Introduction to PCB Controlled Impedance:
Connect two electrical devices (“driver” and “receiver”) for transferring signal power.
An increase in impedance will result if neighbours switch with the same polarity (Zoe, even mode). Conversely, a reduction in impedance will be sustained when the signal on a neighbouring trace switches with opposite polarity (Zoo, odd mode), resulting the potential effect of ghost signal and signal overlap and on overall product quality.
This needs extra attention when board traces carry high frequency. In this case, care must be taken to smooth a signal and to design traces matching the impedance of the driver and receiver.

The main factors affecting PCB Controlled Impedance are as follows:
* Dielectric thickness (52%);
* Dielectric constant (21%);
* Trace width/ space (18%);
* Copper thickness (6%);
* Solder (green) thickness (3%)…etc.
 
Calculating controlled impedance:
According to Polar’s multiple dielectric field solving controlled impedance design, there are three impedances: single ended impedance, differential impedance, and common mode impedance.

Depending on the calculations for inner and outer PCB layers, the selection of impedance (see diagram 1) and the controlled impedance calculations (see chart 1) may vary as described below.

To achieve accuracy of the actual controlled impedance, each PCB factory makes PCB boards with reasonable adjustments during the manufacturing processes. For example, when we edit CAM working files, we would add adjustments ensuring the good performance of etching and copper coating can be done. By doing so, we can prevent any potential effects on trace width/ space, as well as the differences from the actual product design, resulting manufacturing requirements cannot be met.

Diagram 1:





Chart 1:

Abb.	Definition	Characteristic Impedance	Controlled Impedance Testing
W / W1	Upper/ Lower Trace Width	(Inverse): the smaller trace widths, the higher the series resistance.	Per user prefs.
S	Separation	(Direct): the larger trace space, the higher the series resistance.	Per user prefs.
T	Trace Thickness	(Inverse): the higher copper thickness, the lower the series resistance.	Per actual product thickness.
H	Height	(Direct): the higher dielectric thickness, the higher the series resistance.	The general adjustment for controlling impedance; typically from 2.2mil~ 9.0mil.
H1	Height 1	(Inverse): the higher solder thickness, the lower the series resistance.	0.4mil ~ 0.6mil (In general).
Er	Dielectric Constant  (Characteristic of Thin-core material)	(Inverse): the lower the dielectric constant, the higher the series resistance.	Different dielectric materials lead to discrepancies between calculated and measured impedance values (i.e.: FR4 with dielectric constant ranges from 3.94 ~4.8).

JetPCB’s recent productions associated to PCB controlled impedance testing:

Actual Product Photo	Specification	Stack-up
	Layers: 10L Thickness: 1.4 mm       Finished Copper : 1.0 oz Board Size: 230mm*268mm Surface Finish: Immersion Gold 3µ" Min. Trace / Space: 3.5mil/ 3.5mil Smallest Hole: 0.2mm Special Specification: Controlled Impedance: Total of 14 Single-ended 50ohm: 3.5, 4, 5mil Differential 100ohm: 4/5, 4/12, 3.5/11mil Single-ended coplanar 50ohm: 5/5/5mil Differential coplanar 90ohm: 8/5/5/8mil Differential coplanar 100ohm: 8/4/5/8mil
	Layers: 8L Thickness: 0.8mm       Finished Copper: 1.0oz Board Size:  41 mm*57mm Surface Finish: Immersion Gold 3µ" Min. Trace / Space: 4mil/ 3mil Smallest Hole: 0.1mm Special Specification: BGA  10mil/ Resin Plugged Blind and buried vias: L1~L2, L8~L7, L2~L7 Controlled Impedance:  Total of 3 Differential 70ohm: 8/7mil Differential 100 ohm: 4/9mil
	Layers: 6L Thickness:1.0 mm        Finished Copper t:1.0oz Board Size: 222mm*217mm Surface Finish: Immersion Gold 3µ" Min. Trace / Space: 3mil/ 5mil Smallest Hole: 0.2mm Special Specification: Controlled Impedance: Total of 11 Single-ended 53ohm: 3.5mil Single-ended coplanar 50ohm: 12/6/12mil Differential 90ohm: 3.5/5.5mil Differential 100ohm: 3/7.5mil
	Layers: 4L Thickness: 1.6 mm      Finished Copper: 1.0 oz Board Size: 297 mm*208mm Surface Finish:  Immersion Gold 3µ" Min. Trace / Space: 4mil/ 4mil Smallest hole: 0.3mm Special Specification: Blind and buried vias:L1~L2 Controlled Impedance:  Differential100ohm :4.3/4mil,
	Layers:4L Thickness: 1.6mm       Finihed Copper: 1.0 oz Board Size: 318mm*405mm Surface Finish: HASL pb free Min. Trace / Space:  4mil/ 4 mil Smallest Hole: 0.2 mm Special Specification: Controlled Impedance:  Total of 4 Single-ended 50ohm: 4.5mil Differential 90ohm: 5.3/5mil Differential100ohm: 4.3/5mil
	Layers: 8L Thickness: 1.6mm        Finished Copper: 1.0oz Board Size: 81mm*102mm Surface Finish: Immersion Gold 3µ" Min. Trace / Space: 4mil/ 4mil Smallest Hole: 0.2mm Special Specification: BGA: 11.8mil Blind and buried vias L1~L2 Controlled Impedance: Total of 6 Single-ended 50ohm: Differential 90ohm: Differential 100ohm
	Layers: 8L Thickness: 1.2mm        Finished Copper: 1.0oz Board Size: 70mm*90mm Surface Finish: Immersion Gold 3µ" + Gold finger 3u” Min. Trace / Space: 3mil/ 3mil Smallest Hole: 0.2mm Special Specification: Blind and buried vias: L1~L3, L3~L6, L6~L8 Gold Fingers: 45 degree bevelling / Depth 20mil BGA: 14mil / Resin Plugged Controlled Impedance: Total of 20 Single-ended 40ohm: 6.5, 6.8mil Single-ended 45ohm: 5.3, 5.5mil Single-ended 48ohm: 4.8mil Single-ended 50ohm: 4.3, 4.5mil Single-ended 55ohm: 3.5mil Differential 80ohm: 4.5/4.5mil Differential 90ohm: 4.3/5.69mil Differential 100ohm: 5.1/ 6.7mil
	Layers: 8L Thickness: 1.6mm        Finished Copper: 1.0oz Board Size: 145mm*147mm Surface Finish:  Immersion Gold 3µ" Min. Trace / Space: 4mil/ 4mil Smallest hole: 0.2mm Special Specification: Blind and buried vias L8~L7 BGA: 13mil Resin Plugged Controlled Impedance: Total of 6 Single-ended 50ohm: 6mil Differential 90ohm: 6/8mil Differential 100ohm: 7.5/8mil
	Layers: 8L Thickness: 1.0mm        Finished Copper: 1.0oz Board Size: 55mm*142mm Surface Finish: Immersion Gold 3µ" Min. Trace / Space: 4mil/ 4mil Smallest Hole: 0.2mm Special Specification: BGA: 14mil Gold Fingers Blind and buried vias: L1~L3, L1~L5, L6~L7 Controlled Impedance: Total of 1 Differential 100ohm: 4/4mil

*Sources may refer to: TPCA Publication Rigid Circuit Board Materials Introduction.
 
The above are FYI, thank you.