Real-time control of via stub drilling depth asymmetry

A gang drilling machine for drilling a circuit card, the machine comprising:

• an n master drill and a p master drill forming a pair configured to be aligned in registry with a respective n test via and p test via of the circuit card;
• the n master drill associated with a plurality of n minion drills and the p master drill associated with a plurality of p minion drills, the plurality of n minion drills and the plurality of p minion drills configured to be aligned in registry with a respective plurality of n live vias and a respective plurality of p live vias of the circuit card;
• and
• a controller that is electrically connected to control operations of the n master drill, the p master drill, and the associated pluralities of n and p minion drills, transmits and receives electrical signals from the circuit card, wherein the controller is configured to:
• send an electrical query signal to the circuit card, wherein sending the electrical query signal comprises sending an n query signal to the n test via and sending a p query signal to the p test via;
• monitor an electrical response signal from the circuit card, wherein monitoring the electrical response signal comprises monitoring an n response signal from the n test via and monitoring a p response signal from the p test via;
• determine a drilling depth of at least one of the master drills, in response to a comparison of the response signal to the query signal, wherein determining the drilling depth comprises:
• measuring a stub length time skew between the n response signal and the p response signal;
• and
• determining a stub length offset between the n test via and the p test via, in response to the stub length time skew;
• and
• adjust operation of the gang drilling machine, in response to the drilling depth, wherein adjusting operation of the gang drilling machine comprises increasing the drilling depth of the at least one of the master drills and the plurality of associated minion drills, in response to the stub length offset.