Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1635—Composition of the substrate
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/17—Metallic particles coated with metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/18—Non-metallic particles coated with metal
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1655—Process features
  • C23C18/1658—Process features with two steps starting with metal deposition followed by addition of reducing agent
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
  • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
  • C23C18/1837—Multistep pretreatment
  • C23C18/1844—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/42—Coating with noble metals
  • C23C18/44—Coating with noble metals using reducing agents

Definitions

• This invention relates to a process for the preparation of precious metal-coated particles. More particularly, this invention relates to a process for preparing particles each of which comprises a core material portion coated substantially completely with a precious metal layer.
• Particles comprising a core material portion made of inorganic material such as metal, metal oxide, ceramics and glass, and a precious metal layer coated on the core portion are employed or under study in various arts.
• particles in which precious metal such as gold or silver is coated on a core portion made of non-precious metal such as copper or nickel are under study for employing as electroconductive paste (namely, electroconductive coating material), a contactor and so forth used in electric circuits.
• electroconductive materials such as the electroconductive paste for use in electric circuits are generally made of pure precious metal such as gold, silver, platinum or palladium with a small amount of additives.
• the additives in the electroconductive paste are incorporated only for facilitating deposition of the paste on the circuits and selected from materials giving substantially no disturbance to the electroconductivity. Since the use of precious metal is very expensive and the price of the precious metal is rising quickly, trials for replacing the precious metal with a mixture of the precious metal and non-precious metals such as copper and nickel have been carried out in the arts of electroconductive materials such as the electroconductive paste. However, since such mixtures show electroconductive far lower than the pure precious metal, these trials have been discontinued. In place of these mixtures, particles of non-precious metal coated with precious metal have been studied for substituting the pure precious metal component as seen, for instance, in Japanese Patent Publication No. 46(1971)-40593 and No. 49(1974)-21874: the former discloses the use of particles of copper core coated with silver metal, in place of pure silver metal, and the latter discloses the use of particles of copper-bismuth core coated with silver metal in the art of the electroconductive paste.
• the chemical plating can be generally carried out in a simple vessel and with a simple procedure, and therefore, the chemical plating process is very advantageous for the industrial application.
• a process involving a reaction with a weak reducing agent such as sucrose namely, the silver mirror reaction.
• the chemical plating process involving the silver mirror reaction is concretely disclosed.
• the silver mirror reaction is considered to be practically unemployable for preparing the precious metal-coated particles of high quality for the use as the electroconductive material.
• the particles prepared by the use of the silver mirror reaction neither show satisfactory electroconductivity nor appropriate adhesive property to a soft solder.
• the poor electroconductivity and adhesive property to the soft solder is considered to originate from contamination of the surface layer of the particle with the core material.
• the reaction solution for the silver mirror reaction involves nitric acid, and such core metals as nickel and copper are in part dissolved in the aqueous nitric acid. Accordingly, when the precious metal layer is coated on the core metal particle, the dissolved core metal material is introduced into the coating layer to contaminate the precious metal layer. The contamination of such core materials into the precious metal coating layer causes the deteriorations of electroconductivity and adhesive property to the soft solder.
• the present invention provides a process for the preparation of precious metal-coated particles in which the precious metal coating layer has substantially no contamination with the core material employed.
• the particles prepared according to the process of the present invention substantially consists of the core material portion and the precious metal coating layer with substantially no contamination with the core material. For this reason, the so prepared particles give satisfactory electroconductivity and adhesion to the soft solder when employed as the electroconductive material for electric circuits.
• the process of the invention includes a process which comprises adding a reducing agent to an aqueous suspension containing:
• precious metal salt suspension process The above-described process is referred to hereinafter as "precious metal salt suspension process".
• the characteristic feature of the precious metal salt suspension process lies in that the precious metal is supplied with both forms of dissolved ions and suspended particles.
• Another characteristic feature lies in that the reduction reaction for forming the precious metal coating layer is carried out through gelling state.
• Examples of the precious metals employed in the process of the invention include silver, gold, platinum and palladium.
