JP2008166595A - Chip component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip component capable of a solder splitting phenomenon when mounted on a circuit board. <P>SOLUTION: The chip component 2 according to the present invention has a ground electrode layer 20 and a conductive paste film 30. The conductive paste film 30 contains a conductive material and resin, the ratio of the resin per unit area of the conductive paste film 30 being ≤35 area%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chip component, and more particularly to a coil chip component that can prevent an explosion phenomenon when mounted on a circuit board.

  Conventionally, for example, a coil chip component shown in Patent Document 1 below is known. In general, in a coil chip component having a small size, it may be necessary to form an electrode film on the flange after coating the outer periphery of the coil portion around which the wire is wound with resin. In that case, since the coil portion is a step after resin coating, an electrode film baking step cannot be performed. Therefore, a conductive paste film such as Ag is formed on the surface of the conductive paste film by applying a conductive paste such as Ag to the flange and drying it to form a conductive paste film.

  It is known that a solder explosion phenomenon may occur when a coil chip component having a plating film formed on such a conductive paste film is mounted on a circuit board by a solder reflow process.

  The solder explosion phenomenon is a phenomenon in which moisture enters a molten solder through a certain route to cause a steam explosion, and the molten solder is blown off to a particle size of about 20 μm. When this explosion phenomenon occurs, there is a possibility that the solder blown in a granular form may cause a short circuit phenomenon by connecting electrodes that should not be connected. In addition, solder that has been blown into particles may be connected and connected to form a bridge.

  It is thought that the cause of the solder explosion phenomenon is that moisture remaining inside the electrode of the coil chip component is vaporized by the heating during the reflow treatment and enters the molten solder.

In particular, as shown in Patent Document 1, in the case of a coil chip part having a Ni plating film on the surface of an Ag conductive paste film, the adhesion between Ag and Ni is poor, and the conductive paste film, the plating film, There is a possibility that a gap is formed in the gap (interface), and moisture or hydrogen such as a plating solution may inadvertently enter the gap. As a result, in the solder reflow process, moisture and hydrogen remaining between the conductive paste film and the plating film are vaporized, and a part of the plating film may be ruptured to cause a solder explosion phenomenon.
JP 2000-30952 A

  The present invention has been made in view of such a situation, and an object thereof is to provide a chip component capable of preventing a solder explosion phenomenon when mounted on a circuit board.

In order to achieve the above object, a chip component according to the present invention includes:
A base electrode layer;
A chip component having a conductive paste film,
The conductive paste film includes a conductive material and a resin,
The ratio of the resin per unit area of the conductive paste film is 5 area% or more and 35 area% or less.

The chip component according to the present invention is
A core portion around which a wire is wound to form a coil;
A pair of flanges formed integrally with the core part and formed on both axial sides of the core part;
The base electrode layer covering each flange so that the connecting portion of the wire is connected;
A resin coating that covers an outer periphery of the core around which the wire is wound;
And the conductive paste film formed so as to cover the base electrode layer.

  By setting the proportion of the resin per unit area of the conductive paste film to 35 area% or less, the adhesion between the conductive paste film and the plating film formed on the conductive paste film is improved. Therefore, in the plating film forming process, it is possible to prevent the plating film from being lost, and it is possible to prevent a gap from being generated at the interface between the conductive paste film and the plating film. As a result, the solder explosion phenomenon can be prevented during the solder reflow process.

  Preferably, the unit area is 100 μm × 100 μm. Preferably, the resin is uniformly dispersed within the unit area of the conductive paste film.

   Within the unit area, the resin ratio is 35 area% or less, and the resin is uniformly dispersed in the conductive paste film, so that aggregation of the resin is suppressed, and the conductive paste film and the conductive paste Adhesion with the plating film formed on the film can be improved. As a result, the solder explosion phenomenon can be prevented during the solder reflow process.

Preferably, the particle diameter of the conductive material is 0.5 to 10 μm,
The distance between the conductive materials in the conductive paste film is 20 μm or less.

More preferably, the conductive material has a particle size of 1 to 6 μm,
The distance between the conductive materials in the conductive paste film is 12 μm or less.

