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High Density Interconnect

The term high density interconnect refers to printed circuit boards that feature dense placement of components and denser interconnections. Compared to standard PCBs, HDI PCBs can have up to six times the number of copper layers, significantly improving signal integrity and overall performance. This technology is primarily used in electronic devices like mobile phones, tablets and high-performance computers, which require compact circuitry.

High-density interconnect PCBs are constructed using multiple sequential lamination processes. The first step in the fabrication process is etching the inner copper layers to form a blank PCB. This is followed by applying a prepreg layer on both sides of the board and stacking the layers together, like a book. These laminates are then pressed and heated, which liquifies them and sticks them to each other. This process is repeated for each layer of the high density interconnect  PCB until it reaches the desired thickness and routing density. The more layers a PCB has, the higher its routing density will be.

A key ingredient in high-density interconnect is vias, which are small conductive holes that join layers of the board. Vias provide pathways for signals to travel across the PCB, ensuring smooth operation. These traces typically run parallel to the edge of the board, which helps reduce cross-talk and increase signal speed. There are different types of vias, including blind and buried, which are used in HDI PCBs.

Can High Density Interconnect Be Folded Or Creased?

Despite the benefits of increased component density, high-density interconnects pose certain challenges for the manufacturing industry. The most significant challenge is the difficulty of achieving consistent, precise dimensions for each layer. A minor deviation from the specified dimension can impact the reliability of a circuit board. To ensure the accuracy of a high-density PCB, it is critical to use advanced photolithography machinery and precision etching processes.

High-density interconnect technology is an essential part of the modern electronics industry. It offers advantages that are not possible with conventional PCB designs, including lower component pitch, smaller board size, and improved signal integrity. Increasing the amount of copper on the surface of the PCB also improves thermal security, preventing thermal stress and overheating.

As the technology continues to evolve, manufacturers are able to produce more complex circuitry in smaller form factors. This enables new, portable devices that address the needs of today’s consumers. However, the increased complexity of HDI PCBs requires multidisciplinary teams of electrical and mechanical engineers to design and manufacture them effectively.

Fortunately, advancements in materials and manufacturing processes have enabled HDI PCBs to become more reliable. PCB material suppliers are developing FR4 materials that can be fabricated at high-density, providing designers with the freedom to explore innovative designs without having to compromise on reliability.

These materials can be fabricated with a variety of surface finishes, including ENIG, immersion tin, and immersion silver. They are also compatible with microvia drilling and sequential lamination processes, allowing them to support the unique requirements of high-density PCBs. In addition, they can be etched with reactive ion and immersion ion techniques to produce accurate traces.

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