Flux Bridges

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Hello all,

I'm having a problem with my pcb smoking and shorting while running. I went over the layout and everything seems okay (right voltages, current ...). One thing that I suspect (even though it's a very long shot) is that having leftover plumbing flux bridging between the Vin and GND pins is somehow causing shorts as time goes by, does this have any chance of being the cause? did anyone encounter something like that before ?

This topic has a solution.

nh

Last Edited: Tue. Dec 19, 2017 - 09:58 PM
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Nhmdsh wrote:
plumbing flux
Really???

I certainly hope you didn't use an acid based flux on a pcb.

David (aka frog_jr)

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I hope you are NOT using plumbing solder for PCB work! wink But, unless you are using "no clean" solder, you must get rid of the flux on the board.

 

Of course we have no idea how the board has been designed and whether this is the cause for "smoking and shorting".

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I'm pretty sure the design is correct, we had the same design fabricated before and have been using it with no problems. This is the first time I try to assemble one myself. I used plumbing flux and tried tried to clean it all up but certainly there is still some between the pins. I have some solder paste which I recently got (and will use from now on) but I wanted to know if the flux itself can cause such problems while the board is running.

nh

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js wrote:
Of course we have no idea how the board has been designed and whether this is the cause for "smoking and shorting".

I believe the OP posted here as a result of a comment made in his other post https://community.atmel.com/foru... .  He already mentioned the smoking and shorting and also provided a schematic of the board.

 

 

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I used plumbing flux

WHY??!! That's extremely bad for electronics. Can't you get normal fluxed solder for electronics?

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Plumbing fluxes are way too active (i.e. corrosive) to be used for electronics.

However they usually are water soluble, so if you thoroughly wash your pcb with warm distilled water (in a bath, preferably, with some drops of detergent) it should remove most of the flux.

Then dry it with ethanol or isopropanol. If everything goes well, you wont get corrosion later due to the flux.

 

Plumbing fluxes are also highly conductive electrically, so any residues can indeed cause shorts.

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Thanks for all the replies. I think this was the problem.

nh

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Plumbing fluxes are good for zinc gutters, buckets, coffins....and putting electronics into coffins...

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Must’ve brought tears to the eyes when soldering!

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Water cleanup after wave soldering was a deal for a while -- at least with one of our subs. I'm almost certain that they used an acid flux  ( this was a FEW years back). Avoided the nasty stuff used for cleaning rosin flux.

 

Fun fact-around the same time some Japanese manufacturers were noted for NOT cleaning the flux -- which must have been rosin. Apparently, they felt that it would be fine for the expected life of the product

 

hj