EMI Suppression Filters (EMC and Noise Suppression)Noise Suppression Product PLT10H (Common Mode Choke Coil)
Interview episode 2

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Interview with the Development Team

The smallest Large Current Noise Filter. Skillful Product Development

<Episode 1> Conformity between a customer's needs and our own ideas at Murata started the development.

<Episode 2> As well as the product's specifications, we also considered downsizing and quality control.

<Episode 3> The PLT10H supports your design. Message from the development team:

All the demands from customers, the internal proposals (application of the existing technology) and market expectations were waiting for the development of the PLT10H. Now, how was the concept of the product determined?

Considering its future use in EV (Electric Vehicle) and HV (Hybrid car), we established reliability able to meet the requirements of automobile use.

Yamagishi responding at the interview (Development & Plant)

Yamagishi responding at the interview
(Development & Plant)

Yamagishi: First, I would like to talk about the aspect of reliability.
Because I was engaged in product development, and we had the technology to establish reliability for automobile use, we were conscious of its use in automobiles.
About the same time, we started receiving demands from customers. Customers who had been using the conventional leaded type PLT09H as common mode choke coils for automobiles requested that the PTL09H be downsized and be capable of handling larger currents.

Tsuda: And market predictions by Murata's marketing department were based on reports that the number of motors for automobile applications would grow remarkably. This was the period when the EV (Electric Vehicle) and HV (Hybrid car) markets started to grow. The electrification of automobiles also began to accelerate during this period.
Murata started preparing for the EV (Electric Vehicle) and HV (Hybrid car) at an early stage, based on our assumption that those markets would grow in the future.

Yamagishi: That's right. Demands from customers, internal proposals, and market expectations conformed very well from the beginning.

This is a hybrid large current noise filter that handles both the common mode and differential mode.

Takashima: Secondly, I would like to talk about the characteristics of the product. I have already mentioned that it meets the requirements for a "10A class current value," but it was when we were performing noise suppression of a fan motor that the concept became clearer.
Customers of motors for automobiles often request that they want to efficiently suppress noise in the FM and AM bands.
Most products from other companies suppressed noise at high frequencies, so Murata considered developing a product targeting the FM and AM bands. We believed that if did this, we could delight our customers who had problems with noise suppression in the FM and AM bands, so we added "noise suppression in the FM and AM bands" to the product concept.

Tsuda: When driving a vehicle, the noise from FM radio or AM radio bothers passengers.
If the PLT10H can suppress this noise, it can also contribute to improving the receiving characteristics, which is the basic performance of a radio.
Naturally, in order to clear the noise regulations with which automobile manufacturers must comply, the PLT10H demonstrates excellent noise suppression effectiveness.
For example, noise suppression with X/Y capacitors was a noise level that only satisfied CISPR25 Class 3. However, the number of successful examples of noise suppression able to satisfy a noise standard higher than the CISPR25 Class 4 level by adding the PLT10H is increasing steadily.

Yamagishi: In addition, this product is, unlike a common mode choke coil, a hybrid type that can also handle normal mode noise.
Therefore, one PLT10H can suppress not only common mode noise, but also normal mode noise.

Tsuda: This is an all-around hybrid large current noise filter.

This product's vertical type design reduces the base area, helping save space.

Takashima: Next, I would like to talk about the shape. We added the adoption of SMD to the concept from an early stage.
Taking an automobile parts manufacturer as an example, all the products they used were surface mounted types, except for products equivalent to the leaded type PLT10H.
Since all the components can be surface mounted by introducing an SMD type PLT10H, the components can now be mounted by reflow soldering only. We think that this is another extremely important merit.

I had extreme difficulty deciding whether the shape should be a vertical type or a horizontal type.
When we listened carefully to requests from our customers, we came to understand that the customers preferred a smaller base area even if this increased the height. This is because a taller larger capacitor is mounted on power lines. For that reason, I thought that a vertical type product with a smaller base area would contribute to space-saving on the boards, with more merits for customers.

Tsuda: While other companies offer fewer common mode choke coil products capable of handling large currents, the PLT10H can handle large currents of the 10A class even though it is remarkably small.
I believe that Murata was able to demonstrate the merits of a smaller product by applying the small size and high performance technology cultivated for mobile phone and mobile computing devices to components with large currents.

I see. I understand that the product concept was determined through discussions from various angles.
Now, would you tell me about the particular points during the development?

The selection of materials and the adoption of a specially shaped coil realized low DC resistance and low heat generation.

Takashima responding at the interview (Product Planning Dept.)

Takashima responding at the interview
(Product Planning Dept.)

Yamagishi: I carefully considered how to secure high reliability, and control the temperature increase. We resolved the above points by using a specially shaped rectangular coil. We were able to secure low DC resistance and low heat generation characteristics by using the rectangular coil to construct the terminals and coil as integral structures. Since there are no connecting portions, the terminal and coil will not dislocate, which reduces the points that must be considered in the failure modes of the reliability tests.

Takashima: We also carefully considered its casing as a vibration countermeasure.

Yamagishi: That's right. We adopted a resin casing as the cover to make a structure resistant to vibration, so that customers could use the component reliably in applications where vibration is easily generated, as in automobiles or industrial equipment.
Adding this casing maintains insulation from other components, so the product can be mounted close to these other components. This also contributes to saving space on the board.

Takashima: We also carefully selected the materials used for the casing and other parts.

Yamagishi: Yes, we carefully selected all the materials for the core, resin coating, and case.
For example, we adopted a high grade and high heat resistant resin coating for the coil that can satisfy customers using the product in automobiles. Murata's know-how was useful in the selection of the resin for the case and the core.

What about quality control?

We perform reliable quality control utilizing our knowledge of the automobile application business.

Yamagishi: We perform the same quality control as we do for automobile products, so it can be used in automobiles and so on where high reliability is demanded, as well as in consumer products.
We have also obtained qualification based on audits performed by automobile manufacturers. Therefore, I believe that our quality control is reliable.

Tsuda: And regarding capacitors, Murata has learned great deal from its many years in the automobile applications business.

Yamagishi: We also carefully consider the production line, in order to maintain high reliability. We manufacture our products on a fully automated line which, even after the material is injected, performs continuous processes including taping. In addition, we internally designed the production line and manufacturing equipment.

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