Soldering - Desoldering issues

[MXM]

Hello all...

preambule.
i used to do a lot of soldering/desoldering back in mny school days and in other jobs, now i have to get hands to work again since no one else is gonna do it around here,

now i got a lot of those Nasty hp d530 sff going all boom!... sometimes the psu sometimes the mobo... my issue here is related with the mobo... i have found very hard to desolder some (just to not say all) the caps that regularly get blown...
i have to use some not recommened old school tricks... at the end the job gets done but i dont feel like i should rely on those not-so-ortodox methods (i have gone to the point of using the hot air gun, to desolder a cap!)... specially because i might get things worse eventually at some case.

anyways, i thought of this as a good start point to people with such problems, from noobs to experts... we could all use tips for improving this, i guess......

im thinkin on getting a new solder roll... but not sure what should i look for, and the extractor wel ive never had problems with em but for some reasons on this mobo they are giving me hard time...

anything is appreciated, peace.

btw... ive been a not-so-active reader and then member but ive enjoyed this site from long ago

peace.

[stj]

Re: Soldering - Desoldering issues

put some 60/40 crap solder on the joints - it lowers the melting point of the original lead-free solder.

[mathog]

Re: Soldering - Desoldering issues

put some 60/40 crap solder on the joints - it lowers the melting point of the original lead-free solder.

Or at least it makes a very good thermal connection to it, which also helps melt it.

On a related point though, with most of the circuit boards now using lead free solder, might it not be best to also use lead free solder to attach the replaced components? And if so, which lead free solder is most likely to match what is on the circuit board? There are a bunch of different mixtures available, and it isn't like the old days when the only question was the ratio of lead and tin in the solder. Boards have stamps on them to indicate they are lead free, but never which type of solder was used.

What I'm most concerned about is that the mix of lead free and leaded solder may not be at all ideal, and could be more prone to cracking or other failure than either type pure. See

http://en.wikipedia.org/wiki/Solder#Lead-free_solder

the section about how bismuth interacts with lead. Lead containing solder is certainly easier to work with than the lead free stuff, but mixing the two may not be great for the long haul...

[stj]

Re: Soldering - Desoldering issues

i only use lead-free solder.

you dont need to "match" solders.

there are 2 basic types of lead-free,
with silver.
and without silver.

with silver flows much better and has a melting point about 10' lower.
usually 217'
the bad, it costs about 50% more.

the other question is flux.
there are several types.
the main ones being "no clean"
that you dont need to clean and leaves almost no residue.

and "mild activated"
this is agressive stuff that can solder to metals that can otherwise be a problem.
however, it often leaves more of a mess, and you *must* clean it afterwards because it's corrosive.

there are others such as "aquatic" and "highly activated" but you want to stay away from that stuff.

imy personal fav is silver loaded with no-clean flux .7mm
http://uk.farnell.com/metaux-blancs-...50g/dp/1689792