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Cleaning corrosion - SMD components

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xodaraP

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Hi guys,

A friend sent me a Truxton board he wanted me to have a look at and try to repair, as it stands it doesn't boot or do anything, but a quick look over it shows some pretty major track rot and a couple of components covered in corrosion. The logic is easy enough to replace (there are 3 LS163 and a LS374 that will need to be replaced) and the track rot from these components (around the LS163) can be fixed with wire jumpers

The issue I've got is there is an SMD component on the board (an NEC D65024GF035 which the MAME driver says is a CMOS gate) which has corrosion across all the pins on one side. The other pins all appear to be ok, but almost all of the pins on one side measure no continuity to their connected points and the solder pads are an absolute mess.

Given the value of the board and my wanting to learn how to fix these kinds of issues, I'm going to attempt to repair it by jumpering all affected pins on the SMD component. The solder pads are beyond my level of repair and I feel that even if they could be salvaged, it's better for me to jump the 8 or so pins that have no continuity.

tl;dr I want to know the best way to remove the corrosion from the pins on the IC so I can get a good solder joint for wire jumpers.
 
depends on how much the corrosion go deep into pin. if a little nudge will broke them, then it is real bad. if not just use something sharp to rub them off. if bad, and the chip is nowhere to replace, you can grind the epoxy a bit to expose the inside part of the pin so you can solder into it.
 
I scraped them a little bit and they didn't fall off so I think it's just surface corrosion, it's the same sort of corrosion you see when a battery leaks onto an MVS board

But in this case there's no battery and it's in 2 completely different areas of the board, wonder if it was stacked up against or underneath a board with a battery on it that leaked

I have no idea if the chip can be replaced, but the pads on that side are completely trashed so even if I replace the component getting it down onto the board will be an issue
 
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First, scrub/wash that board to see what you are dealing with.

I would say if you suspect battery acid, use baking soda paste and toothbrush.

Follow by Simple green or dawn, toothbrush scrub, rinse & dry.

Have you ever washed/dried a pcb before?

Then start testing replacing/jumpering traces that are faulty and go from there.
 
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Yea it sounds like it's still contained to the surface, you should be able to scrape back to some solid metal and solder jumps in.
If the pins break off, then its beyond simple surface and you'll need to dremel back into the module edge to expose some metal nub.
 
If the pad is totally shot you can gently sand (300grit) the masking off the PCB and solder some K30 directly to the exposed trace.
 
I have washed PCBs before, but that's not required here, apart from the issues with corrosion on those few components (and track rot around the logic which leads me to believe it's battery acid leakage) the board looks brand new
 
jassin000 said:
If the pad is totally shot you can gently sand (300grit) the masking off the PCB and solder some K30 directly to the exposed trace.
Click to expand...
That's a cleaner way of doing it I agree, but I prefer to replace the whole trace with a jumper, it's not as nice looking but it prevents any issues with further track rot

Also given I don't know if the board itself still works at this stage, it's a faster solution to getting it complete
 
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