JP3458701B2 - Electronic component and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as a monolithic ceramic capacitor and a method of manufacturing the same, and more specifically, the structure of an external electrode formed on the outer surface of an electronic component body is improved. The present invention relates to an electronic component and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional multilayer capacitor. In the multilayer capacitor 21, a plurality of internal electrodes 23a are provided in a ceramic sintered body 22 made of dielectric ceramics.
.About.23d are arranged so as to overlap each other in the thickness direction via the ceramic layer. The internal electrodes 23a and 23b are drawn to the end face 22a, and the internal electrodes 23b and 23d are drawn to the end face 22b. The external electrodes 2 are provided on the end faces 22a and 22b.
4 and 25 are formed respectively.

The external electrodes 24 and 25 are made of A having excellent conductivity.
It has a structure in which Ni layers 24b and 25b and Sn layers 24c and 25c having excellent solderability are formed on the g layers 24a and 25a.

The Ag layers 24a and 25a are formed by applying an Ag paste and baking it. Although the Ag layers 24a and 25a have excellent conductivity, they contact the solder during soldering, causing solder erosion. Therefore, the outer surfaces of the Ag layers 24a and 25a are covered with the Ni layers 24b and 25b that do not cause solder erosion. The Ni layers 24b and 25b are usually formed by electrolytic plating.

The Ni layers 24b and 25b have low solder wettability, and the solderability is not good. Therefore, the Sn layers 24c and 25c are formed to improve solderability. The Sn layers 24c and 25c are mainly formed by electrolytic plating. In addition, the Sn layers 24c, 2
In place of 5c, Sn-Pb, which also has excellent solderability,
A metal layer made of an alloy is often used.

[0006]

In the electronic component having the three-layered external electrodes 24, 25 like the multilayer capacitor 21, the external electrodes 24, 2 are used when used under high temperature and high humidity.
Sn layers 24c, 25c and Sn- located on the surface of
There was a problem that Sn in the Pb layer was ionized and moved in the direction of the electric field to cause ion migration.

When the metal ions in the surface layers of the external electrodes 24 and 25 move to the surface of the ceramic sintered body 22 due to the above-mentioned ion migration, problems such as a decrease in insulation resistance occur. Particularly, in recent years, the size of the ceramic sintered body 22 has been reduced along with the downsizing of electronic components. Therefore, when the distance between the external electrodes 24 and 25 and the internal electrode or the external electrode connected to the other party's potential is decreasing, and when the above-mentioned ion migration occurs, the insulation resistance is remarkably reduced or is extremely large. However, the ceramic sintered body 22 may be broken.

An object of the present invention is an electronic component having an external electrode formed by laminating a plurality of metal layers, which is less likely to cause a decrease in insulation resistance or destruction of an electronic component element body due to ion migration, which is reliable. An object of the present invention is to provide an electronic component having excellent properties and a manufacturing method thereof.

[0009]

According to a first aspect of the present invention, there is provided an electronic component in which first and second external electrodes are formed on a surface of an electronic component body, respectively. The second external electrode is formed on the first metal layer as the base layer and the first metal layer, and the second metal layer made of a metal in which migration is relatively hard to occur, and the second metal A third metal layer formed on the layer and having a solderability superior to that of the second metal layer .
The metal layer of Ni is made of Ni , and the second metal layer is exposed in at least one of the first and second external electrodes in the vicinity of the edge of the electrode facing the other external electrode, It is characterized in that the third metal layer is formed so as not to reach the edge.

Further , according to the present invention, in the external electrode formed so that the third metal layer does not reach the edge,
The distance between the edge of the external electrode and the electrode portion located on the outermost side from the end surface on which the external electrode is formed is E
In this case, the length d of the exposed portion of the second metal layer along the direction connecting the first and second end faces is within the range of 10% to 40% of the distance E.

According to a second aspect of the present invention, the electronic component body is formed of a ceramic body, and a plurality of internal electrodes connected to the first or second external electrode are provided in the ceramic body. Formed, thereby forming a monolithic ceramic electronic component.

