In CAD, silkscreen and board markings often look like finishing touches. In CAM review, they are a common reason a job stops after copper and drill are already clean. PCB silkscreen and marking issues delay orders because the legend layer has two jobs at once: it has to stay readable for assembly, and it has to print without landing in solderable areas. UL marks, date codes, factory identifiers, serial numbers, and QR codes sit in the same real estate, but they are contractual and sometimes certification-related. If characters sit on pads, text is too small to print, or mark content and location are left open, the job cannot be tooled on an assumption.
This page is for PCB designers, layout engineers, and manufacturing engineers who put Gerbers, drawings, and fabrication notes together. It walks through what silkscreen and markings actually include, why process limits show up on the finished board, what is worth deciding before release, how the same problems appear in CAM, how those findings usually get closed with the customer, and what to scan before you submit files. It is an overview of the problem domain, not a punch list of isolated defects.
The same themes keep coming back in review: characters drawn on pads or too close to openings; character height and stroke too small for a readable print; UL, date/cycle, factory code, production number/SN, or factory logo never confirmed; a UL request that does not match the laminate or legend ink; and a QR or 2D code with no defined content or position.
| EQ Category | Typical CAM Query | Main Trigger or Source of the Issue | Typical CAM Consideration / Resolution |
|---|---|---|---|
| Legend on or near pads | Can this text be clipped, moved, or left as drawn? | Characters sit on pads or crowd pad/opening spacing | Decide whether ink in the solderable area is acceptable; if not, agree on an edit |
| Unprintable character geometry | Can undersized text be enlarged, relocated, or omitted? | Height or stroke is too small on designators or logos | Choose among a query, a limited artwork change if space exists, or omission—none of these should be assumed |
| Factory / regulatory marks | Which identifiers are required, what do they say, and where do they go? | Notes say "add standard marks" with no coordinates or strings | Confirm who draws the mark, where it lives, and the exact string that will appear |
| UL vs. construction | Is a UL mark allowed with this laminate and legend ink? | The mark is requested against a board or ink system that does not line up with it | Treat this as a construction question, not only an artwork move |
| QR / 2D code | Who owns the payload, what is printed, and where? | The file says "add QR" with no data and no reserved zone | Freeze content or the generation rule, plus a location that can actually print |
Those five rows are the map for the rest of the page: customer legend that has to print, and identifiers that have to be confirmed.
What PCB Silkscreen and Board Marking Actually Include
Two different things share the same ink layer, and mixing them is how a lot of CAM holds start.
Silkscreen (legend) is the graphics customers usually draw: reference designators, pin-1 and polarity marks, outlines, warnings, customer logos, and similar text or symbols. The point is simple. After the board is built, someone still has to read orientation and part identity.
Board marking is the regulatory and traceability set: UL mark placement, date code or cycle code, factory code or vendor ID, production number or SN, and QR or other 2D codes. Some of these belong in customer artwork. Others are added by the fabricator after CAM gets a clear answer.
Ownership is the first split that needs to be written down. A customer logo in the Gerbers is customer artwork. A factory logo silkscreen, date code, factory code, or SN is often factory-added. UL marking may appear only as a note, with no reserved location. If the package never says who draws what, CAM is left to invent a marking plan. That is not a shop-floor decision.
Silkscreen is not copper and not solder mask. It sits on cured mask and competes with pads, vias, unmask openings, connectors, and board edges. A string that looks balanced in layout can still sit on a pad, crowd a fine-pitch row, or leave no home for a required factory mark.
Readability after print and cure is a manufacturing requirement, not a CAD zoom setting. Character size, stroke, and placement are how the legend actually exists on the board. Mark content and location are how the identifier plan actually exists. Both have to survive the process and incoming inspection.
| Item | Typical owner | What has to be defined | Why CAM cannot guess |
|---|---|---|---|
| Reference designators, polarity, outlines, warnings | Customer legend artwork | Location relative to copper and mask openings; printable geometry | Clipping or moving text can hide a needed identifier or change assembly meaning |
| Customer logo | Customer artwork | Size, stroke, keep-out from pads | Fine logo strokes follow the same print limits as small designators |
| Factory logo silkscreen | Often factory-added; sometimes customer-drawn | Who supplies it, location, acceptable size | An unplaced logo either lands on a pad or disappears without approval |
| UL mark | Mixed: requested by the customer, applied only if the construction allows it | Required or not; compatible laminate/ink; reserved location | The wrong mark or the wrong construction can fail a certification review |
| Date / cycle code | Typically factory-added unless already drawn | Format or polarity of the code, plus location | A date code PCB requirement with no site and no format is incomplete |
| Factory code, production number, SN | Typically factory-added | Required or not; content/format; location | Identifiers that wander or change content from board to board create incoming-QA risk |
| QR / 2D code | Customer-defined payload or factory-generated by a stated rule | Content owner, payload or generation rule, coordinates or keep-in zone | A code with no data and no site is not a complete requirement |
How Silkscreen Is Applied and Why Process Limits Matter
Legend is usually screened or inkjet-printed onto cured solder mask, then cured. Factory logos and other added marks generally use the same physical layer, or an agreed alternate method. Either way, they inherit the same clearance and size constraints.
