42 The PCB Design Magazine • December 2015
• The power and ground grid configuration
is the best approach for providing power
delivery on double sided boards.
• Solid copper planes are a much better
solution for high-speed design.
• At high speeds, return currents flow the
path of least inductance which tends to
direct the current directly below the
signal trace.
• At high frequencies, a plane in a PCB is
really two conductors, not one conductor,
due to the skin effect.
• Any voltage drop across a ground plane
will excite cables terminating on the
board, which causes them to radiate as
dipole or monopole antennae.
• Above 10MHz, multilayer PCBs with at
least two plane layers should be seriously
considered.
• Multilayer boards reduce radiated emis-
sion by more than 10 db compared to a
double-sided board.
PCBDESIGN
References
1. Barry Olney Beyond Design Columns:
There are no One-Way Trips, The Dumping
Ground, Losing a Bit of Memory, Stackup Plan-
ning 1-4.
2. Henry Ott, Electromagnetic Compatibil-
ity Engineering.
3. Howard Johnson, High-Speed Signal
Propagation.
4. Hashimoto & Nair, Power Integrity for
Nanoscale Integrated Systems.
5. The ICD Stackup and PDN Planner, www.
icd.com.au.
beyond design
PLANE CRAzY, PART 1
Barry olney is managing
director of In-Circuit Design
Pty ltd (ICD), Australia. This
PCB design service bureau
specializes in board-level
simulation, and has developed
the ICD Stackup Planner and ICD PDN
Planner software. To read past columns,
or to contact olney, click here.
Researchers at the university of Twente re-
search institute MeSA+ have devised an elegant
method for fitting various functional coatings to
silicon microwires. The research has been pub-
lished today in the prestigious scientific journal
Advanced Materials.
Microwires made of the semi-conductor sili-
con are used in numerous fields. It is generally
necessary to 'functionalize' them, by adding a lay-
er of metal or a layer of a cata-
lyst. In most cases, the wires
are given a single layer, but in
specific instances it is useful
to put a different material on
the bottom and on the top of
the wires. However, creating
these wires proved very dif
-
ficult and the process of making them involved
many steps. Researchers from the university of
Twente have now developed a new method that
makes creating wires of this kind easy. According
to university of Twente Professor Jurriaan Huskens,
this has provided chemists with a versatile method
for creating new materials.
In their experiments, the university of Twente
researchers first made microwires with a PN junc
-
tion halfway along the wires. In the experiment,
the wires were submerged into a solution contain-
ing platinum in the dark, causing the 'P side' of
the wire to be covered in platinum. In the next
stage, silver was added to the other side in the
light. The result was a mi-
crowire with silver on the top
and platinum on the bottom.
The wires can be very valu-
able for the purpose of gen-
erating energy from sunlight
or purifying water with the
help of sunlight.
University of Twente Develops
Versatile Method for Developing
New Materials
