Metal paste for ceramic substrates

Abstract

Provided are a metal paste for ceramic substrates that has an optimal sintering temperature and sintering time, is weldable, solderable, and bondable without further processing, and exhibits ferromagnetic or paramagnetic properties and electrical conductivity in addition to oxidation resistance after sintering; a method for producing the metal paste; and a method for using the metal paste. A metal paste for ceramic substrates contains Ni-Cu-Fe metal alloy powder, glass powder, and further additives. A method for producing the metal paste includes the steps of preparing a first mixture by mixing Ni-Cu-Fe metal alloy powder, glass powder, and SiO2, and optionally Fe powder, optionally Ni powder, and optionally titanium(IV) oxide, adding organic additives, particularly solvents / diluents, binders, and dispersants, to the first mixture to adjust the viscosity, and blending the mixture until it becomes a (smooth) semi-solid.

Description

[Technical Field]

[0001] The present invention relates to a metal paste, a method for making a metal paste, and a method for using a metal paste. [Background technology]

[0002] Substrates made of ceramics such as alumina (Al2O3) and aluminum nitride (AlN) are often used as circuit boards for various electronic components. One method for forming circuits (conductor or metal layers) on ceramic substrates is to form electrical circuits using a conductor or metal paste through a process of screen printing, drying, and firing.

[0003] The conductor or metal paste is generally a dispersion of conductive powder and glass powder in an organic solvent.

[0004] Various metal pastes have been described in the past. For example, EP 2 164 822 B1 (Patent Document 1) discloses a conductive paste for ceramic substrates, comprising a) a conductive metal powder containing silver and palladium, b) a glass powder, and c) an organic solvent, wherein the conductive metal powder has an average particle size of 1.2 μm or less, the glass powder is a Bi2O3-SiO2-B2O3-based glass powder, and the content of the glass powder is within the range of 1 to 6 wt% based on the weight of the paste. The paste described in EP 2 164 822 B1 (Patent Document 1) can be sintered at temperatures of 650°C or less when applied to a ceramic substrate, and at the same time, it exhibits excellent adhesive strength on the ceramic substrate. However, the use of expensive materials, silver and palladium, makes this paste unsuitable for mass production.

[0005] WO 2014 / 195097 A1 (Patent Document 2) describes a metal coating on a ceramic substrate. The metal coating is obtained by applying a metal paste to the ceramic substrate and then sintering it. The paste may contain Ni powder, Fe powder, Cu powder, MnO-SiO2-Al2O3 glass powder, and an organic solvent. At least a portion of the Fe powder may be replaced with Ti powder and / or Al powder. Another glass powder described is ZnO-SiO2-B2O3-Al2O3-TiO2-ZrO2. The metal paste is sintered at a temperature of 800 to 900°C, preferably 830 to 870°C. However, it was found that the sintering temperature and sintering time when using such a paste are not optimal. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 2164822 [Patent Document 2] International Publication No. 2014 / 195097 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, one of the objects of the present invention is to provide a metal paste for ceramic substrates that has an optimal sintering temperature and sintering time, is weldable, solderable and bondable without further processing, and exhibits ferromagnetic or paramagnetic properties and electrical conductivity in addition to oxidation resistance after sintering. [Means for solving the problem]

[0008] The above object has been achieved by the metal paste having the features of claim 1.

[0009] That is, it is a metal paste for a ceramic substrate, Ni-Cu-Fe metal alloy powder; Glass powder, Further additives, A metal paste is provided, comprising:

[0010] The metal paste of the present invention offers a combination of properties. Iron-nickel alloys are used in the chemical industry due to their catalytic properties and mechanical, thermal, and magnetic properties. Copper-nickel alloys are often used in shipbuilding due to their high corrosion resistance and resistance to seawater erosion. In addition, these copper-nickel alloys have inherent antifouling properties. Ni-Cu-Fe alloys, such as those in this example, combine the advantages of both.

