What Does 94V-0 Mean on a Circuit Board? UL Rating and E-Number

You open a power supply, an LED driver or a remote control and find “94V-0” printed on the green board, usually next to a small logo and a code starting with “E”. The short answer: 94V-0 means the board’s base material passed the UL 94 vertical burn test at the V-0 level, the strictest of the three vertical classes. In that test, a burning specimen must go out within 10 seconds and must not drop flaming particles that ignite cotton below it. It is a flammability rating for the material. It does not identify the circuit, and it does not mean the whole product is UL certified. This guide covers what the mark means, how the test works, how to look up the E-number, and what to ask for when you order boards.

1. What Does 94V-0 Mean on a Circuit Board?

It is a flammability class. “94” refers to UL 94, the standard test for how plastic materials burn. “V” means the specimen is tested vertically, and “0” is the best of the three vertical classes (V-0, V-1 and V-2). Printed on a PCB, it tells you the board construction was rated V-0 for flammability.

• It describes how the laminate and board construction behave in a flame test.
• It says nothing about voltage, current, circuit function or the device model.
• It is common on FR-4 boards in consumer and industrial electronics, where the end product’s safety review usually expects a flame-rated board.

Why does it matter to you?

If you are repairing a device, the mark is not useful for finding a replacement part (section 5 explains why). If you are designing or buying boards, the rating matters because the safety standard for your end product may require a minimum flammability class for the printed board, and your supplier has to prove it.

2. How Is the UL 94 V-0 Test Run?

A bar of the material is clamped vertically and a flame is applied twice for 10 seconds each. The lab times how long it keeps burning (afterflame) and glowing (afterglow) after each application, and watches whether burning drips ignite a layer of cotton below. Five specimens are tested, so the total covers 10 flame applications.

These are the pass criteria UL Solutions publishes for the three vertical classes:

Criterion	V-0	V-1	V-2
Afterflame time, each specimen	≤10 s	≤30 s	≤30 s
Total afterflame, 5 specimens (10 applications)	≤50 s	≤250 s	≤250 s
Afterflame + afterglow after second application	≤30 s	≤60 s	≤60 s
Flaming drips ignite the cotton	Not allowed	Not allowed	Allowed
Specimen burns up to the clamp	Not allowed	Not allowed	Not allowed

Does V-0 mean the board cannot drip or burn?

No. V-0 material can still char and burn while the flame is applied. The rating limits how long it keeps burning once the flame is removed. Drips are also allowed, as long as they do not ignite the cotton. The difference from V-1 is speed: a V-0 specimen must go out within 10 seconds, while V-1 allows 30.

3. What Do the Other Markings Next to 94V-0 Mean?

They usually identify who made the board, not what the board does. Next to 94V-0 you will typically find the board maker’s logo or trademark, a UL Recognized Component mark and an E-number, often with a date code and a board revision. The exact set varies by board maker, and the marking requirements in UL 796 (the standard for printed wiring boards) are not published in full, so treat the list below as what you will commonly see rather than a fixed rule.

Marking	What it usually means
94V-0	Flammability class of the board construction
Backwards “UR” logo	UL Recognized Component mark
E + digits (for example, E237305)	The UL file number of the company that holds the recognition
Maker logo or letter code	The PCB fabricator’s trademark
4 digits such as 2341	Usually a date code (year and week), set by the maker
Text such as “REV A” or a part number	The product designer’s own board number, if they printed one

The last row is the useful one for repairs. A board number printed by the product designer is the closest thing to a model number on the PCB itself.

4. How Do You Look Up an E-Number in UL Product iQ?

Search the number in UL Product iQ. The basic search works without logging in and shows the company that holds the file, its UL category code (CCN) and category name. Full guide information needs a free account.

1. Open Product iQ and type the full E-number, including the “E”.
2. Read the company name and category in the results.
3. For printed boards, the category is usually “Wiring, Printed” with a code starting ZPMV.

What does a real lookup show?

As an example, a search for E237305 (an E-number that shows up often in related searches) returns KAIMAU ELECTRONICS CO LTD, category ZPMV2, “Wiring, Printed – Component” (UL Product iQ record). That tells you which fabricator made the bare board. It does not tell you which device the board went into, what the circuit does or where to buy a replacement. One file can also cover several board constructions, and they do not all carry the same flame class, so a single E-number does not guarantee V-0 on its own.

5. Can You Use 94V-0 or the E-Number to Find a Replacement Board?

No. Millions of different boards from the same fabricator carry the same 94V-0 mark and E-number. Searches such as “94V-0 power supply” or “94V-0 LED replacement” return random results because the mark is shared across products.

To identify a replacement, use these instead:

• The model and rating label on the device housing.
• A board number or revision printed by the product designer (often near an edge or connector).
• Part numbers on the main ICs, transformers or the power controller.
• For LED drivers and power supplies, the input and output voltage and current printed on the module or its label.

