is there a way to force some of the parts in DxD ,using a property or somthing like that
to be placed in PCB on Bottom side only
No there isn't, if you think it would be a useful option post an enhancement request on Ideas: Mentor Ideas for xDX Designer
Vern posted an interesting option on the Ideas page which I will repeat here:
'Another Option would be create a Cluster property for the parts and then to Cross probe to the PCB Database and use Component Explorer to define the Part Placement options for Bottom Placement.'
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