Intel LGA 771 User Manual
LGA771 Socket
Mechanical Design Guide
November, 2006
Reference Number: 313871-002
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Designers must not rely on the absence or characteristics of any features or instructions marked “reserved” or “undefined.” Intel
reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future
changes to them.
The LGA 771 socket may contain design defects or errors known as errata which may cause the product to deviate from published
specifications. Current characterized errata are available on request.
Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order.
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Copyright © 2006, Intel Corporation.
2 LGA 771 Socket Mechanical Design Guide
Contents
1 Introduction.................................................................................................................7
1.1 Document Goals and Scope ..................................................................................7
1.1.1 LGA771 Socket Overview ..........................................................................7
1.1.2 Document Goals.......................................................................................7
1.1.3 Important Remarks ..................................................................................7
1.2 Terminology .......................................................................................................8
1.3 Reference Documents ..........................................................................................8
2 Assembled Component and Package Description...............................................................9
3 Mechanical Requirements ............................................................................................ 11
3.1 Attachment ...................................................................................................... 11
3.2 Socket Components........................................................................................... 11
3.2.1 Socket Body .......................................................................................... 11
3.2.2 Socket Actuation Mechanism.................................................................... 13
3.2.3 Pick and Place Cover............................................................................... 14
3.2.4 Socket Insertion / Actuation Forces........................................................... 14
3.3 Socket Size ...................................................................................................... 14
3.4 Socket Weight .................................................................................................. 14
3.5 Package/Socket Stackup Height .......................................................................... 15
3.6 Socket Loading Specifications ............................................................................. 15
4 Electrical Requirements ............................................................................................... 19
5 Environmental Requirements ....................................................................................... 21
5.1 Solvent Resistance ............................................................................................ 23
5.2 Durability ......................................................................................................... 23
A Mechanical Drawings................................................................................................... 25
LGA 771 Socket Mechanical Design Guide 3
Figures
3-1 Cross-sectional view of Package / Socket stackup height1.......................................15
3-2 Definition of R ...................................................................................................17
5-1 Flow Chart of Knowledge-Based Reliability Evaluation Methodology...........................21
A-1 LGA Socket Assembly Drawing (Sheet 1 of 4) ........................................................26
A-2 LGA Socket Assembly Drawing (Sheet 2 of 4) ........................................................27
A-3 LGA Socket Assembly Drawing (Sheet 3 of 4) ........................................................28
A-4 LGA Socket Assembly Drawing (Sheet 4 of 4) ........................................................29
A-5 LGA771 Socket Motherboard Footprint (Sheet 1 of 7) .............................................30
A-6 LGA771 Socket Motherboard Footprint (Sheet 2 of 7) .............................................31
A-7 LGA771 Socket Motherboard Footprint (Sheet 3 of 7) .............................................32
A-8 LGA771 Socket Motherboard Footprint (Sheet 4 of 7...............................................33
A-9 LGA771 Socket Motherboard Footprint (Sheet 5 of 7) .............................................34
A-10 LGA771 Socket Motherboard Footprint (Sheet 6 of 7) .............................................35
A-11 LGA 771 Socket Motherboard Footprint (Sheet 7 of 7) ............................................36
A-12 LGA 771 Socket Footprint (Sheet 1 of 2) ..............................................................37
A-13 LGA 771 Socket Footprint (Sheet 2 of 2) ..............................................................38
Tables
3-1 Intel® Xeon® 5000 Sequence Package and Socket Stackup Height..........................15
3-2 Socket Loading Specifications..............................................................................16
4-1 LGA771 Socket Electrical Requirements ................................................................19
5-1 Use Conditions Environment................................................................................22
4 LGA 771 Socket Mechanical Design Guide
Revision History
Revision Description Date
001 • Initial release of the document. June 2006
• Updated Dual-Core 5000 & 5100 Series stackup heights
002
• Added Quad-Core 5300 Series stackup height
• Added Figure 3-1
• Removed Appendix B - Vendor Information
§
November 2006
LGA 771 Socket Mechanical Design Guide 5
6 LGA 771 Socket Mechanical Design Guide
Introduction
1 Introduction
1.1 Document Goals and Scope
1.1.1 LGA771 Socket Overview
This document describes a surface mount, LGA (Land Grid Array) socket intended for
the Dual-Core Intel® Xeon® Processor 5000 Sequence Family for Servers and
Workstations. The socket provides I/O, power and ground contacts. The socket
contains 771 contacts arrayed about a cavity in the center of the socket with solder
balls for surface mounting with the motherboard. The LF-LGA771 Socket contains leadfree solder balls while the LGA771 Socket contains eutectic solder balls. This Design
Guide will refer to the socket as LGA771 for simplicity, but its contents are applicable to
both lead-free and eutectic solder materials unless otherwise specified. The socket
contacts have 1.09 mm X 1.17 mm pitch (X by Y) in a 33x30 grid array with 15x14 grid
depopulation in the center of the array and selective depopulation for keying features.