  In other words, in the conductive paste film, the conductive material is distributed at a density at which the conductive materials are in contact with each other, and a large gap (gap larger than the conductive material) is not generated between the conductive materials. The resin can be uniformly dispersed therein, and the resin can be prevented from aggregating to a size larger than that of the conductive material. As a result, the adhesion between the conductive paste film and the plating film formed on the conductive paste film can be improved, and the solder explosion phenomenon can be prevented.

Preferably, a Cu plating film formed so as to cover the conductive paste film,
Ni plating film formed so as to cover the Cu plating film,
Each of the Cu plating film and the Ni plating film has a thickness of 4 to 8 μm. Moreover, it preferably has an Sn plating film formed so as to cover the Ni plating film, and the thickness of the Sn plating film is 3 to 9 μm.

  By making each plating film thicker than before, the strength of each plating film can be improved. As a result, the plating film can be prevented from being lost or broken, and the solder explosion phenomenon can be prevented.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a longitudinal sectional view of a coil chip component according to a first embodiment of the present invention.
2 is a cross-sectional view of the main part of the II part shown in FIG.
3 (A) to 3 (C) are schematic cross-sectional views showing a process of manufacturing a conductive paste film in the method for manufacturing a coil chip component according to the second embodiment of the present invention.
FIG. 4 is an electron micrograph (reflection electron image) of the outer end face of the flange of the coil chip component according to the embodiment of the present invention.
FIG. 5 is an electron micrograph (reflected electron image) of an outer end face of a flange included in a coil chip component which is a comparative example of the present invention.
FIG. 6 is a graph showing the relationship between the ratio of the resin per unit area of the conductive paste film included in each coil chip component according to the embodiment of the present invention and the occurrence rate of the solder explosion phenomenon.

(First embodiment)
As shown in FIG. 1, the coil chip component 2 according to the first embodiment of the present invention has a drum core 4 as a core member (core material). The drum core 4 is made of a ferrite material. The drum core 4 has a core part 4 a in which a wire 10 a constituting the coil part 10 is wound along the axial direction of the core 4.

  A first flange 4b and a second flange 4c are integrally formed at the first end and the second end, which are both ends in the axial direction of the core 4a. The outer diameters of the first flange 4b and the second flange 4c are larger than the outer diameter of the core part 4a.

  The cross section of the core part 4a is not particularly limited, and may be a rectangular cross section, a circular cross section, or other cross sectional shapes. The cross-sectional shapes of the first flange 4b and the second flange 4c are not particularly limited, and may be a rectangular cross-section, a circular cross-section, or other cross-sectional shapes. The first flange 4b and the second flange 4c have the same size. For example, in the case of a rectangular cross section, the length is about 0.20 to 3.20 mm and the width is about 0.20 to 3.20 mm. Moreover, the outer diameter of the core part 4a is about 0.10-2.20 mm, and the axial direction full length of the drum core 4 is about 0.50-4.50 mm.

  As shown in FIG. 1, the connecting portions 10b and 10c formed at both ends of the wire 10a constituting the coil portion 10 are connected to the base electrode layer 20 at the outer peripheral positions of the flanges 4b and 4c. The connecting portions 10b and 10c of the wire 10a are fixed to the base electrode layer 20 by means such as thermocompression bonding after the base electrode layer 20 is formed on the outer circumferences and end faces of the flanges 4b and 4c. Wire connection is secured. Alternatively, before the base electrode layer 20 is formed, the connecting portions 10b and 10c of the wire 10a are fixed to the outer circumferences of the flanges 4b and 4c by means such as caulking, and then the base electrode layer 20 is formed. May be.

  The base electrode layer 20 can be obtained by applying and forming an electrode paste containing conductive particles such as Ag, glass frit and binder resin, followed by drying and baking. Although the drying temperature in that case is not specifically limited, 100-300 degreeC and baking temperature are about 600-800 degreeC. The film thickness of the base electrode layer 20 after the baking treatment is not particularly limited, but is usually about 20 to 60 μm.

