Guide

Thermal and Mechanical Design
56 Intel® Xeon® Processor E7 2800/4800/8800 v2 Product Family
Thermal/ Mechanical Specifications and Design Guide
2.4.5.4.1 Socket-Socket Pitch
2.4.5.5 LGA2011-1 Socket Land Pattern Guidance
The land pattern guidance provided in this section applies to printed circuit board
design. Recommendation for Printed Circuit Board (PCB) Land Patterns is to ensure
solder joint reliability during dynamic stresses, often encountered during shipping and
handling and hence to increase socket reliability.
2.4.5.6 Pad Type Recommendations
Intel defines two types of pad types based on how they are constructed. A metal
defined (MD) pad is one where a pad is individually etched into the PCB with a
minimum width trace exiting it. The solder mask defined (SMD) pad is typically a pad in
a flood plane where the solder mask opening defines the pad size for soldering to the
component.
In thermal cycling a MD pad has shown to be more robust than a SMD pad type. The
solder mask that defines the SMD pad can create a sharp edge on the solder joint as
the solder ball / paste conforms to the window created by the solder mask.
For certain failure modes the MD pad may not be as robust in shock and vibration
(S&V). During S&V, the predominant failure mode for a MD pad in the corner of the
BGA layout is pad craters and solder joint cracks. A corner MD pad can be made more
robust and behave like a SMD pad by having a wide trace enter the pad. This trace
should be 10 mil minimum but not to exceed the pad diameter and exit the pad at a
45 degree angle (parallel to the diagonal of the socket). During board flexure that
results from shock & vibration a SMD pad is less susceptible to a crack initiating due to
the larger surface area.
Figure 2-28. Suggested Board Marking
LGA2011-1