As PCB designers we all know that for high frequency signal (MHz), we should design return path (reference GND plane) underneath the signal as follows:
https://www.allaboutcircuits.com/technical-articles/better-pcb-design-return-paths-impedance/
Consider that we have a digital chip or analogue chip that we want to design the PCB for driving he chip. In side the package there is die and wire bonding connected to the package pins as follows:
https://www.iue.tuwien.ac.at/phd/poschalko/node39.html
My question is that there is no return path for the wire bonding inside the package (there is no ground reference plane underneath the wire bondings), so even if we consider this return path on the PCB for the signal which is produced by the chip, in the signal source (die and wire bonding) there is no return path. I'm trying to understand why there is no return path inside the package? if we consider this return path is crucial for signal integrity.