Via Aspect Ratio & Annular Ring Tolerance
Estimate drill aspect ratio and worst-case annular ring using fabrication tolerances.
Live results
| Measurement | Result |
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Formula and worked example
Method. Aspect ratio = plated depth ÷ nominal fabrication drill. Worst-case ring = (minimum pad − fabrication drill − positive drill tolerance)/2 − radial registration.
Assumptions. Drill tolerance is a diameter increase and registration is a radial shift. Use a minimum etched pad diameter. The finished hole is smaller after plating and is recorded separately.
Example. 1.6 mm depth / 0.3 mm drill = 5.333:1. With a 0.65 mm pad, +0.025 mm drill tolerance and 0.05 mm shift, the worst-case ring is 0.1125 mm.