Guides / Rotation
Why pick-and-place placements need rotation correction
The most confusing part of SMT setup — where the rotation offset comes from, and how to fix it once per package.
You export a clean placement file from your CAD tool, load it on the machine, and half the parts go down rotated 90 or 180 degrees. This is the most common surprise in SMT setup — and it isn't a bug in your board.
Where the angle comes from
Every component is supplied at a fixed orientation in its tape & reel, defined by the EIA-481 standard. The pick-and-place always grabs the part at that angle, so the machine's idea of "zero degrees" is really "however the part sits in the tape."
Why CAD and the machine disagree
Your CAD footprint also has a zero-degree reference, set by whoever drew the library following a convention like IPC-7351. When the tape orientation and the footprint's zero don't line up — common for ICs — you get a fixed offset for that whole package type. That offset is the rotation correction.
Fixing it
You don't fix it per board — you fix it per package. The SMTPlace converter applies a validated community rotation table (originally compiled for JLCPCB's assembly service) as it prepares your job, and every package page shows the offset it would get.
Rules of thumb (common tape convention)
- ·QFN → add 90°
- ·SOIC, QFP, TSSOP, SSOP, MSOP → add 270°
- ·SOT-23 family → add 180°
- ·Most two-terminal chips → no correction
See the full list in the package size chart, and always verify against your own footprint library — conventions vary.
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