-film copper conductor paste composition having high adhesion strength to the inorganic dielectric material after plating was obtained.

That is, the gist of the present invention resides in a plateable thick film copper conductor paste composition comprising 70 to 95 parts by weight of an inorganic powder and 5 to 30 parts by weight of an organic vehicle having the following composition. This inorganic powder is composed of “100 parts by weight of copper powder” and “P
3-10 parts by weight of glass frit comprising bO, SiO ₂ , B ₂ O ₃ and alkali metal oxide ”,“ 0.1-3 parts by weight of titanium oxide powder ”, and“ 0.5-3 parts by weight of zinc oxide powder ” And the above-mentioned alkali metal oxides are those composed of at least one of Li ₂ O, Na ₂ O and K ₂ O.

[0012] As formulated in the inorganic matter in the glass frit, PbO50～70 parts, SiO ₂ 20 to 40 parts by weight, B ₂ O ₃ 5~15 parts by weight of one or more ones of the alkali metal oxides It is preferably from 0.5 to 10 parts by weight. Further, Al ₂ O ₃ , CaO, MgO, Zn
One or more of O, BaO and SrO can be added as needed within a range of 10 parts by weight or less.

As the titanium oxide powder, those having a rutile type, a brookite type or an anatase type structure are known, and any of these crystal structures may be used, or two or more types may be used. You can also.

The copper powder referred to in the present invention has an average particle size of 0.1.
5 to 10 μm and a tap density of 2 to 5 g / cm ³ , and the powder may be spherical, flake, or resin. Further, oxygen may be contained to such an extent that the copper powder surface is oxidized in a natural environment, and the amount is 1% by weight or less as the oxygen content in the copper powder.

The organic vehicle is obtained by dissolving ethyl cellulose, (meth) acrylic resin, polyester resin and the like in a solvent capable of dissolving resin components such as butyl carbitol acetate and terpineol.
Those commonly used in the art can be used.

The thick film copper conductor composition capable of being plated according to the present invention can be kneaded by using a stirring mixer, and then dispersed and stabilized by a three-roll mill to form a paste. This paste composition can be applied onto the inorganic dielectric by an appropriate method such as screen printing, transfer printing, dipping, or dispenser application. Next, the inorganic dielectric to which the paste is applied can be dried at a temperature of 100 to 200 ° C. and then fired in a temperature range of 850 to 1060 ° C. The firing atmosphere is preferably non-oxidizing,
An inert atmosphere such as ₂ or Ar can be employed. It is preferable that a small amount of oxygen be contained in the system in order to promote the combustion of the organic resin.

In the above-mentioned paste-forming step, in order to control the properties of the paste, a surfactant, a plasticizer and the like can be added as long as the properties of the thick-film copper conductor composition that can be plated are not impaired. is there.

Examples of the inorganic dielectric include an alumina substrate, an aluminum nitride substrate, and an enamel substrate used for a hybrid IC, a ceramic package, and the like, and a glass-ceramic substrate that can be fired at a low temperature. Further, it is possible to use ceramic capacitors, substrate materials for high-frequency applications, and ceramic substrates such as ferrite substrates.

[0019]

According to the present invention, the paste of the present invention is applied and baked on an inorganic dielectric to ensure sufficient adhesion between the inorganic dielectric and the copper conductor even after electroless plating or electrolytic plating. Thus, a reliable circuit or electrode can be obtained.

The reasons for limiting the amount of each component in the present invention are as follows. (Composition of Inorganic Powder) "Glass Frit" When the blending amount of the glass frit is less than 3 parts by weight, the adhesion to the inorganic dielectric is insufficient.
On the other hand, if the compounding amount exceeds 10 parts by weight, the glass bleeds out to the surface of the copper conductor when the inorganic dielectric coated with the copper paste is fired, and as a result, the plating metal and the surface copper of the copper conductor are not plated at the time of plating. Are not sufficiently bonded, and the adhesion is weak. "Titanium oxide powder" When the titanium oxide powder is less than 0.1 parts by weight, the adhesive strength during plating is significantly deteriorated,
If the amount of the titanium oxide powder exceeds 3 parts by weight, the adhesion between the plated metal and the copper conductor is reduced. "Zinc oxide powder" By mixing zinc oxide powder within the scope of the present invention, the same effect as titanium oxide powder can be obtained, and a synergistic effect can be expected by using both together.

