vr16sp4 high failure rate

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John Deez
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vr16sp4 high failure rate

I finally am able to jump the pads ok. However, I failed two reflows in a row tonight. The first one had one emitter shorted and the second one had only one lit. These are the only reflows I’ve ever struggled with. What is so different about them?

One of the things I struggle with is that I want to tweak them after their soldered and the flux is super sticky.

Edited by: John Deez on 10/08/2020 - 22:02
John Deez
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I had the best results soldering the pads by rolling around a tiny ball of solder like he does in the instruction video. But tonight I was using paste.

I see that he jiggles them to center them. But they aren’t responding like that for me. I’ve also had problems with that much flux like they just float on it.

John Deez
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I found the guide on his site:

“The biggest problem for beginner is to keep the ultra thin solder mask layer intact.”
Slowly heat the MCPCB at no more than 2°C/second pace.

-Avoid hard and sharp object on the solder mask especially at high temperature.

-Avoid using too much soldering flux. Some aggressive flux will discolor the solder mask, some will make it bubbled.

-Slowly cool the MCPCB at no more than 2°C/second pace.

This must be why in the video he uses wooden tools to align the leds. I was using a dental pick.

id30209
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Clemence us using low temp solder and he does it under much more precise and controled enviroment than we are doing at home. When i saw the size of E17/21 i simply paid to be build by him. Not worth that hassel

WTB Titanium 4sevens 2xAA tube

John Deez
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That explains a LOT! It makes me feel better. I bought more last night and skipped the service because I’m determined to do it myself.

Is the controlled environment different from post 3 and does anyone think it needs low temp solder?

thefreeman
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here Clemence explains he use indium because he uses agressive water based flux that is too agressive at higher temperature, and he uses this flux because he says it is easier to clean.
Personnally I had no issue cleaning the LEDs thoroughly when using rosin based flux, I used a boiling Isopropyl alcohol bath (as he suggested in a previous comment) and the LEDs and MCPCB are super clean.

If your flux gets sticky it’s because your working temperature is too high or the flux is of bad quality, I use chipquik SMD291 and at SnPb temperature it stays fluid, and consequently is well cleaned off afterwards.

John Deez
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More failures. This is frustrating.

Does the solder mask on these fail 100% of the time at a certain temperature, that would also make the flux sticky?

Has anyone done this succesfully with normal solder paste or solder and no clean flux?

John Deez
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Tonights mistake: Reversed the polarity! Both reflows work although they aren’t perfectly flat, even after being pushed down.

thefreeman
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Too much solder, the pushing down method doesn’t work with this MCPCB and LEDs, the excess solder doesn’t overflow, and that also might be why you had some LEDs short.

John Deez
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Maybe. BUT I have pushed them down successfully a few times if there isn’t way too much. The issue with this method is they also move side to side and putting them back into a window pane is impossible.

I had 2/2 success last night and I think it had to do with using only wooden tools on the pcb. I do think that using less solder may let the pads suck down properly. Its seems like they either have a generous amount on them, or they look like they are just barely tinned.