If Buehler’s PC-MET and PWB-MET targeted grinding fixtures are being used, it is essential to set the total grinding distance using a reference pin. As illustrated in the diagram, this distance is established at 0.150” in the standard equipment.
Reference Pins for Targeting Through Holes in PWB
By grinding to diamond stops in the fixture, the perfect target is achieved. It is of utmost importance to set up the diamond stops precisely. To do this, a dial gage is used. To target grinding to the specific plane before polishing to the center of target hole, it is necessary to set up the Dial Gage to the correct distance. The target plane is set to the center of holes when the Dial Gage is set at zero with a reference pin of known value.
Reference Pins to Set Up Dial Gage
Targeting Through Holes in Printed Wiring Boards (PWB) – Use of Reference Pins
To set the Dial Gage zero, a standard distance of 0.150” needs a reference pin of 0.1972” diameter. Various reference pins can be used to set up the Dial Gage for other distances.
This is calculated as follows:
Half the value of 0.094” diameter index pin (0.047”) + the distance from Reference holes to Target holes.
It is recommended to set the diamond stops to specific values to ensure that the grinding surface plane remains above the target plane and will not pass beyond the center. Normally, these values are 7 mils for the ‘Long Stop’ (first grinding step) and 3 mils for the ‘Short Stop (second grinding step).
Buehler carries PC-Met and PWB-Met Wiring Board preparation systems along with pins. For further information click here.
This information has been sourced, reviewed and adapted from materials provided by Buehler.
For more information on this source, please visit Buehler.