Tag Archives: Kaveh Azar

Join ATS for Live Liquid Cooling Webinar

Advanced Thermal Solutions, Inc. (ATS) is hosting a series of monthly, online webinars covering different aspects of the thermal management of electronics. This month’s webinar will be held on Thursday, Sept. 27 from 2-3 p.m. ET and will cover the design and deployment of liquid cold plates in electronics systems. Learn more and register at https://qats.com/Training/Webinars.

Liquid Crystal Thermography Provides Precise Heat Maps

It is critical for the engineers to accurately determine temperature of a design, whether it is at the chip, component, board, or system level, to ensure that the design will function properly and maintain its optimal performance over its expected lifetime and meet its specified mean time between failures (MTBF). Thermal management of electronics is unarguably a critical component of the design phase.

To optimize thermal management, it is also critical to get an accurate picture of the heat distribution across a device or a board. One of the most precise methods for mapping temperature is liquid crystal thermography (LCT). LCT uses thermochromic liquid crystals (TLC) to give engineers a visual representation of the heat distribution based on the changing colors of the TLC when heated.

Liquid Crystal Thermogrpahy

Liquid crystal thermography systems give a visual representation of the heat on a device, board, or system using thermochromic liquid crystals, high-resolution cameras, and an LED light source. (Advanced Thermal Solutions, Inc.)

LCT technology has been around since the 1950s and has been used in the electronics industry since the 1980s. In 1975, researchers published a review of LCT and it applications in the study of convective heat transfer that determined the method provided “both qualitative and quantitative heat transfer and fluid flow information to be obtained on heated objects placed in forced convection environments.” [1]

The authors added, “In addition to yielding precise quantitative heat transfer information, the liquid crystal thermographic technique afforded the opportunity to visually observe the effects of flow separation, the separation bubble region, the turbulent boundary layer, and the turbulent wake on the surface temperature of the heated cylinder.”

What are Thermochromic Liquid Crystals?

Thermochromic liquid crystals are the key to the LCT process. Rather than changing from a solid to a liquid when heated, TLC have an intermediate liquid-crystal phase and the temperature in which this phase-change takes place is precisely defined depending on the composition of the crystals. The phase-change causes the TLC, which starts as transparent, to reflect different wavelengths of light, represented visually as different colors.

Liquid Crystal Thermography

TLC readings using thermVIEW Lite software from ATS. The TLC shows up as different colors depending on the heat applied, while the software is calibrated to give precise temperature readings. (Advanced Thermal Solutions, Inc.)

As explained by Dr. Bahman Tavassoli in an article for Laser Focus World, “Normally clear or slightly milky in appearance, liquid crystals change in appearance over a narrow range of temperature, called the color-play interval. This is the interval between the first (red) and last (blue) reflection. The displayed color is red at the low-temperature margin of the color-play interval and blue at the high end. Within the color-play interval, the colors change smoothly from red to blue as a function of rising temperature, with blue light corresponding to the clearing-point temperature.” [2]

To visualize the temperature response of the TLC, a bright and stable white light is required to remove the infrared and ultraviolet radiation from the output spectrum. Tavassoli explained, “Any IR energy present in the incident light spectrum will cause unwanted radiant heating of the test surface. Exposure to UV radiation can cause rapid deterioration of the TLC surface, which will result in unreliable color-temperature responses.”

Temperature ranges for the TLC material are established by the manufacturers. Narrow-band TLC have bandwidths below 1-2°C, while wide-band TLC range between 5-20°C. TLC are typically designated by a two-color/temperature system. For instance, R35C5W would indicate that the TLC would show up as red starting at 35°C and that the blue start temperature would be 5°C above the red, allowing engineers to see the estimated bandwith of the TLC.

TLC are inherently oily, and their thermal performance degrades from exposure to chemicals and UV radiation, so manufacturers have developed microencapsulation or polymer dispersion methods to make the materials easier to use in laboratory settings. Microencapsulation provides high resistance to contamination, but the polymer dispersion method provides a more brilliant color response. [3]

How do you use Liquid Crystal Thermography systems?

To obtain the most accurate results from LCT, a smooth and contamination-free surface is important. Test surfaces and calibration tools should be cleaned with alcohol, if possible, and dried before the process begins. A thin and uniform coating of black paint is applied to the test surface and dried using a hot air gun at low temperature. Once the surface is dry, the TLC materials can be applied to the test surface. [4]

A bright, stable, white light source is required to obtain an accurate reflected light intensity from the TLC-coated surface. As explained by Dr. Kaveh Azar in an introduction to LCT techniques, “Consistent light source settings and lighting-viewing arrangements between calibration and actual testing are essential to minimize color-temperature interpretation errors.”

