JP2002305117A - Laminated inductor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated inductor and its manufacturing method, where a method for spreading conductor paste on both end portions of a chip by dipping is not used, so that bulge due to the conductor paste is not generated, bonding strength in the case of mounting is sufficient, design assuming the bulge of a terminal electrode is made unnecessary for designing, and flexibility of design is high. SOLUTION: The laminated inductor of an almost rectangular parallelopiped type is provided where an inductor is formed in a laminate 1. Terminal electrodes 21 are arranged in both the end surface portions in the lamination direction of the laminated. In periphery 4 surfaces in the vicinity of the end surface portions, recessed creep-in electrodes 22 are arranged in the parts except corners. By forming the recessed detour electrodes 22 continuous to the terminal electrodes 21, the amount of solder staying in the recessed detour electrodes in the case of mounting to a printed board or the like can be increased, as compared with a structure article which has no recess, so that bonding strength is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated inductor formed by laminating a conductor and an insulator (including a dielectric) or a resistor made of a magnetic or non-magnetic material to form an inductor, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art A conventional laminated inductor is shown in FIG.
As shown in the layer structure diagram of FIG. 1, through holes 13 are formed in a multi-piece green sheet 11a to 11l (shown for one chip in the drawing) made of a magnetic material or a non-magnetic material.
a to 13l and each green sheet 11a to
11l has lead electrodes 14a to 14a to connect an internal conductor to a terminal electrode 20 (see FIG. 8B) to be attached later.
14d or the coil conductors 12a to 12h are formed, these green sheets 11a to 11l are laminated, cut, divided into individual chips and fired.
As shown in (1), the terminal electrode 20 is applied to both ends of each chip in the stacking direction by dipping or the like with a conductive paste and then fired, and the terminal electrode 20 of the fired chip is electroplated to form a multilayer inductor. ing.

FIG. 9A shows another example of a conventional laminated inductor, in which terminal electrodes 25 are formed only on both end surfaces of a chip 11 and the conditions for applying a conductive paste are set so as not to wrap around the side surfaces. It is set.

FIG. 10 (A) is Japanese Patent Application Laid-Open No. 2000-17385.
FIG. 10 (B) is a perspective view of the layered structure of the multilayer inductor disclosed in Japanese Patent Publication No. 7-1995, in which not only the terminal electrode 25 is formed on the end face side green sheet 11a, but also the green sheets 11a to 11n in the vicinity thereof. The conductor 26 is filled in the side through holes also on the four surfaces 11c to form a soldering surface.

[0005]

In the multilayer inductor shown in FIGS. 8A and 8B, a method for forming terminal electrodes 20 by dip or the like with a conductive paste at both ends of the chip is performed. It is necessary to mechanically chuck the chip, for example, a 0603 shape (length: 0.6
(mm, width and thickness: 0.3 mm), when it comes to chips with minute dimensions such as mechanical chucking, precision equipment is required, or even if such equipment is available, There is a possibility that stable chucking cannot be performed and a problem of dip diagonally occurs.

[0006] In the case of the above-mentioned 0603 shape, the swelling of the terminal electrode due to the conductive paste applied by dip or the like causes a problem that the seating is poor when mounted on a printed circuit board, and shifting and chip standing are likely to occur. .

Further, in the design, the element body 11 is made smaller in consideration of the swelling of the terminal electrode 20,
It is necessary to adjust the overall dimensions, which causes a problem that the inductance cannot be increased.
In the case of a small chip having three shapes, the degree of freedom in design is reduced.

Further, in the multilayer inductor shown in FIG. 9A, as shown in FIG.
0, the pad 41 on the printed circuit board 40 may not be bonded to the lower side of the chip 11 and the pad 41 in some cases. In this case, the solder 42 fills the terminal electrode 25 with a fillet. It is not possible to form them, and there is a high possibility that defective bonding portions 45 will occur. Even if fillets can be formed, there is no bonding between the lower side of the chip 11 and the pads 41, so that the lateral pressing strength is significantly reduced. There is a problem that.

Also, as shown in FIGS. 10A and 10B, the wraparound electrodes 26 formed on the four surfaces near the terminal electrode 25 are provided with a dip at both ends shown in FIG. 8B. As a result, it was confirmed that the mounting strength was lower than that provided with the terminal electrode 20.

In view of the above problems, the present invention does not employ a method of applying a conductive paste to both ends of a chip by dipping, so that there is no swelling due to the conductive paste, the bonding strength in mounting is sufficient, and the design is satisfactory. An object of the present invention is to provide a multilayer inductor having a high degree of design freedom and a method of manufacturing the multilayer inductor, which eliminates the need for design in consideration of the swelling of the terminal electrodes.

