Advanced Thermal Solutions, Inc. (ATS) has released a new thermal test instrument, the iFLOW-200, which assesses the thermal and hydraulic characteristics of cold plates in electronics cooling. It can be used to simulate a wide range of conditions to optimize a cold plate’s performance before it is commercialized or prior to its use in an actual application.
The iFLOW-200 measures coolant temperatures from 0-70°C with the high accuracy of ± 1°C. Differential pressure of the coolant in the cold plate is measured up to 103,000 Pa (15 psi), with the precise accuracy of ± 1%. Distilled water is used as the reference coolant. For test comparisons, the systems coolingVIEW software can also calculate thermal resistance and pressure drop as a function of flow rate for selected liquids.
The instrument system includes a pair of K-type thermocouples for measuring temperature changes on the cold plate surface. Temperatures are monitored on the coolingVIEW interface.
The iFLOW-200 system features easy set up and operation to save time when evaluating different cold plate models. Designed for accuracy and convenience, the iFLOW-200 simply requires setting the starting and ending coolant flow rates, and choosing the dwell time, pumping power and other parameters. These are easily done on any PC using the systemd user-friendly application program.
The iFLOW-200 system features separate controller and hydraulics enclosures with USB connections. The hydraulic package includes a fluid level indicator, coolant inlets and outlets from/to the cold plate under test, ports for surface temperature thermocouples, and a fluid cooling system for its internal heat exchanger. The iFLOW-200 is also ideal for testing alternative liquids.
ATS’ Qpedia is the official media sponsor of the 2012 coolingZONE Business and Technology Summit August 27-30 in Cambridge, MA. We sat down with Dr. Kaveh Azar who will be presenting the Pre-Summit Short Course “Thermal Measurement and Experimental Design in Electronics Cooling” and “State of the Art in Thermal Management – From Vacuum Tubes to Super Computers” as the Summit. In this interview, Dr. Azar discusses why education is so important in the electronics cooling industry and the crucial issues he will discuss at coolingZONE this August.
Qpedia:
Hi my name is Andrea and I’m coming to you from Qpedia Thermal eMagazine. Qpedia is the official media sponsor for the 2012 coolingZONE Summit in August. I’m with Dr. Kaveh Azar hoping to ask a few questions about the thermal management community in general and his upcoming short course on August 27th.
Dr. Azar:
Thank you Andrea, I’m glad to be here.
Qpedia:
Dr. Azar, you have served as an organizer, general chair, and keynote speaker at countless conferences, and have always played an active role in the thermal management community. Why do you think education is so important in this field?
Dr. Azar:
Andrea this is a very good and insightful question. Thermal management obviously as we all know is a critical juncture point for the successful launch of any electronics cooling product. Either we are new to the field or have come from school, when I say new to the field it could have been a seasoned engineer that comes to an electronics company with a mechanically engineering background or electrically engineering background and has given the responsibility of thermal managing of electronics systems. The unfortunate part of it is we are not really exposed to a specific field in electronics cooling. Not that there is new heat transfer or fluid dynamics, we are all exposed to the fundamentals in our graduate studies, but when we get to electronics cooling there are some very unique parameters that make it very difficult. These stem from awkward geometry, multiple materials, multiplicity of heat sources on a board and as a result of it some of the traditional problems we have seen in our thermal management classes in school that we have been exposed to in school may not necessarily apply. Therefore, those of us who have gone through this education by the school of hard knocks have being have an obligation to come back and education people who are coming to the field new, weather from school or as an engineer in a role with new responsibilities. We have to share our experiences and exposures to the people that we have had in electronics cooling to those that are going to be involved. Those are the little nuggets that make the problem much easier to solve than going just going to a heat transfer or thermodynamics class. So the problem is very difficult to solve and education, especially education with experience is very important to share and help the new people coming into the field solve their thermal problems.
Qpedia:
Thank you. On August 27th, you will be giving a one day short course on “Thermal Measurement and Experimental Design in Electronic Systems”. Could you please give a short overview on what you will be presenting?
