Re: Hybrid PCB stack-up -- Rogers + FR4
I don't know what your design requirements are so I can't say if your layer stack is the ideal choice or not. Normally, I would choose 0.020" Rogers 4003 up at several GHz because the metal losses are lower than for 0.008".
Also, I don't know how big your PCB is. Normally, I work alongside a dedicated PCB designer who lays out a PCB for my RF design under my supervision. The PCB designer also talks to the PCB manufacturer and takes advice about choosing the best layer stack. Also they can advise me as to the issues with warping. Having an asymmetric layer stack on a large PCB is a risk for PCB warping and so is having an imbalance in the copper distribution (per layer) after etching.
So often the layer stack can change part way through a design due to feedback from either the PCB designer or the PCB manufacturer. The manufacturer can advise about cost implications for buried/blind vias etc.
I think it just affects the risk of warping especially during solder reflow. But you really need to discuss your design with the PCB manufacturer to assess the risks of warping. If your board isn't very big then it might be OK :)
Will such asymmetrical stack-up affect the performance ?
Hope this is useful to you.
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