  After the base electrode layer 20 and the connecting portions 10b and 10c are connected, a resin coating is formed by molding a resin in the outer peripheral concave portion of the core portion 4a where the coil portion 10 is formed. The outer diameter of the resin coating portion 50 is approximately the same as the outer diameter of the flanges 4b and 4c.

  It does not specifically limit as resin which comprises the resin coating part 50, An epoxy resin, a phenol resin, a polyester resin etc. are illustrated.

  As shown in FIGS. 1 and 2, after the resin coating portion 50 is formed, a conductive paste film (conductive electrode film) 30 is formed so as to cover the outer peripheral surface and the outer end surface of the base electrode layer 20. . The conductive paste film 30 is formed by applying a conductive paste and then drying it. The conductive paste in this case includes, for example, conductive particles such as Ag, a binder resin, a solvent, and the like. Drying after the application of the conductive paste is performed under temperature conditions such that the resin coating 50 does not deteriorate.

  The ratio of the binder resin per unit area of the conductive paste film 30 is 5 area% or more and 35 area% or less.

  In addition, as a method of setting the ratio of the binder resin per unit area of the conductive paste film 30 to 5 area% or more and 35 area% or less, with respect to the entire conductive particles and binder resin included in the conductive paste, What is necessary is just to let the ratio of binder resin be 5 volume% or more and 35 volume% or less. If the ratio of the binder resin in the conductive paste is too small, the adhesion between the conductive paste film 30 and the base electrode layer 20 may be deteriorated, and the conductive paste film 30 may crack, and the ratio of the binder resin is too large. The completed coil chip component 2 may cause a solder explosion phenomenon. However, by setting the ratio of the binder resin in the conductive paste within the above range, these problems can be prevented.

  Preferably, the unit area is 100 μm × 100 μm. Preferably, the resin is uniformly dispersed within the unit area of the conductive paste film.

  Preferably, the particle diameter of the conductive particles is 0.5 to 10 μm, and the distance between the conductive particles in the conductive paste film 30 is 20 μm or less. More preferably, the particle diameter of the conductive particles is 1 to 6 μm, and the distance of the conductive particles in the conductive paste film 30 is 12 μm or less.

  That is, in the conductive paste film 30, the conductive particles are distributed at such a density that the conductive particles are in contact with each other, and a large gap (gap larger than the conductive particles) is not generated between the conductive particles. The binder resin can be uniformly dispersed in the electric paste film 30, and the binder resin can be prevented from agglomerating to a size larger than that of the conductive particles. As a result, the adhesion between the conductive paste film 30 and the plating film 40 formed on the conductive paste film 30 can be improved, and the solder explosion phenomenon can be prevented.

  The thickness t (FIG. 2) of the conductive paste film 30 is not particularly limited, but is preferably about 20 to 50 μm.

  After forming the conductive paste film 30, as shown in FIGS. 1 and 2, an outer electrode film 40 made of a plating film is formed outside the conductive paste film 30. Although the outer electrode film 40 may be a single layer, in the present embodiment, the outer electrode film 40 is formed of a three-layer plating film. As shown in FIG. 2, the outer electrode film 40 includes a Cu plating film 42, a Ni plating film 43 formed so as to cover the Cu plating film 42, and a Sn plating film formed so as to cover the Ni plating film 43. It consists of 44 three layers.

  Preferably, the thickness of each of the Cu plating film 42 and the Ni plating film 43 is 4 to 8 μm. Preferably, the thickness of the Sn plating film 44 is 3 to 9 μm.

  As described above, the strength of each plating film can be improved by making each plating film thicker than before. As a result, each plating film (outer electrode film 40) can be prevented from being lost or damaged, and a solder explosion phenomenon can be prevented.

  In the present embodiment, by setting the ratio of the binder resin per unit area of the conductive paste film 30 to 5 area% or more and 35 area% or less, the conductive paste film 30 and the outer electrode film 40 (Cu plating film 42). ) Is improved. Therefore, in the step of forming the outer electrode film 40, the outer electrode film 40 can be prevented from being lost, and a gap is generated at the interface between the conductive paste film 30 and the outer electrode film 40 (Cu plating film 42). Can be prevented. As a result, the solder explosion phenomenon can be prevented when performing the solder reflow process in order to mount the coil chip component 2 on the circuit board.

