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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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