What is a HDI PCB?
High Density Interconnect PCB, is a circuit board with relatively high line distribution density using micro-blind and buried via technology.
With the development of high-density, high-precision electronic products, the requirements for circuit boards are also the same. The most effective way to increase PCB density is to reduce the number of vias and precisely set blind and buried vias to meet this requirement, resulting in HDI boards.
The electrical interconnection between the board layers of HDI is realized through conductive through holes, buried holes and blind holes. Its structure is different from ordinary multi-layer circuit boards. A large number of micro-buried blind holes are used in HDI boards. HDI uses laser direct drilling, while standard PCBs are usually mechanically drilled, so the number of layers and aspect ratios tend to be reduced.
HDI can not only enable more miniaturization of end product designs, but also meet higher standards of electronic performance and efficiency at the same time.
At present, the core pain point and difficulty of HDI manufacturing is the buried hole plug hole. If the HDI buried hole plugging is not done well, there will be major quality problems, including uneven board edges, uneven dielectric thickness, and potholes on the pads. POE is very professional in this area, we have many years of experience to meet different needs, specially customize HDI PCB of different difficulty for you.
Features of HDI PCB
HDI PCB is a compact circuit board designed for small volume users. Compared with ordinary PCBs, the most notable feature of HDI PCB is the high wiring density. The HDI PCB board is based on the traditional double-sided board as the core board, which is continuously laminated. Compared with the traditional circuit board, the HDI PCB circuit board has the advantages of "light, thin, short and small".
The electrical interconnection between the board layers of HDI PCB is realized through conductive through holes, buried holes and blind holes. Its structure is different from ordinary multilayer PCB circuit boards. A large number of micro-buried blind holes are used in HDI PCB boards.
HDI PCB can not only enable more miniaturization of end product designs, but also meet higher standards of electronic performance and efficiency at the same time. The increased interconnect density of HDI PCB allows for enhanced signal strength and improved reliability.
These features give the HDI PCBs a higher circuitry density as compared to regular PCBs.
Advantages of HDI PCB
1.HDI technology can reduce the cost of PCB, although when the density of PCB increases beyond eight layers, it will be more expensive to manufacture with HDI.
2.The traditional and complex pressing process is low.
3.Increased circuit density: traditional circuit boards and parts are interconnected
4.Conducive to the use of advanced construction technology
5.Have better electrical performance and signal accuracy
6.Better reliability
7.Can improve thermal properties
8.Can improve radio frequency interference/electromagnetic wave interference/electrostatic discharge (RFI/EMI/ESD)
9.Greater design efficiency
The Main Types of HDI PCB Boards
HDI any-layer connect printed circuit boards are the next technological enhancement of HDI microvia PCBs: all the electrical connections between the individual layers consist of laser-drilled microvias. The main advantage of this technology is that all the layers can be freely interconnected.
1. Those with through vias from surface to surface
2. Those with buried vias and through vias
3. Those with two or more HDI layer with through vias
4. Those with passive substrates and no electrical connection
5. Those with coreless construction using layer pairs
6. Those with alternate coreless constructions constructions using layer pairs.
No matter how quickly a product is delivered, it has to perform according to its design specifications. To do this demands the highest level of quality in every aspect of the turnkey PCB assembly process. At POE, one of our core values is ensuring the build quality of each circuit board. To accomplish this, we have several quality control processes throughout our production, including the following:
• Blind and/or buried vias
• Min. Line Width/Space: 0.05/0.05mm
• Via-in-pad
• Through vias from surface to surface
• 20 µm circuit geometries
• 30 µm dielectric layers
• 50 µm laser vias
• 125 µm bump pitch processin
• Surface Finish: ENIG/OSP/HASL/Au Plating (soft/hard)/ Immersion Ag/ Immersion Tin/ Bright Tin Plating/Ag Plating/Carbon Ink
HDI PCB Manufacturing Technology
HDI board is the most sophisticated circuit board in the PCB board, and its board making process is also the most complicated. Its core steps mainly include the formation of high-precision printed circuits, the processing of micro-via holes, and the electroplating of surfaces and holes.
Ultra-fine circuit processing
With the development of science and technology, some high-tech equipment is becoming more and more miniaturized and sophisticated, which requires higher and higher requirements for the HDI boards used. The line width/line spacing of HDI circuit boards of some devices has developed from the early 0.13 mm (5 mil) to 0.075 mm (3 mil), and has become the mainstream standard. The higher and higher line width/line spacing requirements bring the most direct challenge to the graphic imaging in the PCB manufacturing process.
