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THERMOFUSES

SCHOTT is a leading international technology group in the areas of specialty glass and glass-ceramics. With more than 130 years of outstanding development, materials and technology expertise we offer a broad portfolio of high-quality products and intelligent solutions that contribute to our customers’ success.
For several decades, SCHOTT has been a leading developer and manufacturer of thermal links. These safety devices serve a broad range of applications, including home appliances, li-ion batteries and automobiles. With many years of extensive experience and a strong development and manufacturing set-up, we can respond flexibly to market needs and customer requirements.
 
Contents

Introduction, Advantages, Safety standards Design
Applications
Standard Ratings
Performance Data
Definition of Terms
Lead Cutting and Taping
Cautions
 

Introduction

SCHOTT develops and manufactures thermal link protection devices, widely known as SEFUSE®. These devices are designed to protect industrial and home electrical equipment from catching fire by sensing overheating and cutting off the electrical circuit immediately.
There are two SEFUSE® types: SF and SM. Both types suit the needs of a wide range of applications. The SF-type uses thermosensitive material as the thermal pellet, while the SM-type uses a fusible alloy.

SCHOTT SEFUSE® Advantages:

Trusted: For many decades, SEFUSE® has been one of the most renowned a trusted brands of thermal links worldwide.

Safe & Reliable: SCHOTT SEFUSE® thermal links are highly reliable thermal protection devices that provide excellent, long-lasting performance and meet numerous international industrial safety standards, such as UL, VDE, CCC, PSE, etc. SEFUSE® SF-type fuses, except SF/K series, have a ceramic pipe that alleviates stress that may occur on the sealing resin when the leads are bent, thereby reliably holding the leads in place.

Eco-friendly: SEFUSE® thermal links contain no hazardous substances and comply with WEEE and RoHS standards. In addition, the sliding contact of SEFUSE® SF-type thermal links are made of an environmentally-friendly silver copper oxide (AgCuO) material that is patented worldwide.

 
Safety standards
 
Design
SF-Type
Serie: SF/R, SFH/R, SF/K, SF/Y
 

The thermal pellet placed inside the metal case of the SF-type responds to an abnormal temperature situation and triggers the cutoff function. The SF-type features a large rated current of 6A to 15A (AC). Furthermore, the SFH/R series has higher Tm than conventional thermal links, as well as excellent insulation performance at high temperature conditions.
 
Before operation
 
The SF-type contains a sliding contact, springs and a thermal pellet inside a metal case. When spring B is compressed, there is firm contact between lead A and the sliding contact. At normal temperatures, current flows from lead A to the sliding contact and then through the metal case to lead B.

*Not used in SF/K series.

 

After operation
 
When the ambient temperature rises to the operating temperature of the SF-type, heat is transferred through the metal case and melts the thermal pellet. Springs A and B then stretch and the sliding contact moves away from lead A, thereby opening the electrical circuit.

SM-Type
   
Series: SM/A, SM/B, SM/G
 

 
The SM-type uses a fusible alloy inside a ceramic case. As ceramic is an insulator, the SM-type can be fixed directly where temperature detection is required. The SM-type has a rated current of 0.5A to 2.0A (AC) / 3.0A to 7.0A (DC).
 
Before operation
 
The leads of the SM-type are connected by a fusible alloy thereby allowing the current to flow directly from one lead to the other. The fusible alloy is coated with a special flux.
 
After operation
 
When the ambient temperature rises to the operating temperature of the SM-type, the fusible alloy melts and forms a drop around the end of each lead due to the surface tension and the special flux coating. Without a direct contact between the leads, the electrical circuit is opened.

Applications

 

Small home appliances
Coffee makers, electric kettles, bread makers, rice cookers, hot plates, irons, hair dryers

*SF-type, SM-type

Large home appliances
Airconditioners, refrigerators, washing machines, fan heaters, electrical toilets, gas boilers, electrical tables with heaters

*SF-type, SM-type

Automotive
Automotive air conditioners, seat heaters, engine coolings

*SF-type

Office equipment
Airconditioners, refrigerators, washing machines, fan heaters, electrical toilets, gas boilers, electrical tables with heaters

*SF-type

Standard Ratings
SF/R series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 
click to enlarge

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (191 substances, 27th June, 2018).
  2. For standard lead length type, add the suffix "0" at the end of the part number.
    For long lead length type, add the suffix "1" at the end of the part number.
  3. Th is the maximum temperature measured on the thermal cutoff when it continues to conduct a rated current without changing its state of conductivity for 168 hours.
  4. The electrical ratings according to the various safety standards are shown in the following table.