According to a third aspect of the present invention, there is provided a method of manufacturing an electronic component according to the first aspect of the present invention, wherein the first and second external electrodes are formed on the surface of the electronic component body. And forming a first metal layer on the first metal layer,
And to reach the edge of the region where the first metal layer is formed, as a hard metal occurs relatively migration
A step of forming a second metal layer made of Ni , and using a metal having a soldering property superior to that of the second metal layer on the second metal layer, and at least the other of the second metal layers And a step of forming a third metal layer so as to expose the vicinity of the edge facing the second metal layer on the side so as not to reach the edge.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be made clear by giving non-limiting examples of the present invention.

1 and 2 are a sectional view and a perspective view showing a multilayer capacitor according to an embodiment of the present invention. Although not particularly limited, the multilayer capacitor 1 is configured by using a ceramic sintered body 2 made of a dielectric ceramic such as barium titanate ceramics.
The ceramic sintered body 2 has a rectangular parallelepiped shape.

Inside the ceramic sintered body 2, a plurality of internal electrodes 3a to 3d are formed so as to overlap each other in the thickness direction with a ceramic layer interposed therebetween. The internal electrodes 3a and 3c are
It is drawn out to the first end surface 2 a of the ceramic sintered body 2. The internal electrodes 3b and 3d are drawn out to the second end surface 2b facing the end surface 2a.

That is, the ceramic sintered body 2 and the internal structure thereof are the same as those of conventionally known multilayer capacitors. The feature of the multilayer capacitor 1 of this embodiment resides in the first and second external electrodes 4 and 5.

The first and second external electrodes 4 and 5 have an end face 2
It is formed so as to cover a and 2b. However, the external electrodes 4 and 5 are not limited to the end surfaces 2a and 2b, but the upper surface 2c,
It is formed so as to reach the lower surface 2d and the side surfaces 2e and 2f.

The external electrodes 4 and 5 have first metal layers 4a and 5a, second metal layers 4b and 5b, and third metal layers 4c and 5c on the outer surface of the ceramic sintered body 2, respectively. It has a structure formed in order.

The first metal layers 4a and 5a are formed by applying a conductive paste containing Ag and baking it. However, the first metals 4a and 5a may be formed by applying a conductive paste containing another metal having excellent conductivity such as Cu and baking the same. Further, the method for forming the first metal layers 4a and 5a is not limited to the conductive paste coating and baking method, and other methods such as plating and sputtering may be adopted.

Second metal layers 4b and 5b are formed in order to prevent solder erosion of the first metal layers 4a and 5a. The second metal layers 4b and 5b are the first metal layers 4a and 5b.
It is necessary to be composed of a material that can prevent solder erosion of a, and to be composed of a metal that is less likely to migrate with respect to the third metal layers 4c and 5c. Such second metal layers 4b and 5b are made of Ni.
It In this embodiment, the second metal layers 4b and 5b are formed by electrolytically plating Ni.

The second metal layers 4b and 5b are formed so as to reach the upper surface 2c and the lower surface 2d of the ceramic sintered body 2 of the first metal layer and the external electrode edges 4d and 5d reaching the side surfaces 2e and 2f. Has been done. That is, the second metal layers 4b and 5b
Are formed so as to cover all the outer surfaces of the first metal layers 4a and 5a.

The third metal layers 4c and 5c are provided to improve solderability, and in this embodiment, they are formed by electroplating Sn. The third metal layers 4c and 5c are not limited to Sn, but Sn-
It can be made of an appropriate metal material having excellent solderability such as Pb alloy.

The feature of this embodiment is that the third metal layers 4c and 5 are formed.
c is the upper surface 2c, 2d of the ceramic sintered body 2 of the first and second external electrodes 4, 5, and the second metal layer 4b, in the vicinity of the edges 4d, 5d reaching the both side surfaces 2e, 2f.
It is formed so as not to reach the end edges 4d and 5d so that 5b is exposed.

