HDI PCB (high-density interconnect board) HDI PCB (high-density interconnect board) is a highly integrated and compact PCB, own features of high line distribution density through the technology method of micro-blind and buried.Like other popular PCBs, the HDI board also has inner and outer layers. Through drilling, in-hole metallization, and other methods to build the internal connection of each layer of lines. HDI PCBs are generally manufactured by the lamination method. The more the number of laminations, the higher the grade of the PCB. Common HDI PCBs only need one-time stack-up, but high-end HDI needs two or more stack-up while using advanced methods like electroplating, direct laser drilling, and stacking.
When a designer has 8 layers or above request on PCBs, PCB’s cost will be competitive using HDI technology compared with the traditional lamination method. HDI PCBs are compatible with more advanced technology in the electronics industry, like advanced assembly test technology and high-end precision technology that request good electrical performance and precision signals. Electronic products are constantly developing towards high density and high precision. The so-called “high” not only improves the machine’s performance but also reduces the size of the machine. High-Density Integration (HDI) technology contributes to the miniaturization of product designs while offering high performance on electronic efficiency, heating management and reliability:
Save PCB cost
Increasing line density
Good electrical performance
Better reliability
Enhance thermal properties
Improves EMI/ESD/RFI
Increase design efficiency
HDI PCBs are widely used. HDI PCBs reduce the weight and overall size of products and enhance the electrical performance of equipment. HDI boards are generally manufactured by the build-up method. The technical grade of the plate is higher. Ordinary HDI boards are layered once, and high-end HDI uses two or more layering techniques. High-value consumer electronic products such as digital (camera) cameras, MP3, MP4, notebook computers, automotive electronics, and other digital products, among which smartphones are in greatest demand.
The medical industry is where HDI PCB has made the most progress. Medical equipment usually requires a small form factor with high signal transmission speed. In addition to being compatible with the structure of human organs or tissues, it integrates communication, power, power, and mechanical properties as much as possible. It realizes it with the smallest possible volume. It is necessary to ensure low power consumption and stable, high-speed signal transmission. And that’s where only HDI PCB can help.
In addition, HDI PCBs are also used in automotive electronics and aviation equipment that require lightweight and small sizes.
Layers: 8(1+6+1) L Thickness: 1.0mm
Out Layer Copper Thickness: 1 OZ
Inner Layer Copper Thickness: 1 OZ
Min Hole Size: 0.2mm Min Line Width: 2mil
Surface Finish: ENIG
Application: Automotive
Layers: 6L Thickness: 1.2mm
Out Layer Copper Thickness: H OZ
Inner Layer Copper Thickness: H OZ
Min Hole Size: 0.1mm Min Line Width/: 3mil
Surface Finish: ENIG
Application: Display
Layers: 8(2+4+2) L Thickness: 1.0mm
Out Layer Copper Thickness: 0.5 OZ
Inner Layer Copper Thickness: 1 OZ
Min Hole Size: 0.2mm Min Line Width: 3mil
Surface Finish: ENIG
Application: Network
Its core steps mainly include the formation of high-precision printed circuits, the manufacturing of micro-via holes, and the electroplating of surfaces and holes.
Ultrafine Circuits
A few high-tech equipment are high integration and miniaturized. The line width/line spacing of HDI circuit boards of some devices has decreased from the early 0.13 mm (5 mil) to 0.075 mm (3 mil) and has become the existing mainstream standard. The high line width/line spacing requirements enhance the most direct challenge of graphic imaging in the PCB manufacturing process. The existing formation process of lines includes laser imaging (pattern transfer) and pattern etching. Laser Direct Imaging (LDI) technology directly scans the surface of the copper-clad laminate with a photoresist to obtain a refined circuit pattern. Laser imaging technology greatly simplifies the manufacturing process and has become a mainstream engineering process in HDI PCB processing.
An important feature of the HDI circuit board is its micro vias (diameter≦ 0.10 mm), which are all buried blind vias. The buried blind holes on the HDI board are mainly processed by laser, rest is CNC drilling. Compared with laser drilling, CNC drilling also has its own advantages. When laser drilling through holes in epoxy glass cloth dielectric layer, under the condition of the difference in ablation rate between the glass fiber and the surrounding resin, the quality of the hole will not be ferfect, and the residual glass fiber filaments on the hole wall will affect the reliability of the through hole process. Therefore, the advantages of mechanical drilling at this time are presented. Laser drilling and mechanical drilling technologies are steadily improving the reliability and drilling efficiency of PCB boards.
It is crucial to improve the plating uniformity and deep hole plating ability in PCB processing and the board’s reliability. High-frequency sound waves can accelerate the etching ability; permanganic acid solution can enhance the decontamination ability of workpieces, and high-frequency sound waves will stir a certain proportion of potassium permanganate plating solution in the electroplating tank, which will help the plating solution flow into the hole evenly. Thus, the deposition ability of electroplated copper and the uniformity of electroplating are improved. Currently, the copper plating and filling of blind holes is also mature, and copper filling of through holes with different diameters can be carried out. The two-step copper plating and hole-filling method are suitable for through holes with different diameters and high aspect ratios. It has a strong copper-filling ability and can minimize the thickness of the surface copper layer. There are many options for the final finish of the PCB; electroless nickel/gold (ENIG) and electroless nickel/palladium/gold (ENEPIG) are commonly used on high-end PCBs.
Feature | Capability |
Quality Grade | Standard IPC 2, IPC 3 |
Number of Layers | 4 – 30layers |
Material | FR4 standard Tg 140°C,FR4 High Tg 170°C, FR4 and Rogers combined lamination, special materials |
Max Board Size | Max 450mm x 600mm |
Final Board Thickness | 0.4mm – 6.0mm |
Copper Thickness | 0.5oz – 13oz |
Min Tracing/Spacing | 2mil/2mil |
Min Hole Diameter – Mechanical | 4mil |
Min Hole Diameter – Laser | 3mil |
Solder Mask Color | Green,Matte Green, Yellow, White, Blue, Purple,Black, Matte Black, Red |
Silkscreen Color | White, Black, Yellow, Blue |
Surface Treatment | Immersion gold, OSP, Hard gold, Immersion Silver |
Impedance control | ±10% |
Lead Time | 2 – 28days |