Conductive paste, electrode, and chip resistor

Abstract

Provided is a conductive paste having an electrode that can form high sulfurization resistance and low resistance at a relatively low cost. The conductive paste contains (A) alloy particles containing Ag and Sn, (B) a glass frit, and (C) a thermoplastic resin, and the proportion by weight of Sn in the (A) alloy particles is less than 10% by weight.

Description

Technical Field

[0001] This invention relates, for example, to a conductive paste used in the formation of electrodes for electronic components. Furthermore, this invention relates to electrodes formed using this conductive paste, and to chip resistors having such electrodes. Background Technology

[0002] A conductive paste containing silver powder is used in the formation of the electrodes of a surface-mount resistor, which is an electronic component. Figure 1 An example of the cross-sectional structure of a chip resistor 100 is shown. The chip resistor 100 has a rectangular alumina substrate 102. A resistive element 104 and a take-off electrode 106 for extracting electricity from the resistive element 104 are formed on the upper surface of the alumina substrate 102. Furthermore, a lower surface electrode 108 for mounting the chip resistor 100 to the substrate is formed on the lower surface of the alumina substrate 102. A connection electrode 110 for connecting the take-off electrode 106 and the lower surface electrode 108 is formed on the end face of the alumina substrate 102. After conductive paste is applied to the upper and lower surfaces of the alumina substrate 102 by printing, a firing process is performed to form the take-off electrode 106 and the lower surface electrode 108, respectively. Generally, a nickel plating film 112 and a tin plating film 114 are formed on the take-off electrode 106, the lower surface electrode 108, and the connection electrode 110.

[0003] Since the take-out electrode 106 and the lower surface electrode 108 have different required characteristics, different conductive pastes are generally used to form them. For example, in the formation of the take-out electrode 106, a conductive paste with good matching with the resistive element 104 is used. Furthermore, when the resistance value of the resistive element 104 is low, it is required that the resistance value of the take-out electrode 106 is also low. Therefore, in the formation of the take-out electrode 106, a conductive paste capable of forming a low-resistance electrode is used.

[0004] In the past, conductive pastes used in the formation of electrodes have been known to contain silver powder and glass frit, as disclosed in Patent Documents 1 and 2.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: JP Japanese Patent Application Publication No. 7-105723

[0008] Patent Document 2: JP Patent No. 2016-538708 Summary of the Invention

[0009] In automobiles and thermal power plants, the burning of fossil fuels releases large amounts of sulfur oxides into the atmosphere. Furthermore, in wastewater treatment plants and landfills, sulfur is reduced by anaerobic bacteria to produce hydrogen sulfide. Therefore, sulfur-containing components such as sulfur oxides and hydrogen sulfide exist in the atmosphere.

[0010] If sulfur-containing components in the atmosphere reach the surface of silver, the sulfur will adhere to the silver and react with it to form silver sulfide. For example, the same reaction will occur in electrodes made primarily of silver, such as those in surface mount resistors. Therefore, sometimes the silver inside the electrode becomes silver sulfide. If silver sulfide forms inside the electrode, it can cause a break in the electrode. As a result, malfunctions sometimes occur in devices such as surface mount resistors with silver electrodes. This phenomenon is called a break due to sulfide.

[0011] To suppress wire breakage caused by sulfidation, electrodes with high sulfidation resistance are required for silver-based electrodes used in devices such as surface mount resistors.

[0012] To suppress wire breakage caused by sulfidation, palladium monomers or the addition of a given amount (e.g., 20% by weight) of palladium is proposed as conductive particles in the conductive paste used to form electrodes. However, due to the high price of palladium, there is a problem that the cost of the conductive paste increases due to the addition of palladium monomers or palladium.

[0013] Therefore, the object of the present invention is to provide a conductive paste having electrodes that can form high sulfidation resistance and low resistance at a relatively low cost.

[0014] To address the aforementioned issues, the present invention has the following structure.

[0015] (Structure 1)

[0016] Structure 1 of the present invention is a conductive paste containing: (A) alloy particles comprising Ag and Sn; (B) glass frit; and (C) a thermoplastic resin, wherein the Sn in the alloy particles comprises less than 10% by weight.

