10 DFM checks to run before your first production run
A practical checklist to catch the design issues that most often derail a first PCBA build at a contract manufacturer.
Most first production runs do not fail because of the electronics. They fail on details that are cheap to fix in CAD and expensive to fix on the line. These are the ten checks we run on every design before it goes to a contract manufacturer.
1. Footprints match the parts you actually buy
Check every land pattern against the manufacturer datasheet of the exact part number on the BOM, alternates included. A 0.1 mm pad difference on a QFN is enough to cause voids and tombstoning.
2. Fiducials and tooling holes
Put at least three global fiducials on the panel and local fiducials near fine-pitch parts. Leave enough clearance around them.
3. Panelization agreed with the EMS
Agree on the panel size, break-away tabs and V-score positions with your manufacturer before you order boards. Their line has its own constraints.
4. Component-to-edge clearance
Keep parts away from the board and panel edges. Depaneling puts stress on ceramic capacitors, and they crack.
5. Thermal relief on large copper pours
Pads connected directly to large planes cause cold joints and uneven reflow. Use thermal relief on them wherever the current allows.
6. Via-in-pad strategy
If you have vias in pads, specify whether they must be filled and capped. If you don’t, solder wicks away from the joint.
7. Test access
Aim for a test point on every net that matters. Place them on one side of the board, on a grid of at least 1.27 mm, and away from tall components.
8. Polarity and orientation markings
Every polarized part needs a clear silkscreen marking that stays visible after placement. AOI and manual inspection both depend on it.
9. BOM hygiene
Use one manufacturer part number per line, list approved alternates, and set the DNP (do-not-place) flags consistently. Make sure the BOM matches the pick-and-place file.
10. A complete, consistent data package
Send Gerbers or ODB++, drill files, the pick-and-place file, the BOM, assembly drawings and the fab notes, all from the same revision. Mixed revisions are the most common cause of a delayed first build.
Want a second pair of eyes on your design? Get in touch and ask about our DFM review.