One point: please check whether your FAb vendor use
HTE copper foil for inner layer, especially layer 5.
--- Ken Patel <[log in to unmask]> wrote:
> What are the causes of the internal crack on only on
> layer 5? Most of the
> cracks found were on via holes extending into the
> laminate (no
> delamination!). Prepreg used at layer 5 is 3 sheets
> of 1080 of FR406 (these
> 3 will give a total of .008" thickness to overall
> thickness of .093").
>
> Loaded boards failed at ICT that prompted us to do
> some investigation. What
> should I do as an OEM customer on my own as my fab
> house and assembly house
> won't take responsibility easily. Following
> information may help you
> understand my board structure.
>
> # of layers: 12
> SIG/GND/SIG/GND/SIG/3.3V/VCC/SIG/GND/SIG/GND/SIG
>
> 1oz copper used on all layers except first and last
> which plated to 1oz final.
>
> re,
> ken patel
>
______________________________________________________
> Ken Patel                       Phone:  (408)
> 490-6804
> 1708 McCarthy Blvd.             Fax:    (408)
> 490-6859
> Milpitas, CA 95035
>
>
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