Ed,
   I would be concerned about my internal layer connection.  All the 
Z-axis thermal stresses are now borne by the innerlayer connections.  

Example:  A Plated thru hole is like a rivet.  The top and bottom pads 
constrain epoxy board material which is expanding at 50+ ppm per degree 
faster than the epoxy.

In your design, the rivet has only one side.  You should expect the 
rivet/ plated barrel to start up pull out. This will cause your 
innerlayer connection to be intermittent opens.  

The only place you can get away with this is on 2 layer boards.


On Nov 13,  8:04am, [log in to unmask] wrote:
> Subject: ASSY - Padless Plated Thru Holes
> 
>   To extend clearance and eliminate potential shorts to the bottom
> of a connector, the component side pad must be reduced to zero.
> In other words,a top side padless PTH. The shorts are occuring during
> wave solder.
> 
>    What reliability down sides can we expect? Im advised that PCB
> fabrication will not be a problem. Im mostly concerned with assembly
> and repair operations.
> 
>   Parameters: .093", 14 layer board
>                Finished hole .033" with solder side pad at .060"
>                No external layer traces or connections.
>                All connections are internal planes.
> 
>  Thanks in advance: Ed Cassinelli 
>                     Stratus Computer Inc
>                     508-490-6821
> 
> [ Attachment (application/rtf): "ASSY" 3107 bytes
>   Encoded with "base64" ]
>-- End of excerpt from [log in to unmask]



-- 


George Franck Jr
Raytheon E-Systems
Product Assurance Engineer
Falls Church Va

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