The main course of satellites found around solder joints after reflow
soldering comes from moisture that is trapped in and/or stirred in the
solder paste before using it.
And again the main course is a jar with solder paste or cartridge that
has not been conditioned to room temperature when used. When the paste
is too cold, moisture in the air condensates on the paste when opening
the jar or using the cartidge..
A 500 grams jar needs at least 4 hrs conditioning, a 75 grams
cartridge needs 2 hrs.
A standard does not prevent satellites, only describes tests and
evaluates the reflow results.
Soft Soldering Processes
Peer Langeveld, Consultant
The Netherlands
2007/2/7, Dehoyos, Ramon <[log in to unmask]>:
>
>
> One way to mitigate the problem of solder balling is to bake the boards for 30 minutes at 70 deg C or store them in a dry room or box prior to processing. Also slow down the reflow process to, once again, dry the board and components to prevent the steaming of the humidity in vias or in the paste which is believed to create solder balls. The ideal environment that I have heard the most is 70 deg F, 70% humidity. That much humidity lessens ESD. Based on the records that we keep, air conditioning does not allow more than 68% humidity in the building we work during the summer and a lot less in the winter. That is due to the fact that when air is cooled, humidity condenses on the air conditioning system. On J-Std-001D 4.2.2 it says: Temperature and Humidity/ When humidity
> decreases to a level of 30% or lower, the manufacturer
> shall verify that electrostatic discharge control is
> adequate, and that the range of humidity in the assembly
> area is sufficient to allow soldering and assembly materials
> to function correctly in the process, based on vendor recommendations
> or documented evidence of process performance.
> ****For operator comfort and solderability maintenance***,
> the temperature should be maintained between 18°C
> [64.4°F] and 30°C [86°F] and the relative
> humidity should not exceed 70%.
> For process control, more restrictive
> temperature and humidity limits may
> be required.
> So if you are in an air conditioned building, keep the material dry and adjust the reflow process, the problem should be very small.
> Ramon
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Wednesday, February 07, 2007 2:58 AM
> To: [log in to unmask]
> Subject: Re: [TN] Max Humidity allowed
>
> Surely that depends on the chemistry of the paste, the hold time before and after the component assembly and before reflow, as much as the RH?
>
> Brian
>
> Sklenar Vit (RBAU-AE/MFE3) wrote:
> > Hi Techneters,
> >
> > Please is anybody aware or can you refer me to any standard which
> > addresses the maximum allowed humidity in electronic production in
> > order to prevent microballs creation during reflow process?
> >
> > Thank you fro your reply
> >
> > Vit Sklenar
> > Robert Bosch (Australia) Pty. Ltd.
> > RBAU/MF33 - VS, Process Eng.)
> > www.bosch.com.au
> >
> > Tel. +613 9541 7734
> > Fax +613 9541 3909
> > [log in to unmask] 2
> >
> >
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