JPH0693307A - Thick-film copper conductor paste composition capable of being plated - Google Patents

Abstract

PURPOSE:To producers a thick-film copper conductor composition which is fixed to an inorg. dielectric by baking and then plated by inorg. powders of specified composition and an org. vehicle in a specified ratio. CONSTITUTION:70-90 pts.wt. of the inorg. powder consisting of 100 pts.wt. of copper powder, 3-10 pts.wt. of a glass frit consisting of PbO, SiO2k B2O3 and an alkali metal oxide, 0.1-3 pts.wt. of titanium oxide powder and 0.5-3 pts.wt. of zinc oxide powder and 5-30 pts.wt. of an org. vehicle are mixed to prepare a thick-film copper conductor paste composition. The alkali metal oxides are at least one kind among Li2O, Na2O and K2O, and the content is controlled to 0.5-10 pts.wt. The glass frit consists of 50-70 pts.wt. of PbO, 20-40 pts.wt. of SiO2 and 5-15 pts.wt. of B2O3. The composition thus obtained is sintered to an inorg. dielectric of alumina, etc., by baking and then electroless-plated or electroplated.

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 specifically, it can be electrolessly or electrolytically plated on the fired copper conductor after being baked on an inorganic dielectric such as alumina. In addition, the inorganic dielectric after plating and the fired 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 the form of fine powder in an organic medium and, if necessary, other additives are added. It is used as a material for various electronic components including hybrid circuits. This conductor is required to have electrical conductivity, solder wettability, solder dissolution resistance, and adhesion to a substrate, and various additives are selected and used according to the required characteristics.

A thick film conductor using copper as a conductive metal was introduced for the purpose of reducing the cost of a thick film conductor using an expensive precious metal such as gold, silver, platinum, or palladium as a conductive metal. , The characteristics of copper itself recently
In particular, high frequency characteristics have been paid attention to and applied to various fields by various methods.

However, when copper is used as a conductive metal, there is a disadvantage in comparison with conventional thick film conductors using noble metals such as gold, silver, platinum and palladium. For example, the surface of a copper-baked substrate is easily oxidized in the air, which may deteriorate solder wettability and make it difficult to wire bond gold or aluminum wires. As a measure to avoid these problems, it is conceivable to apply a plating that is difficult to oxidize on the copper conductor.
In the conventional copper conductor paste, the adhesion between the copper conductor and the inorganic dielectric material was significantly deteriorated by the plating solution during plating.

Regarding this thick film copper conductor paste composition, US Pat. No. 2,993,815 to Treptow is incorporated.
No. 5-100 parts by weight of copper or copper oxide and 1 part by weight of reduction resistant glass frit, 500-1
A conductor composition for a printed circuit, which is formed by two-step firing at 050 ° C. to form a copper conductor layer, is disclosed by Friedma.
n) U.S. Pat. No. 3,647,532 discloses "copper, glass compositions with lead borosilicate glass containing cadmium oxide as a binder", and Hoffman U.S. Pat. 85-97 parts by weight of copper powder used on the body and 3-15 parts by weight of Cd,
A conductor composition comprising a Bi-free alumina borate glass frit is disclosed, and US Pat. No. 4,072,771 to Grier et al. Describes "a surface-preoxidized copper powder and lead alumina borosilicate glass. Copper is 1 to 5 parts by weight of solid content, and glass frit is 1 of solid content.
10 parts by weight of the conductor composition "is disclosed.

Also, US Pat. No. 4,182,919 to Mitchell, states, "86-97 parts by weight of copper, 1-7 parts by weight of copper oxide and 1-7 parts by weight of a glass frit containing at least 75 parts by weight of bismuth oxide. "A conductor composition comprising" is disclosed in Provance U.S. Pat.
No. 322316 discloses "a conductor composition consisting of 7 to 27 parts by weight of boron, 0 to 35 parts by weight of glass frit, and the balance copper oxide", and U.S. Pat. No. 43 of Relic.
23483 discloses "a conductor composition consisting of copper, copper oxide, lead oxide and bismuth oxide, which does not require a glass frit", US Pat. No. 4 to Siuta et al.
No. 521329, "Copper powder with oxide coating and 3
A conductor composition comprising an inorganic binder having a softening point of 00 to 700 ° C. ”is disclosed.
mick) et al in European Patent No. 0068167
"65-80 parts by weight of copper, 0-6 parts by weight of copper oxide and Bi
A conductor composition comprising 3 to 8 parts by weight of a low softening point glass, which does not contain ". As mentioned above, many documents are known about copper conductor compositions, but none of them considers plating on copper conductors.

