JP2008182128A - Chip resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip resistor that prevents not only the disconnection of side electrode wires but also the deterioration of electrical characteristics, even in the case where the chip resistor having a sulfide resistance top electrode formed by containing palladium therein is used under high sulfide gas concentration conditions. <P>SOLUTION: In the chip resistor, the top electrode 30 contains 15-30% in weight percent of the total weight of palladium, a side electrode 60 being formed of a material having the sulfide resistance characteristics. More specifically, the side electrode 60 is formed of a resin and silver based thick film, the silver being comprised of a scaly silver powder and spherical silver powder. The average maximum width of each scaly silver powder is 13-17 μm, and the average particle diameter of each spherical silver powder is 0.5 μm or less. The proportion of the spherical silver powder to the whole silver is 60-70% in weight percent. Further, the length T in a direction between electrodes in a region where the side electrode 60 is superimposed with the top electrode is 0.2-0.3 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chip resistor, and more particularly to a chip resistor having anti-sulfur characteristics.

  A conventional chip resistor is formed by, for example, a configuration as shown in FIG. That is, the chip resistor 105 includes the insulating substrate 10, the electrode unit 20, the resistor 80, the cover coat 90, and the protective film 98, and the electrode unit 20 is paired on the left and right sides of the insulating substrate 10. The upper electrode 30, the lower electrode 40, the side electrode 60, and the plating 70 are provided. This plating 70 is formed of two layers of nickel plating 72 and tin plating 74. Here, the end portion of the plating 70 is fixed in contact with the end portion of the protective film 98, and is generally formed so as not to expose the top electrode 30 that is easily corroded.

However, in the configuration of FIG. 1, since the adhesive strength between the plating 70 in contact with the protective film 98 and the protective film 98 is generally low, a gap is formed between the protective film 98 and the plating 70 due to repeated contraction and expansion due to thermal stress or the like. Is formed. When this gap reaches the upper surface electrode 30, the upper surface electrode 30 generally formed of a silver-based thick film is used when the upper surface electrode is used in a corrosive atmosphere in which a large amount of sulfur gas (for example, hydrogen sulfide) is present. Silver contained in 30 reacts with the sulfide gas to produce silver sulfide (Ag ₂ S), which is an insulator, and the top electrode 30 is corroded. In other words, silver and sulfide react with sulfide gas, Ag ₂ S whiskers are formed, the upper electrode with the growth of the Ag ₂ S whiskers gone partially lost, fulfill sufficiently function as a conductor Disappear. That is, when the upper surface electrode 30 is disconnected, there is a possibility of causing a failure such as a change in the resistance value of the chip resistor.

  As described above, the end portion of the protective film 98 becomes a so-called sulfidation point, and the sulfurized gas enters from a slight gap between the protective film 98 and the plating 70 and gradually deepens the silver of the upper surface electrode 30 depending on the concentration and time. In an atmosphere where a large amount of sulfur gas exists, the silver on the top electrode may disappear and break in 1 to 3 years.

Moreover, as shown in Patent Document 1, it is possible to prevent sulfidation of the upper surface electrode 30 by containing palladium in the upper surface electrode 30, and in particular, the upper electrode 30 contains 20% by weight or more of palladium with respect to silver. When it is contained, the upper surface electrode 30 is hardly sulfided. That is, when the upper surface of the upper surface electrode 30 is in contact with the sulfide gas, silver on the surface layer of the upper surface electrode 30 is sulfided, and only palladium remains on the surface layer. This palladium is oxidized by water vapor or the like in the air, so that palladium oxide is formed. To produce a palladium oxide concentrated layer.
JP 2003-68502 A

  However, even if the chip resistor is made to contain sulfur in the upper surface electrode 30 by containing palladium in the upper surface electrode 30, the chip resistor is used in an environment with a high sulfur gas concentration (for example, the sulfur gas concentration is low). When used in an environment of about 10 ppm, the sulfide gas that has entered from between the protective film 98 and the plating 70 is less likely to enter the upper electrode 30 due to the palladium oxide concentrated layer. There is a possibility that the gas reaches the gap between the upper surface electrode 30 and the plating 70, the silver in the side electrode 60 is sulfided, and the side electrode 60 is disconnected. If the side electrode 60 is disconnected, it may cause a failure such as a change in the resistance value of the chip resistor.

