Conductive paste, electrode, and chip resistor

Abstract

The present invention provides an electroconductive paste which is capable of forming a relatively low-cost electrode that has high sulfurization resistance, while having a low resistance.　An electroconductive paste which contains (A) alloy particles containing Ag and Sn, (B) a glass frit and (C) a thermoplastic resin, wherein the weight ratio of Sn in the alloy particles (A) is less than 10% by weight.

Description

Technical Field

[0001] The present invention relates to a conductive paste used, for example, for forming electrodes of electronic components. The present invention also relates to an electrode formed using the conductive paste and a chip resistor having the electrode.

Background Art

[0002] For forming electrodes of a chip resistor, which is one of electronic components, a conductive paste containing silver powder is used. FIG. 1 shows an example of a cross-sectional structure of a chip resistor 100. The chip resistor 100 has a rectangular alumina substrate 102, and a resistor 104 and a lead-out electrode 106 for taking out electricity from the resistor 104 are formed on the upper surface of the alumina substrate 102. Further, a lower surface electrode 108 for mounting the chip resistor 100 on a substrate is formed on the lower surface of the alumina substrate 102. Furthermore, a connection electrode 110 for connecting the lead-out electrode 106 and the lower surface electrode 108 is formed on an end surface of the alumina substrate 102. The lead-out electrode 106 and the lower surface electrode 108 are each formed by applying a conductive paste on the upper surface and the lower surface of the alumina substrate 102 by printing and then firing. A nickel plating film 112 and a tin plating film 114 are generally formed on the lead-out electrode 106, the lower surface electrode 108, and the connection electrode 110.

[0003] Since the lead-out electrode 106 and the lower surface electrode 108 each have different required characteristics, they are generally formed using different conductive pastes. For example, for forming the lead-out electrode 106, a conductive paste having good matching properties with the resistor 104 is used. Further, when the resistance value of the resistor 104 is low, it is required that the resistance value of the lead-out electrode 106 is also low. Therefore, for forming the lead-out electrode 106, a conductive paste capable of forming a low-resistance electrode is used.

[0004] Conventionally, as a conductive paste used for forming electrodes, a conductive paste containing silver powder and glass frit disclosed in Patent Documents 1 and 2 is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Disclosure of the Invention

[0006] In automobiles, thermal power plants, etc., fossil fuels are burned, and a large amount of sulfur oxides are discharged into the atmosphere. Also, in sewage treatment plants, waste treatment plants, etc., sulfur is reduced by anaerobic bacteria to generate hydrogen sulfide. Therefore, components containing sulfur such as sulfur oxides and hydrogen sulfide exist in the atmosphere.

[0007] When components containing sulfur in the atmosphere reach the surface of silver, sulfur components adhere to the surface of silver and react with silver to form silver sulfide. For example, in electrodes mainly made of silver such as the electrodes of chip resistors, the same reaction occurs, so the silver inside the electrode may turn into silver sulfide. When silver sulfide is generated inside the electrode, the electrode may be disconnected. Therefore, in devices such as chip resistors having electrodes made of silver, malfunction may occur. Such a phenomenon is called disconnection due to sulfidation.

[0008] In order to suppress disconnection due to sulfidation, electrodes mainly made of silver used in devices such as chip resistors require electrodes with high sulfidation resistance.

[0009] In order to suppress disconnection due to sulfidation, it has been proposed to use palladium alone or add a predetermined amount (for example, about 20% by weight) of palladium as the conductive particles of the conductive paste for forming the electrodes. However, since the price of palladium is high, there is a problem that the cost of the conductive paste increases due to the use of palladium alone or the addition of palladium.

[0010] Therefore, an object of the present invention is to provide a conductive paste that has high sulfur resistance, low resistance, and can form an electrode at a relatively low cost.

[0011] To solve the above problems, the present invention has the following configuration.

[0012] (Configuration 1) Configuration 1 of the present invention contains (A) alloy particles containing Ag and Sn, (B) glass frit, (C) a thermoplastic resin, and is a conductive paste in which the weight ratio of Sn in the (A) alloy particles is less than 10% by weight.

