What are HDI PCBs?

What is High Density Interconnect?

PCB is the backbone of every electronic device. Most of the compactness in your new devices, like continually shrinking smartphones (despite packing a plethora of gadgets), and tiny implants is thanks to the smaller and advanced High Density Interconnect (HDI) PCBs. And small circuits aren’t the only gift of HDI technology. HDI circuits are much better at signal transference than conventional PCBs and they are more suited for high-frequency needs as well.

So what is HDI?

High-Density Interconnect

High-Density Interconnect simply means more wiring per unit area. With the use of smaller vias, microvias, and finer traces, more components can be installed on a much smaller piece of the board than conventional PCBs.

According to IPC-2226, an HDI is a PCB with finer lines, less than 100 micrometers in thickness. Vias should be smaller than 150 micrometer and capture pads should be under 400 micrometers in size. This ultimately translates to a higher pad density. IPC recommends the least pad density for HDIs as 20 pads per square centimeter.

This was a long time ago, and when you work with PCB manufacturers that are pushing the boundaries of technology, you can get a much more compact HDI. With trace widths as small as 35 micrometers, vias (microvias) as small as 50 micrometers in diameter and capture pads with diameters of 100 micrometers. This should give you an idea of how far the HDI has come along and how compact you can make your circuits using HDI.

Normally, whenever you are going above eight layers with conventional PCBs and plated through holes, you will have to switch to HDI. does allow you to cut the number of layers and design the same circuit with much smaller dimensions.

HDIs can employ the whole range of vias like Plated Through Hole (PTH) vias, blind vias, buried vias and microvias. Most HDIs use laser-drilled microvias. They are relatively smaller and allow for a more compact circuit. They also improve a circuit’s signal and frequency handling capabilities. A microvia cannot have a diameter of more than 150 micrometers, and an aspect ratio of more than 1:1 (width to height).

Advantages of High-Density Interconnect

There are various advantages of using High-Density Interconnect, instead of a conventional PTH.
• Cost-efficient for high layer counts.
• Replacing plated through holes with microvias in an HDI frees up surface area.
• HDI is relatively energy efficient. Since the components are packed together, there are fewer energy losses in transmission. This is especially beneficial when we use HDI PCBs in battery-powered devices. Like smartphones and wearables. An HDI circuit will drastically improve the operation-per-charge hours of the device.
• Reduction of the BGA pitch is a great advantage of using HDI. With it, you can have BGA pitches as thin as 0.4mm. It allows for a much higher BGA density and reduction of layers than a conventional PCB. For example, if you are going with a standard PTH, dogbone fan-out the solution for a BGA with a pitch of 0.8 mm, you will need at least 7 layers. If you break out your BGA using HDI, you will reduce the number of layers to three.
• Mechanically superior. Since HDIs reduce the dimensions of a circuit, its housing requires less space in the device. The reduction of weight makes it less susceptible to damage through shocks and jerks on the device. It’s one of the reasons why HDI PCBs are employed in devices that are used in harsh environments.
• High-frequency transmission capability. Conventional PCBs that use PTH, cause discontinuities when the signal frequency reaches the gigahertz range. To curb that, costly high-frequency material was used in the PCBs that used PTHs for high-frequency signal transmission. HDI provides better signal integrity at high-frequencies, without the need of special material. HDI PCBs reduce the signal losses and chances of cross delays. This makes them ideal for high-frequency applications.

High-Density Interconnect With Hemeixin

If you are planning on designing your next circuit in HDI, you might want to consider Hemeixin. No matter how good your circuit design is, if it can’t be fabricated, it’s useless. Many manufacturers lack the capability, technology, and experience to fully realize the capabilities of an HDI circuit.
This is where we come in. When you are working with us, you can really push the conventions of HDI designing. We fabricate HDIs with every layer interconnect (or any layer interconnect). So you can reduce the size of your HDIs even further, by eliminating PTHs altogether.
We have the capabilities of manufacturing 28-layer HDI PCBs. This is high enough for even the most ambitious of prototype circuits.
In laser microvias, we can accommodate tiny diameters as small as 50 micrometers. We can also create skipped, telescopic, stacked, tapered and cupped microvias. They can help you with any specialized circuit requirements your device might have.
Designing your Rigid-Flex with HDIs can also be a great way to reduce the space your circuit takes, even more than a simple HDI circuit. It can also be used for devices that might experience mechanical stress, constant bending, and harsh environments. We can help you design a very cost-effective HDI Rigid-flex.

Conclusion

High-Density Interconnect is still evolving as a technology. There are cost barriers, limitations, and design complexities to overcome. Manufacturers and designers all around the globe are working to improve HDI as much as they can because it’s the future of electronics.
HDI is costly if you are employing it for very basic circuitry. But as the complexity of the circuit increases and the numbers of layers increase with it, HDI might prove a much more cost-effective method. Laser drilled microvais that are now an integral part of the HDI technology, have already replaced mechanical drilling for the most part. They are a much more cost-effective drilling solution.
High-Density Integration should be your choice whenever you want a more compact, reliable and electrically superior circuit.

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