Additive printed wiring process

These trends have led to the larger use of nonorganic base substrates, such as aluminum and soft iron. In addition, alternate ways to create boards have been developed. These will be discussed in this chapter, along with the traditional board structures and processes. The terms printed wiring board, PWB, and board will be used synonymously. Also, the words laminate, substrate, and panel will be used interchangeably. 

N. Ohtake, New Printed Wiring Boards by a Partly Additive Process, PC World Conference IV, Tokyo, Paper No. 44, June 1987. 

S. Imabayashi, et al., Partly-Additive Process for Manufacturing High-Density Printed Wiring Boards, IEEE Trans. 0569-5503/92/0000-1053,1992. 

H. Akaboshi, A New Fully Additive Fabrication Process for Printed Wiring Boards, IEEE Trans, on Comp., Hybrids and Mfg. Tech., Vol. CHMT-9, No. 2, June 1986. 

Paper Production and Properties. During the paper production process, the wood pulp is mixed into an aqueous slurry, which is poured onto a continuously moving wire mesh and drained by gravity. Additional water is then squee2ed out of the paper by a felt web pressed from above. This pressed side, referred to as the felt side, has smaller, finer fibers and is therefore smoother. It is also the preferred printing side. 

Inks having a fluorocarbon base can be used to print stripe patterns on wire for identification. In practice a wheel coated with the desired color runs along the wire prior to the sintering step of the manufacturing process. For more than one stripe, additional wheels are needed. The ink is sintered at the same time as the insulation. PTFE and FEP dispersion have been used as the base to produce ink. Inorganic pigment that is stable under the sintering conditions of polytetrafluoroethylene must be used. 

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