PCB Manufacturing FAQ: Hole Size, Via Placement, Solder Mask, and Board Edge Design
Small PCB layout details can cause big problems during fabrication and assembly.
Incorrect hole sizes, vias placed too close to pads, unnecessary solder mask openings, or poor board-edge spacing may lead to soldering defects, weak connections, mechanical interference, or even redesign.
🤠This FAQ covers several common PCB layout issues to check before sending your board files to production.
1️⃣What happens if hole size, pads, or spacing do not match the datasheet?
🔍Common symptom: The drill hole is too small, the pad outer diameter is too small, or the hole spacing does not match the component lead spacing.
‼️Possible impact:
- Through-hole components may be difficult to assemble.
- Soldering reliability may decrease, with insufficient annular ring or damaged plated holes.
- Rework rate may increase in volume production.
💡Suggested fix:
- Use the PCB layout recommended in the datasheet.
- For connectors, terminal blocks, switches, and other mechanically stressed parts, increase pad and mechanical strength where appropriate.
- Before fabrication, use a 1:1 printout or 3D assembly check to verify physical dimensions.
2️⃣What happens if there are vias on pads?
🔍Common symptom: Vias are placed in the middle or at the edge of pads for chip resistors/capacitors, ICs, or connectors.
‼️Possible impact:
- During reflow, solder may drain into the via, causing insufficient solder, weak joints, or voids.
- Small components may shift or tombstone.
- BGA/QFN components may suffer from voids, opens, or reliability issues.
💡Suggested fix:
- Move vias outside the pad area whenever possible.
- If via-in-pad is required, use resin plugging, plated filling, or another reliable via filling process.
- For standard PCB processes, open vias should not be placed directly on small pads.
3️⃣What happens if all vias have solder mask openings?
🔍Common symptom: All vias are exposed, especially vias close to pads.
‼️Possible impact:
- Solder may flow into the vias, reducing solder volume on the pads.
- Exposed copper may increase the risk of solder bridging, solder balls, or shorts.
- Appearance and long-term reliability may be affected.
💡Suggested fix:
- Close solder mask openings for vias that do not need to be tested or soldered.
- Vias near pads should be tented or moved farther away.
- Test-point vias can remain exposed individually; avoid exposing all vias globally.
4️⃣What happens if vias are too close to pads?
🔍Common symptom: Vias are very close to SMT pad edges, or the solder mask dam is insufficient.
‼️Possible impact:
- Solder may be pulled away into the via.
- If the solder mask dam breaks, the via and pad may bridge.
- Batch soldering consistency becomes poor.
💡Suggested fix:
- Increase the distance between vias and pads, and ensure sufficient solder mask dam width.
- For high-density designs, confirm the minimum solder mask dam capability with the PCB manufacturer.
5️⃣What happens if a USB connector is too far from the board edge?
🔍Common symptom: The USB connector opening is not close enough to the PCB edge, or the connector front is blocked by the board edge or enclosure.
‼️Possible impact:
- The USB plug may not fully insert.
- Poor contact or abnormal mechanical stress may occur during use.
💡Suggested fix:
- Place the USB connector according to the board-edge dimensions recommended in the datasheet.
- Use a 3D model to check the connector, enclosure, panel opening, and PCB edge relationship.
6️⃣What happens if a component needs to overhang the board edge but the layout does not reserve space?
🔍Common symptom: Part of a USB connector, Type-C connector, card socket, button, antenna connector, or similar component should extend beyond the PCB edge, but the PCB outline does not allow it.
‼️Possible impact:
- The component cannot sit flat, creating soldering stress.
- External plugs, cards, or buttons may not work properly.
- Mechanical assembly may fail, and the PCB may need to be redesigned.
💡Suggested fix:
- Follow the datasheet recommended edge-mount or board-cutout layout.
- Perform a 3D assembly check before production.
Small layout details can have a big impact on PCB manufacturing and assembly. Checking hole sizes, via placement, solder mask openings, and board-edge spacing before production can help reduce rework, delays, and reliability risks.
👇Preparing your next PCB or PCBA build?
Seeed Fusion provides free DFA/DFM review to help identify potential issues before manufacturing. From PCB fabrication and PCBA assembly to component sourcing, testing, and small-batch production, we help you move from design files to a reliable build with more confidence.
Take a look at Seeed Fusion’s PCB/PCBA service and get free DFA/DFM support before production.
If you have any other questions, feel free to contact us at [email protected]
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