Polar Toneohms are ideal tools for the
electronics production environment. Able to locate shorts quickly and
accurately on both bare and loaded PCBs,
they provide a very cost-effective means of minimizing
repair and rework of faulty PCBs that have been
identified by pass/fail testing on an ATE system.
"By introducing Polar
Toneohm 950s into our production process, we are able to
achieve maximum throughput of quality-approved boards in
our repair facility. This has proved to be a sound
economic investment for Motorola."
Barry Hayes, Production Manager,
"Its speed of operation
makes the Polar Toneohm 950 a viable and economical way
of curing ground-plane shorts."
Cyril Cooper, Test Specialist,
Design to Distribution Ltd
|Manufacturers and assemblers of
electronic printed circuit boards are constantly striving
rejects and scrap
rework time and cost
and improve quality
percentage of electronics manufacturing and in-service
defects are caused by PCB short-circuits or faulty
devices loading the circuit. Automatic pcb test equipment or
conventional fault detection techniques can be used to
diagnose the presence of shorts, but not their
In recent years, shorts
location has become more difficult due to the
and earth planes
The Toneohm 950
represents the definitive solution to all these problems.
Employing innovative Vectored Plane Stimulus techniques,
the instrument provides fast and accurate guidance to the
origin of PCB shorts. From an operator's point of view,
nothing could be easier to use - you just follow the
arrows on the instrument's front panel!
Why do you need the Toneohm
PCBs are becoming more
complex and valuable in terms of both cost and the
requirements for 100% yield in the production process.
Witness the very rapid growth in multilayer fabrication
techniques, surface-mount technology and just-in-time
manufacturing. You simply cannot afford to spend
excessive time locating faults such as short-circuits,
since this adds cost and reduces quality. Scrapping the
board results in even higher costs and unacceptable
shortfalls in production yield.
Since a significant
percentage of process faults are caused by shorts - some
independent analysts place the figure as high as 60% -
you need help in locating these with a minimum of rework.
The introduction of power and earth planes on multilayer
boards has further compounded the problem, making the
task nearly impossible with conventional fault-finding
How is the Toneohm 950 used?
The Toneohm 950 can be
used by a non-technical operator, and provides a
non-destructive means of tracing short-circuits to their
point of origin. The instrument offers four operating
modes, which cover virtually all categories of hard and
soft PCB shorts, including etch problems, solder bridges,
stuck bus lines and faulty decoupling capacitors.
In addition to
high-sensitivity Track Resistance and Track Voltage
modes, Toneohm 950s provide a completely non-invasive
means of measuring PCB track current - without requiring
you to break or cut the circuit. Employing a non-contact
current-sensing probe, the Track Current mode facilitates
easy location of Vcc-to-ground shorts, and of faults in
bus-structured boards such as backplanes and memory
banks. A backlit liquid crystal display provides clear
indication of relative measurement values, and an audio
tone enables you to walk the probes along the shorted
tracks without even looking at the instrument - the
highest tone will indicate the short.
For shorts on
multilayer PCBs with power or earth planes, the Toneohm
950 offers users a powerful fault location technique
known as Vectored Plane Stimulus.
How does Vectored Plane
The ground and power
planes of multilayer PCBs make it impossible for
conventional test tools to accurately locate the origin
of short-circuits. Polar's Vectored Plane Stimulus uses a
combination of current injection and field sensing
techniques to overcome these problems, enabling you to
rapidly home-in on the precise fault area of a board,
without removing components or applying power.
Locating shorts in
multilayer PCBs could not be easier - you simply follow
the arrows! After attaching stimulus leads to the shorted
plane at or near the corners of the PCB, and a reference
probe to the shorted network, you merely touch the
tracing probe on any node of the failing network. The
four-quadrant LED display on the Toneohm 950 immediately
indicates the direction in which you should probe to find
Three or four probing
operations are generally sufficient to bring you within 2
or 3mm of the short, at which point all four LEDs
illuminate to confirm success. The fault-tracing process
is accompanied by an audio tone which rises in frequency
as the short is approached, together with a digital
display of relative distance which enables extremely
accurate shorts location.