On board Soldering advise

[underwaterchippie]

Currently thinking to repair the following analog board. I spotted a problematic area where a few capacitors have burned out. Any advice on how to tackle this challenge? Below a comparison between a good and a bad board:

Much appreciated

 

[rjenkinsgb]

It looks to me like the main problem is the electrolytic at the top centre of the picture, that has blown and leaked with liquid running down over the smaller components.

I'd remove that cap and clean the board thoroughly with white vinegar (which will remove many corrosion residues) then a few rinses in deionised water, scrubbing with an old toothbrush at each stage.

The other parts may still be OK, though the two upper ceramics do look rather nasty...

 

[Nigel Goodwin]

It looks to me like the main problem is the electrolytic at the top centre of the picture, that has blown and leaked with liquid running down over the smaller components.

I think the spillage is perhaps external to what's in the picture? - aren't those capacitors tantalum?, certainly I'ver never seen any of that type leak - and I've seen a LOT of leaking capacitors

I'd remove that cap and clean the board thoroughly with white vinegar (which will remove many corrosion residues) then a few rinses in deionised water, scrubbing with an old toothbrush at each stage.

I certainly wouldn't use white vinegar for cleaning a board (acetic acid isn't a good idea) - I'd suggest using IPA, or even meths. An aerosol of Electronic Safety Solvent is a good choice as well.

With IPA or the aerosol I wouldn't use water on the board either - but a tooth brush is good.

What I did have at one time, was a special 'cleaning aerosol' - it came as a kit with a trigger fed pipe feeding to the centre of a hard bristled round brush - you simply pulled the trigger and brushed away. Replacement aerosols were available, and it was the best manual PCB cleaning device I've come across.

 

[rjenkinsgb]

It could well be external, it just appears to start around that cap.

Dilute ascetic acid - white vinegar - will remove and neutralise most products of electrolytic corrosion without damaging components.

Just don't leave it on for more than a few minutes or possibly up to an hour; however long it takes to scrub the corrosion residue off completely.

It does work wonders on badly corroded PCBs. Obviously no need if whatever it is will wash off with deionised water or IPA alone, leaving no residues.

 

[underwaterchippie]

Interesting comments! Thank you all!

I am starting to think that the fluid has entered the device and dripped on that spot. This is used in Skin treatments and there is a lot of gel that is applied to the applicator - similar to ultrasound treatments…

I’ve tested the tantalum capacitors and seems fine. What is the name of the round component with the number 100 on it? Not familiar with those!

 

[Diver300]

What is the name of the round component with the number 100 on it? Not familiar with those!

It's a 10 μH inductor. Almost certainly part of a switch mode regulator.

 

[rjenkinsgb]

What is the name of the round component with the number 100 on it

It's an inductor, part of a power filter or switched mode supply (eg. a buck or boost converter).

[Diver just beat me to it].