Blind hole PCB

A blind via is a via that connects the outer layer and inner layer of a PCB without penetrating the entire board. It is often used in PCBs with more than four layers and can increase component density by 15%-20%.

A buried via is a via that connects two or more inner layers of a PCB without connecting to the outer layers, helping to reduce the number of layers and improve signal integrity.

Blind vias connect one inner layer and one outer layer, partially penetrating the board; buried vias connect multiple inner layers, fully penetrating the connected layers, and cannot be visually inspected.

It can improve component density, provide flexible wiring, reduce costs, improve signal integrity, and reduce parasitic capacitance.

Commonly used in products with high space and performance requirements such as mobile phones, tablets, medical devices, and high-end computers.

The minimum for laser drilling is 0.1mm, and the minimum for traditional drilling is 0.15mm.

The diameter of buried vias is generally suitable to be 0.3mm - 0.5mm.

For traditional drilling, the depth-to-width ratio is <12:1; for laser drilling, it is >0.75:1.

Similar to blind vias, the depth-to-width ratio of buried vias by traditional drilling generally also needs to be controlled below <12:1.

Yes, because their manufacturing processes are complex, requiring more processes, more precise equipment, and strict testing, which increases costs.

It emerged to meet the requirements of miniaturization and high integration of electronic products and improve the circuit density of PCBs.

They connect one inner layer and one outer layer.

They connect two or more inner layers and do not connect to the outer layers.

Because they do not penetrate the entire board's stack-up structure, they occupy less space than ordinary plated-through holes, allowing components to be placed more densely.

By skipping the outer layers, designers can use fewer lamination layers when routing on the inner layers.

Compared with traditional through holes, blind vias have a shorter path, which can improve signal integrity to a certain extent, but it is slightly weaker than buried vias.

Because they do not connect to the outer layers, the parasitic capacitance generated is small, which is conducive to improving high-frequency performance.

Not as well as buried vias. Buried vias can prevent interference signals from the outer layers from coupling to the inner layer traces, while blind vias connect to the outer layers, so the shielding effect is limited.

Blind Via; Buried Via.

They have a high proportion in the high-end and high-density PCB fields, and with the miniaturization of electronic products, the proportion is on the rise.

Factors such as aperture size, hole depth, depth-to-width ratio, interlayer alignment, signal integrity, heat dissipation, and cost need to be considered.

The minimum annular ring width for buried vias and blind vias is 0.15mm, and for laser blind vias, it is 0.10mm.

It is determined according to the position of the target inner layer and the board thickness, and precise control is required to ensure stopping at the correct layer.

Pay attention to precise alignment between layers, avoid conflicts with other vias or traces, and reasonably plan positions to optimize signal transmission.

Yes, but cross-design will increase manufacturing difficulty and cost, and should be avoided as much as possible.

It can make the stack-up structure more flexible, reduce the number of layers, and optimize signal transmission, but increase manufacturing complexity.

Reasonably plan the number, size, and type of vias, avoid over-design, and select appropriate manufacturing processes.

Used for pin connection in BGA packaging, which can reduce signal residue and improve routing density.

Try to shorten the length of buried vias, reduce the number of vias, ensure short and straight signal transmission, and reduce signal loss.

Heat can be directed to the heat dissipation area through methods such as thermal pad connection to avoid heat concentration around the vias.

Direct connection or connection through teardrop-shaped pads to ensure safe and reliable connection.

Reliable connection, good electrical conductivity, and avoidance of poor contact and open circuit problems.

The distance from the via to the trace and pad is >=0.25mm, and the diameter of the isolation pad is >= drill diameter + 0.6mm.

Reduce the size of vias, reasonably layout, shorten the signal path, and buried vias not connecting to the outer layers can reduce parasitic capacitance.

Improper handling will have an impact. For example, too large, too many, or unevenly distributed vias may reduce mechanical strength.

Reasonably plan the positions of vias and traces, follow the principles of signal integrity, and adopt shielding measures when necessary.

Follow the principles of shortest routing, optimal signal, conflict avoidance, and easy manufacturing.

Reasonably layout vias and traces, reduce the area of current loops, and adopt measures such as shielding layers.

An appropriate number of vias can improve performance, while too many may increase signal interference, reduce mechanical strength, and increase costs.

Reasonably arrange the positions of vias according to the positions of component pins and the signal flow direction to facilitate connection.

The main methods are mechanical drilling and laser drilling. Mechanical drilling is suitable for larger apertures, and laser drilling has high precision and is suitable for small apertures.

Usually, before laminating multi-layer boards, buried vias between inner layers are manufactured through processes such as drilling and copper plating.

The precision is relatively lower than laser drilling. The aperture is generally larger than 0.15mm, and the depth-to-width ratio is <12:1.

High precision, can make a minimum aperture of 0.1mm, depth-to-width ratio >0.75:1, and little damage to the board.

Adopt high-precision positioning systems and strictly control processes such as drilling and laminating.

Precisely controlling the depth, avoiding drilling deviation, and ensuring the quality of the via wall and copper plating effect.

Problems such as interlayer alignment deviation, poor copper plating in the via, and rough via walls.

Generally, a combination of electroless copper plating and electroplating is used to ensure good electrical conductivity of the via wall.

The general requirement is that the copper plating thickness is not less than 18μm, subject to product requirements.

