AGY Introduces L-Glass™ Fiber for High Frequency, Improved Signal Integrity Circuit Designs

March 24th, 2009 by

Aiken, SC, USA – (March 24, 2009) – In response to the rapid development of highspeed
digital electronic systems, AGY, a leading global producer of glass fiber yarns and highstrength
glass fiber reinforcements, has introduced L-Glass™, a new low-loss glass fiber yarn
for printed wiring board (PWB) applications. The low dielectric constant (Dk) and low
dissipation factor (Df) properties of L-Glass fiber are ideally suited for designs requiring
increased signal speeds and better signal integrity than traditional E-Glass/epoxy substrate

According to Scott Northrup, Director of New Business Development at AGY,
“Substrate materials that provide low dielectric constant and low dissipation factor properties
have become an essential element of high-speed digital systems such as mobile communication
base stations, high-end routers and servers, and high speed storage networks. As these systems
move to higher processing speeds, substrates with low-loss properties are needed to ensure the
speed and integrity of the signals.”

Low-loss laminates for high-speed applications have traditionally been produced in one
of two ways. In one method, a higher performing epoxy resin system is used in conjunction
with E-Glass. This approach limits the achievable Dk and Df properties.
The second method combines very low Dk/Df resins, such as PTFE, with ceramic filler
and a much lower E-Glass content. While these systems can achieve much lower Df/Dk
properties, they suffer from high material and processing costs. The low glass loading also
reduces the dimensional stability of the laminate. The use of L-Glass fiber overcomes these
limitations by allowing epoxy resin systems to achieve much lower Dk/Df properties, and the
PTFE-based systems to use a higher glass loading.

At 10 GHz L-Glass fiber has a dielectric constant of 4.86 and a dissipation factor of
0.0050 whereas E-Glass has a dielectric constant of 6.81 and a dissipation factor of 0.0060 at
10 GHz. The coefficient of thermal expansion (CTE) of L-Glass fiber is 3.9 ppm/°C compared
to 5.4 ppm/°C for E-Glass. This makes L-Glass fiber an attractive material for use in IC
packaging, where CTE mismatches with silicon are magnified due to the thermal environment
and can cause defects.

AGY’s L-Glass fibers will be available in a variety of yarn counts, that will allow
production of low-loss fabrics analogous to styles 106, 1080, 2113/2313, and 2116. Additional
yarn counts can be produced as needed to meet market demands.
“L-Glass fiber is a cost-effective alternative to current systems,” added Northrup. “The
low- loss properties make it ideal for applications operating at the highest signal speeds and
provide designers a compelling alternative to traditional materials.”