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An Introduction of BGA Packaging Technology

Modern information age has seen rapid development of electronics industry, leading electronics products such as computers and cell phones to be increasingly prevalent. People start holding constantly increasing demands in terms of functions and performance of electronics products while constantly decreasing demands in terms of volume and weight. Up to now, multiple functions, light weight and miniaturization have become the leading development trend of modern electronics products. To achieve this goal, feature size of IC (integrated circuit) chips has to be downsizing with their complexity level constantly rising. As a result, I/O count starts uprising and I/O density of packaging starts uprising as well. To be compatible with the development requirement, some advanced high-density packaging technologies come into being among which BGA (ball grid array) is a primary type because it demonstrates more competent advantages than the other packaging forms on light weight, miniaturization and high performance.

The advent of BGA package came as early as the beginning of 1990s and it has grown to be a mature high-density packaging technology. BGA packaging technology has been widely applied as packages in PC chips, microprocessors, ASIC, array, memory, DSP, PDA, PLD etc.

Properties of BGA Packaging

BGA package implements electrical connection between circuit I/O end and PCB (printed circuit board) depending on array of solder balls under package base. Components with BGA packaging technology are a type of SMDs (Surface Mount Devices). Compared with traditional leaded devices such as QFP, PLCC etc., BGA packaging components feature the following properties:

• High Count of I/O

The number of I/O is determined by device size and solder ball pitch. Because solder balls with BGA packaging are distributed as an array at the bottom of base, BGA package can dramatically increase I/O count of components, shrink package size and save assembly space. Generally speaking, package body volume can save at least 30% of space with BGA packaging technology applied in the case of equivalent leads.

• High Pass Rate of Assembly with Cost Reduced

Leads of traditional QFP and PLCC components are evenly distributed around packages with lead pitch being 1.27mm, 1.0mm, 0.8mm, 0.65mm or 0.5mm. As count of I/O goes up, lead pitch has to become definitely downsizing. When pitch is less than 0.4mm, precision of SMT equipment fails to meet corresponding demands. Furthermore, leads tend to become deformed easily, assembly failure rate will therefore rise up.

BGA packaging components, however, arrange solder balls in an array at the bottom of base and can hold higher count of I/O. Standard pitch of solder balls is 1.5mm, 1.27mm and 1.0mm. Fine pitch BGA features their pitch to be 0.8mm, 0.65mm and 0.5mm, compatible with SMT equipment.

Other properties of BGA packaging include:
• Contact area between BGA solder balls and base is large and short, beneficial for thermal dissipation.
• BGA features shorter leads, shortening signal transmission path, reducing inductance and resistance of leads and optimizing circuit performance.
• BGA can obviously improve co-planarity of I/O end, dramatically decreasing loss as a result of bad co-planarity during assembly process.
• BGA works suitable on MCM package and can implement high density and high performance of MCM.
• Both BGA and fine pitch BGA are more reliable than fine pitch lead ICs.

Classifications and Structures of BGA Packaging

BGA comes in numerous types of packages with structure mostly square and rectangle. In accordance with distribution type of solder balls, BGAs can be classified into peripheral, matrix and complete array. In accordance with different material of base, BGAs can be classified into PBGA (plastic ball grid array), CBGA (ceramic ball grid array) and TBGA (tape ball grid array).

• PBGA Packaging

PBGA relies on BT resin or glass laminate as base and plastic as sealing material with eutectic solder 63Sn37Pb as solder ball material. Connection between solder ball and package doesn't need extra solder. Some PBGA packages come in cavity structures, classified into upward cavity and downward cavity. PBGA with cavity structure come to strengthen their thermal dissipation so they are also called EBGA.

PBGA features the following advantages:
a. Better thermal compatibility with PCB board
b. Higher alignment between solder balls and pads
c. Lower cost
d. Excellent electrical performance

• CBGA Packaging

CBGA has the longest history among all types of BGAs. Featuring a multi-layer ceramic as base, CBGA takes advantage of a metal cover plate to get BGA components soldered onto base to protect chips, leads and pads. Solder ball material is high-temperature eutectic solder 10Sn90Pb and connection between solder balls and package depends on low-temperature eutectic solder 63Sn37Pb.

Advantages of CBGA package include:
a. Better air tightness and higher anti-humidity, leading to long-term and high reliability
b. Better electrical insulation than PBGA
c. Higher packaging density than PBGA
d. Higher thermal dissipation than PBGA

Disadvantages of CBGA package include:
a. Due to large difference between ceramic base and PCB board in terms of CTE (co-efficient of thermal expansion), low thermal compatibility is featured by CBGA that tends to fail as a result of solder joint fatigue.
b. Higher cost than PBGA
c. Higher alignment difficulty on solder balls at the edge of package.

• CCGA Packaging

CCGA, a short form of ceramic column grid array, is an improving version of CBGA. The difference between CCGA and CBGA is that CCGA takes advantage of solder column whose diameter is 0.5mm and height is 1.25mm to 2.2mm to replace solder balls with a diameter of 0.87mm so that solder joints of CCGA are more capable of defeating solder joint fatigue.

• TBGA Packaging

TBGA is a cavity structure with two interconnection types between chips and base: inverted soldering bonding and lead bonding.

Advantages of TBGA include:
a. Better thermal compatibility between tape and PCB board
b. Self-alignment of solder balls can be used by TBGA, that is, surface tension of solder balls to meet alignment requirement between solder balls and pads.
c. Lowest cost among all BGA packages
d. Better thermal dissipation than PBGA

Disadvantages of TBGA include:
a. Sensitive to humidity
b. Multi-class combination of different materials is bad for reliability maintenance.

PCBCart Purchasing High-Quality BGA Components and Ensuring Their Optimal Performance in PCBA

Due to over 10 years' experience in this industry, PCBCart has been capable of purchasing high-quality BGA components of all types mentioned above from reliable component manufacturers or distributors around the world. Prior to their applications, each of BGA components has to be rigorously inspected so that their optimal performance can be achieved in your final products. For more information about our purchasing capabilities, please contact us.

Helpful Resources
A Brief Introduction of BGA Package Types
Quality Guaranteed BGA Components Sourcing Service from PCBCart
Full Feature PCB Manufacturing Service from PCBCart
Advanced Turnkey PCB Assembly Service from PCBCart
Factors Affecting the Quality of BGA Assembly
Solder Ball Issues of BGA Components and How to Avoid Them

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