A matching LGA package will be mated with the socket.
For board layout, the land pattern for the LGA771 socket is 43 mils X 46 mils (X by Y),
and the pad size is 18 mils. The component dimensions are defined in metric so there is
a slight round-off error when converting to mils, but it is a negligible amount, relatively
speaking, when compared to the size of the ball and pad. There have been no reported
manufacturing issues.
1.1.2 Document Goals
The goals of this document are:
• To provide LGA771 socket information necessary for motherboard design to ensure
the specified performance of the platform.
• To define the boundary conditions and design constraints within which the socket
design must fit and perform.
1.1.3 Important Remarks
All LGA771 socket characteristics mentioned in this document may change.
LGA771 socket validation reports are available from socket vendors.
LGA 771 Socket Mechanical Design Guide 7
1.2 Terminology
Term Description
LGA771 Socket Processor in the 771-land package mates with the system board through a surface
LGA771-Land
LGA771 Package
IHS (Integrated Heat
Spreader)
Lead-free / Pb-free Lead has not been intentionally added, but lead may still exist as an impurity below
RoHS compliant Lead and other materials banned in RoHS Directive are either (1) below all applicable
mount, 771-pin, LGA (land grid array) socket.
Processors in the 771-Land package are available in a Flip-Chip Land Grid Array
package technology, consisting of a processor core mounted on a substrate with an
integrated heat spreader (IHS). This packaging technology employs a 1.09 mm x
1.17 mm pitch for the substrate lands. Refer to the processor datasheet for
additional information.
A component of the processor package used to enhance the thermal performance of
the package. Component thermal solutions interface with the processor at the IHS
surface.
1000 ppm.
substance thresholds as proposed by the EU or (2) an approved/pending exemption
applies. (Note: RoHS implementing details are not fully defined and may change).
1.3 Reference Documents
Document Intel Order Number
Dual-Core Intel® Xeon® Processor 5000 Series Datasheet 313079
Dual-Core Intel® Xeon® Processor 5100 Series Datasheet 313355
Dual-Core Intel® Xeon® Processor 5000 Series Thermal/Mechanical Design Guide 313062
Dual-Core Intel® Xeon® Processor 5100 Series Thermal/Mechanical Design Guide 313357
Quad-Core Intel® Xeon® Processor 5300 Series Datasheet 315569
Quad-Core Intel® Xeon® Processor 5300 Series Thermal/Mechanical Design Guide 315794
Introduction
Note: Contact your Intel representative for the latest revisions of these documents.
§
8 LGA 771 Socket Mechanical Design Guide
Assembled Component and Package Description
2 Assembled Component and
Package Description
The LGA771 Socket dimensions and characteristics must be compatible with that of the
processor package and related assembly components. Processors using Flip-Chip Land
Grid Array package technology are targeted to be used with the LGA771 socket.
The assembled component may consist of a cooling solution (heatsink, fan, clips, and
retention mechanism), and processor package. The processor Thermal/Mechanical
Design Guidelines (TMDG) provides information for designing components compliant
with the Intel reference design.
Relevant processor 771-Land LGA package and pin-out information is given in the
processor datasheet.
