Perhaps the annular ring would be used to protect the dielectric from
fasteners or other hardware.
>
> Thanks People;
>  But why would one care about annular ring on a non-plated hole?
> IPC-D-275 Table 5-11
> IPC-2221 Table 9-2

################################################################
DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
To unsubscribe:   SIGNOFF DesignerCouncil
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################