USOO6197366B1 (12) United States Patent (10) Patent No.: US 6,197,366 B1 Takamatsu (45) Date of Patent: Mar. 6, 2001 (54) METAL PASTE AND PRODUCTION 4,960,466 * 10/1990 Koplick ............................... 106/1.29 PROCESS OF METAL FILM 5,423,927 6/1995 Laurent et al. ........................ 156/64 (75) Inventor: Hideki Takamatsu, Nishinomiya (JP) FOREIGN PATENT DOCUMENTS (73) Assignee: Takamatsu Research Laboratory, g : R SE Hyogo (JP) 1-226721 * 9/1989 (JP). - 0 1-318044 * 12/1989 (JP). (*) Notice: Subject to any disclaimer, the term of this 8-77826 * 3/1996 (JP). patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days. * cited by examiner (21) Appl. No.: 09/423,476 Primary Examiner Shrive Beck (22) PCT Filed: May 6, 1997 ASSistant Examiner Michael Barr 86) PCT No.: PCT/P97/O1527 (74) Attorney, Agent, or Firm-David G. Conlin; Lisa (86) O /JP97/ Swiszcz Hazzard; Dike, Bronstein, Roberts & Cushman, S371 Date: Nov. 5, 1999 LLP S 102(e) Date: Nov. 5, 1999 (57) ABSTRACT (87) PCT Pub. No.: WO98/50601 According to the present invention, a metal paste comprising PCT Pub. Date: NOW. 12, 1998 an organo- or inorganometallic compound of a metal that is e - as a Solid at ordinary temperature and belongs to group 3 (51) Int. Cl. ............................... B05D3/02; B05D 5/12; through 15 of the periodic table, and an amino compound as C09D 5700 medium, and which exhibits coatable Viscosity, is provided. (52) U.S. Cl. ....................... 427/125; 427/123; 427/376.7; By using the metal paste, metal films of various types of 427/383.1; 106/1.23; 106/1.25; 106/1.26; metals or alloys can be formed inexpensively with an 106/1.27; 106/1.28; 106/1.29 industrially simple process and apparatus even on various (58) Field of Search ..................................... 427/123,125, types of general-purpose, inexpensive Substrates having a 427/383.1, 376.7; 106/1.05, 1.23, 1.25, low Softening point Such as a glass, plastic, film and So forth, 1.26, 1.27, 1.28, 1.29 in addition to a ceramic Substrate. In particular, the metal film can be formed easily in an ordinary pressure onto a (56) References Cited printed wiring board or a Substrate to be coated with a metal, which has a poor heat resistance. U.S. PATENT DOCUMENTS 3,904,783 9/1975 Nara et al. ............................. 427/98 15 Claims, 1 Drawing Sheet 2500 2000 500 9 1000 500 o s O 20.000 40,000 60,000 80.000 U.S. Patent Mar. 6, 2001 US 6,197,366 B1 000'08 000'09 000'0'; (()Z: O$)pqºV–3—^dD 000’0% 000| 009 0092 000? 009l„ d ) tabue Is (O)I*6T) US 6,197,366 B1 1 2 METAL PASTE AND PRODUCTION physically melt the metal particles to obtain a uniform thin PROCESS OF METAL FILM film. Consequently, only ceramic Substrates, metal Sub Strates or other Substrates having a high melting point could TECHNICAL FIELD be used for the Substrate on which the metal film is formed. The present invention relates to a metal paste and a 5 In addition, a large baking oven and peripheral facilities able production process of a metal film. More particularly, the to withstand high temperatures, and an energy Source and So present invention relates to a metal paste that is able to form forth for high-temperature baking are required to perform a metal film by low-temperature baking, and a production baking at high temperatures. process of a metal film that uses Said paste. The metal paste Consequently, if the paste baking temperature could be of the present invention is useful as the raw material of a lowered further, equipment costs could be reduced, energy metal film used for the Surface treatment, coating, demag could be Saved, and costs could be lowered. In addition, netizing and decoration of electronic materials, electronic Since it desirable to form a metal film on a general-purpose, devices and mechanical materials, etc., and in catalysis and inexpensive Substrate having a low softening point (Such as Sterilization. Moreover, it is also useful as the raw material glass or plastic etc.), it is preferable to further lower the of a metal film used in the fields of pharmaceuticals and 15 baking temperature at which metal film is formed to allow agricultural chemicals, etc. use of those Substrates. In addition, if there was a process for easily producing a In order to overcome this shortcoming, a method has been desired metal film even when metals are used directly as the proposed (organometallic (MO) method) in which inorganic base metal at present, there are many cases in which their use metal particles are first converted to an organometallic after forming into a metal film would be easier to handle and compound, coated after uniformly dissolving in a Solvent, more economical. However, Since baking at high tempera and then baked to obtain a thin, uniform metal film. For tures is required to form a metal