Having looked at the plethora of responses on this problem, I would like to
ask some simple questions.

1) Your construction is very high in resin content. Have you measured your
expansion rate (ie ppm in z axis > Tg) of the substrate? (I'm going to stick
my neck out and predict 420ppm)

2) Does the DESIGN of the board use inner layer pads on EVERY layer or only
some of the layers?

3) Have you seen this problem on other products or only this part number?
Are you successfully building significant volumes of similar product
structure types? 

Dave Rooke
Circo Craft - Pointe Claire

_____________________ reply separator __________________________
> i give below some more information on the defect.
>
> we use permanganate desmear and direct metalisation process which requires
>microetch as last step .we do fullpattern plating after imaging. for inner 
>layer adhesion we use reduced blackoxide.
>
>The construction :
>
>______________   1/2 Oz cu
>
>--------------   1080
>--------------   1080
>_______________   0.008         Required thickness  1.6 m.m + / - 0.2 m.m
>
>---------------   1080
>---------------   2116
>---------------   1080
>
>_______________   0.008
>
>---------------    1080
>---------------    2116
>---------------    1080
>
>________________    0.008
>
>----------------    1080
>----------------    1080
>
>________________     1/2 Oz cu   
>
>we use FR 4 nominal Tg of 140 deg c.no mix up of different prepreg and inner
>core has happened.
>
>The microsection looks like hole wall pullaway with maximum separation at
>center of hole  and minimum near inner connect.The connection in the hole is
>between 
>2nd and 7th layer only.
>
>thanks in advance. 
>
>
>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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