Michael, I have no experience and 2 ideas:
1)  Use a higher temperature solder for the aluminum-teflon interface 
than that used to attach components;
2)  Use one of those Metcal soldering irons which have RF heated tips and 
don't get hotter than the solder melt temperature to attache components.
Lou Hart  


.

On Wed, 29 May 1996, Michael J. Chmela wrote:

> Hello all:
> Do any of you have experience in automated soldering of SMT parts onto teflon
> type PCBs already soldered to an aluminum carrier?
> 
> The PCB is either a Rogers RO3006 or Arlon EPSILAM-10 material that is reflowed 
> to a tin plated aluminum carrier (up to .5"x15"x15") using solder paste. 
>  The configuration is reflowed under clamping pressure to prevent voids between
>  the PCB and carrier. Afterwards, the SMT parts are soldered by hand.  This 
> process was choosen as a
> less costly method than procuring the PCB already attached to the carrier
> material and subsequently machined.
> 
> The question is, how do we keep the soldered interface (PCB/carrier) intact
> while the SMT parts are reflowed?  My concern is that if we switch to a higher
> temp solder for the interface to solve this problem, we will have problems with
>  the PCB material after being exposed to that extreme temp. and
> have problems with the oven at those elevated temps.  Cooling will also be a
> problem, because of the mass. 
> 
> Any comments from anyone with experience on this would be appreciated.
> 
> 
>