Edwards, Ted A (AZ75) wrote:
> 
> Sounds like you have interplane separation.  It is a separation of the
> plated copper on the hole wall from the edge of the inner layer.  Dr. Alan
> Poskanzer wrote an article in Plating and Surface Finishing for March 1990
> that you might want to read.  It's title is IP Separation: Its Causes and
> Cures.  The magazine is by the American Electroplaters Society.  Since we
> are on the subject, I'd like to piggyback on this and ask:  Is anyone seeing
> post separation of the Tg 170 range materials and if so do you have a root
> cause?
>  ----------
> From: [log in to unmask]
> To: [log in to unmask]
> Subject: Interconnect Failure
> Date: Monday, November 18, 1996 8:17AM
> 
> RECENTLY WE FIND INNER LAYER OPEN COMPLAINT IN EIGHT LAYER BOARDS FOR ONE
> PARTICULAR PART NUMBER. ON MICRO SECTIONING WE FIND NO INTER CONNECTION
> BETWEEN HOLE COPPER AND INNER LAYER (SEVENTH LAYER).
>   THE CONSTRUCTION 1,2,7 & 8 ARE SIGNAL LAYERS REST ARE GROUND LAYERS.
>   TWO TO SEVEN ( INNER LAYERS HAVE ONE OUNCE BASE COPPER) ONE AND EIGHTTH
> LAYER
> HALF OUNCE BASE COPPER.
>    COPPER INSIDE THE HOLES IS >25 MICRONS. WE DONT FIND ANY WEDGE VOID OR
> PINK RING.
> 
>   THE CUSTOMER BAKES THE BOARD BEFORE ASSEMBLY AND ALL BOARDS PASSED
> ELECTRICAL TESTING. BUT AFTER ASSEMBLY THE CUSTOMER REPORTS INNER LAYER
> OPEN.
> 
> CAN ANYONE THROW LIGHT ON THE ABOVE PROBLEM?
> 
> Thanks in advance
> 
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Most probably the cause is drill smear or epoxy smear as it is called by 
some. an IP connection with smear is weak and will separate under thermal 
stresses. This failure mechanism has been discussed in many many papers 
in the past. IPC has also published information on smear caused fails.
-- 
Pratap Singh
Tel./Fax: 512-255-6820
e-mail: [log in to unmask]


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