Another design finished from the start.
Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Friday, May 09, 2008 7:44 AM
To: [log in to unmask]
Subject: Re: [TN] Fw: [TN] Brittle FPC Tracks

You should never (ever) finish a flex in ENIG that is needed to bend in
the
plated area it will crack - there is no spec for this combination of
board
and finish= if flexed it will crack - period.

I presume you have full body enig.

Change the specification to a different finish

 
 
John Burke
 
(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Friday, May 09, 2008 7:22 AM
To: [log in to unmask]
Subject: Re: [TN] Fw: [TN] Brittle FPC Tracks

Still looking for answers to this problem...
Can anyone tell me if there is an IPC standard which covers requirements
for
FPCs i.e. how much they should be able to bend before cracking.
It appears that it is the Au and Ni which are cracking first.  The
plating
is ENIG.
Also I own a copy of Soldering in Electronics (Wassink) - can anyone
recommend a similar comprehensive text for PCB (PWB) manufacturing
including
details on flexies...
Thanks,Neil>----Original Message----> From: [log in to unmask]>
Date:
May 2, 2008 1:05:53 PM> To: [log in to unmask], [log in to unmask]>
Subj:
Re: [TN] Fw: [TN] Brittle FPC Tracks> > 
>OK - I don't know much about this FPC - it is 3-4 suppliers back in
the
chain, still working my way back...
>I do now know that there is actually a Ni Layer (3microns thick)
with
3microns of Au on top.  The copper is 34microns and the crack on one
part
(as I have received it) goes through the Ni and about 25% of the way
through
the Cu.
>I will try to get a photo to Steve.
>Neil>>>----Original Message---->> From:
[log in to unmask]>> Date: May 2, 2008 11:41:12 AM>> To:
[log in to unmask], [log in to unmask]>> Subj: Re: [TN] Fw: [TN]
Brittle
FPC Tracks>> >> Hi Neil,>> Indeed, Au over Ni will
result
in diffusion. However, while AuSn IMC is indeed brittle and weak and
weakens
the solder structure, I do not know whether Cu-Au is particularly
brittle.
it would also be very thin. Ni barrier would stop the Au diffusion, but
brings with it a whole new set of problems, among which are a thicker
possibly equally brittle Ni layer, Black Pad with too muc P, Ni
'hyper-galvanic' corrosion with too little P, etc.>> My question
about
your problem is-have you determined whether the Cu is not brittle
itself. If
you use un-annealed rolled Cu, it will be brittle in the cross-rolling
direction.>> >> >> >> Werner>>
>>>>>>**************>>Wondering what's for
Dinner
Tonight? Get new twists on family favorites at AOL Food.>>
(http://food.aol.com/dinner-tonight?NCID=aolfod00030000000001) >

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