That is, as shown in FIG. 1, the edges 4 of the second metal layers 4b, 5b facing each other.
The portions near d and 5d are not covered with the third metal layers 4c and 5c and are exposed.

In this embodiment, in actual use, the electric field is, for example, the third metal layer 4c and the external electrode 5 connected to the other potential.
And the internal electrode 3b, the movement of Sn ions to the ceramic sintered body 2 due to the ion migration of Sn forming the third metal layer 4c is reliably suppressed.

As described above, since the edges of the third metal layers 4c and 5c are formed so as not to reach the edges 4d and 5d of the external electrodes 4 and 5 which face each other, the ion migration of Sn is caused. It is considered that the above can be suppressed for the following reason.

That is, the ion migration is a phenomenon in which ionized Sn mediated by water moves to the other potential side due to the potential difference. Now, in the external electrode 4, it is assumed that Sn is ionized by the adhesion of water or water at the position indicated by the arrow A on the outer surface of the third metal layer 4c. However, since the potentials of the portions indicated by arrows A to C are the same, the Sn ions deposited at the position of arrow A do not move in the direction of the position indicated by arrow B. Even if the Sn ions move to the position indicated by arrow B, the exposed portion of the second metal layer 4b has the same potential on any exposed surface. The movement from the position indicated by to the position indicated by arrow C is unlikely to occur. Therefore, the migration of Sn ions deposited on the third metal layer 4c can be reliably suppressed.

Since Ni hardly causes ion migration, even if the second metal layers 4b, 5b are formed so as to reach the edges of the first metal layers 4a, 5a, Ni ion ions Migration rarely occurs.

Preferably, the external electrode 4 will be described as a representative. The above-mentioned edge 4d of the external electrode 4 and the outermost electrode portion outside the end surface 2a where the external electrode 4 is formed are located. When the distance is E, the length d of the exposed portion of the second metal layer 4b along the direction connecting the first and second end faces 2a and 2b is in the range of 10 to 40% of the distance E. To be done. When this ratio is less than 10%, a part of the second metal layer is exposed so that the edge of the third external electrode does not reach the edge 4d of the external electrode 4, The effect of suppressing ion migration may not be sufficiently obtained, and when it exceeds 40%, the second metal layer 4 made of Ni is formed.
In some cases, the exposed area of b becomes large, the solderability deteriorates, and when it is surface-mounted on a printed circuit board or the like, it cannot be reliably joined by solder.

As for the second external electrode 5, the first external electrode 5
The external electrode 4 has the same structure. However, the third metal layers 4c and 5c are formed on both the first and second external electrodes.
Need not be formed so as not to reach the edges 4d and 5d, and at least one of them may be configured as described above. That is, it is sufficient that the second metal layer is not covered with the third metal layer in the vicinity of the edge of the external electrode facing the other external electrode.

Further, in the electronic component according to the present invention,
Other external electrodes may be provided in addition to the second external electrode, and other external electrodes additionally provided may be configured in the same manner as described above.

Further, although the ceramic sintered body 2 is used as the electronic component body in the above embodiment, the electronic component body may be made of a material other than ceramics. Further, the present invention can be applied to not only the laminated electronic component having the internal electrodes 3a to 3d but also the electronic component having no internal electrode.

The present invention can be applied to various electronic parts such as LC parts and resistance elements without being limited to capacitors. Next, a concrete experimental example of the above-described embodiment will be described and a manufacturing method thereof will be clarified.

(First Experimental Example) A dielectric ceramic containing BaTiO ₃ as a main component and an internal electrode made of Pd were used, and a well-known ceramic laminated monolithic technique was used.
The ceramic sintered body 2 shown in was obtained. By applying a conductive paste containing Ag so as to cover the end faces 2a, 2b of the ceramic sintered body 2 and baking it,
First and second metal layers 4a, 5a having a thickness of 5 to 0.2 mm
Was formed.

