32 DESIGN007 MAGAZINE I FEBRUARY 2019
Thermosetting Prepregs
Pros
• Possible to match resin system and
electrical properties of thermosetting
laminates with an E
r
of 2.95 and above
• Superior CTE to thermoplastic bond films
• Can be desmeared and typically etched
back
Cons
• Anisotropic material
• Not available with an E
r
≤ 2.94
• Traditionally higher loss than
thermoplastic resin systems
Fusion Bonding
Pros
• Best electrical performance
• E
r
is almost perfectly matched to adjacent
laminate materials
• May be sequentially laminated depending
on copper thickness
Cons
• Not typically suited for bonding plated
subassemblies unless PTFE bond-ply
is used
• Long lamination cycle
• Extremely high lamination temperature
required ≥700°F (371°C)
• Not compatible with thermosetting resin
systems
Conclusion
As you can see, each of the discussed micro-
wave bonding methods has distinct advantages
and disadvantages that must be considered
when choosing which method will be the right
one for a specific application. PCB designers
need to fully understand these characteristics
to balance cost and performance when select-
ing the optimum bonding method.
DESIGN007
Visit I-007eBooks to download your copies
of American Standard Circuits' books today:
The Printed Circuit Designer's Guide to… Fun-
damentals of RF/Microwave PCBs and Flex
and Rigid-Flex.
Anaya Vardya is president and CEO
of American Standard Circuits.
John Bushie is ASC's application
engineering manager and a process
engineering specialist.
To read past columns or contact the authors, click here.
Scientists at Oak Ridge National Laboratory and
Hypres, a digital superconductor company, have tested
a novel cryogenic—or low-temperature—memory cell
circuit design that may boost memory storage while using
less energy in future exascale and
quantum computing applications.
The team used Josephson junctions
m a d e f ro m n i o b i u m - a n d a l u m i n u m -
based materials fabricated at Hypres
for the single-bit memory design on a
chip and demonstrated write, read, and
reset memory operations occurring on
the same circuit.
"The test showed the viability of
memory processing functions to operate faster and
more efficiently," said Yehuda Braiman, a distinguished
scientist in the computer science and mathematics
division at ORNL. "This could lead to substantially
decreased access energies and times
and allow for more circuits to occupy
less space."
Building on an initial design, ORNL's
Braiman, Niketh Nair, and Neena Imam
continue working on multi-valued mem-
ory cell circuits and large arrays of mem-
ory cells. Their first step was a ternary
memory cell circuit design.
(Source: Oak Ridge National Laboratory)
Circuit Design May Boost Memory Storage
