Best Manufacturers for High-Density Interconnect PCB in 2025

In the world of modern electronics, High-Density Interconnect (HDI) PCBs have become the backbone of cutting-edge devices, enabling greater functionality in increasingly compact form factors. This blog explores the essential requirements for HDI PCBs and profiles leading manufacturers capable of meeting these sophisticated demands across different production scales.

Requirements for HDI PCBs

Of course. The core concept of high-density interconnect (HDI) boards is to "achieve more functional connections in a smaller space," which dictates fundamental differences in design and manufacturing compared to standard PCBs. Its requirements are comprehensive, interlocking, and can be summarized as the ultimate pursuit of  "precision," "complexity," and  "reliability."

First, its routing design demands extremely high precision, necessitating the use of very fine trace widths/spacings and minute vias. Trace widths/spacings are typically reduced to the mil level, and the key to achieving interconnection lies in the extensive use of microvias, blind vias, and buried vias. Particularly, laser-drilled microvias have a much smaller diameter. These vias are no longer simply drilled through the entire board but are intricately placed between specific layers, like floors in a building, thereby avoiding the occupation of valuable routing space and achieving a leap from two-dimensional to three-dimensional layout.

Second, this precise layout presents severe challenges for layer stack-up structure and materials science. To achieve reliable interconnection between multiple layers of microvias, the board's stack-up becomes exceptionally complex, often requiring sequential lamination processes, meaning the board is laminated in multiple stages. This places stringent demands on the alignment accuracy between the core boards and prepreg. Simultaneously, traditional FR-4 material may struggle to meet high-frequency, high-speed, or thermal endurance needs. Therefore, it is necessary to select specialty materials such as modified epoxy, polyimide, or low-loss, low-Dk materials to ensure signal integrity and long-term operational stability.

Finally, all of this must be built upon top-tier process control and quality standards. From the precision of laser drilling and the smoothness of the via walls, to the ability to perform void-free copper plating and filling of vias, and the absolute accuracy of layer-to-layer registration, even a minor deviation in any manufacturing step can lead to the failure of the entire board. Consequently, manufacturers must possess近乎苛刻的 (near-demanding) process control and a comprehensive quality inspection system to ensure that every HDI board not only meets electrical performance standards but also possesses long-term reliability under harsh operating conditions. In summary, it is the ultimate test of a manufacturer's comprehensive technical strength, spanning from design support to final inspection.

Mass-production Manufacturers

These manufacturers possess massive production capacity, highly automated production lines, and global supply chain support, ensuring long-term, stable, and cost-effective large-scale delivery. They are typically core suppliers to the world's top electronics brands.

TTM Technologies, Inc. ranks among the world's leading high-tech printed circuit board manufacturers, boasting industry-leading technical expertise in HDI. This manufacturer excels particularly in handling designs with extremely high layer counts and dense routing, while possessing deep expertise in substrate-like boards and advanced packaging technologies. It serves as the preferred supplier for numerous premium smartphone, data center server, and networking equipment brands.

Unimicron Technology, a Taiwan-based global PCB industry giant, ranks among the world's top tier in both scale and technical capabilities. With comprehensive product lines and substantial production capacity in HDI and IC substrates, Unimicron provides stable high-volume manufacturing support to customers across consumer electronics, computing, and automotive electronics. Its robust engineering capabilities and consistent quality represent core competitive strengths.

AT&S is an Austria-based premium PCB manufacturer renowned for its sophisticated craftsmanship and exceptional reliability. It possesses unique strengths in high-end HDI, semiconductor packaging substrates, and integrated component technologies. AT&S focuses specifically on demanding industries, with its products widely used in automotive electronics (particularly ADAS systems), medical devices, and industrial automation. It stands as a representative enterprise in Europe's high-end technology market.

Shennan Circuit is the undisputed leader in mainland China's PCB industry, boasting unmatched technological prowess and scale domestically. The company holds unparalleled strengths in communication backplanes, core network equipment boards, and server motherboards. Its mature and reliable HDI technology earns trust from leading global communication equipment manufacturers while actively expanding into aerospace and high-end medical electronics markets.

WUS Printed Circuit is a renowned PCB manufacturer with years of deep-rooted experience in mainland China, celebrated for its formidable capabilities in communication boards and automotive electronics boards. The company maintains robust HDI manufacturing processes and a stable quality control system. It enjoys an excellent reputation and significant market share in supplying PCBs for enterprise-level network equipment and automotive control systems, serving as a long-term strategic partner for many global top-tier clients.