  In particular, when the upper surface electrode 30 contains palladium and measures against sulfidation are used in an environment where the concentration of the sulfidized gas is high, the sulfurized gas that cannot enter the upper surface electrode 30 enters the gap between the upper surface electrode 30 and the plating 70. There existed a problem that it penetrate | invades easily and the side electrode 60 is easy to sulfidize.

  Therefore, the present invention prevents the disconnection of the side electrode even when a chip resistor having a top electrode containing palladium and having anti-sulfuration measures is used in an environment with a high sulfur gas concentration. An object of the present invention is to provide a chip resistor that does not impair electrical characteristics.

  The present invention was created to solve the above problems. First, a chip resistor is an insulating substrate and a pair of electrode portions provided on the insulating substrate. An upper surface electrode formed on both sides of the upper surface between the electrodes, the upper surface electrode containing 15 to 30% palladium by weight with respect to the total weight of silver and palladium contained in the upper surface electrode, and at least the upper surface of the upper surface electrode And a side electrode formed on a side surface of the insulating substrate, a side electrode formed of a material having antisulfurization characteristics, and a resistor formed by being connected between a pair of upper surface electrodes And a protective film covering a part of the upper electrode and the resistor.

  In the chip resistor having the first configuration, even when the sulfurized gas enters from the end position sulfurization point in the protective film, the upper surface electrode has a weight ratio to the total weight of silver and palladium contained in the upper surface electrode. 15 to 30% of palladium is contained, it is possible to prevent sulfidation of the upper surface electrode 30, thereby preventing deterioration of the function of the chip resistor, such as disconnection of the upper surface electrode and fluctuation of the resistance value.

  In addition, since the sulfide gas does not easily penetrate into the upper surface electrode, it contacts the side electrode along the upper surface of the upper surface electrode. It does not affect the function, that is, the electrical connection between the upper surface electrode and the solder fillet or the mechanical connection in the chip resistor (particularly, the mechanical connection of each part in the electrode part).

  Second, in the first configuration, the side electrode is formed of a resin / silver-based thick film, silver is composed of scaly silver powder and spherical silver powder, and the scaly silver powder is composed of each scaly silver powder. The average of the maximum width is 13 to 17 μm, the spherical silver powder is characterized in that the average particle diameter is formed to be 0.5 μm or less, and the ratio of the spherical silver powder to the whole silver is 60 to 70% by weight.

  According to the chip resistor having the second configuration, the side electrode contains a large amount of spherical powder, which is fine silver powder, of 60 to 70% in silver, and a resin is present between the silver powder and the silver powder. Because of the thick film structure that enters, even if the side electrode comes into contact with the sulfide gas and the silver powder is sulfided to become an insulator, most of the silver powder is a fine powder (spherical silver powder). The contact point (contact area) between silver powders is small, and the progress of sulfidation is extremely slow. Thereby, sulfidation does not reach the entire side electrode, and the function as the side electrode is not affected.

  Also, since spherical silver powder, which is a fine silver powder, is contained in a large amount of 60 to 70% in silver, when plating is formed on the surface of the side electrode, the plating is uniformly formed without generating pinholes. can do. In particular, nickel plating plays a role as a protective layer against sulfur gas, but by preventing the occurrence of nickel-plated pinholes, sulfidation of the side electrodes can be prevented.

  Thirdly, in the first or second configuration, the length in the inter-electrode direction of the region where the side surface electrode overlaps the upper surface electrode is 0.2 to 0.3 mm. . Therefore, disconnection between the side electrode and the top electrode can be prevented.

  Fourthly, in any one of the first to third configurations, the protective film is formed of a resin containing epoxy and phenol, and the ratio of phenol to the entire protective film is 40 to 40 by weight. It is characterized by 60%. Therefore, it is possible to improve the chemical resistance of the entire protective film and improve the sulfidation resistance.

  The following configuration may also be used. That is, as a fifth configuration, in any one of the first to fourth configurations, the resin in the resin / silver-based thick film is a resin containing epoxy and phenol.

  Further, as a sixth structure, in the fifth structure, the ratio to the whole resin is 30 to 36% by weight of epoxy and 64 to 70% of phenol by weight ratio.

