BuffaloFan32
Well-known member
Has anybody tried or had any luck with repairing an LED that is part of a strip? I always end up cutting non-working LEDs out and resoldering but I wonder if there is a better way.
Repairing a WS2812
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It's basic SMD rework, but the chip may be highly water absorbent so it may need baking out first if hot air is used. Some of the suppliers also use low melting point plastics which means temperature control is vital.
I've chip replaced APA102s. I use two soldering irons with wide tips so I heat all pads for the chip at the same time and lift it off when the solder is melted. I then solder it down like normal for surface mount of it's lead type. Two if the TS100 TS-K slanted blade tips works nicely for these small packages. You could also try a hot air soldering station, but that may cook the chip. Baking out likely would be needed before removing one for use that way.
There are a number of places where you can buy the chips, but I just remove one from the beginning or end of a cut off strip, and solder it in place of the dead chip. That way the characteristics are all the same.
If I was using hot air for removal, I'd likely shield the LEDs to either side with aluminum foil or some other form of heat shield.
I've chip replaced APA102s. I use two soldering irons with wide tips so I heat all pads for the chip at the same time and lift it off when the solder is melted. I then solder it down like normal for surface mount of it's lead type. Two if the TS100 TS-K slanted blade tips works nicely for these small packages. You could also try a hot air soldering station, but that may cook the chip. Baking out likely would be needed before removing one for use that way.
There are a number of places where you can buy the chips, but I just remove one from the beginning or end of a cut off strip, and solder it in place of the dead chip. That way the characteristics are all the same.
If I was using hot air for removal, I'd likely shield the LEDs to either side with aluminum foil or some other form of heat shield.
BuffaloFan32
Well-known member
Thanks Eka. I do not have much experience soldering components as small as these but I will look into the tips you mentioned. Sometimes, an LED will stop working after it is already on my project so some of the baking suggestions you had might not work. Do you know of any good tutorials?
I'm no expert either, but I at least know many of the issues and were to look. Also soldering is so second nature to me and I don't think of how to do it. I've been doing it since I was 8.
PS, buy the high quality solder and flux. A good modern temperature controlled soldering iron also help.
I would search over at EEVblog forum. I know Dave has a video or few on surface mount soldering techniques. Lots of flux and a quality solder are requirements. Louis Rossmann also talks about and shows soldering techniques during repairs on macbooks. His shop sells the flux and some of the equipment he uses. I'd get two TS100s, a selection of tips, and proper 19 to 24 VDC power supplies for them. With two I can pluck most smaller surface mount parts off of PCBs quickly. Louis likes to use hot air, but as I mentioned it can have issues. PS, the round pointed tips suck for soldering. It's hard to get good heat transfer from them to the joint area. With my TS100 soldering irons I often use TS-D24, TS-BC2, TS-K, or some custom ones I made for special uses by modifying existing tips. I usually have the D24 on my primary soldering iron, and the BC2 on the other. I'll switch them both to K tips when I want to remove small SMD devices like SO-8 chips, and bigger resistors and capacitors.
Louis Rossmann https://www.youtube.com/channel/UCl2mFZoRqjw_ELax4Yisf6w
EEVblog forum https://www.eevblog.com/forum/
BuffaloFan32
Well-known member
@Eka, here is a good example of my problem. I somehow shorted out a Teensy and when I turned everything back on, my display looked like this:
I now have 3 problems: 1 pixel where only the red LED is out, 1 pixel that is totally out and what looks like 1 pixel that is not transmitting any data to the rest of the string (two blank rows minus the first pixel). Previous to now, I have been cutting out the bad ones and soldering new strips back in. That is hard to do and a little expensive. i would much rather 'repair' pixels if I can by reflowing solder or replacing chips if that is possible.
I now have 3 problems: 1 pixel where only the red LED is out, 1 pixel that is totally out and what looks like 1 pixel that is not transmitting any data to the rest of the string (two blank rows minus the first pixel). Previous to now, I have been cutting out the bad ones and soldering new strips back in. That is hard to do and a little expensive. i would much rather 'repair' pixels if I can by reflowing solder or replacing chips if that is possible.
In order to get an idea what needs to be done, I'd need a closeup of an LED to see what chip package type it is. That effects the best methods for removal. There are people over at the EEVblog forum that can help you much better than I can. Link in my previous post.
A Louis Rossmann video on repairing some surface mount parts. Different methods than I would use, but he also owns different equipment.
https://www.youtube.com/watch?v=sr1znnLi_hA
Another video.
https://www.youtube.com/watch?v=588iV07nEdM
You may want to get a surface mount practice kit and play with it before doing the work on your array.
A Louis Rossmann video on repairing some surface mount parts. Different methods than I would use, but he also owns different equipment.
https://www.youtube.com/watch?v=sr1znnLi_hA
Another video.
https://www.youtube.com/watch?v=588iV07nEdM
You may want to get a surface mount practice kit and play with it before doing the work on your array.
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