• 86-0411-8853-2005
  • marketing@gespcb.com



what is the HDI PCB? HDI board is an abbreviation for high density interconnect board. Because of the rapid advancement of high technology. Many electronic products are becoming thinner and shorter in length. and high density interconnect board (HDI) to meet market demands. As a result, the development of the HDI board is very rapid. Because of the impact of the drilling tool, traditional PCB board drilling. The cost has been very high when the hole diameter is 0.15mm, and it is difficult to improve again. Laser drilling replaces mechanical HDI board drilling. 

The drilling hole diameter of HDI board is typically 3-5mil (0.076-0.127mm). The average line width is 3-4mil (0.076-0.10mm). To optimize line distribution per unit area, reduce pad size. This results in high-density interconnection. HDI uses infrared and ultraviolet laser hole technology. CO, infrared laser hole forming technology well known for its efficiency and stability. That widely used in the manufacture of 4-6MIL blind holes. HDI technology has seen widespread adoption.

What is the HDI PCB?

The HDI board utilities micro-blind buried hole technology. a circuit board with a relatively dense line distribution. An inner layer of lines and an outer layer of lines are prevalent on an HDI board. Drilling, hole metalization, and other processes are then used. so that each layer of lines has an internal connection. The greater the number of layers, the higher the board’s technical grade. Ordinary HDI board only laminated once. HDI at the highest level using two or more lamination. PCB technology includes stacked holes, plating filling holes, laser direct punching, and more.

The Origin of HDI Boards

In April 1994, the United States printed circuit board industry formed the ITRI. collaborative society to study circuit board manufacturing technology. HDI was born in this society. 5 months later, in September 1994, ITRI began production of high-density circuit board research. which became known as the October Project. After about three years of research, ITRI made public the results of its research on July 15, 1997. with the publication of the October project phase1 round2 report evaluating microwaves. officially launching the “High Density Interconnect HDI” era. Since then, HDI has advanced rapidly, and in 2001. it became the standard for cell phone boards, IC packaging, and loading boards.

HDI PCB Prototype

For high-speed signal electrical requirements. Impedance control with AC characteristics . high-frequency transmission capability, as well as radiation reduction (EMI). Stripline, Microstrip structure, and multilayer design are now required. Low dielectric coefficient to reduce signal transmission quality. The insulation material has a low attenuation rate. To meet the demand for miniaturization of electronic components and arrays. circuit boards continue to increase in density. Attachment and other group parts assembly method. and propel the printed circuit board to a previously unheard-of high-density realm.

HDI Board Identification

This micro via geometry technology improves circuit assembly, space utilization, and more. while the need for miniaturization of electronic products. The industry has used a variety of different names to describe this type of circuit board structure. For example, in Europe and the United States. because the manufacturing process employs sequential construction. this type of product known as SBU (Sequence Build Up Process). which translates as “sequential layer method”. 

Because the hole structure created by these products is much smaller than the previous holes. the production technology of these products known as MVP (Micro Via Process). which is generally translated as “Microvia Process” in the Japanese industry. Some people refer to this type of circuit board as BUM (Build Up Multi layer Board). which is generally translated as “Multi layer board.” because the traditional multi layer board called MLB (Multi layer Board). To avoid confusion, the IPC board association in the United States of America proposed calling this type of product HDI .

Materials for HDI Boards


There are several new requirements for HDI PCB materials. including better dimensional stability, anti-static mobility and non-adhesives. typical materials for HDI PCBs are RCC (resin-coated copper). there are three types of RCC, namely polyimide metalized films. pure polyimide films, and cast polyimide films.

The advantages of RCC include: small thickness, light weight, flexibility and flammability. compatibility characteristics impedance and excellent dimensional stability. In the process of HDI multilayer PCB. instead of the traditional bonding sheet and copper foil as an insulating medium and conductive layer. RCC suppressed by conventional suppression techniques with chips. non-mechanical drilling methods such as laser are then used to form micro-through-hole interconnections.

RCC drives the occurrence and development of PCB products from SMT to CSP . and from mechanical drilling to laser drilling. promoting the development and advancement of PCB microvia. all which become RCC leading HDI PCB materials.

In the actual PCB in the manufacturing process. for the choice of RCC, there are usually FR-4 standard Tg 140C. FR-4 high Tg 170C and FR-4 and Rogers combination laminate. which are mostly used nowadays. With the development of HDI technology. HDI PCB materials must meet more requirements that.

Trends in HDI PCB Materials


  1. The development and application of flexible materials using no adhesives;
  2. Small dielectric layer thickness and small deviation;
  3. The development of LPIC;
  4. Smaller and smaller dielectric constants;
  5. Smaller and smaller dielectric losses;
  6. High solder stability;
  7. Strictly compatible with CTE (coefficient of thermal expansion);


HDI Board Process


HDI boards are mainly made by using the technology of micro-blind buried holes. which features a higher density of electronic circuit distribution in printed circuit boards. The main solution for HDI high-density interconnection is to match the hole forming solution.

  • First-order process: 1+N+1
  • Second-order process: 2+N+2
  • Third-order process: 3+N+3
  • Fourth-order process: 4+N+4

Advantages of HDI.


That can reduce PCB costs: When the density of the PCB exceeds the eight-layer board. HDI will manufacture it at a lower cost than the traditional complex press-fit process.

  • Increase line density: traditional circuit board and part interconnection
  • Facilitate the use of advanced assembly technologies
  • Better electrical performance and signal correctness
  • Better reliability
  • Improved thermal properties
  • Improved RFI/EMI/ESD
  • Increases design efficiency

The Distinction Between Conventional PCB and HDI PCB


HDI mechanically drills through-holes, blind, and buried holes, unlike PCBs. However, laser drilling for micro-vias is also available. HDI PCBs have a variety of stacking arrangements to accommodate microvia. reducing the number of vias and inner layers. Micro vias in HDI inner layers improve signal integrity and routing space.

HDI outperforms standard PCBs board size and electrical performance. HDI manufacturing threshold and process difficulty are much higher than standard PCBs. There are more issues to consider during production, particularly buried hole plugging.

The buried hole plugging is the main source of pain and difficulty in HDI manufacturing. GESP will explain HDI board manufacturing in the next article.

Applications of HDI Boards

While electronic designs are constantly improving machine performance. they are also attempting to reduce machine size. From cell phones to smart weapons, “small” is a constant in small portable products. HDI is widely used in cell phones, digital cameras, automotive electronics. and other digital products, the most common of which are cell phones. The higher the board’s technical grade. Ordinary HDI boards are basically 1 time laminate. whereas high-grade HDI boards use 2 or more times the laminate technology. as well as stacked holes, plating filling holes, laser direct punching. and other advanced PCB technology. 5G phones, advanced cameras, and other applications use high-order HDI boards.

Why Choose GESP HDI PCB Fabrication Services?

GESP summed up the experience try to reduce HDI costs for our clients. we believe that the hole copper thickness is one of the important factors affecting the reliability and life of the PCB. if too thin, the conductive hole after high temperature or high current applications. there is a possibility to pulled off, resulting in board failure. we focus on PCB manufacturing 17 years. and GESP HDI has its own complete system, the entire process is not outsourced. all quality acceptance standards as IPC2 level standards. such as hole copper thickness ≧ 20μm. GESP with the most advanced hole-filling line. as well as the most advanced VCP horizontal plating line, resin plug hole line. Ensure that all PCBs qualities. Contact Us Now!

Leave a Reply

Your email address will not be published. Required fields are marked *