The manufacturing of HDI PCBs began in the late 1980s. With the successive production of PCBs, the first HDI production began in 1984. Since then, designers and manufacturers have been looking for ways to pack more components in a smaller area. HDI boards are designed and manufactured to comply with IPC-2315 and IPC-2226 standards.
Recently, I have been conducting ESD (Electro-Static Discharge) testing on various electronic products. From the test results, I realized that ESD is crucial: if the PCB design lacks proper ESD protection, static electricity can cause devices to freeze or even damage their components. Previously, I only understood that ESD could damage individual components, but now I see the importance of giving full attention to ESD protection throughout the entire design process.