What are Stacked and Staggered Microvias PCB

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Microvias are tiny holes in printed circuit boards (PCBs) that connect pad layers. There are two major types: stacked microvias and staggered microvias.

Stacked vs. staggered microvias on a PCB refer to the physical location of the via on the board: stacked refers to the vias located in two rows with one via row stacked on top of another via row, while staggered means all vias are offset within a single row. At first glance, these two methods seem to have little difference between them, but as you will find out here in this guide, there are some essential differences that may end up changing your PCB layout design selection for a particular project or application.

Stacked Microvia

A stacked microvia PCB is a printed circuit board with multiple layers of metal interconnections. The vias are often called "stacked microvias" or "stacked vias." Stacked microvia saves space and improves heat dissipation by transferring heat from the top layer to another side of the board. This allows for more surface area on the top layer and better cooling features on the bottom layer. The primary function of these vias is to improve the thermal and electrical performance of a printed circuit board. They also provide more possible routing options and reduce parasitic inductance.

Stacked Microvia PCB Layout

The stacked microvia PCB can be manufactured using standard PCB processes such as etching, drilling, plating, and soldering. The layers are assembled using automatic pick-and-place machines that place each component in its correct location on the PCB to create a fully functional device.

The stacked microvia has a cylindrical shape and is made of copper, while the hole in the top layer is made using laser drilling or electrochemical etching (ECE). The diameter of the drilled hole should be equal to that of the diameter of the stacked via. After drilling holes in the top layer of copper, thin copper foil (1-5 microns) is deposited on the top and bottom surface. Then solder paste is done to fill gaps between vias in the bottom layer with solder paste, after which another layer of copper foil is deposited over it. Finally, solder bumps are formed by the reflow soldering process.

Stacked Microvia Advantages

  • Stacked microvias PCB is a PCB made with holes smaller than a drill bit's diameter. This allows you to place vias in a stack on top of each other without using an extra layer. This design method is excellent for saving board space and cost, but it can be tricky to fabricate.
  • Stacked microvias make your PCB look more professional and allow you to fit more components onto your board. They are instrumental when there is not enough room for large holes in your design. Stacking vias is also helpful when trying to route traces through dense areas or using small trace widths.
  • Stacked microvias allow you to place vias in layers without using an extra layer on your board. These holes are drilled into the board at different depths, so they look like little pyramids from above. They work well when you need more than one via but do not have room for larger holes or if you want more than two layers of capacitance between two sections of traces on a multilayer board.
  • Another advantage of stacked microvias PCB is that it can be used to make the circuit board more compact and flexible, which helps reduce the device's size and improve its performance.

Stacked Microvia Applications

Stacked microvias are used for high-density interconnects and provide better routing options for signal traces on multiple-layer boards. Stacked microvias PCB can be used in various applications such as:

Stackable Connectors

Stackable connectors are used for connecting network elements and other devices. These connectors are designed to stack one on top of the other. The stacked microvia PCBs have many vertical holes through which you can pass cables or wires. Therefore, if you have a lot of cables or wires that need to be connected, this is the ideal solution for you.

Power Distribution Boards

Power distribution boards distribute power from one point to multiple points in any device. The stacked microvia PCBs are designed to allow conductive paths to be formed between different points on the board without any interruptions in conductivity between them. This provides power to be distributed evenly across every part of the board without any loss or damage to the current flow.

Staggered Microvia

Staggered microvias PCB is a design that allows for more efficient heat transfer and improved performance. The staggered microvia design places the vias at an angle to the board rather than in a straight line. This means that there will be more contact between the chip and the board, giving you better thermal dissipation and lower temperatures. The purpose of using these types of interconnects is to provide an easier way to route signals between different layers of the PCB, allowing for more efficient routing and better signal integrity. 

Staggered microvias are used in high-frequency designs where it is necessary to minimize parasitic inductance between adjacent signal traces. They can also be helpful in power distribution networks because they can reduce inductance and thus improve efficiency.

Staggered Microvia PCB Layout

The staggered microvia PCB layout comprises multiple layers containing at least one via (hole) between each hole on each layer. These vias are used as connections between layers to form a conductive path. The holes are spaced out evenly, so they do not overlap with other holes or components on the same layer.

The staggered microvias are made by drilling tiny holes in the PCB, called via holes. These holes are then filled with solder or plated with copper to make electrical connections between different copper areas on a circuit board.

Staggered Microvia Advantages

  • When using multiple layers on a board, there is always a risk of crosstalk between adjacent layers as they run parallel to each other in close proximity. By routing traces along staggered vias instead, this risk is significantly reduced because they are not running parallel to each other as regular vias would.
  • Because there is less crosstalk between traces on staggered via boards, this also reduces EMI emissions from the board itself.
  • Another advantage of this approach is that it reduces the overall cost of your board by reducing the number of vias required and making routine easier since there are fewer connections between different layers.
  • It provides improved thermal dissipation due to its more open structure than traditional multilayer boards. This means that heat does not get trapped under layers as easily as conventional multilayer boards, making them more efficient in removing heat from components such as CPUs and GPUs.

Staggered Microvia Common Applications

Medical Devices

 In medical devices like hearing aids and other medical devices where high-frequency signals are transmitted through wires, staggered microvias PCB is used to ensure good signal integrity by reducing impedance at these frequencies.

Wireless Communication Circuits

These circuits also require good signal integrity and can be made using staggered microvias PCB. The advantage of using staggered microvias PCB here is that it reduces the length of the traces and thus improves the performance of these circuits.

Summing Up

We hope this guide has shed some light on the stacked and staggered microvias PCB technology and applications. Microvias are an essential part of PCB design and fabrication and stacked, and staggered microvias are no different. They are designed to improve signal quality by reducing impedance at high frequencies, especially in today's modern devices, such as smartphones, tablets, and medical devices. Ultimately, which is best will depend on the needs of your project. To learn more about HDI microvias, we recommend you check out Hemeixin.

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