Dr. Azar:
Absolutely. Here on this board, just to give an example of why a course like this is of value to any thermal or mechanical engineer in electronics cooling, if you look at this board, you see a multiplicity of geometries, power sources, different packaging, plastic molded packages, metal packages, connectors, the way heat sink attach with clips and as a thermal engineer I have the responsibility to come back and see if this device is going to be functional in the application this board will reside. This board could be sitting vertical, horizontal, or faced down depending on what the configuration is. We have all of these very powerful computational analysis tools but at the end of the day we have to verify our solution. So you have run your CFD simulation, you have done your analytical modeling, but now you need to know whether it is correct or not. To be able to calculate the temperature of this device, I need to know what the air and temperature velocity are and possibly the pressure drop. So in this course we are going to look at the component, board, and system level for how to measure thermal parameters. This includes: temperature, velocity, pressure, and heat flux and also learning about flow visualization which is very important.
Qpedia:
Thank you. Why is thermal measurement so important?
Dr. Azar:
At the end of the day, we have to verify. There is nothing like measurement. It is dangerous to produce data, but at the end of the day people believe data verses simulation and modeling. And when we do measurement often times it is very difficult to do the simulation and we don’t have an exact answer as to what is happening. Assume for instance, for the sake of discussion this is a telecommunications board, and we have multiple boards sitting in an environment or even a single board facing down or up in a natural convection or mild force convection. These are very difficult problems especially with the complex geometry that you see and I need to verify my simulation. I have these powerful tools that I have purchased , I have my answer, I want to send my product out but I need to see whether my answers are correct or not. Because if I don’t have a correct answer, I could jump into a whole different cooling capacity that I could cool this with a simple fan and heat sink. If my simulation is wrong, if I didn’t set the correct boundary conditions, if I didn’t verify my answer, where the measurement will come into the picture to help, it’s going to cause me to go consider a higher capacity cooling system and a higher capacity cooling system will cost more. It is a very competitive market and we want to make sure that every aspect of our solution is minimized as far is cost is concerned so we can get our products out to the market as cost effective as possible and as reliable obviously.
Qpedia:
Thank you. Can you tell us a little about the live demo you plan on giving?
Dr. Azar
Yes, Andrea. As some of you may know, we have developed a whole host of thermal test instruments at ATS. We use these on a regular basis for characterization and consulting work that we do with a variety of clients and I have always believed that it is of immense value to see an experiment in progress. I can sit here and talk about hot wire anemometers, laser doppler velocimetery, heat flux gauges, etc. but when you see it in operation you have a totally different appreciation for some of the challenges we have to face in order to collect good data. In the previous question I mentioned that people believe data and they don’t believe analysis. So the data that you generate has to be as accurate as possible. The live demo will show you the challenges and the issues we confront when we have to do a clean measurement. You can see how this equipment is used, for someone who has never done this before it may be very difficult to imagine what a hot wire anemometer is, how it works, and what the challenges are. Granted it’s a sensor but there are errors associate in that and when you put it in an experiment you can see where the errors are and how to eliminate it when you do a measurement. So the demo will encompass all of this and give an accurate description of measurement is all about.
Qpedia:
Thank you. What do you hope that attendees to take away from this short course?
Dr. Azar:
My greatest hope, first of all, is that they get a good understanding of what measurement is all about. Secondly, that they get a good understanding that measurement is not a game. It is a very detailed process. For me to be a good experimentalist I have to be a good analyst and I hope to convey this very strongly to the people who participate. Last but certainly not least is for people to understand the tools that are available for measurement so when you go back to your offices and you have to conduct a measurement or you see data being collected, you have a chance of judging what to look for, what the pertinent parameters are so you select the right instrument, place it in the right location, and when you look at the data you question the validity of the data even though you may have put it together yourself as you would question your results from analysis and simulation. If those three items are accomplished, which they have been in the past and hopefully we can again, then I think we are going to have a very successful course for our participants and obviously very gratifying for those of us who are giving the course.
