JPH05194895A - Gold ink composition - Google Patents

Abstract

PURPOSE:To provide a gold ink compsn. excellent in transferability and capable of being fired even in an atmosphere of a low oxygen concn. and forming a dense film after being fired. CONSTITUTION:The objective compsn. comprises 4-6wt.% copolymer of isodecyl methacrylate and isobutyl methacrylate with glycidyl methacrylate, 3-5wt.% inorg. additive consisting of either glass frit alone or both of glass frit and an inorg. oxide; 78-85wt.% gold powder of 0.5 to 1mum in average particle diameter, and an org. solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition used for producing a hybrid IC, a ceramic substrate, etc., and more particularly to a gold ink composition for forming a pattern by printing and transfer.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic equipment, there is a demand for fine wiring and miniaturization of circuit boards used therein. For this reason, high-density wiring boards such as ceramic multilayer boards and hybrid ICs, which are advantageous in heat dissipation and miniaturization, are being developed, and in particular, fine wiring technology is an indispensable technology.

Conventionally, ceramic substrates and hybrid ICs
The wiring pattern is formed by directly printing an ink containing an inorganic substance such as copper and a resin vehicle on a substrate by using a screen printing method and firing the ink. Further, recently, in order to reduce the mounting area, development of COB (chip on board) technology for directly mounting an IC bare chip on a substrate is progressing, and along with this, a highly reliable gold electrode for chip mounting is required. Is becoming. Recently, it has become possible to print fine lines of gold having a width of about 50 μm on an experimental level using the screen printing method. The gold ink composition used for conventional screen printing generally uses a resin vehicle in which an ethylcellulose-based resin is dissolved in an organic solvent such as α-terpineol,
This is kneaded with gold powder and glass frit.

[0004]

However, when the conventional screen printing method and ink composition are used,
Fine lines with a width of about 50 microns or less have poor linearity, and considering the mass production level, it is only possible to print fine lines without breaks.
The limit is a 5 micron wide thin wire. Further, in conventional screen printing, narrow gap printing with a line and space of 50 microns or 50 microns is difficult because the printed ink flows out widely from the screen mesh or spills after printing.

Further, in the conventional screen printing method, printing is performed directly on the substrate. Therefore, if a printing failure occurs, it is often necessary to discard the substrate itself. That is, when the conventional screen printing method and the conventional ink composition are used, it is difficult to form a fine and narrow gap wiring pattern with a high yield. In order to form a fine and narrow-gap wiring pattern with a good yield, a method is to print the ink once on a silicone rubber sheet having releasability and solvent absorption, then check the print quality and then transfer the pattern. It is known by the author that it is effective, but with the conventional gold ink composition, the transferability from the sheet to the substrate was poor, and it was not easy to form a fine wiring pattern without disconnection with good yield. ..

Further, when a gold electrode is formed on a substrate on which a copper electrode is formed, the conventional gold ink composition is fired in air, so that there is a problem that the copper electrode is oxidized during gold firing. However, combination with a copper electrode was difficult.

The present invention solves the above-mentioned problems of the prior art, has excellent transferability that enables fine pattern printing by transfer, and has a dense film after baking and baking even in a low oxygen concentration atmosphere. The object is to provide a possible gold ink composition.

[0008]

To achieve this object, the gold ink composition of the present invention comprises a copolymer of isodecyl methacrylate, isobutyl methacrylate and glycidyl methacrylate in an amount of 4% by weight to 6% by weight. %, And 3% to 5% by weight of an inorganic additive consisting of only the glass frit or both the glass frit and the inorganic oxide.
It further comprises 78% by weight to 85% by weight of gold powder having an average particle size of 0.5 μm to 1 μm, and an organic solvent. Preferably, the inorganic additive is copper oxide. Powder and glass frit, 0.3% to 1% by weight of copper oxide powder, and 2% to 4% by weight of glass frit, and preferably isodecyl methacrylate, isobutyl methacrylate and glycidyl. The composition ratio of the copolymer with methacrylate is 50 wt% to 70 wt% of the isodecyl methacrylate, 20 wt% to 40 wt% of the isobutyl methacrylate, and the glycidyl methacrylate. Is 10% by weight.

[0009]

With the above-mentioned constitution, the gold ink composition of the present invention has sufficient tackiness to enable the printing of a fine pattern having a line width of 20 to 30 microns by transfer, and the film after firing is dense. In addition, it is possible to realize a gold ink composition that can be fired even in an atmosphere of low oxygen concentration.

For example, when a screen plate is used to print on a sheet having releasability and solvent absorbability, such as a silicone rubber sheet, the ink printed on the film absorbs the solvent. Very little sagging, and as a result, fine lines can be transferred and printed with a narrow gap. In the conventional gold ink composition, the spread of the ink becomes small due to the absorption of the solvent, but the ink is dried too much and cracks occur, or the adhesiveness is lowered, so that the transfer onto the substrate becomes difficult. On the other hand, since the gold ink composition of the present invention uses isodecyl methacrylate, which has normal tackiness, it has good transferability and is a copolymer with other resins, so the resin vehicle does not dry. However, it is in the form of a film and has a film strength such that cracks are less likely to occur.

Therefore, a sheet having a good releasability can be easily transferred onto the substrate by pressing, and even if the transfer amount of the resin vehicle is small and transferability is a little poor, the resin is thermoplastic and is heated. It is possible to transfer easily by applying pressure while performing.