Next, on the surfaces of the first metal layers 4a and 5a,
1.2-1.5μ by electrolytic plating method using Watt bath
Second metal layers 4b and 5b made of a Ni film having a thickness of m were formed.

Next, an acrylic resin paint as a masking agent was coated on the second metal layers 4b and 5b. After that, the acrylic resin film on the regions where the third metal layers 4c and 5c are formed was washed away with a solvent.

Then, in the area where the acrylic resin film was washed off, Sn was plated on the second metal layers 4b and 5b by electrolytic plating using a Watt bath to 2.2.
The third metal layers 4c and 5c having a thickness of 2.5 μm were formed. Next, the acrylic resin film remaining on the outer surface was washed off with a solvent to obtain a multilayer capacitor 1.

The dimensions of the multilayer capacitor obtained as described above are 1.6 × 0.8 × 0.8 mm, and
The distance d was 50 μm, and the distance E was 0.5 mm.

For comparison, the conventional multilayer capacitor 21 (see FIG. 3) is used in the same manner as in the above embodiment except that the third metal layer is formed so as to cover the entire surface of the second metal layer.
Reference) was prepared.

Regarding the multilayer capacitor of the above embodiment and the conventional multilayer capacitor, the temperature was 85 ° C. and the relative humidity was 90.
Under a 95% environment, a DC voltage of 100 V was applied and a humidity and medium load test was performed. Table 1 below shows the number of defective products per 10,000 multilayer capacitors in this wet and medium load test.

[0041]

[Table 1]

The number of defective products in Table 1 indicates the number of multilayer capacitors in which insulation between external electrodes is defective. As is clear from Table 1, in the conventional example, one defective product per 10,000 units was generated after 2000 hours, and three defective products per 10,000 units were generated after 4000 hours. In the multilayer capacitor of the example, no defective product was generated even after 4000 hours had passed. Therefore, according to the multilayer capacitor of the present embodiment, it can be seen that the reliability under high temperature and high humidity can be improved as compared with the multilayer capacitor 21 of the conventional example.

Further, three multilayer capacitors of the conventional example which became defective after the lapse of 4000 hours were disassembled and the inside was observed. In two out of three defective products, S
It was confirmed that cracks were generated in the ceramic sintered body probably because of migration of n ions.

(Second Experimental Example) Next, a second experimental example will be described. According to the above example, except that the outer shape is 1.0 ×
0.5 x 0.5 mm multilayer capacitor, 1.6 x
Two types of multilayer capacitors having a size of 0.8 × 0.8 mm were manufactured. In addition, various laminated capacitors were produced in which the exposed widths of the second metal layers 4b and 5b, that is, the distance d was made different. However, external electrodes 4, 5
The distance E between the above-mentioned end edges 4d, 5d and the outermost portion in the direction connecting the first and second end surfaces is set to 0.3 mm and 0.5 mm, respectively, as shown in Table 2 below. did.

Sample Nos. 1 to 1 obtained as described above
For each of the multilayer capacitors of No. 1 as described in Experimental Example 1, a humidity and medium load test was performed, and a case where the insulation resistance value was less than 10 ⁹ Ω was determined to be a defective product. In addition, the number of defective products was measured according to the elapsed time in the humidity and humidity load test. The results are shown in Table 2 below.
Are also shown.

Further, after soldering each laminated capacitor to a glass epoxy substrate, the side surface of the laminated capacitor was pressed with a pin, the stress when the laminated capacitor was disengaged from the glass epoxy substrate was measured, and the bonding strength was evaluated. The results are also shown in Table 2 below.

[0047]

[Table 2]

As is clear from Table 2, the second metal layer 4
In the conventional products (Sample Nos. 1 and 6) in which b and 5b were not exposed at all, the cumulative number of failures (400 in the wet and medium load test)
The number of defective products after the lapse of 0 hours was 6 and 3, whereas in the sample numbers 2 to 5 and 7 to 11 corresponding to the examples, almost all defective products were generated after 4000 hours. After 2000 hours, no defective products were found.

