SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 1 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
SEARAYTM* Board To Board System
Connector Routing Guide
* SEARAY is a trademark of Samtec Inc
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 2 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
TABLE OF CONTENTS
I. Overview of the Connector 3
II. Routing Recommendations 4
PCB Pad Layout / Connector foot print 4
Figure 1: Plug Connector Solder Pad Layout 4
Figure 2: Receptacle Connector Solder Pad Layout 4
Routing Pattern: Trace Geometry 5
Figure 3: 5-5-5 Trace Geometry 5
Figure 4: Lateral Escape Routing 6
Figure 5: Longitudinal Esacpe Routing 6
Pair to Pair Spacing When Out of Pin Field 7
Figure 6: Trace Expansion Out of Pin Field 7
Grounding Patterns 7
Figure 7: Grounding Patterns 8
Figure 8: Shielded Grounding Patterns 8
Pad and Anti-Pad Guidelines 9
Figure 9: Trace Routing 9
Via Construction 10
Figure 10: Via Construction Used in SI Analysis 10
Differential Trace to Signal Pad Attachment 10
Figure 11: Flag Escape Detail Longitudinal Escape 10
Intra-pair and Inter-pair skew control 11
Figure 12: Flag Escape Detail 11
Depth of Rows 11
Layer Allocation 12
III. Crosstalk Tx and Rx Arrangement 12
Table A: TX RX grouping separated by low speed (LS) signal columns 12
Table B: TX RX pairs separated by low speed (LS) signal columns 13
Back Drilling 13
Figure 13: Back Drill Specification 13
Keep Out Area 14
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 3 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
I. OVERVIEW OF THE CONNECTOR
The SEARAY connector system provides data rates up to 15 Gbps and superior
signal density up to 67 differential pairs per inch. The SEARAY open pin field provides
designers with flexibility in signal allocation for high-speed differential pairs, low speed
single ended lines and power.
SEARAY’s recessed housing protects terminals from stubbing during mating and
the shrouded housing with guide pins helps align mezzanine cards in blind mating
situations. In processing, SEARAY benefits from Solder ChargeTM SMT Technology with
many advantages over BGA such as increased PCB retention, easier x-ray inspection
and more reliable interfacing to the PCB with a riveted terminal ensuring contact with
the solder pad.
The SEARAY connector system is designed for mezzanine architectures to meet
the growing demands of next-generation telecommunication and data networking
equipment manufacturers. The SEARAY connector system is offered in a large variety
of options with circuit sizes ranging from 40 to 500 circuits and stack heights covering
the gamete of 7 to 15mm.
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 4 of 14
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FILENAME: PS74031C.DOC
II. ROUTING RECOMMENDATIONS
PCB Pad Layout / Connector Footprint
The SEARAY connector system is designed for .025" (0.635mm) diameter solder
pads. A simple .050" x .050" (1.27mm x 1.27mm) solder pad grid is shown in Figure 1.
The solder pad layout is identical between the plug and receptacle with the exception of
the non-plated thru holes (NPTH) for connector alignment pegs relative to row 1 /
position 1.
Figure 1: Plug Connector Solder Pad Layout
Figure 2: Receptacle Connector Solder Pad Layout
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 5 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Routing Pattern: Trace Geometry
For high speed applications it is recommended that the differential signals be
routed through the via pin field as tightly coupled differential pairs in order to minimize
the effects of crosstalk. The differential impedance of the pair should be tuned to be as
close to the nominal system impedance as possible (typically 100 ohms). Other
parameters such as common mode impedance, fabrication consistency, attenuation,
and routing density may also influence the choice of trace dimensions for a particular
application.
For the SEARAY connector the allowable trace geometry is bounded by the
minimum dimensions constant with required impedance and fabrication capabilities and
by the maximum allowable by the SEARAY pin field grid dimensions 050" x .050"
(1.27mm x 1.27mm) of the solder pad grid. A 5-5-5 mil trace geometry is recommended
within the via pin field. Other traces geometries may be used, but is recommended that
the total differential pair width be restricted to 15mils or less. Outside the via pin field the
traces may be expanded as a loosely coupled differential pair (for example 7-14-7) or
uncoupled single ended traces as required by the application. It is recommended that
the pairs be edge coupled and aligned parallel to the long axis of the connector. While
broad side coupling may be used, it is likely to require additional skew compensation.