• There is no specific limitation on the salt form of the precious metal so far as the salt is soluble in the aqueous acidic medium employed for preparing the suspension to an extent, at least, enabling to form the suspended salt phase and the dissolved ionic phase in the medium.
• Examples of the salt forms include nitrate, hydrochloride and cyanide.
• the sizes of the precious metal salt particles In general, the mean particle size is almost similar to or less than the mean size of the core material particles.
• the core materials include non-precious metals such as transition metals, e.g., copper, nickel, cobalt and iron, and these alloys, oxides of metallic or non-metallic elements such as aluminum oxide, zirconium oxide, titanium dioxide, silica, and water insoluble metal salts such as barium titanate. Particularly preferred core materials are copper and nickel.
• the mean diameter of the core material particles is generally less than 30 ⁇ and preferably less than 10 p.
• the aqueous acidic medium to be employed in the above-described process has a certain degree of dissolving capacity for the precious metal salt to be employed and should have little dissolving capacity for the core material to be employed in the reaction. Accordingly, an aqueous inorganic acid consisting of a strong inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid and water is generally employed. A water-miscible organic solvent such as methyl alcohol, ethyl alcohol, acetone, tetrahydrofuran, or ethyl ether can be included in the inorganic acid solution.
• the inorganic acid is selected depending upon nature of the core material. For instance, since nitric acid dissolves copper and nickel, nitric acid is not appropriately employed when the core material is selected from copper and nickel. Concentrated hydrochloric acid is generally employed when copper or nickel is used as the core material.
• the reducing agent there is no specific limitation on the reducing agent to be employed in the process, so far as it can reduce both of the precious metal salt and the precious metal ion included in the reaction system.
• a reducing agent containing metallic element may possibly be carried into the precious metal layer to deteriorate the coating layer quality
• hydrogen peroxide and organic reducing agents such as hydrazine are preferred.
• Particularly preferred is hydrazine.
• the reducing agent is added to the suspension in an amount enough to reduce the precious metal salts and ions to convert to the metallic form.
• the ratio of the amount of the core material against the total amount of the precious metal including both of those present in the suspended salt form and those present in the ionic form preferably ranges from 1/9 to 7/3, more preferably 1/9-4/6.
• the ratio of the amount of the core material against the amount of the precious metal contained in the precious metal-coated particle is substantially similar to the ratio of those in the reaction system, and generally ranges from 1/9 to 7/3.
• Examples of the preferred combinations of the core material, the precious metal (precious metal salt), the inorganic acid to be included in the aqueous acidic medium of the suspension, and the reducing agent include:
• a copper powder is added to conc. hydrochloric acid to prepare a suspension [(I) suspension].
• Most of commercially available copper powders are coated with the oxide film, and this oxide film works negatively in providing a satisfactory adhesion between the copper core and the silver coating layer.
• the commercially supplied copper powder is preferably processed to remove the oxide film in advance of carrying out the coating procedures of the invention.
• the removal of the oxide film can be carried out by, for instance, immersing the copper powder into dilute hydrochloric acid or an aqueous solution of a reducing agent such as hydrazine or hydrogen peroxide.
• a silver salt such as silver chloride or silver nitrate in the microgranular form is suspended in conc. hydrochloric acid.
• the suspension is then stirred for a while to dissolve a portion of the silver salt in the hydrochloric acid.
• the resulting suspension is referred to as (II) suspension.
• the (II) suspension is added, at once or portionwise, to the (I) suspension under stirring.
• To the so obtained suspension mixture is further added under stirring hydrazine in an amount enough to reduce all of the silver salt contained in the suspension mixture.
• the hydrazine is preferably added by two portions.
• Vigorous stirring is applied to the gelling suspension, and within a while the gelling state is broken to convert the mixture again to the simple suspension.
• the coating of the copper powder with metallic silver layer is completed at the time when the gelling state is broken.
• the so obtained silver coating layer consists of pure silver metal with substantially no contamination with copper.
• This invention further provides another process for the preparation of precious metal-coated particles which comprises:
• precious metal solution process The above-described process is referred to hereinafter as "precious metal solution process".
