JPH0440802B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a thick film conductor composition for forming a conductive film with excellent adhesive strength to a ceramic substrate. [Prior Art] A thick film conductor composition includes 65 to 93% by weight of a powder of at least one of noble metals such as silver, gold, platinum, and palladium, and alloys thereof, and glass powder and/or bismuth oxide powder. A paste composition prepared by kneading 0.5 to 5% by weight with 6.5 to 30% by weight of an organic acid vehicle is applied onto a ceramic substrate by means such as screen printing, and baked at a temperature of 750 to 950°C. Precious metal and/or alloy powder is fixed onto a substrate via glass and/or bismuth oxide to form a conductive film, and is used for forming a film for bonding semiconductor elements, and for electrical circuits and It is often used for electrodes of resistors, etc. The adhesive strength of such a conductive film to the ceramic substrate is an important property, and this adhesive strength is
This can be improved by adding a small amount of Cu ₂ O. However, when a conductive film is formed using a thick film conductor composition containing CuO or Cu ₂ O, minute black spots may appear on the surface of the film. As a result of analysis, this speck was found to be copper oxide, and it was added.
It is thought that this is because the CuO and Cu ₂ O powders are not uniformly dispersed, but the presence of such spots not only has an unfavorable appearance, but also impedes solder adhesion and impedes the bonding of semiconductor single molecules. So,
A composition without the risk of spotting was desired. [Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a thick film conductor composition that does not cause copper oxide spots on the conductive film. [Means for solving the problem] In order to achieve this object, the composition of the present invention has the following features:
It is characterized in that a copper organic compound is used instead of CuO or Cu ₂ O powder, and the salt is contained in an amount of 0.2 to 5% by weight in terms of CuO. Copper organic compounds that can be used in the present invention include stearic acid, oleic acid, butyric acid, formic acid, lactic acid, lauric acid, salicylic acid, citric acid, oxalic acid, tartaric acid, naphthenic acid, octylic acid, benzoic acid, acetylacetone, etc. Examples include copper salts. These copper organic compounds are usually solid, and are added after being dissolved in a suitable organic solvent. Typical thick film compositions include organic vehicles such as
Ethyl cellulose dissolved in a solvent such as terpineol or butyl carbitol acetate is used, but the copper organic compound dissolved in this solvent may be added in a solid state. Alcohols such as ethanol and methanol, pyridine, ether, benzene, etc. may be used to dissolve organic copper compounds that do not dissolve in this solvent. If a solvent that easily evaporates is used, the solvent will evaporate and the copper organic compound will be precipitated when the composition is produced in the atmosphere, but there is no problem since the precipitated particles will be fine. In the present invention, the copper organic compound is 0.2 in terms of CuO.
It is necessary to contain up to 5% by weight. 0.2% by weight
If it is less than that, the adhesion between the fired film and the substrate will not be sufficient.
Moreover, if the content exceeds 5% by weight, the solder wettability of the fired film will decrease, and the bonding properties of semiconductor elements will decrease. A thick film conductor composition containing such a copper organic compound is applied to a ceramic substrate, and after drying,
When fired at 0.degree. C., the copper organic compound decomposes into copper oxide, but as a result of the drying, the copper organic compound is uniformly dispersed and precipitated in the dried film, so that no visible spots are formed. Furthermore, as the copper oxide is produced in a uniformly dispersed state, the distribution of the copper oxide interposed between the fired film and the ceramic substrate is also uniform, which has the effect of reducing variations in strength. [Example] Using granular gold powder with an average particle size of 2 μm, silver powder with an average particle size of 3 μm, and palladium powder with an average particle size of 0.1 μm, borosilicate glass powder with an average particle size of 3.4 μm (Pbo60, B ₂ O ₃ 10,
SiO ₂ (30% by weight each) powder and an organic acid vehicle containing 12% by weight of ethyl cellulose in a copper oxide source and terpineol were kneaded in a three-roll mill to form a paste, and the paste was mixed into a 2.5 cm square Al ₂ O _3Screen print a 10mm square pattern on the board,
After drying at 125°C for 10 minutes, the gold paste was heated to 900°C, silver-
The palladium and silver pastes were fired at 850°C, and the appearance and characteristics of the fired films were evaluated. The gold coating improves the appearance and
Bondability with Si chips, appearance of silver-palladium and silver coatings, and solder wettability were evaluated. Bondability with Si chips and solder wettability were determined by the following tests. (i) Bondability with Si chip Using a die bonder, attach a 1.5mm
After the corner Si chips were bonded, the peel strength of the Si chips was measured. This strength is 5Kg or more 〇, 2
Kg or less was marked ×, and the middle one was marked △. (ii) Solder wettability Floating the Al ₂ O ₃ substrate on the solder melt at 230℃, dropping flux onto the film, diameter 4 mm, height 2.85
Place a 60Sn/40Pb solder pellet of mm and solder.
After melting for 10 seconds and cooling, the size of the spread of the solder was measured. A diameter of 6 mm or more is marked as ○, a diameter of 5 mm or less is marked as ×, and a diameter in between is marked as △. In addition, for the evaluation of the appearance, a standard sample with no copper oxide source added was used as a standard for comparison, and those with discoloration or uneven color were rated △, and those with visible spots were rated ×,
Those that are recognized to be equivalent to the standard sample are marked as 〇. The paste composition and evaluation results of the fired film are summarized in Table 1.

【table】

[Table] Table 1 shows that adding a copper organic compound instead of CuO improves the appearance, Si chip bondability, and solder wettability; adding too much is not preferable because the appearance and solder wettability deteriorate. I understand that. [Effects of the Invention] According to the present invention, spots of copper oxide harmful to Si chip bonding and soldering are not formed, and a conductive film with excellent adhesive strength to a ceramic substrate can be formed.

Claims (1)

[Claims] 1. Elemental precious metals such as silver, gold, platinum, palladium, powder of at least one of their alloys, and glass powder and/or bismuth oxide powder,
1. A thick film conductor composition kneaded with an organic vehicle, which contains a copper organic compound in an amount of 0.2 to 5% by weight in terms of CuO.