Working with Backdrilling in Allegro PCB Designer: Best Practices
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Pressfit Connectors
Under normal circumstances, the backdrill code will not backdrill pins from the same
side a connector is placed on. The exception to this rule might apply to pressfit
connectors. Pressfit connector pins are spring loaded or forced into the PCB, making
contact with the barrel of the hole in a specific range. A stub can result from both sides
of the board up to but not including either the trace and/or the contact range. The
following illustration shows an actual pressfit pin and how a trace entering just above
the contact range results in stubs for both the top and bottom side of the PCB.
Pressfit Connector
Tool Tip – The backdrill code will attempt to remove as much electrical stub as
possible, regardless of the BACKDRILL_MAX_PTH_STUB value, but only backdrill to the
layer before the connection layer and not into the adjacent dielectric layer. The
fabrication vendor can continue backdrilling through the adjacent dielectric layer and
stop as close to the connection layer as possible.
