BGA (Ball Grid Array) is a technology for surface mounting ICs using small balls on the underside of the chip package instead of pins. BGA is sometimes referred to as CSP (Chip Size Package). The term BGA is most commonly used when talking about packages that are 4, 6, or 8 balls in diameter.
The distinguishing features of a BGA are:
Very small package size (about 1/20th the area of a comparable pin-based package).
All contacts are on the bottom surface of the chip.
Each contact is made with a solder ball, not a wire.
Solder balls usually have to be reflowed in order to make reliable connections to the substrate. The solder balls are melted with a hot gas at temperatures over 400° C (750° F). BGA packages typically use larger balls than CSP packages. The larger balls allow for better distribution of the gas at the bottom of the package.
The balls do not have to be round as in CSP packages; they can be made out of any shape and are frequently rectangular or triangular for more reliable mounting to a PCB.
BGA packages are mechanically very robust. The balls are usually attached to the chip with a small amount of adhesive, and not with solder. This allows for some misalignment between the balls and contact pads on the chip without causing mechanical damage. If there is excessive misalignment, it will result in poor electrical contact and possibly solder fatigue.
BGA packages are generally not as reliable as CSP packages (more time consuming and costly to repair). They often have larger pads to accommodate the increased thermal expansion. The small size of the package makes it hard to maintain a good temperature distribution during soldering and to perform reliable visual inspection after assembly.
BGA is not a technology, but rather a device classification. There are many variations of BGAs, such as multi-chip BGAs and flip-chip BGAs.
Understanding the importance of BGA Sockets for BGA chips
BGA sockets are used for surface-mounting BGAs onto PCBs. BGA sockets help to mount the BGA chips onto PCBs without much hassle. The main problem of mounting an IC onto a PCB is that it can be very difficult to locate the pins of the IC on a PCB and solder them individually. Also, the mounting process can be very time consuming and frustrating if not done correctly. By using BGA sockets, these problems are solved. A BGA socket is made of plastic in the shape of a rectangle and has spaces on its underside to accommodate each solder ball of the BGA chip.
BGA sockets come in two types: active and passive. An active BGA socket has electrical contacts on its underside to which the solder balls of the BGA chip are connected. A passive BGA socket does not have any contact pads on its underside. Instead, it is connected to a PCB using through-holes or surface mount technology (SMT) components. In this article, we will only be looking at active BGA sockets.
BGA sockets are available in a variety of sizes depending on the size of the BGA chip that they are designed to accommodate. Some BGA sockets are designed to accommodate only one BGA chip, while others accommodate two or even four chips. The size of a BGA socket is usually specified in terms of the number of rows and columns on its underside. For example, if a BGA socket is designed to accommodate a 4×4-ball BGA chip, then it would have 16 contact pads arranged in 4 rows and 4 columns.
BGA chips are available in a variety of sizes. The number of balls on the underside of a BGA chip is usually specified as x4, x6 or x8. A x4-ball BGA chip has 4 balls on its underside. A x6-ball BGA chip has 6 balls, and so on.
BGA chips are available in several different ball sizes. The size of the balls is usually specified as x1, x2, x3, etc. A ball size x1 is the smallest ball size and it has a diameter of 0.4 mm. A ball size x4 is the largest ball size and its balls have a diameter of 1.0 mm. The larger the ball size, the larger the footprint of the BGA chip on the PCB.