Calibration is the key to using LCT. According to Dr. Tavossoli, the system for calibrating TLC is similar to calibrating the voltage-temperature response of a thermocouple. TLC is subjected to known temperature levels and the response is recorded with a color-sensitive camera. The response is recorded at different temperature levels on a test surface and the system develops calibration files that can later be used to interpret the response of TLC on the device being studied.

The following graph shows the relationship between temperature and color of a range of TLC:

Liquid Crystal Thermography

While TLC response is visible to the naked eye, the LTC system uses a high-resolution, solid-state color camera and calibrated software to more precisely determine the temperature.

Advanced Thermal Solutions, Inc. (ATS) has recently added to its line of LCT systems to provide a cost-effective tool for temperature mapping studies. tvLYT™ is accurate, easy to assemble, and easy to use. It comes in a portable case containing the arm, high-resolution macroscopic optic camera, LED light source, black paint, and TLC material for the required temperature range. tvLYT™ can be quickly connected to a computer through a USB and uses thermVIEW™ Lite software (downloadable on the ATS website) to calibrate the readings and provide precise results.

Liquid Crystal Thermography

The tvLYT™ liquid crystal thermography system from ATS provides highly accurate temperature mapping capability using TLC. (Advanced Thermal Solutions, Inc.)

For more information about tvLYT™, visit https://www.qats.com/Products/Instruments/Surface-Thermography/tvLYT.

What are the benefits of LCT?

There are several techniques for measuring temperature across a system, including the use of thermocouples and resistance thermometers. These are common techniques used in labs across the world, but there are challenges and limitations to that method.

As one report noted, “Traditional techniques employing sensors such as thermocouples and resistance thermometers can measure temperature at individual locations. Hence, a large number of sensors are required for complete mapping of the surface. Since physical sensors occupy space, the measurements are to be interpreted as spatial averages. This route may prove to be disadvantageous in regions of localized peaks and valleys of heat transfer. Liquid crystal thermography proves to be useful under these circumstances.” [5]

The tools for thermal imaging, which visualize IR emissions to show heat patterns, continue to improve, seemingly by the day, and several companies have released cameras that can be attached to a mobile phone to improve the mobility and accessibility of thermal imaging. [6] IR cameras can give a quick visualization of the heat emitted from a device and are excellent tools for finding hot spots at the system level, but they lack the precise temperature readings that LCT captures and accuracy counts in thermal management.

Comparison of LCT and IR systems. [4]

LCT gives engineers flexibility. It can be used in to measure temperature across micron-level electronic circuits or large-scale gas turbines. LCT is used in a wide range of applications from detecting lamination in composite polymer materials [7] to studying turbulent boundary layers in a water tunnel [8] to biomedical studies [9] such as testing for skin cancer, breast cancer, blood circulation, and more.

Because precision is the most important benefit to using LCT for temperature mapping studies, ATS has offered four free calibrations during the first year after purchasing tvLYT™ and also lifetime technical support.

For more information about ATS liquid crystal thermography systems, or thermochromic liquid crystal materials, visit https://www.qats.com/Products/Instruments/Surface-Thermography.

If you have questions about any ATS product or its consulting and design surfaces, contact ATS at ats-hq@qats.com.

1. http://heattransfer.asmedigitalcollection.asme.org/article.aspx?articleid=1436225
2. https://www.laserfocusworld.com/articles/print/volume-41/issue-12/features/thermal-imaging-liquid-crystal-thermography-characterizes-heat-issues.html
3. https://www.electronics-cooling.com/1995/10/making-surface-temperature-measurements-using-liquid-crystal-thermography/#
4. https://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0201b.pdf
5. http://www.nptel.ac.in/courses/112104039/pdf_version/lecture35.pdf
6. https://www.thermal.com/compact-series.html
7. https://onlinelibrary.wiley.com/doi/pdf/10.1002/pc.20453
8. https://www.sciencedirect.com/science/article/pii/S0924424715300224
9. http://zm8pc.ippt.gov.pl/papers/JCPT_2014012610120554.pdf

ATS Hosting Thermal Management Webinars

Advanced Thermal Solutions, Inc. (ATS) has announced a series of monthly, online webinars covering different aspects of the thermal management of electronics. The webinars are presented by Dr. Kaveh Azar and begin on Thursday, July 26 at 1:00 p.m. Learn more and register here https://qats.com/Training/Webinars.

