PCB Blind And Buried Hole Diameter Requirements

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When there is limited room on a printed circuit board, connections between layers are made via buried and blind vias. However, not every combination is feasible. UL states that the maximum number of heat press cycles is three. Therefore, we are unable to build multi-layer PCB boards that need more than three lamination procedures in order to provide optimal dependability and quality. This means that you are not allowed to design vias so that assembling them would require more than three steps.

HDI+ buried hole process, buried hole diameter requirements: as shown in the figure below, the buried hole diameter of DRL2-3 is ≤0.30mm, because the RCC between L1 and L2 is very thin.

Except 2.1, mechanically controlled depth drilling, all mechanical blind and buried holes have a diameter of ≤0.40mm

Deep-controlled blind hole process

Furthermore, buried and blind vias significantly raise the price of a circuit board. They ought to be employed just when required. We provide micro vias down to 0.1mm (4 mil) and via holes down to 0.2mm (0.2 mm) to assist PCB designers of tightly printed boards. The minimum pad diameters required for these outer layers are 0.45mm and 0.4mm, respectively.

Verify that your manufacturer covers the vias with copper plate or plugs made of metal or thermal/electrical epoxy to prevent internal air bubbles from migrating upward and creating pinholes or voids in the solder junction. It's not always possible to accommodate every link on one layer. Here's where vias can save the day! A blind via, which doesn't pass through the whole board, joins the outer layers to the inner layers. Without getting to the outer layers, a buried route links the inner levels. Every layer is connected via a throughhole that extends from top to bottom.