    Rated Voltage
    UL/cUL
    VDE
    CCC
    KTL
    PSE 6)
    AC120V
    20A (Resistive)
    -
    -
    -
    -
    AC250V
    10A (Resistive)
    10A
    10A
    10A
    10A
    15A (Resistive)
    15A
    15A
    15A
    15A
    16A (Resistive)
    -
    -
    -
    -

  5. The following SF-types have passed the Conductive Heat Aging Test (CHAT) specified by the UL safety standard: SF184R*, SF188*, SF214*, SF229R*, and SF240R*.
  6. With respect to the PSE standard, SF/R is separately available for 10A and 15A ratings. Please select the appropriate product rating according to the specifications of the final application.
  7. In case of requests for 10A rated current thermal links, please add "J1" after the part number (name). i.e. SF***R0 J1.

Standard Ratings
SFH/R series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 
click to enlarge

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (191 substances, 27th June, 2018).
  2. For standard lead length type, add the suffix "0" at the end of the part number.
    For long lead length type, add the suffix "1" at the end of the part number.
  3. Th is the maximum temperature measured on the thermal cutoff when it continues to conduct a rated current without changing its state of conductivity for 168 hours.
  4. The electrical ratings according to the various safety standards are shown in the following table.

    Rated Voltage
    UL/cUL
    VDE
    CCC
    KTL
    PSE 6)
    AC120V
    20A (Resistive)
    -
    -
    -
    -
    AC250V
    10A (Resistive)
    10A
    10A
    10A
    10A
    15A (Resistive)
    15A
    15A
    15A
    15A
    16A (Resistive)
    -
    -
    -
    -

  5. The following SF-types have passed the Conductive Heat Aging Test (CHAT) specified by the UL safety standard: SFH172R*.
  6. With respect to the PSE standard, SF/R is separately available for 10A and 15A ratings. Please select the appropriate product rating according to the specifications of the final application.
  7. In case of requests for 10A rated current thermal links, please add "J1" after the part number (name). i.e. SF***R0 J1.

Standard Ratings
SF/K series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 
click to enlarge
*Factory Code represents the factory location as shown next Thailand : C

Standard Ratings
SF/Y series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (144 substances, 20 June 2013).
  2. h is the maximum temperature measured on the thermal link when it continues to conduct a rated current without changing its state of conductivity for 168 hours.
  3. The following electrical ratings were used for the UL, VDE, and KTL safety standards: 10A (Resistive)/AC 250V.
  4. The following SF-types have passed the Conductive Heat Aging Test (CHAT) specified by the UL safety standard: SF188K and SF214K.
  5. Pending approval.
click to enlarge
  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (191 substances, 27th June, 2018).
  2. Part number indicates thermal links with standard lead lengths. For long lead length types, add the suffix "-1" at the end of the part number.
  3. 2004010205122568
  4. Pending approval.

Standard Ratings
SM/A series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 
Standard Ratings
SM/B series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 

Standard Ratings
SM/G series
Dimension (Unit: mm)
Note: The dimensions for long lead devices are in parentheses.
 
 
 

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (191 substances, 27th June, 2018).
  2. For standard lead length type, add the suffix "0" at the end of the part number. For long lead length type, add the suffix "1" at the end of the part number.
  3. DC ratings are approved by UL and VDE.
  4. SM072A* has c-UL recognition.

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (191 substances, 27th June, 2018).
  2. For standard lead length type, add the suffix "0" at the end of the part number. For long lead length type, add the suffix "1" at the end of the part number.
  3. DC ratings are approved by UL and VDE.
 

Note

  1. No use of hazardous substances prescribed by WEEE and RoHS.
    All products do not use SVHC prescribed by REACH (144 substances, 20 June 2013).
  2. For standard lead length type, add the suffix "0" at the end of the part number.
    For long lead length type, add the suffix "1" at the end of the part number.
  3. DC ratings are approved by UL and VDE.
Performance Data
SF/R series ∙ SFH/R series ∙ SF/K series ∙ SF/Y series
click to enlarge
 
 
Temperature Rise
 
Response Time
 
click to enlarge
 
Performance Data
SM/A series ∙ SM/B series ∙ SM/G series
click to enlarge
Internal resistance and initial operating temperature
 
Internal resistance and initial operating temperature
 
Internal resistance and initial operating temperature

SM/A series
 

SM/B series
 

SM/G series
 
 
Definition of Terms
Rated functioning temperature is the operating temperature of the thermal link, measured using the method specified in the safety standard. As stated in the Electrical Appliance and Material Safety Law (PSE) of Japan (Appendix 3, Section 3), the thermal links should operate within ±7°C of the specified operating temperature. In cases where Tf is greater than 200°C, the thermal links should operate within ±10°C of the specified operating temperature. In standards that comply with the IEC standard, it is indicated that the thermal links should operate within +0/-10°C of the specified temperature range.