Thermal Management Webinars

ATS Provides LED Thermal Solution for Big Game

When the big game kicks off on Sunday night, the Patriots will not be the only team from New England shining bright at U.S. Bank Stadium in Minneapolis, Minn. Advanced Thermal Solutions, Inc. (ATS) will also be represented, although not on the gridiron, but rather helping to shine a spotlight on the action on the field.

LED Thermal Solution

Ephesus LED lighting solutions, with ATS thermal management design, will be used in the upcoming Super Bowl at U.S. Bank Stadium in Minneapolis.

In 2015, Ephesus Lighting (Syracuse, N.Y.) was chosen to provide LED lighting solutions for the Minnesota Vikings’ new stadium. The Ephesus system allows for greater control and adjustment, whether responding to the amount of sunlight in the stadium or the light’s color temperature (Ephesus recommends a medium color temperature for football), and does not require a 15-minute window for reaching full brightness like typical stadium lighting. It will also provide energy savings of as much as 75 percent.

“We take the light and purposefully model around obstacles that are on the field, players, the balls, so it’s like being in a portrait studio with lighting behind, lighting in front, and you look perfect,” Ephesus Chief Technology Officer Joe Casper said in a 2015 Vikings.com article. “We take great care of taking light from various aspects of the catwalk, and it’s being aimed to create light from 16 different directions so it gives you the appearance that you’re in a studio.”

To keep their patented LED solution cool, Ephesus partnered with ATS for a casted heat sink, which is large, rugged, and reliable. By providing the proper thermal management, ATS has helped Ephesus optimize the performance of its LED, which have now been used in two stadiums that have hosted the NFL’s championship game.

The first time LED were used was at University of Phoenix Stadium in Glendale, Ariz. when the Patriots beat the Seattle Seahawks.

For its assistance, ATS and other Ephesus partners received special thanks from the lighting company:

The casted heat sink design that ATS devised had several advantages, including a reduced part count, having the enclosure and heat sink in a single unit, and reducing the manufacturing complexity of the thermal solution. With ATS help, the lighting was able to be delivered and installed on time for the game, just as it was for the opening of the new stadium in Minneapolis.

For more information about the design that ATS delivered, read this case study with the engineers that worked on the project: https://www.qats.com/cms/2015/04/28/casting-a-light-on-led-cooling-with-die-cast-heat-sinks.

To learn more about the thermal challenges that LED present, read this article from Design World written by Dr. Kaveh Azar, founder and CEO of ATS: https://www.designworldonline.com/lighting-the-way-for-led-development/#_.

Thanks to the LED expertise of Ephesus and thermal management capabilities of ATS, fans will have a perfect view when the Patriots take the field in search of a sixth title.

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. To learn more about ATS LED products and consulting, visit https://www.qats.com/Applications/LED-Applications.

ATS holding webinar on Thermal Management of Medical Electronics

Medical Webinar

DR. Kaveh Azar, founder, CEO and President of Advanced Thermal Solutions, Inc. (ATS), will present a free webinar on “Thermal Management in Medical Electronics” on Dec. 15, 2016.

On Thursday, Jan. 26, Advanced Thermal Solutions, Inc. (ATS) will host a free, online webinar on “Thermal Management of Medical Electronics”. The hour-long webinar will begin at 2:00 p.m. and there will be 30 minutes of question and answer time after its completion.

The webinar will be presented by thermal management expert Dr. Kaveh Azar, the CEO, President and founder of ATS. Dr. Azar will speak about the unique challenges that are present in finding a thermal solution for medical electronics and the importance of including thermal management in the design process.

The object of all thermal management is to ensure that the device junction temperature, the hottest point on a semiconductor, stays below a set limit. While this is true for all electronic systems, medical electronics pose unique thermal challenges that have to be overcome to meet the junction temperature requirements.

Medical electronics could have stringent material selection. For example, copper is a common metal chosen in thermal management, but can cause irritation or a neurodegenerative condition for patients and has to be used carefully. In addition, medical electronics may have spatial constraints, such as forceps that have only 2-4 millimeters of width, which is a constrained space with very little airflow.

Other challenges presented by medical electronics include the need for constant, reliable repeatability; temperature reliability within a range; and in some cases specific FDA requirements.

Dr. Azar will address each of these issues and more. To register for the free webinar on Thursday, Jan. 26, visit http://www.qats.com/Training/Webinars.