HDI (High-Density Interconnect) PCB fabrication techniques refer to the methods used to manufacture PCBs with high-density interconnections and advanced features. These techniques are essential for producing smaller, lighter, and more complex electronic devices.

Here are some common HDI PCB fabrication techniques:

1. Microvia Technology: Microvias are tiny drilled holes used to create connections between different layers of a PCB. They allow for higher routing density and reduce signal interference. Laser drilling or mechanical drilling techniques are used to create these microvias.

2. Sequential Lamination: In sequential lamination, multiple layers of the PCB are fabricated separately and then laminated together. This technique allows for increased layer count and finer trace and space widths.

3. Build-Up Technology: Build-up technology involves building multiple layers of the PCB on a core layer, which is usually a thin FR-4 or polyimide material. This technique enables the creation of complex multilayer structures with high wiring densities.

4. Laser Direct Imaging (LDI): LDI is a precise imaging technique that uses lasers to directly expose the PCB's photoresist, eliminating the need for photomasks. It increases accuracy and allows for finer features and smaller via sizes.

5. Thin Core Substrates: Using thinner core substrates, such as ultra-thin FR-4 or flexible materials like polyimide or liquid crystal polymer (LCP), helps reduce the overall thickness and weight of the PCB while maintaining electrical performance.

6. Stacked Vias and Blind/Buried Vias: Stacked vias allow for vertical interconnections between multiple layers, while blind and buried vias provide interconnections between specific layers without going through the entire PCB. These techniques enhance routing capabilities in complex designs.

These are just a few examples of HDI PCB fabrication techniques. The advancement of technology constantly brings new innovations in PCB manufacturing, allowing for even higher-density interconnects and more intricate designs.

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