Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Gold/Tin Reflow

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AK

#72328

Gold/Tin Reflow | 27 June, 2014

Is it safe to let Au80Sn20 reflow twice? What I am saying is, for example, die attach using Au80Sn20, followed by lid seal using same Au80Sn20 solder, will it create any problem on the die which was first attached using same soldering material?

My first thought was after Au80Sn20 reflow for the first time, it mixed with gold from the mating side, thus changes its composition and raises its melting point, is this correct?

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#72330

Gold/Tin Reflow | 27 June, 2014

Is this fluxed / solder paste or flux-less reflow process? Are you soldering in a nitrogen or vacuum oven? From my experience having gold-tin connections go through reflow a 2nd time does not yield defects or quality issues. However, I cannot comment on the impact of long term reliability in these instances.

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#72332

Gold/Tin Reflow | 27 June, 2014

For lid sealing, a seam seal machine will be used which produces only localized heat on the joint, so any components inside the package soldered with Au/Sn will be unaffected by the final process. [ http://www.coininginc.com/files/admin/english_gold_tin_paper.pdf ]

BR ... davef

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AK

#72342

Gold/Tin Reflow | 30 June, 2014

Thank you SteveO, I have also tried reflow 2nd time without any problem, but I also do not know the impact of long term reliability as our devices are most likely operated in the harsh environment.

We are currently do soldering in Argon environment.

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AK

#72344

Gold/Tin Reflow | 30 June, 2014

Thanks davef for you comments and attached paper, I will investigate seam seal machine with environment control, since we would like to fill our devices with inert gas during capping process.

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