Multilayer ceramics production process

Ceramic boards are currently widely used in high-performance electronic modules as interconnection substrates. They are processed from conventional ceramic precursors and refractory metal precursors and are subsequently fired to the final shape. This is largely an art a much better fundamental understanding of the materials and chemical processes will be required if low-cost, high-yield production is to be realized (see Chapter 5). A good example of ceramic interconnection boards are the multilayer ceramic (MLC) stractures used in large IBM computers (Figure 4.11). These boards measure up to 100 cm in area and contain up to 33 layers. They can interconnect as many as 133 chips. Their fabrication involves hundreds of complex chemical processes that must be precisely controlled. 

Colomban, P, Menet, M., Mouchon, E., Courtemanche, C., and Parlier, M., Composites ceramique-ceramique multicouches elabo-res en utihsant un precur-seur d interface et un precurseur de matrice [Multilayer fiber-matrix ceramic composite material and process for its production], French Patent nos. (ONERA) FR 2672283 (Feb. 4, 1991) and EP 0 498 698 (Jan. 29, 1992), and U.S. Patent no. 07/830.904. 

Pyro-dad. Trade-name. A process for depositing multilayer coatings of metals and ceramics. (Aremco Products Inc. USA). Pyroelectric Materials. Pyroelectrics develop an observable spontaneous electric moment only when heated. Cf ferroelectrics. Pyroelectric ceramics include some niobate-zirconate systems, barium titanate modified with zirconia and hafnia, and lanthanum-modified lead... 

Structure. Figure 23.21 shows the structure and cross-sections for an ALIVH product. The PCB consists of laser-produced blind vias. The core material is an epoxy-aramid laminate. The man-made aramid filaments are ideal to be cut with a CO2 or UV laser. If the DuPont Kevlar filaments are added, then the resulting material wiU have a very low coefficient of thermal expansion (CTE).This is useful for mounting ceramic packages and for direct attachment of flip-chip integrated circuits. The structure can be as simple as a two-sided PCB or as complex as a many-layered PCB. The vias consist of a copper-epoxy paste that connects the top and bottom copper foil. If used as a prepreg layer without copper, the vias connect the various ALIVH layer pairs into a multilayer structure. This is not a sequential build-up process, but rather a parallel build-up process. 

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