0

144/m NeoPixel wires keep coming loose
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

144/m NeoPixel wires keep coming loose

by benbergman on Tue Feb 20, 2018 12:41 pm

Hopefully I'm posting this in the correct part of the forum. Please feel free to move it if it is better posted elsewhere.

I have a strand of 144/m NeoPixels in a wearable project and I have had the wires pop off the LED strip a couple of times. I'm wondering how others have dealt with the fragile connections on these tiny solder pads. I know that you can get some solderless mechanical connectors for the less dense LED strips but I haven't found anything yet that seems designed for the 144/m strips. I've also not yet tried globbing on tons of hot glue as I don't want to lock myself out from being able to repair the strip (though perhaps the hot glue would mean I never need to repair it again). This wearable is on display to the public for a long time, so I need to be able to either repair it easily or ensure it won't be damaged again.

Any suggestions for improving the reliability?

benbergman
 
Posts: 12
Joined: Thu Feb 12, 2015 11:48 pm

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Tue Feb 20, 2018 1:02 pm

A solder joint that is subject to repeated flexing will tend to break at the joint. The bending stress on the wire tends to concentrate at the point where the flexible wire meets the rigid solder joint.

The remedy for this is to "stress relieve" the joint by providing support for the wire near the joint to spread out the bending stress. There are a number of ways to do this: Wrapping the joint with Kapton tape or coating it with a layer of hot-glue or E6000 adhesive are easy solutions - and can be peeled off if you need access to the joint at a later time.

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by benbergman on Tue Feb 20, 2018 1:48 pm

Thanks for the tips. The positioning of the connection is such that it is fairly well hidden from direct contact and so flexing should be minimal, but it is dangling in free space. I suspect vibrations are causing the small/poor solder joints to come loose. My solder joints are likely to blame for that but it is awfully tough to get a good joint on those tiny pads. Any suggestions for improving the solder joints there? I'll need to make a repair there again and want to ensure the best joint possible before covering in hot glue.

benbergman
 
Posts: 12
Joined: Thu Feb 12, 2015 11:48 pm

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Tue Feb 20, 2018 1:59 pm

Is the wire breaking at the joint, or is the solder pulling off the pad?

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by benbergman on Tue Feb 20, 2018 4:28 pm

The first time the solder pulled off the pad. With the most recent break I have not had a chance to disassemble to diagnose fully but applying pressure to the joint restores functionality, so I assume the same as happened this time too.

benbergman
 
Posts: 12
Joined: Thu Feb 12, 2015 11:48 pm

Re: 144/m NeoPixel wires keep coming loose

by caitlinsdad on Tue Feb 20, 2018 4:53 pm

Those pads on the mylar strip are easy to heat off. I guess it takes experience to tin them first, tin your wire and then join with minimal heat. You can try to solder the power connections(+ and ground) to the next full solder pad instead of the very end and incorporate the longer wire in the strain relief blob of glue or tape. I have even put extra wire jumper hooks or outriggers soldered to the next full pads to provide extra strength. Nothing really sticks to the slick strip so in extreme case, sacrifice the first neopixel so you can mechanically fasten something/clamp/tie-wrap loop for a real hook to take the weight. Good luck.

caitlinsdad
 
Posts: 574
Joined: Fri Feb 24, 2012 4:23 pm

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Tue Feb 20, 2018 5:15 pm

Solder pulling off the pad means that the solder did not 'wet' the pad and properly bond to it. Tinning the pads first as suggested by caitlinsdad can help. But even that ca be difficult if the pads are not clean. Sometimes the strips have a some residual oil film on the surface as a side effect of the manufacturing process. Cleaning the pads first with a bit of isopropyl alcohol can make the soldering go easier.

Be careful not to overheat the pads, since that can break down the adhesive that holds them to the strip. If you can't complete the joint in 3-4 seconds, stop and let it cool down before trying again.

http://learn.adafruit.com/adafruit-guid ... -soldering

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by benbergman on Thu Feb 22, 2018 1:50 pm

Thanks for your help. I had attempted to tin the pads first but likely the tiny surface area meant that any residue on it allowed it to pop off at the first sign of tension. I'll remove the connection, clean it, tin it, reconnect it, and coat it in hot glue.

benbergman
 
Posts: 12
Joined: Thu Feb 12, 2015 11:48 pm

Re: 144/m NeoPixel wires keep coming loose

by benbergman on Mon Feb 26, 2018 3:37 pm

I performed a repair that I think should be pretty robust now. There are three things I did that will hopefully make this thing indestructable:

1. I scraped off the solder mask on the back of the LED strip to give me more surface area for soldering. Note that the white layer comes off easily but there is also a clear enamel like layer that is more persistent - scraping from the original solder pad into the covered area helps the scraper catch the edge of the coating. The clear layer was not yet removed in the attached photo.
small-IMG_20180226_103251.jpg
small-IMG_20180226_103251.jpg (121.65 KiB) Viewed 306 times

small-IMG_20180226_104208.jpg
small-IMG_20180226_104208.jpg (121.76 KiB) Viewed 306 times


2. I put a large amount of hot glue over the solder joint to remove any strain on the joint directly

3. I glued a portion of a zip tie to the back of the wire and LED strip to deflect any stresses away from the joint.
small-IMG_20180226_104911.jpg
small-IMG_20180226_104911.jpg (129.06 KiB) Viewed 306 times

benbergman
 
Posts: 12
Joined: Thu Feb 12, 2015 11:48 pm

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Mon Feb 26, 2018 3:40 pm

That looks good. Hope it holds up for you.

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by acintra on Wed Aug 14, 2019 9:38 am

adafruit_support_bill wrote:That looks good. Hope it holds up for you.

I have a similar problem but not with the solder but with the neopixel itself. The strip light works fine for few minutes and afterwards 1 pixel fails and from that failed pixel the rest of the strip either change the color or just shuts off. I believe this is a problem with reliability of these mini neopixels. Can you help me suggesting something I can do? Thanks

acintra
 
Posts: 11
Joined: Wed Aug 07, 2019 9:21 am

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Wed Aug 14, 2019 10:23 am

@acintra - Is it always the same pixel that fails?

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by acintra on Wed Aug 14, 2019 10:55 am

hello @bill.
Not the same pixel. we have a 4 times 144 mini neopixels aligned and needed to control each 48 pixel independently. It is randomly failing and every time it fails we replace 3 before and 3 after the pixel failed. They are cut to length and the solder is done in the laboratory. Do you thing that a non mini neopixel has better reliability? Thanks

acintra
 
Posts: 11
Joined: Wed Aug 07, 2019 9:21 am

Re: 144/m NeoPixel wires keep coming loose

by adafruit_support_bill on Wed Aug 14, 2019 11:13 am

I don't think we have any reliability statistics on these. I haven't seen an abnormal frequency of failures reported.

How do you have these powered? Do you have the recommended large filter capacitor between 5v and GND?

adafruit_support_bill
 
Posts: 74650
Joined: Sat Feb 07, 2009 10:11 am

Re: 144/m NeoPixel wires keep coming loose

by acintra on Wed Aug 14, 2019 11:22 am

May I send you a short video showing you the exact problem?
We have the data sent to Adafruit Fadecandy and yes, we have a large filter capacitor on power supply outputs.
Thanks

acintra
 
Posts: 11
Joined: Wed Aug 07, 2019 9:21 am

Please be positive and constructive with your questions and comments.