The following track layouts can be used to realise defined impedances. Please note that these values only provide a basic orientation. Interference factors such as angles, meanders or vias in the routing of the tracks may have a negative effect on the intended impedances.
Looking at the 4L HD stack-up picture above I’m confused/concerned (accurate loss and trace-trace coupling calculations) about the true thickness of the outer copper layers. It says 18um copper foil, but a processed thickness of 40um. How does 18um become 40um? Surely your ENIG coating isn’t 22um thick.
Speaking of ENIG, Nickel is magnetic and causes considerable loss in high-speed/high-frequency signals. Is there a way to order WITHOUT ENIG coating?
The final copper thickness of 40 µm is the result of the 18 µm base copper of the copper foil plus approx. 22 µm copper, which is applied by the electroplating process.
Pardon my ignorance on PCB manufacturing.
Am I correct then in assuming this 22um Cu plating being the result of the same (electroless) plating process that creates the PTH vias?
Hello Aisler team,
do you have recommended W and W/S for the most popular transmission lines impedance, such as SE45, SE50, Diff85, Diff90, Diff100, possibly based on past experiences with this stackup or, even better, real world measurements?
Those numbers would be very helpful.
Correct, this effect is due to differences in the thickness of the solder resist. The electroplating process builds up tracks and surfaces with additional copper. However, this build-up does not occur completely evenly across the entire width of the track/surface. Thus, any copper structure has more a trapezoidal or dyke-like shape in cross-section rather than a rectangular shape. On the slopes, the solder resist has less adhesion and therefore forms thinner.
Hallo!
I’m looking into making a 4 layers board, and I have questions regarding vias. Is it possible to make a via that links only two contiguous layers (for example, on KiCad, F.Cu and In1.Cu)?
Hi there for the defined impedance table, could you also list the type of transmission line?
Like, is it a micro-strip, or a coplanar wave-guide with ground for example?