[0011]

According to a first aspect of the present invention, there is provided a multilayer inductor having a substantially rectangular parallelepiped shape in which an inductor is formed inside a multilayer body, and terminals are provided at both end surfaces in the stacking direction of the multilayer body. In addition to having the electrodes, the semiconductor device is characterized in that it has a recessed wraparound electrode portion that is continuous with the terminal electrode in a portion excluding a corner portion on four peripheral surfaces near the both end surface portions.

As described above, by forming the wraparound electrode portions depressed at the end portions of the laminate in the stacking direction except for the corner portions of the four peripheral surfaces around the both end portions, the recesses are formed during mounting on a printed circuit board or the like. Since the amount of solder accumulated in the wraparound electrode part can be increased compared to a non-dented structure product, a conductor paste is applied by dip to both ends of the chip and baked and is equal to or greater than the conventional terminal electrode The bonding strength with the printed circuit board can be obtained, and the solder easily accumulates in the recessed wraparound electrode portion, thereby improving the solderability. Also, only one firing step is required, which leads to cost reduction.

In addition, there is no swelling of the terminal electrode when the conductor paste is attached later as in the conventional product, and the stoppage of the work (operation stop due to trouble) is remarkably improved.
Good mounting on a printed circuit board without shifting or chip standing can be performed. Further, since there is no swelling of the terminal electrodes, the chip size can be secured at a predetermined size, and the degree of design freedom is increased.

According to a second aspect of the present invention, there is provided a multilayer inductor.
Wherein the depth of the depression of the wraparound electrode portion is 14 μm or more.

As described above, by setting the recess of the wraparound electrode portion of each of the four sides around the both end surfaces of the laminated body excluding the corner portions to 14 μm or more, the solder recessed portion can be formed on a printed circuit board or the like. It ’s easy to accumulate,
Dip is applied to the both ends of the chip to apply a conductive paste and baked to form terminal electrodes. At the same time, the same bonding strength as that of the conventional product is obtained. And the solderability is good. In addition, if the dent of the wraparound electrode portion is formed by the difference in shrinkage between the conductive paste and the green sheet, it is practical to be 40 μm or less in consideration of the maximum possible difference in shrinkage. is there.

According to a third aspect of the present invention, there is provided a method of manufacturing a multilayer inductor, comprising: forming a plurality of green sheets for forming a plurality of green sheets having through holes filled with a conductive paste for forming inductor coil conductors and connecting the coil conductors; And at least one green sheet on the terminal electrode side having a through hole filled with a conductive paste for connecting the terminal electrode on the end face and the coil conductor, the green sheet being on both sides of the green sheet, At least a part of the electrode-side green sheet is formed with a through-hole for forming a side through-hole filled with a conductive paste, between adjacent inductor forming regions, and at least a side through-hole is formed in advance from the shrinkage ratio of the green sheet. The shrinking ratio of the conductor paste in the hole is set to be large, and the coil conductor is formed. The green sheet and the terminal electrode side green sheet on both sides thereof are overlapped, the terminal electrode paste is overlapped on the end face, the overlapped green sheet is pressed, and the through hole for forming the side through hole is cut at the center. After the individual chips are formed, baking is performed. At the time of baking the chips, the terminal electrode on the end face is formed in a portion excluding the four corners near the end face due to the difference in shrinkage ratio between the conductive paste and the green sheet. And forming a continuous wraparound electrode portion that is continuous with the above.

As described above, the through holes for the side through holes are formed at both end surfaces of the chip or in the vicinity thereof.
By filling the through-hole with the conductive paste, setting the shrinkage of the conductive paste to be greater than the shrinkage of the green sheet, and cutting and firing, the portion of the conductive paste in the side through-hole is a concave portion of the green sheet. A reduced and recessed wraparound electrode portion is formed. As described above, if the recessed wraparound electrode portion is formed by changing the shrinkage ratio of the green sheet and the conductive paste, the recessed wraparound electrode portion can be formed using a conventional sheet laminating method.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a multilayer inductor according to the third aspect, wherein
The conductor paste for forming the terminal electrode and the wraparound electrode portion has a silver content of 77.5 to 89.0% by weight, a glass content of 3.5 to 5.2% by weight, the balance being a vehicle, and a silver powder. Are characterized by having an average particle size of 0.5 to 0.8 µm and a glass softening point temperature of 790 to 830 ° C.

By adopting such a manufacturing method, it is possible to obtain both ends in the laminating direction of the laminated body and the periphery 4 near the both end surfaces.
It is possible to easily form a terminal electrode having a wraparound electrode portion depressed in a portion other than a corner portion of the surface, and a multilayer inductor having the effect of claim 1 can be obtained.

