JP2004023006A - Chip resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip resistor of higher stability in mounting when mounting the tip resistor on a circuit board. <P>SOLUTION: The chip resistor comprises plated electrodes 23 and 23 at both ends of an insulating substrate 11, and a width c of the resistor body is 70% or larger the width d of the insulating substrate. A resistor 15 is so disposed as to extends to the end surface or its vicinity in the length direction of the insulating substrate 11. On the end surface in the length direction of the insulating substrate, an end surface electrode 21 is provided which straddle it in an U-shape, between an electrode 13 on the surface side of the substrate and an electrode 19 on the rear surface side and is formed by dipping. The plated electrode 23, disposed at both ends of the insulating substrate, is equal in height or larger than that of a protective film 17. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a chip resistor having improved mounting stability, and particularly to a so-called bulk mounting in which a chip is mounted on a circuit board without selecting front and back of the chip component from a bulk cassette containing a large number of chip components. Which relates to a chip resistor.
[0002]
[Prior art]
Recently, square chip resistors have become widespread. 2. Description of the Related Art With the progress of electronic devices to be mounted and mounted, it is required to support small and high-density mounting. For this reason, the size of the chip resistor is currently 1005 type (1.0 mm × 0.5 mm), but the shift to the smaller 0603 type (0.6 mm × 0.3 mm) has begun. It is getting. On the other hand, there is a demand for a chip resistor suitable for bulk mounting to be mounted on a circuit board without selecting front and back of the chip component from a bulk cassette containing a large number of chip components.
[0003]
FIG. 6 shows a structure example of a conventional thick film chip resistor. The conventional chip resistor has thick film electrodes 13 at both ends of an insulating substrate 11 made of alumina or the like, and a thick film resistor 15 is arranged between the electrodes. The resistor 15 is covered and protected by a protective film 17 made of a glass insulating film and a resin insulating film. Plating electrodes 23 are formed on the electrode 13 on the front surface and the electrode 19 on the back surface, which are both ends of the insulating substrate 11, and the end surface electrode 16 on the side end surface.
[0004]
In this case, the surface of the protective film 17 may be rounded and, when fixed to a circuit board by a mounting machine (mounter), may be attracted to the collet of the mounting machine while being obliquely inclined. In such a case, misalignment or the like occurs when the semiconductor device is mounted on a circuit board, and mounting stability is impaired. This tendency becomes particularly remarkable as the chip resistor is reduced in size to, for example, a 1005 type (1.0 mm × 0.5 mm) or a 0603 type (0.6 mm × 0.3 mm).
[0005]
Also, as a mounting method, there is a so-called bulk mounting method in which a large number of chip components are stored in a bulk cassette in a random state, and the chip components are taken out of the bulk cassette one by one and mounted on a circuit board. According to such a mounting method, when mounting the chip component on the circuit board, the surface mounting of the chip component is performed without selecting the front and back of the chip component.
[0006]
By the way, when the conventional chip resistor shown in FIG. 6 is bulk-mounted by a bulk mounting machine, the chip resistor may be mounted face down so that the front side (protective film side) faces the circuit board. appear. At this time, in the conventional structure, the surface of the protective film 17 at the center of the substrate is generally higher than the surface of the plating electrode 23. For this reason, there is a possibility that the chip resistor is mounted at an angle, and in the worst case, there is a problem that one side cannot be soldered or a phenomenon such as chip standing occurs. Therefore, the conventional chip resistor has a disadvantage that it cannot cope with so-called bulk mounting.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and has as its object to provide a chip resistor capable of improving the mounting stability when mounting the chip resistor on a circuit board.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a chip resistor according to the present invention includes an insulating substrate, a resistor formed on a surface of the insulating substrate, and covering the resistor on both ends of the resistor. A pair of electrodes, a protective film covering a resistor exposed between the electrodes, and a chip resistor including plated electrodes at both ends of the insulating substrate, wherein the width of the resistor is The width of the insulating substrate is about 70% or more.
[0009]
Further, the resistor is disposed so as to extend to an end face in a longitudinal direction of the insulating substrate or to a vicinity thereof.
