I forgot to add, even if the nickel is there, if it is extremely porous it =
can allow copper migration in certain cases.
-----Original Message-----
From: Stadem, Richard D.=20
Sent: Wednesday, October 26, 2011 1:18 PM
To: [log in to unmask]; [log in to unmask]
Subject: RE: [TN] Discoloration on plated over vias
Hi Vladimer,
Nickel skip is extremely bad, but not all that rare. I have seen this happe=
n several times over the years, and it has nearly always been some type of =
contamination preventing the nickel plating from occurring, most commonly i=
n via-in-pad designs like the ones in Ioan's pictures. The via fill materia=
l is either left on the pad, or the planarization process was not done prop=
erly in most but not all of the cases I have seen. And in every case, the c=
opper diffusion reacting to the gold creates the bright amber/orange deposi=
t, which I have become accustomed to seeing with this type of fabrication i=
ssue.
But only some type of comprehensive evaluation can prove it.
-----Original Message-----
From: vladimir Igoshev [mailto:[log in to unmask]]=20
Sent: Wednesday, October 26, 2011 12:08 PM
To: Stadem, Richard D.; [log in to unmask]
Subject: Re: [TN] Discoloration on plated over vias
That was exactly what I'd also suggest but from my understanding, some of t=
he sectioning had been done already and at least some information can be pu=
lled out from them.
Honestly, I'd be skeptical about the idea of Cu diffusion, unless the layer=
of E-Ni is EXTREMELY bad.
Vladimir
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: "Stadem, Richard D." <[log in to unmask]>
Date: Wed, 26 Oct 2011 11:55:22=20
To: [log in to unmask]<[log in to unmask]>; [log in to unmask]
<[log in to unmask]>
Subject: RE: [TN] Discoloration on plated over vias
A set of microsections directly through some of the affected pads will reve=
al the thickness of the nickel, and may also reveal information on any hole=
-fill epoxy smear, lack of planarization, or other fabrication issues that =
may have caused the root problem; inability to plate the nickel properly.
The way to do this is to microsection the edge of the pad, wet-etch in weak=
acid, coat in hard, clear epoxy, photograph, microsection again further in=
to the pad, repeat the process and photograph again, etc., until you have a=
t least 4 sectional views.
Most good analysis shops can do this for you.=20
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Wednesday, October 26, 2011 11:42 AM
To: [log in to unmask]
Subject: Re: [TN] Discoloration on plated over vias
Hi Ioan,
Careful EDS may be able to tell.=20
Vladimir
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: Ioan Tempea <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Wed, 26 Oct 2011 12:21:14=20
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
Ioan Tempea
<[log in to unmask]>
Subject: Re: [TN] Discoloration on plated over vias
Once again, thanks everybody for the replies on my problem below.
=20
I got one more question:
What test method would indubitably determine if the orange spots are Cu tha=
t surfaced?
=20
Thanks,
=20
Ioan Tempea
=20
=20
=20
=20
Dear Technos,
=20
I got this issue, see http://ipc-technet.groupsite.com/gallery/21662
=20
So 6 layer, 2oz Cu per layer PCB, epoxy filled vias and plated over. After =
assembly we see 4-5 vias having reddish stains, on most boards. Had it anal=
yzed, no trouble with via integrity, no cracks in cover plating, no migrati=
on of fluids from inside out. FTIR does not detect any surface contaminatio=
n.
=20
Au plating thickness stands at 2.09 micro inches.
=20
Nothing special detected in the stains, so the lab concluded what we see is=
an optical effect due to a certain roughness of the Cu. The logical conclu=
sion is no issue, cosmetic defect.
=20
However, our end customer, high reliability, want to know what the stains a=
re and want absolute confirmation that long term reliability is not affecte=
d. Also, we've been warned that no such issues will be tolerated on future =
lots.
=20
My questions to your infinite knowledge is: have you seen this before? How =
can I convince the customer everything is OK? What is the root cause and ho=
w can I get rid of the issue?
=20
Many thanks,
=20
Ioan Tempea, ing.
Ing=E9nieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]> =20
W | www.digico.cc <http://www.digico.cc/>=20
LogoSignature_Courriel
Signature_Courriel_arbreN'imprimer que si n=E9cessaire - Print only if you =
must
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