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| SEM photo of wiring with 12µm pitch |
Toray Industries, Inc. today announced that it has succeeded
in the development of a flexible circuit board for IC mounting that boasts the
world’s highest
pitch density of 12µm for the first time in the world. The application
of this technology will help in the further miniaturization, performance improvement
and cost reduction of IT devices such as cellular phones and LCD TVs1).
This technology enables the commercial production of flexible circuit board for
IC mounting with pitch density below 20µm, considered difficult to achieve
until now, by combining the technology that precisely controls the dimensional
change of polyimide film and the pattern forming technology using semi-additive
method, which assists in achieving high-density.
Toray has installed experimental facilities that can produce up to 1 million
pieces of flexible circuit boards per month within its Seta plant and is carrying
out “Advanced Materials Project” aimed at introducing the product
to the market in fiscal 2006. A prototype with a wiring pitch of 20µm level
is currently under evaluation by customers.
Toray Group is engaged in a wide range of operations in the field of flexible
circuit boards for IC mounting and related materials, and the company expects
to capture new markets (market valued at several tens of billion yen) by utilizing
this technology in the future.
The technological breakthrough achieved this time is as follows:
| 1. |
High-density wire with 12µm pitch made possible for
the first time in the world
Currently, the mass production of chip-on-film (COF) with wiring pitch up to
30µm has already started. The existing technology, however, is nearing
the limits in terms of miniaturization since it is difficult to control the dimensional
changes in polyimide films. By revolutionizing the processing technology, Toray
made it possible to have wires with 12µm pitch (5µm for line width
and 7µm for space). |
| 2. |
Achieving a position accuracy of ±0.001%, improving
the accuracy by one digit
By combining the minute pattern forming technology mastered through production
of LCD color filters with the new technology that controls the dimensional changes
in polyimide films and by further incorporating advanced plating technology and
insulation reliability technology, the company succeeded in improving the “position
accuracy,” which expresses the smallness of the error of dimension, from ±0.04%,
the value considered to be the limitation so far, by one digit to ±0.001%2). |
| 3. |
Securing high-level insulation reliability3)
A high-level insulation reliability (electrical strength above 50V) is required
in flexible circuit boards used for mounting LCD driver ICs. However, the existing
technology couldn’t ensure such reliability and, along with the aforementioned
accuracy issue, this was a hurdle in achieving miniaturization. Toray this time
succeeded in securing a high level of insulation reliability by utilizing minute
area analysis technology and polymer processing technology. |
| 4. |
Achieving wire thickness uniformity of ±10%
The technology announced this time employs semi-additive method, which assists
in achieving high-density. In general, however, it is difficult to ensure uniformity
of wire thickness with semi-additive method, making it an obstacle in fine pitch
IC bonding. Toray achieved a wire thickness uniformity of ±10% for copper
plating using semi-additive method through its unique, revolutionary plating
technology. |
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[Notes]
| 1) |
When pursuing narrow pitch and high density qualities for
wires, it not only leads to the miniaturization of circuit boards but also reduces
the size of the LCD TVs’ driver ICs and enables the reduction in the number
of ICs used (reductions in cost). |
| 2) |
In flexible circuit boards for IC mounting such as COF based
on existing technologies, the limitation on position accuracy is considered to
be about ±0.04%. This is attributed to the dimension changes occurring
in the polyimide film that forms the base due to expansion or shrinkage caused
by the influence of temperature or humidity, don’t completely recover their
original levels even after the temperature or humidity conditions are back to
the original levels. Toray developed a revolutionary technology to control the
dimension changes occurring when processing polyimide film by exploiting its
technical knowledge on polyimide films accumulated over the years and also its
expertise in handling film processing, thus leading to the realization of remarkably
high position accuracy. This technology removed the limitation of 30µm
pitch imposed by IC bonding accuracy and even a pitch less than 10µm has
become possible. |
| 3) |
In insulation reliability tests (85°C, 85%RH, 50V applied)
with existing technologies, it is difficult to maintain an insulating resistance
of more than 1E+8Ω for 1,000 hours with 30µm wiring
pitch and a 12µm wiring pitch even causes a short circuit right after the
test is started. By comparison, with the newly developed technology, even a 12µm
wiring pitch maintains insulating resistance of more than 1E+8Ω for 1,000
hours. |
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