Since they’ve been created, electronics have been getting smaller, faster, and more efficient. But when you try to cram more components, pins, and connections in a smaller sized board, you’re going to have some problems. These challenges include heat, BGA breakouts and size itself, meaning how are you going to fit your board in that small, oddly shaped enclosure.
Here are a few quick stats:
Board area has remained relatively constant, while the number of leads per square inch has tripled in the last 10 years.
The average number of components has quadrupled in 15 years while the average leads-per-part has decreased by a factor of 4 to 5x.
The number of pins in a design has tripled and the number of pin-to-pin connections has doubled.
With these types of increases not looking to slow down anytime soon, it's important to understand how to address these issues when designing. Let’s focus in on a couple of these issues here, routing a high pin BGA and HDI PCBs.
For many of us the manual planning and routing of the BGA can take several days and if your plan is inefficient you may be adding more layers than needed, which increases cost and we all know our budget isn’t getting any larger. With many BGAs today we place our via capture pads diagonally. I’m sure you’ve seen this in what we call a dog bone fanout.
Dog Bone Style Fanout
But more and more we’re starting to see that dog bone fanout isn’t always an option, this is due to the small pitch size of the pins not allowing enough room to add those vias. For these BGAs we need a via in pad method for breaking out. This is when the via is directly connected to the pad, allowing one to route the signal on a new layer.
Increase Density with HDI
Something else you should keep an eye out for as as your designs continue to shrink is how are you going to cram more components, traces, and overall more complexities onto a smaller PCB without adding extra layers. A method of solving this problem is through the use of high density interconnect (HDI) PCBs.
HDI PCB courtesy of flygold circuit
HDI boards are printed circuit boards with a higher density of tracks and pads when compared to a “normal” PCB. They often include blind, buried and micro vias. Everything is smaller on these boards, traces, spacing, capture pads, ext. HDI boards have the advantage of reduced size and weight, and yet they can still boost the electrical performance of the device. They do have their drawbacks though and you need to be aware of what those are. These are things like smaller components and less space between them.
Embrace Layout Challenges
Miniaturizing our technology whether it be ICs, transistors or PCBs, brings with it many challenges. But challenges are nothing to hide from, we must embrace them, because with new challenges brings with it innovative new solutions. To learn more about the challenges and solutions that plague modern PCB layouts check out this whitepaper.
About the AuthorMore Content by Alexsander Tamari