[0017] (Structure 2)

[0018] In the present invention, structure 2 is based on the conductive paste of structure 1, wherein the weight proportion of Ag in the alloy particles (A) is 50% or more.

[0019] (Structure 3)

[0020] In the present invention, structure 3 is based on the conductive paste of structure 1 or 2, wherein the content of glass frit (B) is 2 to 20 parts by weight relative to 100 parts by weight of alloy particles (A).

[0021] (Structure 4)

[0022] The structure 4 of the present invention, based on the conductive paste described in any one of structures 1 to 3, further includes: (D) silica filler.

[0023] (Structure 5)

[0024] In the present invention, structure 5 is based on the conductive paste described in structure 4. The glass material (B) contains SiO2 and TiO2. The weight ratio of SiO2 B contained in the glass material (B) to the weight D of SiO2 contained in the silica filler (D) is B:D = 1:0.25 to 1:9.8.

[0025] (Structure 6)

[0026] Structure 6 of the present invention is an electrode obtained by firing the conductive paste of any one of structures 1 to 5.

[0027] (Structure 7)

[0028] Structure 7 of the present invention is a chip resistor having the electrodes described in structure 6.

[0029] According to the present invention, a conductive paste is provided that can form electrodes with high sulfidation resistance, low resistance, and relatively low cost. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating an example of the cross-sectional structure of a chip resistor.

[0031] Figure 2 The image is a cross-sectional SEM image (magnification 1500x) of a test piece (sintered body of conductive paste) prepared under the same conditions as in Example 4, after being stored in a sulfur-containing gas atmosphere.

[0032] Figure 3 The image is a cross-sectional SEM image (magnification 1500x) of a test piece (sintered body of conductive paste) prepared under the same conditions as Comparative Example 3, after being stored in a sulfur-containing gas atmosphere. Detailed Implementation

[0033] The following describes specific embodiments of the present invention. Furthermore, these embodiments are illustrative of the present invention and do not limit the invention to their scope.

[0034] The conductive paste of this embodiment comprises (A) alloy particles, (B) glass frit, and (C) thermoplastic resin. The conductive paste of this embodiment is preferably used for forming electrodes in devices such as chip resistors having electrodes made of silver.

[0035] The following describes the components contained in the conductive paste of this embodiment.

[0036] (A) Alloy particles

[0037] The conductive paste of this embodiment contains (A) alloy particles. The (A) alloy particles contain silver (Ag) and tin (Sn). By including Sn in the (A) alloy particles, the sulfidation of Ag can be suppressed. Therefore, by using the conductive paste of this embodiment, an electrode with high sulfidation resistance can be formed.

[0038] Furthermore, the (A) alloy particles may contain metals other than Ag and Sn. However, in order to reliably obtain an electrode with low resistance and high sulfidation resistance, it is preferable that the (A) alloy particles contain only Ag and Sn. In addition, in this specification, "the (A) alloy particles contain only Ag and Sn" means that as (A) metal particles, metals other than Ag and Sn are not intentionally incorporated, so as not to exclude even metals other than Ag and Sn that are inevitably mixed in.

[0039] (A) The alloy particles may contain metals such as Zn, In, Al and Si, other than Ag and Sn, without impairing the effects of this embodiment.

[0040] In the conductive paste of this embodiment, the weight percentage of Sn in the alloy particles (A) is preferably less than 10% by weight. More specifically, the weight percentage of Sn in the alloy particles (A) is preferably 1% by weight or more but less than 10% by weight, more preferably 1.5% by weight or more but less than 9% by weight, further preferably 2% by weight or more but less than 8% by weight, and particularly preferably 4% by weight or more but less than 8% by weight. When the weight percentage of Sn is too high, the resistance as an electrode may become too high. Furthermore, when the weight percentage of Sn is low, the improvement in sulfidation resistance is not significant. In particular, when the weight percentage of Sn is less than 2% by weight, the sulfidation resistance tends to deteriorate.