[0013] (Configuration 2) Configuration 2 of the present invention is the conductive paste of Configuration 1, in which the weight ratio of Ag in the (A) alloy particles is 50% by weight or more.

[0014] (Configuration 3) Configuration 3 of the present invention is the conductive paste of Configuration 1 or 2, in which the content of the (B) glass frit is 2 to 20 parts by weight with respect to 100 parts by weight of the (A) alloy particles.

[0015] (Configuration 4) Configuration 4 of the present invention is the conductive paste of any one of Configurations 1 to 3, further containing (D) a silica filler.

[0016] (Configuration 5) Configuration 5 of the present invention is such that the (B) glass frit contains SiO 2 and TiO 2 and the ratio of the weight B of SiO 2 contained in the (B) glass frit to the weight D of SiO 2 contained in the (D) silica filler is weight B: weight D = 1: 0.25 to 1: 9.8, which is the conductive paste according to Configuration 4.

[0017] (Configuration 6) Configuration 6 of the present invention is an electrode obtained by firing any one of Conductive Pastes 1 to 5.

[0018] (Configuration 7) Configuration 7 of the present invention is a chip resistor having the electrode described in Configuration 6.

[0019] According to the present invention, it is possible to provide a conductive paste capable of forming an electrode having high sulfidation resistance, low resistance, and relatively low cost.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be specifically described. Note that the following embodiments are forms for embodying the present invention and do not limit the present invention within its scope.

[0022] The conductive paste of the present embodiment contains (A) alloy particles, (B) glass frit, and (C) a thermoplastic resin. The conductive paste of the present embodiment can be preferably used for forming electrodes of devices such as chip resistors having electrodes made of silver.

[0023] Hereinafter, the components contained in the conductive paste of the present embodiment will be described.

[0024] (A) Alloy particles The conductive paste of this embodiment contains (A) alloy particles. The (A) alloy particles contain silver (Ag) and tin (Sn). By the (A) alloy particles containing Sn, the sulfidation of Ag can be suppressed. Therefore, by using the conductive paste of this embodiment, an electrode having high sulfidation resistance can be formed.

[0025] Note that the (A) alloy particles can contain metals other than Ag and Sn. However, in order to surely obtain an electrode having low electrical resistance and high sulfidation resistance, it is preferable that the (A) alloy particles consist of only Ag and Sn. In this specification, "the (A) alloy particles consist of only Ag and Sn" means that, as the (A) metal particles, metals other than Ag and Sn are not intentionally blended, and it does not exclude the case of containing metals other than Ag and Sn that are unavoidably mixed in.

[0026] (A) The alloy particles can contain metals such as Zn, In, Al, and Si as metals other than Ag and Sn within a range that does not impair the effects of this embodiment.

[0027] In the conductive paste of this embodiment, the weight ratio of Sn in the (A) alloy particles is preferably less than 10% by weight. More specifically, the weight ratio of Sn in the (A) alloy particles is preferably 1% by weight or more and less than 10% by weight, more preferably 1.5% by weight or more and 9% by weight or less, still more preferably 2% by weight or more and 8% by weight or less, and particularly preferably 4% by weight or more and 8% by weight or less. When the weight ratio of Sn is too high, the electrical resistance as an electrode may become too high. Also, when the weight ratio of Sn is low, the improvement in sulfidation resistance may be small. In particular, when the weight ratio of Sn is less than 2% by weight, the sulfidation resistance may easily deteriorate.

[0028] The conductive paste of this embodiment preferably has a silver weight ratio in the alloy particles of 50 wt% or more, more preferably 70 wt% or more, and still more preferably more than 90 wt%. The electrical resistance of silver is low compared to other metals. Therefore, by having the silver weight ratio within a predetermined range, an electrode with a relatively low electrical resistance can be obtained.

[0029] (A) The shape of the alloy particles is not particularly limited. For example, spherical, granular, flaky and / or scaly alloy particles can be used.

