NEC develops smallest fibre-optic electric field probe using
27 February 2006
Tokyo, Japan. NEC Corporation has developed what it claims is the
smallest fibre-optic electric field probe, enabled through the adoption of a
nanotechnology process. The probe is used to evaluate electrical
characteristics of high-density electronic circuits.
The probe consists of an optical fibre and an electro-optical film that
is formed at its edge, which acts as a field sensor. As its lateral size of
approximately 125 µm is equivalent to that of
the diameter of an optical fibre, the probe can be inserted into narrow
spaces such as the crevice between a ball grid array (BGA) LSI package and a
printed circuit board (200 - 300 µm), enabling
evaluation of the electrical characteristics of high-density packaged
electronic circuits on printed circuit boards (PCBs). It can therefore be
used to create electrical designs for high-density electronic packages to
help achieve low-noise/low-electromagnetic interference (EMI) level
The new probe was created based on a nanotechnology process referred to as
aerosol deposition (AD), which was developed by the National Institute of
Advanced Industrial Science and Technology (AIST), Japan. This process
involves a recently developed ceramics film formation technology, which can
directly deposit complex oxide films that consist of nano-particles on any
kind of substrate material. By adopting the AD method for electro-optical
film deposition, which consists of the formation of the electric field
sensor onto an optical fiber edge surface, for the first time NEC was able
to develop the world's first film processing techniques for precise sensing
of electric fields.
The main features of the new probe are as follows:
1. Measurement of the electrical characteristics of high-density LSI
packages has been enabled by successfully reducing the probe's sensor size
to less than half of that of the smallest conventional fibre-optic electric
field probes. Its lateral size of approximately 125 µm
is equivalent to that of the diameter of an optical fibre.
2. Detection of electrical signals in devices being tested is achieved by
converting an electrical signal to an optical signal in the electro-optical
film. Since the signal is sent by an optical fibre, a wave guide that does
not contain metallic parts, the electromagnetic field surrounding the device
being test is undisturbed, resulting in the improvement of measurement
3. Development of a highly-sensitive probe owing to the formation of a
world-leading electro-optical film, lead zirconate titanate (PZT) film, on
the edge of the fibre. This structure consists of the dense agglomeration of
small particles, whose size is at a level of that of several tens of
nanometers, resulting in both high transparency and large electro-optical
In recent years, the issue of electromagnetic noise in electronic
equipment has become more serious due to an increase in the operation speed
of electronic equipment and packaging density of electronic devices. In
order to combat this, it is important to evaluate the electrical
characteristics of LSIs that are mounted on PCBs (not the evaluation of
unpackaged LSIs) and reflect the obtained results on the circuit design.
However, conventional probes can not be used with today's very small, high
density LSI packages as their size is too large to measure electrical
signals or noise in microscopic regions such as the crevice between a BGA
package and a printed circuit board.
In order to respond to these needs, NEC has been developing a probe that
is capable of measuring microscopic regions on PCBs with high density LSI
packages. Now, with the cooperation of AIST, it has succeeded in the
successful development of a microscale electric field probe consisting of an
optical fibre with a diameter of approximately 125 µm
and an electro-optical film, which is formed at the edge of the fiber.
Realized utilizing a nanotechnology process, AD, this probe boasts the
world's smallest electro-optical sensor.
NEC says it will continue to advance this research toward the improvement
of the sensitivity and the measurable frequency band of the probe with the
aim of achieving practical use by the end of March, 2007.