Anatomy of next-gen IoT PCBs
Next-generation IoT printed circuit boards are taking on a completely different anatomy than conventional PCBs thanks to a group of technologies that savvy IoT PCB houses are deploying. The whole idea behind these technologies is to meet the size, performance, reliability and cost demands of advanced IoT devices.
These technologies include:
- High-density interconnect (HDI),
- Micro via,
- Multi-chip modules (MCMs),
- Direct die attach on the substrate, and
- Package-on-package (PoP).
Just like the name implies, HDI PCBs allow greater board density so that you can put more compact devices into a small circuit board area, like on the small flex or rigid-flex circuit boards used in most cases for IoT devices. HDI PCBs also bode well for lower power consumption and improved electrical performance. When components are placed in closer proximities, shorter distances translate into better electrical performance, thus lower power consumption. Plus, HDI PCBs require a reduced number of materials due to their high density, resulting in less cost.
So, as can be well imagined, the IoT PCB designer is constantly fighting for every little tenth of an inch of circuit board real estate. This is where HDI PCBs can open up the small circuit board and allow the designer to pack more electronic functions into those tiny areas. But it’s not only on one PCB side where this high density is found, it’s also on the backside of an IoT flex or rigid-flex circuit board that offers a greater area for customer demanded circuitry.
Micro vias are leading the HDI charge. These are extremely small laser-drilled holes that allow electrical connections to be made between the layers in a multilayer IoT flex or rigid-flex circuit board. Since they’re considerably smaller than regular plated-through vias that go from top to bottom of a board, micro vias conserve a significant amount of IoT PCB real estate, and thus increase reliability.
Here’s a more detailed explanation of how micro vias save that space: Micro vias are vias that are typically smaller in size and diameter and are generally used within internal layers of a particular PCB. They are used in the form of either blind or buried vias. Blind vias start from top or bottom side of the board and terminate inside internal layers, say starting at the top and terminating at layer 5 on an eight layer board. Buried vias, on the other hand, are micro vias that start and terminate inside the internal layer structure of the board.
Using micro vias uses less space on the board, as well as frees up the top and bottom layer, allowing more components to be placed, thereby freeing up valuable real estate on a board.
Now, we come to MCMs. The form factor remains the same as a conventional integrated circuit (IC). However, the technology has advanced so much in recent years that chipmakers are placing multiple ICs on a single silicon die or chip. Here again, more complex and powerful circuitry is packed into ever-shrinking components to meet IoT OEM customer requirements.
Direct die attach is also starting to come into the picture. This means a chip without its conventional device packaging is directly placed on the IoT PCB using any one of several techniques known as wire bonding, flip chip, wedge bonding or chip on board. But device packaging isn’t completely out of the picture for IoT PCBs. There’s still the PoP that chipmakers use to stack one packaged chip on top of another to conserve board area.
All in all, you can see with these technologies that the state of the art in IoT PCBs is progressing at a steady clip to hand the IoT OEM the best quality and reliability possible at well-planned cost structures.
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