UL Certificates Explained

If you are developing a product with electronics in them, you will almost certainly need to get a UL certificate for all or part of the device. This article provides a brief explainer on the topic.

Underwriters Laboratories is an independent not-for-profit electronics testing organization, headquartered in the US. Established in 1894, it has grown in parallel with that of the electrical and electronics industries providing services to ensure products are safe to use. It's not the only safety certifier of electronics but it’s the dominant player in the market.


UL has a developed a range of standards for virtually every type of electronic product and the components that make them up. It provides testing services to ensure products comply with those standards and issues a range of marks that certify products and components.

Today, many key standards for electronic products call up UL standards. For example, IEC 62638 for IT Equipment and IEC 60601-1 for Medical Equipment both reference UL standards.


Primarily, UL is focused on key safety risks such as electrical shock and fire. The key UL standard most commonly referenced for the PCB bareboard design and manufacture is UL 796 covering standard PCBs and a range of related standards such as, UL 796F covering flex PCBs, UL 746E covering the laminates used in PCBs. UL 94 covers flammability requirements for all plastics and PCBs.


UL marks can be given for the complete finished product or for components/sub-assemblies. When, the manufacturer gain certification from UL, components critical to safety will be identified. The manufacturing process must then ensure that these components cannot be substituted and, where specified, have come with a UL certificate from the component supplier.


UL will periodically audit the manufacturer to ensure the correct processes are being followed. Typically, these audits will be once a quarter but the UL auditors can, and do, conduct unannounced spot checks.


For ordinary manufacturers, these audits and their unpredictable nature can be a real burden. Fortunately, it is not a problem at Circuitwise because our ISO 13485 medical device quality management system (QMS) automatically implements everything UL requires.


ISO 13485 QMS requires manufacturers have systems for full traceability of product manufacture, which happen to match exactly the UL requirements for any other kind of product, not just medical devices. For example, during goods inward inspection photographs are taken of the components showing the manufacturer and part number, recording the device provenance. Our system then logs whenever these components are used during a production run of a particular product. UL certificates are likewise stored in the system and all information is stored.


When products being introduced to our system require a UL certificate, the components identified as critical are all marked as such. Our system then takes care of all the requirements of UL automatically. So, if a UL auditor turns up unannounced it is never a problem as everything they require has been done automatically.