In particular, the ratio of the distance d to the distance E is 10
When it was at least%, no defective product was found even after 4000 hours had passed in the wet and medium load test. In addition, in the above-mentioned joint strength evaluation measured by soldering a laminated capacitor to a glass epoxy substrate, d /
It was confirmed that when the ratio of E was 40% or less, the bonding strength was sufficient. Therefore, preferably, by setting the ratio of d / E to be in the range of 10 to 40%, it is possible to suppress the decrease in reliability due to ion migration and to bond the substrate with sufficient strength. I understand.

[0050]

According to the invention described in claim 1,
In at least one of the second external electrodes, near the edge of the electrode facing the other external electrode,
The third metal layer is formed so as not to reach the edge so that the second metal layer is exposed, and the second metal layer is made of a metal that does not easily cause migration , that is, Ni . Therefore, it is possible to effectively suppress the migration of the metal ions forming the third metal layer. Therefore, even if it is used under high temperature and high humidity,
It is possible to provide an electronic component having excellent reliability, which is unlikely to cause a decrease in insulation resistance or the like due to ion migration of the metal forming the metal layer.

[0051] Also, the edge of the external electrode, when the distance between the electrode portion located outermost from the end face which is formed in the external electrode and E, are exposed in the second metal layer Since the length d along the direction connecting the first and second end faces of the portion is set in the range of 10 to 40% of the distance E,
It is possible to more reliably suppress ion migration of the metal forming the metal layer, and it is possible to provide an electronic component having good bonding strength by soldering.

[Brief description of drawings]

FIG. 1 is a sectional view showing a multilayer capacitor as an electronic component according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of the multilayer capacitor shown in FIG.

FIG. 3 is a sectional view showing an example of a conventional multilayer capacitor.

[Explanation of symbols]

1. Multilayer capacitor 2 ... Ceramic sintered body as an electronic component body 2a, 2b ... First and second end faces 2c ... top surface 2d ... bottom surface 2e, 2f ... Sides 4, 5 ... First and second external electrodes 4a, 5a ... First metal layer 4b, 5b ... Second metal layer 4c, 5c ... Third metal layer 4d, 5d ... Edges

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-330173 (JP, A) JP-A-3-218613 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 4/00-4/42

Claims (3)

(57) [Claims] 1. An electronic component in which first and second external electrodes are respectively formed on the surface of an electronic component element body, wherein the first and second external electrodes are first base layers. A metal layer, and a second metal layer formed on the first metal layer and made of a metal in which migration is relatively unlikely to occur,
A third metal layer formed on the second metal layer and having a solderability superior to that of the second metal layer, wherein the second metal layer is made of Ni; In at least one of the first and second external electrodes, the third metal layer has the edge so that the second metal layer is exposed in the vicinity of the edge of the electrode facing the other external electrode. It is formed so as not to lead to the third
The external power supply is formed so that the metal layer of
At the pole, the edge of the external electrode and the external electrode
The electrode part located on the outermost side from the end face where the
Exposing the second metal layer when the distance from
Length d along the direction connecting the first and second end faces of the portion
Is in the range of 10% to 40% of the distance E. 2. A multilayer ceramic electronic component, wherein the electronic component body is a ceramic body, and a plurality of internal electrodes connected to the first or second external electrodes are formed in the ceramic body. The electronic component according to claim 1. 3. The method of manufacturing an electronic component according to claim 1, wherein a first metal layer for forming first and second external electrodes is formed on the surface of the electronic component body. A step of forming, and a second metal made of Ni as a metal on which migration is relatively unlikely to occur on the first metal layer so as to reach an edge of a region where the first metal layer is formed. A step of forming a layer, and a second metal layer at least on the other side of the second metal layer, the metal being superior in solderability to the second metal layer is used on the second metal layer. And a step of forming a third metal layer so as to expose the vicinity of an edge facing the edge metal and not reach the edge.