[0030] (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 means the volume-based median diameter (D50) obtained by the laser diffraction scattering particle size distribution measurement method.

[0031] (A) The method for manufacturing the alloy particles is not particularly limited. For example, it can be manufactured by a reduction method, a pulverization method, an electrolysis method, an atomization method, a heat treatment method, or a combination thereof. The flaky alloy particles can be manufactured, for example, by crushing spherical or granular alloy particles with a ball mill or the like.

[0032] (B) Glass frit The conductive paste of this embodiment contains (B) glass frit.

[0033] (B) The glass frit is SiO 2 and TiO 2It is preferably included. By the conductive paste containing (B) glass frit, the adhesion strength of the electrode obtained by firing the conductive paste to the substrate is improved. The glass frit is not particularly limited, but preferably a glass frit having a softening point of 300 °C or higher, more preferably a softening point of 400 to 900 °C, and still more preferably a softening point of 500 to 800 °C can be used. The softening point of the glass frit can be measured using a thermogravimetric analyzer (for example, TG-DTA2000SA manufactured by BRUKER AXS).

[0034] (B) Examples of the glass frit include titanium borosilicate (TiO 2 system), and glass frits such as barium borosilicate system. Further, examples of the glass frit include bismuth borosilicate system, alkali metal borosilicate system, alkaline earth metal borosilicate system, zinc borosilicate system, lead borosilicate system, lead borate system, lead silicate system, bismuth borate system, and zinc borate system. These glass frits can also be used as a mixture of two or more. The glass frit is preferably lead-free from the viewpoint of environmental consideration.

[0035] The glass frit preferably contains at least one selected from the group consisting of ZnO, BaO, Na 2 O, CaO and Al 2 O 3 It is more preferably included ZnO, BaO, Na 2 O and Al 2 O 3 .

[0036] The average particle size of the glass frit is preferably 0.1 to 20 μm, more preferably 0.2 to 10 μm, and most preferably 0.5 to 5 μm. The average particle size here means the volume-based median diameter (D50) obtained by the laser diffraction scattering method for particle size distribution measurement.

[0037] In the conductive paste of the present embodiment, the content of (B) glass frit is preferably 1 to 20 parts by weight, more preferably 1.5 to 15 parts by weight, and still more preferably 2 to 10 parts by weight with respect to 100 parts by weight of (A) alloy particles. When the content of the glass frit is less than this range, the adhesion of the electrode obtained by firing the conductive paste to the substrate decreases. When the content of the glass frit is more than this range, the resistance value of the electrode obtained by firing the conductive paste becomes high. Incidentally, when the content of the glass frit is relatively small, a low-resistance electrode can be obtained. Also, when the content of the glass frit is relatively large, an electrode excellent in chemical resistance can be obtained. Chemical resistance is a property required because a pretreatment for plating is necessary when forming a plating film on the surface of the electrode. The pretreatment for plating is performed for the purpose of removing contaminants from the surface of the electrode, activating the surface of the electrode, and making it in a clean state suitable for plating. The contaminants to be removed can be roughly classified into organic and inorganic types. The pretreatment process is not a process for removing all contaminants in a single process. For example, organic substances are removed in a process using an alkaline cleaning agent. Inorganic substances are removed in a process using an acid cleaning agent. Therefore, high chemical resistance is required for the electrode.

[0038] As the temperature rises, the glass frit softens and the sintering of silver progresses in the conductive paste. When the glass frit content is high, the glass component may be extruded onto the surface of the sintered body. In that case, the surface of the sintered body may be covered with the glass component. 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 also the conductivity of the sintered body can be improved even when the surface of the sintered body is covered with the glass component. Since the alloy particles (A) of the present embodiment are alloy particles containing Ag and Sn, they have lower sinterability than Ag particles. Therefore, the occurrence of the phenomenon that the surface of the sintered body is covered with the glass component can be suppressed. Therefore, the content of the glass frit can be increased, and an electrode with excellent chemical resistance can be obtained as compared with Ag particles. Regarding the (D) silica filler having the same properties and functions as the glass frit, its content can also be increased, so that an electrode with excellent chemical resistance can be obtained.