   In the present embodiment, the binder resin ratio is 35 area% or less on an area scale (100 μm × 100 μm unit area) where the outer electrode film 40 may be missing or damaged, and in the conductive paste film 30. By uniformly dispersing the binder resin, the aggregation of the binder resin is suppressed, and the adhesion between the conductive paste film 30 and the outer electrode film 40 can be improved. As a result, the solder explosion phenomenon can be prevented during the solder reflow process.

  Furthermore, in the present embodiment, since the conductive paste film 30 is formed, even if the outer electrode film 40 is formed on the conductive paste film 30, a plating solution is formed from the gap between the base electrode layer 20 and the coating resin 50. Can be prevented and various problems such as short circuit failure can be suppressed.

  In the present embodiment, an outer electrode film 40 composed of plating films 42 to 44 is formed on the outer periphery of the conductive paste film 30. By forming the plating films 42 to 44, mounting on a substrate or the like becomes easy.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In addition, below, description is abbreviate | omitted about the matter which is common in 1st Embodiment and 2nd Embodiment, and only the difference between both embodiment is demonstrated.

  In the present embodiment, the thickness of the conductive paste film located on the outer end face of the flanges 4b and 4c is smaller than the thickness of the conductive paste film on the outer peripheral surface of the flanges 4b and 4c. Specifically, after applying a conductive paste on the base electrode layer 20 formed on the flanges 4b and 4c, the flange 4b is applied using the steps shown in FIGS. 3 (A) to 3 (C). , 4c is made thinner than the conductive paste film 30b at the outer peripheral portion of the flanges 4b, 4c.

  First, as shown in FIG. 3A, conductive paste films 30a and 30b are formed on the outer peripheral surface and outer end surface of one flange 4b by applying a conductive paste, for example, by dipping.

  After that, before the conductive paste films 30a and 30b are dried, only the conductive paste film 30a formed on the outer end face portion of the flange 4b is replaced with the water absorbent sheet 60 as shown in FIG. The conductive paste film 30a is absorbed by water. Although it does not specifically limit as the water absorbing sheet 60, The paper material, woven fabric, nonwoven fabric, etc. which have water absorption are illustrated.

  Thereafter, as shown in FIG. 3 (C), when the outer end face of the flange 4b is pulled away from the water absorbent sheet 60, most of the conductive paste film 30a formed on the outer end face becomes water absorbent. Absorbed by the sheet 60. As a result, the thickness of the conductive paste film 30a located on the outer end face of the flange 4b is extremely thinner than the thickness of the conductive paste film 30b on the outer peripheral portion of the flange 4b. Thereafter, after the conductive paste films 30a and 30b are dried, the conductive paste films 30a and 30b are similarly formed on the outer end face and the outer peripheral face of the flange 4c.

  In the conductive paste film 30 thus formed, the thickness of the conductive paste film 30a on the outer end face portion of the flanges 4b and 4c is 0.5 to 10 μm, preferably 0.5 to 6 μm, and more preferably 0. .5-5 μm and extremely thin. Further, the conductive paste film 30b on the outer peripheral portion of the flanges 4b and 4c is about 20 to 50 μm.

  In the coil chip component according to the present embodiment, the conductive paste film 30 is formed after the resin coating portion 50 is formed. However, the thickness of the conductive paste film 30a located on the outer end face of the flanges 4b and 4c is 0. 5 to 10 μm, preferably 0.5 to 6 μm, more preferably 0.5 to 5 μm. For this reason, even if the size of the coil chip component is reduced, variations in the axial length of the coil chip component can be suppressed.

  According to the experiments by the present inventors, when the thickness of the conductive paste film 30a is 0.5 to 10 μm, the variation can be within 3.3%, and the thickness of the conductive paste film 30a is In the case of 0.5 to 6 μm, the variation can be within 2.0%. Further, when the thickness of the conductive paste film 30a is 0.5 to 5 μm, the variation can be within 1.7%.