[0041] In this embodiment, the conductive paste preferably contains 50% by weight or more Ag in the alloy particles (A), more preferably 70% by weight or more, and even more preferably over 90% by weight. Ag has a lower resistance compared to other metals. Therefore, by using a given range of Ag weight proportions, electrodes with relatively low resistance can be obtained.

[0042] (A) The shape of the alloy particles is not particularly limited, for example, spherical, granular, snowflake and / or scale-shaped alloy particles can be used.

[0043] (A) The average particle size of the alloy particles is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 7 μm, and most preferably 1 μm to 5 μm. The average particle size referred to here is the volume reference median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement method.

[0044] (A) There are no particular limitations on the manufacturing method of alloy particles. For example, they can be manufactured by reduction, crushing, electrolysis, atomization, heat treatment, or a combination thereof. Snowflake-like alloy particles can be manufactured, for example, by flattening spherical or granular alloy particles using a ball mill or the like.

[0045] (B) Glass Material

[0046] The conductive paste of this embodiment includes (B) glass frit.

[0047] (B) The glass frit preferably contains SiO2 and TiO2. By including the glass frit (B) in the conductive paste, the adhesion strength between the electrode and the substrate is improved when the conductive paste is sintered. The glass frit is not particularly limited, but a glass frit with a softening point of 300°C or higher is preferred, a glass frit with a softening point of 400–900°C is more preferred, and a glass frit with a softening point of 500–800°C is even more preferred. The softening point of the glass frit can be measured using a thermogravimetric analyzer (e.g., BRUKERAXS TG-DTA2000SA).

[0048] Examples of glass frits (B) include titanium borosilicate (TiO2) and barium borosilicate glass frits. Other examples include bismuth borosilicate, alkali metal borosilicate, rare earth metal borosilicate, zinc borosilicate, lead borosilicate, lead borate, lead silicate, bismuth borosilicate, and zinc borate glass frits. Two or more of these glass frits can be mixed. For environmental reasons, lead-free glass frits are preferred.

[0049] The glass frit preferably contains at least one selected from the group consisting of ZnO, BaO, Na2O, CaO, and Al2O3. More preferably, the glass frit contains ZnO, BaO, Na2O, and Al2O3.

[0050] The average particle size of the glass frit is preferably 0.1–20 μm, more preferably 0.2–10 μm, and most preferably 0.5–5 μm. Here, the average particle size refers to the volumetric median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement.

[0051] In the conductive paste of this embodiment, the content of (B) glass frit is preferably 1 to 20 parts by weight relative to 100 parts by weight of (A) alloy particles, more preferably 1.5 to 15 parts by weight, and even more preferably 2 to 10 parts by weight. When the glass frit content is less than this range, the adhesion of the electrode obtained by firing the conductive paste to the substrate decreases. When the glass frit content is more than this range, the resistance value of the electrode obtained by firing the conductive paste increases. Furthermore, when the glass frit content is relatively low, an electrode with low resistance can be obtained. In addition, when the glass frit content is relatively high, an electrode with excellent chemical resistance can be obtained. Chemical resistance is a characteristic sought when a plating film is formed on the surface of the electrode, due to the need for pre-plating treatment. The purpose of pre-plating treatment is to remove contaminants from the surface of the electrode, activate the electrode surface, and create a clean state suitable for plating. The contaminants to be removed are broadly classified as organic and inorganic. The pre-treatment step is not a step in which all contaminants are removed in a single step. For example, organic substances are removed in processes using alkaline cleaning agents. Inorganic substances are removed in processes using acidic cleaning agents. Therefore, high chemical resistance is required for the electrodes.

[0052] As the temperature rises, the glass frit softens, and the sintering of silver progresses. When the glass frit content is high, glass components may sometimes be extruded onto the surface of the sintered body. In this case, the surface of the sintered body may be covered by glass components. By forming a nickel plating film on the surface of the sintered body, not only can the diffusion of tin from the tin plating film to the electrode be suppressed, but the conductivity of the sintered body can also be improved even when the surface of the sintered body is covered by glass components. The alloy particles (A) in this embodiment, being alloy particles containing Ag and Sn, have lower sinterability compared to Ag particles. Therefore, the phenomenon of the sintered body surface being covered by glass components can be suppressed. Therefore, since the glass frit content can be increased, an electrode with superior chemical resistance can be obtained compared to Ag particles. Furthermore, regarding the silica filler (D), which has the same properties and functions as the glass frit, an electrode with superior chemical resistance can also be obtained by increasing its content.

