Dotstar LEDs (APA102)
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Dotstar LEDs (APA102)

by lucasreddinger on Sun Jun 21, 2015 7:56 am

How do you guys get these soldered to the PCBs made for them?

I don't know if I'm melting the LEDs or just not getting a good connection, but all I see is a tiny green spark in the LED, but it doesn't truly light as it should.

I tin the PCB mounts, place the LED on top, then try to quickly melt and reseat each side. Doesn't work well, but it's the best method I've found so far.

This SMT stuff is a disaster for hand soldering. Such a waste.

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Joined: Sat May 16, 2015 4:31 am

Re: Dotstar LEDs (APA102)

by bcoggs on Sun Jun 21, 2015 8:39 am

The best way is to apply solder paste via stencil. Failing that syringe, failing that, solder on very fine tip of iron with flux pre-applied on device.


Best reflow method is oven, failing that, hot-plate + hot air gun, failing that, hot air gun.

If the dotstars are like the ws2812's they tend to melt very easily.

some videos on smt soldering with just an iron here: http://store.curiousinventor.com/guides ... ering/101/

A cheap way to achieve bottom heat is with a small hot-plate. I put sand on the bottom of the hot plate to even the heating.

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Joined: Mon Jun 28, 2010 3:17 pm

Re: Dotstar LEDs (APA102)

by adafruit_support_mike on Mon Jun 22, 2015 12:49 am

As a tip for doing SMT by hand: don't try to tin all the pads before placing the part. Put a small blob of solder on one pad, heat that and place the part, then let the pad cool. That connection tacks the part in place, and you can tweak the alignment if you need to.

Once the part is sitting where you want it, do a second pad to lock the part in place. Again, you can reheat and tweak if necessary. Once those two pads are cool, you can do all the other pads pretty quickly. If the pads are close enough together, just get a well-fluxed blob of solder on the end of your iron and drag it along the connections.. capillary action will pull enough solder to make a joint away from the blob as it passes.

If you get solder bridges, use a bit more flux and some solder wick to clean them up.

SMT parts are made to take advantage of the surface tension of solder. Once you learn how to make that work for you, working with them is kind of fun.

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Re: Dotstar LEDs (APA102)

by lucasreddinger on Mon Jun 22, 2015 2:17 am

Great, thanks for all the tips. I'll be patient and expect this to take some time.

I guess I'll get some other LEDs in the meantime so I can get a prototype working soon.

Posts: 9
Joined: Sat May 16, 2015 4:31 am

Please be positive and constructive with your questions and comments.