Product Description

The SCHOTT SEFUSE® SM type is a thermal link designed to protect electrical home appliances and industrial electrical equipment from catching fire. It contains a fusible alloy inside an insulated case which interrupts the electrical circuit by melting when ambient temperatures reaches abnormal levels.

SF type

The device is integrated into the electrical circuit of the appliance. Two leads are connected in the device by a fusible alloy, which is coated with a special flux. Under normal conditions, the current flows directly from one lead to the other through the fusible alloy. In case the ambient temperature should reach a critical point, the fusible alloy will melt and then condense into a drop around the end of each lead caused by surface tension and the special coating. As a result, the electric current is interrupted immediately.


SM type thermal cutoffs:
  • Are stable and operate with precision to ensure maximum safety for the operation of electrical equipment
  • Can be mounted directly where temperature detection is required without insulation
  • Have fast thermal response due to their shape and small size
  • Have a resin-seal which ensures strong reliability and accuracy


The SM type is used in many different electrical products, such as in power supplies, motors, battery packs and automobiles.

Technical Details


The SM type is a one-shot operation device that uses a fusible alloy as thermal element inside an insulated ceramic case. The alloy is coated with a special flux.

For additional information about this technology, please click on the thermal cutoff technology page.

Features/ Specifications

All versions of the SM type use a fusible alloy as a thermal element and cover a range of operating temperatures from 76°C to 151°C. All types are especially environmentally-friendly, complying with the Directive on Waste Electrical and Electronic Equipment Directive (WEEE), and the Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS).
Series Electrical Ratings Opening Temperature Standard
AC/DC Current Voltage
SM-G Series AC 0.5A 250V 115°C-151°C UL, CSA, VDE, BEAB, CCC, PSE
SM-B Series AC 1A 250V 97°C-151°C UL, CSA, VDE, BEAB, CCC, KTL, PSE
DC 3.5A-6A 50V UL, VDE
SM-A Series AC 2A 250V 76°C~151°C UL, CSA, VDE, BEAB, CCC, KTL, PSE
DC 3A-7A 50V UL, VDE
About CCC Self-Declaration number

Due to the publication of new implementation rules from the Certification and Accreditation Administration of the People’s Republic of China (CNCA), the authentication method of thermal links was changed to CCC Self-Declaration (Index No. 2019-1571296947171 / Document No. 2019 No.44). SCHOTT SEFUSE® thermal links that had acquired CCC certification have completed the conversion to the CCC Self-Declaration accordingly.
For more details, please refer to the “Announcement for CCC Self-Declaration number”.

Forms of Supply and Product Packaging

Lead cutting and tapping services are available upon request. For further information, please download the file 'Lead Cutting and Taping' below.
Standard forms of supply are available. Please contact our sales department if you have any special requests concerning supply and packaging.

Please refer to "Cautions" in the Thermal Cutoff catalog for our design guidelines.


The SM type is a reliable thermal protection device manufactured in a location certified by the International Standards Organization (ISO9001/14001 quality standard).

All SM type thermal cutoffs undergo an automatic internal resistance check, in addition to the standard quality assurance processes of SCHOTT to ensure the consistent high quality of the product.

For further information, please review our quality assurance page. The Thermal Cutoff catalogs are also available from our download page.
무역박람회 & 이벤트
Trade fair CIOE - China International Optoelectronic Exposition, Shenzhen, 中国, 01.09 - 03.09.2021
Trade fair Compamed, Düsseldorf, Deutschland, 15.11 - 18.11.2021
Trade fair SPIE Photonics West, San Francisco, United States, 25.01 - 27.01.2022
SCHOTT Korea Co., Ltd.
Seoul 8F. Samseong-Building, 623 Teheran-ro, Gangnam-gu
E-Mail to SCHOTT+82 2 3456 0328+82 10 2419 7143