[sdiy] SMD soldering video

[Eric Brombaugh]

On Mar 5, 2007, at 8:44 PM, Dave Manley wrote:

>> John Mahoney wrote:
>>> I just saw this video on soldering an SMD using solder wick:
>>>      
>>> http://www.makezine.com/blog/archive/2007/03/ 
>>> smd_soldering_video.html
>>>
>
> Ive seen this before and I've got to totally disagree with this  
> method.  What a waste of solder and solder-wick.  I've soldered  
> hundreds of fine pitch surface mount parts (240PQFP for example) and  
> there's no need to do it this way.  Instead put the tip at a right  
> angle to the pins so you can touch multiple pins with the tip at a  
> time.  Apply solder to the tip and pins and drag the tip and solder  
> down the remaining pins, continually adding solder as you go.  You  
> basically drag a blob of solder across the pins, relying on the  
> surface tension of the solder to maintain the blob, and the wicking  
> action of the solder to make a good joint.  With a little practice it  
> is easy to do and you'll have very few solder bridges.  To make it  
> really easy apply liquid flux to the pins and use very small diameter  
> solder.
>
> Their method of pre-loading the tip or the solder-wick with molten  
> solder completely negates the value of the flux in the solder.   
> They've vaporized the flux without it ever contacting the surfaces to  
> be soldered.
>

I'd tend to agree - it seems pretty wasteful.

I've been able to solder 0.5mm pitch parts (up to QFP80 so far) without  
too much trouble. The trick I use is pre-tinned PCB pads and a dab of  
liquid flux. Position the part, tack two opposing corners, apply a drop  
of flux and then merely heat the pads. The pre-tinned solder on the pad  
will melt and the flux cleans the surface, allowing it to flow to the  
part leads. This give an extremely clean joint with no excess or  
bridging. The main difficulty is cleaning the excess flux off  
afterwards, but an old toothbrush and some isopropyl seems to do the  
trick.

The main advantage of the Spark-Fun technique seems to be that they can  
do it very quickly without giving each lead individual attention.

Eric