JPH0262011A - Inductance element and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an inductance element whose characteristic is excellent and which is small-sized and thin by a method wherein an air-core coil or a coil containing a magnetic core is sealed and molded by using a synthetic resin containing a ferrite powder and particle diameters of the ferrite powder are set at prescribed values. CONSTITUTION:An air-core coil or a coil 5 containing a magnetic coil is sealed and molded by using a synthetic resin 7 containing a ferrite powder. A main part of the ferrite powder is constituted of a powder which has mixed a large- diameter powder of 20 to 210mum with a small-diameter powder of 0.5 to 10mum in a weight ratio of 1:0.2 to 0.5. Thereby, it is possible to obtain an inductance element whose characteristic is high and which has been made small-sized and thin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inductance element used in various electronic devices and a method for manufacturing the same.

2. Description of the Related Art As shown in FIG. 4, a conventional inductance element is made by winding a copper wire 2 having an insulating coating around a magnetic core or an air-core bobbin 1 and connecting it to a terminal 3 to form a coil. The wire-wound type, which is sealed and molded using Step 4, is the mainstream.

BACKGROUND ART In recent years, as electronic devices have become lighter, thinner, shorter and smaller, electronic components have been mounted in higher density, and there is a strong demand for smaller and thinner electronic components used in such devices.

Under these circumstances, since the above-mentioned wire-wound inductance element is an open magnetic path type, it was difficult to make the shape smaller and thinner while maintaining the inductance value and Q value that indicate the characteristics. By mixing ferrite powder, which is a soft magnetic material, into the resin to create a closed magnetic circuit type, a smaller size and thinner structure has been achieved and has been put into practical use. In addition, this closed magnetic circuit type has a magnetic shielding effect, reduces leakage of magnetic flux to peripheral components, and enables high-density mounting, and is expected to develop in the future.

The ferrite powder used in this closed magnetic circuit type has a fine average particle size of 1 to 11 μm (Japanese Patent Application Laid-Open No. 129357-1982)
(see Japanese Patent Application Laid-open No. 163354/1983).

The reason why powder with such a fine particle size is used is thought to be that when calcined ferrite pellets are subjected to a crusher, they tend to become particles of this size, and that they are easily mixed and dispersed in the resin.

Note that the filling rate of the ferrite powder is preferably as high as possible from the viewpoint of magnetic properties. However, the transfer molding method is mainly used as a sealing molding method for this type of inductance element using thermosetting resin. The filling rate is limited to approximately 80% by weight.

Problems to be Solved by the Invention As already mentioned, with the trend toward high-density surface mounting of electronic components,
As resistors and capacitors are becoming smaller and thinner, inductance elements are becoming smaller.

Thinner devices are lagging behind, and even though wire-wound inductance elements have been made smaller by using a closed magnetic circuit type, they still have a large volume and a high height, so there is a strong desire to make them smaller and thinner.

In order to meet this demand for this wire-wound inductance element, the most effective solution is to improve the characteristics of the sealed molded part, which is mainly made of ferrite powder and resin, of the closed magnetic circuit inductance element. This is a countermeasure, and the present invention aims to provide an inductance element with high characteristics in which this portion has high magnetic permeability, and an inductance element that is thereby made smaller and thinner.

Means for Solving the Problems In order to solve the above problems, the inductance element of the present invention contains ferrite powder mixed in the sealing molding resin in an amount of 20 to 20%.
2107zE11 large particle size powder and 0.5 to 10 μm
The ferrite powder is made of a mixture of small particle size powders in a weight ratio of 1:0.2 to 0.6, and is sealed and molded with a resin mixed with this ferrite powder.

Further, this ferrite powder having a large particle size of 20 to 210 μm is mainly composed of an aggregate sintered body of particles having a small particle size of 0.5 to 10 μm.

Furthermore, as a manufacturing method, ferrite powder is prepared by mixing ferrite powder with a large particle size of 20 to 210 μm and ferrite powder with a small particle size of 0.5 to 10 μm in a weight ratio of 1:0.2 to 0.60. The mixture is mixed and kneaded with a synthetic resin and additives are added as necessary, and an air-core coil or a coil with a magnetic core is sealed and molded with this mixed-kneaded product, and solidified as necessary.

