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At telecommunications equipment manufacturer, General Bandwidth,
tight production schedules make rapid thermal prototyping
imperative. Delays can force board layout engineers to proceed
without thermal data in order to avoid schedule slips, a costly
decision if problems surface later forcing a redesign.
To perform fast design iterations, General Bandwidth
simplifies its thermal
models. Rather than pinpoint temperatures to within a couple degrees,
General Bandwidth quickly identifies preferred component and air
mover locations, along with some placement options for maximum
layout flexibility. To further speed calculations, initial models
are analyzed for parameter sensitivity using a minimum number of
grid cells. As models are refined, the number of cells is increased.
A typical simplified model, takes about an hour to run. The simplified models
demonstrate a strong correlation with test results; for example,
a change in chip placement or airflow, that produces a 10% change
in the Coolit model temperature, will produce a 10% change in
measured results.
There are three to four circuit boards in development at any
one time. The designs are evolutionary, so that test results
from one generation can be used to refine assumptions for
follow-on modules. All components are assumed to operate at
maximum power consumption, to guarantee a conservative estimate.
Prior to Coolit, General Bandwidth depended on an outside
consultant for its thermal analyses. But the rapid development pace
soon created an information bottleneck between the organizations.
It took too long to cycle modeling information and test data back
and forth.
Once the decision was made to do thermal modeling in-house, General
Bandwidth reviewed its options, including the CFD package used by its
consultants---a choice that would have made porting of legacy information
relatively easily. After a thorough evaluation, Coolit was selected for
its unparalleled speed and ease-of-use.
Ramp up for the three member thermal team occurred rapidly; the
mechanical engineer was creating models in a day and, within a week,
he had three boards ready for layout. The other two team members,
who had never used CFD, took two days to get up to speed. Throughout,
Daat Technical Support was there to help as required.
Since adopting Coolit for its in-house use, General Bandwidth has
significantly shortened its thermal prototyping schedules and saved
thousands of dollars in consulting fees. The Coolit graphics have
made it easy for thermal engineers to communicate recommendations to
non-specialists, who can view in 3D full color and with animation, the
impact of various design decisions on thermal performance. In one
instance, Coolit proved that relying on intuition can be dangerous.
A stack of three components, that should have shown increasing temperature
with distance from the fan, instead had a hot spot in the middle of the
stack. The culprit proved to be an unexpected airflow pattern that
disrupted the seemingly logical temperature variation.
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