Mr. Willard,

	It is my understanding that a black oxide process that is not well controlled may 
promote excess dendritic growth of the (oxide) crystalline structure.  The longer crystals are more 
likey to break off during the lamination process due to shear stresses related to the parameters of 
the resin system interacting with the micro obstructions of the copper thickness and the etched 
design AND the stability and flatness of the platens of the press.

	At the sites of the broken dendrites there is an increased probability of micro voids 
which, when intersected by a drilled hole, would promote excess wicking of electroless copper 
(and/or other chemicals in the process stream).  This condition can result in blow holes, voids, 
and/or pink ring.  It can also shorten the life of the PCB by creating a lateral path to adjacent 
uncommon conductors, which will ultimately result in electrical shorts when filled with certain 
chemicals that promote a conductive dendritic growth.  Each step of the process that subjects 
the PCB to thermal or mechanical stress can increase the chance of this occurring.


Fred J. Paul, Sr. Process Engineer
PCB Operations, FLUKE CORPORATION
direct:  206 356-5734  fax:  206 356-6070
[log in to unmask]	


On Wed, 24 Apr 1996 11:13:00 -0700 [log in to unmask] wrote:

> From: [log in to unmask]> Date: Wed, 24 Apr 1996 11:13:00 -0700
> Subject: Effects of poorly controlled Black-Oxide process
> To: [log in to unmask]
> 
> 
> 
>         I am aware of the importance of a well controlled copper 
>      oxidization process to promote good inner layer adhesion for 
>      multi-layer PCB's. It has been brought to my attention that a weak 
>      copper oxide layer (maybe the crystal structure is too long) may cause 
>      electrical problems on the inner layers as the structure crumbles in 
>      the lamination stages, possibly creating a time-bomb scenario with 
>      shorts forming later when electrically stressed.
>      
>      
>         Has anybody out there experienced this phenomenon or do you know of 
>      any articles or papers on the subject.
>      
>                 Regards  Gary Willard
>                          Motorola (UK)
>                          E-mail [log in to unmask]  
>