[0053] (C) Thermoplastic resin

[0054] The conductive paste of this embodiment contains (C) a thermoplastic resin.

[0055] Thermoplastic resin binds silver powder together in conductive paste. As a thermoplastic resin, a thermoplastic resin that burns off during the firing of the conductive paste can be used.

[0056] As thermoplastic resins, examples include cellulose-based resins such as ethyl cellulose and nitrocellulose, acrylic resins, alkyd resins, saturated polyester resins, butyral resins, polyvinyl alcohol, and hydroxypropyl cellulose. These resins can be used alone or in mixtures of two or more types.

[0057] (C) The content of thermoplastic resin relative to 100 parts by weight of alloy particles (A) is preferably 0.5 to 40 parts by weight, more preferably 1 to 35 parts by weight. When the content of thermoplastic resin in the conductive paste is within the above range, the conductive paste improves the coating properties and leveling properties of the substrate, resulting in excellent printable shapes. On the other hand, if the content of thermoplastic resin exceeds the above range, the amount of thermoplastic resin contained in the conductive paste becomes excessive. As a result, it may no longer be possible to form electrodes with high precision.

[0058] (D) Silica filler

[0059] The conductive paste of this embodiment preferably further comprises (D) silica filler.

[0060] (D) Silica filler, for example, can be commercially available spherical silica (SiO2) particles, used as a semiconductor sealing material. The shape of the silica filler can also be other than spherical. There are no particular limitations on the manufacturing method of the silica filler; silica fillers manufactured by known methods such as thermal spraying can be used. The average particle size of the silica filler is preferably 20 nm to 5 μm, more preferably 1 μm to 3 μm. Here, the average particle size refers to the volumetric median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement.

[0061] In the conductive paste of this embodiment, (B) glass frit contains SiO2 and TiO2, and the weight ratio of SiO2 B contained in (B) glass frit to SiO2 D contained in (D) silica filler is preferably B:D = 1:0.25 to 1:9.8, and more preferably B:D = 1:0.25 to 1:3.5.

[0062] The conductive paste of this embodiment improves the chemical resistance of the electrode obtained by containing (D) silica filler. On the other hand, if there is too much silica filler, the resistance of the resulting electrode becomes high, making it difficult to obtain a low-resistance electrode. Furthermore, the (D) silica filler has the same function as the (B) glass frit. Therefore, by keeping the ratio of the weight B of SiO2 contained in the (B) glass frit to the weight D of SiO2 contained in the (D) silica filler within the range described above, suitable chemical resistance and a low-resistance electrode can be obtained.

[0063] (E) Solvent

[0064] The conductive paste of this embodiment may contain a solvent (E). Examples of solvents include alcohols such as methanol, ethanol, and isopropanol (IPA), organic acids such as vinyl acetate, aromatic hydrocarbons such as toluene and xylene, N-alkylpyrrolidones such as N-methyl-2-pyrrolidone (NMP), amides such as N,N-dimethylformamide (DMF), ketones such as methyl ethyl ketone (MEK), cyclic carbonates such as terpineol (TEL) and butyl carbitol (BC), and water. The amount of solvent is not particularly limited. The amount of solvent relative to 100 parts by weight of alloy particles (A) is preferably 1 to 100 parts by weight, more preferably 5 to 60 parts by weight.

[0065] The viscosity of the conductive paste in this embodiment is preferably 50–700 Pa·s (shear rate: 4.0 sec). -1 More preferably, it is 100–300 Pa·s (shear rate: 4.0 sec). -1 By adjusting the viscosity of the conductive paste within this range, the paste's coatability and handling properties on the substrate become excellent, allowing it to be applied to the substrate with a uniform thickness. Furthermore, the viscosity of the conductive paste can be measured using an HB-type viscometer SC4-14SPINDLE (manufactured by Brookfield).