[0011] In one embodiment of the paste, 60 to 80 wt %, preferably 65 to 76 wt %, more preferably 68 to 73 wt % Ni-Cu-Fe powder is used (based on the total weight of the paste).

[0012] In one embodiment, the paste may further contain Fe powder and / or Ni powder and / or titanium (IV) oxide.

[0013] That is, in another embodiment, the paste contains 0.0 to 5 wt %, preferably 1 to 4 wt %, more preferably 1.2 to 3 wt % of Fe powder (based on the total weight of the paste).

[0014] In yet another embodiment, 0.0 to 5 wt. %, preferably 1 to 4 wt. %, more preferably 1.2 to 3 wt. % Ni powder is added (based on the total weight of the paste).

[0015] In yet another embodiment, the paste contains 0.0 to 10 wt. %, preferably 1 to 8 wt. %, and more preferably 1.2 to 5 wt. % TiO2 (based on the total weight of the paste).

[0016] In a further embodiment, the paste comprises 3 to 15 wt. %, preferably 5 to 10 wt. %, more preferably 6 to 8 wt. % glass powder (based on the total weight of the paste).

[0017] As further additives, further additives may be added in an amount of 15 to 25% by weight.

[0018] In one specific embodiment, the composition of the metal paste is: 60 to 80 wt. %, preferably 65 to 76 wt. %, more preferably 68 to 73 wt. % Ni-Cu-Fe powder (based on the total weight of the paste); 0.0 to 5 wt. %, preferably 1 to 4 wt. %, more preferably 1.2 to 3 wt. % Fe powder (based on the total weight of the paste); 0.0 to 5 wt. %, preferably 1 to 4 wt. %, more preferably 1.2 to 3 wt. % Ni powder (based on the total weight of the paste); 0.0 to 10 wt. %, preferably 1 to 8 wt. %, more preferably 1.2 to 5 wt. % TiO2 (based on the total weight of the paste); 3 to 15 wt. %, preferably 5 to 10 wt. %, more preferably 6 to 8 wt. % of glass powder (based on the total weight of the paste); 15 to 25 wt. % of further additives; The total of all ingredients always equals 100% by weight.

[0019] In an even more preferred embodiment, the composition of the metal paste is: 60-80 wt. % Ni-Cu-Fe powder (based on the total weight of the paste); 0.0 to 5 wt. % Fe powder (based on the total weight of the paste); 0.0 to 5 wt. % Ni powder (based on the total weight of the paste); 0.0 to 10 wt. % TiO2 (based on the total weight of the paste); 3 to 15 weight percent glass powder (based on the total weight of the paste); 15 to 25 wt. % of further additives; The total of all ingredients always equals 100% by weight.

[0020] In yet another preferred embodiment, the composition of the metal paste is: 65 to 76 weight percent Ni-Cu-Fe powder (based on the total weight of the paste); 1 to 4 wt. % Fe powder (based on the total weight of the paste); 1 to 4 wt. % Ni powder (based on the total weight of the paste); 1 to 8 wt. % TiO2 (based on the total weight of the paste); 5 to 10 weight percent glass powder (based on the total weight of the paste); 15 to 25 wt. % of further additives; The total of all ingredients always equals 100% by weight.

[0021] In yet another preferred embodiment, the composition of the metal paste is: 68-73 wt. % Ni-Cu-Fe powder (based on the total weight of the paste); 1.2 to 3 wt. % Fe powder (based on the total weight of the paste); 1.2 to 3 wt. % Ni powder (based on the total weight of the paste); 1.2 to 5 wt. % TiO2 (based on the total weight of the paste); 6 to 8 weight percent glass powder (based on the total weight of the paste); 15 to 25 wt. % of further additives; The total of all ingredients always equals 100% by weight.

[0022] As will be described in more detail below, the further additives (organic and inorganic) may include SiO2 and / or binders and / or dispersants (such as, for example, polymeric esters) and / or solvents and / or diluents.