Operating Temperature

Operating temperature and tolerance refers to the operating temperature range measured by the following conditions. A thermal link test sample is placed in the condition where the temperature of a thermostatic oven is raised until 12°C below the rated functioning temperature of the test sample at optionally increasing speed. Then the temperature of the thermostatic oven is raised at the rate of 0.5-1.0°C a minute. At this time, the electric current flowing through the test sample for opening confirmation shall be less than 10mA. Furthermore, the distance between a measuring point and a test sample shall be less than 20 mm.

Th (Holding Temperature)
Th is the maximum temperature measured on the thermal links when it continues to conduct a rated current without changing its state of conductivity for 168 hours.

Tm (Maximum Temperature Limit)
Maximum temperature limit is the maximum temperature for which conductivity does not occur again during the following test. First, the samples are maintained at Tm for a period of 10 minutes. Then, the withstand voltage test is conducted for 2 minutes with twice the rated voltage. During the test, the thermal links must remain in the functioned state, i.e. open. Hence, no current is allowed to pass through. (Functioned state of the SF-type: not less than 0.2MΩ; SM-type: not less than 2MΩ (between body and lead) and not less than 0.2MΩ (between lead and lead)
 
Lead Cutting and Taping
 
Lead cutting and taping services are available upon request for the following types.
 
Taping
 
 
Lead Cutting
 
Lead Forming (SF/R, SFH/R)
Packing Quantity
Cautions
This section describes points to note, about the design, installation and storage of SEFUSE® thermal links, so as to achieve the optimum performance of these thermal protection devices.
 
For optimal thermal link performance, it is recommended that customers correctly store the thermal protection devices, design appropriate circuits for the appliances and perform evaluations, mounting and testing steps as necessary. Problems arising from the inappropriate execution of the above would be the sole responsibility of the customer, and SCHOTT declines any and all responsibility.
 
Design  
Do not use this device for any purpose other than as a thermal link.
The thermal link is designed to detect abnormal rises in temperature and open the electrical circuits as required. It is not a current fuse that cuts off excess current. If the thermal link is used as a current fuse, it may malfunction.
Do not use this device in aerospace equipment, aeronautical equipment, nuclear reactor control systems, life support equipment or systems, transportation machinery engine control or safety-related equipment.
This device is designed for use in household electrical appliances, office automation equipment, audio and video equipment, computer communications equipment, test and measurement equipment, personal electronic equipment and transportation equipment (excluding engine control).

Decisions regarding the type of thermal link, the installation location and the mounting method should be made by the customers, based upon the requirements of the final application.
It is recommended that designers test the final design with the selected thermal link under both normal conditions as well as predicted worst-case scenarios.

  ▼Thermal links should be mounted where it can detect abnormal heat as quickly as possible.
  The thermal link operates when the thermal element within melts. Therefore, if the thermal element does not reach the operating temperature, the cutoff will not activate even if the ambient temperature has risen to the operating temperature. In addition, a short lag time might result in the event of a sudden rise in the ambient temperature or if the thermal link only detects part of the temperature increase.
  ▼Thermal links* should be mounted such that the temperature gradient is equal throughout the thermal link.
  If lead B of the SF-type, which is caulked to the metal case, is mounted in such a way that it only conducts heat to the metal case, the temperature around the thermal pellet would always be higher than other parts in the metal case. This could lead to the thermal link opening prematurely. Hence, it is recommended that lead A, which is the resin-sealed side, be connected nearer to the heat source. It should also be mentioned that similarly, if lead A is fixed in a location where the temperature it is exposed to is always lower than that of lead B, the thermal link could also be prematurely triggered.
  ▼Cautions about Tm
  Please ensure that the design of the final application does not exceed Tm (the maximum temperature limit) of the thermal link. If used in conditions beyond the rated temperature, a dielectric breakdown could result and the thermal link could re- conduct even after opening.
  ▼Cautions about Th (SF-type)
  Continuous exposure to temperatures close to the Th temperature of the thermal link could result in the thermal pellet reducing in size over time, thereby shortening the lifespan of the thermal link. This change in the pellet size is irreversible. Hence, it is important that designers select and test thermal links suitable for the temperature zone of the final application, based on the temperature recommendations in Table 1. Please also note that the Th temperature test is a one-time test, not a cycle test, conducted continuously for 168 hours.
Designers of the final application should take into account the maximum surface temperature of the thermal link as shown in Table 1, and avoid exceeding this level.
If the body temperature of the thermal link is exceeded on a regular basis, the thermal link may start opening at temperatures lower than the normal operating temperature. Malfunctions may also occur. In case of using SM-type in DC rating, please kindly contact SCHOTT.
 
