Fetures of Ball Grid Array

Introduction to Ball Grid Array ( BGA )

In the current information age, with the rapid development of the electronics industry, products such as computers and mobile phones have become increasingly popular. People have more and more functional requirements and stronger performance requirements for electronic products, but the volume requirements are getting smaller and the weight requirements are getting lighter and lighter. This promotes the development of electronic products in the direction of multi-function, high performance, miniaturization and light weight. In order to achieve this goal, the feature size of IC chips will become smaller and smaller, and the complexity will continue to increase. As a result, the number of I/Os in the circuit will increase, and the I/O density of the package will continue to increase. In order to meet the requirements of this development, some advanced high-density packaging technologies have emerged, and BGA packaging technology is one of them.

BGA packaging appeared in the early 1990s and has now developed into a mature high-density packaging technology. Among all packaging types of semiconductor ICs, BGA packaging has the fastest growth rate during the five-year period from 1996 to 2001. In 1999, the output of BGA was about 1 billion. However, so far, this technology is limited to the packaging of high-density, high-performance devices, and the technology is still developing in the direction of fine pitch and high I/O terminal count. BGA packaging technology is mainly suitable for the packaging of PC chipsets, microprocessors/controllers, ASICs, gate arrays, memories, DSPs, PDAs, PLDs and other devices.

Structural features of Ball Grid Array

According to the different packaging materials, BGA components mainly have the following types:
PBGA (plastic BGA, BGA in the plastic package); CBGA (ceramic BGA, BGA in the ceramic package); CCBGA (ceramic column BGA, BGA in the ceramic column package); TBGA (tape BGA, BGA in the carrier tape package); CSP( chip scale package or μBGA)

PBGA (Plastic Ball Array) Package

PBGA (Plastic Ball Grid Array), which uses BT resin/glass laminate as the substrate, and plastic (epoxy molding compound) as the sealing material. The solder balls can be divided into lead solder (63Sn37Pb, 62Sn36Pb2Ag) and lead-free solder ( Sn96.5Ag3Cu0.5), the connection between the solder ball and the package body does not require additional solder.
Some PBGA packages have a cavity structure, which is divided into two types: cavity up and cavity down. This kind of PBGA with a cavity is to enhance its heat dissipation performance, it is called thermally enhanced BGA, EBGA for short, and some are also called CPBGA (cavity plastic solder ball array).

Advantages of PBGA package

• 1. Good thermal matching with PCB board. The coefficient of thermal expansion (CTE) of the BT resin/glass laminate in the PBGA structure is about 14ppm/℃, and that of the PCB board is about 17ppm/cC. The CTE of the two materials is relatively close, so the thermal matching is good;
• 2. The self-alignment effect of the solder ball can be used during the reflow soldering process, that is, the surface tension of the molten solder ball to achieve the alignment requirements of the solder ball and the pad;
• 3. Low cost;
• 4. Good electrical performance.

Disadvantages of PBGA package

Sensitive to moisture, it is not suitable for the packaging of devices that require airtightness and high reliability.

CBGA package (ceramic solder ball array)

CBGA (Ceramic Ball Grid Array) has the longest history in the BGA package series. Its substrate is multi-layer ceramic, and the metal cover is welded on the substrate with sealing solder to protect the chip, leads and pads. The solder ball material is high temperature eutectic solder 10Sn90Pb, and the connection between the solder ball and the package body needs to use low temperature eutectic solder 63Sn37Pb.

advantages of the CBGA package

The advantages of the CBGA package are as follows:

• 1. Good air tightness and high moisture resistance, so the long-term reliability of the packaged components is high;
• 2. Compared with PBGA devices, the electrical insulation characteristics are better;
• 3. Compared with PBGA devices, the packaging density is higher;
• 4. The heat dissipation performance is better than PBGA structure.

disadvantages of the CBGA package

The disadvantages of the CBGA package are as follows:

• 1. Since the coefficient of thermal expansion (CTE) of the ceramic substrate and the PCB board are quite different, the thermal matching is poor, and solder joint fatigue is the main failure mode;
• 2. Compared with PBGA devices, the packaging cost is high;
• 3. The difficulty of aligning the solder balls on the edge of the package body increases.

TBGA package (Tape carrier type solder ball array)

TBGA (Tape Ball Grid Array) is a cavity structure. There are two ways to interconnect the chip and substrate of the TBGA package: flip-chip bonding and wire bonding. The chip is flip-chip bonded on the flexible carrier tape for multi-layer wiring; the peripheral array of solder balls used as the circuit I/O end is installed under the flexible carrier tape; its thick sealing cover is also a heat sink (heat sink), and at the same time In order to strengthen the package body, the solder balls under the flexible substrate have better coplanarity. The chip is bonded to the copper heat sink in the core cavity; the chip pad and the multilayer wiring flexible tape carrier substrate pad are interconnected with bonding wires; the circuit chip, the lead, and the flexible tape carrier pad are encapsulated with a sealant (Potting or coating) up.

advantages of TBGA

The advantages of TBGA are as follows:

• 1. The thermal matching performance of the flexible carrier tape of the package and the PCB board is better;
• 2. In the reflow soldering process, the self-alignment effect of the solder ball and the surface tension of the printed solder ball can be used to achieve the alignment requirements of the solder ball and the pad;
• 3. It is the most economical BGA package;
• 4. The heat dissipation performance is better than PBGA structure.

disadvantages of TBGA

The disadvantages of TBGA are as follows:

• 1. Sensitive to moisture;
• 2. The multi-level combination of different materials has an adverse effect on reliability.

Other BGA package types

• MCM-PBGA (Multiple chip module-PBGA), multi-chip module PBGA;
• μBGA, micro BGA, is a chip size package;
• SBGA (Stacked ball grid array), laminated BGA;
• etBGA, the thinnest BGA structure, the package height is 0.5mm, which is close to the chip size;
• CTBGA, CVBGA (Thin and Very Thin Chip Array BGA), thin and ultra-thin BGA;