• the characteristic feature of the precious metal solution process lies in that the coating reaction is necessarily carried out in a gelling suspension.
• Examples of the core material, the precious metal (precious metal salt), the aqueous acidic medium, and the reducing agent are the same as those described for the precious metal suspension process.
• the ratio between the core material and the precious metal is also the same as those described for the precious metal suspension process (referred to hereinafter as Suspension Process).
• the (I) suspension of copper powder is prepared in the same manner as in Suspension Process.
• a gold salt such as HAuCI 4 is introduced in hydrochloric acid to make its solution [(II) solution].
• the (I) suspension and the (II) solution are mixed, and a portion of a reducing agent such as hydrazine is added under stirring to the resulting mixture to turn it to a gelling suspension.
• Another portion of the reducing agent is then added to the gelling suspension under vigorous stirring to return the gelling suspension to a simple suspension.
• the so obtained gold coating layer consists of pure gold metal with substantially no contamination with copper.
• This invention further provides another process for the preparation of precious metal-coated particles which comprises mixing:
• precious metal chelation process or simply “chelation process”.
• the characteristic feature of the precious metal chelation process lies in that the portion of the precious metal to form the coating layer is subjected to the reduction to form the coating layer, in the chelated form and also that the reduction is accomplished in a gelling suspension.
• precious metals are the same are those described for the precious metal suspension process.
• the aqueous gelling solution containing precious metal ion and chelated precious metal compound referred to as (A) in the above can be prepared, for instance, as follows.
• a water-soluble precious metal salt such as silver nitrate is dissolved in water to prepare an aqueous precious metal ion solution of a relatively high concentration such as 5-50% by weight.
• a chelating agent such as EDTA (ethylenediaminetetraacetic acid) in the sodium salt form is dissolved in water to prepare a solution containing the chelating agent at a concentration of at least 2% by weight.
• the so prepared aqueous precious metal ion solution and chelating agent solution are then mixed, resulting in the formation of an aqueous gelling mixture comprising, in the aqueous phase, the precious metal ion and chelated precious metal compound and, in a suspended particle phase, chelated metal compound.
• the chelating agent preferably is incorporated in an amount of less than the stoichiometric amount for the counterpart metal ion to be incorporated in the mixture. More preferably, the chelating agent is an an amount of less than a half of the stoichiometric amount for the incorporated metal ion which serves as the counterpart in the formation of a chelated compound. Addition of a greater amount of the chelating agent may in advantageously cause contamination of the precious metal coating layer upon the reaction to reduce the quality of the coating layer.
• chelating agents to be employed in the chelating process include poly- aminocarboxylic acids such as EDTA, oxycarboxylic acids such as citric acid, and condensed phosphates. Particularly preferred is EDTA.
• hydrogen peroxide serves as a reducing agent in an alkaline solution to reduce the ionic and chelated precious metal to convert to the metallic form.
• hydrogen peroxide is preferably employed in an excessive amount.
• the aqueous suspension of core material particles referred to as (C) in the above preferably comprises the core material particles in a ratio ranging from 1/1000 to 1/10 (ratio by weight) per the amount of water.
• the core materials can be selected from those described for the precious metal suspension process.
• the chelation process can employ glass and ceramics.
• the chelation process is advantageously applied to core materials selected from nickel, and metal oxides such as zirconium oxide and titanium dioxide.
• the size and the ratio of the core material and the precious metal reference is made to the description given hereinbefore for the precious metal suspension process.
• the alkali agent assists hydrogen peroxide to work as a reducing agent.
• alkali agents to be employed in the chelation process include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
• the alkali agent is generally employed as an aqueous solution.
• the four (A), (B), (C) and (D) agents can be mixed in any sequence or simultaneously. Nevertheless, the sequences described below are advantageously adopted for the preparation of the precious metal coating layer of high quality.
• Hydrogen peroxide is added to the (A) gelling mixture; then the (C) suspension and finally the alkali agent are added successively thereto.
