Printed circuit boards printing

Processing of printed circuit boards Printed circuit boards are subjected to special treatment in order to recover their entire metal content. 

The term prepreg is used for the non-conducting semi-cured layers of FR4 which are used to separate the conducting layers of a multiplayer printed circuit board. Printed circuit broad laminates comprise a layer of prepreg bonded between sheets of copper foil. The Japanese NEC company is understood to be marketing a self-extinguishing reinforced glass-epoxy resin for PCB. 

MIL-PRF-31032, Printed Circuit Board/Printed Wiring Board, General Specification for ... 

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

Prince William Sound Prinivil Prins reaction Print bonding Printed circuit board... 

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). 

Cadmium usage, illegal in most of Europe, is being discouraged elsewhere. The U.S. military has cadmium specifications for electronic, fastener, and marine equipment, which requires only cadmium. Tin is being substituted for tin—lead as a metallic etch resist during printed circuit board production. 

Fig. 1. The different levels of electronic packaging (0) chip (1) chip carrier (2) printed circuit board (electronic card assembly) (3) rack and (4) system (2).

Most of the laminates used for rigid printed circuit boards have been classified, by the National Electrical Manufacturers Association (NEMA), according to the combination of properties that determine the suitabiHty of a laminate for a particular use. Eiber reinforcements make laminate-effective properties orthotropic. 

Because the heat distortion temperature of cured epoxy resins (qv) increases with the functionality of the curing agents, pyromellitic dianhydride is used to cross-link epoxy resins for elevated temperature service. The dianhydride may be added as a dispersion of micropulverized powder in liquid epoxy resin or as a glycol adduct (158). Such epoxies may be used as an insulating layer in printed circuit boards to improve heat resistance (159). Other uses include inhibition of corrosion (160,161), hot melt traffic paints (162), azo pigments (163), adhesives (164), and photoresist compounds (165). 

Blends have also been prepared by dissolving DMPPO in a monomer and then polymerizing the monomer. An example is an epoxy—DMPPO blend prepared by curing a solution of DMPPO in Epon 828 at 85°C with an alurninum—tetramethylguariidine catalyst. Some copolymer formation is observed. The solutions can be appHed to glass cloth before curing to produce prepregs for composites in appHcations such as printed circuit boards (67). 

Polysulfones also offer desirable properties for cookware appHcations, eg, microwave transparency and environmental resistance to most common detergents. Resistance to various sterilizing media (eg, steam, disinfectants, and gamma radiation) makes polysulfones the resin family of choice for many medical devices. Uses in the electrical and electronic industry include printed circuit boards, circuit breaker components, connectors, sockets, and business machine parts, to mention a few. The good clarity of PSF makes it attractive for food service and food processing uses. Examples of appHcations in this area include coffee decanters and automated dairy processing components. 

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... 

Because of the ease with which they can be soldered, electroplated tin—lead coatings of near eutectic composition (62 wt % tin) are extensively used in the electronics industry for coating printed circuit boards and electrical coimectors, lead wires, capacitor and condenser cases, and chassis. 

Phenohc/adhesives adhesives / sealants / gaskets abrasives and break pad binders printed circuit boards stmctural composites /laminates Metal/glass binders metal oxide binders retroreflective coatings glass optical coatings Hard copy printing inks toners... 

---