Message Board Thread - "IR imaging of PCAs"

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IR imaging of PCAs AMP 4/6/2004
We have recently purchased an IR camera to use for thermal imaging of our products and PCAs during the development cycle in order to understand the hot spots and to aid in making product improvements. I have done some imaging of a couple PCAs during operation, and we have used the results to focus in on what appear to be the hot spots. Since I am new to IR and thermal imaging, I have been doing a lot of research to understand this technology and what I need to consider when taking and analyzing the images. Of course, everything I read states that having correct emissivity values is critical. With the imaging I have done, I have assumed a constant emissivity across the PCA of 0.98, but I do not think that is correct to assume. Most components are colored a flat black, of course, so they will have high emissivity. I did an experiment where I placed a PCA in a temperature chamber, raised the temperature and let the PCA stabilize, then took an image of it. From knowing the temperature, I calculated the emissivity values of several parts; they all are around 0.95. My question is, is anyone else using IR for a similar purpose, and if so, what do you do about emissivity values? Any suggestions would be appreciated. Thank you.
 
Re:IR imaging of PCAs Thermoimagen 4/9/2004
hi ..

sorry, what is a "PCA" ?..
 
Re:IR imaging of PCAs JKEngineer 4/11/2004
Ditto on "what is a PCA?"

Also - using an oven to heat the device and then measure its emissivity will give ambiguous results unless the surface measured is removed from the oven's influence. If you image the device while still in the oven, the background temperature and the object temperature are essentially the same and you cannot derive the emissivity.
Jack
Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

4011 Hillman Ave
Bronx, NY 10463

718-884-6644
866-884-6644 toll free
212-214-0919 fax and voice mail

JKEngineer@aol.com or JKEngineer@KleinfeldTechnical.com
come see what we can do for you: http://www.KleinfeldTechnical.com
 
Re:IR imaging of PCAs AMP 4/12/2004
PCA is Printed Circuit Assembly. Basically a loaded printed circuit board. I guess I don't understand why the board would need to be removed from the chamber. If I do that, the temperature of the board will drop to an unknown level. Is there any better way to determine emissivity?
 
Re:IR imaging of PCAs Thermoimagen 4/12/2004
well AMP

lets to think in termally facts ..

if you add heat to the PCA, i will assume that after a while, everything inside the temperature chamber will be at the same temperature, is my observation ok?..

So, that's the main reason to inspect outside the temperature Chamber.

Remember that: to have a good image you will need good termal contrast, cool behind hot at front, or backwards. otherwise you image will be not clear to analize.

Is like when you inspect a Load center that has been turned off for hours or days and the ambient temperature is the same at all the breakers and wires.

regards
 
Re:IR imaging of PCAs JKEngineer 4/15/2004
AMP -
Examine the equation approximating the radiation the camera receives:

Tcamera= e*Tobject + (1-e)*Tbackground

where I have ignored transmission and supersimplified the terms. (took out Stefan-Boltzman and fourth power)

Rearrange to solve for e:

e=(Tcamera-Tbackground)/(Tobject-Tbackground)

If the background T is the same as the object T, as it would be if the object surface is still inside the oven and still seeing the oven as the background T, then you cannot solve for e.

Agema used to enable your type of study in their 900 series camera and software. They recommended using an open topped box for the heating environment driven by hot air. The face of the board looke up at the ceiling, which was at room T. They recommended two measurements to fit the curve -- if I remember correctly at about 10 and 20C above room T.

If you would like more substantial help, including help in setting up your program, contact me directly.

Jack
Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

4011 Hillman Ave
Bronx, NY 10463

718-884-6644
866-884-6644 toll free
212-214-0919 fax and voice mail

JKEngineer@aol.com or JKEngineer@KleinfeldTechnical.com
come see what we can do for you: http://www.KleinfeldTechnical.com
 
Re:IR imaging of PCAs Gary Orlove 4/15/2004
Thanks Jack for your explanation.

Below are two photos of the emissivity measurement apparatus. The top image shows the apparatus closed during the heating and equilibration of the circuit board. The bottom image shows the top cover open for the infrared inspection and measurement. Because you want everything to be as isothermal on the PCB as possible, this part of the process needs to be performed quickly.

Gary Orlove
Infrared Training Center
 
Re:IR imaging of PCAs JKEngineer 4/16/2004
You're welcome Gary.

Neat apparatus, I had not seen it before. The system I had described to me at an Agema users group meeting hosted by Rotec in Peabody, MA sounded like a cardboard box with hot air fans. Yours is much nicer!

Bo Wallen was at that meeting, and I think he was the one that presented it. The software, I think Researcher, was actually configured to accept a set of different temperature images and calculate the emissivity for each point on the board. Unfortunately, I think the capability to do this automatically has been lost from the software.

If I am right, it's a pity. If I am not -- PLEASE correct me. If I am right -- would FLIR consider reinstating it?

Jack
Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

4011 Hillman Ave
Bronx, NY 10463

718-884-6644
866-884-6644 toll free
212-214-0919 fax and voice mail

JKEngineer@aol.com or JKEngineer@KleinfeldTechnical.com
come see what we can do for you: http://www.KleinfeldTechnical.com
 
Re:IR imaging of PCAs Gary Orlove 4/16/2004
This device was built in Sweden and I wouldn't be surprised if Bo designed it. Notice the low emissivity sides to avoid spurious radiation!

The program you are referring to is called Equal (the Inframetrics version was called CirPass), and Equal is no longer available, and it is a pity.

I have brought this up before, but the impression is that there is little demand for software of this type. Let's here from you users out there if there is a demand!

Gary Orlove
Infrared Training Center
 
Re:IR imaging of PCAs AMP 5/28/2004
Gary, I am interested in finding out more about the emissivity measurement boxes. I had read about these before, but do not know who makes them. Who makes them? If you have any contacts, please let me know. Thanks!
 
Re:IR imaging of PCAs Thermasearch 6/2/2004
You might want to contact Bill Barron senior at: wbarronsr@williamsonir.com

Bills company, Williamson IR produces relatively inexpensive solutions to measuring E and providing very accurate temps, providing both in clean to harsh environments. They use two or more wavelengths viewed from the same instrument to cut through the clutter and errors.

Good Luck,
Mike
 


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