BGA, PGA and LGA – What is behind the different grid arrays?

If you take a closer look at different CPU types, you will inevitably come across terms such as BGA, PGA and LGA. We will explain to you what these abbreviations actually mean.

The terms BGA, PGA, LGA and CCGA are name types of integrated circuit packaging. However, they differ in the type of connections.

##What is integrated circuit

Ball Grid Array (BGA)

The abbreviation BGA stands for "Ball Grid Array". In this package, small solder balls form the connections, which are arranged in a square grid made up of columns and rows on the bottom surface of the chip. This design enables considerably more connections to be accommodated, roughly twice as many as with PGA. The solder balls provide short connections and therefore an enormous performance.

The advantages of BGA lie in the small space requirement, the good heat dissipation and the low impedance due to short connection paths to the circuit board. In addition, the chips can be unsoldered from the circuit board without damaging them. This enables the removal of old solder balls (deballing) and populating with new balls (reballing). The chip can then be soldered to a new circuit board. Since soldered processors are mechanically and thermally extremely robust, BGA is mainly used for embedded CPUs.

A major disadvantage is that the solder joints can only be checked by X-ray, as the connections are covered and difficult to access. This also severely limits repair options. Special equipment, a so-called reflow oven, is required for safe soldering. In addition, BGA chips can only be used effectively on multilayer boards, which limits their application possibilities.

Pin Grid Array (PGA)

The so-called "Pin Grid Array" (PGA) is mainly used for processors. While soldering balls are used with BGA, the pin grid array - as the name suggests - uses small pins as connections. These are also arranged in a square grid, but the number of connections and arrangement of the arrays varies, so that there is a large number of variants and thus different CPU sockets. The rows of pens can be arranged in parallel or offset, they are identified with numbers and letters.

There are different types of PGA:

  • With the Ceramic Pin Grid Array (CPGA), the semiconductor chip is fixed on a heat-conducting ceramic carrier. It is used in the first generation Intel Pentium, socket A variants of the AMD Athlon and the Duron family.
  • With the Plastic Pin Grid Array (PPGA), the carrier for the semiconductor chip is made of plastic. This variant is a little cheaper, has better thermal properties and also an improved electrical performance than ceramics. PPGA is mainly used for the Pentium MMX processors and Celeron.
  • The Staggered Pin Grid Array (SPGA) is characterized by staggered connection rows. This variant is required for CPUs that have more than 200 connections, because the offset layout offers more space. It is used on the Pentium and later central processing units.
  • With the Flip-Chip Pin Grid Array (FCPGA), the integrated circuit is attached to the top of the carrier ("flip-chip" means "inverted, turned chip"). This design is used for example in Pentium III and some Celeron processors.

Since the pins for PGA are on the CPU, the corresponding holes are on the mainboard so that the CPU can be installed without much pressure.

Land Grid Array (LGA)

The Land Grid Array (LGA) is the exact opposite of PGA. The contact pins are on the base of the mainboard. The CPU has the same number of contact points with which a connection is established. Intel has been using LGA for the majority of its Celeron, Pentium, Core and Xeon CPUs for many years.

The advantages of LGA are, on the one hand, the smaller size of the pins, which enables a larger number of pins in the same area. Secondly, they are not easily damaged because the socket has no pins that can be crushed. Compared to LGA, PGA sockets have the advantage that the mainboard cannot actually be damaged. In addition, pins are easier to repair on a PGA processor than on a LGA mainboard.

Ceramic Column Grid Array (CCGA)

Even if it has nothing to do with Mini-PCs, we want to mention the Ceramic Column Grid Array (CCGA) here for the sake of completeness. CCGA housings are extremely reliable and are used in space and military technology. The solder connections on the underside of the housing are columnar (hence the name “column”) and consist of heavily leaded solder. Similar to BGA, the columns are arranged in a grid. They cannot be used in the civilian market because they are not permitted under the RoHS guidelines due to the high lead content due to EU trade bans.

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