Re: RE: SMD soldering?

From: André Fachat <afachat_at_gmx.de>
Date: Sun, 01 Nov 2009 13:49:43 +0100
Message-ID: <20091101124943.202010@gmx.net>
Hi Scott,

I'm soldering SMDs onto newly made PCBs (my own design, for some new boards of my selfbuilt 6502...) The PCBs got solder resist (solder mask, Lötstopplack) on them, I didn't trust myself enough to not use it...

I did solder the other ICs with 1.27mm pin distance (74xxx logic, RAM) with a small soldering iron and small solder and it worked fine.
Even with traces running between the pins. I did use a magnifying glass though... :-) (and some desoldering braid(?) to get superfluous solder away).

Only the other ICs I have are even smaller. I'm new to soldering with flux, but it seems I'll have to give it a try.

Thanks for your advice!
André

-------- Original-Nachricht --------
> Datum: Sun, 1 Nov 2009 07:27:52 -0500
> Von: "Scott" <rylos@charter.net>
> An: cbm-hackers@musoftware.de
> Betreff: RE: SMD soldering?

> Andre'
> 
> Make sure the glue that held down the old IC is removed, you can do this
> by
> over curing it with your soldering Iron. Then prep the pads, use flux and
> leave a small amount of solder on the pads. This solder will make the
> joint
> for you.
> 
> I then tack down opposites corners of the IC using just enough solder on
> the
> iron to make it conduct. If the IC's pins are not bent most of the other
> legs will fall in place. If they don’t, carefully move them over with a
> sharp pointed object, I usually use an Explorer (dental tool).
> 
> Once you have everything aligned. Soak the pins will a good flux. I still
> prefer rosin flux because no clean evaporates too fast. Now, hold the pin
> down with the Explorer and touch it with your Iron. If you have enough
> flux
> on the leads you shouldn’t have to worry about bridging the pins. So
> don’t
> be overly concerned about touching more than the leg you want to solder. 
> 
> Once everything Is tacked down, clean then reapply flux and re-solder
> using
> the explorer to get that clean finish. Then take the explorer or exactor
> knife and carefully run it between the legs of the Ic to make sure there
> are
> no bridges. Observe with a magnifying glass. Clean again and your done. 
> 
> Of course make sure you bounce back and forth when soldering, left side of
> the chip to the right side, this way you won't overheat the IC. And most
> important, your Soldering iron tip temperature should turn to a nice
> golden
> brown after solder is applied. If it turns the flux in the solder black
> then
> you are way to hot. 
> 
> Anyway, all steps are important. But To answer your question, I normally
> just tack down the corners first. 
> 
> -----Original Message-----
> From: owner-cbm-hackers@musoftware.de
> [mailto:owner-cbm-hackers@musoftware.de] On Behalf Of "André Fachat"
> Sent: Sunday, November 01, 2009 06:31
> To: cbm-hackers@musoftware.de
> Subject: SMD soldering?
> 
> 
> Hi,
> 
> I know some of you do SMD soldering. I did already solder 1.27mm distance
> packages, but now I have to solder some 1.0 or .8mm pins - and I find it
> quite difficult to position the SMD part correctly. I only have normal
> pincers as help. I solder one pin and by resoldering that pin I can
> actually
> correct the position before soldering the other pins - but that seems
> difficult with those smaller parts.
> 
> What do you use to position those SMDs? Do you have vacuum pincers /
> airpicks (or whatever they are called)? Or do you use other tools? Like
> glue
> to keep the part in position when positioned? 
> 
> Any help appreciated
> 
> Thanks
> André
> 
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