In the recent past, there has been a proliferation of new electronic applications that demand smaller form factors, smaller packages, lower power consumption, along with improved and increased functionality. This not only requires better embedded signal processing, but also superior imaging interfaces and power management. In addition, all the above requires integration within tighter dimensions and, most often, flexible substrates.
Printed circuit board manufacturers, like PCB Trace Technologies Inc, assess this trend poses innumerable challenges to conventional PCB manufacturing technologies. Earlier, the electronics industry used rigid, flat-surface circuit boards as their mainstay. However, with the emergence of flexible and wearable electronics, mobile technologies, IoT devices, and other compact systems, the trend has shifted to the development of new, flexible, and advanced miniaturized PCBs. The design of these flexible boards allows fitting them to the contours of ever-shrinking devices. Designers are struggling to adapt to the new generation of PCBs that bear little resemblance to the preceding generation.
Because of the above trends, designers are following production technologies that offer thinner copper tracks, transmission lines that support high-speed signals, complex impedance controls, and innovative via placement strategies. This has also resulted in the use of newer substrate materials and increased the reliance on embedded devices. With all the above, there is an imposition of substantially numerous constraints on the design stages of a PCB, significantly impacting the power management, system functionality, reliability, and overall success of the project.
New Challenges in PCB Design
In the new generation of compact electronic devices, one of the critical considerations is the battery life. Now, this affects the design of any PCB in several ways. Designers must be aware of signal loss and issues of signal propagation that often result in battery life being shortened. This requires a strong focus on signal integrity, EMI issues, and power management. This is especially true for flexible PCBs, as signal impedance control may suffer when flexing of the PCB skews high-speed signals.
To counter the above challenges to signal transmission and interference, designers may need to add passive devices like inductors, capacitors, and resistors to the circuit. With PCB miniaturization, there can be lack of available space for the extra components, forcing the designer to opt for embedding them within the board. However, embedding the passive devices within circuit boards is not a developed, mature capability, and can result in the generation of functional issues such as reduced reliability or power issues. Moreover, embedding components imposes numerous restrictions on the design flow.
Newer compact electronics often improve their functionality by employing near-field RF communications, and in most cases, this function requires embedding during the PCB design. While conventional electronics houses RF components within rigid, rugged, and high-performance material structures, compact devices can use only thin and flexible materials. This forces designers to step outside the principles of mainstream PCB design. For instance, copper traces must be formed with greater precision, while the spacing between two adjacent traces must be further narrowed. Such design also affects the placement of vias within the board layers, while also impacting the positioning and size of such interconnects. The designer may need to substitute regular materials with alternatives to strengthen vias where the surrounding layers are not of the glass-fiber composition as in conventional rigid boards.
Manufacturing Innovations in PCB Miniaturization
PCB manufacturers are resorting to many innovative technologies to meet the key challenges of the newer generation. One of them is DI or direct imaging system. Manufacturers are using this technology to form very thin copper traces, down to 10-microns. With a proper DI system in place, manufacturers are able to reach a balance between high registration accuracy on one hand, with optimal quality on the other, even with a high production throughput. Changes in PCB topography, and higher precision and uniformity of traces requires a suitably high depth of focus. DI systems offer a low-cost alternative to expensive front-end lithography techniques. With continuous improvements in position of solder mask, the flexible PCB industry is set to breach the sub 10-micron traces. For instance, with direct imaging and mSAP, the advanced HDI PCB technology can easily fabricate 10-micrometer features.
Simultaneously, manufacturers are employing advanced UV laser drill systems to make small vias in a wide range of materials with varying strength and thickness. These materials include Polyimide, ABF, ceramics, resin, metal, mold compounds, and solder resists. The laser drilling system does not damage the material at the bottom of the via, leaves no residue at its top, and there is no undercut. In addition, the registration accuracy is close to 9 microns.
The systems above help in streamlining the manufacturing processes necessary for modern electronic devices, especially as they become smaller, thinner, flexible, and with improved functionality. In fact, manufacturers are using these systems not only to improve the manufacturing precision and quality of their miniaturized PCBs, but also to increase the production throughput substantially.
Conclusion
PCB manufacturers are investing in these advanced production systems with a view to improve their aggregate yield, thereby improving their profits. Traditional OEMs tend to avoid producing high-functionality devices with miniature PCBs because of concerns with yield management. However, for the new generation of printed circuit boards, the imaging, laser drilling systems, and inspection systems reduce the risks of yield management to a considerable extent. Simultaneously, these systems allow the use of smaller dimensions with newer substrate materials, while improved repair capabilities help to keep yield at acceptable levels. The innovative systems accommodate the stringent constraints that continuous miniaturization imposes on PCBs.