In addition, an end face electrode formed by dipping in a U-shape on the electrode on the front side and the electrode on the back side of the substrate is provided on a longitudinal end face of the insulating substrate. Since the electrode formed by dipping is also formed on the surface electrode, it is easy to arbitrarily adjust the surface height of the plating electrode formed thereon. Accordingly, it is possible to easily make the height of the plating electrodes arranged at both ends of the insulating substrate substantially equal to or higher than the height of the protective film. Therefore, it is possible to easily cope with the bulk mounting method.
[0010]
According to the present invention, as described above, the shape of the resistor is made to occupy about 70% or more of the width of the insulating substrate, and is extended to the end face in the longitudinal direction of the insulating substrate or to the vicinity thereof. Was arranged. This makes it possible to secure a wider flat portion on the protective film surface of the chip resistor. Therefore, when the chip resistor is surface-mounted, the chip resistor can be easily and reliably sucked by the suction portion of the mounting machine, and the mounting stability can be improved even in a very small chip resistor. it can. Further, since the resistor is disposed so as to extend to or near the longitudinal end face of the insulating substrate, the flatness of the plating electrode surface can be improved, and the chip resistor is securely mounted on the circuit board. It becomes possible.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 shows an overall configuration of a chip resistor according to an embodiment of the present invention, and FIG. 2 shows an arrangement of resistors on a substrate surface.
[0012]
A resistor 15 is formed on the surface of an insulating substrate 11 made of alumina or the like of the chip resistor. The resistor 15 is formed by baking after forming a pattern by screen printing of a thick film paste such as ruthenium oxide, and a pair of surface electrodes 13 are formed so as to cover both end portions of the resistor 15. The surface electrode 13 is formed by baking after forming a pattern by screen printing of a thick film paste such as silver or palladium. On the back side of the insulating substrate 11, a pair of back electrodes 19, 19 are formed. The back electrodes 19, 19 are also formed by baking after pattern formation by screen printing of a thick film paste such as silver or palladium, like the front electrodes. End electrodes 21 and 21 are formed in a U-shape on both end surfaces of the insulating substrate 11 so as to extend over the front electrode 13 and the back electrode 19. Then, a plating electrode 23 is formed on the end face electrode 21 and on a part of the back face electrode 19 that does not straddle the end face electrode.
[0013]
The resistor 15 is covered and protected by a two-layer protective film 17 composed of a glass insulating film 17a and a resin insulating film 17b. On both sides of the protective film 17 composed of the glass insulating film 17a and the resin insulating film 17b, a pair of plated electrodes 23 are disposed on the front surface electrode 13, the back surface electrode 19, and the end surface electrode 21.
[0014]
That is, by dipping a paste of silver (Ag) or the like on the side end surface of the insulating substrate 11, a part of the electrode 13 on the front surface side and the electrode 19 on the back surface are covered in a U-shape to form an end electrode. 21 is formed, and a plating electrode 23 formed by plating is adhered. The plating electrode 23 is composed of a nickel plating layer and a solder or tin plating layer.
[0015]
This chip resistor is characterized in that the width c of the resistor is relatively larger than the width d of the insulating substrate. FIG. 2 shows the appearance of the surface of the insulating substrate 11 having a width of dmm on which the resistor 15 having a width of cmm is formed. The distance from the side end of the resistor 15 to the side end of the insulating substrate 11 is amm. The end of the resistor 15 extends to the longitudinal end surface of the insulating substrate 11 or its vicinity (distance bmm). In a chip resistor of 1005 size (1.0 mm × 0.5 mm), the width d of the substrate is 0.5 mm, the distance a is 0.05 mm or more, and the resistor width c is 0.35-0. 4 mm is appropriate. That is, in the 1005 type chip resistor, which is an extremely small chip resistor, the width c of the resistor is relatively wider than the width d of the insulating substrate, and occupies about 70 to 80% of the width d.
[0016]
In a 0603 type (0.6 mm × 0.3 mm) chip resistor, the width d of the substrate is 0.3 mm, the distance a is about 0.04 mm, and the width c of the resistor is 0.22 mm. Appropriate. That is, the width c of the resistor is relatively wider than the width d of the insulative substrate, and also accounts for about 70 to 80% of the width d. Further, the resistor 15 may be extended to the end face in the longitudinal direction of the insulating substrate 11 or may be arranged to be separated from the end face by a small distance b (about 0.04 mm).