[0039] (C) Thermoplastic resin The conductive paste of the present embodiment contains (C) a thermoplastic resin.

[0040] The thermoplastic resin connects the silver powders together in the conductive paste. As the thermoplastic resin, one that burns out during the firing of the conductive paste can be used.

[0041] As the thermoplastic resin, for example, cellulose resins such as ethyl cellulose and nitrocellulose, acrylic resins, alkyd resins, saturated polyester resins, butyral resins, polyvinyl alcohol, and hydroxypropyl cellulose can be used. These resins can be used alone or in combination of two or more.

[0042] (C) The content of the thermoplastic resin is preferably 0.5 to 40 parts by weight, more preferably 1 to 35 parts by weight, based on 100 parts by weight of the alloy particles. When the content of the thermoplastic resin in the conductive paste is within the above range, the coatability of the conductive paste onto the substrate and the paste leveling property are improved, and the printed shape is excellent. On the other hand, when the content of the thermoplastic resin exceeds the above range, the amount of the thermoplastic resin contained in the conductive paste is too large. Therefore, there is a possibility that the electrode cannot be formed with high precision.

[0043] (D) Silica filler The conductive paste of the present embodiment preferably further contains (D) silica filler.

[0044] (D) As the silica filler, for example, spherical silica (SiO 2 ) particles commercially available as a semiconductor encapsulant can be used. The shape of the silica filler may be other than spherical. The production method of the silica filler is not particularly limited, and silica fillers produced by known methods such as a spraying method can be used. The average particle size of the silica filler is preferably 20 nm or more and 5 μm or less, and more preferably 1 μm or more and 3 μm or less. The average particle size referred to here means the volume-based median diameter (D50) obtained by the laser diffraction scattering type particle size distribution measurement method.

[0045] In the conductive paste of the present embodiment, (B) the glass frit contains SiO 2 and TiO 2 , and the ratio of the weight B of SiO 2 contained in (B) the glass frit to the weight D of SiO 2 contained in (D) the silica filler is preferably weight B: weight D = 1: 0.25 to 1: 9.8, and more preferably weight B: weight D = 1: 0.25 to 1: 3.5.

[0046] The conductive paste of the present embodiment contains (D) silica filler, whereby the chemical resistance of the resulting electrode is improved. On the other hand, if there is too much silica filler, the resistance value of the resulting electrode becomes high, making it difficult to obtain a low-resistance electrode. In addition, (D) silica filler has the same function as (B) glass frit. Therefore, by the ratio of the weight B of SiO 2 contained in (B) glass frit and the weight D of SiO 2 contained in (D) silica filler being within the range of the above-described ratio, appropriate chemical resistance can be obtained and a low-resistance electrode can be obtained.

[0047] (E) Solvent The conductive paste of the present embodiment may contain (E) solvent. Examples of the solvent include alcohols such as methanol, ethanol, and isopropyl alcohol (IPA), organic acids such as ethylene 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 content of the solvent is not particularly limited. The content of the solvent is preferably 1 to 100 parts by weight, more preferably 5 to 60 parts by weight, based on 100 parts by weight of (A) alloy particles.

[0048] The viscosity of the conductive paste of the present embodiment is preferably 50 to 700 Pa·s (shear rate: 4.0 sec -1 ), more preferably 100 to 300 Pa·s (shear rate: 4.0 sec -1 ). By adjusting the viscosity of the conductive paste within this range, the coatability and handleability of the conductive paste on the substrate are improved, and it becomes possible to coat the substrate with the conductive paste in a uniform thickness. The viscosity of the conductive paste can be measured using an HB-type viscometer SC4-14 spindle (manufactured by Brookfield).

[0049] The conductive paste of this embodiment may contain other additives, such as dispersants, rheology modifiers, pigments, etc.

