Originally published at: https://www.protoexpress.com/blog/case-study-resolving-emi-and-routing-issues-in-medical-optical-scanner/
In a recent collaboration, our PCB design engineers worked on a medical circuit board for a leading healthcare device manufacturer specializing in advanced optical scanners in ophthalmology. The primary objective of this project is to integrate an optical scanner with a circuit board to control the scanner’s movement in the X, Y, and Z directions. This integration enables detailed eye image captures. The circuit board layout comprises critical components such as stepper motor connectors, inductors, switching regulators, motion controllers, and microcontrollers. In this case study, you’ll learn how we resolved EMI and circuit board routing issues in the optical scanner…
I see that you have used polygons to route high-current paths. Are there are any other techniques to route them without the risk of overheating?
I’m laying out a BGA for the first time and feeling a bit overwhelmed with some of the finer details. It’s a 9x9 BGA with a 0.4mm pitch, so I’ve opted to use vias in pads (filled) to break out the signals.
My question pertains to the bottom layer of the board beneath the BGA. It’s currently empty, and I’m considering placing passive components directly below the BGA and using filled through-holes to connect them to the bottom layer of the board. Is this a viable approach, or are there potential issues I should be aware of?
While many resources online focus on fan-out strategies for BGAs resembling QFP MCUs, I’m unsure if this is necessary for my particular BGA. Any insights or advice would be greatly appreciated.
Although a 0.4 is a fairly tight pitch, you’re luck you only have potentially 81 pins to deal with. Going with via-in-pad will also make the job much easier. And, if you’re referring to the bypass caps as the “passive components” then you should be right on target. Assuming you don’t violate any clearances or placement rules, placing those caps directly underneath and keeping them as close to the pin (ball) as you can, you should get about as good of results as is possible. For a small BGA like this the fanout should be both fairly obvious and fairly easy. If you find yourself facing larger BGA packages in your upcoming projects you might want to take a look at BGA Breakouts and Routing by Charles Pfeil, published by Mentor Graphics. It shows lots of examples and provides some insight as how to go about finding the best approach.
Yes. You can use a plane to handle high current requirements.