Multichip module package

M. Pecht, Integrated Circuit, Hybrid, and Multichip Module Package Design Guidelines M Focus on Keliability,]ohxi Wiley Sons, Inc., New York, 1994. 

A substrate is a robust element that provides mechanical support for the die. It can be mounted with more than one die such packages are called multichip modules. Because parasitic capacitance effects are directiy proportional to the dielectric constant, substrate material should have a low dielectric constant. 

Pricing as well as reliability considerations have led to an almost exclusive use of Si-based (i.e. Si and SOI) micro machined devices. Packaging and assembly has focused on ceramics (A1203, AIN, Low Temperature Co-fired Ceramics LTCC), Printed Circuit Board (PCB-) and Surface Mount Device (SMD-) technology and multichip modules (MCM s). 

Pautsch, G. and Bar-Cohen, A., 1999, Thermal Management of Multichip Modules with Evaporative Spray Cooling, ASME Publication, EEP-Vol 26-1, Advances in Electronic Packaging -1999, Vol 1, Proceedings, InterPack 99, Maui, Hawaii... 

In the future, the very hot IC s will be packaged in a thermally efficient module or in a multichip module, which will then be mounted on a more conventional substrate. 

When molded or premolded packages cannot be used for whatever reason, for example, a need for hermetic sealing, modules using ceramic substrates (or PCB-printed circuit board) offer almost unlimited flexibility. They can be used for simple multichip modules containing two or more elements (e.g., a sensing element and an evaluation circuit), may include external components, or may be used to construct complete systems. Stress-optimized package configurations for sensitive microsystems and sensors are no problem (Fig. 5.8.4). 

In assembling hybrid microcircuits or multichip modules, ceramic interconnect substrates fabricated using thin-film or thick-film processes are attached to the inside base of a ceramic or metal package. Generally, film adhesives that have been cut to size are used to attach large substrates (greater than 1-inch square) while either paste or film adhesives may be used for smaller substrates. Substrates may be alumina, beryllia, aluminum nitride, or silicon. 

Multichip packaging involves the attachment and interconnection of a variety of chip devices on an interconnect substrate that may be single layer or multilayer. There are two basic types of multichip packaging hybrid microcircuits and multichip modules. 

Guidelines for Multichip Module Technology Utilization, IPC-MC-790. Lincolnwood, IL Institute of Interconnecting and Packaging Electronic Circuits Aug. 1992. 

Iwami C, Licari JJ, Nakagawa C. New Adhesive requirements for multichip modules, Proc. 5th Inti. SAMPE Electronic Materials and Processes Conf. Los Angeles Jun 1991. Harper PR. Thermoplastic die attach for hermetic packaging. Inti. J. Microelectronics and Electronic Packaging. 4th Quarter 1994 17(4). 

Figure 5.5 Examples of multichip modules in which die-attachment adhesives were used. Top Aluminum/polyimide interconnect (MCM-D) on silicon substrate in Kovar package. Bottom Multilayer thick-film (MCM-C) digital filter.

The major applications of LCP films in electronics are multilayer boards and multichip modules, and flexible printed circuits. Current materials used in the.se applications include polyimide film, high performance thermoplastic film such as polyphenylene sulfide and polyetherether ketone, and fiber reinforced composites such as quartz fiber-polyimide. The price of these materials for electronic packaging is in the range of. 50 to. l(K)/lb, so LCPs can compete very effectively at their current prices. Based on a two to three times increase in price... 

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