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4-layer HDI with 1 stacking PCB manufactrue process
4-layer HDI with 1 stacking PCB manufactrue process

4-layer HDI with 1 stacking PCB manufactrue process

2019-07-04 14:48:16
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Author:pcb factoty

High-density interconnect PCB (HDI PCB Board) is now gradually being widely used. Traditional HDI PCB is used in two types of products, portable products and semiconductor packaging.

The third type of application of HDI PCB's rapid growth: high-speed industrial system applications. The difference between this type of printed circuit board used in telecommunications and computer systems is: PCB board size is large, the focus is on electrical performance, and the challenge of wiring Very complex PBGA and CCGA packages.


For designers, the first thing to notice is to design high-speed PCB systems regardless of the best intentions of the design. They need to understand how to use materials in the system to meet the performance indicators of physical devices. PCB material selection, layered structure and design rules will affect electrical performance (such as PCB characteristic impedance, crosstalk, and signal conditioning). The device density will also show the function of PCB wiring rules, design specifications, material selection and microvia structure selection. Buried and blind vias are simple structures for complex, multi-layered PCBs. Compared with material stability, board surface treatment and design rules, problems in the assembly process will be confirmed in circuit testing.


4-layer HDI with 1 stacking PCB manufactrue process


Three typical application platforms of HDI PCB

The classification of HDI PCB products is determined by the recent development of HDI and the strong demand for its products. Mobile communication companies and their PCB suppliers have played a pioneering role in this field and have established many standards. Correspondingly, the demand for products has also prompted changes in the technical limitations of mass production, and the prices have become more affordable. The consumer industry has taken the lead in HDI PCB products. The computer and network circles have not yet felt the strong pressure of HDI PCB technology approaching, but due to the increase in component density, they will soon face such pressure and enable HDI PCB technology. In view of the ever-shrinking pitch and the ever-increasing number of I/Os, the advantages of using HDI PCB substrates on flip-chip packages are very obvious.

HDI PCB technology can be divided into several technology types. The main driving force of HDI PCB products is from mobile communication products, high-end computer products and PCB substrates for packaging. The technical requirements of these types of products are completely different. Therefore, HDI PCB technology is not one type, but several types. The specific classifications are as follows:

      *HDI PCB board for miniaturization

      *HDI PCB board for high density substrate and subdivision function

      *High-level number HDI PCB board


1. Miniaturized HDI PCB board

HDI PCB miniaturization initially refers to the reduction of the size and weight of the finished product, which is achieved through its own wiring density design and the use of new high-density devices such as uBGAs. In most cases, even if the price of a product remains stable or declining, its functionality continues to increase. The internal interconnection adopts the buried via process structure, which is mainly a 6-layer or 8-layer board. Other features of the product include the following: 10mil pads, 3-5mil vias, most of them use 4mil line width/line spacing, the board thickness is also controlled within 40mil, FR4 or high Tg. (160 ℃) FR4 substrate. Figure 1 describes the basic structure and main design rules of HDI.

The miniaturization technology of consumer products is relatively mature in HDI PCB technology and is widely used in China. This design method provides a good application of smaller size and higher density, and the application device includes uBGA or flip chip pins.


2. High-density substrate HDI PCB board

HDI PCB boards with high-density substrates are mainly concentrated in 4-layer or 6-layer boards, with buried vias between layers to achieve interconnection, of which at least two layers have micro-holes. Its purpose is to meet the increasing demand for high-density flip-chip I/O. This technology will soon be integrated with HDI PCB to achieve product miniaturization.

The high-density IC substrate technology used for packaging is suitable for flip-chip or bonding substrates. The microvia process provides sufficient spacing for high-density flip-chips. This technology is required even for HDI PCBs with a 2+2 structure.


3. High-level number HDI PCB board

The high-level HDI PCB board is usually a traditional multilayer board with laser drilling from the first layer to the second layer or the first layer to the third layer. The use of the necessary sequential lamination process, and the micro-hole processing on the glass reinforcement material is another feature. The purpose of this technology is to reserve enough component space to ensure the required impedance level. Figure 3 describes this type of typical multilayer board structure.

The high-level digital board technology of high-performance products is suitable for high-level HDI boards with high I/O count or fine-pitch components. The buried via process is not a necessary process in this type of products. The purpose of the microvia process is only to form high-density devices. (Such as high I/O components, uBGA), the dielectric material of HDI PCB can be back-adhesive copper foil (RCF) or prepreg.


In summary, there are five main driving factors for the development of high-performance HDI PCB board that must be considered, and these factors interact with each other. These factors are: circuit (signal integrity); components; substrate; lamination and design rules; consideration of the assembly process, designing such a printed circuit board with microvias is a very complex task, although the circuit is considered Signal integrity is extremely important, but the cost factor cannot be ignored. Based on this, a compromise solution must be considered in actual operation.