Small is the new Smart – A PCB story

Ashissh Raichura

Ashissh Raichura

Tinier hardware products that deliver larger outputs are always preferred in the domain of technology. The relevance is all the more applicable in the context of wearables and IoT products.

Size does matter, but not quite in the way one would expect in the field of technology. End-user preferences tilt in favour of smaller hardware products. The obvious reasons are efficiency in space, easier portability and optimized functioning among others. Behind every small hardware product is a small printed circuit board (PCB).

Often, a smaller product size is critical to your product’s success. This makes it critical to invest in technology that miniaturizes the PCB to the smallest possible size. Doing this enables the components in and around the PCB to fit more snugly together.

Vias are the answer to smaller PCBs

The key technology that can enable a smaller PCB is the use of vias. Considering via stands for path or way in Latin. In electronic terms, a via is an acronym for vertical interconnect access. It is an electrical connection between layers in a circuit that goes through multiple layers. In PCBs, a via consists of two pads in corresponding positions on different layers of the board. These are connected electronically through holes in the board.

PCBTypically, these vias are further sub-categorized by purpose. The most common among these is the through via, which fulfills the most basic of purposes. The through via goes through every layer on the board. This effectively reduces space for routing on the layers of the PCB. Less routing space translates to a larger board size, which defeats the purpose of tiny hardware products. To combat this handicap, it’s essential to make use of blind and buried vias in your PCB design.

Diving deep into the layers of a PCB- Blind & Buried Vias

These vias are fairly simple to understand. The classic blind via connects an external layer to an internal layer, whereas the buried via connects two or more internal layers in the PCB. Using blind and buried vias offers greater flexibility as opposed to through vias, enabling smaller PCB design. However, it’s not all hunky-dory as it sounds. Here’s why:

1) Higher costs: Needless to say, using blind and buried vias is more time consuming and complex. This drastically increases the cost of the PCB in question. While high-volume production will help negate the long-term effects of high costs, blind/buried vias can triple the expense incurred in the prototype testing phase. Therefore it’s essential to get the design and preference of vias absolutely correct in as short a span of time in the prototype phase.

2) Complexity of layers: Use of blind and buried vias also come with limited options in terms of which layers can be connected. The start and end of via need to be at the far sides of a core section on the PCB. This is a thumb-rule to follow in order to maintain structural integrity. Moreover, a multitude of stack-up combinations can be used to connect layers. This means extensive testing is required to determine the best stack-up combination to suit your PCB design. Finally, buried vias only connect the inner layers and need to be accounted for to ensure success of the PCB. Needless to say, the more the layers, the more complicated the process.

A simple hack to avoid this complication is to pre-determine which layers can be connected using blind/buried vias in each stack-up combination. This pre-determination aids in the final decision of which stack-up works best for the PCB design in question.

Smart use of vias paves the way for smaller PCB design

If size is not of key importance, it’s always a safer practice to stick to through vias. However, the demands of end users today skew towards smaller products with higher utility. In such scenarios, blind and buried vias hold the key to really squishing your PCB to its most compact form.

Ashissh Raichura is a veteran techie and serial entrepreneur with over 23 years of diverse experience to his name. A doctorate in Computer Science from Vancouver, he is reputed for setting up a billion dollar business in Canada. Currently the CTO of Healthsaverz, he possesses a plethora of knowledge in BigData, Hadoop, Predictive Analysis, Cyber Forensic Analysis and Cyber Crime Investigation. An IoT futurist, Ashissh holds a fondness for medical/health-tech & smart homes and is now developing an extensive external health-care device. A moonshot thinker with a keen mind, he always sets high benchmarks in the sphere of technology.



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