That is why "it looks fine in CAD" is not the same as "it will print as drawn." Stroke width, character height, and spacing have to survive print resolution, ink spread, and the steps in mask over copper. Features that sit on pads, in solderable openings, or across large mask/copper steps tend to print poorly. They can also put ink where solder is supposed to wet.
When characters are designed onto pads, or sit too close to pads, finished text often comes out blurred or incomplete. When the character is actually on the pad, the problem is no longer only cosmetics. Ink in the solderable area can affect soldering. When height and stroke are too small, the finished characters can blur even if they never touch a pad.
If the artwork cannot be printed as drawn, CAM has to change it, ask about it, or hold the job. Nobody in CAM should assume it is acceptable to clip a designator, drop a logo, or slide a factory mark into an empty-looking region the customer still needs.
Key Engineering Considerations Before Release
Most of these delays are avoidable in the release package. CAM only has to invent answers when the files stay silent.
Clearance from solderable features. Legend should not sit on pads or crowd pad edges in a way that puts ink on copper or breaks the text. Silkscreen on pad shows up in CAM because a print layer and a solderable opening are occupying the same place. Tight spacing to pads leads to the same family of results: incomplete characters, blurred edges, or ink that reaches the opening.
Character geometry. Height, stroke, and spacing between characters and lines have to remain complete after print. Dense reference designators and fine logos are the usual sources of undersized text. A factory logo drawn by the customer is not exempt. It uses the same ink and the same process.
Keep-out thinking. Pads, unmask openings, tight connector rows, and board edges are competing real estate. Customer text and factory marks both need a legal home. On a dense board, preferred and fallback locations for factory marks keep CAM from choosing among leftover scraps.
Mark ownership and content. Decide which items the customer will draw and which the factory will add: UL, date or cycle code, factory code, SN, QR, factory logo. If a specific string or format is required, write it down. "Add standard marks" with no coordinates and no content is not a marking plan.
Certification compatibility. UL mark placement is not only a graphics problem. The request has to match the specified laminate and legend ink. Empty space on the board does not fix a construction conflict.
Placement hierarchy. On a crowded board, list a primary site and an alternate for factory-added identifiers. That one note often removes an entire clarification loop.
These are the same themes that later appear as EQs: characters on or near pads, height and width that will not print, marks with no content or location, UL versus material or ink, and QR content and position left open.
Common Silkscreen and Marking Issues Found in CAM Review
Most delays fall into two groups. One is whether customer characters can print and still leave the pads solderable. The other is whether factory and regulatory identifiers were ever defined. Something that looks cosmetic in layout becomes a fabrication or assembly risk once ink is committed to the board. CAM should not clip, move, or omit text on its own, and it should not invent UL, date, SN, or QR content.
The subsections below map that landscape. They do not try to exhaust every variant.
Silkscreen Encroaching on Pads or Tight Spacing
Characters drawn on pads, or drawn too close to pads and openings, are a high-frequency CAM finding. After print, the text is often incomplete or blurred. If ink reaches the solderable area, readability is no longer the only issue.
Ink on pad can affect wetting, solder-joint appearance, and inspection. Leaving that condition alone is generally not an option in CAM, because the legend layer and the opening are in conflict. The real question is whether the customer will accept clipping, relocation, or another defined change—not whether the artwork "almost fits."
Character Height and Stroke Too Small to Print Clearly
Text that reads cleanly on a zoomed CAD view can print broken, filled-in, or illegible once height and stroke drop below what the process can hold. Dense reference designators and fine logos, including a factory logo silkscreen drawn as artwork, are the usual sources.
CAM then has to ask, enlarge or move the text if space exists, or omit it. None of those choices should be implicit. Dropping a designator that assembly still needs, or growing a logo onto a pad, only trades one problem for another.
Factory Marks, UL, Date Codes, SN, and Logos Not Confirmed
Review often stops on marking intent: whether UL, cycle or date code, factory code, production number or SN, and factory logo are required; what they contain; and where they go.
Customer files often leave no reserved space. Fabrication notes often say "add standard marks" with no coordinates and no content. That pair is incomplete. Wrong content or a wrong location can fail incoming inspection or a certification audit. Confirming UL mark placement, date code PCB format, factory identifiers, and logo ownership before tooling is the control. Guessing after CAM is not.
UL Mark Conflicts with Specified Laminate or Legend Ink
A UL mark is tied to a recognized board construction and ink system. The requested mark can conflict with the chosen laminate, stack-up, or silkscreen ink even when there is empty space on the board.
This is an engineering clarification, not a simple artwork move. Sliding the graphic to a new corner does not fix a mismatch between the identifier and the materials.
QR / 2D Code Content and Location Left Open
QR and similar codes need defined data or a defined data owner, a location that can print, and enough size and contrast to survive legend print. "Add QR" with no content and no coordinates is not a complete requirement.
Codes follow the same pad-clearance and minimum-feature constraints as other silkscreen. A code on a pad, or drawn smaller than a stable print, fails for the same physical reasons as a cramped designator.