• the gelling mixture turns into a simple suspension containing precious metal-coated particles upon the addition of the alkali agent.
• This sequence is advantageously applied when material having some solubility in an aqueous alkaline solution such as titanium dioxide (Ti0 2 ) is employed as the core material.
• Hydrogen peroxide is added to the (A) gelling mixture; separately, a portion (e.g., a half) of the alkali agent is added to the (C) suspension; the latter (C+alkali agent) is added to the former (A+hydrogen peroxide); this procedure gives precipitation of a portion of the precious metal of metallic form on the core particle; and finally the remaining portion of the alkali agent is added thereto to break the gelling state to form a simple suspension containing precious metal-coated particles.
• the whole portion of the alkali agent can be added to the (C) suspension in the initial stage instead of the divisional addition. In this case, the addition of the mixture of (C) suspension and the alkali agent to the mixture of (A) gelling mixture and hydrogen peroxide instantly breaks the gelling state of the latter mixture to form a simple suspension containing precious metal-coated particles.
• Sequence II including the alternative sequence is advantageously applied when material having substantially no solubility in an aqueous alkaline solution such as nickel or zirconium oxide is employed as the core material.
• the process of the invention employs a reaction system in which the core material is hardly dissolved in the reaction medium, and therefore the precious metal coating layer of the precious metal-coated particles obtained according to the invention has substantially no contamination with the core material.
• the precious metal-coated particles provided by the invention is particularly advantageous when these are employed as electroconductive materials for the use in electric circuit, such as electric contactor and electroconductive paste because these show substantially same electroconductivity and adhesion to soft solder as pure metal materials show.
• Example 2 The procedure described in Example 1 was repeated, using 3 g. of the copper powder, 250 ml. of conc. hydrochloric acid and 200 ml. of water, to prepare a copper-containing suspension ... [(Ib) suspension].
• the (lib) suspension was added to the (lb) suspension by two times addition procedure in the same manner as in Example 1 to prepare a suspension.
• To the so prepared suspension was added 80 ml. of hydrazine, forming a gelling mixture. Further, 160 ml. of hydrazine was added to the gelling mixture, and the resulting mixture was vigorously stirred to break the gelling state into a simple suspension in which particles coated with metallic gold were suspended. The gold-coated particles were collected through filtration, and showed the gold:copper ratio by weight of approximately 2.1:1.
• a gelling solution was produced by mixing an aqueous solution of 10 g. of silver nitrate in 50 ml. of water and an aqueous solution of 15 g. of disodium ethylenediamine-tetraacetate (EDTA) in 200 mi. of water. 50 ml. of water was added to the gelling solution to reduce the viscosity of the solution. To the gelling solution was added 100 ml. of aqueous hydrogen peroxide (30% aqueous solution). To this gelling solution was further added a suspension of 1 g. of titanium dioxide powder (mean diameter: 2 ⁇ ) in 150 ml. of water, and the mixture was well stirred. To this gelling suspension was added under vigorous stirring 100 ml.
• EDTA disodium ethylenediamine-tetraacetate
• aqueous sodium hydroxide NaOH 5 g./25 ml. water
• 150 ml. of aqueous hydrogen peroxide (30%) was added to the suspension to complete the reaction.
• a gelling solution was produced by mixing an aqueous solution of 10 g. of silver nitrate in 50 ml. of water and an aqueous solution of 15 g. of disodium salt of EDTA in 300 ml. of water. 150 ml. of water was added to the gelling solution to reduce the viscosity of the solution. To the gelling solution was added 150 ml. of aqueous hydrogen peroxide (3096). To this gelling solution was further added a suspension of 1.5 g. of powdery nickel metal (mean diameter: 3 ⁇ ) in 50 ml. of aqueous sodium hydroxide (NaOH 5 g./25 ml. water, same hereinbelow), and the mixture was well stirred.
• Zr0 2 was pre-treated in the following manner to give the silver coating layer of an improved quality.
• a gelling mixture was prepared by mixing an aqueous solution of 10 g. of silver nitrate in 50 ml. of water and an aqueous solution of 15 g. of disodium salt of EDTA in 200 ml. of water under stirring, and further adding 50 ml. of water to the mixture.
