Re: Soldering/Desoldering temperatures

From: mike (spamme0_at_netscape.net)
Date: 12/18/04 

Date: Fri, 17 Dec 2004 23:12:35 -0800

caligulashorse@hotmail.com wrote:
> mike wrote:
>
>
>
>>Raising the iron temperature helps because the tip can cool somewhat
>>and still melt solder. But if you use it on a joint with lower
>
> thermal
>
>>mass, you overheat things.
>>
>>If you're trying to remove an electrolytic from a motherboard, each
>
> end
>
>>is typically connected to an internal ground plane that does a great
>
> job
>
>>of conducting away the heat you apply. And the holes in the board
>
> are
>
>>tiny. Not much clearance to pull out the wire.
>
>
> Interesting you should mention electrolytics because that's what I'm
> removing, and thousands of them. I'm recapping an old recording
> console, So, thank you from bringing this up. I wasn't aware that they
> did that, but it makes perfect sense.

First, are you sure the caps are bad?

It varies greatly from brand to brand, but...sometimes you can just bend
small diameter radial lead caps over and the leads will pull right out.
  Remove 'em from the top one lead at a time.

>
>
>
>>I use a BIG 3/8" chissel tip 50W 1050 degree F iron on a light dimmer
>
> to
>
>>control heat input...and a LOT of care on ground plane connected
>
> parts.
>
>>Preheating the surrounding area with a hot air gun also helps.
>
>
> Ok, so wht do you mean by "a lot of care"? Also, if I jack the heat
> up on my station, any suggestions on a temp setting?

I run my big iron so hot that the solder oxidzes and turns purple in
short order. I use 800F tips in the small weller iron.

Another thing that sometimes works is a heat gun. Depends a lot on what
else is on the board and how close to what you're removing. I've often
stripped computer boards with a paint-stripper heat gun. Heat up the
backside and the caps just pull out.
This obviously won't work if other stuff is gonna fall out too.
Get a helper's extra hand to apply hot air to preheat while you
desolder.

>
> As for the kind of solder I'm using it's a 60/40 Kester solder.
>
> Thanks for the great post!
>
> This was really helpful (I'm already looking into a metcal desoldering
> stataion on ebay!)

Metcal is a great system, but you may need more heat depending on the
ground plane situation.

>
> /John\
> 

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