Land grid array
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The land grid array (LGA) is a type of surface-mount packaging for integrated circuits (ICs) that is notable for having the pins on the socket rather than the integrated circuit. An LGA can be electrically connected to a printed circuit board (PCB) either by the use of a socket or by soldering directly to the board.
The land grid array is a packaging technology with a square grid of contacts on the underside of a package. The contacts are to be connected to a grid of contacts on the PCB. Not all rows and columns of the grid need to be used. The contacts can either be made by using an LGA socket, or by using solder paste.
LGA packaging is related to ball grid array (BGA) and pin grid array (PGA) packaging. Unlike pin grid arrays, land grid array packages are designed to fit both in a socket or be soldered down using surface mount technology. PGA packages cannot be soldered down using surface mount technology. In contrast with a BGA, land grid array packages in non socketed configurations have no balls and use a flat contact which is soldered directly to the PCB and BGA packages have balls as their contacts in between the IC and the PCBs.
Use in microprocessors 
LGA is used as a physical interface for microprocessors of the Intel Pentium 4 (Prescott), Intel Xeon, Intel Core 2, Intel Core (Bloomfield and Lynnfield) and AMD Opteron families. Unlike the pin grid array (PGA) interface found on most AMD and older Intel processors, there are no pins on the chip; in place of the pins are pads of bare gold-plated copper that touch protruding pins on the microprocessor's placeholder on the motherboard.
While LGA sockets have been in use as early as 1996 by the MIPS R10000 and HP PA-8000 processors, the interface did not gain widespread use until Intel introduced their LGA platform, starting with the 5x0 and 6x0 sequence Pentium 4 (Prescott) in 2004. All Pentium D and Core 2 desktop processors currently use an LGA socket. As of Q1 2006, Intel switched the Xeon server platform to LGA, starting with the 5000-series models. AMD introduced their server LGA platform starting with the 2000-series Opteron in Q2 2006. AMD offered the Athlon 64 FX series on socket 1207FX through ASUS's L1N64-SLI WS motherboards. It was the only desktop LGA solution offered by AMD.
The most common Intel desktop LGA socket is dubbed LGA 1155 (Socket H2), which is used with Intel's Sandy Bridge and Ivy Bridge series Core i3, i5, and i7 families. However, the Sandy Bridge-E Core i7 family uses the LGA 2011 (Socket R) socket. The LGA setup provides higher pin densities, allowing more power contacts and thus a more stable power supply to the chip. LGA packaging also has a tertiary benefit of placing pins onto the motherboard; if a pin breaks, the motherboard is often cheaper to replace than the CPU chip (as compared to a PGA chip/socket setup).
The AMD server LGA socket is designated Socket G34 (LGA 1944). Like Intel, AMD decided to use LGA sockets for their higher pin densities, as a 1944-pin PGA would simply be too large for most motherboards.
- LGA 775 (Socket T)
- LGA 771 (Socket J)
- LGA 1366 (Socket B)
- LGA 1356 (Socket B2)
- LGA 1156 (Socket H)
- LGA 1155 (Socket H2)
- LGA 1150 (Socket H3)
- LGA 2011 (Socket R)