Cadence PCB Best Practices

Working with Backdrilling in Allegro PCB Designer: Best Practices Learn more at Cadence Online Support https://support.cadence.com © 2014 Cadence Design Systems, Inc. All rights reserved worldwide. Page 12 Applying the Minimum Pin Plating Property The BACKDRILL_MIN_PIN_PTH property can be applied to the symbols or pins using Edit Property (Edit > Properties). It prevents Backdrill passes from removing a stub based on the relation between the depth range and the "Must Not Cut Layer" using the following criteria: • If the lower surface of the "Must Not Cut Layer" (Connection Layer) is outside the minimum pin plating depth, backdrilling will occur to eliminate the stub. If not, the layer pair will be shifted down one layer so that backdrilling can occur. • If the lower surface of the shifted "Must Not Cut Layer" is outside the minimum pin plating depth, backdrilling will occur to eliminate the stub. If not, the pin will be flagged with a "P" symbol, indicating a stub exists but the pin could not be backdrilled due to the plating restriction. The PCB Designer, when assessing the P code violations, is advised to: • Consider rerouting the signals on other layers to reduce the stub length while maintaining the minimum pin plating requirements. • Consult with Engineering and discuss the possibility of increasing the value of the BACKDRILL_MAX_PTH_STUB property on the affected nets. • Create a new backdrill pass set to accommodate the targeted layer to backdrill to. • Apply the BACKDRILL_OVERRIDE property to a layer that satisfies the min pin plating requirement, treating the stub violations as acceptable. Property BACKDRILL_MIN_PIN_PTH Purpose Ensures minimum pin plating depth is not compromised Usage Optional Value Depth from side component is placed (database units) Objects Symbols, Pins Backdrill analysis flag P

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