WHAT IS BLIND AND BURIED VIA IN PCB?

PCBsupplierChina learned these are connective, plated-through holes between PCBs’ layers. They are used to route a trace between outer and internal layers. It is especially vital for multi-layered boards with complex designs where the provision of sufficient flow of both electrical and thermal current is an issue. 

Vias are drilled mechanically and then plated to create an electrical connection. You can see them as simply channels that may vary in diameters/sizes and types. For example, in the image below, there is a conventional, non-optimal PTH via, a buried via, and a blind via.

It is apparent that the first type goes through the entire PCB connecting all the layers at once. But let’s focus more on the other two types as they are way more functional and complicated to use.

· Blind via. Ensures a connection of the surface layer with several next ones. It is called blind because it makes it impossible to see through the PCB.

· Buried via. Ensures a connection between several inner layers. It is called buried because it is not visible on a PCB’s surface.

PCBmanufacturer China talk：HOW MUCH DO BLIND VIAS COST?

Fabrication method.

As detailed, sequential lamination is the most expensive technique overall.    At the same time, photo defined fabrication offers a superior price per via.    Controlled depth fabrication is simply the most affordable method.

Aspect ratio.

Typically, manufacturers charge more for aspect ratios that are rather than 10.    It is so because such design decisions may require non-conventional approaches to fabrication.    But what is even more important is the pad clearance which is extremely hard to keep at higher aspect ratios.

For example, an aspect ratio of 12 on a 4 mm board means the needed via size is 0.3 mm, pad size of 0.56 mm, and a drill hole size of 0.36 mm.    In this case, via pad-tp-BGA pad clearance is only 0.09 mm., which is difficult to ensure.

A number of vias.

It is a very basic consideration that impacts some methods and the amount of time needed to fabricate all of them.

Via size.

A machine with higher revolutions per minute is needed to get a high-quality hole.    Not necessarily, but it may affect the cost per via.    And the differences in via sizes will absolutely result in higher cost.    It is so because either several machine units will be required, or the same equipment unit will be subject to changing its tooling multiple times.

Typically, you will not be charged for standard designs in board shops, i.e., for designs that can be performed with standard drill set-ups. But it is because the average via cost is already in the final price.    But large suppliers offering custom PCBs at affordable costs do charge depending on the factors detailed above.

So much for this post. Feel free to let FPC&PCBmanufacturer know if you’re interested in knowing more about it, or that you have any question about FPC.