[hpsdr] Favorit soldering method ?

[Rob Frohne]

Hi Kjell,

What problems have you had with leaving solder paste around on a board a 
long time?  I haven't experienced any, but I haven't on purpose left it 
sitting out for a long time.  I have left the solder paste sitting out 
for weeks without any problems.  Also, you can do multiple re-flows if 
needed, but you have to cut your stencil up.  I can't make anything half 
as nice as the re-flowed solder connections by hand.  We use homemade 
stencils that are made on an LPKF engraving machine.  You can see a 
couple of videos of my student using an ordinary toaster oven here 
<http://www.youtube.com/watch?v=TCWVUdBO0kg>.

I think we need to make these techniques more well known so that more 
people will attempt and succeed on home made boards.

73,

Rob
KL7NA

On 03/08/2012 02:58 PM, Kjell Karlsen wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> 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
>
>

-- 
Rob Frohne, Ph.D., P.E.
E.F. Cross School of Engineering
Walla Walla University
100 SW 4th Street
College Place, WA 99324
(509) 527-2075			http://people.wallawalla.edu/~rob.frohne

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