1. The one genuinely hard conflict: legend cannot sit where solder goes
Among legend failure modes, only one class is structural and has nothing to do with ink quality: legend landed on a surface that must stay free of ink.
The tolerance page already defines those surfaces indirectly. Solder-mask clearance must be 0.003" larger than the pad (mask swell), which means there is a ring of metal around every pad that has to stay exposed. Solder-mask registration is ±0.003", which means the actual position of that clearance floats within a range. Legend inside that "clearance plus float" is a conflict.
The same class of surface includes:
- Plated through-holes and annular rings. The hole takes solder; the ring is a joint.
- Gold fingers. Listed under special processes on capabilities. It is a mating contact.
- Castellated half-holes. Also a special process; the cut face is itself a joint.
- Test points and probe landings. Capabilities states
100% full coverage electrical test; flying probe or fixture has to reach bare copper.
What these share: they must stay solderable or conductive. Ink on them is a defect, not a cosmetic issue.
The important part is that fabrication has exactly three options here, and no fourth:
| Handling | What it does | The cost |
|---|---|---|
| Clip | Cuts away the part of the character overlapping the clearance | Character is mutilated, may read as a different character or not at all |
| Shift | Moves the character or the whole group to adjacent free space | The designator-to-component association can become ambiguous |
| Omit | Does not print that legend block at all | Assembly and repair lose a piece of information |
All three make your drawing and the physical board disagree. The only real choice is whether you made that decision during review, or the fab made it for you while preparing production data.
Checkpoint 01 on the quality page is CAM data review; the page states that undersized openings, insufficient spacing and unbuildable stackups get flagged back to you. Legend conflicts travel the same channel — they will be seen. But what happens after they are seen, if the drawing is silent, falls back to common practice.
2. Legend position has no tolerance of its own — it inherits
This is the second common misconception: that legend has its own registration specification. What actually determines where a character ends up are the things around it that already have tolerances.
The tolerance page states imperial values are authoritative, metric is for convenience, and values follow IPC-6012 acceptability standards. The items that bear directly on legend position:
| Tolerance item | Published value | How it moves your legend |
|---|---|---|
| Soldermask registration | ±0.003" | The real clearance boundary floats; legend must yield that margin |
| Soldermask clearance vs pad | 0.003" larger | The keep-out is bigger than the pad you drew |
| Pad spacing | <0.010" may need special processing | Fine-pitch gaps have no safe legend space to begin with |
| Board outline | ±0.005" | Legend near the edge can lose part of itself |
| Scoring location | ±0.003", score line centre is the board edge | Legend crossing a score line gets split in two |
| Hole location (annular ring) | ±0.003" | The real position of the ring floats too |
Add one that is easy to miss: the tolerance page states outer copper must stay ≥0.005" from the board edge, inner copper ≥0.010" (except scored arrays). Legend is not copper and is not bound by that line, but it tells you the edge region is already a squeezed area.
So "how fine can your legend go" is the wrong question. The right one is: with mask clearance, pad spacing, outline and scoring tolerance all at their worst combination, how much clear space is left here for a character. If the answer is zero, the prettiest legend layer still gets clipped at data preparation.
The tolerance page also says tighter tolerances may be available on request — talk to engineering about specific requirements. That applies to legend as well, but to have that conversation you have to state the requirement as something verifiable, not "legend must be clear".
3. Where legend lands in the flow: what is published and what is not
The capabilities page publishes a ten-step flow: 01 Cutting → 02 Inner Layer → 03 Lamination → 04 Drilling → 05 Plating → 06 Outer Layer → 07 Solder Mask → 08 Surface Finish → 09 Profiling → 10 Testing.
Note: legend is not a separate step in that list. The related equipment you can find in the equipment list is the Atma Solder Mask Screen Printer, named under the solder mask process.
This has to be stated plainly, because it directly bounds what you can commit to on a drawing:
What is published: the inspection evidence legend depends on sits at checkpoint 09 on the quality page — solder-mask registration and thickness, surface-finish thickness (gold and nickel on ENIG, for instance), then outline tolerance and hole-position accuracy on a vision system after routing. In other words, the set of positional relationships legend hangs off (mask, outline, hole position) all have in-process checkpoints.
What is not published and must be confirmed in the project file: which process step legend actually belongs to, its order relative to surface finish (08), and which imaging method is used. Those three affect final appearance and durability, but the site publishes no single position on them. Do not infer it from the numbering of the flow diagram, and do not assume industry common practice is this factory's practice.
In practice this means: if your legend has a hard requirement — a particular mark must stay fully legible after surface finish, or must survive downstream cleaning — raise it as an explicit question at RFQ, have engineering confirm it, and get it into the project file. That is the same logic capabilities applies to impedance, blind/buried vias and any-layer: the capability exists, but the specific window is bounded by the project confirmation record.
4. Colour is not a free field
The quote form on the site's PCB Layout service offers legend colour as White / Black / Yellow.
Those are the values selectable on the form, not a statement that only three are possible — but it does tell you something: legend colour is an item you declare at RFQ, not a default. If your design depends on specific contrast (light characters on dark mask, or a mark that a camera has to read), that choice gets confirmed together with mask colour rather than left blank.