Further, since the gold ink composition of the present invention uses the above-mentioned resin vehicle and gold powder having an average particle size of 1 micron or less, a fine gold film can be formed even on fine wiring having a width of 20 to 30 microns. Obtainable. Average particle size 0.
When the amount of gold powder having a particle size of 5 microns or less increases, the bubbling phenomenon such as blister generation becomes noticeable when fired at a high temperature. Therefore, this can be prevented by setting the average particle size to 0.5 micron or more. Further, by using copper oxide powder and glass frit as the inorganic additive, the adhesive strength to the alumina substrate or the like can be increased. This is because copper oxide and alumina react to form a spinel compound. Further, since the resin vehicle used in the present invention has thermal decomposability, gold wiring can be obtained even by firing in a low oxygen concentration atmosphere.

[0013]

EXAMPLE An example of the gold ink composition of the present invention will be described below. Table 1 shows the composition of the copolymer resin used.

[0014]

[Table 1]

The resins shown in (Table 1) are mixed with an organic solvent α-
The vehicle was prepared by dissolving the appropriate amount in terpineol. In addition, (Table 2) shows the composition of the prepared gold ink composition and the evaluation results.

[0016]

[Table 2]

Inks A to H are all about 50 on a screen plate having 400 mesh, emulsion thickness 10 μm, fine line width 50 μm, pitch 100 μm, and polyethylene terephthalate film as a transfer sheet.
Using a silicone rubber sheet having a silicone rubber layer of 0 micron formed thereon, screen printing was performed on the transfer sheet, and then the gold ink print pattern was transferred by heating onto an alumina substrate. Further, thereafter, this alumina substrate was placed in a nitrogen atmosphere at 800 ° C. or the oxygen doping amount was 10
Firing was performed in a low oxygen concentration atmosphere of ppm.

Next, the evaluation results of each gold ink composition will be described. Ink A, Ink B, Ink C and Ink D were good in transferability, denseness after firing, and adhesiveness (adhesive strength). Ink A, Ink B
In addition, in the ink C, the addition of the copper oxide powder was particularly effective in improving the adhesive strength. Further, the denseness of the thick gold film after firing was improved as the finer powder was used.

The ink E had a small amount of resin, and the transferability from the silicone rubber sheet to the substrate was poor.
Ink F had a large amount of resin and had good transferability, but the amount of resin was so large that the film after firing was not dense, and therefore the adhesion to the substrate was weak. The ink G is a fine powder having an average particle size of 0.3 micron.

In this case, since a very fine powder was used, swelling of the gold film occurred after firing, resulting in poor adhesive strength. Ink H had a small amount of glass frit, and the adhesive strength after firing was weak. As the glass frit amount increases, the adhesive strength increases, but on the contrary, the sheet resistance value increases, so it was not desirable to add a large amount. Also, when an ink was prepared using the resin b, similar results were obtained.

Further, the resin b has a higher adhesive force of the resin itself than the resin a, and when the resin b is used, the transfer can be performed with a lighter pressing force. It should be noted that the high-density ceramic substrate manufactured by using the ink A, the ink B, the ink C, and the ink D described above was highly reliable for the IC bare chip mounting. Further, even when the substrate on which the copper electrode was formed was re-fired at the same time as the gold thick film was fired, almost no oxidation of the copper electrode was observed.

[0022]

As described above, the ink composition of the present invention is
The copolymer of isodecyl methacrylate, isobutyl methacrylate and glycidyl methacrylate is 4 to 6% by weight, and the inorganic additive consisting of the glass frit alone or both the glass frit and the inorganic oxide is 3 to 5% by weight. % By weight, and further 78% by weight to 85% by weight of gold powder having an average particle size of 0.5 μm to 1 μm and an organic solvent, and preferably the inorganic additive is copper oxide powder. And 0.3% to 1% by weight of copper oxide powder and 2% to 4% by weight of glass frit, and preferably isodecyl methacrylate, isobutyl methacrylate and glycidyl meta. The composition ratio of the copolymer with acrylate is 50% by weight based on the isodecyl methacrylate. By using 0 wt%, 20 wt% to 40 wt% of the isobutyl methacrylate, and 10 wt% of the glycidyl methacrylate, it is possible to print using a screen plate and at the same time. It is possible to realize a gold ink composition that has excellent transferability that enables fine pattern printing by transfer, and that has a dense film after baking and that can be baked even in a low oxygen concentration atmosphere.

Claims (4)

[Claims] 1. A copolymer of isodecyl methacrylate, isobutyl methacrylate and glycidyl methacrylate of 4 wt% to 6 wt%, and an inorganic additive comprising only glass frit or both glass frit and an inorganic oxide. 3 to 5% by weight, and
A gold ink composition comprising 78% by weight to 85% by weight of a gold powder having an average particle size of 0.5 to 1 micron and an organic solvent. 2. The gold ink composition according to claim 1, wherein the inorganic additive comprises copper oxide powder and glass frit. 3. The inorganic additive comprises copper oxide powder and glass frit, wherein the copper oxide powder is 0.3% by weight to 1% by weight and the glass frit is 2% by weight to 4% by weight. Gold ink composition. 4. The composition ratio of the copolymer of isodecyl methacrylate, isobutyl methacrylate and glycidyl methacrylate is such that the isodecyl methacrylate is 50% by weight to 70% by weight and the isobutyl methacrylate is 20% to 40% by weight
And 10% by weight of the glycidyl methacrylate
The gold ink composition according to claim 1 or 2 or 3.