  Since the variation in the axial length of the coil chip component can be suppressed, the land size and error of the substrate portion on which the coil chip component is mounted are less likely to occur, and mounting defects can be prevented. . Further, in a printed circuit board or the like, it is not necessary to design the land pattern with a margin, and high mounting density is facilitated.

  In the present embodiment, the ratio of the binder resin to the whole of the conductive particles and the binder resin contained in the conductive paste is 35% by volume or less. As a result, even if most of the conductive paste film 30a formed on the outer end face of each flange 4b, 4c is absorbed by the water absorbent sheet 60, the binder resin aggregates in the conductive paste film 30a on the outer end face. Can be prevented.

  In addition, as a method for making the thickness of the conductive paste film 30a located on the outer end face of each flange 4b, 4c thinner than the thickness of the conductive paste film 30b on the outer peripheral surface, the paste is absorbed by the water absorbent sheet. Other methods may be used. As such a method, there is a method of scraping the paste with a blade or the like.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, the specific cross-sectional structure of the coil chip component according to the present invention is not limited to the embodiment shown in FIG. 1 and may have various aspects.

  Next, the present invention will be described based on a more specific example, but the present invention is not limited to this example.

Example 1
As Example 1, a coil chip component 2 according to the first embodiment shown in FIG. In the production of the coil chip component 2, the binder resin ratio is 20.5% by volume and the Ag particle ratio is 79 with respect to the entire conductive particles (Ag particles) and binder resin contained in the conductive paste. .5% by volume. A conductive paste film 30 was formed using this conductive paste.

  The outer end face of the flange 4b in the obtained coil chip component 2 was photographed with an electron microscope to obtain a reflected electron image of FIG. In the reflected electron image of FIG. 4, a black region (region R) indicates a surface region in which the binder resin is unevenly distributed in the conductive paste film. Moreover, the area | region (area | region M) shown in white shows the surface area | region where Ag particle is unevenly distributed.

  The ratio of the region R shown in FIG. 4 was 20.5 area% per unit area of 100 μm × 100 μm. Further, the ratio of the region M shown in FIG. 4 was 79.5 area% per unit area of 100 μm × 100 μm. That is, in Example 1, it was confirmed that the ratio of the binder resin per unit area of the conductive paste film 30 was 35 area% or less.

  Next, the coil chip component 2 of Example 1 was mounted on a circuit board by solder reflow processing, and the presence or absence of a solder explosion phenomenon was examined. As a result, it was confirmed that the solder explosion phenomenon did not occur in the coil chip component 2 of Example 1.

Comparative Example 1
In Comparative Example 1, the ratio of binder resin to 43.83 volume% and the ratio of Ag particles to 56.17 volume% with respect to the entire conductive particles (Ag particles) and binder resin contained in the conductive paste. did. A coil chip component of Comparative Example 1 was produced under the same conditions as in Example 1 except for the ratio of each component in the conductive paste.

  In Comparative Example 1, it was confirmed that a part of the plating film (outer electrode film) was missing on the outer end face of each flange of the coil chip component.

  Next, the outer end face of the flange in the coil chip component of Comparative Example 1 was photographed with an electron microscope in the same manner as in Example 1 to obtain the reflected electron image of FIG. In the reflected electron image of FIG. 5, a black region (region R) indicates a surface region in which the binder resin is unevenly distributed in the conductive paste film. Moreover, the area | region (area | region M) shown in white shows the surface area | region where Ag particle is unevenly distributed.

  The ratio of the region R shown in FIG. 5 was 43.83 area% per unit area of 100 μm × 100 μm. Further, the ratio of the region M shown in FIG. 5 was 56.17 area% per unit area of 100 μm × 100 μm. That is, in Comparative Example 1, it was confirmed that the ratio of the binder resin per unit area of the conductive paste film 30 was over 35 area%.

  Next, under the same conditions as in Example 1, the coil chip part 2 of Comparative Example 1 was mounted on a circuit board by solder reflow processing, and the presence or absence of a solder explosion phenomenon was examined. As a result, in the coil chip part 2 of Comparative Example 1, a solder explosion phenomenon occurred.