[0066] The conductive paste of this embodiment may contain other additives, such as dispersants, rheology modifiers, pigments, etc.

[0067] The conductive paste of this embodiment can be manufactured by mixing the above-mentioned components using a pounder, a can mill, a three-roll mill, a rotary mixer, and / or a two-shaft mixer.

[0068] This embodiment is an electrode obtained by calcining the conductive paste of this embodiment as described above.

[0069] This embodiment uses the conductive paste described above as the material to form an electrode. The electrode of this embodiment is obtained by coating the conductive paste onto a substrate and then firing it. Therefore, the electrode of this embodiment contains (A') alloy particles comprising Ag and Sn and (B') glass components made of glass frit. The (A') alloy particles are in a sintered state. The Sn content in the (A') alloy particles of the electrode of this embodiment is less than 10% by weight. Furthermore, since the (C) thermoplastic resin and (E) solvent contained in the conductive paste are vaporized or burned during firing, the electrode substantially does not contain (C) thermoplastic resin and (E) solvent.

[0070] In addition to the (A') alloy particles and (B') glass components, the electrode of this embodiment may further contain (D') silica filler. Furthermore, regarding the electrode of this embodiment, the weight ratio of Ag in the (A') alloy particles, the content of the (B') glass components, and the composition of the (B') glass components correspond to the weight ratio and composition of the (A) alloy particles and (B) glass components contained in the conductive paste that forms the material.

[0071] The sheet resistance of the thin film that forms the electrode in this embodiment varies depending on the film thickness, and can be set to approximately 10 mΩ / □ (10 mΩ / square) or less. Therefore, it is preferable to use it in the formation of electrodes where low resistance is required.

[0072] Next, a method for forming electrodes on a substrate using the conductive paste of this embodiment will be described. First, the conductive paste is applied to the substrate. The application method is arbitrary; for example, known methods such as dispensing, jet dispensing, stencil printing, screen printing, dot transfer printing, or embossing can be used.

[0073] After applying a conductive paste to a substrate, the substrate is placed in a sintering furnace or similar environment. The conductive paste applied to the substrate is then sintered at 500–900°C, more preferably 600–900°C, and even more preferably 700–900°C. As a result, the solvent components in the conductive paste evaporate at temperatures below 300°C, and the resin components burn off at 400–600°C, forming a sintered conductive paste body. The resulting electrode exhibits high chemical resistance and excellent adhesion to the substrate.

[0074] This embodiment is a chip resistor having the electrodes described above.

[0075] The conductive paste of this embodiment can be used in the formation of circuits for electronic components and other devices, the formation of electrodes, and the bonding of electronic components and other devices to a substrate. Furthermore, the conductive paste of this embodiment is preferably used in the formation of electrodes for surface mount resistors.

[0076] exist Figure 1An example of the cross-sectional structure of the chip resistor 100 according to this embodiment is shown. The chip resistor 100 may have: a rectangular alumina substrate 102; and a resistive element 104 disposed on the surface of the alumina substrate 102 and a take-off electrode 106. The take-off electrode 106 is an electrode for extracting electricity from the resistive element 104. Furthermore, a lower surface electrode 108 for mounting the chip resistor 100 to the substrate may be disposed on the lower surface of the alumina substrate 102. Furthermore, a connection electrode 110 for connecting the take-off electrode 106 and the lower surface electrode 108 may be disposed on the end face of the alumina substrate 102. At least one of the take-off electrode 106, the lower surface electrode 108, and the connection electrode 110 may be formed using the conductive paste of this embodiment. It is particularly preferable to form the take-off electrode 106 using the conductive paste of this embodiment. In addition, a nickel plating film 112 and a tin plating film 114 can be disposed on the upper surface (the surface opposite to the alumina substrate 102) of the extraction electrode 106, the lower surface electrode 108 and the connecting electrode 110.

[0077] By using the conductive paste of this embodiment, electrodes with high sulfidation resistance, low resistance, and relatively low cost can be formed, thus enabling electronic devices such as chip resistors with highly reliable electrodes to be obtained.

[0078] Example

[0079] The present invention will be specifically illustrated by the following examples, but the present invention is not limited to these examples.

