Thermosetting polymer aims to replace epoxy for pc boards
Epoxy-glass has long been the preferred material for fabricating
printed-circuit boards. However, demands for higher thermal and electrical
performance have led researchers on a mission to develop alternative materials.
One such research effort, at IBM Research Div.'s Thomas J. Watson's Research
Center (Yorktown Heights, NY), has yielded a thermosetting polymer called CYTUF
(toughened cyanate-ester resin).
The material resulted from advanced composites research focusing on
cyanate-ester compounds. Traditionally, polymer resins have outperformed epoxy
resins, but are impractical to use because of their tendency to become brittle
and crack. In IBM's CYTUF material, however, a thermoplastic additive toughens
the cyanate by forming microscopic particles that intercept the cracks and
prevent their spread through the material.
According to Dr. Alfred Viehback, manager of Advanced Polymer Materials for
IBM, the polymer provides a higher-cost, but higher-performing alternative to
epoxy-glass in computer, aerospace, automotive, and consumer electronics where
high strength and light weight are critical.
For instance, according to Viehback, the material could be used as a laminate
in MCM-L applications. Other possibilities include airplane antennas and
satellite dishes.
The CYTUF material can be manufactured through the same processes used for
epoxy-resin pc boards. Its characteristics include high thermal stability, good
electrical insulation, low moisture absorption, high strength, and inherent
flame retardancy. Also, the material bonds securely to copper. The table lists
some of the material's characteristics.
Because of its superior heat resistance, the polymer allows chips to be bonded
directly to its surface, thus possibly eliminating the need for some of the
chip packaging. Moreover, the material is easily drilled and processed without
cracking, thus improving fabrication yield. Besides its processing ease, CYTUF
can also be reinforced with materials such as Du Pont's nonwoven Aramid called
Thermount.
IBM is now selling various CYTUF-impregnated cloth in both laminated and
unlaminated form. The company is seeking licensees for the manufacturing
process used to make the material. For more information, contact Dr. Gerald
Present of IBM's Research Div.at 914-784-7650 (fax only), or .
–Spencer Chin
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