ATS Case Study: Improving temperature control of Automatic Test Equipment

Lab Equipment
We wrote about “Thermal Management of Testing High Power IC Devices” last week and noted that ATS’s team had been approached to invent a cooling test head for semiconductor test equipment. We thought our readers might like to hear a bit more about that project.

A major semiconductor firm focusing on the network processors approached ATS to consider how improved temperature control of test could be implemented for their existing automatic test equipment test head. ATS proposed to redesign the existing test head to allow for improved processor temperature control during the test cycle. While the project never went forward, the thermal design approach for this kind of thermal challenge is useful to consider.

Semiconductors aren’t likely to get cooler and automatic test equipment needs to be designed to handle the potential extremes in thermal states such components go through during test.

As part of ATS’s evaluation of the project, we discovered that the test head only maintained one fixed temperature and did not compensate for the power being dissipated by the device under test. During the customer’s test, the device power level changes greatly as it cycles; especially at power up the device made a very rapid ramp.

The overall purpose of the test head is to control the processor temperature to a known value with reduced variation, independent of the instantaneous power level. ATS’s proposed two different appraoches to solve the problem of the test head being now required to compensate for the power being dissipated by the device under test.

The first approach suggested was to reduce the thermal mass and decrease the latency in both heating and cooling of the processor. Reducing the thermal mass required a very detailed study on the power signature of the test cycle to anticipate the required cooling (or heating) at a given point of the cycle. ATS felt this method could offer the potential for a tighter control of processor temperatures while requiring more complication control hardware and precise understanding of each test cycle.

A second approach our team suggested was to increase the thermal mass of the system to dampen the temperature variations caused by the power level fluctuations. The increased thermal mass would help to absorb the power impulse levels while keeping the temperature relatively steady through the cycle. The advantage of this approach is that it would require less sophisticated control and monitoring hardware, and not be as process dependant.

Thermal management is a necessary evil (or obsession if you live in our world) and it has to be addressed at many different levels. And this includes the thermal management of test equipment during test.

For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.

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