[0050] The conductive paste of this embodiment can be manufactured by mixing the above components using, for example, a lycra machine, a pot mill, a three-roll mill, a rotary mixer, and / or a twin-screw mixer, etc.

[0051] This embodiment is an electrode obtained by firing the conductive paste of the above-described embodiment.

[0052] This embodiment is an electrode formed using the conductive paste of the above-described embodiment as a material. The electrode of this embodiment can be obtained by applying the conductive paste to a substrate and firing it. Therefore, the electrode of this embodiment can contain (A’) alloy particles containing Ag and Sn, and (B’) a glass component made of glass frit. (A’) The alloy particles are in a sintered state. The weight ratio of Sn in the (A’) alloy particles of the electrode of this embodiment is less than 10% by weight. Note that since the (C) thermoplastic resin and (E) solvent contained in the conductive paste vaporize or burn during firing, the electrode substantially does not contain the (C) thermoplastic resin and (E) solvent.

[0053] The electrode of this embodiment can further contain (D’) a silica filler in addition to the (A’) alloy particles and the (B’) glass component. Also, the weight ratio of Ag in the (A’) alloy particles, the content of the (B’) glass component, and the composition of the (B’) glass component of the electrode of this embodiment correspond to the weight ratio and composition of the (A) alloy particles and the (B) glass frit contained in the conductive paste used as the material.

[0054] The sheet resistance of the thin film serving as the electrode of this embodiment varies depending on the film thickness, but can generally be about 10 mΩ / □ (10 mΩ / square) or 10 mΩ / □ or less. Therefore, it can be preferably used for forming an electrode that is required to have low resistance.

[0055] Next, a method of forming an electrode on a substrate using the conductive paste of the present embodiment will be described. First, the conductive paste is applied onto the substrate. The application method is arbitrary, and for example, it can be applied using a known method such as dispensing, jet dispensing, stencil printing, screen printing, pin transfer, or stamping.

[0056] After applying the conductive paste onto the substrate, the substrate is put into a firing furnace or the like. Then, the conductive paste applied onto the substrate is fired at 500 to 900 °C, more preferably 600 to 900 °C, and still more preferably 700 to 900 °C. Thereby, the solvent component contained in the conductive paste evaporates at 300 °C or lower, the resin component burns out at 400 °C to 600 °C, and a fired body of the conductive paste is formed. The electrode thus obtained has high chemical resistance and excellent adhesion to the substrate.

[0057] The present embodiment is a chip resistor having the above-described electrode.

[0058] The conductive paste of the present embodiment can be used for forming circuits of devices such as electronic components, forming electrodes, and joining devices such as electronic components to substrates. Further, the conductive paste of the present embodiment can be preferably used for forming electrodes of chip resistors.

[0059] FIG. 1 shows an example of the cross-sectional structure of the chip resistor 100 of the present embodiment. The chip resistor 100 can include a rectangular alumina substrate 102, a resistor 104 disposed on the surface of the alumina substrate 102, and a lead-out electrode 106. The lead-out electrode 106 is an electrode for extracting electricity from the resistor 104. Further, a bottom electrode 108 for mounting the chip resistor 100 on a substrate can be disposed on the lower surface of the alumina substrate 102. Furthermore, a connection electrode 110 for connecting the lead-out electrode 106 and the bottom electrode 108 can be disposed on an end surface of the alumina substrate 102. At least one of the lead-out electrode 106, the bottom electrode 108, and the connection electrode 110 can be formed using the conductive paste of the present embodiment. In particular, the lead-out electrode 106 is preferably formed using the conductive paste of the present embodiment. Note that a nickel plating film 112 and a tin plating film 114 can be disposed on the upper surfaces (surfaces opposite to the alumina substrate 102) of the lead-out electrode 106, the bottom electrode 108, and the connection electrode 110.

[0060] By using the conductive paste of the present embodiment, an electrode having high sulfidation resistance, low resistance, and relatively low cost can be formed, so that an electronic device such as a chip resistor in which a highly reliable electrode is formed can be obtained.