Effect: By having the above configuration, it is possible to provide an inductance element that has high characteristics and is smaller and thinner.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, the basic technical idea of the present invention will be explained.

Ferrite powder is mainly made by crushing calcined pellets, and its magnetic properties, especially coercive force, are 0.10 for sintered bodies.
While it is small and excellent at around 55, powder has around 1000. AC initial permeability (μiac)
Even if a sintered body with a high μiac is crushed or a sintered body with a low μiac is crushed, the coercive force of the resulting powder is large.For this reason, resin ferrite mixed with resin has an excellent high μiac. It is thought that it would be difficult to make a soft magnetic material with this, and detailed studies have not been made.

The present inventors investigated the relationship between the particle size and coercive force of the powder, and found that as the particle size increases, the coercive force decreases. It has become clear that it is an excellent material. Therefore, we created resin ferrite by keeping the filling rate of ferrite powder constant and mixing and kneading the ferrite powder with different particle sizes.In order to clarify the caac, we molded a ring core and wound it into an LCR meter. The inductance L was measured and μiac was obtained. The results are shown in FIG. From FIG. 3, it is clear that when the particle size is 20 μm or more, μiac becomes larger than the conventional case where the particle size is about 10 μm or less. This is particularly noticeable when the diameter is 46 μm or more. However, when the thickness is 210 μm or more, there is a restriction on the gate height during molding, and the flow does not flow sufficiently, resulting in a decrease in μiac. Therefore, the particle size of the ferrite powder mixed in the resin ferrite is 20 to 210 μm, preferably 45 to 1
60 μm is suitable, and an application for the invention has already been filed based on this.

As a method for further improving μiac, it is possible to increase the filling rate of ferrite powder into the resin. It has long been known that the filling rate can be increased by inserting small-sized particles into the gaps created by large-sized particles, and when this method was studied, it was found that μiac was significantly improved. I was able to discover new facts in this. If we organize the data with a constant ferrite filling rate, we find that when small particle size powder is mixed in a certain proportion, μ
The goal is to improve iac. An example is shown in FIG. This is 45 to 106 as a large particle size ferrite powder.
Use μm powder, 0.5 to 10 μm as small particle size powder
m powder was used. The filling rate of the ferrite powder in the resin ferrite is constant at 70% by weight. The weight of the powder with a large particle size is 1 and the weight of the powder with a small particle size is X. = μiac in the range of 0.2 to 0.6
shows a practically meaningful improvement. This is not an effect that appears due to an increase in the filling rate, which has been obvious in the past, since the filling rate of the ferrite powder is kept constant.

The present invention was made based on this new fact, and the present invention is based on this new fact. powder, in weight ratio,
The former 1 is mixed with the latter at a ratio of 0.2 to 0.5 μm, and this ferrite powder is mixed into a sealing molding resin, and additives are added as needed and mixed and kneaded to make resin ferrite. This inductance element is made by sealing and molding an air core coil or a magnetic core recoil with this resin ferrite.

Ferrite powder with a small particle size originally has a large coercive force, and resin ferrite mixed with only small particle size powder has a small μlac and poor magnetic properties, as is clear from FIG. However, if a small amount of small particle size ferrite powder is added to a large particle size ferrite powder with a large μiac, the μi
The fact that ac is improved has not been fully elucidated at present.

However, this may be inferred from the fact that the magnetic field flow is not good because the large-grained ferrite powders with high μiac are separated one by one by resin, but by getting the small-grained ferrite powder in between, the particles become smaller. The large diameter ferrite powder acts to bridge the flow of the magnetic field between the large particle diameter ferrite powders with high μiac, and the overall μia
It is thought that this improves c. It is thought that if the amount of small particle size ferrite powder is less than 0.2, its effect will be slight, and if it exceeds 0.6, the original low μiac will appear, reducing the overall μiac. .