Contrast already has a clear position in traceability marking design: the different carrier forms for a board ID — human-readable characters, machine-readable code, or both — place different demands on surface condition and contrast. The designator layer is no different. Read by a person and read by a machine are two requirement sets.
5. Board ID and designators compete for the same real estate
This is the legend problem most likely to blow up late in a project, and at bottom it is an area problem.
Traceability marking design concludes: a unique board ID needs a fixed area that will not be hidden by components, connectors, heatsinks, shields or labels; that area belongs on the mechanical or assembly drawing, not as a box dropped onto the legend layer; and when board area is genuinely tight, board-ID readability should be treated as a layout constraint during review rather than squeezed in at the end.
Stack that on the first four sections and you get the full legend area budget:
- Pad and mask-clearance keep-outs (section 1) — unavailable
- The tolerance-squeezed band at board edges and score lines (section 2) — high risk
- Component body footprints and shadowed areas (per the traceability article) — unavailable for board ID
- What remains is the area available to designators and marks
Designers commonly place designators for readability first, then hunt for somewhere to put the board ID, and the board ID ends up at the board edge or under a component. The correct order is the reverse: lock the board-ID keep-out against its readability requirement first, then place designators, which are free to follow their components anyway.
6. The lines your drawing needs
Collecting the previous five sections into items you can write into a file. These are not a template; they are the places where a decision is required. Leaving them blank hands the decision away.
Four lines that must be written:
- Handling priority when legend collides with a pad. State explicitly whether clip, shift or omit takes precedence, and which legend is never omissible (polarity marks, warning text).
- The non-omissible legend list. Identify it by location or category; "don't omit important marks" is not an instruction.
- Legend colour together with mask colour. Declare both; leave neither to default.
- Board-ID keep-out. Per traceability marking design, place it on the mechanical or assembly drawing, and state whether it must remain readable after assembly and from which side.
Three items to raise as questions and have engineering confirm into the project file:
- Required order between legend and surface finish (step
08), if you have a hard requirement. - Whether a specific mark must stay fully legible after downstream processing.
- If a mark will be camera-read, the reading method and contrast requirement.
What you can request at acceptance: the quality page states one record per job and that the full production record can be supplied on request, with IPC-A-600 Class 2 and UL796 as the acceptance standards, and checkpoint 09 covering mask registration and thickness, surface-finish thickness, and post-routing outline and hole position. The positional relationships legend depends on are on record — provided your requirement was verifiable on the drawing.
7. When to reconsider the approach
Three exit signals:
- Legend keeps colliding with fine-pitch parts. The tolerance page already states pads within
0.010"may need special processing; those areas have no legend margin to start with. Consider moving designators outside the component outline or switching to zone numbering. - The board genuinely cannot fit the required marks. That is a layout problem, not a legend problem. Handle it the way traceability marking design does — as a constraint resolved during review.
- Marking requirements exceed the general case (resistance to a specific cleaning process, specific contrast, machine reading). Those go through engineering confirmation, the same way capabilities handles impedance
±5%, blind/buried vias and any-layer: confirm feasibility and window first, then write it into the project file.
FAQ
Q1: If legend sits on a pad, will you just fix it?
It will be seen. Checkpoint 01 on the quality page — CAM data review — catches undersized openings and insufficient spacing, and legend conflicts travel the same channel. But "seen" and "handled the way you intended" are different things. Handling is limited to clip, shift or omit; with no priority on the drawing, it falls back to common practice. To control the outcome, put the priority and the non-omissible list on the drawing.
Q2: What is your minimum legend character height and line width?
That number is not in the published specifications. The capabilities table lists layer count, board thickness, line/space, hole size, aspect ratio and copper weight across three columns; legend is not broken out. Treat it as an engineering-confirmation item and raise it at RFQ along with mask and legend colour, bounded by the confirmation record. Do not design to a generic value found elsewhere.
Q3: Is there a separate registration spec for legend position?
There is no independent spec. What determines a character's final position are the objects around it that already carry tolerance: mask registration ±0.003", mask clearance 0.003" larger than pad, outline ±0.005", scoring location ±0.003" (score line centre is the board edge), hole location ±0.003". Design to the worst-case combination; see the tolerance page for the original table.
Q4: Is legend printed before or after surface finish?
The published ten-step flow (01 Cutting → 10 Testing) does not break legend out as a step, and the site publishes no position on its order relative to step 08 surface finish. If you have a hard requirement — a mark must stay fully legible after surface finish — raise it as an explicit question at RFQ and have engineering confirm it into the project file. Do not infer it from the flow numbering.
Q5: Will V-cut cut through legend on an array?
Yes, if legend crosses the score line. The tolerance page states the centre of the score line is the board edge, with scoring location at ±0.003". Legend crossing a score line will be split, and the split position floats. Legend near the edge is also subject to outline tolerance ±0.005". On array designs, place legend treating the score line as the real board edge.
Q6: Can board ID and designators share one area?
Not advisable, because their constraints differ. Traceability marking design separates them explicitly: designators serve assembly readability and follow their components; a unique board ID serves quality investigation and field analysis, needs a fixed area that is not obstructed after assembly, and belongs on the mechanical or assembly drawing. The placement order should be board-ID area first, designators second.