Figure 3: 5-5-5 Trace Geometry
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 6 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Figure 4: Lateral Escape Routing
Figure 5: Longitudinal Escape Routing
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 7 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Pair To Pair Spacing When Out of Pin Field
Outside of the pin field it is recommended that the pair to pair spacing be as wide
as possible to minimize the pair to pair cross talk. Transitions from the pin field tracing
spacing to the general board trace structure should be performed smoothly and
symmetrically.
Figure 6: Trace Expansion Out of Pin Field
Grounding Patterns
The SEARAY connector being an open pin field connector allows various
arrangements of signal pins and ground pins to be defined. For maximum density a
staggered 2:1 signal / ground arrangement may be used. It should be noted that this
arrangement may lead to higher crosstalk than other arrangements.
A staggered 1:1 signal / ground arrangement may be used to give improved
crosstalk isolation relative to the 2:1 signal / ground arrangement.
For maximum crosstalk isolation a fully shielded ground pattern can be used at
the expense of signal density.
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 8 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
2:1 1:1
Figure 7: Grounding Patterns
2:1 Shielded 1:1 Shielded
Figure 8: Shielded Grounding Patterns
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 9 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Pad and Anti-pad guidelines
For High-speed signaling applications Pad and anti-pad construction are of
critical importance. For correct attachment of the SEARAY connector the top layer SMT
pads are required to be .025" (0.635mm) in diameter. The internal pads should be small
to minimize capacitance. The inner layer pads and annular ring with outer diameter of
18 mils is recommended. The number of pads on inner layers should be the minimal
required to maintain good adhesion of the via to the PCB in order to minimize the
capacitance for the via structure.
Anti-pads are recommended to be 35 mils in radius when used with 15mil (total
width) differential pairs (for example 5-5-5 or 4-6-4 traces). The anti-pad should be large
to allow for minimum deviation of impedance from the nominal value. However, it should
not be so large that that the anti-pad cavity can extend over the trace causing
impedance discontinuities and a reduction in cross talk isolation. Anti-pads may align
with the outer edges of the differential traces, but should not extend over the differential
pairs in order maintain control of crosstalk and impedance. Smaller than recommended
anti-pads may be used but a negative influence on via impedance is expected.
Figure 9: Trace Routing
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 10 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Via construction
For the SEARAY connector via in pad construction is recommended to minimize
any impedance discontinuity at the via / pad transition. Dog bone via structures may be
used but with an expected reduction in electrical performance.
As a surface mounted technology (SMT), the SEARAY connector does not
constrain the choice of via size due to compliant pin or press fit requirements. A 10 mil
(drill) via barrel was used in the SI analysis of the SEARAY via structure and this size or
smaller is recommended depending on the host board thickness and allowable aspect
ratio.
Figure 10: Via Construction Used in SI Analysis
Differential Trace to Signal Pad Attachment
For the SEARAY connector a 45° flag style launch (Figure 4) is preferred for high
speed applications. The 45° flag provides a reduced capacitance and reduced
differential impedance discontinuity.
Figure 11: Standard Escape Detail (Longitudinal)
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 11 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
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FILENAME: PS74031C.DOC
Intra-pair and Inter-pair skew control
Routing orthogonally to the differential pair directly though the pin field in a lateral
escape configuration is recommended to minimize the intra-pair skew. A longitudinal
escape may be used but some form of skew compensation may be required. It is
recommended that the differential pairs be routed through opposite side of the
connector on the top and bottom boards to minimize inter-pair skew. If this is impractical
then skew compensation should be performed outside the pin field to achieve an
acceptable level of inter-pair skew control. If the traces are routed longitudinally intra-
pair skew may be compensated by routing the traces on the top and bottom board in
opposite directions so that the traces are essentially mirror image. It is recommended
that any skew compensation applied to the traces be distributed along the traces
outside of the pin field region rather than performed at a single point along the trace.
Figure 12: Flag Escape Detail
Depth of rows
It is recommended that the differential traces be routed to minimize the depth of
rows through which the signal traces must pass. This means that ideally the signals be
routed with center symmetry along the longitudinal axis of the connector so that cross
talk and impedance variations observed by the signal traces are minimized.
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 12 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Layer allocation
To avoid stub effects it is recommended that high speed differential pairs be
routed on the bottom layers of the PCB board. Use of embedded micro-strip routing on
the top layer and strip-line traces with micro-vias on the upper layers can allow high
speed routing on the upper layers with minimum stub effects. Middle layers should be
used with caution when routing high speed lines. If middle layer must be used then back
drilling is highly recommended to optimize impedance and minimize crosstalk.
