What is via in PCB?
Vias are the most common holes in PCB production. They connect the different layers of the same network but are usually not used for solder components. Vias can be divided into three types: through holes, blind vias, and buried vias. The details information for these three vias is as below:
Blind vias
Blind vias are small holes that connect one layer of the PCB to another without passing through the entire board. Blind vias enable designers to create complex and densely packed PCBs more efficiently and reliably than conventional methods. With blind vias, designers can create multiple levels on a single board, reducing component costs and making for faster production times. Also, the depth of the blind via usually not over a specific ratio (aperture). This production method must pay special attention to the drilling depth control (Z axis). It should be appropriated. If you ignore it, it won’t be easy to electroplate in the hole in the plating process. The other way to make blind via, you can also drill the holes for the circuit layer that needs to be connected first at the time of making individual circuit layers, then stick each layer together ( for example, blind via from L1-l4, you can drill L1 and L2, L3 and L4 first, then attach all four-layer). Still, this method needs an exact positioning and alignment device.
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Buried vias
Buried vias connect the inner layer circuit in PCB. They can connect any inner layer but not through to the outer layer, so you can not see it from the outer layer like buried inside the PCB. And they are also used in inner signal interconnection. People familiar with the PCB industry may share their views, “Buried vias can reduce the probability of signal interference, keep the continuity of the characteristic impedance of the transmission line, and save the wiring space at the same time, right?” Yes, indeed. That’s why they are suitable for high-density and high-speed PCB. Buried via can not be drilled after lamination. We have to drill at individual circuit layers. It will take more time than through holes, and blind vias, so buried via costs are the highest. Buried via typically use in high-density PCB to increase the usable space of other circuit layers.
Through holes
Through holes are used to connect all layers through the top layer and bottom layer. Plating copper inside holes can be used in internal interconnection or as a component positioning hole. The purpose of through holes is to allow for the passage of electrical wiring or other components through a surface. Through holes provide a means to mount and secure electrical connections on printed circuit boards, wires or similar substrates that require an attachment point. They are also used as anchors and fasteners in industrial products such as furniture, shelving, and medical equipment. Additionally, through holes can provide pass-through access for threaded rods in machinery or structural elements. Furthermore, the process of plugging through holes is required. Viasion summarizes the following requirements for plugging through holes.
- Clean the through holes with a cotton swab or toothpick.
- Ensure the through hole is free of debris, dirt and dust.
- Measure the through holes to ensure it is compatible with the plugging device
- Choose an appropriate filler material for filling through holes: silicone caulk, epoxy putty, expanding foam or polyurethane glue.
- Insert and press the plugging device in the through hole.
- Securely hold it in position for at least 10 minutes before releasing pressure.
- Wipe away any excess filler material from around the through holes once complete.
- Check through holes periodically to ensure they are free of leaks or damage.
- Repeat the process as necessary for through holes of varying sizes.
The drilling methods of vias
There are mainly two drilling methods of vias: mechanical drilling and laser drilling.
Precautions for PCB via design
- Ensure vias are not too close to components or other vias.
- Vias are an essential part of a PCB design and must be placed carefully to ensure they do not cause any interference with other components or vias. When vias are too close, there is the risk of short-circuiting, which can severely damage the PCB and all connected components. According to Viasion’s experience, to minimize this risk, vias should be placed at least 0.1 inches away from components, and vias should not be placed closer than 0.05 inches to each other.
- Ensure vias do not overlap with traces or pads on neighbouring layers.
- When designing vias for a circuit board, it is essential to ensure vias do not overlap with any traces or pads on other layers. It is because vias can cause electrical shorts, leading to system malfunctions and failure. As our engineers suggest, vias should be placed strategically in areas with no adjacent traces or pads to avoid this risk. In addition, it will ensure the vias do not interfere with other elements on the PCB.
- Take into account current and temperature ratings when designing vias.
- Ensure vias have good copper plating for current carrying capability.
- Placement of vias should be considered carefully, avoiding locations where routing may be difficult or impossible.
- Understand the design requirements before selecting via sizes and types.
- Always place vias at least 0.3mm from board edges unless otherwise specified.
- If vias are placed too close to one another, it may damage the board when it is drilled or routed.
- It is essential to consider the aspect ratio of vias during design, as vias with a high aspect ratio can affect signal integrity and heat dissipation.
- Make sure vias have sufficient clearances to other vias, components and board edges as per design rules.
- When vias are placed in pairs or more significant numbers, it is important to spread them evenly for optimal performance.
- Be mindful of vias that may be too close to a component’s body, as this can cause interference with the signals passing through.
- Considering vias near planes. They should be placed carefully to minimize signal and power noise.
- Consider placing vias in the same layer as signals where possible, as this reduces vias costs and improves performance.
- Minimize vias count to reduce design complexity and costs.
Mechanical characteristics of PCB through hole
Why PCB vias must be plugged?
Here are some reasons why PCB vias must be plugged, summarized by Viaison:
- PCB vias provide a physical link to mount components and connect different PCB layers, thus enabling the board to perform its intended function efficiently.
- PCB vias are also used to improve the PCB’s thermal performance and reduce signal loss. As PCB vias conduct electricity from one PCB layer to another, they must be plugged to ensure a connection between the different layers of the PCB.
- Lastly, PCB vias help prevent short circuits by avoiding contact with any other exposed components on the PCB.
Therefore, PCB vias must be plugged to prevent any electrical malfunctions or damage to the PCB.
Summary
In a nutshell, PCB vias are essential parts of PCBs, allowing them to route signals effectively between layers and connect different board elements. By understanding their various types and purposes, you can ensure that your PCB design is optimized for performance and reliability.
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