[0023] The metal paste of the present invention can be sintered at a temperature of 650°C to 1600°C, preferably 800°C to 1500°C, and most preferably 900°C to 1400°C for 30 minutes to 12 hours, preferably less than 10 hours, and most preferably less than 8 hours.

[0024] The sintering is carried out in an inert or reducing atmosphere, preferably a reducing atmosphere. The reducing atmosphere may contain hydrogen and a further inert gas, such as a mixture of hydrogen and nitrogen, preferably a mixture of up to 50 parts hydrogen and up to 50 parts nitrogen. A reducing atmosphere is preferred over an oxidizing atmosphere.

[0025] The above sintering parameters allow the metal paste to be characterized by good adhesion, good electrical conductivity, and good paramagnetic properties on ceramic articles, which may be ceramic parts such as three-dimensional articles such as substrates and carriers for printed circuit boards. DETAILED DESCRIPTION OF THE INVENTION

[0026] (Ni-Cu-Fe alloy powder) The Ni-Cu-Fe alloy powder provides magnetic properties and allows the metal paste to be joined, soldered and welded.

[0027] In one embodiment, the Ni-Cu-Fe alloy powder comprises 15-35 wt %, preferably 18-30 wt %, and most preferably 20-28 wt % Ni (based on the total weight of the Ni-Cu-Fe alloy powder).

[0028] In a further embodiment, the Ni-Cu-Fe alloy powder comprises 12-26 wt. %, preferably 15-25 wt. %, and most preferably 18-23 wt. % Cu (based on the total weight of the Ni-Cu-Fe alloy powder).

[0029] In yet another embodiment, the Ni-Cu-Fe alloy powder comprises 45-75 wt %, preferably 50-70 wt %, and most preferably 55-65 wt % Fe (based on the total weight of the Ni-Cu-Fe alloy powder).

[0030] In a preferred embodiment, the Ni—Cu—Fe alloy powder contains, based on the total weight of the Ni—Cu—Fe alloy powder: 15-35 wt% Ni, preferably 18-30 wt% Ni, most preferably 20-28 wt% Ni, 12-26 wt% Cu, preferably 15-25 wt% Cu, most preferably 18-23 wt% Cu, and 45 to 75 wt. % Fe, preferably 50 to 70 wt. % Fe, most preferably 55 to 65 wt. % Fe, Preferably, the total of all components always equals 100% by weight.

[0031] In a preferred embodiment, the Ni-Cu-Fe alloy powder contains 15-35 wt% Ni, 12-26 wt% Cu, and 45-75 wt% Fe, based on the total weight of the Ni-Cu-Fe alloy powder, and preferably, the sum of all components always equals 100 wt%.

[0032] In a more preferred embodiment, the Ni-Cu-Fe alloy powder contains 18-30 wt% Ni, 15-25 wt% Cu, and 50-70 wt% Fe, based on the total weight of the Ni-Cu-Fe alloy powder, and preferably, the sum of all components always equals 100 wt%.

[0033] In a most preferred embodiment, the Ni-Cu-Fe alloy powder contains 20-28 wt% Ni, 18-23 wt% Cu, and 55-65 wt% Fe, based on the total weight of the Ni-Cu-Fe alloy powder, and preferably, the sum of all components always equals 100 wt%.

[0034] The alloy powder is obtained by mixing the metals, melting the mixture, and powdering the melt by injecting it into a jet (preferably a Laval jet), where the melt is surrounded by a flow of inert gas in the same direction as it flows through the jet.

[0035] The average particle size D90 of the Ni-Cu-Fe powder is about 3 to 60 μm, preferably about 5 to 50 μm, more preferably about 8 to 40 μm, and most preferably about 10 to 18 μm. The average particle size D50 of the Ni-Cu-Fe powder (measured in accordance with ISO 13320 using a laser particle size analyzer Cilas 1064) is about 1 to 40 μm, preferably about 2 to 30 μm, more preferably about 4 to 20 μm, and most preferably 4 to 12 μm.

