[sdiy] Starting with SMT hand-soldering

[Oren Leavitt]

On 10/28/2010 6:33 PM, Dave Manley wrote:
>
>
>
>   On Thu 10/10/28  1:58 PM , "Jason Tribbeck" jason at tribbeck.com sent:
>> On 28 October 2010 21:47, Dave Manley  wrote:
>>
>>   On Thu 10/10/28 12:17 PM , "David G. Dixon" dixon at interchange.ubc.ca
>> sent:
>>>> I'd like to try my hand at laying out and
>>> hand-soldering an SMT board and>  thought I'd stop in here to see what
>> advice I
>>> could get from those that>  have done it.
>>>
>>> Go see Rick Moranis about getting yourself shrunk...?  :o)
>>
>> Short of doing that:
>>
>> For chip resistors/caps: holding the part with the tweezers, solder down
>> one end.  Move on to the next component, only soldering down one end of
>> all the caps and resistors, then make a final pass soldering the other end,
>> and touching up as necessary.  Some people will object to this, but I find
>> this is the fastest.
>>
>> For leaded ICs: solder down one corner, then solder down the opposite
>> (diagonal) corner.  If all the leads aren't perfectly lined up on the
>> pads, adjust the corners until you get it right.  Then solder all the
>> other leads, using lots of solder flux, dragging the wetted iron while
>> applying more solder, solder all the leads on one side in a single pass.
>>   With practice you can get very good at this and not need to do much touch
>> up, or cleanup with solder wick.  There's no reason to solder one lead at
>> a time!  Don't do it!  :-)
>>
>> This reminded me of something: I use a pair of tweezers which are normally
>> closed for the resistors/capacitors, which means you don't get too tired
>> doing a lot of them. But I also only solder one side at a time (I also try
>> to tin the pads in the same orientation so I don't need to spin the PCB
>> around too many times).
>>
>> The technique for chips described above does work very well, but it did
>> take me a while before I was comfortable doing it - for a while, I found it
>> easy to do 1.27, but difficult for 0.8, and then easy for 0.65 and smaller.
>> I think it's because the 0.8mm is close to my soldering iron tip size, and
>> I couldn't drag the solder properly. However, after a bit of practice, I
>> think I've got it cracked.
>
> The other thing I like to do when putting down chip resistors/caps, is to put a little bit of solder on one of the pads first.  Then you only need two hands to put the part on - step one put the solder on, step two with the tweezers slide the part into the pre-soldered pad that you're heating with the soldering iron.  If you pre-load one side of all the component pads with some solder, then assembly goes much faster.
>
> -Dave

That's what I do, too - after going all over the map for a decent way to 
hand-solder SMT parts.
A little touch of Kester 331 solder one pad for each part. Place part, 
press down on it with a toothpick, heat the soldered pad to pin the part 
in place.
After all parts are "pinned", solder all remaining leads.
Wash the 331 flux off. Nice clean board with no glue or stickum.
Done!

I have a Weller/Ungar 921ZX needle-point adjustable temp soldering iron 
(found in a thrift store for $10) that does this job nicely.

- Oren