Blind Vias
Vias are an important component of a PCB. They provide paths for connecting different layers and help with signal transmission integrity. However, blind and buried vias can add up in price due to the extra work required to fabricate them. In this blog post, we’ll look at how they affect the manufacturability of a PCB, and what steps are needed to make sure they are manufactured correctly.
A blind via is a hole that connects two or more inner layers of the PCB. It is drilled into one layer of the PCB and then filled with a conductive material (either electroless or electroplating) through which electrical connections can be made. This is a more expensive method of making a connection compared to plated through holes because of the additional steps that are involved.
The advantage of using a blind vias is that it doesn’t affect the layout of the other layers on the board, which can allow designers to create more complex circuits. This can also reduce the number of drill holes that are required and make it easier to meet tight design tolerances. Another benefit is that it helps to lower parasitic capacitance, which is a significant issue with today’s high data rates. The parasitic capacitance is caused by the barrel of the plated through-hole and the planes it passes through, which can degrade signals beyond where they are useful. A blind via eliminates this problem by shortening the length of the hole and reducing its diameter, which significantly reduces the amount of capacitance that is created.
Blind Vias – How They Affect the Manufacturability of PCBs
There are several different types of vias that can be incorporated into a PCB, including blind and buried vias. The type that you choose will depend on your needs and the capabilities of your manufacturer. The best way to decide which type of via to use is to check with your manufacturer to see if they support the types you are considering and what their process requirements are for producing a PCB that uses these features.
A common type of blind via is the controlled-depth via. This type is drilled into a layer of the PCB, and then it is filled with copper through either electroless or electroplating. This is the most cost-effective way to manufacture a blind via, but it has some limitations. For example, the hole must be deep enough to reach the copper in the layer below it, but not so deep that it hits other components on the PCB.
The other type of blind via is the photo-defined blind via. This type is drilled after the PCB is laminated, but before the outer layers undergo etching and lamination. The manufacturer prepares the core by laminating a sheet of pre-preg and a sheet of copper foil to it. The photosensitive layer has a pattern that indicates where the blind vias should be, and then it is exposed to light to harden. When the layers are etched, the holes are defined. Then the copper is deposited in the holes and on the surface of the core.