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 GBIC >> MCM >> Design - Packages

Design - Packages
There are only two primary structures that make up and MCM, the interconnect and the package. It's simple to say, but not so simply in practice to accomodate all of a customer's requirements without reverting to custom package designs. Many MCM engineers attempt to standardize on packages in order to lower the NRE costs to a customer while others customize every facet of the design to maximize the performance against customer requirements. Both approachs utilize the two, basic packaging concepts - a drop-in substrate with enclosing package, or an integrated package-interconnect.

Overview Metal HTCC LTCC Laminate

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Overview

As I've mentioned, packages come in two generaly flavors - those in which the interconnect is fabricated separately and dropped into the package as part of the assembly process, and those in which the interconnect is an integral part of the package. There are 3 basic categories of materials used for packages:
  • Metal
    In the days when analog circuits were king, metal packages were the technology of choice. Not only were metal forming technologies more readily available at that time, but the natural shielding of the package for analog designs combined to define a good solution to the packaging problem. Fortunately, the module I/O count was very low by today's standards, further satisfying the limits of the package I/O technology - hermetic, glass-sealed feed-thru leads.
  • Ceramic
    Ceramic modules are the choice where environmental conditions are most difficult. Ceramics are essentially impervious to most environmental conditions, and are capable of providing the high degrees of hermeticity when compared to the competing laminate technologies. Once the package of choice, this package has mostly been relegated to custom and/or military applications - where the hight cost of low volume manufacturing runs can best be absorbed.
  • Organic
    The general term laminates is often used in preference over organic simply because most MCM packages of this category use laminated PCB interconnects as the package. But you should note that many organic PCB structures are made using sequential fabrication techniques as well. The basic benefits of organic packages are the low cost and the huge international infrastructure for fabricating such interconnects.

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Metal Packages

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High Temperature Cofired Packages

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Low Temperature Cofired Packages

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Laminate Packages