Intel 31244 PCI-X Motherboard Stackup for Backplane Designs, Motherboard Stackup, Microstrip

Intel® 31244 PCI-X to Serial ATA Controller

Printed Circuit Board (PCB) Methodology

6.2.2Motherboard Stackup for Backplane Designs

The motherboard is supporting components in addition to GD31244, so an assumption is, desktop PC requirements are dominate to assure the processor and memory subsystem may be implemented with normal 60 ohm guidelines.

Table 12.	Motherboard Stackup, Microstrip
	Variable	Nominal (mil)	Tolerance	Min (mil)	Max (mil)
	Mask Thickness	0.8	+/- 0.2	0.6	1.0
	Mask Er	3.6		3.6	3.6
	Trace Height	4.0	+/- 0.3	3.7	4.3
	Preg Er	4.15	+/- 0.55	3.6	4.7
	Plane Thickness	1.4	+/- 0.2	1.2	1.6
	Trace Thickness	1.4	+/- 0.4	1.0	1.8
	Trace Width	5 mil	+/- 1.5	3.5	6.5
	Total Thickness	62.0	+/- 6.0	56.0	68.0

Table 13.	Motherboard Microstrip Parameters
	Parameter	Routing Guideline	Notes
	Motherboard Layout	Microstrip
	Single Ended Trace Impedance	55 +/- 12%
	Differential Trace Impedance	100 ohms +/- 15%
	Reference Plane	ground
	Trace Thickness	1.4 mil
	Trace Width	5 mil
	Intra Pair Trace Spacing	15 mil	intra-pair to pair center-to-center
	Pair-to-Pair Trace Spacing	55 mil	pair to pair center-to-center
	Trace Length	2” to 6”
	Trace Length Matching	10 mil	Intra-pair matching
	Vias	0	Minimize number of vias (none preferred). Each
			channel in the pair has an equal number of vias.
	When possible, it is recommended that the designer use stripline for the following reasons:

•Reduced skin effect relative to microstrip

•Reduced forward cross talk

•Reduced jitter through differential stackup and isolated power delivery

42 Design Guide