I’m a beginner in BGA design and currently setting up my layout in KiCad. By default, KiCad had a 0.2 mm clearance but since I’m working with a fine-pitch FBGA**, I changed the default clearance to 0.07 mm to make routing under the BGA possible.
Now I’m wondering:
Is it okay to keep 0.07 mm clearance just for the BGA signal nets?
Or should I change the clearance back to 0.2 mm for non-BGA signals?
Right now, I’ve just globally changed the default to 0.07 mm, but I’m not sure if that’s the best way to handle it. Should I instead use net classes and apply 0.07 mm only where it’s needed?
Any suggestions or best practices would really help. Thanks
This might be a “What is your goal?” question. Strictly speaking, if you’re paying for 0.07mm anyway, you can use it. But if you only need tolerances that tight in a few places, it might be far more manufacturable to not specify things that tightly anywhere else.
The default clearance in KiCad was 0.2 mm, but I couldn’t route traces between the BGA pads with that setting. To meet the design requirements, I reduced the clearance to 0.075 mm (3 mils). However, I’m concerned that such a tight clearance might cause crosstalk issues, especially in the fan-out region outside the BGA.
Would it be acceptable to use different clearance values—like 3 mils inside the BGA and 0.2 mm outside? I don’t know the general practice for this kind of situation. Should I keep BGA signals at that clearance and use a different clearance for non-BGA signals? Any guidance would be appreciated
Yes you can use 3mil clearance (on external layer) inside the BGA and once the trace is fanout then you can increase the trace width as needed. Only thing you need to consider the copper thickness on external layer ( 0.25OZ foil + Plating) to have clearance of 3mils.