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February 2011

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Subject:
From:
Ioan Tempea <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ioan Tempea <[log in to unmask]>
Date:
Thu, 17 Feb 2011 12:07:08 -0500
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Bonjour Cédric,

Maybe you should try playing with the finishes. The first question coming through my mind is why Ni/Ag on top of the Al? Ni wets slower than Cu, so why not going for a Cu/Ag plating on the Al...? Also, Cu instead of Ni might help the RF performance. Maybe you should also try tinning the Ni/Au of the component.

Bonne chance,

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] 
W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Cedric ORAIN
Sent: Thursday, February 17, 2011 6:26 AM
To: [log in to unmask]
Subject: [TN] Voids issue on Aluminium base plate

Dear Technetters,

We have to solder a RF power transistor onto an aluminium base plate and
we
are facing with a very challenging issue.

We encountered a high voids rate (>30% or 40%) underneath the component
body
(which is about 35x10mm). This is not acceptable for this application.

The component is Nickel/gold plated whereas the aluminium baseplate is
plated with Nickel and Silver and then cleaned with solvent.

We tried to change/adapt:
- soak time of the profile, 
- 2 difference solder pastes (SAC305), 
- change the screen design and thickness

Finally none of these parameters looks to have significant effect on
voids
rate. We are now wondering if the solderability of the Ni/Ag plating is
good
enough and even if it is convenient for that purpose.

Is somebody could give us advises? How to enhanced NiAg plating
solderability (acid ?!, ...)? Which flux could help to compensate the
poor
wettability? Which kind of plating would be preferable? ...

Thanks and regards,

Cedric



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