Hello,
I am encountering issues when updating a footprint and its padstacks in Allegro PCB Designer version 17.2 for Windows 8. This is for a footprint with a fairly specialized application. I am creating the land pattern for a 32 pin QFN device where, instead of assembling the part on an exterior layer, we will be milling away a cavity post PCB lamination where the footprint will become exposed on an internal layer. Since SMD pins in the Pad Editor are only offered for the Begin and End layers, I need to create this padstack using a thru pin pad. My thought is to pick an unused drill size that I can remove from the drill file later, define the internal pad shape and the top pad that will be milled away--much like a blind via. The bottom layer will be undefined since I will have routing on this layer.
I am able to successfully define and update such a pad for the center thermal/ground pad of the QFN; however, the peripheral lead pads of the QFN will not update to include the internal layer pads that need to be populated to connect the device. I am using the following command sequence to update symbols: Place->Update Symbols->Package Symbols->[Device of Interest]->Refresh. I have also tried checking the "Update symbol padstacks from library" option with no success. Additionally, I have double checked my pad path to ensure that duplicate pads have not been defined in the various libraries I have included. Nothing is working. Attached are images of the Pad Editor for the pads I'm using. Any thoughts or ideas would be greatly appreciated!!
Cheers,
Vipul
QFN Ground pad that successfully updates to include the bottom and internal layer.
QFN lead pad that will not update to include internal layer
