Printed-circuit substrates

The past introduction of TP materials into the area of printed circuit substrates has led to a broader type of application for the circuits. The products can be injection molded and the circuit applied to a molded part which will have a molded-in connector structure used to interconnect the device to the rest of the system. By combining the connector and substrate functions, it is possible to make very compact printed circuit units. 

Polyetherimide is used in a variety of applications. Electrical applications include printed circuit substrates and bum-in sockets. In the automotive industry, PEI is used for under-the-hood temperature sensors and lamp sockets. PEI sheet has also been used to form an aircraft cargo vent. The dimensional stability of this polymer allows its use for large flat parts such in hard disks for computers. 

The polysulfones are used for manufacturing of printed-circuit substrates, moving parts of relays, coils, clamps, switches, pipes socles, potentiometers details, bodies of tools, alkaline storage and solar batteries, cable and capacitor insulation, sets of television and stereo-apparatuses, radomes. The details under bonnet, the head lights mirrors, the flasks of hydraulic lifting mechanisms of cars are produced from polysulfones. 

Chip on board (COB)—the die is mounted directly on the printed circuit substrate (or board). See also tape automated bonding (TAB) and tape carrier packages (TCB). 

Welsher,T. L., Mitchell, IP, and Lando, D. I, CAF in Composite Printed Circuit Substrates Characterization, Modeling and a Resistant Material, IEEE Reliability Physics Symposium Proceedings, Vol. 18,1980, pp. 235-237. 

Z. Lai and J. Liu, Anisotropically Conductive Adhesive Rip-Chip Bonding on Rigid and Flexible Printed Circuit Substrates, IEEE Transactions on Components Packaging and Manufacturing Technology, Part B, Vol 19, 1996, p 644-660... 

Printed circuit boards manufacture is aided by the use of KMnO. Alkaline permanganate solution is used to remove resin smeared on the interior hole wall of multilayered printed circuit boards. Additionally the hole wall is etched, resulting in a surface with excellent adhesion characteristics, for electrodeless copper (250). The alkaline permanganate etchback system containing >60 g/L KMnO and 40-80 g/L NaOH at 70—80°C, is effective for difunctional, tetrafiinctional, and polyimide resin substrates, where the level of etchback is direcdy proportional to the immersion time (10—20 min) (251). 

Alkaline solutions consisting of approximately 160 g/L NaAlnO and 60 g/L NaOH at 75°C and contact times in the range of 15 minutes, exhibit high etch rates for printed circuit boards (252,253). The resulting manganese residues can readily be removed by acid neutrali2ation. Addition of K", Rb", and Cs" as co-ions to an alkaline NaAlnO solution maintains etch rates of resin substrates comparable to solutions of higher NaAlnO concentrations (254). 

Metal powder—glass powder—binder mixtures are used to apply conductive (or resistive) coatings to ceramics or metals, especially for printed circuits and electronics parts on ceramic substrates, such as multichip modules. Multiple layers of aluminum nitride [24304-00-5] AIN, or aluminay ceramic are fused with copper sheet and other metals in powdered form. The mixtures are appHed as a paste, paint, or slurry, then fired to fuse the metal and glass to the surface while burning off the binder. Copper, palladium, gold, silver, and many alloys are commonly used. 

Pig. 2. (a) The cell mount design of the integrated PV array of Pigure 1, which uses laminated conductive and insulating layers on top of an aluminium substrate in a printed circuit board-type panel (7). The array produces 20 kW at 20°C ambient and 850 W/m direct sunlight, and measures 155 m. The lens is a molded acryUc Presnel lens parquet mounted on the front of the array stmcture. The PV panel is mounted on the back of the array stmcture and is... 

The contact ends of printed circuit boards are copper. Alloys of nickel and iron are used as substrates in hermetic connectors in which glass (qv) is the dielectric material. Terminals are fabricated from brass or copper from nickel, for high temperature appHcations from aluminum, when aluminum conductors are used and from steel when high strength is required. Because steel has poor corrosion resistance, it is always plated using a protective metal, such as tin (see Tin and tin alloys). Other substrates can be unplated when high contact normal forces, usually more than 5 N, are available to mechanically dismpt insulating oxide films on the surfaces and thereby assure metaUic contact (see Corrosion and corrosion control). 

In industrial applications of metal deposition a metal M is deposited either on the native metal substrate M or on a foreign metal substrate S. As an example of the former, Cu is electrodeposited on a Cu substrate formed by electroless Cu deposition on an activated nonconductor in the fabrication of printed circuit boards. As an example of the latter, Ni is electrodeposited on Cu in the fabrication of contact pads in the electronics industry. 

In the fabrication of printed circuit boards the sensitizer is applied to the substrate S by immersion of the substrate into the solution for 1 to 3 min. Alternatively, the surface of a nonconductor may be sprayed with sensitizer. Addition of aged stannic chloride (SnC ) solution to the tin sensitizer solution results in an improved sensitizer (17). The improved sensitizer yields a greater number of active centers per unit surface area (greater density) and a more uniform distribution. The density of adsorbed centers, using the conventional and improved sensitizers, is 10 and 10 particles per square centimeter, respectively. The diameter of adsorbed particles for both types of sensitizers is about 10 to 15 A. 

The screen printing process uses a rubber squeegee to force ink through a tightly stretched, finely woven mesh onto various substrates. The basic concept has been refined to the point where large semi- and fully automatic lines are relatively common. Typical products are display printing, industrial and container printing, and printed circuit production. ... 

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