0787150007

SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES TABLE OF CONTENTS 1.0 SCOPE 2.0 PC BOARD REQUIREMENTS 2.1 MATERIAL THICKNESS 2.2 LAYOUT 3.0 HIGH SPEED ROUTING 3.1 TRACE TO PAD ATTACHMENT 3.2 GROUD VIA PLACEMENT 3.3 IMPEDANCE MATCHING AT TRACE AND FOOTPRINT/PAD 3.4 HIGH SPEED REFERENCE PLANE ANTI-PAD 3.5 SKEW COMPENSATION FOR DIFFERENTIAL ROUTING 3.6 TRACE COMPARISON REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 1 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 1.0 SCOPE This board layout and routing guidelines cover the printed circuit board layout that can be used for the evaluation of high-speed signals using microstrip routing for 78715 series connector. Disclaimer: Molex does not guarantee the performance of the final product to the information provided in this document. All information in this report is considered Molex proprietary and confidential. This guide is not intended as a substitute for engineering analysis where optimization for signal integrity (SI) performance can be critical. 2.0 PC BOARD REQUIREMENTS 2.1 MATERIAL THICKNESS The recommended PC board thickness shall be 1.60mm. Suitable PC board material shall be glass epoxy (FR-4). 2.2 LAYOUT The solder pads for the connector assembly must be precisely located to ensure proper placement and optimum performance of the connector assembly. Refer to the applicable Sales Drawing for the recommended solder pad pattern, dimensions and tolerances. REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 2 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 3.0 HIGH SPEED ROUTING 3.1 TRACE TO PAD ATTACHMENT There are several ways to connect the traces to their corresponding signal pads. Two possible methods are illustrated in Figures 1 and 2. Figure 1 Figure 2 As seen in Figure 1, trace routed outwards from pad of connector will result in minimum pad stub while worst case pad stub occurs when trace is routed inwards as shown in Figure 2. REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 3 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 3.2 GROUND VIA PLACEMENT There are several ways to connect ground vias to their corresponding ground pads. Two possible methods are illustrated in Figures 3 and 4. PCB Top View Ground Via Ground Via Figure 3 PCB Top View “Run-away” Ground Via Figure 4 As seen in Figure 3, ground vias can be attached to both ends of ground pad for better signal return path. If this is not possible due to routing constrain, “run-away” ground vias from ground pads should follow the direction where the signal traces were attached to their corresponding signal pads as shown in Figure 4. REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 4 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 3.3 IMPEDANCE MATCHING AT TRACE AND FOOTPRINT/PAD Impedance matching is critical to improve and optimize SI performance. All traces and pad should design to obtain single-end 50Ω or differential 100Ω at application. This could be done by controlling distance between trace (Htrace) and pad (Hpad) with reference to their ground return. This is illustrated in Figure 5. When the trace width of pad equals to trace, Htrace equals Hpad. If pad width is wider than trace, Hpad > Htrace. This is to eliminate excessive capacitive coupling at pad region. Connector housing trace pad Hpad Htrace PCB Figure 5 REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 5 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 3.4 HIGH SPEED REFERENCE PLANE ANTI-PAD An antipad or copper cutout region, shown in Figure 6, is needed to obtain desirable Hpad for impedance optimization. A table containing suggested values are shown in Table 1. Connector housing trace pad Hpad Htrac PCB antipad Antipad = X by Y a Y c b X Figure 6 – Port Footprint Antipad Dimension Primary/Secondary Port X Y 7c + 6b a+b Table 1 Note: Anti-pad was implemented for impedance matching. Dimensions can vary from recommendation to meet electrical requirements. For example, the anti-pad can be made larger with a broader keep-out region on non-signal ground planes to minimize parasitic capacitance. REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 6 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC SAS-3 VERTICAL SMT RECEPTACLE BOARD LAYOUT AND ROUTING GUIDELINES 3.5 SKEW COMPENSATION FOR DIFFERENTIAL ROUTING It is recommended that skew compensation be distributed verses grouped in one or more locations. 3.6 TRACE COMPARISON TRANSITION SHOULD BE SYMMETRIC REVISION: D ECR/ECN INFORMATION: TITLE: EC No: S2014-1265 DATE: 2014/06/23 DOCUMENT NUMBER: AS-78715-001 SI BOARD LAYOUT AND ROUTING GUIDELINE FOR SAS-3 VERTICAL SURACE MOUNT RECEPTACLE SHEET No. 7 of 7 CREATED / REVISED BY: CHECKED BY: APPROVED BY: CMWONG 2014/06/23 HELVY 2014/06/23 WTCHUA 2014/06/23 TEMPLATE FILENAME: AS1704602.DOC