  Further, as a seventh configuration, in any one of the first to sixth configurations, the ratio with respect to the entire side electrode is 10 to 25% by weight of resin and 75 to 90% of silver. It is characterized by that. Thereby, since silver contains much as 75 to 90% by weight ratio, since the contact location of silver powder increases and many conductive paths are formed, the resistance value of the whole side electrode is made low. be able to. In particular, when the spherical silver powder, which is a fine silver powder, is increased to 60 to 70% in silver, the individual resistance value of the spherical silver powder is high, and the contact point (contact area) between the spherical silver powders is small. Therefore, the contact resistance value is also increased, but the resistance value of the entire side electrode can be lowered by including silver as much as 75 to 90% by weight.

  Further, as an eighth configuration, in the first configuration, the side electrode is formed of a resin / nickel-based thick film containing a resin and nickel.

  According to the chip resistor according to the present invention, even when sulfurized gas enters from the end position sulfurization point in the protective film, the upper surface electrode has a weight ratio to the total weight of silver and palladium contained in the upper surface electrode. Since 15 to 30% of palladium is contained, it is possible to prevent the upper electrode 30 from being sulfided, thereby preventing deterioration of the function of the chip resistor such as disconnection of the upper electrode and fluctuation of the resistance value. In addition, since the sulfide gas does not easily penetrate into the upper surface electrode, it contacts the side electrode along the upper surface of the upper surface electrode. It does not affect the function, that is, the electrical connection between the upper surface electrode and the solder fillet or the mechanical connection in the chip resistor (particularly, the mechanical connection of each part in the electrode part).

  In the present invention, even when a chip resistor having a top electrode containing palladium and having anti-sulfuration measures is used in an environment with a high concentration of sulfur gas, disconnection of the side electrode is prevented, and the electrical resistance of the chip resistor is reduced. The purpose of providing a chip resistor that does not impair the mechanical characteristics was realized as follows.

  The chip resistor 5 based on this invention is comprised as shown in FIGS. 1-3, and has the insulating substrate 10, the electrode part 20, the resistor 80, the cover coat 90, and the protective film 98. Yes. In the figure, the Y1-Y2 direction is a direction perpendicular to the X1-X2 direction, and the Z1-Z2 direction is a direction perpendicular to the X1-X2 direction and the Y1-Y2 direction.

  Here, the insulating substrate 10 is an insulator formed of alumina having a content rate of about 96%. The insulating substrate 10 has a substantially rectangular parallelepiped shape as a whole. In the example shown in FIG. 1, the insulating substrate 10 has a rectangular shape in plan view, but may have another shape, for example, a square shape. In addition, the size of the insulating substrate 10 is 1.0 mm to 7.0 mm for the long side and 0.5 mm to 3.5 mm for the short side in plan view. Specifically, the long side is 1 mm. The short side is 0.5 mm, the long side is 2 mm, the short side is 1.2 mm, the long side is 6.4 mm, and the short side is 3.2 mm. Although the long side is 1.0 mm to 7.0 mm and the short side is 0.5 mm to 3.5 mm, any size may be used.

  Further, as shown in FIG. 1, a total of a pair of electrode portions 20 are provided along the opposing side portions of the insulating substrate 10. Specifically, the electrode part 20 is provided along one short side (side in the Y1-Y2 direction) of the insulating substrate 10, and the electrode part 20 is provided along the other short side. Yes. In addition, although the electrode part 20 was formed along the short side, it may be formed along the long side.

  Here, as shown in FIG. 1, a pair of electrode portions 20 are provided on the left and right sides of the insulating substrate 10, and includes an upper surface electrode 30, a lower surface electrode 40, a side surface electrode 60, and a plating 70. .

  A pair of upper surface electrodes 30 are formed at both end regions in the longitudinal direction (X1-X2 direction (see FIG. 1)) of the upper surface of the insulating substrate 10 and have a substantially rectangular shape in plan view. That is, one upper surface electrode 30 is formed to have a predetermined length from the end portion on the X1 side of the upper surface of the insulating substrate 10, and the other upper surface electrode 30 is an end portion on the X2 side of the upper surface of the insulating substrate 10. To a predetermined length. The width of the upper electrode 30 in the Y1-Y2 direction (width direction) is slightly larger than the width of the resistor 80 in the Y1-Y2 direction, and smaller than the width of the insulating substrate 10 in the Y1-Y2 direction. Is formed. Further, a gap is formed between the upper surface electrode 30 and the end portion of the insulating substrate 10 in the Y1-Y2 direction.

