How to look up a PCB supplier’s UL file number (E-number)

PCBVerified Editorial · Updated 2026-10-24

A UL file number, usually written as an E-number such as E350325, identifies a file that UL holds for a company. For printed circuit boards, that file leads to a list of recognized board constructions, each with its own limits. It does not tell you which factory will build your board. The lookup below takes a few minutes and turns a number in a sales email into a record you can compare with your order.

What the E-number on a PCB refers to

Bare boards are recognized as components in UL’s “Wiring, Printed - Component” category, code ZPMV2. Flexible constructions sit under ZPXK2. Laminates (QMTS2) and PWB coatings (QMJU2) are separate material categories, so a laminate supplier’s E-number says nothing about the board shop that uses the material.

One file number usually carries many type designations. Each designation is a defined construction, such as a single-layer board, a multilayer board or a metal-base board, with listed conductor, solder and temperature limits. When a supplier quotes “our UL number”, the useful follow-up is: which type designation covers this board?

Search UL’s printed wiring board database

UL iQ for Printed Wiring Boards at iq.ul.com/pwb is a free public search. It offers File Number, Company, Type/Material Dsg, Tradename and Country fields, plus a category filter. Enter the number exactly as supplied, including the E, and order the results by type designation.

Search by number first. The company field matches parts of names: on 24 October 2026, a company search for “aohong” returned Changzhou Aohong Electronics under E303981 and also a Jiangxi Zhaohong Kexin Circuit listing under a different file. Use the company search afterwards to look for other files held under related names.

Clicking a type designation opens its certificate page. The wider UL Product iQ database and the category guide text ask for a sign-in; the per-construction pages reached from the PWB search did not on the date of this review.

A worked example: E350325

Searching E350325 on 24 October 2026 returned 32 type designations listed to Camelot Electronics Technology Co., Ltd, China, all in ZPMV2. The JL-1 page showed:

• the holder’s address in the Yingfu Industrial Area, Anfeng Industrial Park, Qingyuan, Guangdong;
• the construction: multilayer printed wiring boards;
• a 0.10 mm minimum conductor width, and conductor thickness from 17 µm up to 68 µm on internal layers and 102 µm on external layers;
• solder limits of 288 °C for 20 seconds, a 130 °C maximum operating temperature, flame class V-0 and “All” under UL 796 DSR;
• a report date of 2011-12-03 and a last revision of 2016-08-17.

The Camelot manufacturer profile records production bases in Qingyuan, Anlu and Suining, with the Anlu operation run by a separate Hubei subsidiary. The JL-1 listing names the Qingyuan address. That is not a contradiction, but it frames the order question precisely: will this board be built at the listed Qingyuan site, and which JL designation covers its construction?

Match the record to your order

• Holder: the listed company should match the manufacturer on your purchase documents, or the supplier should explain the relationship in writing.
• Address: the listed address should be the plant that will build your boards, not only the group headquarters.
• Construction: the type designation should describe your board, for example multilayer rather than single-layer, or metal-base where you need an aluminium core.
• Limits: compare the listed minimum conductor width and maximum copper thickness with the finest feature and heaviest copper in your design. Compare the solder limits and maximum operating temperature with your assembly profile and the requirement set by your end-product standard.
• Marking: ask which type designation will be marked on delivered boards and where the marking will appear.

Group companies can hold separate files

A company search for “founder” on the same date returned E164671 for Zhuhai Founder Tech. Multilayer PCB Co Ltd and E315850 for Zhuhai Founder Tech High Density Electronic Co Ltd, among other results. The Founder F3 HDI profile concerns the high-density company. A group name on a brochure therefore does not identify the file; ask for the file number and the producing legal entity in the same reply.

What a matching record does not settle

A ZPMV2 listing covers the recognized constructions in that file. It does not confirm your specific stack-up, the laminate batch used for your order, or which process steps are subcontracted. Ask for the proposed process route alongside the UL reference, and record material requirements separately; the material traceability note covers that part.

If no listing appears, or the holder or address differs from the supplier’s documents, record the check as unresolved. Send one precise question naming the file number, the mismatch and the document that would resolve it.

How PCBVerified records UL numbers

A number found on a company website is shown as manufacturer reported. A stronger status needs a recorded comparison with UL’s database, with the date and the scope matched. Our note on why “Not independently checked” is shown explains how those labels are kept apart.