Qpedia:
I agree! Dr. Azar thank you very much for your time. We look forward to seeing you at the 2012 coolingZONE Summit, August 27-30, in Cambridge, Massachusetts.
Dr. Azar:
Thank you Andrea for giving me the opportunity to talk with you and the audience.
Visit www.coolingzone.com to see the full list of topics, short courses, exhibitors, and speakers that will be at the 2012 Summit.
Register by July 31, 2012 to receive a 15% discount. Contact coolingZONE at cz-[email protected] or 508-329-2021.
Today we conclude our three part series, “Sensors for Temperature Measurement and Their Application”. We’ll be talking about the last three sensor types: Infrared or Radiation, Fluorescent Detector and Liquid Crystal. To catch up on the series, you can click to Part 1 of our series or click over to Part 2 of our series.
4. Infrared Thermography
Infrared thermography works on the basis of the IR waves emitted from a heated surface. The infrared system captures the waves, and based on internal calibration converts them into temperature. The following are required for IR-based measurements:
Infrared imaging system — The market offers a broad range, but a worthy system starts at around $30-70k. For IR microscopy (down to 5mm only-lower limit of IR wave-length), the system starts at $180k.
Signal processing equipment.
Knowledge of emissivity if the test specimen must be coated with a known emissivity material.
Calibration.
Figures 5a and 5b show a typical IR image of heat-emitting surfaces:
5a shows and IR image of a PCB in forced convection air flow[3]
5b shows and IR image of a PCB in forced natural convection air flow[3]
The following points are noteworthy when using an IR camera for temperature measurement:
Application accuracy is a function of emissivity.
The measurement situation must duplicate the actual environment, as far as air velocity, temperature and air flow distribution are concerned.
The IR camera is sensitive to reflected radiation.
Carbon dioxide and water vapor absorb significant energy and may cause significant error.
In an electronics application, surfaces typically have different emissivities thus, one must make the emissivity uniform before measurement of known emissivity (black paint or powder).
In most IR equipment, the temperature readout is the average over an area. Therefore, temperature peaks may be ignored as the result of integration. To remedy the situation, better IR optics must be used to reduce the area where integration occurs.
5. Optical Probes
Optical sensors are light-emitting devices that illuminate the test body with source radiation, and can detect reflected radiation, or simulated radiation such as fluorescence. Although not broadly used, optical probes are used at the die or component level. Figure 6 shows one such a probe.
Figure 6. Optical Probe For Surface Temperature Measurement The Probe Either Touches The Surface Or Captures The Reflected light From A Fluorescent Treated Surface.
6. Liquid Crystal Thermography
LC thermography works on the basis of visible light reflected from a surface treated with the LC material. The system captures the reflected wavelengths, and based on internal calibration, converts them into temperatures. Liquid crystals (LCs) are cholesteric materials. When applied to a heated surface they realign and reflect light at a different wavelength. The reflected light shows the standard colors seen in a rainbow. Figure 7 shows the application of LCs on an IC.
Figure 7. Color display of liquid crystal applied on an IC. Blue reveals the circuit’s hottest point, and black shows that the temperature is outside the range of the crystal material [3].
The following are salient features of LC material:
Liquid crystals are organic compounds that can be poured like a liquid, yet reflect light like a crystal.
Changes in LC optical properties can be produced by externally applied fields (e.g., electrical, magnetic, and thermal).
Cholesteric liquid crystals progressively exhibit all colors of the visible spectrum when heated over their event temperature range.
Width and placement of the event temperature range can be controlled by selecting and mixing the appropriate liquid crystals.
Liquid crystals are commercially available with event temperatures ranging from below 0oC to 160oC, with spans ranging from 1 to 50oC.
An LC thermography system such as the one shown in Figure 8 can provide a very effective temperature-mapping system.