Furthermore, when observing large-grain ferrite powder with high μiac using a scanning electron microscope, it was found that due to the difference in the heat treatment of the calcined pellets, the powder became an aggregate sintered body of small-sized particles of 0.5 to 1.0 μm. There was something there. The powder of this aggregate sintered body is formed by point contact or surface contact between fine particles.
They are sintered and stuck together in that area, and their morphology is different from that of ordinary large-grain powders in which the grains have grown sufficiently and the grain boundaries are in contact at 36°. However, although its magnetic properties are larger in terms of coercive force than general large-particle powders, it is small, and when comparing the μiac of resin ferrite, although there is a slight difference, it has a high μiac. Indicated. This is probably because the heat treatment temperature during calcination was somewhat low and the grains did not grow sufficiently.

However, when pulverizing the calcined pellets, it is easy to make the particle size uniform, which is advantageous in terms of powder production.

The resin used in the present invention is mainly an epoxy resin, but also a thermosetting resin such as a phenol resin, an unsaturated polyester resin, or nylon.

It goes without saying that thermoplastic resins such as pps and liquid crystal polymers are also effective. Additives include mold release agents and flame retardants, including stearic acid.

Coupling agents, lubricants, etc. may be added as necessary.

In addition, the powder with a small particle size of 0.5 to 10 μm was used, but this is because the size that ferrite powder is easily formed by pulverization is 0.5 to 10 μm, and if the powder is less than 0.5 μm, Because the surface area of the powder becomes larger, the amount of resin that can be taken in increases, and in order to ensure the flowability of the resin during molding, as the amount of fine powder increases, the filling rate of the ferrite powder must be lowered. Since it is currently desired to increase the filling rate of the ferrite powder as much as possible, the powder has a diameter of 0.6 μm or more.

In addition, ferrite powder is used after being classified using a classifier or sieve, but when we examined the distribution of these classified powders using a particle size distribution meter, we found that particles smaller than the restricted particle size were mixed in. The amount was 2 to 5% by weight, and there were almost no large particles. It is thought that the particles with small particle diameters were probably adsorbed to larger powders and mixed during classification, or were created when larger powders were broken during post-classification processing. In any case, even if a few pieces of powder outside the limit are mixed in, it is acceptable because it will not affect the majority of people.

Hereinafter, the present invention will be explained in detail using specific examples.

Example 1 Ni-Zn calcined pellets were crushed to a size of 0.5 to 10μ
A powder with a small particle size of m and a powder with a large particle size of 45 to 105 μm were obtained. Using these powders, the weight ratio of powder with a large particle size of 45 to 105 μm and powder with a small particle size of 0.5 to 10 μm is 1:0. (1) Ferrite powders mixed at a ratio of 1:0.33° (1:1) were prepared, and 75% by weight of each was mixed in an epoxy resin as a sealing resin, kneaded with hot rolls, and formed into a tablet. Next, a plurality of coils were prepared by winding 50 turns of insulated copper wire with a diameter of 30 μm around a drum core made of a Ni-Zn based sintered body, and bonding the ends of the coils to terminals. Next, a part of them is placed in a mold, this mold is attached to a transfer molding machine, the temperature of the mold is raised to 170°C, and then a transfer molding machine is installed using the epoxy resin tablet containing the ferrite powder described above. It was operated and sealed. After curing for a certain period of time, the sealed molded product was taken out from the mold, and after hardening at 160°C for 6 hours, the terminal part was bent to have a length of 3.2H and a width of 1.
The inductance element is finished with a height of 6ffl and a height of 1.1mm.

The same operation was then repeated to create three inductance elements with different blending ratios. L and Q of these three types of inductance elements were measured using an LCR meter. The results are shown in Table 1.

(Hereinafter, blank) From these results, it was found that the inductance element A2 of the present invention had an improvement of 12 degrees in L value compared to A1 which did not contain powder of small particle size. This rate of improvement may seem small, but in the wire-wound chip inductor 321611, the inductance value reaches saturation when the ferrite powder filling rate is 76% by weight, which allows transfer molding to produce high quality yields. This is a major improvement, and one of great industrial significance.

Example 2 A Ni-Cu-Zn based calcined pellet was broken and the fractured surface was observed using a scanning electron microscope, and lofts, which are aggregated sintered bodies of particles with a small diameter of 0.5 to 10 μm, were found. I chose it. Lightly crush this loft calcined pellet to 0.5 to 10μ
A powder with a small particle size of m and a powder with a large particle size of 45 to 160 μm were obtained. From these powders, a powder with a large particle size of 45 to 15oIIX11 and a powder with a small particle size of 0.5 to 10 μm were mixed in a weight ratio of 1:o.