According to a fifth aspect of the invention, there is provided a method of manufacturing a multilayer inductor according to the third or fourth aspect, wherein the through hole for forming the side through hole is oval.

As described above, by making the shape of the through hole for the side through hole for forming the wraparound electrode portion on the four surrounding surfaces into an oblong shape as shown in FIG.
The width dimension α of the wraparound electrode portion shown in FIG. 1A can be kept constant with respect to the cutting displacement that always occurs when cutting into individual chips. For example, when the through-hole is not an ellipse but a perfect circle, the width deviation α of the wraparound electrode portion varies in size due to the cutting deviation that always occurs, resulting in unstable bonding strength and Is impossible to satisfy.

[0022]

FIG. 1A is a perspective view showing one embodiment of a multilayer inductor according to the present invention. This inductor has a substantially rectangular parallelepiped shape in which an inductor is formed inside the multilayer body 1, has terminal electrodes 21 on both end surfaces in the stacking direction of the multilayer body 1, and has corners on four peripheral surfaces near the both end surfaces. A portion other than the portion has a wraparound electrode portion 22 that is concave and continuous with the terminal electrode 21.

FIG. 2 is a layer configuration diagram of one of the laminated inductors. 1a to 1m are ceramic green sheets containing a magnetic or non-magnetic powder. 2a ~
Reference numeral 2h denotes a coil conductor formed by printing a conductor paste on the green sheets 1d to 1k. Each green sheet 1d to 1k has a through hole filled with a conductor for connecting the coil conductors and conductors 22a to 22c described later. 3d to 3k are provided.

Terminal electrodes 21a are printed on the green sheet 1a, and conductors 22a, 22b, 22 are formed on the green sheets 1b, 11l, and 1m except for portions other than corner portions.
c is printed. These green sheets 1a, 1b,
The coil conductors 2a to 2h are connected to the terminal electrodes 21 and 1m, respectively.
Through holes 3a, 3b, 31, and 3m filled with conductors for connection to the a and 21b are provided. A conductor 4 for connecting to the terminal electrode 21a is provided on the green sheet 1c.
And a through hole 3c filled with a conductor. The lowermost base film 18 is obtained by solid-coating the terminal electrode 21b to transfer the one terminal electrode 21b, and is peeled off after lamination.

FIG. 3 shows the green sheet 1a shown in FIG.
1b, a pattern diagram showing the shapes of side through holes 33 provided in 1l, 1m, central through holes 3a, 3b, 31, 3m, and conductors 22a to 22c filling the side through holes 33 and through holes 3b, 31, 3, 3m. It is.

FIG. 4 is a view showing a laminated structure of green sheets for taking a large number of pieces in actual production.
FIG. 3 is a view showing a state in which these green sheets are stacked.

FIG. 6 shows through holes 33A for forming side through holes 33 provided in the green sheets 1a, 1b, 11 and 1m in a state where the green sheets 1a to 1m and the terminal electrodes 21 are laminated.
FIG. 6 is a diagram showing a relationship between conductors 22a to 22c to be filled in a chip and a cutting width W for obtaining individual chips. In the present embodiment, as shown in FIG.
The through hole 33A for 3 is formed in an oval shape.

The green sheets 1a to 1m and the terminal electrodes 21b are laminated, crimped, and cut vertically and horizontally.
5 and 36 are cut and baked, but the green sheets 1 a to 1
The shrinkage of the conductive paste using silver or its alloy powder is set to be larger than the shrinkage of m. As a result, when the chip is cut into individual chips and fired, the conductive paste shrinks more than the green sheet, so that the wraparound electrode portion 22 that is concave as described above can be formed. The wraparound electrode portion 22 includes paste-like conductors 21a, 21b, 22a to 2a.
2c is formed by the portion filled in the side through hole 33.

It is preferable that the shrinkage ratio of the conductive paste is at least 4% larger than that of the green sheet. More specifically, when the shrinkage of the green sheet is 16%, the shrinkage of the conductive paste is 20% or more. As the green sheet, it is preferable to use alumina, cordierite, umlite, low-dielectric-constant glass or the like having a relative dielectric constant of 30 or less for high frequency use in order to reduce the distributed capacitance. In the embodiment, glass consisting of strontium, calcium, alumina and silicon oxide 70 wt.
%, And a ceramic green sheet made of a ceramic composition having a composition of 30% by weight of alumina.

