Soldering Advice Needed

[Superully]

guys, i need some input:
yesterday i had to remove two old capacitors from a pcb which turned out more difficult than i had imagined.
(1) desoldering: i couldn't get the old solder to "flow / melt", although i had done everything i was told to do: temperature at 370°, tin the tip, put some new solder on the tip to add flux to the old solder. it worked at some joints, but there was one which was impossible to get out / off. even the new solder didn't want to stick to the old one, , i even tried cleaning the old solder with a fibreglass pen. i had to give up on this joint 
(2) soldering: as you know, i'm no expert in that, but i've watched a couple of videos and read some stuff about it. so i put the new capacitor legs through the holes, cut them to the correct length and heated both the spot and the leg at the same time. the videos suggest that you add the solder wick from the other side, because it tends to flow towards the heat, therefore forming a nice little "hill" around the entire leg. this didn't work at all, the solder simply wouldn't melt. then i put it directly on the soldering iron tip and while this worked for the first "connection", it got worse with each subsequent one. at the fourth connection, it wouldn't even stick to the capacitor's leg anymore 

i feel stupid!!! now it's your time to shine: what did i do wrong, how can i get the old solder to melt and the new one to stick / flow?

one more question: is it possible that the solder wick i'm using is too old: i have this liying around for many many years, perhaps it simply isn't usable anymore. if that is the case, do you have any solder wick suggestions for me?

[Superully]

bump of the week!

[liquidx]

I doubt your wick is too old, it sits in shops for ages before you buy it also.

You could try applying flux to the area first, you can buy it in the same places you buy the rest.
Also, check if the solder you're using is the new lead-free stuff. I'm not sure about this but it might not bind well with the older solder with lead in it.

I know it's bad for your health and whatnot to inhale the leaded solder but I've never managed to get good results with the lead-free stuff anyway.

For soldering, hold the iron to the trace/leg, and apply solder from the opposite side of the leg (not the opposite side of the board). You might need to "help" it a little by applying a little solder to the trace while heating it and letting it flow around the leg first.

[funkycochise]

on a french board, there's a tutorial, to properly desolder using desoldering braid.

Here it is, passed thru google translator :

there are many pictures, this could be helpful :

http://translate.google.fr/translate?hl=fr&sl=fr&tl=en&u=http%3A%2F%2Fwww.gamoover.net%2Ftuto%2Fje-dessoude-%25C3%25A0-la-tresse-%25C3%25A0-dessouder

[Etienne MacGyver]

Like liquidx says, leadfree solder sucks bigtime !

I always use the tin with lead (60-40)

and make sure youre using Flux-core solder , that is made for electronics
it has flux inside that helps the solder to flow

http://en.wikipedia.org/wiki/Solder#Flux-core_solder

[DarthNuno]

OK, I'm using this topic for my question 

Got my new soldering station yesterday, and finally asking for some basis questions ( )

1.How do you proceed with this? 



... I mean, do you clean 'the head?' on it between each soldering (or after a couple of..), when it's still on temperature? Or do you clean the 'head' on this 'white thing' (what is the English word?) when the soldering station is cold, after the job?

2. Does this 'kind' of heavy paper is also a cleaning part? 



 

[italiandoh]

... I mean, do you clean 'the head?' on it between each soldering (or after a couple of..), when it's still on temperature? Or do you clean the 'head' on this 'white thing' (what is the English word?) when the soldering station is cold, after the job?

2. Does this 'kind' of heavy paper is also a cleaning part? 



 

The soldering iron head needs to be cleaned while working between one soldering and another. That "heavy paper" has to be a sponge. You need to add water to it so it will inflate and be ready to clean the iron.

Matteo

[DarthNuno]

Many thanks Matteo 

[liquidx]

And, even better if you can, get dry solder tip cleaner. It works just as well and doesn't reduce the tip's temperature each time because of the water.

I love this stuff.

[level42]

I always "flick" the excess solder off. Use a quick movement with your wrist and aim on a surface that can't be hart by hot solder (like a carton box or something).
Note that this is for advanced solderers only !

[Blanka]

I would say go hotter. 450 degrees (max on my solder station) is great for thick capacitor legs. And higher temperatures are less damaging then lower ones, as the time to heat can be kept much shorter.

[Vnera]

Somethings i learnd at school are. Alwees stab the sponge like you would do whit a sword. Dont wipe but stab. Also never set your iron to hot it wil burn the liquid thad helps the tin flow.

[Superully]

ok, back on this since i'm still struggling: how long does it take for an old solder joint to get "flowing" when being touched with the soldering iron? i've tried temepratures from 350 to 400 degress, but nothing happens at all. i really think my soldering station isn't capable of producing enough heat anymore ...

[level42]

Hey you should have asked when I was around (didn't I actually show you ? I forgot).

First step is to ALWAYS tin the tip of your soldering iron with some new solder, so that it covers the tip and looks shiny. If you can't get the tip shiny anymore, your tip is very likely worn out.

The thing is with old solderings is that they do not have any "flowing" fluids in them anymore. This results in the fact that the old solderings won't start becoming fluid, no matter how high the temperature you apply.

So, to start running old solderings, you will need to add a little NEW solder.  So put the iron on the old soldering, and then add a little new solder until it becomes fluid, then remove the new solder. Now you can suck it up. Recently I've switched from using a hand-pump tin sucker to solder-wick, it works MUCH better and cleaner IMHO.

As I mentioned before, get LEADED solder when you still can, it is a hell lot better to handle compared to the current unleaded stuff.

Yes, lead is bad for your health and the environment so don't inhale the fumes, but since we're not soldering 8 hours per day there is extremely little risk.

[liquidx]

Yes, lead is bad for your health and the environment so don't inhale the fumes, but since we're not soldering 8 hours per day there is extremely little risk.

Or make an extractor. That's what I did.

http://blog.makezine.com/archive/2008/11/nocost_fume_extractor.html