Hi Thomas,
I can't comment on you root problem with the resin coated copper shorts, but
I did have a quick thought on the SEM/EDX results you mentioned. The
bromine
signal (peak) is most likely coming from the flame retardants used in the
laminate.
The aluminum signal (peak) that you are seeing is also coming from the
bromine.
Bromine and aluminum signals overlap at 1.48keV on the EDX spectrum and
cannot be separated. However, bromine has additional lines (peaks) at 11.9
keV
that can be identified. So if bromine is present there is no easy way to
determine
if aluminum is present by EDX. You would need to use another analytical
technique
such as WDX, but that's another story.
Hope this helps,
Wade McFaddin
NEXTEK Inc.
> -----Original Message-----
> From: Thomi [SMTP:[log in to unmask]]
> Sent: Thursday, February 03, 2000 7:46 PM
> To: [log in to unmask]
> Subject: [TN] electrical shorts in RCC (resin coated copper) build up
> layer
>
> Dear Technetters,
>
> has anyone come across a root cause for electric shorts between
> neighboring copper lines of different potential within a layer laminated
> with RCC (resin coated copper)? We have carefully ground away layers 1+2
> from one side, and layer 4 from the other, to find a (ca.) 1 micrometer
> diameter filament connecting two neighboring lines in layer 3. Cross
> sectioning this further, we could analyse this filament by using SEM/EDX
> and found copper. The surrounding resin shows peaks of Bromium (probably
> from flame retardants) and Aluminum (??Al2O3 filler material??). The
> electric short was not detected during bare board testing, but occured
> within one week of functional testing of the full assembly in an
> environmental chamber operating at 120°C (I wouldn't believe it!).
>
> Is there a certain resin condition under which copper migration is
> enhanced within the RCC-resin (however close to the interface with the
> core to which the RCC is laminated)? There is a recommendation to ensure
> driving/baking out humidity from the multilayer, which makes me somewhat
> suspicious, but I don't know enough about the constituents (resin,
> hardener, flame retardant, maybe filler material) to try and explain what
> happens electrochemically.
>
> Best regards,
>
> Thomas Ahrens, Memellandstr. 8, D-24598 Boostedt
> Tel. ++(49) (0) 4393 97769 e-mail [log in to unmask]
> <mailto:[log in to unmask]>
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