[0017]
3A and 3B are diagrams showing a conventional chip resistor and a chip resistor of the present invention in comparison with each other. FIG. 3A is a cross-sectional view of a central portion of a conventional chip resistor, and FIG. 3 shows a cross section near the end face along the longitudinal direction. (C) shows a cross section at the center of the substrate of the chip resistor of the present invention, and (d) shows a cross section near the end face along the longitudinal direction of the substrate. In the chip resistor of the present invention, since the width of the resistor 15 is wider than the width of the insulating substrate 11, a wide flat surface 17y is obtained on the surface of the protective film 17 as shown in FIG. Therefore, when mounting the chip resistor, the roundness 17x on the surface of the protective film that existed in the conventional chip resistor does not exist, and even when using a collet, it is possible to perform stable suction even with a very small chip resistor. Stability can be improved.
[0018]
Further, since the resistor 15 extends to or near the end face of the insulating substrate 11, a protruding portion 23x of the plating electrode which occurs in the overlapping portion between the resistor 15 and the electrode 13 as shown in FIG. Instead, a wide flat surface 23y is obtained on the surface of the plating electrode on the surface electrode 13 as shown in FIG. Note that a similar flat surface 23y is similarly formed on the back surface electrode 19 on the back surface side of the substrate. Thereby, when mounting the chip resistor on the circuit board, the mounting stability can be improved. Further, as shown in FIG. 3C, since the width of the resistor 15 is wide, the surface of the plating electrode on the surface electrode 13 can be made flat. If a resistor having a narrow width as shown in FIG. 3A is formed as a lower layer of the surface electrode, the surface of the electrode becomes rounded and the mountability decreases.
[0019]
In the chip resistor having the above-described structure, the plated electrode 23 having a height equal to or higher than the surface of the protective film 17 of the chip resistor is formed. The inclination of the resistor can be suppressed, so that the resistor is securely mounted on the circuit board. For this reason, it is possible to cope with so-called bulk mounting, in which chip resistors are supplied from a bulk cassette by a bulk mounting machine without selectivity of front and back surfaces to perform surface mounting.
[0020]
Next, a method for manufacturing a chip resistor according to the present invention will be described with reference to FIG. 4 (cross-sectional view) and FIG. 5 (plan view).
First, as shown in (a), an insulating substrate 11 of alumina or the like is prepared. Although the illustrated example shows two to three chip regions, a multi-chip substrate for manufacturing a large number of chip resistors at once is used.
[0021]
Next, as shown in (b), on the surface of the insulating substrate 11, a resistor 15 wider than the substrate width is formed by firing after pattern formation by screen printing of a thick film paste such as ruthenium oxide. I do. In this embodiment, the resistors 15 are formed continuously with respect to adjacent sections so as to extend to the end surface of the insulating substrate when each chip resistor is formed. However, they may be divided and arranged so as to leave a small distance from the end face of the substrate.
[0022]
Next, as shown in (c), a pair of electrodes 13 is formed on both sides of the resistor 15 on the surface of the insulating substrate 11. Also, a pair of back electrodes 19, 19 are formed at both ends of the back surface. These electrodes 13 and 19 are formed by forming an Ag or Ag-Pd paste pattern by screen printing, and firing at a temperature of, for example, about 850 ° C. Either of the front-side electrode 13 and the back-side electrode 19 may be formed first, or they may be fired at the same time.
[0023]
Next, as shown in (d), a glass insulating film 17a for protecting the resistor is formed on the resistor 15. If necessary, laser trimming is performed to form cuts 18 to adjust the resistance value to a desired value.
[0024]
Next, as shown in (e), a second protective layer pattern of a resin paste is formed on the glass insulating layer 17a by screen printing and is heated and cured to form a second protective layer 17b. The second protective layer 17b is formed by heating and curing a resin paste at a temperature of, for example, about 200 ° C. The first protective layer 17a and the second protective layer 17b are formed so as to partially overlap the pair of front electrodes 13 and cover the resistor 15 therebetween. As described above, since the width of the resistor is relatively larger than the width of the insulating substrate, a flat surface 17y (see FIG. 3C) is obtained on the surface of the protective film formed thereon.
