Cleaning and fixing corroded components?

[Artlav]

The rear view camera on my car stopped working one day.
A look inside reveals why.

Size comparison:

High resolution:

Basically, many years of road grime was seeping inside the poorly sealed camera capsule.
The PCB seems fine, but several components are corroded.

New one cost around $400, or $150 from China.
Which is a little too much for a $0.001 worth of problems.

So, i want to fix it, and step one is cleaning up the corrosion.
At least to see what is connected and what isn't.

What is a good way to do it?
I don't want to scrub or touch it much, since many parts are dust sized.
Soak it up in isopropyl alcohol?
Wash with orthophosphoric acid?
Something else?

[all_repair]

Brush off as much as you can.  And put in for an ultrasonic bath with distilled water.  Upgrade the solution to stronger type if needed.  Do not ultrasound clean too long with strong solution (like alcohol), the protection plating of the conductors may wear out.

[darkness_electro]

I believe a gentler treatment should be used. First, try a sponge and some paste for dishes, the one with little granules inside. If precise size of the leads is not important, try to tin them with a strong flux, then you should be good to go. If solder doesn't take, then try, as suggested, to brush.

[Ian.M]

Its almost certainly FUBAR.   The usual effect of electrolytic action is to dissolve more positive tracks, leads and component terminals.  You can see that the large brown ceramic cap on the left near the board edge has lost all its terminal metallization from the near end.  Its likely that the pad has also been eroded away.   I suspect that is the bulk decoupling cap for the supply and that any passive components connected to the +v rail will also be damaged. (Active devices generally have thicker metal terminals so often survive). Expect some of the vias to have gone open circuit as well.

If this is just the power board (with the camera sensor on a separate board) you can wash it in hot water with one drop of detergent, scrubbing gently with a soft toothbrush.  If any parts come off it proves the tracks were eroded BER.  Rinse thoroughly in distilled water, shake and blot off as much as possible then rinse with IPA to remove residual moisture and air dry.   You will then be able to inspect it more closely, but I doubt you will be able to fix it without a schematic (or an identical unit) to determine the values of failed passives and extensive track repair.

[edpalmer42]

A toothbrush might be a little too aggressive.  Whether you use detergent or IPA, maybe start with a paintbrush and see how that goes.

Ed

[DmitryL]

New one cost around $400, or $150 from China.
Which is a little too much for a $0.001 worth of problems.

IPA in ultrasound bath.
What are you going to do with the corroded out taces and pads of the LGA (?) chip on the photo ?
Fixing things under a BGA package if any sounds like a good fun.

[obiwanjacobi]

A de-ox spray? (contact spray -> WD40)

[Artlav]

Well, bad news and good news.
Bad news - nothing really helped. I cleaned all the corrosion away with cotton sticks and IPA and reflowed most contacts, without much success.

Good news - the badly damaged board is only a power supply, turning 12V into 3.3V for the camera board.
The camera board itself is fine - i get clear video from it when powered with a bench supply.

So the problem is now reduced to making an auto-grade 12V->3.3V switching converter that fits within a square centimetre.
Hm...

[Artlav]

Post mortem, high res:

Several tracks and vias around the LGA package have dissolved completely, along with assorted damage mostly in the lower part of the board.

Trying to trace out the PCB - there is at least a video signal LC filter of some sort besides the power supply, and the correct output voltage turned out to be 3V.
Black solder mask is horrible for visibility.
On the good side, it's only a two layer board.

[Gyro]

As the camera board still works, might the easiest option be to build a simple 3V linear reg upstream (in the boot?) rather than trying to salvage the ruins of that board?

You might even squeeze an 'air-wired' (suitably epoxied and insulated of course) regulator using a TO92 or SOT223 pkg into the back of the camera. I can't imagine that it pulls that much current (check).

If you're already getting a clear video picture then I doubt  if the Video LC filter is all that critical.

[Artlav]

In the end i kept the old PCB (it had the unobtanium connectors soldered on it), and added a little 12V->3V converter on top of it.

It fits quite well, and works fine.

Potted the whole thing, hopefully it will work for some time now.

build a simple 3V linear reg
...
I can't imagine that it pulls that much current (check).

160mA of current, which is 2W or so in a tiny unventilated box.
Not a good idea.

[Gyro]

A very nice looking repair (or addition) 

Hmm, yes 2W would have been a bit high with a linear, would have kept it nice and warm through your winter though. 

[codeboy2k]

Now that you've got it opened up,cleaned and repaired, perhaps you should pot it in potting compound ?

[Emiter]

Nice looking repair. Glad you got it opened and sorted