Re: gEDA-user: Surface mounted circuits in hobby projects

[Steve Underwood <steveu@xxxxxxxxxxx>]

Peter TB Brett wrote:
> On Thursday 02 April 2009 08:32:09 Peter Carlsson wrote:
>   
>> Hello!
>>
>> I have just started my first hobby project with gEDA and
>> noticed that some circuits I need is only available as
>> surface mounted circuits.
>>
>> How do you handle this problem? Or is it a problem?
>>     
>
> It's not necessarily a problem -- it's actually not particularly hard to hand 
> solder SMT components, with a little practice.
>   
When you reach the age where you need reading glasses, the difficulty 
suddenly increases rather a lot. :-\

The girls (almost always girls) who assemble prototypes by hand for a 
living will assemble anything other than a BGA very quickly and very 
cleanly, mostly using a big fat soldering tip. Getting the central pad 
to solder on a QFN can be a challenge for them, though. Some like to use 
a huge iron and let a big blob of solder run down each side of a QFP or 
QFN, soldering the pins as it flows past. With practice they can clear 
away the surplus solder in seconds. Creating a huge continuous blob of 
solder around the four side is the strategy for removing a QFP. QFNs 
tend to be a pain to remove with an iron, because of that big central 
pad. It all comes down to learning the fine art of using the surface 
tension of molten solder to your advantage. Use a lot of flux. If you 
have high impedance circuits, like LCD segment lines, you'll need to 
clean that flux away really thoroughly as most modern flux is somewhat 
conductive. Getting it out from under the package can be a pain, though.

So, if your sight is good and your hands are steady you can assemble 
extremely small things very cleanly with some practice. Just don't be 
discouraged by the mess you'll probably make the first few tries. It 
doesn't take too long to start getting the hang of it.

Steve



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