Intel LGA 771 manual Contacts, Lot Traceability

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Mechanical Requirements

3.2.1.4.2Lot Traceability

Each socket will be marked with a lot identification code to allow traceability of all components, date of manufacture (year and week), and assembly location. The mark must be placed on a surface that is visible when mounted on the motherboard.

3.2.1.5Contacts

The socket has a total of 771 contacts, with 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 alignment features. For board layout, a 43 mils x 46 mils pitch

(X by Y) can be utilized.

Base material for the contacts is high strength copper alloy.

For the area on socket contacts where processor lands will mate, there is a 0.381 µm [15 µinches] minimum gold plating over 1.27 µm [50 µinches] minimum nickel underplate.

No contamination by solder in the contact area is allowed during solder reflow.

3.2.1.6Solder Balls

A total of 771 solder balls corresponding to the contacts are on the bottom of the socket for surface mounting with the motherboard.

Two versions of the socket, leaded and lead-free, will be available with the following materials for the solder balls:

•Eutectic Solder

—Sn63 Pb37 (± 0.5% Sn).

—Socket marking will be LGA771 for sockets comprised of eutectic solder.

•Lead-free Solder

—Composition must be lead free and have a melting point temperature in the range of 217-220°C (for example: Sn Ag 3.0 Cu 0.5).

—Socket marking will be LF-LGA771 for sockets comprised of lead-free solder.

The co-planarity (profile) requirement for all solder balls on the underside of the socket is defined in Appendix A.

The solder ball pattern has a true position requirement with respect to applicable datum’s in order to mate with the motherboard land pattern. See Appendix A.

3.2.2Socket Actuation Mechanism

The socket actuation mechanism is made of the load plate and the load lever. These components are made of stainless steel SUS 301. Both components need to be fully actuated to ensure electrical contact. When correctly actuated, the top surface of the processor IHS is above the load plate allowing proper installation of a heatsink. The post-actuated seating plane of the package is flush with the seating plane of the socket. Movement will be along the Z direction, perpendicular to the motherboard.

When combined with the socket body and load lever, the load plate distributes the force necessary to achieve the required socket contact resistance values. The load from the load plate is distributed across two sides of the package onto a step on each side of the IHS. It is then distributed by the package across all of the contacts.

LGA 771 Socket Mechanical Design Guide

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Contents Mechanical Design Guide LGA771 SocketLGA 771 Socket Mechanical Design Guide Contents Tables FiguresRevision Description Date Revision HistoryLGA 771 Socket Mechanical Design Guide Document Goals and Scope IntroductionReference Documents TerminologyTerm Description Document Intel Order NumberAssembled Component and Package Description Assembled Component and Package Description Attachment Mechanical RequirementsSocket Components Name Package Installation / Removal AccessLot Traceability ContactsSocket Size Socket WeightPackage/Socket Stackup Height Socket Loading SpecificationsIntel Xeon 5000 Sequence Package and Socket Stackup Height Parameter Board Socket Loading SpecificationsMin Max Unit Thickness Definition of R Mechanical Requirements LGA771 Socket Electrical Requirements Electrical RequirementsCriteria Size Electrical Requirements Detailed description of this methodology can be found at Environmental RequirementsShipping and Handling Use Conditions EnvironmentDurability Solvent ResistanceEnvironmental Requirements Drawing Description Number Mechanical DrawingsFigure A-1. LGA Socket Assembly Drawing Sheet 1 Figure A-2. LGA Socket Assembly Drawing Sheet 2 Figure A-3. LGA Socket Assembly Drawing Sheet 3 Figure A-4. LGA Socket Assembly Drawing Sheet 4 Figure A-5. LGA771 Socket Motherboard Footprint Sheet 1 Figure A-6. LGA771 Socket Motherboard Footprint Sheet 2 Figure A-7. LGA771 Socket Motherboard Footprint Sheet 3 Figure A-8. LGA771 Socket Motherboard Footprint Sheet 4 Figure A-9. LGA771 Socket Motherboard Footprint Sheet 5 Figure A-10. LGA771 Socket Motherboard Footprint Sheet 6 Figure A-11. LGA 771 Socket Motherboard Footprint Sheet 7 Figure A-12. LGA 771 Socket Footprint Sheet 1 Figure A-13. LGA 771 Socket Footprint Sheet 2
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