The composition of the conductor paste is silver 77.5.
８９89.0 wt%, glass 3.5 to 5.2 wt%, and the remainder was a vehicle. Further, the average particle size of the silver powder is 0.5 to 0.8 μm.
m, and the glass softening point temperature was 790 to 830 ° C. Preferably, the silver content was 78.0 to 83.0 wt%, the glass was 3.5 to 4.4 wt%, and the balance was vehicle and the average of silver powder was The particle size is 0.55 to 0.75 µm, and the glass softening point is 790 to 810 ° C.

The coil conductors 2a to 2h are printed so that the pattern width is 35 μm and the thickness is 10 μm.
Silver paste was used as the conductor paste.

The width α of the wraparound electrode portion 22 (FIG. 1)
(See (A)) is 0.1 mm, and the chip is fired and electroplated to form 0603 (length: 0.6 m).
m, width and thickness: 0.3 mm). The electroplating of the terminal electrode 21 is completed by performing copper and nickel and tin, nickel and tin, nickel and gold, nickel and palladium and gold, nickel and palladium and silver, or nickel and silver.

By forming the through-hole 33A in an elliptical shape as described above, the width α of the wraparound electrode portion 22 shown in FIG. it can.

In FIG. 1A, the dimension β in the longitudinal direction from the end face of the wraparound electrode portion 22 depends on the thickness of the green sheet forming the wraparound electrode portion 22. By setting the thickness, the dimension β can be arbitrarily set. In the embodiment, the wraparound electrode portion 22 is formed by two green sheets, but may be formed by one or three or more sheets depending on the chip size and the thickness of the green sheet.

FIG. 1B is a perspective view showing a state in which the laminated inductor is soldered to a printed board, and FIG. 1C is a sectional view taken along the line EE of FIG. When the wraparound electrode portion 22 is soldered with the solder 42, the recessed portion is filled with the solder 42, and compared with the conventional example of FIG. 1D (the example of FIG. 10),
The joining strength increases.

FIG. 7 shows the results of comparison of the lateral pressing strength of the inductor having the nominal value of 2.7 nH according to the conventional example and the terminal electrode shape in the present invention. In FIG. 7, conventional example 1
As shown in FIG. 8B, a terminal electrode 20 is provided by attaching a conductor paste to both ends of a chip by dip or the like. In the first embodiment, the wraparound electrode portion 22 is formed in a recess of 14 μm in a portion excluding the corners of the four side surfaces shown in FIG. 1, and in the second embodiment, the electrode portion 22 is formed in a recess of 36 μm. In Conventional Example 2, as shown in FIG. 10, wraparound electrode portions without depressions are formed on four surfaces near the terminal electrodes. In Conventional Example 3, as shown in FIG. 9, a conductor paste is attached only to both end portions by dipping or the like.

As is clear from FIG. 7, according to the first and second embodiments, the same joining strength as that of the first conventional example in which both end portions and the vicinity thereof are dipped can be obtained. High bonding strength can be obtained.

[0038]

According to the first aspect of the present invention, since the recessed wraparound electrode portion is formed on the part except for the corner portions of the four peripheral surfaces of both end surfaces in the stacking direction and the both end surfaces in the stacking direction, it is mounted on a printed circuit board or the like. Occasionally, the amount of solder accumulated in the recessed wraparound electrode portion can be larger than that of a structure product without a recess, so that it is equivalent to a conventional terminal electrode in which a conductor paste is applied by dipping to both ends of the chip and baked Alternatively, a higher bonding strength with the printed circuit board can be obtained. In addition, solder easily accumulates in the recessed wraparound electrode portion, so that there is no shifting or chip standing, and mounting with good solderability is possible. Only one firing process is required, which leads to cost reduction.

Since there is no swelling of the terminal electrodes, a predetermined chip size can be ensured, and the degree of design freedom is increased.

According to the second aspect of the present invention, the recess of the wraparound electrode portion except for the corners on the four peripheral surfaces at both end surfaces of the laminated body is set to 14 μm or more, so that the solder can be recessed in mounting on a printed circuit board or the like. Dip is applied to both ends of the chip and conductive paste is applied and baked to obtain the same bonding strength as that obtained by forming the terminal electrodes. The tension easily attaches to the terminal portion, and the solderability is improved.

According to the third aspect, by forming the recessed wraparound electrode portion by changing the shrinkage ratio of the green sheet and the conductive paste, the recessed wraparound electrode portion is formed by using the conventional sheet laminating method. be able to.

