AVR-Chat

----- Original Message ----- 
From: "Tim Mitchell" <tim@sabretechnology.co.uk>
To: <AVR-Chat@yahoogroups.com>
Sent: Monday, June 05, 2006 1:09 PM
Subject: RE: [AVR-Chat] One of >46 pin project


AVR-Chat@yahoogroups.com wrote:
>> Ryan wrote:
>>
>
>> If you've never seen it before, check out this video:
>>
>> http://region.bdmicro.com/smt1.mov
>>
>
> I had not seen that before, very tempting.
>
> If there was any sound on the video, I couldn' t hear it, so
> does anyone know what the 'pen' was?
>
> It looks like a highlighter, but clearly thats not the case.
> I assume it wasn't solder paste, as this regular solder was used.
>
> I assume therefore that it was flux, but then the iron was
> used to 'glue' the chip into place.
> I guess that must have relied upon the tinning on the PCB,
>
> Anyone any experience of this?
>
> What sort of thickness of solder is required. It looked about
> the same width as the pitch of the pins (or at least thicker than the
> width of a pin).
>

That's 'drag soldering'. It's easiest with a special tip like the Metcal 
mini-hoof which has a little depression to hold a small amount of molten 
solder, but it can be done with a conventional tip with a blob of solder on 
it. The secret is to use plenty of liquid flux. I use the technique with 
fine pitch devices like the Philips ARM chips (0.5 mm lead spacing).

Leon