  Specifically, the upper surface electrode 30 is formed of a silver-based thick film (silver-based metal glaze thick film), contains silver (Ag) and palladium (Pd), and has a total weight of silver and palladium. Palladium is contained in an amount of 15 to 30% (preferably 19 to 25%) by weight. That is, it can be said that the upper electrode 30 is a silver / palladium thick film (silver / palladium metal glaze thick film). Moreover, this upper surface electrode 30 is baked at 840-860 degreeC, and silver and palladium are fully alloyed by this.

  Further, as shown in FIG. 1, a pair of lower surface electrodes 40 are formed in both end regions in the longitudinal direction (X1-X2 direction (see FIG. 1)) of the lower surface of the insulating substrate 10, and are substantially rectangular in bottom view. It has a shape. The length of the lower surface electrode 40 (the length in the X1-X2 direction) is substantially the same as that of the upper surface electrode 30, but the length of the lower surface electrode 40 is arbitrary. Further, the width of the lower surface electrode 40 in the Y1-Y2 direction is formed substantially the same as the width of the insulating substrate 10 in the Y1-Y2 direction. The lower surface electrode 40 is formed of a silver-based thick film (silver-based metal glaze thick film).

  In addition, the side electrode 60 has a substantially cross-sectional shape so as to cover a part of the upper electrode 30, a part of the lower electrode 40, and the side surfaces of the insulating substrate 10 (that is, the X1 side surface and the X2 side surface). It is formed in a layer shape in a letter shape. The side electrodes 60 are provided at the end on the X1 side and the end on the X2 side, respectively.

  The side electrode 60 is a resin / silver-based thick film containing a resin and silver powder. Specifically, the side electrode paste is obtained by uniformly kneading a resin containing epoxy and phenol and silver powder. Is a thermosetting resin / silver-based thick film.

  Here, the ratio of the resin and silver in the entire side electrode 60 is 10 to 25% (preferably 14 to 16%) of resin and 75 to 90% (preferably 84) of silver powder in terms of weight ratio. In the volume ratio, the resin is 55 to 65% and the silver powder is 35 to 45%.

  Moreover, the ratio of epoxy to phenol in the whole resin is 30 to 36% (preferably 32 to 34%) of epoxy and 64 to 70% (preferably 66 to 68%) of phenol as weight ratio. It has become.

  The silver powder is composed of scaly powder (may be flaky powder) (scaly silver powder) (see FIG. 3) and spherical powder (spherical silver powder). The ratio of the scaly powder to the spherical powder in the entire silver powder is In terms of weight ratio, the scale powder is 30 to 40% (preferably 35%) and the spherical powder is 60 to 70% (preferably 65%). This scaly powder has a substantially thin plate shape, and the average diameter of its maximum width is 13 to 17 μm. As shown in FIG. 3, the maximum width here refers to the width U of the portion having the maximum width from one end portion to the other end portion in the scaly powder. The spherical powder has an average particle size of 0.5 μm or less (preferably 0.1 to 0.4 μm).

  Further, as shown in FIG. 1, the side electrode 60 has a substantially U-shaped cross section, and a part of the side electrode 60 is laminated on the upper surface of the upper surface electrode 30. The length of the portion (the length in the X1-X2 direction) T is formed to be 0.2 to 0.3 mm. That is, the protruding dimension of the side electrode 60 is 0.2 to 0.3 mm.

  The plating 70 includes a nickel plating (Ni plating) 72 and a tin plating 74, and is provided in an end region on the X1 side and an end region on the X2 side, respectively. That is, the plating 70 is provided on the surface of the electrode portion for connecting the chip resistor, the inner layer is the nickel plating 72, and the outer layer is the tin plating 74.

