• HDI PCBs have conductive pathways that connect components in a high density package with the use of laser micro vias and high quality thin substrates. Generally, we distinguish HDI boards by the number of lamination cycles and laser drill pairs that are required. For example, 1+N+1, 1+1+N+1+, and 2-(N-1) are all constructions of HDI boards. Our general lamination process for a multi-layer HDI is described below:
• Firstly, we bond layers together via standard lamination process by subjecting two layers and a substrate material to high temperatures and pressure. The circuit traces on each of the layers of copper are etched away using a photosensitive dry resist and fine imaging technologies. If a PCB has multiple subsets within the same design, then we use a sequential lamination process where a dry, electronic substance is placed between each pair of subsets. After this process, standard manufacturing processes can be implemented.
• The most common lamination type for HDI laminates are PTFE and FR4 mix laminates. PTFE has a consistent and controlled dielectric constant, very low substrate imperfections, and a tight tolerance for the overall thickness. For HDI PCBs, PTFE is the most common material selection.
• If you have a specific electrical performance requirement for your application, then we can help you to choose the best lamination and substrate type. If you need any advice about your specific HDI PCB lamination process, then you can contact us via email at info@pcbonline.com.

Often times HDI designs require that vias are stacked on top of one another to transfer signals between layers. There are times when these vias are staggered from one another, but it is also possible that the vias are not staggered at all. We can utilize this stacked via technology to route fine pitch components with very small diameter blind and buried vias. Micro vias typically require the use of a sequential lamination process because of the small drill diameters and via aspect ratio requirements of those drills.

• Choose the correct materials for your specific application is one of the most important processes of designing a high-quality HDI PCB. On top of requiring fine pitch pads, thin traces, and laser drilled micro vias, you will also need to consider the signal integrity of your design for any high-speed signals. If you require complicated thickness structures, large mechanical drills, multiple inner layers with sequential laminations, and micro vias, then you will need to choose the appropriate materials for your design. You can use any of the brands shown below or you can ask our engineers to help you.
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