[hpsdr] Favorit soldering method ?

[Kjell Karlsen]

Hi Roland.

The "best" solution is to use a reflow oven but there is one drawback: The  
method to apply the solder paste is very important. In my opinion the only  
way to do it properly is by using a Laser Stencil but then you run into  
another problem: You have to place all components on the PCB before it  
goes into the oven. It takes too long time to do this as the paste dries  
too fast. You do not have much more than one hour available and that is to  
short time for all the components. It is possible to use the stencil and  
apply paste only on the IC´s and other difficult components and solder  
only those in the oven. Afterwards it is easy to install the rest manually  
one by one.

I have a reasonable priced hot air soldering station (AOYUE Int2738) and a  
Quartz Infared Pre-heating Station (AOYUE INT853A). You find one vendor in  
England. You must also buy the right nozzles for the IC´s but they have  
all in stock. I start to place all the IC´s correctly and solder 2 pins  
diagonally. When I am sure they are correctly placed, i apply a narrow row  
of paste along the pins on all sides. Use very little of paste but it is  
easy to remove the excess solder afterwards using a dry, clean soldering  
iron or a narrow solder wick. Be careful so no paste gets under the IC.  
When all the IC´s are in place put the PCB on the pre-heater, set it to  
250 deg.C and wait until this temperature is reached (after 1,5-3 min).  
Then use the hot air tool to heat each component until you see the solder  
melt. It is best to do some training on a scrap PCB and old IC´s. I did  
some practices on old PC cards (Old VGA and Audio cards are fine) first by  
removing the IC´s and then solder them back. I use the pre-heater also to  
remove the parts.

In fact there are only a few of the components on Hermes (LTC2208 and  
LTC6400) that are difficult to solder manually using only a soldering iron  
with a narrow tip (0,4 mm). I have found that it is easier to get good  
results when using higher temperatures than normally advised (350 deg.C)  
and I also prefer a small 80W iron (Weller WSP 80 or equivalent). With  
this the soldering process goes much faster and also introduce less stress  
to the components. The tip must be kept clean all the time and DO NOT USE  
LEAD LESS SOLDER! In my opinion it is a disaster.

One tip when using Solder Wick to remove excess solder: Apply fresh flux  
to the wick before use, it is much more efficient then.

I have built 2 Hermes Beta that has been in use for nearly 2 years and at  
least one of them will be dismantled and the expensive components  
installed on a new PCB. I may keep one just for fun but I do not think the  
software for the USB version will be updated.

Enjoy the work and I hope to meet you on the band with Hermes in both ends!

73, Kjell






På Thu, 08 Mar 2012 21:45:24 +0100, skrev roland etienne  
<roland.etienne at free.fr>:

> Hi,
>  I’ve been lucky to get an Hermes PCB, and I am now collecting all the  
> components. I am wondering what is your favourite method to solder all  
> the ICs and oscillators: iron, hot air or refusion oven ?
> Surely, I will buy an hot air station, any model recommended ?
> I would like to make some test with a refusion oven, any advice? Is it  
> possible to do several passes ?
>  Thanks for any comments,
>  73, Roland F8CHK


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