Figure 8: The thermVIEW System for Macro and Microscopic (down to 1um) Surface Temperature Measurement[4]
Figure 9 shows a typical result of LC thermography at die level:
Figure 9. Temperature distribution across a memory chip (5 x 5 mm) at Tambient = 25oC, as shown using Liquid Crystal Thermography [3].
Like any other system for temperature measurement, LC thermography offers distinct advantages and disadvantages. One salient advantage of LC thermography is that its not dependent on surface emissivity. A second is that at micron and submicron levels, though not a trivial task, LC thermography allows easier and less costly temperature measurements while enabling 1µm or smaller spatial resolution. One disadvantage of LC thermography is that it is not a pick-up-and-measure system like IR. One must apply the calibrated liquid crystal material to a surface in order to perform the measurement. But, this is similar to the IR system, in that you need to make the surface emissivity uniform if the measured surface has multi-emissivity (e.g., a die or PCB).
In this article, we reviewed six different probes/techniques for temperature measurement. It would be a missed opportunity not to include a word on calibration. Irrespective of the types of measurement and sensors one uses, calibration is of utmost importance. Pay special attention to the calibration process and ensure that the sensors are properly calibrated. Further, one needs to ensure that the chosen sensor is suitable for the type of measurement. As Prof. Frank White states in his Viscous Flow book, Bad data is worse than no data at all [5].
If you are in need of sensors for thermal measurement, click now to ATS’ sensor family. To learn more about ATS ‘ thermVIEW liquid crystal thermal analysis system, click to thermVIEW System. You can also email or call us with your questions on temperature measurement and one of our engineers will be happy to help you. Email us at [email protected] or call us at 781-769-2800.
Today we start a three part series on on Temperature Measurement and Their Application. There is an IT axiom that says, “garbage in, garbage out” and no where is that more true than in thermal analysis. If you measure your data incorrectly, you’ll have no chance of getting the data you need to design the best thermal management solution for your application.
In todays market, it is very rare to see electronic equipment that has not undergone extensive thermal evaluation, either by measurement or simulation. Inevitably, the temperature of the device junction or case, or the enclosure, has been measured to ensure that the system will operate to its intended specifications. A quick look at the equations associated with stress in a lead wire, and with the acceleration factor used in reliability calculations, will show why temperature plays such an important role in electronics equipment [1].
Equations 1 and 2 clearly demonstrate the linear and exponential relationships that temperature has in the operation of the electronic components. Concurrently, simulation tools are used extensively in todays thermal design. But, due to the complexity of the electronics packaging and composite nature of the materials used, the simulation data must be verified in order to ensure reliable data is obtained. In this article, we present different sensors and their application domains in electronics thermal management.
Table 1 shows six primary sensors used in temperature measurement:
Table 1. Standard Temperature Transducers [2]
In part 2 of our three part series, we’ll start consider each sensor in detail, focusing on the resistor thermometer, thermocouple and diode transistor.
References:
1. Klinger, D., Nakada, Y., Menendez, M., AT&T Reliability Manual,
Van Nostrand Reinhold, 1990.
2. Azar, K., Thermal Measurement in Electronics Cooling, CRC Press,
1997.
3. Advanced Thermal Solutions, Inc., Tutorial Series, Principles of
Temperature Measurement.
4. thermVIEW System, product of Advanced Thermal Solutions, Inc.
5. White, F., Viscous Fluid Flow, McGraw-Hill, 3rd Ed., 2005.
If you are in need of sensors for thermal measurement, click now to ATS’ sensor family. Including our industry leading Candlestick Sensor.You can also email or call us with your questions on temperature measurement and one of our engineers will be happy to help you. Email us at [email protected] or call us at 781-769-2800.
The eATVS family of instruments are best sellers for us. And no wonder. They are inexpensive, accurate and reliable. The software, stageVIEW, completely automates the data gathering process, freeing your hands up to do other tasks. Our latest video not only demonstrates our eATVS instruments but shows a bit how to use them.
