Message Board Thread - "Need option to painting electronics on boards"

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Need option to painting electronics on boards Tom Hryhorysak 10/18/2004
We have been using flat black paint to prep boards prior to performing IR scan but concerns have been raised regarding potential damage to the small traces on the board. There was an article from IBM on the FLIR website about using a 3M window film in place of paint. Has anyone had any experience with such a technique and are there other options? I do not want to dust, paint or otherwise coat the electronics. Any help is much appreciated.
 
Re:Need option to painting electronics on boards lapster 11/3/2004
We have the same concern. Anyone have any tips?

Thanks
 
Re:Need option to painting electronics on boards AMP 11/3/2004
I am interested in this also. I recently tried paining a silver component with flat paint; it didn't work very well, and I was concerned about the paint getting hot. Where is the article from IBM located?
 
Re:Need option to painting electronics on boards JEB2 11/4/2004
We've painted IC's and PCB's w/ flat black paint too but didn't find it to be a problem. As an alternative, you may be able to use a Germanium Window from Edmund Industrial Optics, but depending on the size of your pcb / substrate / IC , cost may be a factor. I purchased a 12.7mm (approx .5") dia Ge window recently to scan de-capped IC's for temp characterization with and without overmold compound. It cost $126.00. (A 50.8mm costs $425.00). Quoting from Edmunds'
"Germanium is typically used in thermal imaging and FLIR applications. It has proved to be most useful as a window or lens mat'l in the 1.6 - 18 micrometer region for semiconductor substrate applications". Good luck !
 
Re:Need option to painting electronics on boards AMP 12/1/2004
In the most recent imaging I did of a PC assembly, instead of painting the silver components, I put a small white label on them. I was able to see them in the image and get what I believe is an accurate temperature reading. Has anyone else tried this? Does anyone see any problems with what I am trying?
 
Re:Need option to painting electronics on boards JKEngineer 12/2/2004
In general anything you do to a surface to make it a viable area for IR readings will affect the surface temperature. For example, if the surface is low emissivity and is over a 200F body (interior)that is producing the heat at some fixed power level, it will lose heat primarily by convection and come to some steady state temperature governed by the heat loss. If the surface is then modified, with paint, a label, or anything else to give a high emissivity, its temperature will change. This is often ignored, but can be significant. The change is caused by the increase in radiative transfer of the higher emissivity, but is also affected by a new convective transfer rate due to the change, and the insulative effect of whatever is put on the surface.

Heat transfer calculations can be performed to estimate the "true" temperature of the surface, i.e., the temperature before us thermographers start playing with it to make it readable. The approach would need as a starting point the emissivities as is and as modified, the temperature measured as modified, the properties of the material applied. Additional information might also be helpful.

If any of you are doing these measurements and have sufficient need for accuracy that these errors are of concern, I would be glad to provide this type of analysis for you.
Jack
Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

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
 
Jack, you inadvertantly just addressed an inverse problem Scott Willits 12/3/2004
that I've been discussing with ITC's Joe DeMonte over the last few days.

I've got a client operating a large rotary kiln with a heavily oxidized steel outer surface. Assuming E around 0.95, I get readings anywhere from 300F to beyond the capability of my camera to measure in areas where there's obvious refractory damage.

I'd like to suggest to my client that they applying a high-temp tolerant, low emissivity coating. Using Dr. Bob's heat loss calculator, I figure that on the basis of the difference in E alone we should see a resultant reduction in the rate of heat loss on the order of 77 kW -- and that's before you account for any apparent or actual surface temperature difference. The actual savings could be up to three or four times that depending on how much lower those parameters might be in reality.

My question to you is whether given no more information than I've provided (which is all I've got for now), can we assume a realistic range of reduction in surface temperatures, and thus a corresponding savings in heat loss? Or is this impossible to do without actual testing. I realize its complicated because at these temperatures the value of E will not be uniform across all wavelengths.

For what it's worth, I've seen what appear to be effective results of this type of measure when applied to manway doors on a large steam boiler, but in that case not only do I have no idea what the actual emissivity of the coating applied was (it was aluminized silver), but there refractory and gasket repairs done at the same time so I can't attribute all the differences seen to the coatings.
 
Re:Need option to painting electronics on boards JKEngineer 12/4/2004
Scott -
I am going to give you a partial response to your questions and some additional comments, but then suggest that you and I take the discussion offline if you want to pursue it as a B2B discussion.

First, I am not commenting on your 0.95 emissivity of the steel. However, you can measure it, so it does not need to be discussed.

Second, I was in a group in a pulp and paper company for many years that dealt with these types of issues on rotary lime kilns, although we were not using IR.

Third, a reduced emissivity of the shell may actually raise the shell surface temperature, becuase it is removing part of a path of heat rejection to the outside world. That will counter some of the savings, not augment them.

Fourth, some additional information would make this a lot more doable. For example: process temperature, nominal R value for good refractory (which we could estimate from your measurements if it is not available), shell thickness, etc. Most of this should be available. I am assuming that the plant is going to fix the refractory before they do anything else.

Fifth, recognize that using a low emissivity coating on the kiln may make it impossible to use IR to check the refractory condition. This may be a stopper by itself.

Sixth, there are other types of coatings that may be candidates, including ceramic types. They may add conductive R as well as radiative R. They would also tend to increase the temperature of the steel, which may be a problem. I believe that there are even products that can be put on the inner surface of the refractory, although I am not sure of this and these would be more expensive and need a shut down.

Seventh, the estimation of the heat loss changes needs a simultaneous solution of the convective, conductive, and radiative heat transfer of the system. It would be done for as is and for as proposed. Certainly we could estimate it with just a little more information than you have presented.

I hope this helps and would be glad to discuss it further with you directly if you wish.

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

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:Need option to painting electronics on boards jdlirab 7/15/2009
Hi, I´m an engineer student and right now I´m interested in the use of thermography in electronics components, I haven’t been able to find any good related information, I was wondering if some know about an article or an internet page where I could find something about this topic.
I´m need to do a verification on a electronic board of a CNC machine.
Thank you
 


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