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April 2001

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Subject:
From:
Mike Fenner <[log in to unmask]>
Reply To:
Mike Fenner <[log in to unmask]>
Date:
Tue, 24 Apr 2001 17:56:14 +0100
Content-Type:
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I smiled at the joke in your post, typed out stannum and then as so
often happens just as I hit the send button on stannum I wished I
hadn't. ... Someone as erudite as you  already knew the answer, unlike
me on this.
Titanium is used in etching machines so I would have thought it was
pretty resistive to most things, probably what you want is not a
straight acid but a buffered blend where the pH is low enough to
remove Ni, but not low enough to remove the Ti. (Most likely you  will
get a different rate of etch so also you will want a good stop watch).
Whether this window exists and how it might be achieved without
experimentation I don't know, possibly not.
A more recent/practising chemist could probably advise this, or
someone who has done it before. If the 'netters don't know either
suggest try a pcb chemical / plating supply house, or maybe someone
from front end. Ericcson used to have an ASIC foundry in I think
Gothenburg, they would most likely  know.

Mike


----- Original Message -----
From: "Ingemar Hernefjord (EMW)" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 24, 2001 10:16 AM
Subject: Re: [TN] Embrittlement


> Dictum factum, as they say in Northumbria when the cows go mad on
the pub, and can't see the difference between Isle of Jura and Johnny
Walker. If you are so alert, Mike, perhaps you can also give me the
recipe for best etching away Nickel without damaging Titanium. Is wet
possible at all? I'm trying to find ESD damages in the dielectric of
0.5x0.5 mm MOS caps. Have removed bond gold, and want remove 1000 A
nickel without taking underlying Titanium simultaneously. Step- by-
step analysis is  important in this case. Top of the selective etch
list for Ni, Pt, Cr and Ti would be grate. I have experimented with
most common acids, but not found really good selective soups. I don't
talk fine etching for grain studies but stripping.
> Ingemar
> PS. No,Mike, milk did not work so good.
>
> -----Original Message-----
> From: Mike Fenner [mailto:[log in to unmask]]
> Sent: den 24 april 2001 09:03
> To: TechNet E-Mail Forum.; Ingemar Hernefjord (EMW)
> Subject: Re: Re: [TN] Embrittlement
>
>
> Stannum
>
> Mike
>
> ----- Original Message -----
> From: "Ingemar Hernefjord (EMW)"
<[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, April 24, 2001 7:31 AM
> Subject: Re: [TN] Embrittlement
>
>
> > another one falling into #2 is me. Gold is Aurorum, Silver is
> Argentum, Lead is Plumbum, but what was Sn? Was it Senilium?
/Ingemar
> >
> > -----Original Message-----
> > From: Wenger, George M (George) [mailto:[log in to unmask]]
> > Sent: den 23 april 2001 19:46
> > To: [log in to unmask]
> > Subject: Re: [TN] Embrittlement
> >
> >
> > Bev,
> > It's only a tough question if 1). You didn't have a metallurgy
> course or 2).
> > you start to get old and forgetful.  I didn't take #1 but I know a
> lot about
> > #2.  I think Dave, like the rest of us, is starting to fall into
#2.
> >
> > I think he meant to tell you AuSn4 and AgSn3 not Au4Sn and Ag3Sn
> >
> > Regards,
> > George
> > George M. Wenger, DMTS Bell Laboratories Princeton
> > Supply Network Solutions
> > PO Box 900, Princeton NJ 08542-0900
> > Route 569 Carter Rd., Hopewell, NJ 08525
> > (609)-639-2769 (Office), 3210 (Lab), 2346 (Fax)
> > [log in to unmask]
> >
> >
> > -----Original Message-----
> > From: David Hillman [mailto:[log in to unmask]]
> > Sent: Monday, April 23, 2001 12:54 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Embrittlement
> >
> >
> > Hi Bev! There is a fairly large set of industry data on the solder
> joint
> > reliability problems induced by Gold/Tin intermetallic  (Au4Sn)
> formation
> > and a smaller data set on the solder joint reliability problems
> induced by
> > Silver/Tin intermetallic  (Ag3Sn) formation.  See Klein Wassink's
> book ISBN
> > 0-901150-24-X. I would expect that if you have both intermetallic
> species
> > in a solder joint it just would not be a "good" thing. The use
> environment
> > of the assembly would also play a role in just "how much"
> intermetallic
> > degradation would be allowable. Tough question - good luck.
> >
> > Dave Hillman
> > Rockwell Collins
> > [log in to unmask]
> >
> >
> >
> >
> > Bev Christian <[log in to unmask]>@IPC.ORG> on 04/16/2001 08:33:58
> AM
> >
> > Please respond to "TechNet E-Mail Forum." <[log in to unmask]>;
Please
> respond
> >       to Bev Christian <[log in to unmask]>
> >
> > Sent by:  TechNet <[log in to unmask]>
> >
> >
> > To:   [log in to unmask]
> > cc:
> >
> > Subject:  [TN] Embrittlement
> >
> >
> > Good morning!
> > Here is a met. question to start off the day.
> >
> > We know that if we have over 4% gold in a 63/37 tin lead solder
> joint we
> > risk gold induced embrittlement because of the production of a
> significant
> > amount of the tin/gold intermetallic.  It is also common practise
to
> use a
> > slight variation of the eutectic solder with a 62/36/2 Sn/Pb/Ag
> > composition.
> > We also know that gold and silver are 100% soluble in each other.
> My
> > question: if the final tin/lead based solder joint composition has
a
> > COMBINED noble metal percentage in the 4% range how bad is that
for
> solder
> > joint reliability?
> >
> > regards,
> > Bev Christian
> > Research in Motion
> >
>
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