[0036] When Ni-Cu-Fe alloy powder is used, the sintering time and temperature can be reduced compared to when metal powders such as Ni powder, Fe powder, and Cu powder are used individually.

[0037] (More metal powder) As mentioned above, in addition to the Ni-Cu-Fe alloy powder, further metal powders may be added.

[0038] The Fe powder enables the metal paste to be joined, soldered and welded.

[0039] The average particle size D50 of the Fe powder is 0.5 to 20 μm, preferably 2 to 15 μm, more preferably 4 to 12 μm, and most preferably 7 to 12 μm (measured according to ISO 13320 using a laser particle size analyzer Cilas 1064).

[0040] The Ni powder enables the metal paste to be joined, soldered and welded.

[0041] The Ni powder has a particle size D50 of 3 to 20 μm, preferably 5 to 18 μm, most preferably 8 to 15 μm (measured according to ISO 13320 with a laser particle sizer Cilas 1064), and preferably a particle size D99 of less than 90 μm, preferably less than 80 μm.

[0042] However, it should be understood that the paste may not require the addition of Fe powder and / or Ni powder.

[0043] TiO2 improves the adhesion of this metal paste on ceramic substrates, and using TiO2 instead of Ti is more cost-effective.

[0044] (glass powder) Glass is used to generate and improve adhesion of the metal paste to the ceramic substrate. Glass also contributes to lowering the surface energy of the paste when melted.

[0045] The glass powder used herein is based on Zn-Si-BO glass. Specifically, the glass powder contains ZnO, SiO2, and B2O3. Preferably, the amount of ZnO, SiO2, and B2O3 is 60 to 95% by weight, more preferably 75 to 90% by weight. The glass may further contain TiO2, ZrO2, Li2O, Na2O, CaO, Al2O3, or mixtures thereof.

[0046] In one embodiment, the glass powder contains 25-45 wt%, preferably 30-35 wt%, ZnO, 10-30 wt%, preferably 15-20 wt% B2O3, 20-40 wt%, preferably 25-35 wt% SiO2, and TiO2, ZrO 2、 It may contain further oxides such as Li2O, Na2O, CaO, Al2O3. The sum of all components always equals 100% by weight. In one embodiment, TiO2, ZrO 2、 The amount of each of the compounds Li2O, Na2O, CaO and Al2O3 added may be 0 to 7% by weight.

[0047] Glass melts at temperatures below 1500° C., preferably below 1200° C., and most preferably below 1000° C. At lower temperatures, the glass powder melts while retaining its properties.

[0048] The average particle size D50 (measured with a laser particle sizer Cilas 1064 according to ISO 13320) is 0.5 to 10 μm, preferably 0.8 to 8 μm, and more preferably 1.0 to 5 μm. Such a particle size of the glass powder provides optimal printability and sintering activity.

[0049] The glass powder in the paste may be a mixture of two or more types of glass powders.

[0050] It should be noted that the present metal paste does not have or contain any significant amount of aluminum (Al). A trace amount of Al, less than 1.3% by weight, may be present in the glass powder. Indeed, the addition of Al is undesirable because it impairs the properties of the paste, either because of its undesirable properties in the paste or because of its reaction with other compounds in the paste. Furthermore, Al deteriorates the magnetic properties of the paste.

[0051] Furthermore, CuO and CuO2 are not added to this paste because they cause problems during sintering and soldering, as the sintering time is too short to completely reduce the oxides to metal. Metals such as tungsten (W) / tungsten oxide (WO2), molybdenum (Mo), and tantalum (Ta) are also not added to this paste because they increase the melting point. This paste does not contain lead (Pb).

[0052] As mentioned above, the metal paste may also include additional additives.

[0053] (Solvent / Diluent) Solvents and / or diluents are added to adjust the viscosity of the metal paste for subsequent application, such as application onto a ceramic component, such as a ceramic substrate or carrier for a printed circuit board. The metal paste can be applied to a ceramic component, such as a substrate or carrier for a printed circuit board, by various printing techniques, by spraying the paste onto the ceramic component, such as a substrate or carrier for a printed circuit board, or by immersing the substrate in the paste. After application, the solvent and / or diluent are removed during drying and sintering.

