Hi Guys, we still lid a fair number of Ni/Au packages and our standard Au thickness on lid seal area would generally less than the 2.5um we specify on the pins for wirebonding, so I'd expect about 1-1.5um on the seal face, certainly no more than 2um. Largest flat lid we weld is 0.015", but more usually 0.010". We don't use stepped lids. We use both electroplated and electroless Ni on packages - thickness on lid seal area would be typically 4 microns, lids are electroless Ni and we use a 7 degree electrode angle. 0.020" lid thickness for seam seal welding is a challenge, good welding on thicker lids usually requires a fair load on the electrodes (we use 8lb) to prevent the heat being generated totally at the electrode/lid interface and this is where most seam seal welders fall down in or experience. We would expect total fusion of the Ni on both the package and lid and effectively a braze to the kovar.
Hope this helps
Ian Fox
Lead Materials and Process Engineer
Goodrich ECS
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: 13 March 2007 16:38
To: [log in to unmask]
Subject: Re: [TN] Seam resistance pulse welding
Ingemar,
There was a day that I could just rattle that right off for you ...
... don't use it ... ya loose it!
Will have to see if I can find any notes at home.
It seems that if one component were electroplated [package], the other would be electroless [step lid]
3.8 - 6.4µm was the nickel plating thickness range.
I believe that we would plate the lid whether it was kovar or nickel for roller welding.
My recollection is that the angle was extremely low - like 9° or less.
I will have to dust off many boxes to see if I can find further details :-)
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Tuesday, March 13, 2007 10:08 AM
To: [log in to unmask]
Subject: [TN] Seam resistance pulse welding
Hi,
Anyone who's guru at this? Lids=nickel plated 0.5 mm thick Kovar.
Package= goldplated over nickel plated Kovar.
We have He leakage problems due to porous and brittle welds. I suspect that
a)the 3-4um gold plating on the package is not metallurgically correct, at least, ought to be much thinner, let's say like flash gold.
b)too thin nickel on the package, just 1 um, should be 5um or more.
c)package shouldn't have electrolytic nickel, but electroless nickel, because the later has 300 Centigrade lower melting point, and moreover, is not so brittle (HV300, while EN can be HV1000)
Qs :
what nickel plating do you prefer?
What nickel plate thickness? (Welding, or rather brazing, is nickel-to-nickel, Kovar should not be involved)
What wheel angle? 9, 12, 15 or what degrees?
Thanks in advance
Inge
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