(Composition of Glass Frit) "PbO" PbO is an important component that determines the softening temperature of glass. If PbO is less than 50 parts by weight, the softening temperature of glass becomes high, and the adhesion to the inorganic dielectric material becomes poor. Not enough. On the other hand, if PbO exceeds 70 parts by weight, PbO is reduced at the time of plating, leading to breakage of the glass, and the adhesion to the inorganic dielectric is deteriorated.

“SiO ₂ ” SiO ₂ has an effect of inhibiting the erosion of glass by the plating solution. For this purpose, 20 parts by weight or more is required. No longer exhibits the effect of

"B ₂ O ₃ " B ₂ O ₃ has a role as a glass flux. However, if it is too much, it tends to be eroded by the plating solution, and if it is too little, the softening temperature of the glass is raised to increase the inorganic dielectric. No effect on improving the adhesion to the body can be expected. Accordingly, B ₂ O ₃ is preferably blended 5 to 15 parts by weight.

"Alkali metal oxide" Alkali metal oxide promotes the softening point of glass and fluidization of glass. When the content is too large, the erosion by the plating solution increases. Is less likely to occur. Therefore, it is preferable to add 0.5 to 10 parts by weight. Here, Al ₂ O ₃ , CaO, MgO, ZnO, Ba
By adding O, SrO and the like in a range of 10 parts by weight or less, the same effect as the alkali metal oxide can be expected.

(Organic Vehicle) If the amount of the organic vehicle is less than 5 parts by weight with respect to 70 to 95 parts by weight of the inorganic powder, it is difficult to form a paste when forming the paste. The subsequent copper conductor becomes porous, greatly promoting the erosion of the plating solution into the copper conductor, and deteriorating the adhesion.

[0026]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

In this example, as shown in Table 1 below, two types of copper powder, A and B, were used, and three types of glass frit (C,
D, E) were used. In Table 2, the compounding amounts indicate parts by weight.

[0028]

[Table 1]

[0029]

[Table 2]

Then, the mixture prepared as shown in Table 3 below was preliminarily kneaded with a mixing stirrer, and then uniformly dispersed with a three-roll mill to prepare a paste. Each of these pastes was applied to a substrate of the material shown in the same table by each coating method described in the same table, and dried at 120 ° C. for 10 minutes. Next, each of the substrates was fired in a belt-type firing furnace under the conditions of a nitrogen atmosphere containing 5 ppm of oxygen, a peak temperature of 900 ° C., and an in-out time of 60 minutes. Then, the fired substrate was first degreased with a solvent, then subjected to alkali degreasing and pickling, and the one whose surface was cleaned was plated as shown in Table 3. In the case of electroless Ni and Au plating, the plating conditions are as follows.
The treatment is performed in an i-P-based plating bath, and the Ni content is 0.1 to 3%.
.mu.m thick and then Au
A thickness of μm was deposited. On the other hand, in the case of electrolytic plating, the cleaning step is the same as that of electroless plating, but Ni is applied in a thickness of 1 to 5 μm by barrel plating, and then solder plating is applied in a thickness of 0.5 to 2 μm. A wire was fixed to each of the substrates plated in this manner with solder, and peeled off by a peeling method to measure the strength. Table 3 shows the results. In Table 3, the blending amounts indicate parts by weight.

[0031]

[Table 3]

As is clear from Table 3, the thick-film copper conductor paste composition according to the present example has practically sufficient adhesive strength even after plating.

[0033]

According to the present invention, a thick-film copper conductor which can be plated with less deterioration of the adhesive strength between the sintered copper conductor and the inorganic dielectric even after the electroless or electrolytic plating treatment is performed. A paste composition can be provided.

Claims (3)

(57) [Claims] 1. A plateable thick film copper conductor paste composition comprising 70 to 95 parts by weight of an inorganic powder and 5 to 30 parts by weight of an organic vehicle having the following composition. The inorganic powder is “copper powder 10
0 parts by weight "and" PbO and SiO _2, B ₂ O ₃ and alkali metal oxides and glass frit 3-10 parts by weight "consisting of" 0.1 to 3 parts by weight of titanium oxide powder "" zinc oxide powder 0. 5-3 and made of parts by weight ", and the alkali metal oxides, Li ₂ O, refers to consist of one or more of Na ₂ O and K ₂ O. 2. The composition of the glass frit is PbO50 or more.
70 parts by weight, 20-40 parts by weight of SiO ₂ , B ₂ O ₃
2. The composition according to claim 1, wherein the composition is 0.5 to 10 parts by weight of 5 to 15 parts by weight of at least one of the alkali metal oxides. 3. The composition according to claim 1, wherein the titanium oxide powder has at least one of rutile type, brookite type and anatase type.