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48 DESIGN007 MAGAZINE I APRIL 2024 How did a product aimed at signal integrity end up being more about documentation? For a little backstory, the Polar team has an unspoken "no business speak" rule at certain times. So, why is this column titled "Drilling Down?" I find it fascinating when a company sets off in one direction, but customers steer it in another. at's what has happened here as customers took a product down a fork in the road we couldn't predict. Your destination isn't always where you initially set off to go, and that's how we got to our subject of drills and drill documentation. Laser-focused, But Rotating Drills Still Play a Major Role Conventional drilling has come a long way, and from a signal integrity perspective, the advent of precision-controlled depth drilling— especially when combined with contact detec- tion—has transformed the high-speed perfor- mance of thicker boards, eliminating trouble- some via stubs which behave to the signal as though they are twice as deep electrically as they are physically. Historically, you had to calculate the stub length, which would cap the maximum frequency at which a channel could operate. Backdrilling the via can release the perfor- mance of the channel. e increased availabil- ity of PCB drilling machines with precision depth drilling has revolutionized the signal integrity performance of high-layer count PCBs. I have oen mentioned that good mod- eling tools can't fix an inherent design flaw or limitation. In the case of via stubs, the mod- Drilling Down on Documentation The Pulse by Martyn Gaudion, POLAR INSTRUMENTS Figure 1: Via stub length of 200 mils requires attention at 4 Gbit/s data rate. Find the math behind this in Signal and Power Integrity Simplified, by Dr. Eric Bogatin.

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