JPH02103916A - Manufacture of inductance element - Google Patents

Abstract

PURPOSE:To enlarge inductance by mixing ferrite powder and resin powder, and then forming it into a tablet without heating and kneading it, and sealing a magnetic-core or air-core coil with the aid of the tablet. CONSTITUTION:Resin for bonding is applied as an adhesive 5 on a metallic terminal 2 being one part of a lead frame, and thereon an Ni-Zn ferrite core 3 is placed, and this adhesive 5 is solidified so as to fix the ferrite core 3 and the metallic plate terminal 2. Next, copper wire covered with insulator is wound around the ferrite core 3 and is made a coil 4, and lead wires 6 at both ends are connected to metallic plate terminals 2 by soldering. Next, ferrite powder and epoxy resin powder are mixed and are made into a tablet by compression molding. The core 3 is put in a die and is heated, and the tablet is put in and is pressurized and is sealed and molded with an armour resin molding 1. It is removed from the die and a molding 1 is solidified, and the terminals 2 are cut off from the lead frame and are bent and are made into an inductance element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an inductance element used in various electronic devices.

BACKGROUND OF THE INVENTION In recent years, as electronic devices have become lighter, thinner, and smaller, electronic components have become more densely packaged, and there is a strong demand for smaller and thinner electronic components. Under these circumstances, inductance elements are larger in size than resistors and capacitors, and there are particularly strong demands for miniaturization and magnetic shielding.

FIG. 1 schematically shows an example of a magnetically shielded wire-wound inductance element. The outline of the manufacturing method for this type of inductance element is to apply an adhesive 5 to the metal plate terminal part 2 of a part of the lead frame, and apply a ferrite core 3 on top of the adhesive 5.
After that, the insulated copper wire is wound around the ferrite core 3 to form the coil 4, and the two lead wires 6 at the ends of the coil 4 are connected to the opposing metal plate terminal portions, one each. Connect to each of 2. In this state, it is placed in a mold of a transfer molding machine and sealed using a resin containing ferrite powder to produce an exterior resin molded body 1. After solidifying the exterior resin molded body 1 by heat treatment as necessary, the metal terminal portion 2 is separated from the lead frame and bent to complete the inductance element.

The ferrite powder-containing resin used in this manufacturing method is a mixture of ferrite powder and resin (e.g. epoxy resin),
The ferrite powder is heated and kneaded in a kneading machine such as a hot roll machine at a raised temperature to uniformly disperse the ferrite powder in the resin, then rapidly cooled, crushed, and pressure-molded into cylindrical tablets.

Problems to be Solved by the Invention The inductance L of the inductance element manufactured by the conventional manufacturing method described above does not have a size that fully meets the needs of the user, and it is strongly desired to further increase the inductance L. ing.

Looking at the chip inductors currently on the market, the horizontal 3.
For the 2M, 2.5xm long, 2.2ff thick type, the inductance L of the magnetic shield type is 120μH.
However, it is said to be smaller and will become the main product from now on. There is no wire-wound type for the type with a width of 3.2 m, length of 1.6 m, and thickness of 1.11 IFM, and the laminated type has a maximum of 33 μH. With the current trend toward high-density surface mounting, there is a strong demand for magnetically shielded type chip inductors, and in particular, chip inductors with a small size and high inductance L are desired.

An object of the present invention is to further increase the inductance L of a magnetically shielded wire-wound inductance element.

In wire-wound inductance elements, magnetic flux is generated by high-frequency current flowing through the coil, and the magnetic flux forms a closed loop through the ferrite core and the exterior resin molded body. Therefore, the inductance L increases by increasing the magnetic permeability μ of the exterior resin molded body.

It is known that the magnetic permeability μ of a ferrite core decreases when it is subjected to pressure due to curing shrinkage of its exterior resin molded body, and one of the major challenges has traditionally been how to reduce the curing shrinkage of the exterior resin molded body. However, low stress resins have now been developed and used.

The same thing can be said about the ferrite powder contained in the exterior resin molded body, but since a low stress resin is used as mentioned above, the inventors further broadened their view of stress and added it to the ferrite powder itself. The present invention was made based on the findings of this study.

As a means to solve the problem, the present invention mixes ferrite powder and resin powder, mixes them uniformly, and then pressure-molds them into a cylindrical tablet without heating and mixing, and uses this tablet to transfer The coil and metal plate terminal are molded against soil to create an exterior resin molded body, which is then used as an inductance element.

Effect: With this configuration, the ferrite powder is not subjected to a kneading machine such as a hot roll machine together with the resin, so it is not subjected to the enormous pressure applied during kneading. Therefore, the magnetic properties of the ferrite powder do not deteriorate due to pressure such as residual stress, and the magnetic permeability μ of the exterior resin molded body made by transfer molding is improved compared to the conventional one, and L of the inductance element is increased.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

A detailed explanation will be given using a schematic diagram of an example of a wire-wound inductance element shown in FIG.

Apply adhesive resin as an adhesive 6 to the metal plate terminal 2, which is a part of the lead frame, place the N-needle Zn-based ferrite core 3 on top of it, and solidify the adhesive 6 to bond the ferrite core 3 and the metal plate. Terminal 2 was fixed. Next, copper wire diameter 3
A 0 μm insulated copper wire was wound around a ferrite core 3 with 50 turns to form a coil 4, and lead wires 6 at both ends of the coil 4 were connected to metal plate terminals 2 by soldering.

