JPH0153907B2 - - Google Patents

Description

[Detailed description of the invention]

This invention generally relates to inks for forming electric circuits (a general term for conductors and resistors), and specifically to inks for forming thick film resistors or conductors that can be baked in air. and its use for multilayer electrical circuit structures on porcelain coated metal substrates. It is known to those skilled in the art to use specialized inks to form thick films with various functions on suitable substrates in the manufacture of multilayer integrated circuit structures. This technique is of increasing interest in forming extremely dense multilayer circuit patterns on a variety of substrates for a wide range of applications in the electronics industry. A substrate that is significantly improved in the manufacture of such circuits is disclosed in US Pat. No. 4,256,796. Based on its oxide content, this substrate can be made of magnesium oxide (MgO) or a mixture of magnesium oxide and other oxides, barium oxide (BaO), boron trioxide (B ₂ O ₃ ) and silicon dioxide (SiO ₂ ). It is an advanced porcelain coated metal consisting of a mixture of. The preferred metal is steel, especially low carbon steel, which can also be coated with various other metals, such as copper, for example. A porcelain composition is applied to the metal core and fired to form a partially devitrified porcelain coating. This coating exhibits a very low viscosity at its initial melting point, but devitrification results in a high viscosity almost instantaneously. The coating after firing is recommended for hybrid circuits, but with a deformation temperature of at least 700°C and a deformation temperature of at least 110×10 ^-7 /°C
It has a high coefficient of thermal expansion. Although the porcelain-coated metal substrates of the above-mentioned US patent are significantly superior to known substrate materials, the only drawback is that they are not compatible or difficult to compatibility with commercially available thick film inks. The present invention provides an ink for forming electric circuits (ie, for forming conductors and resistors) that is compatible with the substrate of the above-mentioned US patent and can be baked in air. The advanced air-sinterable ink of the present invention includes barium-calcium borosilicate glass, a suitable organic medium, and a functional component, which is a resistor-forming ink (hereinafter referred to as resistor ink). In the case of ruthenium dioxide, the ink for forming a conductor (hereinafter referred to as conductor ink) is a noble metal to which bismuth oxide is added to improve soldering performance. According to the present invention, there is provided a reliable air-sinterable ink for forming electrical circuits useful for forming thick film circuits on porcelain metal circuit boards. The inks of this invention are particularly compatible with the circuit boards of the above-referenced US patents, as well as other functional air sinterable inks specifically designated for the circuit boards. It is obvious to those skilled in the art that when forming electronic circuits, it is economically advantageous for all inks to be sinterable in air rather than in an inert atmosphere such as nitrogen. The inks of this invention consist of a barium calcium borosilicate glass frit, a suitable organic medium, and one or more functional ingredients. Its functional components are, in the case of resistor inks, ruthenium dioxide and optionally a temperature coefficient of resistance modifier, and in the case of conductor inks, one or more noble metals and the soldering promoter bismuth oxide. The glass frit of the ink of this invention contains about 40 to 55% barium oxide, about 10 to 15% calcium oxide, about 14 to 25% boron trioxide, and about 13% by weight.
It is a barium calcium borosilicate glass consisting of ~23% silicon dioxide. The glass frit constitutes about 1 to 80% by weight of the air sinterable ink of this invention. The glass frit in the resistor ink is preferably about 25-80% by weight, with 50-75% by weight particularly recommended. The amount of glass frit in the conductor ink is about 1 to 15% by weight, with about 1 to 7% by weight being particularly recommended. The glass frit recommended for the resistor ink of this invention contains about 52% barium oxide and about 12% barium oxide by weight.
% of calcium oxide and about 16% of boron trioxide,
Consisting of approximately 20% silicon dioxide, the glass frit recommended for conductive inks contains approximately 52% barium oxide, approximately 12% calcium oxide, and approximately 19% by weight barium oxide.
