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liquid flow to and from the To achieve the desired thermal dissipation
DUT vertically, a liquid- at test, while providing a reliable solution
based thermal head can for their users, engineering teams must
provide significant cooling work closely with their socket vendors.
while staying inside the x/ Thermal requirements must be clearly
y profile across the PCB documented, and detailed simulations of
compared to an air-based mechanical, electrical – and now thermal –
solution. Such a liquid- performance must be completed. For many
cooled thermal lid will 300W – 500W devices, both air and liquid
have hoses attached that cooling can be considered. The choice of
must be managed, but these which solution to pursue will depend very
can be much lighter and heavily on the requirements of the end
easier to handle than a heat users. Test engineering hardware teams
pipe design with a large, must stay well informed about their users’
heavy heat sink attached. requirements and make critical tradeoffs
Management of the liquid when providing design guidance to their
hoses has not proven to be socket vendors. In the world of these
a major issue – in general, power-hungry chips, effective test socket
the hoses are lightweight thermal design is a critical element to
and flexible, so a simple ensure on-time design release.
cable-type management
Figure 7: Thermal simulation of a liquid cooled test socket lid for a 500W
TDP device using a 0.75gpm flow rate. system will suffice. Acknowledgement
In addition to providing This article is based on materials
maximum cooling, the originally presented at the MEPTEC “Too
lower z-axis profile of a Hot to Test” event in February, 2021.
liquid-based lid can enable
the PCB to be integrated References
i n t o a f u l l s y s t e m 1. Public disclosure by NVIDIA of 54B
environment (such as a transistors, https://www.nvidia.com/
server rack) while in use. en-us/data-center/nvidia-ampere-
This can help engineering gpu-architecture/
teams to gather valuable 2. “NVIDIA_GeForce_GTX_780_
real-world performance PCB-Front” by https://commons.
data at the full system level wikimedia.org/wiki/User:James086
across multiple DUTs in a i s l i c e n s e d u n d e r h t t p s :/ /
system. We are currently creativecommons.org/licenses/
partnering with leading- by/2.0/deed.en
edge networking providers 3. Tom’s Hardware article, “Micron
to i nteg r ate t her mal R e v e a l s G D DR 6 X D e t a i l s :
solutions into motherboards T he Fut u re of Memor y, or a
that will be loaded into rack Proprietary DRAM?” https://www.
Figure 8: Thermal simulation using flow dynamics to analyze the
effectiveness of liquid cooling above the DUT in a test socket lid. servers to test full-stack tomshardware.com/news/micron-
real-world testing. reveals-gddr6x-details-the-future-of-
purge functionality in their lids to prevent memory-or-a-proprietary-dram
condensation and/or icing. Summary 4. Q. Nguyen, T. Wooden, MEPTEC
From a use-model standpoint, one of the For testing advanced compute and “Too Hot to Test” presentation, Feb
major advantages of a liquid-cooled solution networking ICs, the co-design of PCB 2021, slide #6, https://events.meptec.
is the reduced size of the thermal head that hardware, the test socket, and the thermal org/too-hot-to-test-2021/
attaches to the socket lid. By directing the head have become a critical collaboration.

Biographies
Rick Marshall is Global Market Development Director, Semiconductor Test, at Smiths Interconnect,
Milpitas, CA. He has held sales and management positions at leading ATE, probe card, test socket, and software
companies. Rick has over 25 years of experience in the fabless/OSAT semiconductor test market, including 3
years based in Asia. He holds a BA from Stanford U. Email: rick.marshall@smithsinterconnect.com

Quynh Nguyen is a Mechanical Engineer at Smiths Interconnect, Milpitas, CA. She holds a BS degree in
Mechanical Engineering from San Jose State U., with a major in Technical Design and a minor in Thermal. She
has more than 15 years of experience in the semiconductor test industry.

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