[0054] The type of organic solvent / diluent is not particularly limited. Examples of organic solvents / diluents include, but are not limited to, α-terpineol, butyl carbitol, butyl carbitol acetate, Texanol, octanol, 2-ethylhexanol, and mineral spirits. Preferred solvents / diluents are α-terpineol, butyl carbitol, butyl carbitol acetate, Texanol, octanol, 2-ethylhexanol, and mineral spirits.

[0055] The amount of solvent / diluent in the paste is 0.5 to 15% by weight, preferably 1.0 to 11.0% by weight, and more preferably 1.5 to 8.0% by weight.

[0056] Amorphous and / or crystalline SiO2 acts as a thickener and is the source of thixotropy in the metal paste. The amount of SiO2 added may be 0.1 to 1 wt%, preferably 0.15 to 0.8 wt%, and more preferably 0.18 to 0.6 wt%.

[0057] In one embodiment, fumed silica can be used. Fumed silica is a synthetic colloidal material with specific properties and dimensions, and is used as a filler in plastics. It is composed entirely of amorphous silicon dioxide (SiO2) particles, which aggregate to form larger units. Fumed silica has a primary particle size of about 5 to 50 nm and a BET specific surface area of ​​50 to 600 m. 2 The particle size of the aggregates is 0.1 to 100 μm.

[0058] Binders are used to impart semi-solid consistency and basic viscosity to the paste. Binders can be short-chain (C10), medium-chain (C50), or long-chain (C100), cyclic or acyclic, linear or branched, low-volatility organic liquids such as ethers and / or esters, carboxylic acids, fatty acids, polyethers, or polyesters, preferably containing oxygen as a heteroatom in the chain. Alternatively, the binder can be a polymer powder dissolved in a suitable solvent or a mixture of resins dissolved in a solvent. Examples of suitable polymers include, but are not limited to, linear polymethacrylates, branched polymethacrylates, and nitrocellulose. Examples of such resins include ethyl cellulose resin, hydroxypropyl cellulose resin, acrylic resin, polyester resin, polyvinyl butyral resin, polyvinyl alcohol resin, rosin-modified resin, and epoxy resin.

[0059] The amount of binder added may be 10 to 20% by weight, preferably 12 to 18% by weight, and more preferably 13 to 16% by weight.

[0060] Dispersants (such as polymer esters) are used to improve mixing of all the components of the paste, and may be added in an amount of 0.1 to 0.3 wt %, preferably 0.12 to 0.2 wt %, and more preferably 0.13 to 0.18 wt %.

[0061] This metal paste is preparing a first mixture by mixing a Ni-Cu-Fe metal alloy powder, a glass powder, and SiO2, and optionally Fe powder, optionally Ni powder, and optionally titanium (IV) oxide; adjusting the viscosity of the first mixture by adding organic additives, in particular solvents, binders and dispersants; blending the mixture until it is semi-solid (smooth); The method is obtained by the method comprising:

[0062] Each component of the paste is provided in the amounts indicated above.

[0063] The components of the paste are blended or mixed in a suitable blending or mixing device, the rotation speed of which is preferably adjusted so as to avoid heating the paste during the mixing process.

[0064] As mentioned above, the metal paste is used as a conductive layer on a ceramic article such as a ceramic substrate for a circuit board, or on a cooling device or a three-dimensional object.

[0065] Suitable ceramic substrates may be oxide ceramics such as Al2O3, Al2O3-ZrO2, Al2O3-SiO2, Al2O3 / ZrO2 / Y2O3, ZrO2, or non-oxide ceramics such as AlN or Si3N4, or may be dielectric or magnetic.

[0066] The metal paste is applied to a ceramic substrate and then sintered at a temperature above 650°C, preferably above 800°C, and most preferably above 900°C.