Small-to-medium Batch Manufacturers

These manufacturers specialize in flexibility, responsiveness, and technical services. They are well-suited for prototype validation during R&D phases, pilot production runs, and niche market projects that do not require massive production capacity. They offer customers closer technical support and shorter delivery cycles.

Gold Circuit Electronics is a highly regarded manufacturer in the field of quick-turn and small-batch HDI production. It offers clients fast, flexible services spanning prototyping to small-to-medium volume manufacturing, with technical capabilities sufficient to meet most high-density design requirements. Known for its efficient responsiveness and reliable product quality, this manufacturer is an ideal choice for many R&D teams and tech startups.

Edadoc Tech, while renowned for its robust PCB design consulting and technical services, also excels in HDI quick-turn production through its affiliated manufacturing system. Its key advantage lies in providing end-to-end solutions from design optimization to manufacturing. Its engineering team delivers professional design-for-manufacturing analysis, which is crucial for mitigating R&D risks and accelerating time-to-market.

Xunjiexing Tech positions itself explicitly as a “specialist in PCB express services and small-batch prototyping.” Centered on a strategy of “diverse product range, high quality, and fast delivery,” HDI board production is a core focus. Xunjiexing deeply understands client needs during the R&D phase, offering efficient online quoting and seamless communication—making it highly suitable for electronic product development projects requiring rapid iteration.

PCBONLINE is a manufacturer specializing in high-value-added PCB and assembly services, excelling in small-batch production and mid-to-high-end industries. Equipped with premium production equipment from Germany and Japan, it possesses the capability to manufacture HDI boards ranging from 1-layer to over 20-layer, along with DFM and R&D capabilities. The company specializes in production for industries such as BMS, CCS, IoT, and industrial control. A key feature of this manufacturer is its vertically integrated service offering, spanning high-quality PCB fabrication to component sourcing (with a dedicated Hong Kong procurement office) and assembly. This makes it particularly well-suited for clients seeking a one-stop solution with stringent requirements for materials and production standards. The company possesses extensive application experience in high-end sectors including industrial control, medical, and aerospace.

The landscape of HDI PCB manufacturing is diverse, catering to different needs across the product lifecycle. From global giants ensuring mass production stability to agile specialists enabling rapid innovation, the choice of manufacturer ultimately depends on your specific technical requirements, volume needs, and strategic goals. Understanding these options empowers designers and engineers to select the right partner for bringing their most advanced electronic visions to life.

Core Capabilities Summary for HDI Manufacturers

One-Stop HDI PCB Manufacturer and Its PCB Via Filing Capabilities

If you're looking for turnkey HDI electronics manufacturing services (EMS) from hardware development to PCBA fabrication and box-build assembly, you can work with the one-stop HDI PCBA manufacturer PCBONLINE.

Founded in 1999, PCBONLINE has R&D capabilities for HDI projects and EMS manufacturing capabilities, including via filling for stacked vias. It provides 4-to-64-layer HDI PCB fabrication, assembly, and PCBA box-build assembly. You can order various HDI PCBs from PCBONLINE, such as FR4, polyimide (flexible PCB), polyimide + FR4 (rigid-flex PCB), and PTFE/Rogers (high-frequency PCB).

Here'e the PCB via filing capabilities at PCBONLINEL:

• Micriavia filling with copper: laser via size 0.1-0.125mm, priority 0.1mm
• Finished hole size for via-in-pad filling with resin: 0.1-0.9mm (drill size 0.15-1.0mm), 0.3-0.55mm normal (drill size 0.4-0.65mm)
• Max aspect ratio for via-in-pad filling with resin PCB - 12: 1
• Min resin plugged PCB thickness: 0.2mm
• Max via-filling ith resin PCB thickness: 3.2mm
• Making different hole sizes with via filling in one board: Yes
• Via filling with copper/silver: Yes

If you need HDI PCBAs or any other PCBAs requiring via filling, please send your email to PCBONLINE at info@pcbonline.com. We will provide one-on-one engineering support to you.

Conclusion

Via filling is used for creating stacked vias in HDI PCB fabrication, BGA/CSP/QFN IC packaging, and filling PCB via-in-pad with resin during multilayer PCB fabrication. If you need one-stop electronics manufacturing for your HDI PCBA project, contact the one-stop advanced PCB manufacturer PCBONLINE for high-quality PCBA and box-build solutions tailored to your project's needs.