On the other hand, an N-nee Zn-based ferrite calcined ingot was crushed and
The powder was classified into powders with a particle size of 106 μm, and a coupling agent was applied and dried to improve the adhesion between the powder surface and the resin.

Also, mix the epoxy resin base resin, mold release agent, and other additives and knead at 80 to 90°C with hot rolls, then add the curing agent and curing accelerator to the place where the mixture is sufficiently kneaded. It was then rapidly cooled and pulverized to form a powder of 150 μm or less.

These ferrite powders and epoxy resin powders were mixed together so that the ferrite powder content was 76% by weight, and the mixture was sufficiently stirred. This mixed powder was compression molded to form a diameter of 8 lines.
I made it into a tablet with a length of 13fl.

The lead frame on which the ferrite core 3 on which the coil 4 described above is wound is fixed is placed in the mold of a transfer molding machine and the temperature is raised to 170, at which the resin hardens in a short time.
°C, the prepared tablet was put into the mold, and it was pressurized at 120 kg/c11, which is higher than the normal molding pressure car rokg/cA, and sealed with the exterior resin molded body 1. After being removed from the mold, the exterior resin molded body 1 is cured to almost completely solidify it, and then the metal plate terminal 2 is separated from the lead frame and bent to form a product with a width of 3.2 fl, a length of 1.6 Jff, and a thickness of 1.1 mm.
A 1n inductance element was used.

Also, for comparison, 46 to 10 classified as before.
A coupling agent was applied to 6 μm Ni-Zn ferrite powder and dried, and this was put into a mixture of an epoxy resin base resin, a mold release agent, and other additives, and kneaded with hot rolls until thoroughly mixed. After kneading, a curing agent and a curing accelerator were added, kneaded, rapidly cooled, and pulverized. The amount of ferrite powder filled was 76% by weight, the same as described above. This resin powder containing ferrite powder was compression molded to form a tablet having the same shape as described above. This tablet was sealed and molded using a transfer molding machine under a pressure of 70 kg/d in the same manner as above to produce an inductance element having a width of 3.2 jff, a diameter of 11.6 ff, and a thickness of 1.1 silk.

When the characteristics of these two types of inductance elements were measured, the results were as shown in the table below.

The inductance L of the product of the present invention was improved by 18% compared to the comparative product.

Also, using two types of tablets made in the same manner, the outer diameter was 10 mm using a transfer molding machine.

Create a ring core with an inner diameter of 411N and a cross section of 3H in diameter,
An insulated copper wire having a diameter of 0.20H was wound uniformly for 40 turns, and the magnetic permeability μiac of the resin containing ferrite powder was measured. The results were 6.7 using the conventional method of tablets kneaded with hot rolls, and 7.0 using the tablets of the present invention, an improvement of about 23%. When the coercive force H6 of this ring core was measured, it was 6.606 using the conventional method, whereas it was 6.200 using the method of the present invention, which was about a 20% decrease. From the above results, according to the method of the present invention, compared to the conventional method, the ferrite powder-containing resin of the exterior resin molded body 1 has a coercive force of about 2.
The magnetic permeability was 23% higher, and as a result, the inductance of the inductance element was 61 μH, which was 18% higher. Width: 3.2ff, height: 1.
6. As an inductance element with a thickness of 1.1 ff and a magnetic shield type, the maximum value of the multilayer type is 33 μH, which is 60% larger than the maximum value of 33 μH, which is excellent.

In this example, the structure of the inductance element uses a ferrite core as the magnetic core, but in an inductance element of the type in which the magnetic core is eliminated and a coreless coil is used, and the ferrite magnetic core is filled with a resin containing ferrite powder. The method of the present invention is also applicable.

In addition, since heating and mixing are not performed in the present invention, in order to make the binding properties of the ferrite powder and resin as good as those obtained by heating and kneading, the surface of the ferrite powder is modified with a camping agent, and the adhesive properties during transfer molding are By raising the pressure higher than normal pressure, we made it so that there would be no problem in practical use.

In addition to epoxy resins, thermosetting resins such as phenol resins and unsaturated polyester resins, and thermoplastic resins such as nylon, pps, and G-crystalline polymers can also be used as resins.

Effects of the Invention As described above, according to the present invention, the ferrite powder contained in the resin is not subjected to a strong processing force during heating and kneading, so there is no residual stress at the time of cross-wiring, and the magnetic field of the ferrite powder is reduced. Properties are not degraded by stress. Therefore, when compared with the conventional method, the coercive force rHa becomes smaller and the magnetic permeability μi1° becomes larger.Therefore, the inductance of the inductance element according to the present invention is approximately 20% larger than that of the conventional method. effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a magnetic shield type wire-wound inductance element obtained by the inductance element manufacturing method of the present invention. 1... Exterior resin molded body, 2... Metal plate terminal, 3... Ferrite core, 4...
Coil, 6...Adhesive, 6...Leader wire. Name of agent: Patent attorney Shigetaka Awano and one other person I
−・− 2−・ 3−・ 4−・ 5−・・ 6−・・ Exterior metal hukoi girder E1 巳も 膓 FXL description body development light core FII zelkova

Claims (1)

[Claims] A method for producing an inductance element, which comprises mixing ferrite powder and resin powder and then forming them into a tablet without heating and kneading, and using this tablet to encapsulate and mold a coil with a magnetic core or an air-core coil. .