Inductor Guide

Anecdote of inductor development [No. 4]Japan's first air-core horizontal wire-wound coil

Nowadays if you look inside the mobile phones that everyone is using, most contain an LQW series horizontal wire-wound air-core coil. This part is coated with blue resin, so it stands out and is easy to find. It also has good characteristics, so it is convenient for various customers.
I remember long ago when a customer came to Murata with a complaint, being told that, "Our set won't produce the desired characteristics without this component, so please address this complaint!" At the time I was busy dealing with complaints, but looking back now I am extremely grateful for receiving their feedback.
It is precisely because of the cooperation of various parties that the LQW series, which are irregularly shaped parts among high-frequency inductors, developed into a product that has achieved such widespread use. In this column I would like to describe some of these developments.

I joined Murata just as mobile phones were beginning to appear. Our competitors were also working tirelessly to prepare their product lineups for this market. The trend at the time was toward miniaturization, and our competitors were pushing miniaturization by the use of layering and other methods. On the other hand, the section to which I was assigned was in charge of wire-wound inductors, and there were debates as to whether conventional wire-winding methods could keep up with the miniaturization trend. However, our supervisors at the time were quite strong willed, and it was decided to develop a miniature wire-wound inductor.

The biggest issue for miniaturization is that wires are wrapped around a core. We wanted to use the smallest size (1.6 × 0.8 × 0.8 mm) core at the time, so the degree of difficulty was high, and though Murata's Product Technology Department tried their best, they could not achieve satisfactory results. Some members of our department began to wonder openly whether such a technology was even possible.

Amid these efforts, a certain coil-winding machine manufacturer came to us with proposals as to how it could be done. Needless to say this was extremely welcome news. The developed equipment was simple, accurate, and satisfied all the functions we required. Thanks to this equipment, we were able to commercialize a miniature wire-wound inductor.
Some time thereafter, while meeting with a person in a high position at that coil-winding machine manufacturer, I learned that in the planning stage, the manufacturer's employees also did not think that such a coil-winding machine could be made. However, a certain technician brought in a large model of a core (approximately 30 cm) and enthusiastically described an image of equipment for winding wires around that core. Seeing that enthusiasm and the large model, people began to reconsider that, contrary to expectations, it just might be possible, so the project proceeded and the coil-winding machine was created.
I am truly grateful for the presentation abilities and enthusiasm of that technician. 
I believe that had it not been for that technician and others, this part would not have been commercialized. I feel that I was given an excellent opportunity to achieve fine work in connection with various people, and to this day remain grateful to all related parties.

Photograph showing the LQW18A series exterior

Written by: T.T., Product Development Dept.1, EMI Filter Division

The information presented in this article was current as of the date of publication. Please note that it may differ from the latest information.

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