% boron trioxide and approximately 17% silicon dioxide. The above-mentioned glass frit does not use oxides that are difficult to compatibility with the porcelain-coated metal substrate, such as lead oxide or zinc oxide, which are contained in conventional inks of this type that can be baked in air. It contains 10% by weight calcium oxide and is therefore well suited for use with new porcelain-coated metal substrates such as those described in the above-mentioned US patents, as well as other air-sinterable inks. Furthermore, since it contains the above amount of calcium oxide, it has the advantage of exhibiting a high surface tension that maintains an appropriate contact relationship with the functional component particles in the ink, and a low surface tension that allows good fluidity during firing. The functional component of the air-sinterable ink of this invention, i.e., ruthenium oxide or noble metal, is about 2 to 90%
% by weight present. The resistor ink of the present invention contains about 2 to 60% by weight of ruthenium oxide, preferably about 5 to 60% by weight.
Contains 25% by weight. The ruthenium oxide of this resistor ink is preferably of high purity and has a particle size of about 0.05 to 0.2 microns. This air-sinterable resistor ink also contains about 10% by weight of conventional resistance temperature coefficient modifiers such as manganese dioxide, cadmium oxide, cuprous oxide, etc.
It may even include. "Precious metals" used in this invention include gold, silver,
Refers to one or more metals recognized by those skilled in the art, such as platinum, palladium, rhodium, etc. Combinations of metals, such as silver and platinum, gold and platinum, silver, platinum and palladium, are also commonly used in conductive inks. All of these are used in pure metal form with the exception of rhodium, which is sometimes used in the form of commercially available resinates. The precious metal is present in the conductor ink of the present invention in an amount of about 60-90% by weight, preferably about 70-85% by weight. The conductor ink of the present invention contains about 1 to 15 weight percent bismuth oxide as a soldering promoter, preferably about 1 to 7 weight percent, either in the form of an additive powder or as part of the glass frit. The bismuth oxide and glass frit are preferably present in the conductive ink in a weight ratio of 1:3 to 3:1, preferably in equal amounts. The conductive inks of this invention optionally include a small amount, less than about 1% by weight, of a suitable oxidizing agent. The function of this additive is to provide a source of oxygen and oxidizing vapors to aid in the removal of organic media during calcination. The recommended oxidizing agent is bismuth nitrate pentahydrate, which is effective over a wide temperature range, unlike oxidizing agents that decompose at certain temperatures, resulting in rapid release of undesirable gases. The organic medium of this ink is a binder such as a cellulose derivative, especially a synthetic resin such as ethyl cellulose, polyacrylate or methacrylate, polyester, polyolefin, etc., and is generally the usual medium used in inks of the type described herein. can also be used. Recommended commercially available media include, for example, Amoco
Chemicals Corp.) to Amoco H-
Pure liquid polybdenum commercially available as Type 25, Type H-50, and Type L-100 and Dupont (EIDupont)
Polyrubutyl methacrylate, etc., commercially available from deNemours & Co.). The above resins can be used alone or in combination of two or more. Moreover, a suitable viscosity modifier can be added as necessary. The modifier may include solvents commonly used in similar inks, such as pine oil, terpineol, butyl carbinol acetate, ester alcohols available under the trademark Texanol from Texas Eastman Co., etc. or a solid material such as a castor oil derivative commercially available from NL Industries under the trademark Thixatrol. The organic medium accounts for about 8-35% by weight of the inks of this invention, preferably about 20-30% by weight for the resistor inks and about 10-25% by weight for the conductor inks. The air-sinterable ink of this invention is applied to a porcelain-coated metal plate as described in the above-referenced US patent by conventional means, such as screen printing, brushing, spraying, etc., with screen printing being preferred. This coating is then exposed to air for 100 min.
After drying at ~125℃ for about 15 minutes, in the air.
Bake at peak temperature of 850-950℃ for about 4-10 minutes. The value of this resistive film can be adjusted by laser trimming or air abrasion trimming. In addition to its excellent compatibility with the substrates and inks of the above patent, the coatings formed from the resistor inks of the present invention exhibit very good resistance temperature coefficient values, laser trimmability, current noise levels, and thermal shock. , exhibits stability against solder immersion, heat storage, load, and humidity. Additionally, coatings formed from this conductive ink exhibit excellent electrical conductivity, soldering performance, solder bleed resistance, wiring performance, and high humidity long-term exposure resistance. The invention will now be explained by way of example, but the invention is not limited to the details. In the following examples, all parts and percentages are by weight and all temperatures are in degrees Celsius, unless otherwise indicated. Example 1 A gold conductor ink was prepared with the following composition.

