[hpsdr] Favorit soldering method ?

[Kjell Karlsen]

Hi Rob.

We had a project in the local Radio Club building an APRS Tracker (Polaric  
Tracker) and used a reflow oven for soldering. There were a lot of  
components on the PCB and after 1,5 hours the paste did not stick to the  
PCB and it was difficult to place the components correctly. May be the  
paste was not good but we ran into problems.

When I built my 2 Hermes Beta boards I had to add some liquid flux to the  
paste to get it a bit more soft. Without a Pick-and Place machine I spent  
at least 5 hours to place all components and also now the paste dried and  
it was difficult to have the components to stick to the pads.

I agree that to use an oven for soldering is the best method. The stencil,  
at least a laser cut is quite expensive but if there are many builders  
that can use them it may be done.

73, Kjell







På Sat, 10 Mar 2012 01:34:15 +0100, skrev Rob Frohne  
<rob.frohne at wallawalla.edu>:

> 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
>>
>>
>


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