  Here, the nickel plating 72 is formed so as to cover a part of the upper surface electrode 30, the side surface electrode 60, and a part of the lower surface electrode 40. That is, it is formed so as to cover the exposed portions of the upper surface electrode 30, the side surface electrode 60, and the lower surface electrode 40. The nickel plating 72 is formed with a substantially uniform film thickness by electroplating. The nickel plating 72 is made of nickel and is formed to prevent solder erosion of internal electrodes such as the upper surface electrode 30. In addition to nickel, this nickel plating may use copper plating.

  Further, the tin plating 74 is disposed with a substantially uniform film thickness so as to cover the surface of the nickel plating 72. Note that solder plating may be used in addition to tin plating.

  As shown in FIG. 1, the resistor 80 is basically provided on the upper surface of the insulating substrate 10, and both end portions in the X1-X2 direction are connected to the upper surface of the upper electrode 30. . That is, the resistor 80 is formed in a strip shape in the longitudinal direction (inter-electrode direction or energization direction), and is formed in a substantially rectangular shape in plan view. The width of the resistor 80 in the Y1-Y2 direction is smaller than the width of the upper surface electrode 30 in the Y1-Y2 direction. The resistor 80 is formed of a ruthenium oxide-based metal glaze thick film.

  Further, the cover coat 90 is formed on the upper surface of the resistor 80 and is formed to alleviate the thermal shock during trimming of the resistor 80. The cover coat 90 is made of a glass-based material, specifically, a lead borosilicate glass thick film.

  Further, as shown in FIG. 1, the protective film 98 is mainly provided so as to cover the cover coat 90 and the resistor 80. That is, the formation position of the protective film 98 will be described in more detail. The protective film 98 is formed in the Y1-Y2 direction so as to be substantially the same as the width of the insulating substrate 10 (may be formed shorter than the width of the insulating substrate 10). Furthermore, in the X1-X2 direction, the resistor 80 and a part of the upper surface electrode 30 are provided so as to be covered. Thereby, the protective film 98 is formed so as to include the entire planar region of the resistor 80 in plan view.

  The protective film 98 is formed of an epoxy / phenolic resin, and the ratio of epoxy to phenol in the entire protective film 98 is 40 to 60% of epoxy and 40 to 60% of phenol by weight. Yes.

  The manufacturing method of the chip resistor 5 having the above configuration will be briefly described. First, a solid alumina substrate in which primary and secondary slits are formed on both the front and back surfaces (this alumina substrate has a plurality of chip resistors). And a bottom electrode is formed on the back surface (that is, the bottom surface) of the alumina substrate. That is, a paste for the lower surface electrode (for example, a silver-based paste such as silver-based metal glaze) is printed, dried and fired. In forming the lower surface electrode, the lower surface electrode is simultaneously formed for adjacent chip resistors. Furthermore, in the direction perpendicular to the inter-electrode direction, a bottom electrode is formed continuously in a strip shape.

  Next, an upper surface electrode is formed on the front surface (that is, the upper surface) of the alumina substrate. That is, the top electrode paste is printed, dried and fired. The upper surface electrode paste in this case was a silver palladium paste, and specifically, 15 to 30% (preferably 19 to 25%) palladium was contained in a weight ratio with respect to the total weight of silver and palladium. A top electrode paste is used. In addition, when it becomes a chip resistor, the upper surface electrode which adjoins mutually by the upper surface electrode of an adjacent chip resistor is formed in one printing area | region.

  Next, the resistor 80 is formed on the upper surface of the alumina substrate. That is, after the resistor paste of the resistor 80 is printed, it is dried and fired to form the resistor. The resistor paste is a ruthenium oxide paste (for example, ruthenium oxide metal glaze).

  Next, a lead borosilicate glass-based glass paste is printed and fired on the upper surface of the resistor 80 and the upper surface of the upper electrode to form a cover coat 90 and a cover coat 92. That is, the cover coat 90 and the cover coat 92 are formed simultaneously.

  Next, a trimming groove is formed in the resistor 80 to adjust the resistance value. That is, a trimming groove is formed in the resistor 80 by laser trimming.

  Next, a protective film is formed so as to cover at least the resistor 80 and the cover coat 90. That is, the resin paste is printed in a strip shape, dried and cured. Thereafter, primary division is performed along the primary slit.

