Let’s continue to learn about the various types of holes found on HDI PCB.
1. Two-step hole
Laser holes that span from the second layer to the third layer are known as second-order vias. It's similar to descending a staircase, where you go down one step from the first to the second layer, and then another step from the second to the third layer, hence the term "second-order via." These vias are used to connect signals or components between the second and third layers of a multi-layer PCB.
2. Any-layer hole
Arbitrary-order vias refer to laser holes that can connect any two layers within a PCB. These are not through-holes and include all types of first-order, second-order, third-order, buried vias, and more. For example, a laser hole from layer 4 to layer 2 is considered an arbitrary-order via. The top cover image is a drilling type chart of a 12-layer arbitrary-order board, showing that there are more than 60 types of blind and buried holes.
Top-tier smartphone manufacturers developing 5G phones typically use arbitrary-order via designs to ensure optimal phone performance. On the other hand, Original Design Manufacturers (ODMs) often opt for cost-reducing second- or third-order via designs to significantly reduce subsequent production costs. The arbitrary-order via process represents the highest level of PCB design and manufacturing technology .
More kinds of holes will be shown in the next new.
