Building Multilayer Structures

Now that we have discussed the processes that can be used to create multilayer structures, coating, coextrusion, and lamination, the question arises, which process should be used, and when Liquid adhesive systems usually run faster than extrusion laminating and coating systems. If one is using a solvent-based system, there is the issue of whether or not any residual odors that might affect the product to be packaged remain. Water-based systems do not have solvent odors, but they are not necessarily odor-free. 

Extrusion laminations are obviously used to create structures containing paper and foil, but extrusion laminating can be done to join two polymer films, also. One 

Obviously, the equipment that a supplier has available will affect the type of materials offered. Decisions should be based on the needs of the product and the packaging machinery available. Once one has set these goals, compromises because of business issues, such as limited supplier base, economics, etc., maybe necessary. 

Discuss the similarities and differences between extrusion laminating and hot melt laminating. 

Describe the process for making metallized film. Give two examples of packages that use metallized film. What are the major advantages and disadvantages of metallized film, compared to laminations containing aluminum foil  

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Fig. 17 shows the adsorption isotherms of all (undimerized and dimerized) particles. Except for a very fast increase of adsorption connected with filling of the first adlayer, the adsorption isotherm for the system A3 is quite smooth. The step at p/k T 0.28 corresponds to building up of the multilayer structure. The most significant change in the shape of the adsorption isotherm for the system 10, in comparison with the system A3, is the presence of a jump discontinuity at p/k T = 0.0099. Inspection of the density profiles attributes this jump to the prewetting transition in the... 

By changing the device architecture e.g. by building multi- instead of single layer structures the physical and chemical processes in the LED can be greatly altered. For that reason the fundamental properties of the LED, such as threshold voltage, efficiency, emission color, brightness, and lifetime can be optimized in multilayer structures [43J. 

Let us consider a multilayer structure plotted schematically in Fig. 1. It will be taken as a fundamental building block of any more complex guided-wave structure considered here. Let the optical wave propagate along the longitudinal coordinate z, and x is the transversal coordinate. 

Building up multilayered structures in certain elements is often a necessary processing step in order to fulfill various functional requirements. Examples of such garment elements are jacket fronts, waistbands in trousers and skirts, and collar and cuffs in shirts. Multilayered structures should produce desirable bending stiffness, drape, and extension. The use of fusible interhnings for this purpose is an established practice. 

Integration of passives in LTCC is also used to build components. Several elements can be combined in a multilayer structure to achieve a specific electrical function (e.g., a band-pass filter). These small-sized components have terminations allowing surface-moimt assembly operations (land grid, castellation, or ball grid array [BGA]). Depending on the nature of diese passive multicomponent devices, they are referred as monolithic (only LTCC elements) or hybrid [58] (mixture of embedded components and additional surface-mounted elements). Reasons for not implementing all passives in the hybrid type are ... 

Blodgett technique. The enhanced materials stability may make functional siloxane-based systems suitable for device integration and operation. It is noteworthy that standard isocyanate/hydrolysis polymerization chemistry can be used as well to build-up structurally regular multilayers. 

Printed wiring boards (PWBs) with microvia hole structures are called different names, such as HDI, SBU (sequential build-up), and BUM (build-up multilayer). However, HDI covers a broader range of high-density wiring boards such as extremely high-layer-count multilayer boards (MLBs) without microvia holes. MLBs with microvia holes are not necessarily built sequentially, nor do they necessarily have build-up structures.These definitions are not appropriate for the discussions in this chapter, and therefore we shall address MLBs with microvia holes simply as microvia hole boards (all microvia hole boards are essentially multilayer boards). 

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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