JP2600730B2 - Composite magnetic mold material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for magnetically shielding such an element by molding it to cover an inductance element such as a chip type coil element. The present invention relates to a composite magnetic molding material containing a ferrite powder, and more particularly to an improvement for improving flowability in a mold.

[Prior Art] As electronic devices have become smaller and thinner, electronic components have been chipped, and electronic components that can be mounted with higher density are desired. By the way, in order to achieve high-density mounting, the chip-type coil element must have a sufficient magnetic shielding ability. Therefore,
As disclosed in Japanese Patent Application Laid-Open No. 61-12140, a chip type coil element having a structure in which a core and a coil are covered with a composite magnetic molding material made of a resin containing 30 to 70% by weight of a ferrite powder has been proposed. . Here, a magnetic shielding effect is given to the coil element by including the ferrite powder in the above ratio in the molding material.

[Problems to be Solved by the Invention] However, in the above-described prior art, the content of the ferrite powder was 70% by weight or less, so that the effective magnetic permeability was relatively low and a sufficient shielding effect could not be obtained. Was.

Therefore, the applicant of the present application has filed a Japanese Patent Application No. 61-2688 filed earlier.
No. 86 proposed a composite magnetic molding material for a chip-type coil element with a better magnetic shielding effect. At the beginning, a composite magnetic molding material comprising a resin containing 75 to 90% by weight of a ferrite powder is described. Thus, the composite magnetic mold material proposed at the top of the above has a higher ferrite powder content than the conventional one, so
Exhibits a much better magnetic shielding effect.

By the way, it is obvious that the magnetic shielding properties of the composite magnetic molding material made of the resin containing the ferrite powder can be improved by increasing the content of the ferrite powder. However, conventionally, when ferrite powder is contained in a proportion exceeding 70% by weight, it has been practically impossible to perform molding. On the other hand, at the above-mentioned head, it is possible to mold even if the ferrite powder is contained at 75 to 90% by weight by using a thermosetting resin having a low melt viscosity.

However, as described above, even if a resin having a low melt viscosity is used, if a composite magnetic mold material containing a ferrite powder in a high ratio of 75 to 90% by weight is used, the melt viscosity naturally increases. Therefore, unless high pressure is applied during molding, desired molding cannot be performed. As a result, the element to be covered by the molding material may move from a predetermined position in the mold, or the winding constituting the coil may be cut.

As one means for reducing the melt viscosity of the composite magnetic mold material, the particle size of the contained ferrite powder is
If the pressure is increased, for example, to about 100 μm or more, the pressure required for molding decreases, but there is a problem that the molding material leaks into the gap between the molds and “burrs” occur.

Therefore, the present invention has good flowability at the time of molding, even when the ferrite powder is contained in such a large amount that an excellent magnetic shielding effect can be obtained, and therefore molding at a relatively low pressure is possible. It is an object to provide a composite magnetic mold material.

[Means for Solving the Problems] The composite magnetic mold material according to the present invention is composed of a resin containing 75 to 90% by weight of ferrite powder. , Wherein 1 to 10 parts by weight of finely divided silica is added to 100 parts by weight of the resin.

At the beginning, the content of the ferrite powder was selected to be 75 to 90% by weight. However, such a content was selected because if the content was less than 75% by weight, a sufficient magnetic shielding effect could not be obtained. On the other hand, when the content exceeds 90% by weight, even if fine powdered silica is contained while using a resin having a low melt viscosity, flowability is poor, and molding by transfer molding or injection molding is impossible. Because there is.

In addition, for the finely divided silica, the amount of addition is
1 to 10 parts by weight with respect to parts by weight is less than 1 part by weight "burr" is likely to occur, on the other hand, if more than 10 parts by weight, the viscosity of the mold material increases rather,
This is because the pressure during molding must be increased.

According to the present invention, first, a composite magnetic mold material capable of exhibiting an excellent magnetic shielding effect can be obtained by the presence of a ferrite powder having a high content of 75 to 90% by weight. Therefore, in such a case, if the magnetic molding material is applied to, for example, elements such as a chip-type coil element, high-density mounting of these elements becomes possible, which can contribute to miniaturization and thinning of electronic devices.