A clean, constant temperature and humidity environment is required to reduce the impact of dust and changes in temperature and humidity on the process.

High-precision drilling equipment, copper plating equipment, laminating equipment, etc. are required, and laser drilling has higher requirements for equipment grades.

Factors such as aperture size, quantity, precision requirements, manufacturing process, and equipment cost.

Control drilling accuracy, hole wall quality, copper plating quality, interlayer alignment accuracy, etc.

Visual inspection, aperture measurement, hole position measurement, copper plating thickness detection, electrical performance testing, etc.

Classify and recycle, recover and refine metal waste, and dispose of other waste in accordance with environmental protection requirements.

Laser drilling has relatively high energy consumption, and the energy consumption of the entire manufacturing process varies depending on the process and equipment.

Improve accuracy, reduce costs, shorten production cycles, and increase yield.

Operators need protection to prevent laser damage and chemical corrosion, and equipment should be regularly maintained and inspected.

Such as high-precision laser drilling technology, new copper plating processes, etc.

There are relevant industry standards, and enterprises also have internal standards to ensure process consistency and quality stability.

Through visual inspection, aperture measurement, hole depth measurement, copper plating thickness detection, electrical continuity testing, etc.

Due to non-visual inspection, interlayer alignment is mainly detected by X-ray, conductivity is detected by electrical performance testing, and copper plating thickness is measured, etc.

Rough hole walls, aperture deviation, insufficient hole depth, poor copper plating, foreign matter in the hole, etc.

Interlayer alignment deviation, copper plating voids, open circuits, residual glue in the hole, etc.

Depending on the type of defect, it can be re-drilled, re-plated with copper, or foreign matter removed. Severe defects may require scrapping.

It is difficult to repair problems such as interlayer alignment deviation. For copper plating voids, re-plating copper can be tried, and scrapping is required in severe cases.

Under normal use and maintenance, it is equivalent to the life of the PCB, and it can normally work within the life cycle of general electronic products.

Problems such as copper plating layer corrosion, open circuits, and abnormal signal transmission may occur.

Take protection measures, avoid harsh environments such as humidity and high temperature, and conduct regular inspections and maintenance.

It depends on the product usage environment and requirements. Generally, electronic products are fully inspected during production and periodically sampled during use.

Microscopes, aperture measuring instruments, X-ray inspection equipment, electrical performance testing equipment, etc.

Based on industry standards and product design requirements, such as aperture tolerance, copper plating thickness standards, etc.

Keep clean, avoid external impact, and regularly check the appearance and electrical performance.

Humid environments may cause corrosion of the copper plating layer, affecting conductivity and signal transmission. Moisture-proof measures are required.

High temperature may cause material expansion and deformation, affecting the accuracy of the holes and the reliability of connections. Heat dissipation and material high-temperature resistance need to be considered.

Reasonable design can resist electromagnetic interference to a certain extent, otherwise problems such as signal distortion may occur.

Compare with standard values, analyze the causes of deviations, determine whether they are within acceptable ranges, and provide a basis for process improvement.

Meeting the inspection standards is qualified, and exceeding the tolerance range or having defects affecting performance is unqualified.

Maintenance time, maintenance personnel, maintenance content, inspection data, problems found and handling situations, etc.

Due to the need for professional equipment and technology, the inspection cost is relatively high, specifically depending on the inspection items and quantity.

Used for signal transmission lines to increase wiring density and meet the needs of high-speed and high-frequency signal transmission.

Used in automotive control units, sensors, etc., to improve integration, reduce volume, and enhance reliability.

Used in aircraft electronic equipment to meet the requirements of miniaturization, high performance, and high reliability.

It can achieve miniaturized design, improve component integration, and adapt to the strict requirements of wearable devices for space and performance.

Improve equipment accuracy and reliability to meet the needs of medical equipment for miniaturization and high performance.

Used in industrial controllers, instruments, etc., to enhance system stability and integration.

Developing towards higher density, smaller size, and faster signal transmission.

For example, medical equipment requires high reliability, and 5G communication equipment requires high-speed signal transmission performance, etc.

Check whether the copper plating layer is detached, whether there is foreign matter in the hole, and whether the connection with the trace is good. Use electrical testing equipment for positioning.

Check interlayer alignment deviation, copper plating defects, and surrounding interference sources, and analyze through signal testing.

Slight corrosion can be replated after cleaning, and severe cases require replacing the PCB or related components.

Check for short circuits and optimize the heat dissipation design, such as adding heat sinks and improving ventilation.

Reasonable design and fixing can ensure certain reliability, otherwise problems such as loose connections may occur.

Salt spray easily corrodes the copper plating layer, and protection measures such as corrosion-resistant materials or coatings are required.

In high-altitude environments, the thin air and heat dissipation changes may affect performance, requiring targeted design.

The higher the humidity, the more likely the copper plating layer is to corrode, affecting conductivity and signal transmission.

High temperature may cause material expansion and deformation, and low temperature may make the material brittle, affecting connection reliability.

It may damage the copper plating layer, causing open circuits or affecting signal transmission. Electrostatic protection is required.

Reasonable layout, shielding measures, optimized trace design, etc.

Yes, performance may decline due to copper plating layer wear, corrosion, etc., requiring regular inspection and maintenance.