Doing the design process of IC Package Layout

Hi,
Could you please let me know that IC Package Layout Design be it a SIP/MCM using any technology like WB or FC, can the design process be done independent of foundry who manufactures package provided I have foundry design rules available for that particular package or should it be designed in direct contact with foundry? or should the package design should also be done by foundry?
- what would be the best approach (self design or foundry design)?
- What types of issues we may be encounter if it's designed isolated and send the gerber to foundry for packaging
- Is their any cost advantage. If yes what whould be the difference in terms of percentage?
Any help.
Know.

Hi,
*There are couple of tools available for doing IC Package layout like Cadence APD, Sigrity UPD etc.
*And IC package layout can be anything like WB as well as FC, this is as per our requirement w.r.t electrical performance, cost and nature of DIE.
*Yes, for doing IC Package design, you need Foundry rules and Substrate Manufacturer rules like pcb manufacturing and its better to have direct contact with subcons
* Prior experience required to do IC Package layout as well as subject to availability of tools, So the best approach is as per our convinence.
* I think with the help of having Foundry/Manufacturer rules, Package layout can be carried out successfully and can send the gerbers to foundry for packaging
* No Idea about costing

Regards
Pras