How PCBs Evolved: From Single-Layer to High-Density Interconnect (HDI)
Release time:
2025-12-31
The origins of the PCB can be traced back to the 1920s, when Austrian inventor Paul Eisler first developed
The origins of the PCB can be traced back to the 1920s, when Austrian inventor Paul Eisler first developed the concept of etched copper traces for radio equipment. Early PCBs were simple single-layer designs—with copper traces printed on one side of a phenolic resin substrate—suitable only for basic devices like tube radios and early calculators. These boards had limited functionality: they could only connect a handful of components, and trace widths were often several millimeters wide, limiting the number of connections per square inch.
By the 1960s, as electronics became more complex (e.g., the first computers), engineers developed double-layer PCBs, with copper traces on both sides of the substrate connected by small holes called "vias." This doubled the number of possible connections without increasing the board’s size. The 1980s and 1990s saw the rise of multi-layer PCBs, with layers of copper traces separated by insulating substrate, connected by plated-through vias. Today, advanced High-Density Interconnect (HDI) PCBs represent the pinnacle of this evolution, featuring up to 50+ layers, microvias (tiny holes as small as 0.1mm in diameter), and trace widths as thin as 0.05mm—thinner than a human hair.
This technological leap has been driven by the demand for smaller, more powerful electronics. For 5G smartphones, HDI PCBs are critical: they allow manufacturers to pack 5G modems, multiple cameras, and high-performance processors into a compact space while ensuring fast signal transmission. Electric vehicles (EVs) also rely heavily on HDI PCBs—modern EVs can contain over 100 PCBs, including multi-layer HDI boards for battery management systems (BMS) that monitor and regulate hundreds of battery cells. These boards must handle high currents and tight spacing, with traces designed to minimize signal interference. Additionally, HDI technology reduces power consumption by shortening the length of signal paths, as electrons travel less distance between components. This efficiency is crucial for portable devices like laptops and wearables, where battery life is a top priority.
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