The buried and blind via technology for high-layer PCB manufacturing, and stable mass production is the core key.

2026,04,25

In the manufacturing of high-layer and multi-layer PCBs, the key lies in the stable mass production of buried and blind via technology. It serves as the core principle of high-end PCB manufacturing, as well as the dividing line between "paper-only technology" and genuine technical strength.

On one hand, consumer electronics pursue light weight, thin profile and high-density interconnection, representing the continuous exploration of ultimate miniaturization. On the other hand, products for AI computing power and servers focus on high frequency, high speed, signal transmission, high-layer stacking and buried & blind via technology, which mark the extreme challenges for data transmission capabilities in the computing era.

The R&D of high-end products can never be achieved through empty promotion. The decisive factor for enterprises’ competitiveness is how to convert these cutting-edge technologies into tangible products and realize stable mass production.

Why is stable mass production so difficult?

Professionals in the industry are generally familiar with the basic process flow of blind and buried via technology. It is not hard to produce a few prototypes; the real challenge is maintaining consistent stability throughout high-volume production.

1.Drilling accuracy and depth control

Blind vias only connect the outer layers with specific inner layers, while buried vias are completely hidden between inner layers. Laser drilling requires extremely precise depth control. Excessive drilling depth will damage the target layer, whereas insufficient depth will result in failed interlayer connection. The hole diameter is usually ≤ 0.15mm, and the hole position deviation must be controlled within ±0.02mm. Any deviation beyond the tolerance will cause misalignment between vias and circuits, sharply increasing the risk of open circuits.

2.Uniformity of electroplated through holes and blind holes

Through holes feature a high aspect ratio, which restricts the circulation of electrolyte inside the holes and easily causes uneven plating thickness. For AI server applications, the electroplated copper thickness on the inner walls of buried and blind vias shall be no less than 25μm, with surface copper thickness deviation controlled within ±3μm. Insufficient copper thickness will directly reduce current carrying capacity.

3.Control of layer alignment in multi-layer lamination

High-end HDI boards often require multiple lamination cycles for completion. Each lamination process carries the risk of interlayer offset. If the interlayer alignment error exceeds ±25μm, the stability of signal transmission will be compromised.

Second-order HDI boards generally need three times of lamination. With each additional lamination step, the production yield typically drops by approximately 5% to 10%.

4.Differentiated challenges brought by high-frequency and high-speed materials

The layer count of HDI boards for AI servers has evolved from the conventional 20 layers to 40 layers, and even 60 to 78 layers. The number of buried and blind vias can exceed 5,000 per square meter. High-frequency and high-speed materials are required, such as M9-grade ultra-low loss materials (Dk＜3.0), to support high-frequency and high-speed signal transmission. From consumer electronics to AI computing power hardware, the technical difficulty has achieved leaping upgrades.

Only stable mass production capability is the absolute truth.

1.Three Core Indicators of Mass Production Capability

Yield stability: The mass production yield shall remain steadily above 98% with a fluctuation range of less than 1%. Otherwise, it will lead to out-of-control costs.

Delivery consistency: Deviations in hole position accuracy, copper thickness uniformity and electrical performance of products from different batches must be controlled within ±5%.

Cost controllability: On the premise of ensuring quality, control the unit cost within the customer’s acceptable range to avoid losing market share due to excessive costs. Maintaining a mass production gross profit margin above 30% represents sound cost control.

2.How to Improve Mass Production Capability

Process standardization: Solidify the parameters of each process into standardized operating procedures (SOP) to reduce discrepancies caused by manual operation.

Equipment automation: Adopt fully automatic laser drilling machines, electroplating lines and AOI inspection equipment to improve production efficiency and product consistency.

Professional talent team: Cultivate interdisciplinary talents with comprehensive capabilities in design, process and quality control to quickly handle unexpected on-site production issues.

Supply chain collaboration: Establish in-depth cooperation with material and equipment suppliers to secure high-quality raw materials and equipment in advance, ensuring stable supply.

The R&D of high-end products relies not on empty boasting, but on steadily refining every process detail step by step, ultimately transforming cutting-edge technologies into stable mass production that is repeatable, scalable and profitable.

With unwavering commitment to stable mass production and superior quality, our company is a trusted leader in PCB manufacturing. We specialize in a full range of high-performance products, including FPC Flexible Board Series & Soft-Hard Combination Board Series, OSP Antioxidant Board, Nickel Gold Plate Series, Spray Tin Plate Series, FR-4 Multilayer circuit board, and FR-4, CEM-3 Double-sided Circuit Board. Backed by mature buried and blind via technology—core to high-layer and multi-layer PCB manufacturing—we translate cutting-edge technical strength into consistent, reliable products. Our strict quality control and standardized production processes ensure each product meets the highest industry standards, delivering stable performance and long-term value for customers across various fields.

Author:

Mr. lingchao

E-mail:

mr.xu@lingchaopcb.com

Phone/WhatsApp:

+86 13780181891