Sorry for rehashing the obvious but am trying to get the problem.
There is copper migration after thermal cycling on top of Gold. The gold
thickness varies from 1 to 0.1 um and Nickel shows porosity.
If it is electroplated Ni/Au - it is not necessary to find Cobalt. However
it is unlikely to get 1 um and 0.1 um on the same board in electroplating.
Max 0.1 to 0.2 um.
If ENIG we could have LPISM residues which obstructed ENI and lead to
porosity and uneven Gold deposit and hence failure. (cannot comprehend
chemistry behind what George says of high gold where nickel skips and copper
available - but if the guru says it must be).
To me the problem in either case is unclean base or a terribly unbalanced
ENIG.
Anil Kher
micro interconnexion pvt. ltd
D3-12A, Corlim Industrial Estate
Corlim, Ilhas , Goa , India 403110
tel: 91-832-2284209/337. fax 2284209/2285271
e mail: [log in to unmask]
Leaders in Gold plated PCBs - selective/ cob
an ISO 9001-2000 Company
-----Original Message-----
From: Lee parker [mailto:[log in to unmask]]
Sent: Thursday, October 19, 2006 1:53 AM
Subject: Re: ENIG problem
This could very likely be Flash Gold which is electroplated gold and nickel.
If this is the case, all of the outer traces will be plated with soft gold
over nickel; the soldermask will rest on the gold coating. You may want to
have the supplier's local rep have cross sections made of the traces at a
lab of your choosing.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: "Hfjord" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 18, 2006 11:58 AM
Subject: Re: [TN] ENIG problem
> Not one single count of Cobalt.
> Inge
>
>
> ----- Original Message -----
> From: "R Sedlak" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, October 18, 2006 1:09 AM
> Subject: Re: [TN] ENIG problem
>
>
> > Ingemar:
> >
> > I have a suspicion you may have found the answer...
> > Thick gold can only mean electroplated gold... electroplated gold is
> > often alloyed (think Cobalt is most common alloying metal)... which
> > undoubtedly would make bonding difficult.... remember, in
> > electroplating gold, pure gold is often referred to as "soft
> > gold".... the alloying metals are present to harden the gold...
> > which has to interfere with bonding...
> >
> > And from the comments about appearance, it may well not be well alloyed.
> >
> > Rudy Sedlak
> > RD Chemical Company
> >
> > "Ingemar Hernefjord (KC/EMW)" <[log in to unmask]> wrote:
> > Hi amigos,
> > I should never said that we had no ENIG problems. Now we seem to
> > have one. Chinese board supplier. Problems with heavy wire aluminum
> > bonding on the ENIG pads. Too low pull test values. Possible reason:
> > pad surface invaded by copper particles after the
> > bake/reflow/mounting. Sending picture to Mr Yoda. Never seen this
> > before. Gold is too thick for being ENIG (>1um), Nickel about 6um.
> > Can't see how Copper could diffuse to the surface so rapidly and at
> > those low temperatures which are typical for a general assembly
> > process. Any clue? Graham? You seem to be sitting at the keyboard just
now.
> > Ingemar Hernefjord
> > SAAB MICROWAVE SYSTEMS
> >
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