film, the Substrate is limited example, in the case of gold, a paste method using an to materials having a high melting point. Therefore, if the organometallic compound containing Sulfur allows the for baking temperature for forming a metal film can be made mation of a uniform gold film demonstrating equal perfor lower, applications could be expanded to include general 25 mance while requiring approximately only /7 the amount of purpose, inexpensive Substrates having a low Softening point gold as compared with the thick film paste method in which (Such as glass or plastic etc.). The present invention relates fine particles of gold are kneaded into a paste. Consequently, to a metal paste for low-temperature baking that allows this in fields that use gold, production is Switching over to the wide range of applications. MO method from the conventional thick film paste method. A Synthesis method in which an organic Substance is BACKGROUND ART bonded directly to a metal to transform into an organome Metals have useful properties that are unique to each type tallic compound is typically used as a method for producing of metal. Each of these types of metals are used either alone the above-mentioned organometallic compound. In this Syn or in the form of an alloy for Surface treatment, coating, 35 thesis method, a special production method is required to demagnetizing and decorating of electronic materials, elec convert inorganic metal into an organometallic compound. tronic devices, mechanical materials and So forth, as well as In addition, since it is difficult to convert at a yield of 100% catalysis, Sterilization, and even in the fields of pharmaceu at that time, this method is more expensive than methods ticals and agricultural chemicals etc. by utilizing their using metal and Solvent. Thus, although this method can be respective characteristic performance (Such as electrical used practically in the case the base metal itself is an conductivity, resistance, Semi-conductivity, transparency, 40 expensive metal like gold, in the case of other metals, the use ionicity, corrosion resistivity, friction, light blocking, color of this method results in the cost required for the process of ing and/or metallic luster) after forming into a film by converting to an organometallic compound being higher various means on a Substrate Such as ceramicS and So forth. than the price of the metal itself. Consequently, there is a The following lists examples of technologies of the prior 45 need in industry for a metal paste that allows metal films to art used to produce metal films: (1) methods that require a be produced both inexpensively and easily. high Vacuum Such as Sputtering, and, (2) methods in which metallic ink is applied and baked Such as the thick film paste DISCLOSURE OF THE INVENTION method. The Sputtering method of (1) requires an expensive, In consideration of the above-mentioned problems, the high-vacuum and large apparatus, has poor mass 50 inventors of the present invention found that when a general productivity due to batch production, and has high produc purpose, inexpensive Solid organo- or inorganometallic tion costs. Consequently, the paste method of (2) is used compound, and not a special, expensive organometallic because of its low equipment cost and high productivity. In compound, is mixed with a general-purpose, inexpensive this method, various types of metal paste are coated onto a amino compound, it unexpectedly changes into a liquid or Substrate and baked, allowing metal films to be produced 55 mud to allow the obtaining of a coatable, Viscous metal continuously and inexpensively using a simple process and paste, thereby leading to completion of the present inven apparatuS. tion. The paste used in this thick film paste method is a A production process in which an organo- or inorgano heterogeneous Viscous liquid Simply comprising forming metallic compound can be directly formed into a paste in the various types of metal into fine particles and dispersing in a 60 form of a metalloorganic (MO) ink by adding an amino Solvent. Coating and baking this viscous liquid results in a compound to a Solid organo- or inorganometallic compound metal film in which the metal particles Simply make contact, followed by a simple means of manipulation in the form of thereby preventing the formation of a uniform film. Stirring is not known in the literature. Consequently, in the case of Silver-palladium alloy that is According to the present invention, a metal paste is most frequently used in the electronics industry, even if 65 provided which demonstrates coatable Viscosity and is com formed with the thick film paste method, it is necessary to posed of an organo- or inorganometallic compound of a bake by heating to a high temperature of about 950 C.