Multilayered Ceramic Packages

The substrates that we have been describing are single-layer substrates. There are a wide variety of multilayered packages that perform the same function as the single-layer substrate—that is, as a carrier for components that also provide insulation of one component from another, but which occupy a smaller area since some of the layers are internal to the package. The next section will discuss these multilayered ceramic packages in some detail, since they are manufactured primarily by tape casting. 

Multilayered ceramic packages (MLC) would not exist if tape casting had not been invented. The basis for the multilayer industry is the 

The major advantages of this technology include the ability to provide high-density interconnections with relatively short path lengths, which lead to higher-speed computers excellent thermal dissipation the ability to operate at elevated temperatures, excellent structural strength provision for a hermetically sealed transistor enclosure, excellent dimensional stability, and an overall low thermal coefficient of expansion. 

The original multilayered ceramic packages were developed around what is today known as a high-temperature cofired ceramic (HTCC). In this technology the ceramic was primarily an alumina-based 

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Figure 13. Process flow for cofired multilayer ceramic packages. (Used by courtesy of Interamics.)...

Knickerbocker, S.H., Kumar, A.H. and Herron, L.W. (1993) Cordierite glass-ceramics for multilayer ceramic packaging. Am. Ceram. Soc. Bull. 72, 90-5. 

Extraction Replication (Crystals In Fired Moly). The multilayer ceramic package that Is used by IBM has a sintering operation In which the alumlna/glass body undergoes slnterlng-wlth-a-llquld phase simultaneously with the firing of the molybdenum lands. 

First presentation on multilayered ceramic packages prepared from tape-cast materials H. Stetson and B. Schwartz, "Laminates, New Approach to Ceramic Metal Manufacture Part 1 Basic Process." Am. Ceram. Soc. Bull., 40 [9] 584 (1961). 

The next step in part fabrication is the generation of a hole pattern in the tape-cast material. These holes are used to interconnect layers in a multilayered ceramic package or to interconnect the two surfaces of a substrate. The holes are generally circular, but they can be most any other shape. This section will address the techniques and equipment used in the via generation process. 

FIGURE 1.1.1 Process flow for multilayer ceramic package fabrication. 

The lead-on-substrate MCP could also be implemented using a cofired ceramic package with the leads brazed on and finished by cover coating with a suitable encapsulant or hermetic seaUng of the assembled ICs. Chapter 7 of Ref. 7 gives a detailed discussion of the cofired multilayer ceramic package manufacturing processes. 

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