From One Engineer to Another

Au/Sn – One of a Kind

Wednesday, January 23, 2008 by Jim Hisert [Jim Hisert]

For those of us who recommend solder alloys, Au/Sn holds a place in our hearts. In many cases it is the #1 solder for an application (if you don’t factor cost into it). Although the cost of the alloy rules it out of many applications, sometimes it just can’t be replaced or substituted. It’s that good!

It MEMS packaging, Au/Sn is perfect for Au-Au soldering. The nature of this alloy allows flux-less reflow and strength that is unmatched in the world of solders.

For high-temp (formerly high-Pb temperature) applications, 80Au/20Sn is the only proper Pb solder replacement. As you would expect – this alloy can also be made in preforms, paste, and other forms to replace high-Pb alloys

For us tech guys, I guess recommending Au/Sn is a little like working at a car dealership and letting people test drive a high-end car. If you’re into solder, it just feels good to know someone is using the “Cadillac” or “Ferrari” of solder – Au/Sn

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Comments for Au/Sn – One of a Kind

Sunday, April 13, 2008 by Kyooseok Kim:
I want to know the u-Sn paste Particle size.
Sunday, April 13, 2008 by Kyooseok Kim:
I want to know the Au-Sn paste Particle size.
Monday, April 14, 2008 by Jim Hisert:
Thanks for the interest! The particle size for Au/Sn paste is dictated by the customer. Common applications use type 3 (25-45 micron), type 4, type 5, and type 6 (5-15 micron) powder sizes.
Thursday, September 4, 2008 by Mickael POMMIER:
Do you have more details or information of AuSn spheres soldered on Ni surface. Thks
Thursday, September 25, 2008 by Jim Hisert:
Hi Mickael, This is very common indeed. The magic number is 350 for processing Au/Sn-here’s why: Below 350degC you should use a flux. Tacky fluxes are best for holding the spheres in place. TacFlux 007 is used most for this operation. Above 350degC a flux will not work, that’s the point where you want to reflow the spheres in a forming gas atmosphere. You wouldn’t use a forming gas atmosphere at lower temperatures because it starts full activation at ~350degC. I hope this helps!

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