Example

[0061] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[0062] [Preparation of Conductive Paste] The following components (A) to (E) were mixed at the ratios shown in Tables 1 and 2 to prepare a conductive paste. Note that the ratios of the respective components shown in Tables 1 and 2 are all indicated in parts by weight. The average particle size means the volume-based median diameter (D50) obtained by the laser diffraction scattering particle size distribution measurement method.

[0063] (A) Metal particles (A) As the metal particles, the following metal particles A1 to A7 were used. The following Ag / Sn numerical values are by weight ratio. Metal particle A1 (alloy particle): Weight ratio Ag / Sn = 98 / 2, average particle size (D50) 2.5 μm. Metal particle A2 (alloy particle): Weight ratio Ag / Sn = 95 / 5, average particle size (D50) 2.5 μm Metal particle A3 (alloy particle): Weight ratio Ag / Sn = 93 / 7, average particle size (D50) 2.5 μm Metal particle A4: Ag particle, average particle size (D50) 2.5 μm Metal particle A5: Mixture of Ag particles (average particle size (D50) 2.5 μm) and Sn particles (average particle size (D50) 2.5 μm), weight ratio Ag particles / Sn particles = 93 / 7 Metal particle A6 (alloy particle): Weight ratio Ag / Sn = 90 / 10, average particle size (D50) 2.5 μm Metal particle A7 (alloy particle): Weight ratio Ag / Sn = 70 / 30, average particle size (D50) 2.5 μm

[0064] (B) Glass frit (B) As the glass frit, the following glass frits B1 and B2 were used. Glass frit B1: Titanium borosilicate glass frit (composition: SiO 2 -B 2 O 3 -Na 2 O-TiO 2 system), softening point (Ts) = 570 °C, average particle size (D50) 1.4 μm Glass frit B2: Barium borosilicate glass frit (composition: SiO 2 -B 2 O 3 -BaO system), softening point (Ts) = 750 °C, average particle size (D50) 1.2 μm

[0065] (C) Thermoplastic resin Thermoplastic resin C1: Ethyl cellulose resin (STD-200, manufactured by Dow Chemical Company) Thermoplastic resin C2: Ethyl cellulose resin (STD-4, manufactured by Dow Chemical Company)

[0066] (D) Silica filler As the (D) silica filler, the following silica filler was used. Spherical silica (SiO 2 ) powder, average particle size (D50) 2 μm

[0067] (E) Solvent As the solvent, Texanol (manufactured by Eastman Chemical Company) was used.

[0068] [Preparation of test pieces] Using the prepared conductive paste, test pieces were prepared according to the following procedure. First, the conductive paste was applied onto a 20 mm × 20 mm × 1 mm (t) alumina substrate by screen printing. As a result, 20 patterns each having a square pad shape with a side of 1.5 mm were formed on the alumina substrate. For the formation of the patterns, a 250-mesh stainless steel mask was used. Next, the conductive paste was dried at 150 °C for 10 minutes using a hot air dryer. After drying the conductive paste, the conductive paste was fired using a firing furnace. The firing temperature was kept at 850 °C for 10 minutes, and the total firing time was 60 minutes.

[0069] [Measurement of sheet resistance] First, the sheet resistance R 0 of the square pad pattern formed on the alumina substrate as the test piece was measured. The sheet resistance R 0 was measured by the four-terminal method using a tester. Next, a sulfidation resistance test in a high-sulfur environment was conducted in accordance with ASTM B809-95 (60 °C, 1000 hours). That is, 200 g of a 0.5 wt% aqueous potassium nitrate solution was placed at the bottom of a desiccator, 50 g of sulfur powder and the test piece were placed on a watch glass, the desiccator was covered, and stored at 60 °C for 1000 hours to conduct an accelerated test for sulfidation of the electrodes. After this storage, the sheet resistance R 1 was measured. In order to evaluate the deterioration of the electrodes due to sulfidation, the change rate of the sheet resistance before and after storage was calculated by the following formula. Tables 1 and 2 show the change rates of the sheet resistance of the examples and comparative examples. Change rate of sheet resistance = (R 1 - R 0 ) / R 0

