Ball Grid Array or BGA packages are a type of surface mount technology. Surface mount technologies are widely used in integrated circuits. BGA is the name given to the structure in which the chips are soldered directly to the PCB without using any sockets, which has become an indispensable part of electronic circuit production with the many advantages it offers.
BGA packages were developed because a more efficient and logical package system was needed for integrated circuits with many pins. With the increasing need for integrated circuits, some circuits had more than 100 pins.
Packages with conventional design have very thin and tightly spaced pins. This causes very easy damage even in controlled environments. The soldering process of these packages also needs to be done very carefully. Otherwise, excess solder causes poor placement.
From a design point of view, because the pin density is so high, congestion occurs in the circuits on the way out. BGA packages have been developed to overcome these problems and also increase the reliability of soldered parts.
Purposes of BGA
BGA was developed to provide many advantages to manufacturers of integrated circuits and electronic components, and therefore to those who use these equipment. We can summarize the advantages of this technology as follows:
- Effective use of the circuit space on the cards, allowing the connection to the packets not only from the outside, but also from the bottom.
- It includes improvements in terms of thermal and electrical performance (BGA packages provide sufficient power for low conductivity or controlled impedance paths and channel excess heat to the outside).
- It positively affects the production process as it makes the soldering process more effective, allowing wider spacing between the connections and facilitating the soldering process.
- It provides the advantage of use in devices that need to be produced thinner, such as mobile phones, due to reducing the package thickness.
- Improved compatibility for reworking circuits.
What is BGA Package?
BGA takes a different approach than conventional surface mount connections. Other packages, for example Quad Flat Pack (QFP) use the environment for connections. Since the pins were placed very close, there was very little space to connect. BGA, on the other hand, also uses the bottom of the package and provides sufficient space for connections.
The pins are placed on the underside of the chip carrier in a grid texture. In addition, instead of pins that will provide connection, pads covered with solder balls are used. With the matching copper pads, the necessary connection is provided on the circuit board.
Besides the improvements in connectivity, BGA has other advantages as well. Compared to QFP, it offers lower thermal resistance in the silicon chip itself. Thus, the heat generated in the integrated circuit is transferred to the card more quickly and effectively. This allows BGA devices to generate more heat without the need for special cooling measures.
With the conductors on the bottom surface of the chip carrier, the paths on the chip become shorter. Thus, the unwanted conductivity level of the solder is reduced and higher performance is offered compared to the QFP.
What are BGA Package Types?
Many different types of BGA have been developed for different types of equipment and production options.
- MAPBGA – Molded Array Process Ball Grid Array: This BGA package was developed for low and medium performance class devices. It was created especially for jobs requiring easy surface mounting and low inductance. Still with high stability, this type of BGA offers a low-cost choice.
- PBGA – Plastic Ball Grid Array: This BGA package was developed for medium and high performance class devices. It is designed to handle higher power thanks to the additional copper layers it contains.
- TEPBGA – Thermally Enhanced Plastic Ball Grid Array: This package has higher heat dissipation level. Thanks to the thick copper layers, the heat is withdrawn from the circuit and transferred to the card.
- TBGA – Tape Ball Grid Array: This BGA package has been developed for mid to high class devices that do not have an external source of heat absorbing but require high thermal performance.
- PoP – Package on Package: This BGA package stands out in applications where space is critical. It allows a memory pack to be placed on the main device.
- MicroBGA: As the name suggests, this BGA package is smaller. These BGA packages with dimensions such as 0.65, 0.75 and 0.8 mm are used in industry.
Testing BGA Devices
One of the problems of BGA devices is that it is not possible to show soldered connections with optical methods. When this technology was introduced, manufacturers were therefore skeptical and tested whether the soldering process was effective. The main problem with BGA devices was the need to ensure that enough heat was applied to effectively melt the solder balls on the grid.
It is also not possible to perform a full test of assembly joints by testing electrical performance. It is possible that the joints are not made properly and cannot function over time. X-ray is currently the only satisfactory examination method. When making sure the heat profile of the soldering machine is set properly, BGA devices solder very well and have very few problems. BGA mounting is also possible for most applications.
BGA Repair/Reballing
BGA package can be removed and replaced with a new one. Generally, it is possible to repair or renew BGA packages when they are dismantled. BGA repair can make sense if the chip is expensive.
During the repair process, a process called reballing, in which the solder ball is replaced, needs to be applied. It is possible to use small ready solder balls produced and sold for this purpose. Manufacturers also have specialized equipment for this process.
