Inge,
I have used the SST vac/pressure reflow system for criters similar to this. Here is their web site - http://www.sstinternational.com/prod_3130.html
The cost back then was ~$150K. Not sure what they are up to now.
The base unit had the capability of 50-100mT vacuum, or 2-3 atm of pressure [gas of your choice] and all points in between. Programmable rise, hold and fall rates [within reason], multiple gas flows and rates.
You likely saw a very small sample of some of the high lead and Au/Sn with LTCC configurations permitted with this equipment.
Heating of components is accomplished by conduction from graphite tooling plates - the tooling plates being heated by passage of electric current within a sealed chamber.
On my unit, I could not plumb in more [more concentrated] than a forming gas [5-6% hydrogen], however. That might be barely suitable for oxidized nickel [we never used fluxes inside the chamber] if you can get the temperatures high enough [if your components can withstand them] to actually activate the hydrogen's reduction effect. At 300-400°C, or below, a good clean nitrogen appears to work just as well from a practical experience standpoint.
You have left out a lot of details, possibly the nature of the beast at this point, however. Are you dealing with matched, or compression seals? Have a clue for what the max temp capabilities are so that a reflow hierarchy can be established?
Doesn't sound like you could use 280°C Au/Sn eutectic very will with the possibility of oxidized Ni, but it just may work if you can clean things up well prior to reflow. My assumption is that you desire something stronger/better than Sn/Ag eutectic, or generic hi-temp lead bearing alloys.
In theory the newer SST's [1000°C max temp capability] can handle the generic Cu/Ag eutectic at ~780°C, but I did not have the opportunity to go that high.
When using the Cu/Ag eutectic, the Kyocera's & NTK's of the world seemed to always go to the cracked ammonia atmosphere tunnel kilns. I never got to play with the 25% hydrogen atmosphere, like the 'big boys'.
Corporate had an 'Astro' batch furnace that could get there, however.
There are various other 'active braze' alloys containing titanium that will fire in these temperature ranges, but I believe they will like to be in the cracked ammonia environment as well.
Lastly, if you believe the advertising [I have some swamp land to sell, if you do] you could buy some epoxy and make a "hermetic" seal !! - just kidding.
You come up with all the fun stuff!
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Wednesday, September 24, 2008 10:26 AM
To: [log in to unmask]
Subject: [TN] Soldering SMA to heavy RF packages, need advice
TNetters godday.
Target is very large metal packages with bright nickel finish. Imagine soldering hermetic feedtrues. Nickel needs higher temperature and longer exposure time than copper, silver, gold and other metals. Vapour phase soldering is maximum 218 Centigrades, which I believe is not high enough. Iron soldering is not practical for launches. IR oven could be an idea if we add protection gas. Hot gas stations (Nitrogen)seem to be too lame. Resistance soldering not tested, unknown for SMA. Torch heard of, ought to be impractical, will burn flux and miscolor package. Laser soldering not practised.
Anyone out there with experience from this kind of soldering?
Inge
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