How These Issues Affect Fabrication and Order Flow
These findings are not pedantic artwork comments. They decide whether the job can be tooled, assembled, inspected, and accepted.
Unprintable or pad-overlapping legend means artwork edits, extra CAM cycles, or a hold on panel and tooling. Copper and drill can already be acceptable. The legend layer can still keep the order from moving.
Ink on pads creates assembly risk. A board can be fabricated and shipped with that condition if nobody stops it, and still produce poor wetting, odd solder appearance, or inspection noise at SMT.
Undersized or crowded text produces lot-to-lot readability variation. Marks that move from board to board, or change content because the factory had to improvise, hurt traceability. Incoming QA and field tracking both depend on identifiers that stay stable in content and location.
Incorrect or missing UL, date, SN, or factory identifiers can fail customer or agency checks after build. An unspecified QR, a UL-versus-material question, and an undefined mark location are typical stop-the-line EQs. They are not judgments the shop floor should make.
Each clarification loop delays tooling release. That is why silkscreen and marking problems show up as schedule problems even when they never touch the netlist.
| Problem family | What CAM typically sees | Fabrication / assembly effect | Order-flow effect |
|---|---|---|---|
| Silkscreen on pad or tight pad spacing | Characters in or crowding solderable openings | Blurred or incomplete text; ink that can interfere with soldering | Artwork hold until clip, move, or accept is confirmed |
| Undersized height or stroke | Fine designators or logos that will not print complete | Unreadable finished legend; inconsistent appearance across lots | Query or limited edit before print tooling |
| Unconfirmed UL / date / factory code / SN / logo | "Add marks" with no site or string | Risk of the wrong identifier, or no reserved space | CAM cannot add marks without written confirmation |
| UL vs. laminate or ink | Mark requested against an incompatible construction | Certification risk even if the graphic fits | Engineering clarification of materials and marking |
| QR / 2D code undefined | No payload and no coordinates | Unprintable or unauditable code | Hold until content owner and location are frozen |
Practical Engineering Checklist for Silkscreen and Marking
- No legend on pads or on copper that will be soldered.
- No legend in documented keep-outs.
- Smallest designators still look complete at finished size, not only in a zoomed CAD view.
- Logo strokes, including factory logos in customer artwork, are not hairline features.
- Every required designator still has a legal location after pad-clearance cleanup.
- UL mark: yes/no; compatible with this laminate and ink; location reserved.
- Date or cycle code: yes/no; format; location reserved.
- Factory code / production number / SN: yes/no; content; location reserved.
- Factory logo: customer-drawn or factory-added; location reserved.
- QR / 2D code: content or generation rule defined; position defined.
- Fabrication notes and silkscreen layers name the same marks.
- Notes do not say only "add standard marks" with no site or string.
Closing
Silkscreen is how assembly reads the board. Markings are how customers, factories, and auditors accept the board. PCB silkscreen and marking issues delay orders when those two jobs stay implicit: characters on or too close to pads, text too small to print, and UL, date code, factory identifiers, SN, logos, or QR codes with no confirmed content and location.
Before release, settle clearance, character geometry, mark ownership, and certification compatibility so CAM is not writing the plan for you. After an EQ, answer the finding directly—accept, clip, move, omit, enlarge, define the string and site, or change construction—so tooling can proceed. The checklist is the short pass over the same items in the Gerber package.
If the layout is dense, or the notes only say to add marks, close those answers in the release package rather than in a CAM loop. When the files already state them, legend and marking stop being a tooling hold and go back to what they should be: readable information on a finished PCB.
FAQ
Q1: If silkscreen sits on a pad in the Gerbers, can CAM just clip it and proceed?
A1: Not without confirmation. Silkscreen on pad is a print problem and a solderability problem. CAM can propose clipping or moving the text. Leaving ink in a solderable opening, or quietly removing a designator, is still a customer decision.
Q2: Why does text that is readable in CAD come back as blurred or incomplete?
A2: Legend is printed ink on mask, not a vector display. When character height or stroke is too small, or spacing to pads is too tight, print resolution, ink spread, and mask topography can break or fill the characters. That is a process limit, not a zoom-level limit.
Q3: Who should draw the UL mark, date code, factory code, SN, and factory logo?
A3: Whoever the marking plan names. Some items belong in customer artwork; many identifiers are factory-added. The package needs required versus not required, the content or format, and a reserved location. "Add standard marks" is not enough for UL mark placement, a date code PCB requirement, or factory logo silkscreen.
Q4: Why would a UL mark be rejected when there is empty space on the board?
A4: Because UL marking is tied to the recognized laminate and legend ink, not only to available graphics area. The requested mark can conflict with the specified construction even when placement looks easy.
Q5: The drawing says "add QR code." What else does CAM need?
A5: Content or a defined generation rule, a data owner, and a location that can print. QR codes use the same clearance and feature constraints as other silkscreen. A note without payload and coordinates is incomplete.
Q6: Do factory-added marks follow different design rules than customer legend?
A6: They use the same physical layer, or an agreed alternate method. They still cannot sit on pads or print below a stable character size. Factory addition changes who draws the mark and when. It does not change the need for clearance and readable geometry.