  Next, the side electrode 60 is formed on the strip-shaped substrate. That is, the side electrode paste is printed, dried and cured. This side electrode paste is a side electrode paste obtained by uniformly kneading a resin containing epoxy and phenol and silver powder, and the ratio of resin to silver in the side electrode is expressed by weight ratio. 10 to 25% (preferably 14 to 16%), silver powder is 75 to 90% (preferably 84 to 86%), and the ratio of epoxy to phenol in the resin is weight ratio, 30 to 36% (preferably 32 to 34%), phenol is 64 to 70% (preferably 66 to 68%), and silver powder is scaly powder (may be flaky powder) And the ratio of the scaly powder to the spherical powder is 30 to 40% (preferably 35%) for the scaly powder and 60 to 70% (preferably 65%) for the spherical powder. %). Alternatively, the side electrode paste may be printed, dried, and fired.

  Thereafter, secondary division is performed along the secondary slit. Next, nickel plating is formed, and then tin plating is formed.

  The usage state of the chip resistor 5 will be described. The chip resistor 5 is used by being mounted on a wiring board (or a printed board). In mounting on the wiring board, the chip resistor 5 is mounted on the land 102 formed on the wiring board 100 via the solder fillet 110 as shown in FIG.

  In the chip resistor 5 of the present embodiment, even when the sulfide gas enters from the end portion in the longitudinal direction of the protective film 98, that is, the sulfide point that is the boundary position between the protective film 98 and the plating 70, Further, since 15 to 30% of palladium is contained in a weight ratio with respect to the total weight of silver and palladium, sulfidation of the upper surface electrode 30 can be prevented. That is, since 15 to 30% of palladium is contained in a weight ratio with respect to the total weight of silver and palladium, a palladium oxide concentrated layer is formed on the surface layer of the upper surface of the upper surface electrode 30, whereby silver sulfide is obtained. Stops at the surface layer of several tens of nm on the upper surface side, and this tens of nm is sufficiently smaller than 5 to 20 μm, which is the normal thickness of the thick film. The function of the vessel is not degraded.

  Moreover, by setting the ratio of palladium to 15 to 30% by weight with respect to the total weight of silver and palladium, there is a sufficient effect for preventing sulfidation of the upper surface electrode, and the palladium is contained more than necessary and the cost is more than necessary. It is not multiplied. Further, when the content ratio of palladium is increased, the resistance value of the upper surface electrode is increased, which is not suitable for a low-resistance chip resistor, but the palladium ratio is 15 to 30 by weight with respect to the total weight of silver and palladium. By setting it as%, it can also be suitable for a low-resistance chip resistor. Furthermore, since palladium is less expensive than gold (Au), the cost does not increase significantly.

  Since the sulfurized gas that has entered from between the protective film 98 and the plating 70 does not easily enter the upper surface electrode 30, particularly when the chip resistor 5 is used in an environment with a high concentration of sulfurized gas, Although it reaches the gap between 30 and the plating 70 and is in contact with the side electrode 60, since the side electrode 60 has the above-described configuration, sulfuration of the side electrode 60 can be prevented.

  That is, the side electrode 60 contains a large amount of silver powder of 75 to 90% (preferably 84 to 86%), and in particular, spherical powder that is a fine silver powder is 60 to 70% (preferably). Is contained in a thick film structure in which resin enters between silver powder and silver powder, so that the side electrode comes into contact with the sulfide gas and the silver powder is sulfided to insulate. Even if it becomes a thing, since most in silver powder is fine powder, the contact point (contact area) between silver powder is small, and progress of sulfidation becomes very slow. As a result, the entire side electrode 60 is not sulfided, and functions as a side electrode, that is, electrical connection between the upper surface electrode 30 and the solder fillet 110, mechanical connection in the chip resistor (particularly in the electrode portion 20). It does not affect the mechanical connection of each part.

  Further, since the spherical powder, which is a fine silver powder, is contained in a large amount of 60 to 70% (preferably 65%) in the silver powder, when the nickel plating 72 is formed by electroplating, a nickel plating pin is used. There is no generation of holes, and nickel plating can be formed uniformly. The nickel plating 72 serves as a protective layer against the sulfide gas, but by preventing the nickel plated pinholes from occurring, the side electrodes can be prevented from being sulfided.