III. CROSSTALK TX AND RX ARRANGEMENT
Cross talk is strongly influenced by the rise time of the input signal. High-speed
signals can show significant increase in cross talk relative to lower speed signals in the
same channel. For this reason careful consideration of signal arrangement should be
made. It is recommended that Tx and Rx signals be grouped together in separate
blocks to minimize cross talk. In addition high-speed signals can be separated by power
return and low speed signaling to further increase crosstalk isolation. It is also
recommended that Tx and Rx signals be routed out on different layers to increase cross
talk isolation between traces
Table A: TX RX grouping separated by low speed (LS) signal columns
1 Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx Rx Rx
2 Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx
3 Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx Rx Rx
4 Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx
5 Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx Rx Rx
6 Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx
7 Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx Rx Rx
8 Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx
9 Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx Rx Rx
10 Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P Rx Rx Rx Rx
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
A B C D E F G H J K L M N O P R S T U V W X Y Z AA AB AC AD AE AF
Single 2:1 Diff Pairs 1:1 Diff Pairs Fully Shielded
Ended
Rx
Rx
=
Rx Signal
Tx
Tx
=
Tx Signal
SE/P
SE/P
=
Low speed single ended / Power
=
Ground
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 13 of 14
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FILENAME: PS74031C.DOC
Table B: TX RX pairs separated by low speed (LS) signal columns
Back drilling
For high speed signals, it is highly recommended for any via that extends a
significant number of layers below the active signal layer that the excess via stub below
the active signal layer is removed by back drilling. In simulation back drilling has shown
significant improvement in via impedance and crosstalk. Routing on bottom layer with
minimal stub and routing on top layers with control depth via reduces the need for back
drilling, but for signals routing on middle layers back drilling is strongly recommended.
Since the Searay connector does not require any control of drilling depth to
accommodate a press fit or compliant pin, back drilling depth is determined only by the
depth of the active layer and the accuracy and resolution of the drilling process.
For a 10mils drill size it is recommended that a 12mils ~14mils drill size be used
for back drilling.
Figure 12: Back Drill Specification
1 SE/P SE/P SE/P Tx SE/P Rx Rx Rx Rx Rx Rx Rx Rx Rx Rx
2 Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P
3 SE/P SE/P SE/P Tx SE/P Rx Rx Rx Rx Rx Rx Rx Rx Rx Rx
4 Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P
5 SE/P SE/P SE/P Tx SE/P Rx Rx Rx Rx Rx Rx Rx Rx Rx Rx
6 Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P
7 SE/P SE/P SE/P Tx SE/P Rx Rx Rx Rx Rx Rx Rx Rx Rx Rx
8 Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P
9 SE/P SE/P SE/P Tx SE/P Rx Rx Rx Rx Rx Rx Rx Rx Rx Rx
10 Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx SE/P SE/P SE/P SE/P SE/P
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
A B C D E F G H J K L M N O P R S T U V W X Y Z AA AB AC AD AE AF
Single 2:1 Diff Pairs 1:1 Diff Pairs Fully Shielded
Ended
Rx
Rx
=
Rx Signal
Tx
Tx
=
Tx Signal
SE/P
SE/P
=
Low speed single ended / Power
=
Ground
SEARAY CONNECTOR ROUTING GUIDE
REVISION: ECR/ECN INFORMATION: SHEET No.
EC No:
UCP2010-1365
A DATE:
2009/12/01
TITLE:
SEARAY BOARD TO BOARD SYSTEM
CONNECTOR ROUTING GUIDE 14 of 14
DOCUMENT NUMBER: CREATED / REVISED BY: CHECKED BY: APPROVED BY:
AS-45970-990 GREGORI SQUIRE / STANCZAK COMERCI
FILENAME: PS74031C.DOC
Keep out area
Recommended clearance or keep out area allowed for reworking of this component is
.200” (5.0mm) all the way around the perimeter of the part. Contact Molex if further assistance is
required.
The required distance between the connector and an impedance discontinuity is highly
dependent on the rise time and spectral content of the data transmitted. For a 6.25GHz NRZ
differential signal it is recommended that a keep out distance of greater than 12.5mm be kept
between the connector and any impedance dicontinuity (based on the 1/4 wavelength distance
of the clock frequecy in the PCB dielectric).
