I have never experienced the results you mentioned, but I keep your?
information in mind, I don't postpone the soldering phase often.

I did it a couple of times because after putting some of the parts?
and emergency came up and had to abort. I placed the board in a zip?
locked bag in the refrigerator and continued the next day. As a norm?
I very slowly ramp the preheat temperature precisely to get rid of?
moisture. On those boards I did a very long and slow warm up cycle?
since the boards were cold, all the joints were soldered just fine.

Soldering paste doesn't have a very long life in commercial outfits?
but using manual paste application I have solder paste that work?
quite well after two years, the commercial environment requires the?
paste density to be in a very strict range in order to be?
automatically applied, manual procedures can accept a larger variance.

I did one experiment where I place a partial parts count and?
re-flowed the board, I then did it an additional two times and was?
surprised that the components were all fine after some of them were?
re-flowed three times, since then I've read some have done as many as?
six times but I think you are pushing your luck doing it that many times.

I've bought the components to make an automatic controller for my?
Infrawave Oven once that is done then repeatability will improve, and?
I can work on other boards while the first batch is proceeding on?
auto pilot. I'm thinking of using it for commercial projects.

At 11:35 PM 4/17/2014, you wrote:
>Cecil,
>
>You're playing with fire when you wait for reflow,
>The solder paste is VERY sensitive to moisture, and the flux?
>evaporate fairly fast.
>So, you end up with crusty paste that might hold the parts a bit, but you are
>almost certain to create cold solder joints, and tons of solder balls.
>At all the places I have worked, 6 hours was the shelf life of a?
>board with solder paste and parts.
>Past that time, the PCB was washed and recycled because it was the?
>most expensive part.
>The paste and the inexpensive parts were trashed. Some (very few)?
>very expensive ICs were recycled.
>
>I understand the hobbyist viewpoint, but please don't suggest that?
>it is an acceptable practice.
>
>I would suggest to place a few parts and reflow them, then you can?
>wait, then add fresh solder paste, place parts
>and reflow those.
>Too many reflows are not good for ICs, but 3 to 4 is OK.
>So you can limit the number of reflows by adding heat screens on?
>your board for the parts already soldered
>(aluminum foil makes a good screen)
>
>My $0.02
>
>Jean-Paul (AC9GH)
>
>
>On Apr 17, 2014, at 11:03 PM, Cecil Bayona?
><<mailto:cbayona@...>cbayona@...> wrote:
>
>> From personal experience I've had no problems with putting the
>>paste and parts and then soldering a few days later, what happened
>>was that some of the binding oil evaporated but the parts were held
>>in place by the dried out paste. When placed in the oven the parts
>>were soldered OK.
>>
>>It would not be OK if you put the paste but not the parts, when you
>>go to put in the parts later they would not stick to the pad.
>>
>>At 08:53 PM 4/17/2014, you wrote:
>> >
>> >
>> >I am planning the build of an Ensemble RX and I am thinking of
>> >trying the griddle-heat gun reflow method to install the SMT parts.
>> >As far as blocking out time to apply the solder paste and place
>> >individual parts, how long can one let the applied parts stand
>> >without reflow? I would like to break the placement process up over
>> >several days but I am worried that the solder paste will separate or
>> >otherwise degrade if I don't place all the parts and reflow them in
>> >the same session. Can the process be broken up over a period of days
>> >or even a couple of weeks without ruining the already placed parts?
>> >John Stockman, KC2THY
>>
>>--
>>Cecil - k5nwa
>><?
>><>?>?
>><??>
>>
>>Never take life seriously. Nobody gets out alive anyway.
>

--?
Cecil - k5nwa
<??> <??>

Never take life seriously. Nobody gets out alive anyway.?