[0067] As mentioned above, the metal paste of the present invention is used to form electrical circuits on ceramic substrates. For this purpose, solder is applied to the metal paste after sintering on the ceramic substrate. It has been confirmed that the metal paste has high wettability, i.e., solder can be applied to the paste very well and is retained on the paste, and also has high peeling resistance, i.e., the paste is not peeled off from the ceramic by the solder (i.e., preferably 95% of the paste is retained on the ceramic compound).

[0068] The specific square resistance of the conductor line applied to the ceramic is 100 to 220 mΩ / □, preferably 120 to 200 mΩ / □. The sheet resistance can be adjusted by adjusting the sintering conditions. [Example]

[0069] The present invention will now be described in more detail with reference to examples.

[0070] The following examples are included to demonstrate certain aspects and embodiments of the claimed invention. However, those of ordinary skill in the art will appreciate that the following descriptions are illustrative only and should not be construed as limiting the invention.

[0071] An embodiment of a metal paste according to the present invention may have the following composition:

[0072] [Table 1]

[0073] [Table 2]

[0074] The total of all components always adds up to 100% by weight.

[0075] The particle size of each compound used in the paste is measured using a laser particle size measuring instrument Cilas 1064 in accordance with ISO 13320.

[0076] (Preparation of NCF paste) The Ni-Cu-Fe alloy powder was prepared by mixing the metals, melting the mixture, and granulating it into powder. preparing a first mixture by mixing a Ni-Cu-Fe metal alloy powder, a glass powder, and SiO2, and optionally Fe powder, optionally Ni powder, and optionally titanium (IV) oxide; adjusting the viscosity of the first mixture by adding organic additives, in particular solvents, binders and dispersants; blending the mixture until it is semi-solid (smooth); The method is obtained by the method comprising:

[0077] The amounts of each compound in the paste are as shown in the table above.

[0078] (metal paste wettability) The ceramic is baked with the paste and then immersed in a solder bath at 250°C or higher. The solder bath contains a lead-free solder made of tin, silver, and copper. The ceramic is left in the bath for approximately 10 seconds and then removed. The amount of solder that "sticks" to the paste upon initial removal is measured; the more the amount, the better the wetting. After removal from the solder bath, the fired paste is over 80% wet.

[0079] (Solder corrosion resistance) To measure the solubility of the metal coating in solder, ceramics are dipped several times to determine whether the paste still adheres to the ceramic after multiple passes. It is undesirable for the baked paste to form an alloy with the solder and / or for the paste to peel off. In this experiment, the paste of the present invention remains on the ceramic with no or almost no reaction with the solder.

[0080] The adhesive strength of this metal paste is 5N / mm 2 The adhesive strength gives information about how strongly the metal coating is bonded to the ceramic. A nut is attached to the metal coating (with glue if the metal coating is not solderable, or with solder if the metal coating is solderable) and then tension is applied until the nut comes off.

[0081] The electrical resistivity is 100 to 220 mΩ / □, preferably 120 to 200 mΩ / □. The electrical resistivity is measured using a conductor line of a specified length and width that is applied to a ceramic carrier and sintered (see the conditions described above). After sintering, the layer thickness is measured, and the electrical resistance of the conductor line is measured at two points using a multimeter, and then standardized to a thickness of 10 μm to obtain the electrical resistivity.

[0082] The durability or lifespan of the metal paste exceeds 500 cycles (measured in an impact test: using two chambers at each temperature, 15 minutes at 40°C, followed by a 7-second transfer time at 125°C for 15 minutes; the coated ceramic compound is transferred between the two chambers).

[0083] The increase in electrical resistance after 1000 cycles is less than 2 Ω.