• To the so prepared gelling mixture was added 100 ml. of aqueous hydrogen peroxide (30%), and subsequently the Zr0 2- containing suspension was added thereto under stirring.
• the gelling state was quickly broken to precipitate gray-colored particles coated with silver.
• the precipitated particles were recovered in the same manner as in Example 3. Yield 7.4 g. (theoretical yield 7.5 g . ) .
• a gelling solution was produced by mixing an aqueous solution of 11 g. of HAuCI 4 in 75 ml. of water and an aqueous solution of 25 g. of disodium salt of EDTA in 300 ml. of water. Water was added to this gelling solution to adjust the volume of the solution to 400 mi. To this gelling solution was added 150 ml. of aqueous hydrogen peroxide (30%).
• a commercially supplied powdery copper (mean diameter: 5 ⁇ ) was immersed in an aqueous hydrazine solution for 1 hour under stirring to remove the oxide film produced on the surface of the powder, and washed with water.
• 2 g. of the so prepared powdery copper was introduced into 140 ml. of aqueous sodium hydroxide (NaOH 5 g/25 ml. water) to obtain a homogeneous suspension.
• the above-prepared gelling solution was added to the suspension under stirring.
• the gelling state was quckly broken to precipitate copper particles coated with gold.
• the so precipitated particles were then recovered in the same manner as described in Example 3 to give brown- colored particles. Yield 8.2 g. (theoretical yield 8.37 g.).
• a mixture consisting of the above-listed materials was kneaded in a three-rollers type kneader to give a paste.
• the paste was printed on a ceramic base plate through the screen printing method.
• the so printed ceramic base plate was dried at 150°C for 30 min., and then placed in a firing furnace.
• the internal temperature of the furnace was elevated to 800°C over 1 hour, and this 800°C temperature was maintained for 10 min.
• the printed plate was then taken out of the furnace and cooled to room temperature.
• the so produced printed plate showed silver metallic surface at the printed portion.
• the Scanning Electron Microscope JSM-25S manufactured by Japan Electron Optics Laboratory Co., Ltd. was applied to the surface of the metallic surface layer of the metallic portion to observe its electron reflection image. The observation indicated that the metallic surface substantially consisted of pure silver metal with no trace of copper metal.
• the printed plate was immersed in a soft solder bath, and there was observed that whole surface of the metallic printed area was completely covered with the soft solder.
• the electroconductivity was almost equivalent to pure silver, 2x10- B Qcm.
• Example 7 The procedures of Example 7 were repeated except that the silver-coated copper particles were replaced with the gold-coated copper particles produced in Example 2 and also except that the amount of lead borosilicate glass frit was changed into 0.4 g. instead of the 0.2 g. to produce a metal printed plate.
• the printed plate was placed on a hot plate kept at 450°C, and a silicone tip was placed on the printed metal surface. The so placed silicone tip was well adhered to the metal surface.
• Example 7 The procedures of Example 7 were repeated except that the silver-coated copper particles were replaced with the silver-coated titanium dioxide particles produced in Example 3.
• Example 7 The procedures of Example 7 were repeated except that the silver-coated copper particles were replaced with the silver-coated nickel particles produced in Example 4.
• Example 7 The procedures of Example 7 were repeated except that the silver-coated copper particles were replaced with the silver-coated zirconium oxide particles produced in Example 5.
• Example 8 The procedures of Example 8 were repeated except that the gold-coated copper particles were replaced with the gold-coated copper particles produced in Example 6.
• the gold surface was formed on the particle with substantially no contamination with copper metal.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Powder Metallurgy (AREA)
• Chemically Coating (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

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• 1980
  • 1980-08-26 JP JP55116482A patent/JPS5741301A/ja active Granted
• 1981
  • 1981-08-19 DE DE8181303778T patent/DE3164569D1/de not_active Expired
  • 1981-08-19 EP EP81303778A patent/EP0046657B1/en not_active Expired

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