Rear panel processing

The rear panel is where transistors are formed. The fast response required for LCDs requires a switch at each pixel. The switch is a transistor that consists of a gate, source and drain, and channel. The gate metal is applied to the glass substrate and photodeliniated using standard processes. Next, a silicon-based dielectric, channel. 

Figure 5.21 Front and rear flat panel process flows. Array substrate (Top) Color filter (Bottom).

The first major industrial use of thermoplastics (a filled blend of polycarbonate [PC] and acrylonitrile-butadiene-styrene [ABS]) in an automotive exterior door panel, rocker panel, and rear panel was introduced by The Dow Chemical Company in a special process developed for the General Motors Saturn line of vehicles. A formulated blend of nylon 6,6 and polyphenylene oxide (PPO), known as Noryl GTX, also was introduced at the same time in those same Saturn vehicles by General Electric Plastics (now SABIC) using a special assembly line procedure (Figures 9 and 10). 

The RIM process was originally developed for the car industry for the production of bumpers, front ends, rear ends, fascia panels and instrument housings. At least one mass-produced American car has RIM body panels. For many of these products, however, a number of injection moulding products are competitive, including such diverse materials as polycarbonate/PBT blends and polypropylene/EPDM blends. In the shoe industry the RIM process has been used to make soling materials from semi-flexible polyurethane foams. 

In this process, gas (nitrogen) is injected into the molten polymer to form hollow sections inside a part. The gas can be injected via the machine nozzle or through mold nozzles. GAIM is widely employed in the automotive, consumer and furniture industry, especially for parts with thick sections. Typical products are bumpers, dashboards, pillar covers, pedals, rear guidances, automotive door panels and arm rests, handles, copier doors, housings and covers, TV and monitor cabinets, CD-ROM trays, crates, chair legs, etc. [4]. 

Applications for hard RIM products are mainly large automotive parts, such as front and rear bumpers, and rocker panels (see Figure 1.135). The most frequently used materials are polyurethanes reinforced with milled short fibers, which are processed in the so-called RRIM process (Reinforced Reaction Injection Molding). The short fibers increase the stiffness and decrease the thermal expansion in the case of temperature changes. They are abrasive, therefore the molds are made from steel (in small series also aluminum). 

The polyurethanes and polyureas may be formulated to be flexible or rigid, solid or foamed. Fillers and/or reinforcing agents (for example, glass fibers or flake) may be added to one or both components (in which case the process is sometimes known as RRIM—reinforced RIM). A major application of RIM is to produce energy-absorbing front and rear ends and body panels for automobiles. Cycle times of two minutes or less are feasible for such large parts. 

Recent advances in poly (urethane) reinforced reaction injection molded (RRIM) parts has led to use in components such as fenders for small trucks, low-density interior door panels, and higher heat-resistant body panels. Rear fenders on the Chevrolet Silverado and the GMC Sierra trucks (Fig. 2), made of RRIM polyurea, are the first application of a RRIM polymer designed to withstand electrocoat, primer, and topcoat paint line process temperatures. 

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