Printed circuit boards deposition techniques

The microstructure was realized by a dry-film photoresist technique and based on established techniques from printed circuit board technology [142], Dry resists are available as thin films, e.g. of thickness 50 or 100 pm. The resist films are encased in other polymer materials which are later removed. The resist films can be deposited on various base materials such as silicon or polymers giving mechanical stability. Lamination is carried out with a roller laminator. Then, exposure is made and spray development without any solvents follows. The process steps can be repeated at multi-laminated structures. Closed structures can be made in this way. 

The manufacture of a three-dimensional circuit device from a molded plastic such as the demonstration part shown in Figure 1 differs from the traditional printed circuit board. Different imaging techniques are required due to the three-dimensional features of the devices. In addition, the metal comprising the traces on the surface of the substrate are now deposited rather than formed from the laminated copper foil. 

Fine patterns of polymeric material are widely used in the electronics industry. They are required in the manufacturing of integrated circuits, printed circuit boards and solder masks for the latter. However, photopolymerization finds only limited application in this area. Photocrosslinking and photochemical enhancement of the rate of dissolution are primarily used. Larger structures can also be made by screen printing. In this technique, the photopolymerizable material is deposited pattern-wise and then irradiated in an overall exposure. 

Screen or stencil printing can be used for adhesives as well as solder paste. The low viscosity of most flux solutions precludes their successful dispensing by this technique. The adhesive or solder paste is deposited through openings in the stencil or screen called apertures. The apertures are located over the locations on the circuit board where the adhesive or solder paste is required. The placement of material is performed by a squeegee pushing a quantity of adhesive or paste ahead of it, over the screen or stencil, as illustrated by Fig. 40.16a. 

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