[0080] [Preparation of conductive paste]

[0081] The conductive paste is prepared by mixing components (A) to (E) in the proportions shown in Tables 1 and 2. All proportions of the components shown in Tables 1 and 2 are expressed in parts by weight. Furthermore, the average particle size refers to the volumetric median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement.

[0082] (A) Metal particles

[0083] As (A) metal particles, the following metal particles A1 to A7 are used. The Ag / Sn values ​​below are weight ratios.

[0084] Metal particles A1 (alloy particles): weight ratio Ag / Sn = 98 / 2, average particle size (D50) 2.5μm.

[0085] Metal particles A2 (alloy particles): weight ratio Ag / Sn = 95 / 5, average particle size (D50) 2.5μm

[0086] Metal particles A3 (alloy particles): weight ratio Ag / Sn = 93 / 7, average particle size (D50) 2.5μm

[0087] Metal particles A4: Ag particles, average particle size (D50) 2.5 μm

[0088] Metal particles A5: A mixture of Ag particles (average particle size (D50) 2.5 μm) and Sn particles (average particle size (D50) 2.5 μm), with a weight ratio of Ag particles / Sn particles of 93 / 7.

[0089] Metal particles A6 (alloy particles): weight ratio Ag / Sn = 90 / 10, average particle size (D50) 2.5μm

[0090] Metal particles A7 (alloy particles): weight ratio Ag / Sn = 70 / 30, average particle size (D50) 2.5μm

[0091] (B) Glass Material

[0092] As (B) glass material, the following glass materials B1 and B2 are used.

[0093] Glass frit B1: Titanium borosilicate glass frit (composition: SiO2-B2O3-Na2O-TiO2 system), softening point (Ts) = 570℃, average particle size (D50) 1.4μm

[0094] Glass frit B2: Barium borosilicate glass frit (composition: SiO2-B2O3-BaO system), softening point (Ts) = 750℃, average particle size (D50) 1.2μm.

[0095] (C) Thermoplastic resin

[0096] Thermoplastic resin C1: Ethyl cellulose resin (STD-200, manufactured by Dow Chemical Company)

[0097] Thermoplastic resin C2: Ethyl cellulose resin (STD-4, manufactured by Dow Chemical Company)

[0098] (D) Silica filler

[0099] As (D) silica filler, the following silica filler is used.

[0100] Spherical silica (SiO2) powder, average particle size (D50) 2μm

[0101] (E) Solvent

[0102] Texanol (manufactured by Eastman Chemical Company) was used as the solvent.

[0103] [Production of the experimental film]

[0104] Test pieces were fabricated using a prepared conductive paste in the following sequence: First, the conductive paste was screen-printed onto a 20mm × 20mm × 1mm (t) alumina substrate. This created 20 patterns on the alumina substrate, each consisting of a square pad with a side width of 1.5mm. A 250-mesh stainless steel mask was used for pattern formation. Next, the conductive paste was dried at 150°C for 10 minutes using a heat-sealing dryer. After drying, the conductive paste was fired in a firing furnace. The firing temperature was maintained at 850°C for 10 minutes, for a total firing time of 60 minutes.

[0105] [Determination of resistance in thin-film materials]

[0106] First, the sheet resistance R0 of the square pad pattern formed on the alumina substrate used as the test piece was measured. The sheet resistance R0 was measured using a testing machine via the four-terminal method. Next, a sulfur resistance test under high sulfur environment was conducted according to ASTM B809-95 (60°C, 1000 hours). Specifically, 200g of 0.5wt% potassium nitrate aqueous solution was sandwiched in the bottom of a dryer, 50g of sulfur powder and the test piece were placed on an orifice plate, the dryer was covered, and the dryer was stored at 60°C for 1000 hours, thereby conducting an accelerated sulfurization test of the electrode. After this storage, the sheet resistance R1 was measured. To evaluate the electrode degradation caused by sulfurization, the rate of change of sheet resistance before and after storage was calculated using the following formula. The rate of change of sheet resistance for the examples and comparative examples is shown in Tables 1 and 2.