[Table] The composition of the glass frit is BaO51.32%,
CaO 12.51%, B ₂ O ₃ 19.42%, and SiO ₂ 16.75%.
The amount of organic medium is 0.58% ethyl cellulose, 7.90% terpineol, 3.23% butyl carbinol acetate, and texanol based on the finished ink.
1.84%, and hexatrol 0.34%. First make a solution of ethylcellulose and hexatrol with the liquid components of the vehicle, combine the media and mix first with the combined powder components by hand, then
Mixing was carried out under shear on a roll mill to obtain a smooth paste suitable for screen printing. Media was added to compensate for losses during mixing and maintain proper rheology. This ink was printed on a porcelain-coated steel plate of the type of the aforementioned US patent using a 325 mesh stainless steel screen to an emulsion thickness of approximately 25.4 microns, dried in air at 125°C for 10 minutes, and then dried in air. Peak temperature in conveyor furnace
Baking was performed at 900° C. for 4 to 6 minutes at its peak temperature. The sheet resistance of the film thus obtained is 4.5×
It was 10 ^-3 Ω/square. Example 2 A gold-platinum conductor ink was prepared by the method of Example 1 using the following composition.

[Table] The composition of the organic medium was 0.70% ethyl cellulose, 5.43% terpineol, 3.82% butyl carbinol acetate, 2.23% texanol, and 0.42% hexatrol. This ink was printed in the same manner as in Example 1, and the film obtained by baking had a sheet resistance of 60×10 ⁻³ Ω/square. Example 3 A silver palladium conductor ink was prepared by the method of Example 1 using the following composition.

[Table] The composition of the organic medium was 0.78% ethyl cellulose, 17.56% terpineol, 1.33% butyl carbinol acetate, and 0.04% hexatrol. This ink was printed in the same manner as in Example 1, and the film obtained by baking had a sheet resistance of 58×10 ⁻³ Ω/square. Example 4 A silver palladium platinum conductor ink was prepared by the method of Example 1 using the following composition.

[Table] The composition of the organic medium was 1.13% ethyl cellulose, 13.94% terpineol, 4.48% butyl carbinol acetate, and 0.15% hexatrol. This ink was printed in the same manner as in Example 1, and the sheet resistance of the film obtained by baking was 85×10 ⁻³ Ω/square. Example 5 A ruthenium resistor ink was prepared by the method of Example 1 using the following composition.

[Table] The composition of the glass frit in each case is
BaO51.59%, CaO12.58%, _{B2O3 15.62} %,
SiO ₂ was set at 20.21%. The organic medium was a 6% Texanol solution of ethyl cellulose. This ink was screen printed as in Example 1 and baked in air. First, various conductor terminals were attached for each composition and fired. The sheet resistance measured for each was as shown in the following table.

[Table] This result shows the compatibility of the resistor and conductor of the present invention.

Claims (1)

[Claims] 1. Consists of 2 to 90% by weight of functional components, 1 to 80% by weight of glass frit, and 8 to 35% by weight of organic medium, and the above functional components are used for forming resistors. is ruthenium dioxide, and when used to form a conductor, it is a combination of bismuth oxide and a noble metal, and the bismuth oxide is contained as a mixture with the noble metal or as a component in the glass. The glass frit contains 40-55% by weight of barium oxide, 10-15% by weight of calcium oxide, 14-25% by weight of boron trioxide, and 13-23% by weight of boron trioxide.
% by weight of silicon dioxide.