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Electronics => Projects, Designs, and Technical Stuff => Topic started by: daniel123 on May 01, 2016, 01:07:58 am

Title: Desoldering
Post by: daniel123 on May 01, 2016, 01:07:58 am
Hi

I was wondering if anyone has advice for desoldering very small smd components with nothing but a soldering iron. I have an unregulated ecg iron 20 watt and a hakko888d. and will i need a hot air gun if i try to take off surface mount ic's?

Thanks daniel
Title: Re: Desoldering
Post by: tautech on May 01, 2016, 01:14:45 am
Hi

I was wondering if anyone has advice for desoldering very small smd components with nothing but a soldering iron. I have an unregulated ecg iron 20 watt and a hakko888d. and will i need a hot air gun if i try to take off surface mount ic's?

Thanks daniel
Yes.

Study this thread:
https://www.eevblog.com/forum/projects/how-difficult-it-is-for-hobbyist-to-work-with-smd-packages/ (https://www.eevblog.com/forum/projects/how-difficult-it-is-for-hobbyist-to-work-with-smd-packages/)
Title: Re: Desoldering
Post by: KL27x on May 01, 2016, 02:20:48 am
Depends on how big the package is and if you want the part intact.

It is fairly trivial to remove smaller IC's by flooding the pins with solder and removing the part while it's hot.

It is also totally possible to cut off the pins and then remove them one at a time. Or to melt the solder and lift the pins with a knife, one at a time.

Quote
very small smd
If you're talking about VERY small passives and SOT parts and the like, you can easily use the solder blob method for a lot of these parts. Or a knife (K) tip can be helpful for the passives.
Title: Re: Desoldering
Post by: sleemanj on May 01, 2016, 04:38:41 am
I highly recommend a hot air station if you work with SMD.  Just a cheap Chinese one is fine (check it for safety though), $50 to $100 and you have a tool which will save you so much hassle and time when you want to remove/replace a part on a board.

(I find) a hot air station is all but useless for actually assembling a board from scratch, use your iron for that, but for reworking, absolutely essential.
Title: Re: Desoldering
Post by: Skimask on May 01, 2016, 04:56:30 am
ChipQuik alloy is just Sn42Bi58 alloy, but at a very bloated price.
ChipQuik makes something like 20 different mixes.  Sn/Bi is just one type.

But, bloated price...Yes...

How can the O/P afford desoldering equipment is he's hard up for free equipment?
Title: Re: Desoldering
Post by: Skimask on May 01, 2016, 05:34:41 am
Thanks for the mention about the Sn42Bi58 alloy.  I remember reading about some low melting alloys applicable to electronics but I did not do any research about their particular availabilities.
Where do you commonly obtain such alloy for non bloated prices?  I recall someone mentioning about ebay sources for certain low MP alloys but I don't recall if this was the sort or not.
I don't.  |O  Made the mistake of buying a 50g container from Sparkfun before I figured out the stuff was seriously overpriced...as most of their stuff is.   |O  Or maybe that's the going rate for it.  I don't know.  Haven't looked lately.  That was almost 2 years ago though.  I haven't burned thru that 50g container yet.  I store it in the bottom of the fridge, let it warm up to room temp for a couple hours before I use it, throw it back in the fridge when I'm done.  Last fall, I mixed in about a dozen drops of liquid RMA flux after the paste seemed to not reflow so well.  Works well enough after the addition though.