The current formation process of fine lines includes laser imaging (pattern transfer) and pattern etching. Laser direct imaging (LDI) technology is to directly scan the surface of the copper clad laminate with photoresist to obtain the refined circuit pattern. The laser imaging technology greatly simplifies the process and has become the mainstream in HDI PCB plate making. process technology.
Micropore processing
An important feature of HDI circuit boards is that they have micro vias (diameter ≤0.10 mm), which are all buried blind via structures.
Buried blind vias on HDI boards are currently mainly processed by laser.
Compared with laser drilling, mechanical drilling also has its own advantages. When laser processing through holes in epoxy glass cloth dielectric layer, due to the difference in ablation rate between the glass fiber and the surrounding resin, the quality of the hole will be slightly poor, and the residual glass fiber filaments on the hole wall will affect the reliability of the through hole. . Therefore, the advantages of mechanical drilling at this time are reflected. In order to improve the reliability and drilling efficiency of PCB boards, laser drilling and mechanical drilling technologies are steadily improving.
Through metallization
The biggest challenge of through-hole metallization is that it is difficult to achieve uniform plating. For the deep-hole electroplating technology of microvias, in addition to the use of an electroplating solution with high dispersibility, the plating solution on the electroplating device should be upgraded in time. This can be done through strong mechanical stirring or vibration, ultrasonic stirring, and horizontal spraying. In addition, the humidity of the through-hole wall must be increased before plating.
In addition to process improvements, HDIs’ through-hole metallization method has also seen major technological improvements: these include chemical plating additive technology, direct electroplating technology, etc.
HDI PCB Application
Consumer Electronics
Medical Equipment
Automotive Applications
POE has been delivering high-density interconnect printed circuit boards for more than 15 years, and we believe no order is too small, and no tolerance is too tight.Pair that with competitive pricing, quick quotes and response times, domestic and offshore manufacturing and an unprecedented level of flexibility, and you have a winning combination for all your HDI PCB needs.
Shorter PCB manufacturing time-to-market and enhanced machine performance for Flip Chip, BGA, MCM, SIP technologies.
Ultra thin cores, fine line geometries and alternative via methods for improved thermal transfer for thermal PCBs.In compliance with 20um circuit geometries, 30um dielectric layers, 50um laser vias and 125um bump pitch processing.
Allows reducing the lead times by combining the manufacturing capabilities with a profound understanding of high speed digital and high frequency RF package requirements.
Increases the area for PCB designer to place electronical components and also enhances faster signal transmission and reduced signal loss.
Our high HDI PCB boards have the technology-driving capabilities to bring applications in a large number of industries including but not limited to semiconductor test equipment, military weapons, medical, and aerospace.
POE HDI PCB Board Capability
We're capable of manufacturing HDI PCB up to 24 layers in various structures, check the following table for our available HDI PCB structures:
ITEM Capability
Layers 1-28
Thicker Copper 1-6OZ
Products Type HF(High-Frequency)&(Radio Frequency) board, Impedance controlled board , HDI board ,BGA& Fine Pitch board
Solder Mask Nanya&Taiyo ;LPI & Matt Red, green, yellow,white, blue,black.
Base material FR4(Shengyi China、ITEQ, KB A+,HZ), HI-TG, FR06, Rogers,Taconic、Argon、Nalco、Isola and so on
Finished Surface Conventional HASL,Lead-free HASL,Falsh Gold, ENIG (Immersion Gold)OSP(Entek), Immersion Tin,ImmersionSilver,Hard Gold
Selective Surface 
ENIG(immersion Gold)+OSP, ENIG(immersion Gold)+Gold Finger,Flash Gold +Gold Finger, immersion Silver+ Gold Finger, Immersion Tin+Gold Finger   
Technical Specification Minimum line width/gap:3.5/4mil(laser drill)
Minimum hole size:0.15mm(mechanical drill)/4mil(laser drill)
Minimum Annular Ring: 4mil
Max Copper thickness: 6OZ
Max Production size:900×1200mm
Board Thickness:D/S: 0.2-7.0mm, Multilayers:0.40-7.0mm,
Min Solder Mask Bridge:0.08mm
Aspect ratio: 15:1
Plugging Visa capability: 0.2-0.8mm
Tolerance Plated holes Tolerance:0.08mm(min±0.05)
Non-plated hole tolerance:0.05min(min+0/-0.05mm or +0.05/-0mm)
Outline Tolerance:0.15min(min±0.10mm)
Functional test :
Insulating resistance : 50 ohms (mormality)
Peel off strength: 1.4N/mm
Thermal Stress test :2650c,20 seconds
Solder mask hardness:6H
E-Test voltage :500V+15/-0V 30S
Warp and Twist: 0.7% (semiconductor test board≤0.3% )