Joy, Stephen C wrote:

>      Does anyone know of a non destructive way to measure the
>      dielectric spacing between L1 and L2?
>
>      Thanks,
>      Steve
>
> ################################################################
> TechNet 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 TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################

  Hi, TechNetters!
Undoubtedly, the manufacturer's information and, the impedance
measurements are good. Cross sectioning is the most accurate way.
Stephen wants to perform a non-destructive test, and we don't know if it
is for lack of time or equipment.
I dare to suggest an "exotic" way which may be rather quick if he has
an X-Ray at hand.
1. If you have a coupon from the batch, you ca cut a thin slice and take

a picture at the max. magnification with all the layers at 90 degrees .
Then you can measure the distances between layers and calculate the real
numbers knowing the real overall thickness of the board.
2. If you have no other possibility, put your board at an angle and try
to adjust your viewing angle till you see a through hole entirely.
Compare the distance between the outer pads with the distance between
the first layer pad and second layer pad.Recalculate knowing the
thickness of the circuit.

Is this crazy  and not accurate? It depends on your needs.
Gaby

################################################################
TechNet 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 TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################