On the other hand, regarding plating on a thick film paste, for example, Japanese Patent Laid-Open No. 56-125889 describes "Ni, Cu after applying a paste containing a Pd, Pt compound on a heat-resistant insulating substrate and firing it. Or a method of forming a circuit by electroless plating of Co ", and also relates to a method of manufacturing a thick film printed circuit board.
"A method of printing a copper paste on an alumina ceramic substrate and providing a Ni-Au layer on an electrode portion of a fired copper thick film by an electroless plating method" is further disclosed.
No. 89, "A plating layer made of a substance containing Ni or Co is formed on the conductor pattern by electroless plating,
A method of obtaining a thick film circuit board "is disclosed. Thus, 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.

As detailed above, there is no disclosure of a useful technique relating to a copper conductor paste composition which can be plated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to perform electroless or electrolytic plating treatment on a fired copper conductor. It is intended to provide a thick film copper conductor paste composition which can be plated with an inorganic dielectric material with less deterioration in adhesive strength.

[0010]

In order to achieve the above object, the present inventor has conducted various studies, and as a result, uses a glass frit having a specific component and further using a titanium oxide powder and a zinc oxide powder in combination. Thus, a thick film copper conductor paste composition having a high adhesive strength with the plated inorganic dielectric has been obtained.

That is, the gist of the present invention is a thick film copper conductor paste composition which can be plated and which comprises 70 to 95 parts by weight of an inorganic powder having the following composition and 5 to 30 parts by weight of an organic vehicle. This inorganic powder contains "100 parts by weight of copper powder" and "P
Glass frit composed of bO, SiO ₂ , B ₂ O ₃ and alkali metal oxide ₃ to 10 parts by weight, “titanium oxide powder 0.1 to 3 parts by weight” and zinc oxide powder 0.5 to 3 parts by weight. The above-mentioned alkali metal oxide means one composed of at least one of Li ₂ O, Na ₂ O and K ₂ O.

The blending of each inorganic substance in the glass frit is one or more of PbO 50 to 70 parts by weight, SiO ₂ 20 to 40 parts by weight, B ₂ O ₃ 5 to 15 parts by weight and alkali metal oxides. It is preferably 0.5 to 10 parts by weight. Furthermore, Al ₂ O ₃ , CaO, MgO, Zn
One or more of O, BaO, and SrO can be added within the range of 10 parts by weight or less, if necessary.

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

The copper powder referred to in the present invention has an average particle size of 0.
The powder shape is 5 to 10 μm and the tap density is 2 to 5 g / cm ³ , and the powder shape may be spherical, flake or resin. Further, oxygen may be contained to such an extent that the surface of the copper powder is oxidized under a natural environment, and the amount thereof is 1% by weight or less as the oxygen content in the copper powder.

The organic vehicle refers to one obtained by dissolving ethyl cellulose, (meth) acrylic resin, polyester resin or the like in a solvent capable of dissolving a resin component such as butyl carbitol acetate or terpineol,
What is generally used in this industry can be used.

The plateable thick film copper conductor composition of 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 a suitable method such as screen printing, transfer printing, dipping, or dispenser application. Then, the paste-applied inorganic dielectric can be dried at a temperature of 100 to 200 ° C. and then fired within a temperature range of 850 to 1060 ° C. The firing atmosphere is preferably non-oxidizing and N
An inert atmosphere such as ₂ or Ar can be employed. In addition, it is preferable that a small amount of oxygen is contained in the system in order to promote combustion of the organic resin.

In the pasting step, in order to control the properties of the paste, it is possible to add a surfactant, a plasticizer or the like as long as the characteristics of the thick film copper conductor composition which can be plated are not impaired. is there.

Examples of the inorganic dielectrics include alumina substrates, aluminum nitride substrates, enamel substrates used in hybrid ICs and ceramic packages, and glass-ceramic substrates that can be fired at low temperatures. Furthermore, it is possible to use a ceramic capacitor, a substrate material for high frequency applications, or a ceramic substrate such as a ferrite substrate.