Claims

1. A metal paste for a ceramic substrate, Ni—Cu—Fe metal alloy powder; Glass powder, Further additives, A metal paste comprising:

2. The metal paste according to claim 1, further comprising: Fe powder and / or Ni powder and / or titanium(IV) oxide, A metal paste comprising:

3. The metal paste according to claim 1 or 2, 60 to 80 wt. %, preferably 65 to 76 wt. %, more preferably 68 to 73 wt. % Ni—Cu—Fe powder (based on the total weight of the paste); 0.0 to 5 wt. %, preferably 1 to 4 wt. %, more preferably 1.2 to 3 wt. % Fe powder (based on the total weight of the paste); 0.0-5 wt. %, preferably 1-4 wt. %, more preferably 1.2-3 wt. % Ni powder (based on the total weight of the paste); 0.0 to 10 wt. %, preferably 1 to 8 wt. %, more preferably 1.2 to 5 wt. % TiO (based on the total weight of the paste) ２ and, 3-15 wt. %, preferably 5-10 wt. %, more preferably 6-8 wt. % of glass powder (based on the total weight of the paste); 15 to 25 wt. % of further additives; A metal paste characterized by containing the above components so that the total of all components is always 100% by weight.

4. 4. The metal paste according to claim 1, wherein the Ni-Cu-Fe alloy powder contains, based on the total weight of the Ni-Cu-Fe alloy powder, 15 to 35 wt. %, preferably 18 to 30 wt. %, and most preferably 20 to 28 wt. % Ni, 12 to 26 wt. %, preferably 15 to 25 wt. %, and most preferably 18 to 23 wt. % Cu, and 45 to 75 wt. %, preferably 50 to 70 wt. %, and most preferably 55 to 65 wt. % Fe.

5. 5. The metal paste according to claim 1, wherein the average particle size D50 of the Ni-Cu-Fe powder is about 1 to 40 μm, preferably about 2 to 30 μm, more preferably about 4 to 20 μm, and even more preferably about 4 to 12 μm.

6. 6. The metal paste according to claim 1, wherein the average particle size D50 of the Fe powder is 0.5 to 20 μm, preferably 2 to 15 μm, more preferably 4 to 12 μm, and even more preferably 7 to 12 μm.

7. 7. The metal paste according to claim 1, wherein the glass powder contains ZnO, SiO ２ and B ２ O ３ A metal paste comprising:

8. 8. The metal paste according to claim 1, wherein the glass powder has an average particle size D50 of 0.5 to 10 μm, preferably 0.8 to 8 μm, and more preferably 1.0 to 5 μm.

9. 9. A metal paste according to any one of claims 1 to 8, characterized in that a solvent / diluent, in particular an organic solvent / diluent, is added to the metal paste.

10. 10. The metal paste of claim 9, wherein the solvent / diluent is one of α-terpineol, butyl carbitol, butyl carbitol acetate, texanol, octanol, 2-ethylhexanol, and mineral spirits.

11. 11. The metal paste according to claim 9 or 10, characterized in that the amount of solvent / diluent in the paste is 0.5 to 15% by weight, preferably 1.0 to 11% by weight, more preferably 1.5 to 8% by weight.

12. The method for producing a metal paste according to any one of claims 1 to 11, Ni-Cu-Fe metal alloy powder, glass powder, and SiO ２ and optionally mixing Fe powder, Ni powder, and titanium (IV) oxide to prepare a first mixture; adjusting the viscosity of said first mixture by adding organic additives, in particular solvents / diluents, binders and dispersants; blending the mixture until it becomes semi-solid (smooth); A manufacturing method comprising:

13. A method for using the metal paste according to any one of claims 1 to 11 as a conductor layer on a ceramic substrate, a cooling device, or a three-dimensional object.

14. A ceramic substrate comprising a conductor layer obtained from the metal paste according to claim 1 .

15. The method for manufacturing a ceramic substrate according to claim 14, A step of applying the metal paste according to any one of claims 1 to 11 to a ceramic substrate; sintering the metal paste applied to the ceramic substrate in a reducing atmosphere at a temperature above 650°C, preferably above 800°C, and most preferably above 900°C; A manufacturing method comprising:

Images