  Further, since the spherical powder which is fine silver powder is contained in a large amount of 60 to 70% (preferably 65%) in the silver powder, the individual resistance value of the spherical powder becomes high, and the spherical powders Since the contact point (contact area) is small, the contact resistance value is also high, but since silver powder is contained in a large amount of 75 to 90% (preferably 84 to 86%) by weight, Since the number of contact points increases and a large number of conductive paths are formed, the resistance value of the entire side electrode can be lowered.

  Moreover, since the protruding dimension of the side electrode 60 is 0.2 to 0.3 mm, the disconnection between the side electrode 60 and the upper surface electrode 30 can be prevented.

  That is, when an extremely severe sulfur acceleration test was performed in which a chip resistor was immersed in oil containing high-concentration sulfur at a high temperature, the side electrode 60 was sometimes sulfided by 50 μm in the X1-X2 direction. . Further, the protruding dimension of the side electrode 60 is a function as a side electrode (electrical bonding of the upper surface electrode 30 and the solder fillet 110 and mechanical bonding in a chip resistor (particularly, mechanical bonding of each part in the electrode unit 20)). In order to achieve the above, it is usual to provide 0.1 mm, so that the protruding dimension of the side electrode 60 is set to 0.2 to 0.3 mm so that the function can be achieved even when 50 μm is sulfurized. The portion exceeding 0.15 μm is for improving the reliability, and the length not exceeding 0.3 mm is for suppressing the cost of the side electrode paste.

  In addition, by forming the protective film 98 from an epoxy / phenolic resin, the risk of sulfur gas entering and contacting the upper electrode 30 under the protective film 98 can be extremely reduced. In particular, the weight ratio of epoxy to phenol is 40 to 60% for epoxy and 40 to 60% for phenol, thereby improving the chemical resistance of the entire protective film and improving the sulfur resistance. be able to.

  In the above description, the side electrode 60 is described as being formed of a material containing resin and silver powder. However, the present invention is not limited to this, and the side electrode 60 is formed of a material containing resin and nickel powder. Also good. That is, the side electrode 60 may be a resin / nickel thick film. In other words, since nickel is not sulfided, the side electrode 60 can be made to be sulfide resistant by making the side electrode 60 a resin / nickel thick film. Examples of the resin in the resin / nickel-based thick film include a phenol resin and a resin containing epoxy and phenol.

It is sectional drawing which shows the structure of the chip resistor based on the Example of this invention, and is AA sectional drawing in FIG. It is a top view which shows the structure of the chip resistor based on the Example of this invention. It is a perspective view which shows the example of a scaly powder. It is sectional drawing which shows the use condition of the chip resistor based on the Example of this invention.

Explanation of symbols

5,105 Chip resistor 10 Insulating substrate 20 Electrode part 30 Upper surface electrode 40 Lower surface electrode 60 Side electrode 70 Plating 80 Resistor 90 Cover coat 98 Protective film

Claims (4)

A chip resistor,
An insulating substrate;
In a pair of electrode parts provided on an insulating substrate,
An upper surface electrode formed on both sides of the upper surface of the insulating substrate in the inter-electrode direction, the upper surface electrode containing 15-30% palladium by weight with respect to the total weight of silver and palladium contained in the upper surface electrode;
An electrode portion having at least a part of the upper surface of the upper surface electrode and a side surface electrode formed on a side surface of the insulating substrate, and a side surface electrode formed of a material having sulfuration resistance;
A resistor formed between a pair of upper surface electrodes;
A protective film covering a part of the upper surface electrode and the resistor;
A chip resistor comprising: The side electrode is formed of a resin / silver thick film, and the silver is composed of scaly silver powder and spherical silver powder. The scaly silver powder has an average maximum width of each scaly silver powder of 13 to 17 μm. 2. The chip resistor according to claim 1, wherein the average particle size is 0.5 μm or less, and the ratio of the spherical silver powder to the whole silver is 60 to 70% by weight. 3. The chip resistor according to claim 1, wherein a length in a direction between the electrodes in a region where the side electrode overlaps with the top electrode is 0.2 to 0.3 mm. 4. The chip resistor according to claim 1, wherein the protective film is formed of a resin containing epoxy and phenol, and the ratio of phenol to the entire protective film is 40 to 60% by weight. vessel.

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