[0025]
The above process is a batch process of a multi-piece substrate, and then a process of dividing into strips is performed. The processing may be dicing or break. As shown in (f), the multi-piece substrate is divided into strips. Thereafter, as shown in (g), the exposed end face on the substrate side is dipped in silver (Ag) paste or the like to form end face electrodes 21 and 21. The end surface electrodes 21 and 21 may be formed by dipping in a conductive resin. The end electrodes 21 and 21 are formed much thicker than, for example, a thin-film conductive layer of Ni / Cr deposited by sputtering. The end surface electrodes 21 and 21 are formed thickly so as to straddle the U-shaped surface electrode 13 on the front surface side of the substrate and the back surface electrode 19 on the back surface side. Therefore, by adjusting the thickness, the final surface height of the plated electrode can be arbitrarily adjusted.
[0026]
Next, as shown in (h), a process of dividing into single chips is performed. Processing may be dicing or break. Next, as shown in (i), plating is performed on the electrodes 19 and 21 by electrolytic plating. In order to prevent electrode cracking and improve the reliability of soldering, a plating electrode 23 composed of a Ni plating layer and a Sn—Pb plating layer (or a Sn plating layer) is formed by electrolytic plating.
[0027]
According to the above-described manufacturing process, the surfaces of the electrodes 23 at both ends of the insulating substrate 11 are raised by the thick end surface electrodes 21 wrapping around the surface side, and the surface electrodes 13, 13 are formed on the resistor 15. Since the structure is adopted, the swelling 23x (see FIG. 3B) due to the overlap of the electrode layers can be avoided, and the plating electrodes 23, 23 are higher than the central protective film 17 and the flatness is improved. According to such a method for manufacturing a chip resistor, a normal method for manufacturing a chip resistor can be used as it is, except that a dipping step is used for an end face electrode. Therefore, it is possible to manufacture a chip resistor compatible with bulk mounting while suppressing an increase in manufacturing cost and improving mounting stability.
[0028]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention may be embodied in various forms within the scope of the technical idea.
[0029]
【The invention's effect】
As described above, according to the present invention, a wide resistor is formed on a surface of an insulating substrate so as to extend to or near an end face in a longitudinal direction, and a surface electrode is formed on the resistor. An end face is dipped in a conductive resin to form a thick end face electrode in a U shape on the front face electrode and the back face electrode, and a plating electrode is formed thereon. The chip resistor of the present invention is a chip resistor having a plating electrode which is equal to or higher than the surface of the protective film, and which has a wide flat portion on the protective film surface and the electrode surface. In this case, mounting on a circuit board is ensured. Further, it is possible to provide a chip resistor suitable for bulk mounting having no selectivity between front and back during mounting.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an overall configuration of a chip resistor according to an embodiment of the present invention.
FIG. 2 is a top view of an insulating substrate of the chip resistor.
3A and 3B are diagrams showing a conventional chip resistor and a chip resistor of the present invention in comparison with each other. FIG. 3A is a cross-sectional view of a central portion of a conventional chip resistor, and FIG. FIG. 3C shows a cross section near the end face along the longitudinal direction, FIG. 4C shows a cross section at the center of the substrate of the chip resistor of the present invention, and FIG.
FIG. 4 is a cross-sectional view of each step for explaining a method of manufacturing a chip resistor of the present invention.
FIG. 5 is a plan view of each step for explaining a method for manufacturing a chip resistor of the present invention.
FIG. 6 is a cross-sectional view showing the overall configuration of a conventional chip resistor.
[Explanation of symbols]
Reference Signs List 11 Insulating substrate 13, 19, 21 Electrode 15 Resistor 17a, 17b, 17 Protective film 17x Rounded protective film 17y Protective film 18 having flatness Trimming groove 21 Conductive resin electrode 23 Plating electrode 23x Electrode 23y having flatness

Claims (4)

An insulating substrate, a resistor formed on the surface of the insulating substrate, a pair of electrodes formed at both ends of the resistor so as to cover the resistor, and a resistor exposed between the electrodes A protective film for covering, a chip resistor provided with plated electrodes at both ends of the insulating substrate,
A chip resistor, wherein the width of the resistor is about 70% or more of the width of the insulating substrate. 2. The chip resistor according to claim 1, wherein the resistor is disposed so as to extend to an end face of the insulating substrate in a longitudinal direction or a vicinity thereof. 2. An end face electrode formed by dipping over a U-shaped electrode on an electrode on the front side and an electrode on the back side of the substrate on a longitudinal end face of the insulating substrate. Chip resistors. 2. The chip resistor according to claim 1, wherein the height of the plating electrodes arranged at both ends of the insulating substrate is substantially the same as or higher than the height of the protective film.

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