[0070] [Photograph taken by SEM] Figure 2 shows SEM photographs of cross-sections of test pieces fabricated under the same conditions as in Example 4, where the change rate of sheet resistance was relatively small, taken at a magnification of 1500 times with a scanning electron microscope (SEM). Figure 3 shows SEM photographs of cross-sections of test pieces fabricated under the same conditions as in Comparative Example 3, where the change rate of sheet resistance was large (it was an insulator), taken at a magnification of 1500 times with an SEM. Note that the test pieces were subjected to SEM observation after being stored in a sulfur atmosphere (60°C) for 1000 hours.

[0071] As can be seen from the results shown in Table 1 and Table 2, the electrode patterns obtained by firing the conductive pastes of Examples 1 to 10 had a change rate of sheet resistance of 11% or less, which was relatively low. In contrast, the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 4 had a change rate of sheet resistance of 95% or more, or the sheet resistance after the storage in the accelerated sulfidation test was too high to be measured.

[0072] In the SEM photographs of the examples shown in Figure 2, the portion where silver sulfide 20 was formed due to sulfidation was a portion with a film thickness d of about 50 nm on the surface of the fired body 10 (silver particles) of the conductive paste. In the example shown in Figure 2, although a film of silver sulfide was deposited on the electrode surface, sulfur did not penetrate to the inside of the electrode. Therefore, no cracks or the like were observed inside the electrode. That is, it is clear that in the example shown in Figure 2, the formation of silver sulfide 20 had almost no effect on the fired body 10.

[0073] On the other hand, in the SEM photograph of the comparative example shown in Fig. 3, silver sulfide 20 was formed up to a film thickness d of about 250 nm in the fired body 10 (silver particles) of the conductive paste due to sulfidation. That is, compared with the example shown in Fig. 2, in the case of the comparative example shown in Fig. 3, the thin film of silver sulfide was thick, and it can be understood that sulfidation occurred even inside the electrode. Therefore, as is clear from the SEM photograph of Fig. 3, in the case of the test piece of Fig. 3, cracks 30 occurred inside the fired body 10 (electrode). That is, it is considered that the reason for the large increase in sheet resistance in the comparative example is due to the cracks generated by the influence of sulfidation.

[0074]

Table 1

[0075]

Table 2

Explanation of Signs

[0076] 10 Fired body of conductive paste 20 Silver sulfide 30 Crack 100 Chip resistor 102 Alumina substrate 104 Resistor 106 Take-out electrode 108 Bottom electrode 110 Connection electrode 112 Nickel plating film 114 Tin plating film d Film thickness of silver sulfide

Claims

1. (A) alloy particles containing Ag and Sn, (B) glass frit, (C) a thermoplastic resin, and contains, (A) the weight ratio of Sn in the alloy particles is 1% by weight or more and 9% by weight or less, (A) the weight ratio of Ag in the alloy particles is 50% by weight or more, a conductive paste. 】

2. (A) the weight ratio of Ag in the alloy particles is 50% by weight or more, the conductive paste according to claim 1. 】

3. The content of the (B) glass frit is 1 to 20 parts by weight with respect to 100 parts by weight of the (A) alloy particles, the conductive paste according to claim 1 or 2. 】

4. (D) further comprising a silica filler, the conductive paste according to any one of claims 1 to 3. 】

5. The aforementioned (B) glass frit contains SiO ２ and TiO ２ and includes The weight B of SiO contained in the said (B) glass frit ２ and the weight D of SiO contained in the said (D) silica filler ２ The conductive paste according to claim 4, wherein the ratio of weight B:weight D is 1:0.25 to 1:9.

8. 】

6. An electrode obtained by firing the conductive paste according to any one of claims 1 to 5. 】

7. A chip resistor having the electrode according to claim 6.

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