According to the fourth aspect, the conductive paste for forming the wraparound electrode portion has a silver content of 77.5 to 8%.
9.0 wt%, the glass content is 3.5 to 5.2 wt%, the remainder is vehicle, and the average particle size of the silver powder is 0.5 to 0.5.
Since the glass softening point temperature is 790 to 830 ° C., a terminal electrode having a wraparound electrode portion depressed at a portion excluding a corner portion among both end surfaces in the laminating direction and four peripheral surfaces near both end surfaces in the lamination direction. Can be easily formed, and a multilayer inductor having the effect of claim 1 can be obtained.

According to the fifth aspect, the shape of the through hole for the side through hole for forming the wraparound electrode portion on the four surrounding surfaces is made oval, so that the cutting deviation always occurs when the chip is cut into individual chips. On the other hand, the width of the wraparound electrode portion can be kept constant, and as a result, the bonding strength is stabilized.

[Brief description of the drawings]

FIG. 1A is a perspective view showing an embodiment of a multilayer inductor according to the present invention, FIG. 1B is a perspective view showing a state of soldering to a printed circuit board, and FIG. -E is a sectional view, and (D) is a sectional view showing a conventional mounting structure.

FIG. 2 is a layer structure diagram of the multilayer inductor of the present embodiment.

FIG. 3 is a pattern diagram showing a side through hole for forming a wraparound electrode portion and a conductor filling the same in the present invention.

FIG. 4 is a layer structure diagram of a multilayer inductor for multi-cavity production according to the present embodiment.

FIG. 5 is a perspective view showing a state in which green sheets are stacked from the state shown in FIG. 4;

FIG. 6 is a plan view showing a relationship among an inductor, a cutting line, and a through hole in the present embodiment.

FIG. 7 is a diagram showing a comparison of the bonding strength between the embodiment of the present invention and the conventional example.

FIG. 8A is a layer structure diagram of a conventional multilayer inductor,
(B) is a perspective view thereof.

FIG. 9A is a perspective view showing another example of the conventional multilayer inductor, and FIG. 9B is a side view for explaining the problem.

10A is a layer structure diagram showing another example of a conventional multilayer inductor, and FIG. 10B is a perspective view thereof.

[Explanation of symbols]

1: laminate, 1a to 1m: green sheet, 2a to 2
h: coil conductor, 3a to 3m: through hole, 4: conductor, 21, 21a, 21b: terminal electrode, 22: wraparound electrode portion, 22a to 22c: conductor, 33: side through hole, 33A: through hole, 35, 36: Cutting line

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroki Fukumoto 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation F-term (reference) 5E062 FG07 FG11 5E070 CB13 EA01

Claims (5)

[Claims] 1. A laminated inductor having a substantially rectangular parallelepiped shape in which an inductor is formed inside a laminated body, having terminal electrodes on both end surfaces in the laminating direction of the laminated body and four peripheral surfaces near the both end surfaces. 3. The multilayer inductor according to claim 1, further comprising a recessed wraparound electrode portion that is continuous with the terminal electrode except for a corner portion. 2. The multilayer inductor according to claim 1, wherein the depth of the recess of the wraparound electrode portion is 14 μm or more. 3. A plurality of multi-piece green sheets having through holes filled with a conductor paste for forming inductor coil conductors and connecting between the coil conductors, and green sheets on both sides of these green sheets. A terminal electrode side 1 having a through hole filled with a conductive paste for connecting the terminal electrode on the end face and the coil conductor.
And at least a part of the green sheet on the terminal electrode side, between adjacent inductor forming regions, forming a through hole for forming a side through hole filled with a conductive paste, At least the shrinkage of the conductor paste in the side through hole is set to be larger than the shrinkage of the green sheet in advance, and the green sheet on which the coil conductor is formed and the terminal electrode side green sheets on both sides thereof are overlapped,
The terminal electrode paste is stacked on the end surface, the stacked green sheets are pressed, and the individual through-chips are formed by cutting the through-holes for forming the side through-holes at the center, and then sintering. Wherein a recessed wraparound electrode portion which is continuous with the terminal electrode on the end surface is formed in a portion excluding the four corner portions near the end surface due to a difference in shrinkage ratio between the conductor paste and the green sheet. Manufacturing method of multilayer inductor. 4. The method of manufacturing a multilayer inductor according to claim 3, wherein the conductor paste for forming the terminal electrode and the wraparound electrode portion has a silver content of 77.5 to 89 wt.
%, The glass content is 3.5 to 5.2 wt%, the remainder is vehicle, and the average particle size of the silver powder is 0.5 to 0.8 μm,
A method for manufacturing a multilayer inductor, wherein a glass softening point temperature is 790 to 830 ° C. 5. The method for manufacturing a multilayer inductor according to claim 3, wherein the through hole for forming the side through hole has an oval shape.