(1) Mixed powders at a ratio of 1:0.2 and (2) 1:0.5 were prepared. Next, each of these ferrite powders is treated with an epoxy resin paste resin, a hardening agent, a hardening accelerator,
A mold release agent and the like were added so that the ferrite powder weighed 78% by weight, kneaded with heated rolls, rapidly cooled and pulverized, and made into tablets using a molding machine. Next, the copper wire diameter is 30
An air-core coil 6 is made by winding 28 turns of insulated copper wire with an inner diameter of 0.6fl and a height of 0.2H, and the ends of the air-core coil 6 are glued to the terminals 6 to create multiple pieces. did.

Place this part in a mold, install this mold in a transfer molding machine, raise the temperature to 170°C, then put in the tablet of epoxy resin 7 containing ferrite powder and seal it. did. After curing, it was taken out from the mold, solidified at 160° C. for about 6 hours, and 6 portions of the terminal were processed to obtain an inductance element with a length of 3.2 f, a width of 1.6 mm, and a height of 0.6 fi. FIG. 1 shows a schematic cross-section of this inductance element.

Each of the obtained inductance elements was measured with an LCR meter to determine inductance L and Q. The results are shown in Table 2.

The measurement results showed that the inductance value was improved by 25% in the case of A6 and 33% in the case of A6 compared to the case of using only large particle size powder. Q was also observed to be improved by 20 to 30%.

(Blank below) Effects of the invention As described above, in a wire-wound inductance element, a closed magnetic circuit element in which an air-core coil or a magnetic core-containing coil is encapsulated with synthetic resin mixed with ferrite powder. 2Q~210μm large particle size powder and 0.5~
By mixing small particle size powder of 10 μm with ferrite powder at a weight ratio of 1:0.6, an improvement of 10 to 33 cm was observed compared to the case of using only large particle size powder. .

Although the rate of improvement seems small, in order to mold with good quality yield in transfer molding, the filling rate of ferrite powder has a limit of about 80% by weight, so the improvement in inductance value is saturated. Therefore, it is of great industrial significance to improve L by controlling the particle size of the ferrite powder using a carefully selected ferrite material and within a determined filling rate.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing one embodiment of the inductance element of the present invention, and Fig. 2 shows a case where large particle size ferrite powder and small particle size ferrite powder are mixed at a weight ratio of 1:x. Figure 3 shows the change in the AC initial magnetic permeability μiac of the resin containing ferrite powder.
FIG. 4 is a schematic cross-sectional view showing a typical structure of a conventional inductance element. 5... Coil, 6... Terminal, 7...
...Resin containing ferrite powder. Name of agent Patent attorney Shigetaka Awano and 1 other person Figure 3 Figure 2 Figure 7 Ferrite powder incident oil 1O20 451+) 521 Q value Momme 000 m (μm) Figure 4 O+ \ Small A bottle appearance Proportion of weight χ 1 2

Claims (3)

[Claims] (1) An air-core coil or a coil with a magnetic core is sealed and molded with a synthetic resin containing ferrite powder, and the main part of the ferrite powder is a large particle size powder of 20 to 210 μm and a large particle size powder of 0.5 to 10 μm. Small particle size powder in a weight ratio of 1:
An inductance element made of powder mixed at a ratio of 0.2 to 0.5. (2) Large particle size ferrite powder is mainly 0.5 to 1
2. The inductance element according to claim 1, comprising a sintered aggregate of particles having a small diameter of 0 μm. (3) Ferrite powder with large particle size of 20 to 210 μm and 0
．． Ferrite powder with a small particle size of 5 to 10 μm in a weight ratio of 1
: Ferrite powder, the main part of which is powder mixed at a ratio of 0.2 to 0.5, is mixed and kneaded with synthetic resin and additives added as necessary, and this mixed and kneaded product is used to form air core coils or magnetic cores. A method for manufacturing an inductance element, characterized by sealing and molding an inserted coil and solidifying it as necessary.