How to avoid Liquid Damage due to Soldering

[caspian]

Dear Technicians,

I have a bad experience in soldering:
Two months ago, I soldered the point of PJ801 (in the photo) on a laptop mainboard using flux and leaded solder. Then, I cleaned the area using pure paint thinner. I did not used any other substance. but there was still some flux residues which I refused to clean. I did this because I did not want to use too much thinner.
Today, the customer came back. I opened the laptop and observed one side of the capacitors in the area got a dark color. Even the solder of PJ801 became dark. This is what happens to capacitors when they get liquid damaged. but the other pins of the components look shinny.
In the photo, I noticed that the flux residues are gray-colored too. Probably, the thinner made brown flux turn gray.

Now my questions are:
Why have this liquid-damage happened?
What did I do wrong in that soldering?
Was the liquid-damage due to flux residues or something else?

note: I do not use my isopropyl alcohol because I used it sometimes but it had the following problems:
1- It could not clean the flux completely.
2- It could not clean glue from the board.
3- It leaded to liquid damage too. It may be mixed with water by the maker.
Then, I decided to use paint thinner which is stronger and can clean flux and glue completely.

thanks

[diif]

Re: How to avoid Liquid Damage due to Soldering

I always and only use 99% Isopropanol for cleaning boards and flux. It doesn't cause any damage and dries perfectly leaving no residue. IPA is hydroscopic, it absorbs water but stored and dispensed properly and this isn't an issue. I use an antistatic brush for stubborn parts and foam swabs to clean up. I've never had any issue with a board after repair and clean up.

What's in the paint thinner you used ? there's many types/formulations.
The customer either spilled liquid in the exact same place, or what was in your paint thinner/flux did the damage, not being cleaned properly.
What flux do you use ? some are water based.

[caspian]

Re: How to avoid Liquid Damage due to Soldering

The thinner is colorless and is called "Instant Thinner". Its ingredients were not mentioned by the maker. It was recommended for cleaning nitro cellulose paint, clear lacquer, polyester lacquer, putty, primers, and washing industrial components. It does not seem to contain water, because it completely evaporates when I leave a drop of it on a surface.
The flux is an ordinary liquid flux made by an unknown maker. It may contain water, but I do not know. It is pretty oily and looks like a solid paste flux that was heated and became liquid. When I leave a drop of it on a surface, it gets dry and solid after a few days.
The flux is brown. When I pour thinner or isopropyl alcohol on it, it turns dark gray.

I found a photo that looks like the thinner which I use.

Any ideas on why the capacitors turned gray in one side?
In general, what substances can make such a damage on capacitors?

[diif]

Re: How to avoid Liquid Damage due to Soldering

Only you can tell if the liquid has come from the customer.
If its not from the customer it's from you. I use genuine Amtech 599 no clean tacky flux, cleans away easily with Isopropanol.
Perhaps when you didn't clean the board properly, heat made what was left on the board flow towards the caps and that's what damaged them.

[caspian]

Re: How to avoid Liquid Damage due to Soldering

Probably, there was no liquid by the customer.
can flux residues damage the capacitors like what happened?

[diif]

Re: How to avoid Liquid Damage due to Soldering

Decent flux won't, neither will isopropanol.

[caspian]

Re: How to avoid Liquid Damage due to Soldering

I have to change my cleaning methods.
If we consider flux residues that were mixed with thinner and turned dark gray, cam them damage the capacitors like what happened?
Is it possible the instant thinner makes solder joints weak? or no such problem to worry about?

[caspian]

Re: How to avoid Liquid Damage due to Soldering

Oops, I had typing mistake.
Edition of the previous post:

If we consider flux residues that were mixed with thinner and turned dark gray, can they damage the capacitors like what happened in the photo?
I can think dark gray flux may be not the same substance as brown flux. it may be a harmful substance to solder joints.

Is it possible the instant thinner makes solder joints weak? or no such problem to worry about?

[stj]

Re: How to avoid Liquid Damage due to Soldering

does that chemical feel greasy on your fingers?
it looks like white spirit.

post a foto of the label, there should be an MSDS datasheet for it.

[storm12]

Re: How to avoid Liquid Damage due to Soldering

As diif said above, best thing is to use quality flux and 99.9% purity IPA. I use amtech 559 no clean flux as well and never had problems. Since you are not sure what that thinner contains I don't think it's a good idea to use it as you don't know how it will affect the components or how the chemicals react to the flux you're using and may cause more damage.

[stj]

Re: How to avoid Liquid Damage due to Soldering

amtech flux may be a problem,
the u.s. sellers may refuse to ship because of sanctions and getting it via china is asking for trouble.
probably 95% of it would be fake.

[diif]

Re: How to avoid Liquid Damage due to Soldering

There is no problem with genuine Amtech 559, agreed most on ebay is fake, insatint is a genuine UK seller on ebay though.

[storm12]

Re: How to avoid Liquid Damage due to Soldering

I think problem might be procuring genuine amtech in Iran.

Maybe insat are shipping there? caspian, it might be worth asking http://www.insatinternational.com/

[caspian]

Re: How to avoid Liquid Damage due to Soldering

Thanks for all the replies.
Finally I found the problem:
I discovered that the board was exposed to a bit of water. most areas of the board are clean now. but the points that contained my flux residues, absorbed the water. So only those points were damaged on the board because those points made the water to stay. This is what happened to the capacitors.
The flux residues did not damage the capacitors directly. because I used the same flux and thinner on another board and it is still fine.
At least, we learned something.

[storm12]

Re: How to avoid Liquid Damage due to Soldering

Glad you figured it out!

[Th3_uN1Qu3]

Re: How to avoid Liquid Damage due to Soldering

Never trust the customer when they said they haven't spilled anything...

[sam_sam_sam]

Re: How to avoid Liquid Damage due to Soldering

This is the flux remover that I use it works very good and you only need a little bit dose a lot