Hdi circuit boards design

What is HDI PCB?

HDI PCB is the name of a printed circuit board with a large number of interconnects. In other words, it means a PCB with more components and circuits per unit area than a normal PCB.

This complex design is the basis of many electronic products today, from mobile phones to computers and other devices. So what does HDI mean and how is it used in HDI circuit board design and stackup?

4 layers HDI PCB

HDI PCB Meaning

Now that you have an idea of ​​what it is, let’s dive into the definition of HDI PCB:HDI means “high density interconnect”, which indicates the large number of connections that have been placed on the board.

To achieve HDI, everything is miniaturized, and the circuit boards have become smaller and lighter. HDI technology effectively meets the performance and size needs of modern electronic products, including:

Wireless communication devices such as mobile phones
Wearable devices such as fitness trackers
Computers and game consoles
Medical devices
Automotive electronic systems
Aerospace technology
Military electronic hardware

hdi pcb

HDI PCB Stackup

One of the most important aspects of high-density interconnect circuit boards is their stackup, or the arrangement of different layers. The fact that you can pack many components in a small area actually reduces the number of layers required.

But this also requires the right choice of dielectric or insulating layers between the conductive copper layers. Generally speaking, the type of material used must have excellent dimensional stability, be able to withstand lamination, and be easy to process. Options range from FR4 and FR5 to polyimide films.

In HDI multilayer PCBs, different arrangements can be made. Examples include 0-N-0, 1-N-1, and 2-N-2. This type of PCB board can also be rigid, rigid-flex, or flexible, depending on the type of application. In the next section, we will see how this board differs from regular PCBs.

HDI PCB Manufacturing

The HDI PCB manufacturing process, while almost similar to that of standard PCBs, also has some differences. Just like any other board, it starts with engineers making the design of the board, followed by the prototyping phase, and finally the manufacturing process for the HDI board implementation.

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HDI PCB Design

The board is first designed keeping in mind its unique characteristics, such as component density. Also, the fact that these must be laid out in a way that does not compromise the signal integrity and board performance. During the HDI PCB design phase, the following features are determined.

Type of materials used

Number of layers or stack-ups. HDI PCB stack-ups usually consist of fewer layers than standard boards.

Type of vias used along with buried, blind and microvia options.

Number and type of electronic components. Most of the time, these are surface mounted devices with many pins or pads.

EMI reduction strategies such as optimized trace sizes, component grouping and spacing, use of ground planes, etc.

Routing and layout optimization

The HDI PCB design is implemented in the PCB design software. After that, the designer sends it to the manufacturing department for prototyping before the actual production process can begin.

HDI PCB Prototype

Before full-scale production can begin, a test board or prototype needs to be made. HDI PCB prototypes have all the features required to test its different features. These results will form the basis for corrections, if any, to ensure that the board meets every performance and reliability requirement.

HDI PCB Manufacturing

This is where the HDI design is realized and made into an actual product. The HDI PCB manufacturing process is similar to that of traditional circuit boards, except for the type of technology used to print the circuit board and drill the holes.

Since HDI PCB boards require smaller traces and vias, mechanical film printing and mechanical drilling are less viable options. Therefore, laser machines are used to do the job. Laser etching and drilling – despite being more expensive – not only offer precision, but are also capable of processing very small surfaces.

To print the circuits, laser direct imaging technology is used. For vias, a concentrated laser beam is aimed at a point. The heat generated when the material absorbs this energy vaporizes the point, essentially forming a small hole. Note that mechanical drilling can also be used, especially when only a few boards are required.

HDI PCB Cost

As you might have guessed, the complexity of HDI printed circuit boards makes their manufacture a demanding process that requires complex design considerations. It also mostly requires advanced manufacturing techniques.

However, while the above requirements may increase the estimate of HDI PCB costs, the reduction in the number of layers ultimately reduces costs significantly. In general, the cost of HDI boards depends on the following variables:

The amount and type of materials used.

The board stackup characteristics (number of stackups and board thickness).

The type of vias used or the technology used to manufacture them (laser drilling is more expensive).
Different HDI PCB manufacturers will also vary in the pricing of their circuit board manufacturing services, so you can expect these figures to vary widely. To reduce expenses, it is vital to optimize your board for different functions. You may also want to include only what is critical and necessary for your board.

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Conclusion

As the world of digital technology becomes more advanced, the demand for HDI PCB boards continues to grow. This type of board packs many components in a small area, making miniaturized circuits and devices possible.

Although this also means a longer and more demanding manufacturing process, modern HDI circuit boards are becoming increasingly affordable due to the use of automation and other manufacturing techniques.

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