If you only have the bare board, photograph both sides and search by the IC part numbers and the designer’s board number, not by 94V-0.

6. Does Board Thickness Change the Flame Rating?

Yes. A laminate is rated at specific thicknesses, and a thin version of the same material can earn a lower class than a thick one. UL’s Yellow Card (the certificate data sheet for a rated plastic) lists the flame class by minimum thickness. UL’s own Yellow Card guide uses an example where the same material is V-1 at 0.75 mm and V-0 at 1.0 mm and 3.0 mm. That example is a teaching card, not a PCB laminate, but the rule carries over: check the rating at your finished board thickness.

Is every FR-4 board automatically 94V-0?

No. FR-4 is a laminate grade, and “FR” stands for flame retardant, but the UL rating belongs to a specific laminate at a specific thickness, built by a specific fabricator. If you are moving to a thin board (under 1.0 mm, for example) or a halogen-free laminate, check the rating rather than assuming it. Our FR-4 material guide covers how Tg grades and laminate choice interact.

7. Does a 94V-0 Board Mean the Product Is UL Certified?

No. 94V-0 is a material flammability class, and the board itself is a UL Recognized Component. UL separates Recognized Components from certified end products: a recognized part comes with conditions of acceptability and is meant to be built into a product that is evaluated separately. UL 796 also states that the board is a component and the end product still needs its own investigation.

In practice, using a recognized 94V-0 board makes the end-product safety review simpler, because the board’s flammability does not have to be tested again. But the product still needs its own evaluation against the standard that applies to it.

8. How Can You Tell if a 94V-0 Circuit Board Is Bad?

Look first, then measure, then test under power. The test-equipment maker Huntron recommends this order:

1. Inspect under magnification for burned or swollen parts, cracked solder joints, scorch marks and lifted pads.
2. With the power off, measure for shorts across the supply rails and suspect parts with a multimeter (resistance) or a signature tester.
3. Only then power the board, ideally in a known-good assembly or on a test bench, and confirm the fault is gone after repair.

A board can look clean and still be faulty, so appearance alone does not prove it works. And a burn mark on the board does not mean the material failed its rating: V-0 limits how long the board keeps burning after the heat source is gone, not whether a failed component can scorch it.

9. What Should You Specify When Ordering 94V-0 Boards?

Put the flammability class, the finished thickness and the marking requirement in writing. “94V-0” alone on a drawing leaves the thickness and marking open.

Item to specify	What to write	Why
Flammability class	UL 94 V-0 for the finished board	Your end-product standard may require it
Finished thickness	For example, 1.6 mm ±10%	The rating applies at specific thicknesses
Laminate	Grade or brand, or “supplier to propose a V-0 laminate”	Lets you check the laminate’s Yellow Card
UL marking	Fabricator’s UL mark, E-number and 94V-0 on the board, with location	Proof for your safety reviewer
Halogen-free (if needed)	Halogen-free and V-0	Check that both apply to the same laminate
Evidence	UL file number and the matching construction	Lets you confirm it in Product iQ

How can we help with a 94V-0 order?

Send us the required flame class, finished thickness and any marking or halogen-free requirement with your Gerber files, and we will confirm the laminate and construction in the quote. We quote within 24 hours, have no minimum order quantity, and 2–4 layer FR-4 prototype boards are free. For a wider look at laminate options, see our PCB materials guide. See our PCB manufacturing overview for the certifications and build classes we work to.

Conclusion

94V-0 on a circuit board means the board construction passed the UL 94 vertical burn test at its strictest vertical class. The E-number next to it identifies the board fabricator in UL’s database. Neither one identifies the device or proves the finished product is certified. For repairs, use the device label and IC part numbers instead. For orders, specify the flame class at your finished thickness, the marking you need and the evidence you expect. Send your Gerber files, thickness and flammability requirement, and contact us today for a quote within 24 hours.

FAQ

Q1: What does UL 94 V-0 mean? It is the strictest of the three vertical flammability classes in UL 94. Each specimen must stop burning within 10 seconds after the flame is removed, and burning drips must not ignite cotton below it.

Q2: Is V-0 better than V-1? Yes, for flammability. V-0 allows up to 10 seconds of afterflame per specimen, V-1 allows 30, and both forbid drips that ignite the cotton.

Q3: Can I find a replacement board using the E-number on my PCB? No. The E-number identifies the company that made the bare board, and it appears on many unrelated products. Use the device label, the designer’s board number or the main IC part numbers instead.

Q4: Does a 94V-0 board mean my product is UL certified? No. The board is a recognized component with a material flammability class. The finished product still needs its own safety evaluation.

Q5: How much does one PCB cost? There is no single price; it depends on layer count, size, material, thickness and quantity. At QueenEMS, 2–4 layer FR-4 prototype boards are free, and we quote other builds within 24 hours.