POLYMER THICK FILM TECHNOLOGY
The area of additively refined flexible circuits has actually been controlled by polymer thick film (PTF) technology. PTF has been in use for a very long time in calculator keyboards, screens and the like, but recent developments in polymer ink modern technology have actually caused increases in conductivity that make PTF an attractive alternative to engraved metal flex PCB for sure applications. At the present time, PTF modern technology is being modified as a technique for printed electronic devices make. A later chapter will cover the topic in more detail.
The procedures used in PTF flex PCB circuit manufacture are relatively straightforward. The circuit pattern of conductive ink is screen printed into the surface of a flexible polymer using a screen of appropriate mesh as well as the conductive metal-filled ink is healed utilizing either UV radiation or warm.
The pattern is after that usually safeguarded either by a screen-printed covercoat or by a pre-machined (i.e., pierced or punched) coverlayer. Frequently PTF flex PCB circuit products integrate screen-printed resistors also. The graphite inks utilized are also generally made use of as a call finish for switches. Because polyester films are normally utilized, a heat-forming action can be introduced, creating the flex PCB circuit to take and also hold a particular shape. Low-priced dome switches are created thus. Dome buttons are reviewed in even more detail later in the chapter.
PLATEABLE TONER TECHNOLOGY
Plateable toner innovation (PTT) has actually been discovered as a prospect for additive flex PCB circuit manufacture. The technology is based upon the usage and down payment of a catalytic and plateable toner. The catalytic toner is deposited straight on to the surface of a flexible polymer movie that is advanced in roll kind utilizing a modified printer. The circuit patterns are ultimately layered with electroless/electrolytic copper.
A special quality of PTT is that it permits a part to be gone down directly right into manufacture via computer with no intermediate steps. This enables circuits to be built financially at a run amount of one. In addition, the modern technology allows for the manufacture of circuits of virtually limitless size.
A variant on this idea has actually been presented in the last few years by Conductive Inkjet Technology in England. The basic idea is similar, however the procedures differ in that the more recent procedure utilizes an ink jet printer to print the circuit pattern with a catalytic ink. The rest of the handling is essentially the same. The more current procedure, nevertheless, appears to be limited to using electroless only, therefore sheet resistance worths are restricted to 50 to 20 milliohms/square, compared to typically utilized copper aluminum foil which has a sheet resistivity value of 0.68 milliohms/square at a 25µm density. This subject will be touched on once more in this chapter and in more detail in the future sections