small corrosion around chips on pcb...

[Genesis]

Hi all,

I have a card which seems to have a few spots of corrosion around the chips on the bottom of the PCB board. The card itself seems to be working as I've installed it in my PC, and I've run 3x different 3D benchmarking utilities to stress it out and all have come out good.

This being the case, would it just be surface corrosion of some sort ?

Is there any way of cleaning/removing corrosion from chips/cards ? Any way of 'scrubbing' gently with a soft bristled toothbrush and maybe using alcohol or something ?

I'll try upload some pics of the affected areas shortly.


Regards,

 

[slydogsrus]

Typical corrosion can be removed with rubbing alcohol and a toothbrush, then allow to dry completely before reassembly.

Depending on the corrosion type it can lead to weak solder joints and intermittent operation, but if it works as it is, then "if it ain't broke don't fix it" !

If I had the board on the bench I would remove the corrosion and reflow the solder in the affected areas.

Best of luck, Slydogsrus

 

[Genesis]

Hey Slydgosrus, thanks for the reply

Depending on the corrosion type it can lead to weak solder joints and intermittent operation...

Do you meant the corrosion itself will lead to weakness ? or cleaning/removing the corrosion will ? Wouldn't Corrosion spread though ?

...I would remove the corrosion and reflow the solder in the affected areas.

Only problem is the chips are Micro in size.. very tiny. Even if I had the tools, my in-experience with electronics/soldering will most likely make a bigger mess .


Thanks

 

[(*steve*)]

Post a picture.

 

[slydogsrus]

Do you meant the corrosion itself will lead to weakness ? or cleaning/removing the corrosion will ? Wouldn't Corrosion spread though ?

The cleaning or removing of corrosion will not harm anything if done properly and the board does not have any sensitive Mosfet devices that can be damaged by static build up.

Only problem is the chips are Micro in size.. very tiny. Even if I had the tools, my in-experience with electronics/soldering will most likely make a bigger mess .

If they are SMD devices then you have to be even more careful as those parts can be damaged much easier if you don't know what you are doing, and reflowing an SMD chip requires special equipment, or at the very least a low wattage iron with the proper tip and a good magnifying station to see what you are doing.

Like Steve said post a picture so we see what you are talking about.

Slydogsrus

 

[Genesis]

Hey guys,

Here's a link to some photos I took.

http://s998.photobucket.com/albums/af101/Widget1983/Electronics/

The affected areas are only on the bottom of the card (from what I could tell).




Regards,

 

[(*steve*)]

I see something nasty on image number 5 and 10 and 12/13 (haven't gone past this).

5/12/13 seem to show the same location. It looks like corrosion, but a close-up that is in focus would help.

10 looks like damage caused by overcurrent, and if I was really bold, I would suggest the overheating was on an internal layer of the board. Again, a closeup that is in focus.

Image 7 is the sort of thing we need, but remember that even that is only sharply in focus in a small area (the area around the pins of the second header)

 

[slydogsrus]

The most concerning picture I saw was number 10 with R641, and like Steve I agree it looks to be due to overheating. I am also concerned with what is right above R641, hard to tell without cleaning it up first. To the left in number 10 TP603 appears to be typical copper oxidation.

Picture 5 almost looks like some kind of mold growing on it, if I was to guess this card was used in a high moisture enviroment, but most all of the other pictures seem to show dust and common oxiditation.

I would just use some rubbing alcohol and a toothbrush and clean the board up first to remove the dust and oxidation, and possible mold and go from there.

Depending on the camera you are using, a good backlight and setting a manual ISO of around 100 with macro on, and turning the flash off tends to get better up close pictures from the cameras I have used.

Best of luck, Slydogsrus

 

[Genesis]

Hey all, thanks for the replies

Yeh, I've got a couple copies in there, some looked better then others and some I took of different angles.

I'll see if I can pick up some rubbing alcohol tomorrow and give it a bit of a clean after work. Is there anything I should look for in the Alcohol ? some thing I should watch out for which can be bad for the card ?

Sorry about the quality, all I do is chuck it into Auto mode, point and shoot lol, I'll check out the settings and see if I can do manual focus or something.


Regards,

 

[slydogsrus]

I use 70% rubbing alcohol solution, they make a 90% but the more alcohol content the more agressive it can be, and 70% is the cheap stuff here in the U.S.

If you have never washed a board before, I recommend applying it to the toothbrush first then scrubbing, you just don't want to apply too much and get components like caps on the top side wet.

Best of luck, Slydogsrus

 

[(*steve*)]

There are a few things to watch out for, but in general you can submerge boards in alcohol without any problems.

The areas where you can have problems:

* If the alcohol leaves a residue (put a spot somewhere and see if there is any mark once it evaporates)
* Anything with lubrication (it can wash it away)
* Heatsinks (whilst it won't remove goo from under the components, it may wash any excess onto other parts, making a mess)
* Some markings can be removed (but usually only marks made in pen)
* some LEDs may be affected (the ones with the soft gel-like lens on the top)

Most components are made to withstand some washing after manufacture. If you were really anal you could track down the manufacturers data for each component...

The moral is: Don't leave stuff bathing in solvent for hours, but likewise don't get too concerned if something gets a bit of a splash.

I use isopropyl alcohol, but there are also special solutions made for cleaning boards.

 

[Genesis]

Hey all,

Thanks for the replies

I managed to get a toothbrush/cotton bud and remove most of the affected area. I took some more photos though even mucking around with the settings I couldn't figure out how to zoom/focus in more.

http://s998.photobucket.com/albums/af101/Widget1983/Electronics/HIS HD4870/

Also, I cleaned the areas, but didn't notice all the little fibres from the cotton bud until i uploaded :S

Another thing, I noticed that in picture 0173 (#4) there's a little component that seems to be missing (solder joints still visible). Going back over all the photos, it didn't show up so I'm assuming it happened with the previous owner before giving it to me.
What is that part that's missing and what does it do ? That same thing happened to my Playstation 2 sometime after I got it. I was doing something with the main board and I accidently pushed on it and it came off, but ignored it and put it back together again, and it still worked, and has worked fine for the past 7yrs.


Regards,

 

[(*steve*)]

It's not unusual to find components "missing". There are pads for 2 ICs and a number of other components on that board. Perhaps they make several models, some with more features than others.

I don't see anything immediately concerning. I wonder if the dull look to many of the soldered joints has to do with them using a lead free solder (if indeed they are).

See if the board says ROHS on it anywhere. That is an almost sure sign that there is no lead in the solder. And some lead free solders look decidedly un-shiny.