How do BGA, PGA, and LGA differ from each other?
Article By : Ken G
While each of these IC packages comes with its own set of advantages and disadvantages, overall, it is their use that has facilitated a tech revolution.
When it comes to integrated circuit (IC) packaging, you are likely to come across many acronyms such as BGA, PGA, and LGA.
The difference between them lies in terms of the type of connections. It will be worthwhile to look at each of them and the differences between them in some detail.
Ball Grid Array (BGA)
As its name suggests, this array comprises small solder balls that are arranged in a square grid, which is made up of rows & columns. The big advantage of this grid is that it accommodates a large number of connections. Ball Grid Array assembly aka BGA Assembly enables roughly double the number of connections as opposed to Pin Grid Array. The solder balls offer short connections & are high on performance.
BGAs are of several types, namely:
PBGA (Plastic Ball Grid Array)
This is extremely popular when it comes to double-sided PCBs. The core is made up of Bismaleimide Triazine (BT) resin that is used as the substrate material. The big advantage of these arrays is the fact, that they have between 200 to 500 ball arrays and it, therefore, works well for a good number of applications.
CBGA (Ceramic Ball Grid Array)
This package type has ceramic as its substrate. In this BGA, the ratio of tin and lead is 10:90. It, therefore, has a high melting point and is known for its reliability and thermal conductivity. Devices that require a high pin count on flip-chip designs particularly necessitate the use of CBGA.
A variant of this package type, the CCGA, or the Ceramic Column Grid Array uses columns of solder joints. Here the number of contact points compared to basic ball grid arrays is nearly double.
TBGA (Tape Ball Grid Array)
TBGA uses flexible interconnect when it comes to creating fine lines on the solder balls. This kind of package offers superior electric connectivity as well as heat dissipation. The only disadvantage of this kind of BGA is its higher cost.
EBGA (Enhanced Ball Grid Array)
Simply put, this variety is a summation of PBGA along with additional heat sinks. In such arrays, the chips face down & a wire bond is used for conduction between the chips & the PCB.
FC-BGA (Flip Chip Ball Grid Array)
This is similar to CBGA except that the resin used in this case is BT resin. By doing this, the additional cost is saved. The value of this array lies in the fact that there are shorter electrical pathways & hence improved conductivity & performance are a given. Also, the tin & lead ratio in this type is 63:37. Another advantage of this BGA type is that without making use of the flip-chip alignment machine approach, the chips can be realigned.
MBGA (Metal Ball Grid Array)
This type makes use of metal-ceramic as its substrate. Also, it makes use of wire bonding to make connections. It is known for its electrical performance as well as heat dissipation properties.
Micro BGA
In such BGAs, the substrates are made of packing tape and the chips are faced down. As their name suggests, they lend themselves to miniaturization. The big advantage with these BGAs also is that the use of elastomer between the tape & the chip comes in handy when it comes to thermal expansion stress. With a low number of pins, it also comes in handy in high-storage products.
Advantages of BGA
There are several advantages of the BGA. These include:
- It lends itself to optimal space utilization as the packages are small. This does not in any way, however, impact performance
- They ensure optimal heat dissipation
- With short connection paths, they have low impedance
- They are easy to unsolder & do not cause any damage
- Lends itself to Deballing & Reballing. Essentially it means that it is easy to remove old, worn-out solder balls & replace them with new ones
- They are extremely portable.
- They are high in mechanical as well as thermal properties.
Disadvantages of BGA, however, include:
- It necessitates the use of X-rays to inspect the solder joints
- The lack of accessibility limits repairs
- Soldering needs special equipment
- BGAs work well only for multi-layer PCBs.
Pin Grid Array (PGA)
Once again, as their name suggests, these make use of small pins as connections. The pins can be arranged parallel or can be offset. Primarily Pin Grid Arrays are of the following types:
- Ceramic Pin Grid Array (CPGA)-Here the semiconductor chip is fixed on the ceramic carrier. It finds application, among others, in the first-generation Intel Pentium.
- Plastic Pin Grid Array (PPGA)- Here the carrier for the semiconductor chip is made of plastic. This is known for its cost-effectiveness, and thermal as well as electrical properties. It finds application in the Pentium MMX processors.
- Staggered Pin Grid Array (SPGA)-It has staggered connection rows. It finds application in CPUs with more than 200 connections & is known for use in the Pentium
- Flip-Chip Pin Grid Array (FCPGA)- Here the integrated circuit is attached to the top of the carrier. It finds use in Pentium III.
Land Grid Array (LGA)
As opposed to the Pin Grid Array, in the Land Grid Array, the contact pins are placed on the base of the mainboard. It is known for use in the Celeron, Pentium, Core & Xeon CPUs. The advantages it offers include:
- The small size of pins & hence less space requirement
- They aren’t prone to damage
- They are easier to repair.
To Sum up
While each of these IC packages comes with its own set of advantages and disadvantages, overall, it is their use that has facilitated a tech revolution. It is because of their use that miniature devices come with complex computation capabilities.
About the Author
Ken G is a production manager at Technotronix Inc.