Intel LGA 771 1

LGA 771 Socket Mechanical Design Guide 7

Introduction

1Introduction

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 lead-

free 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.

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.

All LGA771 socket characteristics mentioned in this document may change.

LGA771 socket validation reports are available from socket vendors.