EEVblog Electronics Community Forum
Products => Thermal Imaging => Topic started by: Ultrapurple on February 02, 2020, 04:59:03 pm
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Dead pixel repair procedure ;)
- Take a deep breath. You’ll need it.
- Pump the room down to hard vacuum. (You may find it useful to have someone tape up round the door to improve the seal).
- Restore the room to atmospheric pressure.
- Eject the cat.
- Repeat steps 1 & 2.
- Using a small (eg jeweller’s) oxy-acetylene torch to melt the hermetic seal, remove the window from the microbolometer package. Don’t forget that you’ll have to adjust the oxygen and acetylene flow valves from their normal positions if you usually use the torch under atmospheric ambient conditions.
- Any contamination on the window should be removed carefully using a dry, lint-free cloth. Bulb-type air blowers should be avoided because they are inefficient in a vacuum. Isopropyl alcohol wipes may be used if the ambient temperature can be lowered sufficiently to avoid boil-off.
- Use your dead pixel map as a guide to identify and replace the defective pixel(s). Use only OEM replacement pixels that are properly matched to the stored NUC data.
- Remember that the array scans from bottom to top and that you’ve just replaced the wrong pixels. |O AVOID THE TEMPTATION TO SWEAR – you are supposed to be holding your breath, on account of the hard vacuum around you.
- Repeat step 8, this time replacing the correct pixels.
- Replace the package window, making sure you have the correct side out. Fitting the window inside out will mess up the performance of the AR coatings.
- Restore the room to atmospheric pressure, exhale, then breathe normally. You can use the torch oxygen supply – sparingly – as a supplement if you are feeling hypoxic.
Done properly, this procedure shouldn’t take more than 30 minutes or so. You may want to practice holding your breath first.
:popcorn:
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It's best to first mark the identified dead pixels with a small fine-tip marker, this will make the replacement job better and faster.
After you're done, wipe the marker off using a 100% alchohol solution, and sand the area for a more crispy image.
:-DD
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Example of properly applied procedure :D
https://youtu.be/ny17r03uj9Y
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You can fix pixels on displays, the only problem with the fixes is that they never work.
https://www.teamknowhow.com/discover/discover/fixing-dead-pixels (https://www.teamknowhow.com/discover/discover/fixing-dead-pixels)
https://www.digitaltrends.com/computing/how-to-fix-a-dead-pixel/ (https://www.digitaltrends.com/computing/how-to-fix-a-dead-pixel/)
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You did not mention the distilled floor polish method. :-DD
The pixels are held up on legs made of silicone, so you can make new legs for them by spot welding the silicone back on after boiling down some floor polish. You will need to find the pixel itself if both legs broke off, but there is a pixel net in one corner of the sensor where they collect.
You may also be lucky and, a bit like buttons on shirts, find some spare 'blind pixels' than never do anything. These are in fact secret spares.
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:-DD
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You are not only need vaccum, but also no dust, so it's better to use a vaccum cleaner to do both at the same time.
I found OEM pixels are too expensive for me, so sometimes I use third party ones, just find one with the correct spec (material, size, NETD, resistor, bias voltage... etc) and you can save a lot. There are also some homemade pixel methods, but I'm not skilled enough to try them yet. Be careful, wrong type pixel can damage the driving/readout circuit, and replacing transistors of them are much more difficult because they are much smaller.
Also sometimes you don't even need to replace it, you can try using a heat gun to reflow it, might be just a loose connection.
Remember to seal the package before restore room vacuum, and update the offset table afterwards. Some low quality or hand crafted pixels can drift too much and FFC shutter is not enough to correct them.