Examples 2-5, Comparative Examples 2-8
In Examples 2 to 5 and Comparative Examples 2 to 8, the ratio of the binder resin per unit area of the conductive paste film 30 (hereinafter referred to as the resin ratio) and the unit area of the conductive paste film 30 The coil chip parts of Examples 2 to 5 and Comparative Examples 2 to 8 were used under the same conditions as in Example 1 except that the ratio of Ag particles (hereinafter referred to as Ag ratio) was set to the values shown in Table 1. 500 samples were prepared for each.

  Next, the presence or absence of a solder explosion phenomenon was examined for the samples of Examples 2 to 5 and Comparative Examples 2 to 8 by the same method as in Example 1. Then, in each of Examples 2 to 5 and Comparative Examples 2 to 8, the ratio of the number of samples that caused the solder explosion phenomenon to all samples (hereinafter referred to as the explosion occurrence rate) was obtained. The results are shown in Table 1. Moreover, in FIG. 6, the relationship between each resin ratio of Examples 2-4 and Comparative Examples 2-7 and each explosion occurrence rate is shown in a graph.

  As shown in Table 1, in Examples 2 to 5, since the resin ratio was 5 area% or more and 35 area% or less, the explosion occurrence rate was 0%, and it was confirmed that no solder explosion phenomenon occurred. . On the other hand, in Comparative Examples 2-7, since the resin ratio was 40 area% or more, it was confirmed that the solder explosion phenomenon occurred.

  In Comparative Example 8, since the resin ratio was too small, 3% by area, there was a problem that the conductive paste film 30 was cracked.

  Moreover, as shown in FIG. 6, it was confirmed that the explosion occurrence rate can be reduced to 0% by setting the resin ratio to 35 area% or less.

FIG. 1 is a longitudinal sectional view of a coil chip component according to the first embodiment of the present invention. It is principal part sectional drawing of the II section shown in FIG. FIG. 3A to FIG. 3C are schematic cross-sectional views showing a process of manufacturing a conductive paste film in the method for manufacturing a coil chip component according to the second embodiment of the present invention. FIG. 4 is an electron micrograph (reflection electron image) of the outer end face of the flange of the coil chip component according to the embodiment of the present invention. FIG. 5 is an electron micrograph (reflected electron image) of the outer end face of the flange of the coil chip component which is a comparative example of the present invention. FIG. 6 is a graph showing the relationship between the ratio of the resin per unit area of the conductive paste film included in each coil chip component according to the embodiment of the present invention and the occurrence rate of the solder explosion phenomenon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Coil chip component 4 ... Drum core 4a ... Core part 4b ... 1st flange 4c ... 2nd flange 10 ... Coil part 10a ... Wire 10b, 10c ... Connection part 20 ... Base electrode layer 30 ... Conductive paste film 30a ... Conductive paste film 30b located on the outer end face of each flange ... Conductive paste film located on the outer periphery of each flange 40 ... Outer electrode film 42, 43, 44 ... Plating film 50 ... Resin coating 60 ... Water absorbent sheet

Claims (5)

A base electrode layer;
A chip component having a conductive paste film,
The conductive paste film includes a conductive material and a resin,
A chip component, wherein a ratio of the resin per unit area of the conductive paste film is 35 area% or less. A core portion around which a wire is wound to form a coil;
A pair of flanges formed integrally with the core part and formed on both axial sides of the core part;
The base electrode layer covering each flange so that the connecting portion of the wire is connected;
A resin coating that covers an outer periphery of the core around which the wire is wound;
The chip component according to claim 1, further comprising the conductive paste film formed to cover the base electrode layer.   The chip part according to claim 1, wherein the unit area is 100 μm × 100 μm. The conductive material has a particle size of 0.5 to 10 μm,
The chip component according to claim 1, wherein a distance between the conductive materials in the conductive paste film is 20 μm or less. A Cu plating film formed to cover the conductive paste film;
Ni plating film formed so as to cover the Cu plating film,
5. The chip component according to claim 1, wherein each of the Cu plating film and the Ni plating film has a thickness of 4 to 8 μm.

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