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What Do You Know About HDI

by: Sep 21,2018 1915 Views 0 Comments Posted in PCB Basic Information


Summary:       HDI board refers to High Density Interconnect, namely High Density Interconnect board. It is a relatively new technology developed by PCB industry in the end of 20th century.

What Do You Know About HDI

—by PCBWay

Basic Information:

HDI board refers to High Density Interconnect, namely High Density Interconnect board. It is a relatively new technology developed by PCB industry in the end of 20th century. When the drilling hole size of the traditional PCB reaches 0.15mm, the cost is very high and it is difficult to improve it again because of the affection by the drilling tool. The drilling of HDI board no longer relies on traditional mechanical drilling, but uses the laser drilling technology so that it's sometimes called a laser plate. The hole diameter of HDI board is generally 3-5mil (0.076mm-0.127mm) and the width of circuits is generally 3-4mil (0. 076mm-0.10mm). The size of the pad can be greatly reduced, so more circuits can be distributed within the unit area, resulting in higher density. The emergence of HDI technology adapts and advances the development of PCB industry, making it possible to arrange the more concentrated BGA, QFP and so on in the HDI board. At present, HDI technology has been widely used, among which the level 1 HDI has been widely used in the PCB production of BGA with 0.8 pitch.


PCBWay Materials:

1.     Classification of Materials:

1)     Copper: the basic material of PCB board.

2)     Core: the skeleton of the circuit board and double-sided copper-clad board, which can be used for double-panel production of the inner layer.

3)     Prepreg: multi-layer board makes indispensable materials, adhesives between the core board and the core board, and also ACTS as insulation.

4)     Resistance welding ink: it can prevent welding, insulation and corrosion on the board.

5)     Character ink: marking.

6)     Surface treatment materials: including lead-tin alloy, nickel-gold alloy, silver, OSP, etc.

2.     Materials of Insulation layers:

Classification of Materials



60T12,   65T12, 80T12, 60T18, 80T18


1080,   106

3.     Introduction of Special Materials:

1)     RCC (Resin Coated Copper) is a special material used for HDI insulation, which refers to the coating of a special resin coating on Copper plating. This film can completely cover the inner line to form an insulation layer.


2)         Features of RCC:

a)      free of glass dielectric layer, easy to form by laser and plasma microhole.

b)     thin dielectric layer.

c)      extremely high peel strength.

d)     high toughness and easy to operate.

e)     smooth surface, suitable for micro-narrow line etching.

Generally, laser drilling of HDI plates is done on the Coated Copper foil and the shape of the aperture is not exactly the same as that of a mechanical bore. The hole in the laser drill is shaped like an inverted trapezoid, while the shape of the general mechanical drill hole is column. Considering the energy and efficiency of laser drilling, the size of laser holes should not be too large and it generally is 0.076-0.10mm.

Other materials, such as semi-cured sheet and copper foil, donot have special requirements. Since the current in the laser plate is generally not too large, the thickness of copper in the circuit is generally not too thick. For example, the inner layer is typically 1 ounce and the outer layer is typically half an ounce of base copper plated to 1 ounce of finished copper thickness. The thickness of the sheet is generally thinner. Moreover, since RCC only contains resin and does not contain glass fiber, the hardness/strength of HD1 board using RCC is generally worse than other PCB with the same thickness.


PCBWay Capacities:

The Regular Capacities of HDI Boards:





Layers Number

4-18   layers

Through hole aspect ratio




Blind hole aspect ratio




Clearance tolerance

+/-   3mil



Blind   hole location tolerance

+/-   20um

Min-diameter of Through Hole


Minimum Spacing of out   layer


Min-diameter of Blind Vias


Minimum Spacing of inner   layer


Min-thickness of out-layer copper foil


Number   of laser drilling


Max-thickness of out-layer copper foil


The   machined bore diameter of the blind hole


Min-thickness of inner-layer copper foil


Impedance   tolerance

+/-   7%

Min-thickness of inner-layer copper foil


Solder   mask alignment

5mil   bigger than pad of inner layer


If you have any need of HDI PCB, pls do not hestitate to contact PCBWay! All that you just need to click here: https://www.pcbway.com

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