Outlook for PCB

With the development of smartphones, the second generation of HDI was born at the beginning of the 21st century. While retaining laser-drilled microvias, stacked vias began to replace staggered vias, and in combination with “any-layer” construction techniques, HDI boards ended up with line widths/spaces of up to 40 μm.

This any-layer approach is still based on the reduced-format process, and it’s safe to assume that most high-end HDI for mobile electronics is still based on this technology. However, in 2017, HDI started to move into a new phase of development and began to move away from the subtractive method process to a process based on graphic plating.

For example, in a 0.3-mm pitch BGA design, two alignments are crossed between the BGA pads, with a through-hole size of typically 75 microns and a pad size of 150 microns. The layout design requires a 30 ?m/30 ?m line width/line pitch. Realizing this fine line structure with existing subtractive processes is challenging. Etch capability is one of the key factors where finished copper thickness and plating uniformity need to be optimized along with the imaging process. This is why the PCB industry is now adopting the mSAP process. Compared to subtractive processes, the mSAP process makes it easy to produce lines with optimized conductor shapes, where the top width of the etched end face of the PCB is almost equal to the width of the bottom end of the line across the entire PCB panel – the line shape is easily controllable. mSAP has the added advantage of utilizing existing resources and technology, using standard PCBs. Another advantage of mSAP is that it utilizes existing resources and technologies, adopts standard PCB processes such as drilling and plating, and uses conventional materials to provide good adhesion between the copper and the dielectric layer, ensuring high reliability of the final product.

The semi-additive method (mSAP) and the modified semi-additive method (amSAP) are modified and advanced modified versions of what is now expected to be the predominantly used process for next-generation HDI PCBs.

Due to miniaturization, HDI and microvias provide a huge boost to high density. These technologies will follow the IC cell geometry as it continues to evolve and become smaller. So the next revolution will be in optical conductors.

As the process of ultra-large-scale integrated circuits continues to improve the processor performance of computer systems, but at present, electronic computers continue to use traditional copper wires to realize the chip-chip, processor-processor, circuit board-circuit board connection, the International Semiconductor Technology Blueprint ( ITRS) has pointed out that future electronic systems will be limited by the interconnection between the chip, because the main problems faced by the current main copper wire are: (1) high-speed signal distortion, bandwidth is limited; (2) the transmission loss of the metal wire with the increase in signal frequency increases, restricting the transmission of high-frequency signals distance; (3) susceptible to electromagnetic interference; (4) high power consumption and so on.

Optical communication has many advantages that traditional electrical signals do not have, such as high bandwidth, low loss, no crosstalk, anti-electromagnetic interference and so on. In fact, optical fiber has completely replaced the traditional copper wire for long-distance communication for decades, the future development trend is that the optical interconnection of the communication distance will gradually become shorter, from the long-distance communication between countries to the future of the chip within the signal transmission.

At present, the industry generally believe that when the single channel rate of 25 Gb / s or more, whether from the technical realization or cost comparison, electrical interconnect will face great challenges. Therefore, in order to overcome the electronic computer “bottleneck”, it is necessary to change the traditional copper-based interconnection, the introduction of optical technology into the electronic system, with the new optical interconnect instead of the traditional electrical interconnect, in order to significantly increase the operating speed of the computer and to promote the development of high-speed information and communication networks to meet the needs of social development.