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Technology
 
- -- Did you aim to make the D3SH the world's smallest detection switch when you began developing it?
 - Tsuda:
Actually, this surface mount switch was OMRON's first entry into this market. mount switch market. As such, we realized that we wouldn't be able to beat the competition by simply producing a look-alike product. We launched our product development with the idea of starting right from the beginning with specifications that would surpass competitive products.
The specification that we chose as the most distinctive was size. We decided that creating the world's smallest detection switch for use in today's increasingly compact and slim cellular phones and other mobile equipment would clearly distinguish our product from the competition.
- With the idea of also giving the new switch superb reliability and operating ease, we added the targets of high operating reliability with a unique contact structure, a long 1.5-mm stroke and easy use with multi-directional detection to our development goals right from the start.
- -- What kind of line-up do you have?
- Tsuda:
Presently, the D3SH line-up consists of a standard lever type with a 1.5-mm operating stroke that detects operations in two horizontal directions relative to the printed circuit board, and a 2.0-mm long lever type. Both types come with an SPST-NO/SPST-NC contact form, right or left lever, and with or without a positioning boss.
We plan to develop other types that will also be the world's smallest, such as one that will detect operations in vertical directions relative to the printed circuit board.
- Product Variation Examples
-
| Contact Form |
Terminal |
Detection direction |
Lever |
| (SPST-NO) |
L-bend |
Right |
| Standard |
 |
|
| Long |
 |
|
| Left |
| Standard |
 |
|
| Long |
 |
|
| (SPST-NC) |
L-bend |
Right |
| Standard |
 |
|
| Long |
 |
|
| Left |
| Standard |
 |
|
| Long |
 |
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- -- What was the hardest part of developing the world's smallest detection switch?
 - Kiyono:
I'd say the most difficult challenge from the viewpoint of structural design
was achieving the 1.5-mm stroke while maintaining the world's smallest
size. After repeated design attempts, we decided to use a coil shape
for the spring. However with the conventional switch structure, lengthening
the stroke made the spring larger, which made it impossible to obtain
the world's smallest size. So we changed our thinking a bit, and decided
to have the spring turn while it underwent elastic deformation. This
made it possible to get the compact size that we wanted, while also providing
the desired stroke.
- -- So were you able to get the world's smallest size by just using a coil shape for the spring?
- Kiyono:
No, that was just the beginning, which helped us to make our target for the area of the switch. At that point, the thickness was 1.1 mm, which was 0.2 mm thicker than the target. We tried everything we could think of, but that structure just wouldn't let us shave off another 0.2 mm.
On top of that, Ohigashi and Inasaka couldn't accept the requests we made for parts and assembly precision, so there was really no choice but to change the structure itself. It was an extremely difficult decision for me to make as the person in charge of structural design, but I eventually called for a structural change.
Application example: Digital still camera- Since
we were going to change the structure anyway, I decided we may as well try
to come up with something very novel. After beating our brains to the point
of dreaming about the structure every night, I came up with the idea of giving
the coil spring a movable contact function.
This idea let us achieve our thickness goal of 0.9 mm, and also gave us enough
contact force and wiping ability to raise the contact reliability. It was like
killing two birds with one stone.
- -- I understand that heat resistance was also a major challenge.
- Kiyono:
Yes, because the D3SH is a surface mount switch, it had to be designed to withstand
the temperatures in the reflow oven, which can go above 250°C. This problem,
though, wasn't entirely mine to solve. We asked for help from Mr. Morii who specializes in molding materials and lubricants, and Mr. Ohigashi who was
in charge of precision processing. We eventually solved the heat resistance
problem by a team effort among the people in charge of structural design, materials,
and processing technology.
I think you'd be better off to ask Mr. Morii and Mr. Ohigashi about this. For
my part, I mostly just gave them unreasonable requests. (Mr. Kiyono laughs)
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