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What is via in PCB?
2024-07-25 21:51:41
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:
The Role of Blind Vias in PCB Design and Manufacturing
Blind vias
Blind vias are small holes that connect one layer of the PCB to another without passing through the entire board. This allows designers to create complex and densely packed PCBs more efficiently and reliably than with conventional methods. By using blind vias, designers can build multiple levels on a single board, reducing component costs and speeding up production times. However, the depth of a blind via typically should not exceed a specific ratio relative to its aperture. Therefore, precise control of the drilling depth (Z-axis) is crucial. Inadequate control can lead to difficulties during the electroplating process.
Another method for creating blind vias involves drilling the necessary holes in each individual circuit layer before laminating them together. For example, if you need a blind via from L1 to L4, you can first drill the holes in L1 and L2, and in L3 and L4, then laminate all four layers together. This method requires highly accurate positioning and alignment equipment. Both techniques highlight the importance of precision in the manufacturing process to ensure the functionality and reliability of the PCB.
Buried vias
What are buried vias?
What is the difference between micro via and buried via?
Buried vias are critical components in PCB design, connecting inner layer circuits without extending to the outer layers, rendering them invisible from the outside. These vias are essential for internal signal interconnections. Experts in the PCB industry often note, "Buried vias reduce the likelihood of signal interference, maintain the continuity of the transmission line's characteristic impedance, and save wiring space." This makes them ideal for high-density and high-speed PCBs.
Since buried vias cannot be drilled post-lamination, the drilling must be performed on individual circuit layers before lamination. This process is more time-consuming compared to through-holes and blind vias, leading to higher costs. Despite this, buried vias are predominantly used in high-density PCBs to maximize the usable space for other circuit layers, thereby enhancing the overall performance and reliability of the PCB.
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 using a plasma cleaning method.
*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 primary use for via is an electrical connection. The size is smaller than other holes that use for solder components. The holes used for solder components will be bigger. In PCB production technology, drilling is a fundamental process, and one can not be careless about it. The circuit board can’t provide electrical connection and fixed device functions without drilling the required through holes in the copper-clad plate. If an improper drilling operation causes any problem in the process of through holes, it may affect the use of the product, or the whole board will be scrapped, so the drilling process is critical.
The drilling methods of vias
There are mainly two drilling methods of vias: mechanical drilling and laser drilling.
Mechanical drilling through holes is a crucial process in the PCB industry. Through holes, or through holes, are cylindrical openings that pass entirely through the board and connect one side to the other. They are used for mounting components and connecting electrical circuits between layers. Mechanical drilling of through holes involves using specialized tools such as drills, reamers, and countersinks to create these openings with precision and accuracy. This process can be done manually or by automated machines depending on the complexity of the design and production requirements. The quality of mechanical drilling directly impacts product performance and reliability, so this step must be done correctly every time. By maintaining high standards through mechanical drilling, through holes can be made reliably and accurately to ensure efficient electrical connections.
Laser drilling
Mechanical drilling through holes is a crucial process in the PCB industry. Through holes, or through holes, are cylindrical openings that pass entirely through the board and connect one side to the other. They are used for mounting components and connecting electrical circuits between layers. Mechanical drilling of through holes involves using specialized tools such as drills, reamers, and countersinks to create these openings with precision and accuracy. This process can be done manually or by automated machines depending on the complexity of the design and production requirements. The quality of mechanical drilling directly impacts product performance and reliability, so this step must be done correctly every time. By maintaining high standards through mechanical drilling, through holes can be made reliably and accurately to ensure efficient electrical connections.
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.
lacement 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
Through-hole diameter
The diameter of through holes must exceed the diameter of the plug-in component pin and keep some margin. The minimum diameter that the wiring can reach through holes is limited by drilling and electroplating technology. The smaller through hole diameter, the smaller space in PCB, the smaller the parasitic capacitance, and the better the high-frequency performance, but the cost will be higher.
Through-hole pad
The pad realizes the electrical connection between the electroplating inner layer of the through-hole and the wiring on the printed circuit board’s surface (or inside).
Capacitance of through hole
ach through hole has parasitic capacitance to the ground. The through-hole parasitic capacitance will slow down or deteriorate the rising edge of the digital signal, which is unfavourable for high-frequency signal transmission. It is the main adverse effect of through-hole parasitic capacitance. However, in ordinary circumstances, the impact of through-hole parasitic capacitance is minuteness and can be negligible—the smaller diameter of the through hole, the smaller the parasitic capacitance.
Inductance of through hole
Through holes are commonly used in PCBs to connect electrical components, but they can also have an unexpected side effect: inductance.
Inductance is a property of through holes that occur when electric current flows through them and induces a magnetic field. This magnetic field can cause interference with other through-hole connections, resulting in signal loss or distortion. If we want to mitigate these effects, it’s crucial to understand how inductance works and what design steps you can take to reduce its impact on your PCBs.
The diameter of through holes must exceed the diameter of the plug-in component pin and keep some margin. The minimum diameter that the wiring can reach through holes is limited by drilling and electroplating technology. The smaller through hole diameter, the smaller space in PCB, the smaller the parasitic capacitance, and the better the high-frequency performance, but the cost will be higher.
Why PCB vias must be plugged?
Here are some reasons why PCB vias must be plugged, summarized by Shenzhen Rich Full Joy Electronics Co., Ltd :
Shenzhen Rich Full Joy Electronics Co., Ltd：
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.
Shenzhen Rui Zhi Xin Feng Electronics Co., Ltd. offers comprehensive PCB manufacturing, component sourcing, PCB assembly, and electronic manufacturing services. With over 20 years of experience, we have consistently delivered high-quality PCBA solutions at competitive prices to over 6,000 global customers. Our company is certified with various industry certifications and UL approvals. All our products undergo 100% E-testing, AOI, and X-RAY inspections to meet the highest industry standards. We are committed to providing exceptional quality and reliability in every PCB assembly project.
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Drilling Process Introduction:
1. Pinning, Drilling, and Hole Reading
Objective: To drill through-holes on the PCB surface to establish electrical connections between different layers.
By using upper pins for drilling and lower pins for hole reading, this process ensures the creation of vias that facilitate interlayer circuit connections on the printed circuit board (PCB).
CNC Drilling:
Objective: To drill through-holes on the PCB surface to establish electrical connections between different layers.
Key Materials:
Drill Bits: Composed of tungsten carbide, cobalt, and organic adhesives.
Cover Plate: Primarily aluminum, used for drill bit positioning, heat dissipation, reducing burrs, and preventing pressure foot damage during the process.
Backing Plate: Mainly a composite board, used to protect the drilling machine table, prevent exit burrs, reduce drill bit temperature, and clean resin residue from drill bit flutes.
By leveraging high-precision CNC drilling, this process ensures accurate and reliable interlayer connections on printed circuit boards (PCBs).
Hole Inspection:
Objective: To ensure there are no abnormalities such as over-drilling, under-drilling, blocked holes, oversized holes, or undersized holes after the drilling process.
By conducting thorough hole inspections, we guarantee the quality and consistency of each via, ensuring the electrical performance and reliability of the printed circuit board (PCB).