Further, according to the present invention, the fine powdered silica is contained in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the resin, so that the flowability at the time of molding is good, and therefore, molding under relatively low pressure is possible. Becomes Therefore, in the mold, the element to be covered by the molding material moves from a predetermined position, and also, for example, not only does the winding of the chip-type coil element break, but also “burrs” It can be prevented from occurring.

In the present invention, the finely divided silica preferably has an average particle diameter of 0.01 to 0.1 μm. Thereby, it is possible to more effectively prevent the occurrence of “burrs” due to the leakage of the molding material from the gap of the mold during molding.

Further, in the present invention, as the ferrite powder, those having a particle size of about several tens μm to 100 μm can be used. Preferably, it is used.

FIG. 1 is a cross-sectional view showing a chip-type coil element formed by molding a composite magnetic molding material according to the present invention. This chip-type coil element includes a core 1, and a coil 2 is wound around the core 1. Terminals 3 and 4 are fixed to the lower surface of the core 1, and these terminals 3 and 4 are electrically connected to respective ends of the coil 2. On the other hand, the composite magnetic molding material 5 according to the present invention is molded around the core 1 and the coil 2. This composite magnetic molding material 5 is made of a resin containing 75 to 90% by weight of ferrite powder, and 1 to 10 parts by weight of fine silica is added to 100 parts by weight of the resin.

The resin used in the above-described molding material 5 is preferably excellent in heat resistance in consideration of fixing to a substrate (not shown) by soldering or the like, and low in consideration of moldability. It is preferably of a melt viscosity. Therefore, as such a resin, it is preferable to use a thermosetting resin having a low melt viscosity, for example, an epoxy resin, a polyimide resin, a phenol resin,
Silicone resins and their copolymer resins can be used. Preferably, the melt viscosity is from 100 to 180
Those at 5000 ° C or lower are selected. This is because the lower the melt viscosity is, the easier the molding is, and the content of the ferrite powder can be increased to the extent that molding is not impossible.

When obtaining a chip type coil element as shown in FIG.
As shown in FIG. 2, the coil 2 is placed on the metal terminal material 10.
Is fixed. This terminal material 10 is finally cut along the alternate long and short dash line A,
This constitutes the terminals 3 and 4 in FIG.

Core 1 for winding coil 2 disposed on terminal material 10
Is arranged, for example, in the cavity 12a of the mold 12 shown in FIG. The molten composite magnetic molding material 5 (FIG. 1) is transferred from the transfer pot 13 to the cavity.
It is introduced in a pressurized state into 12a. In this way, transfer molding is performed, whereby the periphery of the core 1 and the coil 2 is covered with the molding material 5.

Finally, the terminal material 10 is cut along the alternate long and short dash line A in FIG. 2, and then the terminals 3 and 4 are bent along the lower surface of the core 1 so that the chip type coil element shown in FIG. Is obtained.

According to the above-described manufacturing method, the molding material 5 shown in FIG. 1 was formed by transfer molding using composite magnetic molding materials having various compositions shown in Table 1. Table 1 shows the results of comparison of the required molding pressure and the results of evaluation of the occurrence of "burrs" in Examples of the present invention and Comparative Examples 1 and 2.

As is apparent from Table 1, in the embodiment of the present invention,
Molding at a relatively low pressure was possible, and no generation of "burrs" was observed. On the other hand, Comparative Example 1
Although no burrs were observed, a relatively high pressure was required for molding. In Comparative Example 2,
Although molding at a relatively low pressure was possible, "burrs" occurred.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a chip type coil element covered with a composite magnetic mold material according to the present invention. FIG. 2 shows one step in a manufacturing method for obtaining the chip coil element shown in FIG.
FIG. 3 is a perspective view showing a state in which a core 1 around which a coil 2 is wound is fixed. FIG. 3 is a cross-sectional view illustrating a transfer molding process. In the figure, reference numeral 5 denotes a composite magnetic mold material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01F 27/02 H01F 15/02 L

Claims (3)

(57) [Claims] 1. A composite magnetic mold material comprising a resin containing 75 to 90% by weight of ferrite powder, wherein 1 to 10 parts by weight of fine silica is added to 100 parts by weight of the resin. Composite magnetic mold material. 2. The finely divided silica has an average particle size of 0.01 to 0.1 μm.
2. The composite magnetic mold material according to claim 1, wherein m is m. 3. The ferrite powder has an average particle size of 100 μm.
The composite magnetic molding material according to claim 1 or 2, wherein the composite magnetic molding material is of a degree.