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Using multiple component forms


pwdixon

I would like to layout a pcb with two processors (for sourcing reasons) with a BGA and a QFP format so that either chip can be sourced and fitted.  I have made a schematic with the two chips and connected all of the same pins to each other. 

The autorouter has never been able to track the BGA chip so I have had to layout the interwiring manually.

I have managed to wire the two chips completely but I want to know how I can use this compound part in my final design including a number of other components.

Is there any way to preserve these processor layout combination for future use as though it was a single library part?

The problem is that once wired to other components any subsequent unroute removes the inter processor traces too.

Also, when trying to autoroute component connected to the processor(s) some try to aim for the BGA part and cannot autoroute even though the QFP pins are readily accessable to the external components.  It looks like some random net end points are chosen that are on the BGA part and the autorouter doesn't realise the assessable pins are also on the net to be routed.

I suspect the autorouter is just too dumb to work these things out and I will be forced to manually route the entire board.

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