[0019]

According to the present invention, the paste of the present invention is applied and fired on the inorganic dielectric so that the adhesiveness between the inorganic dielectric and the copper conductor is sufficiently secured even after electroless plating or electrolytic plating. It is possible to obtain a reliable circuit or electrode.

The reasons for limiting the blending amount of each component in the present invention are as follows. (Composition of inorganic powder) "Glass frit" When the amount of glass frit is less than 3 parts by weight, the adhesion with the inorganic dielectric is insufficient,
On the other hand, if the blending amount exceeds 10 parts by weight, the glass bleeds out on the surface of the copper conductor when firing the inorganic dielectric material coated with the copper paste, and as a result, the plated metal and the surface copper of the copper conductor during plating. Does not bond well, resulting in poor adhesion. "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 titanium oxide powder exceeds 3 parts by weight, the adhesion between the plated metal and the copper conductor will deteriorate. “Zinc oxide powder” By blending 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 in combination.

(Composition of glass frit) "PbO" PbO is an important component for determining the softening temperature of glass, and when PbO is less than 50 parts by weight, the softening temperature of glass becomes high and the adhesion to the inorganic dielectric is high. Will not be enough. On the other hand, if the amount of PbO exceeds 70 parts by weight, PbO is reduced at the time of plating, which leads to breakage of the glass and the adhesion with the inorganic dielectric is deteriorated.

[SiO ₂ ] SiO ₂ has the effect of stopping the erosion of the glass by the plating solution, and for that purpose, 20 parts by weight or more is necessary, but if it exceeds 40 parts by weight, the softening point becomes too high and the glass becomes glass. No longer shows the effect of.

"B ₂ O ₃ " B ₂ O ₃ has a role as a flux for glass, but if it is too much, it is easily corroded by the plating solution, and if it is too little, the softening temperature of the glass is raised to increase the inorganic dielectric. The effect of improving the adhesion to the body cannot be expected. Therefore, it is preferable to add 5 to 15 parts by weight of B ₂ O ₃ .

"Alkali Metal Oxide" Alkali metal oxide promotes the softening point of glass and the fluidization of glass, but if too much, corrosion by the plating solution becomes large, and if too little, fluidization of glass occurs. Is less likely to occur. Therefore, it is preferable to add 0.5 to 10 parts by weight. Al ₂ O ₃ , CaO, MgO, ZnO, Ba
By adding O and SrO in the range of 10 parts by weight or less, the same effect as that of 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 prepare a paste when forming the paste, while if the amount of the organic vehicle exceeds 30 parts by weight, it is baked. The subsequent copper conductor becomes porous, which greatly promotes the erosion of the plating solution to the copper conductor and deteriorates 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 powders A and B were used, and three types of glass frit (C,
D, E) were used. In Table 2, the blending amount is part by weight.

[0028]

[Table 1]

[0029]

[Table 2]

Then, a mixture prepared as shown in Table 3 below was pre-kneaded by a mixing stirrer and then uniformly dispersed by a three-roll mill to prepare a paste. Each of these pastes was applied to a substrate made of the material shown in the table by each coating method described in the 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 alkali degreased and pickled, and the surface-cleaned one was plated as shown in Table 3. In the case of electroless Ni and Au plating, the plating condition is N after performing activation treatment with a Pd solution in advance.
Treatment in an iP type plating bath to add Ni to 0.1-3
to a thickness of μm, and then add 0.01 to 0.1 of Au.
It was deposited in a thickness of μm. On the other hand, in the case of electrolytic plating, the washing process is the same as that in electroless plating, but Ni was deposited by a barrel plating method to a thickness of 1 to 5 μm, and then solder plating was applied to a thickness of 0.5 to 2 μm. The wire was fixed to each of the substrates thus plated with solder, and the peeling strength was measured by the peel method. The results are shown in Table 3. In Table 3, the blending amount is part by weight.

[0031]

[Table 3]

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

[0033]

EFFECTS OF THE INVENTION According to the present invention, a thick film copper conductor which can be plated with little deterioration in adhesive strength with an inorganic dielectric even after electroless plating or electrolytic plating is performed on a fired copper conductor. A paste composition can be provided.

Claims (3)

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