[0107] The rate of change of the resistance of the thin sheet = (R1-R0) / R0

[0108] [Photographs taken using SEM]

[0109] exist Figure 2 The image shown is a cross-section of a test piece prepared under the same conditions as in Example 4, where the rate of change in sheet resistance is relatively small, taken at 1500x magnification using a scanning electron microscope (SEM). Figure 3 The image shown is a cross-section of a test piece prepared under the same conditions as Comparative Example 3 (which is an insulator) with a large rate of change in sheet resistance, taken by SEM at 1500x magnification. Additionally, the test piece was observed by SEM after being stored in a sulfur atmosphere (60°C) for 1000 hours.

[0110] As can be seen from the results shown in Tables 1 and 2, the change rate of sheet resistance of the electrode patterns obtained by firing the conductive pastes of Examples 1 to 10 was less than 11%, which is relatively low. In contrast, the change rate of sheet resistance of the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 4 was more than 95%, or the sheet resistance after storage in the accelerated curing test was too high to be measured.

[0111] exist Figure 2 In the SEM image of the illustrated embodiment, the portion where silver sulfide 20 is formed by sulfidation is a portion with a film thickness d = 50 nm on the surface of the sintered body 10 (silver particles) of the conductive paste. Figure 2 In the illustrated embodiment, a film of silver sulfide is deposited on the electrode surface, but sulfur does not penetrate into the electrode interior. Therefore, no cracks or other defects are observed inside the electrode. That is, in Figure 2 In the illustrated embodiment, it is clear that the formation of silver sulfide 20 has almost no effect on the sintered body 10.

[0112] On the other hand, Figure 3 In the SEM image of the comparative example shown, regarding the portion where silver sulfide 20 is formed by sulfidation, in the sintered body 10 (silver particles) of the conductive paste, silver sulfide 20 is formed to a film thickness d = 250 nm. That is, compared with... Figure 2 Compared to the embodiments shown, it can be understood that, Figure 3 In the comparative example shown, the silver sulfide film is thick, extending into the interior of the electrode. Therefore, as in... Figure 3 As clearly shown in the SEM images, in Figure 3 In the case of the test piece, cracks 30 were generated inside the sintered body 10 (electrode). That is, in the comparative example, the reason for the significant increase in the sheet resistance is believed to be due to cracks caused by the effect of sulfidation.

[0113] [Table 1]

[0114]

[0115] [Table 2]

[0116]

[0117] Explanation of reference numerals in the attached figures

[0118] 10 Sintered bodies of conductive paste

[0119] 20 Silver Sulfide

[0120] 30 cracks

[0121] 100mm surface mount resistor

[0122] 102 alumina substrate

[0123] 104 Resistor

[0124] 106 Remove the electrodes

[0125] 108 Lower surface electrode

[0126] 110 Connecting electrodes

[0127] 112 Nickel plating

[0128] 114 Tin plating film

[0129] d Silver sulfide film thickness.

Claims

1. A surface mount resistor, characterized in that, It has electrodes obtained by sintering conductive paste. The conductive paste contains: (A) Alloy particles containing Ag and Sn; (B) Glass material; and (C) Thermoplastic resin, The Sn content in the alloy particles of (A) is less than 10% by weight. The content of the glass frit in (B) is 1 to 20 parts by weight relative to 100 parts by weight of the alloy particles in (A).

2. The surface mount resistor according to claim 1, characterized in that, The weight percentage of Ag in the (A) alloy particles is 50% or more.

3. The surface mount resistor according to claim 1 or 2, characterized in that, The content of the glass frit in (B) is 1.5 to 15 parts by weight relative to 100 parts by weight of the alloy particles in (A).

4. The surface mount resistor according to claim 1 or 2, characterized in that, The conductive paste further comprises: (D) silica filler.

5. The surface mount resistor according to claim 4, characterized in that, The glass frit (B) contains SiO2 and TiO2. The weight ratio of SiO2 B contained in the glass frit (B) to the weight D of SiO2 contained in the silica filler (D) is B:D = 1:0.25 to 1:9.

8.

6. The surface mount resistor according to claim 1 or 2, characterized in that, The glass material (B) includes titanium borosilicate glass material and barium borosilicate glass material.

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