Intel Pentium 4 Processor 478-Pin Socket (mPGA478) Design Guidelines

Intel® Pentium® 4 Processor 478-Pin Socket (mPGA478)
R
13
3.12. Solder Ball/Surface Mount Feature True Position
The solder balls/surface mount features have a 254 mm diametrical true position requirement with respect to
Datum. See Section 8 – Appendix Z.2.
3.13. EMI Tab Socket Requirements
The principal functionality of the EMI Tab is a potential locating feature by which the EMI ground frame
component could be assembled to the socket prior to heat sink installation. The socket EMI Tab shall retain
EMI component through environmental testing.
3.13.1. Tab Size
Material MUST be maintained in the two lower corners of the rectangular cross-section. w = 1.5 mm MIN or,
h = 0.5 mm MIN See Section 8 – Appendix Z.2 – for location on the socket.
EMI TAB Outline
4.87mm
1.1
mm
Option 1
4.87mm
1.1
mm
w
Option 2
4.87mm
h
3.13.2. Tab Shape
The shape of the two lower corners must be square (radius 0.76 max allowed) Vendors may modify the
geometry in one of the following ways (NOT BOTH):
1. Introducing a vertical channel located exactly at the CL of the socket so long as the resulting tabs have
a minimum width of 1.5 mm
2. Shortening the height of the rectangle to a minimum of 0.5 mm (with the caveat that this will affect the
lead-in angle of the tab and may significantly increase the assembly force when installing the EMI
component).