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As Signal Density Rises, Designers Turn To
Technologies Such As Tape
Ball-Grid Arrays To Fend Off
The Laws
Of Physics.
The growing number of high-performance ICs-with greater functional complexity, higher integration, and improved performance-continues to create a higher standard for IC packaging. In response, advanced interconnect technologies, such as flex-based circuits and tape ball-grid arrays (TBGAs) have stepped up to the plate. With significantly improved electrical and thermal performance over older IC interconnect methods, TBGAs, like other enhanced BGA packages, are becoming ever-more popular.
Recent tests have demonstrated the TBGA's strengths with respect to integration levels, defect levels, joint reliability, and thermal and electrical performance. While the results are highly encouraging, migrating to a new format is never a cut-and-dry decision, as a number of factors must be taken into account. Chief among these is overall cost, mainly affected by the format's compatibility with the existing manufacturing infrastructure. Due to its compatibility with surface-mount-construction techniques, the TBGA may have the edge over competing packaged options.
Why BGA?
For IC interconnect packages, plastic packages with gull-wing leads-particularly small-outline IC (SOIC) and quad flat pack (QFP)-represent the majority of surface-mount-technology (SMT) compatible first-level packages in use today. In the near future, they will continue to be the packages of choice for first-level IC packages. However there are newer alternatives that offer designers an option, and one of those is the BGA.
The reasons for the rising popularity of BGAs are simple: They offer higher reliability, a smaller form factor, improved electrical and thermal performance, and more. According to the Worldwide IC Packaging Market publication, the relatively new BGA will grow by more than a factor of 10, from 0.319-billion packages in 1996 to 3.269 billion in 2001.
Within the BGA family, there are three alternatives: plastic BGA (PBGA), ceramic BGA (CBGA), and TBGA (see the figure). Defined as any BGA package which uses flex circuitry as the substrate, the TBGA delivers many of the advantages of its cousins, and is expected to be a major player within the rapidly growing BGA product family.
TBGA (also called a flex-circuit-based BGA) can include larger high-lead-count packages, as well as small, chip-scale packages (CSPs). The superior wiring density of flex circuitry endows the TBGA with all the advantages...