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Interconnect technology is expanding to include printed systems. As detailed in the iNEMI Organic and Printed Electronics Roadmap,  there is a bounty of printed electronics technologies, such as “drop on demand,” Xerography, micropen, et al. It is not within the scope of this chapter to detail the principles, advantages, benefits, etc., of each technology; rather, it’s important for electronic packaging and interconnect designers to understand the salient features of printed electronics and digital fabrication technologies as well as the similarities and differences among conventional printed circuit technologies and processes.

Digital fabrication can be viewed as the creation of electro-optical-mechanical-thermal systems by means of either parallel or sequential additive processes, as controlled by a digital device. As with any technology, the designer should consider and take advantage of the technology’s features before applying it. In the case of digital fabrication, those features include adaptive, additive, roll-to-roll processes and the ability to fabricate on curved, conformal, curvilinear surfaces.

Most often, digital fabrication is accomplished in a roll-to-roll process, but panel-based digital fabrication is also possible. The revolutionary aspect of digital fabrication, as compared to conventional printed circuit board, is the ability to simultaneously create electronic and/or optical devices, electrical interconnects, mechanical structures, and thermal management systems. For example, using conventional technology and processes, a television remote control is produced by packaging and assembling tens to hundreds of electronic devices onto PCBs and subsequently assembling the PCBs, interconnect, LED, touchpad, etc., within a plastic housing. Digital fabrication would allow the entire system to be fabricated, layer-by-layer, in a fashion similar to that of stereolithography apparatus (SLA). Applying digital fabrication requires a transformation in thinking by electronic system designers: digital fabrication provides for the 2D and 3D design and fabrication of systems that are not limited to electrical interconnect and passive devices.

In digital fabrication, materials with the necessary electrical, mechanical, thermal, and optical properties to form the desired devices, systems, etc., are deposited onto a substrate. Polymer and plastic are the most common substrate materials, due to their compatibility with low-cost, high-through-put processing. However, rigid substrates can be used as well. The materials used in forming electronic devices and interconnect are, typically, conductive inks and dielectrics. Any material, however, that can be dispensed by the dispensing system (“print head” plus material control) can be used. The materials used in forming mechanical and thermal structures, likewise, are defined by the application and limited by the capabilities of the “print head” and material control system. To date, biological, organic, optical, and many types of functional materials have been printed.

Given that devices and structures are being “built-up,” layer-by-layer, there are key differences in the resulting device and feature attributes. For example, vias can be formed as filled or partially filled and can be conductive and/or nonconductive, electrically and/or thermally. Unlike conventional pcb circuit board technology and processes, digital fabrication can be used to produce vias of any geometry. Similarly, individual traces can be of any geometry and can be produced to effect sidewalls with attributes to support application needs. Conductors produced using conventional pcb manufacture technology have sidewalls that are tapered or orthogonal. Digital fabrication could be used to produce conductors with irregular sidewall features, as related to specific performance or mechanical applications. Furthermore, in digital fabrication, mechanical, thermal, and other features could be included in the construction of conductors.

The ability to produce large-area, fine-pitch flexible interconnect is driven by a number of elements. Those elements are comprised of materials, processes, facilities, equipment, design, and engineering support. The demand for thin, fine-pitch flexible interconnect requires unique considerations that are not possible with traditional printed circuit board (PCB) technologies. Fine feature requirements, over large areas, must have clean process facilities and tooling. Most PCB facilities have limited clean-room capabilities and are often restricted to Class 10,000 in the pattern transfer area. Fine-pitch interconnect processing of structures with less than 100um pitch requires clean process areas—i.e., Class 100-1,000–to be able to produce interconnect with acceptable yield. The clean-room facilities must also be augmented with tooling, processes, and operator controls for low-defect densities.

Defects found on flexible interconnect can include trapped fibers, hole in trace, and conductor-to-conductor shorts. These defects are the result of particles generated from process materials or the process environment, including tooling, operators, and the process facility. Many PCB manufacturers have designed clean process tools that contain the work and protect it from an unclean facility.

Flexible printed circuits, with respect to features and process environments, are at the intersection of their semiconductor and printed circuit board equivalents. Fine-pitch flexible interconnect resides at the intersection; tooling, facilities, and expertise from the semiconductor industry are more closely coupled to fine pitch.

2 Different Amplifier

Different amplifier can only magnify the D-VALUE of 2 signals, but won’t magnify general voltage signal. If design job of different amplifier and Printed Circuit Board aren’t reasonable, when signal level in the low status, general voltage will generate a small differential interference signal. Due to the high input impedance of different amplifier, any parameter imbalance on input point will bring much great interference to circuit. Therefore, during the printed circuit board design process, it has to ensure physical structure of amplifier complete symmetry.

There is a leakage resistance exist in the input point of different amplifier, it can take an effect of imbalance voltage deviation. Designer can solve this problem through add protective device on the input circuit, protective device can circle the signal wire, if it can keep the same voltage with 2 input signal low level, as a result of that, positive resistance value will increase. This device can ensure signal source terminal and protector keep the same voltage with low level of signal source.