§
LGA 771 Socket Mechanical Design Guide 9
Assembled Component and Package Description
10 LGA 771 Socket Mechanical Design Guide
Mechanical Requirements
3 Mechanical Requirements
3.1 Attachment
The socket will be tested against the mechanical shock and vibration requirements
listed in Section 5 under the expected use conditions with a heatsink and retention
mechanism attached under the loading conditions outlined in Section 3.6, and the
processor datasheet. The socket will only be attached by the 771 contact solder balls to
the motherboard. There are no additional external methods (i.e. screw, extra solder,
adhesive, etc.) to attach the socket.
Note: Heatsink Static Compressive Loading
Heatsink static compressive loading is traditionally used for:
• Mechanical performance in mechanical shock and vibration.
• Thermal interface material (TIM) performance
— Required preload depends on selected TIM
In addition to mechanical performance in shock and vibration and TIM performance,
LGA771 socket requires a minimum heatsink static compressive load to protect against
fatigue failure of socket solder joints.
Solder ball tensile stress is created by inserting a processor into the socket and
actuating the LGA771 socket load plate. In addition, solder joint shear stress is caused
by coefficient of thermal expansion (CTE) mismatch induced shear loading. The solder
joint compressive axial force induced by the heatsink static compressive load helps to
reduce the combined joint tensile and shear stress.
Overall, the heatsink required static compressive load is the minimum static
compressive load needed to meet all of the above requirements: Mechanical shock and
vibration, TIM performance, and LGA771 socket protection against fatigue failure.
Refer to Section 3.6 for detailed information for heatsink static compressive load for
the LGA771 socket to ensure socket solder joint protection against fatigue in
temperature cycling.
3.2 Socket Components
The socket is made of four main components: socket body, load plate, load lever, and
socket body stiffener. Refer to Appendix A for detailed drawings.
The socket will be delivered as a single integral assembly.
3.2.1 Socket Body
3.2.1.1 Housing
The housing material will be a thermoplastic or equivalent, UL 94 V-0 flame rating,
temperature rating and design capable of maintaining structural integrity following a
temperature of 260°C for 40 seconds which is typical of a reflow/rework profile for
solder material used on the socket. The material must have a thermal coefficient of
expansion in the XY plane capable of passing reliability tests rated for an expected high
LGA 771 Socket Mechanical Design Guide 11
operating temperature, while mounted on an FR4-type motherboard material. The
creep properties of the material must be such that the mechanical integrity of the
socket is maintained for the use condition outlined in Section 5.
The color of the socket housing will be dark as compared to the solder balls to provide
the contrast needed for surface-mount (SMT) equipment pick and place vision systems.
Components of the socket may be different colors as long as they meet the above
requirement.
3.2.1.2 Package Installation / Removal Access
Access will be provided to facilitate the manual insertion and removal of the package.
To assist in package alignment and proper orientation during package installation into
the socket:
• The package substrate has keying notches along two opposing edges of the
package and offset from the package centerline (refer to the processor datasheet
for further details).
• The socket utilizes one feature designed to mate with the keying notch along the
inside wall of the package seating cavity (refer to Appendix A).
3.2.1.3 Socket Standoffs
Mechanical Requirements
Standoffs will be provided on the bottom of the socket base in order to ensure the
minimum socket height after solder reflow. The standoff locations and surface area
located as specified in Appendix A. A minimum gap between the solder ball seating
plane and the standoff prior to reflow is required to prevent solder ball to motherboard
land open joints.
3.2.1.4 Markings
All markings withstand a temperature of 260°C for 40 seconds, which is typical of a
reflow/rework profile for solder material used on the socket, as well as any
environmental test procedure outlined in Section 5 without degrading.
3.2.1.4.1 Name
LGA771 (Font type is Helvetica Bold – minimum 6 point (or 2.125 mm)).
This mark shall be stamped or Laser Marked into the sidewall of the stiffener plate on
the actuation lever side when eutectic solder is used.
LF-LGA771 (Font type is Helvetica Bold – minimum 6 point (or 2.125 mm)).
This mark shall be stamped or Laser Marked into the sidewall of the stiffener plate on
the actuation lever side when lead-free solder is used.
Manufacturer’s insignia (Font size is at supplier’s discretion).
This mark will be molded or Laser Marked into the socket housing.
Both socket name and manufacturer’s insignia will be visible when first seated on the
motherboard.
12 LGA 771 Socket Mechanical Design Guide
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