Why is the cost of high-density multi-layer boards so high? What are the factors influencing the quotation?

In the PCB industry, high multi-layer boards have always been products with high technical content and great manufacturing difficulty. When many customers purchase these boards, they often find that for the same size circuit board, the price of high multi-layer boards is usually much higher than that of ordinary double-sided boards or conventional multi-layer boards. Some boards with 12 layers, 16 layers, or even 20 layers or more are several times or even more than ten times the price of ordinary PCBs.

So, where exactly does the cost of high-density multi-layer boards lie? What factors do manufacturers mainly consider when setting the prices? Understanding these aspects not only helps enterprises reasonably control their procurement budgets, but also enables them to avoid unnecessary cost waste during the product design stage.

What is a high-density multi-layer board?

Generally speaking, when the number of PCB layers exceeds 10, especially for products with 12 layers, 16 layers, or 20 layers and above, they are usually referred to as high multi-layer boards in the industry.

Compared with ordinary 4-layer boards and 6-layer boards, high multi-layer boards have the following characteristics:

More layers

Higher wiring density

More complex structure

The signal rate is faster.

The impedance requirements are more stringent.

Higher reliability standards

Therefore, high-density multi-layer boards are widely used in:

Communication equipment

AI server

Data Center

Industrial Control

Medical equipment

Automotive Electronics

Aerospace and Aviation

These industries themselves have set higher requirements for PCBs.

Why are high-density multi-layer boards so expensive?

Many people think that high-density multi-layer boards are expensive because they contain more materials. However, the material cost is only a part of the total cost.

The key factors that truly influence the price are:

Manufacturing difficulty and yield control.

As the number of layers increases, the production complexity does not grow linearly but rather rises in a stepwise manner.

For example:

If the number of layers is increased from 4 to 8, the cost may increase by about twice.

When upgrading from an 8-layer board to a 16-layer board, the manufacturing difficulty often increases by several times.

What are the main factors influencing the quotations for high-density multi-layer boards?

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1. Number of PCB Layers

The number of layers is the most direct factor influencing the price.

Common products include:

Eight-layer board

10-layer board

12-layer board

Sixteen-layer board

Twenty-layer board

24-layer board

The more layers there are:

More circuit boards and prepreg sheets (PP) will be required.

Meanwhile:

The number of pressing operations has increased.

The difficulty of the position has increased.

Increase in drilling depth

The manufacturing cost has naturally increased.

For example:

The processing difficulty of 16-layer boards is usually much higher than that of 8-layer boards.

Therefore, the price difference is quite obvious.

II. Board Types

The PCB material directly affects the cost.

Common FR-4 material

Suitable for general electronic products.

The price is relatively low.

High TG material

It has better heat resistance.

Suitable for automotive electronics and industrial equipment.

The cost is higher than that of ordinary FR-4.

High-frequency and high-speed materials

For example:

Rogers Series

Megtron series

Panasonic High-Speed Materials

Mainly used for:

5G Communication

AI server

High-speed switch

The price is often several times that of ordinary materials.

Therefore, the choice of materials has a significant impact on the quotation.

III. Plate Thickness and Copper Thickness

Plate thickness

Common plate thickness:

1.0 millimeter

1.6 millimeters

2.0mm

3.2mm

Products with a high number of layers usually have a thicker plate thickness.

The thicker the board:

The greater the degree of pressing and bonding.

Copper thickness

Common specifications:

0.5 ounces

1oz

2oz

3oz

The thicker the copper is:

More electroplating time is needed.

The difficulty of etching will also increase.

Especially:

Automotive electronic and power control products often adopt thick copper designs.

The cost has significantly increased.

IV. Line Precision Requirements

The thinner the wire is, the greater the processing difficulty will be.

Standard PCB:

5mil/5mil

4mil/4mil

The high multi-layer board may require:

3mil/3mil

2.5 mil / 2.5 mil

2mil/2mil

Ultra-thin circuits require:

LDI Laser Imaging

Precision etching

More rigorous AOI inspection

The difficulty of yield control has significantly increased.

Therefore, the price will also increase.

V. Number and Structure of Drilling Holes

The internal connections of the high multi-layer board rely heavily on a large number of holes.

Mainly includes:

Through hole

Throughout the entire board.

Blind hole

Number of layers in the connection part.

Burial hole

Hidden within the board.

Back drilling hole

Used for optimizing high-speed signals.

As the number of holes increases:

Increase in drilling time

The cost of electroplating has increased.

The detection difficulty has increased.

Especially the blind-buried hole structure.

It often requires multiple presses.

The price increase has become more pronounced.

VI. Impedance Control Requirements

High-speed electronic products usually require strict impedance control.

For example:

50Ω single-ended impedance

90Ω differential impedance

100Ω differential impedance

Impedance accuracy requirements:

±10%

±5%

±3%

The higher the precision:

The more strict the production control is.

The manufacturer needs:

Precise calculation of the layered structure

Real-time measurement of impedance value

The manufacturing cost has increased.

VII. Surface Treatment Process

There is a significant price difference among different surface treatment methods.

HASL Tin Plating

The cost is lower.

Suitable for ordinary electronic products.

Silver Inlay (ENIG)

High level of flatness.

It is widely applied to high-end products.

Chemical nickel palladium gold (ENEPIG)

More reliable.

Suitable for automotive and medical electronics.

Electroplated gold

Mainly used for the connector area.

The price is the highest.

The differences in surface treatment will lead to significant variations in the quotations.

VIII. Testing and Certification Requirements

High-density multi-layer boards usually require more rigorous testing.

Including:

Flying needle test

Verify the conduction performance.

AOI inspection

Inspect the wiring defects.

X-ray inspection

Inspect the internal structure.

Metallographic section analysis

Verify the quality of the copper in the hole.

Impedance testing

Ensure the performance of high-speed signals.

If it involves:

Automotive Electronics

Medical equipment

Military industry project

Additional verification may also be required.

The testing cost is also included in the quotation.

IX. Production Yield

This is an important factor that many customers tend to overlook.

During the processing of high-density multi-layer boards:

Possible scenarios include:

Interlayer offset

Cracking of the copper hole

Impedance out of tolerance

Curvature deformation

Line defect

The more layers there are:

The yield is more difficult to control.

For example:

The yield rate of the 8-layer board could reach over 95%.

The yield rate of the 20th layer may significantly decrease.

The manufacturer needs to bear more risks related to product scrapping.

Therefore, the price naturally increased.

X. Order Quantity

The same type of PCB.

The price of the sample is quite different from that of the batch production.

Small batch orders

Feature:

The proportion of engineering costs is high.

High cost of equipment installation

Low material utilization rate

The unit price is relatively high.

Large quantity order

Feature:

Engineering cost amortization

The yield is more stable.

Higher production efficiency

The unit cost has significantly decreased.

Therefore:

The price of 100 pieces is often several times higher than that of 10,000 pieces.

How to reduce the procurement cost of high-density multi-layer boards?

Enterprises can start optimizing from the design stage.

Properly plan the number of floors

Avoid excessive design.

If a problem can be solved with 10 layers, there is no need to design it with 16 layers.

Optimize the wiring structure

Reduce unnecessary layers and pore structures.

Control special processes

For example:

Blindly buried hole

Back drill

Thick copper

Use only at necessary locations.

Conduct DFM review in advance

Reduce risks through manufacturability analysis.

Improve the yield rate of mass production.

Select a manufacturer with rich experience

Excellent manufacturers usually:

Higher yield rate

The process is more mature.

Overall cost is lower.

Avoid subsequent rework and quality losses.