Hi all,

I design layouts for flip chip process.  The pad pitch is 200um and stud bump height ~50um.  I would like to know if there is any requirement on the flip chip pads coplanarity. That is, is there any specification for difference in max and min copper pad heights on pcb board within the 4 sides of the chip?  I have not been successful in finding any information regarding this area on the internet.  How tolerant is the stud bump process in flip chip?

Also, do you recommend soldermask under the flipchip?


Regards,
Stella


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