Table 1 Recommended usage temperatures
Note that the temperature listed in Table 1 refers to the surface temperature of the thermal link, not the ambient temperature.
 
Thermal links have a limited life.
The thermal elements used are durable substances designed for long-term use. However, the longevity of the thermal link depends on the conditions in which it is exposed to. This is particularly true if the thermal protection device is frequently exposed to temperatures very close to its operating temperature. Hence, it is recommended that designers conduct a reliability test by fixing the thermal protection device onto the actual application and simulating the expected operating conditions to assess the lifetime of the device.
 
The body temperature of the thermal link increases as current passes through it.
The body temperature of the thermal link could rise to levels higher than the ambient temperature current passes through the device. In addition, the body temperature could also increase depending on a number of factors such as the mounting method. Hence, it is recommended that designers measure the body temperature of the thermal link after conducting a reliability test.
 
Use the thermal link with a voltage and current level lower than the rated level.
If the thermal link is used with a voltage or current level higher than the rated level, the contacts may be welded together in the SF-type, causing the thermal link to malfunction. In the SM-type, the body of the thermal link may rupture.
 

Do not use the thermal link in an atmosphere out of the standard specifications such as in environments exposed to sulfurous acid gas, nitrogen oxide gas, ammonia gas or conditions that contain formic acid. It is also not suitable for high humidity situations and submersion in a liquid.
The case of the thermal link* is made with a copper alloy. Hence, installing the thermal link in such conditions or similar, could deteriorate the sealing resin or lead to cracks in the case of the thermal link due to corrosion. The thermal link could thus operate at lower than operating temperatures or not activate even if its operating temperature is exceeded.

*SF-K series only

 
The thermal link corresponds to industrial waste.
The thermal link corresponds to industrial waste, and requires disposal according to governmental and provincial regulations. The services of a licensed disposal contractor could also be engaged.
 
The thermal link is a non-repairable device.
In case of replacement, an equivalent thermal link from the same manufacturer should be used. For general consumers who are not aware of the cautions associated with the thermal link, they should be informed not to mount, remove or replace the thermal link through a note to this effect in the user's manual and other related materials.
 
Lead wire process
When bending the lead wire, it is important not to apply excessive pressure to the root of the lead wire. The lead wire should be secured close to the case and bent (not twisted) at a distance 3 mm or more from the body of the fuse.
The tensile strength applied to the lead wire should be 49N or less for SF-type and 9.8N or less for SM-types.
The strength applied to the body of the thermal link should be 98N or less for SF-type, 49N or less for SM-type.
With regards to the SF-type, deformation of the case may change the location of the sliding contact during operation and could lead to the thermal link operating only at temperatures lower than the normal operating temperature range. The thermal link may also not operate even if the thermal link's operating temperature is exceeded.
 
Mounting
Thermal links can be mounted by soldering, caulking or welding.
The connecting position should be 5 mm or more from the body of the thermal links.
If soldering, take note that the thermal link may function because of excessive solder temperature. To prevent such malfunctions, for example, holding the lead near the case with a tool is effective for allowing the heat to escape and the soldering should be done in short intervals.
Another effective method is to use a lower solder temperature and to solder at a location that is at a distance from the case.
 
If caulking or welding, be careful to keep the resistance value of the connecting section low. If the connecting section has a high resistance value, the passing current may generate an abnormally high temperature that will cause the thermal link to operate. If caulking particularly, please test many times because heat-cycle and humidity cause a high resistant value.
 
After mounting the thermal link, be careful not to apply force that may pull, push or twist the lead wires.
 
If using a SF-type thermal link, the lead on the resin-sealed side must not be allowed to touch the case. This would cause the current to flow from the lead on the resin-sealed side to the opposite lead resulting in a non-functioning thermal link.
 
 
Note that the body of the SF-type is the same in potential as the circuit. Therefore, it must be electrically isolated from other metallic parts.
 
Storage

The body and lead A of the SF-type, and the leads of SM092A, SM092B, SM225A, SM225B and SM225G are silver-plated. Therefore, these parts may discolor because of sulfuration, making the markings on the body illegible or negatively affecting the solder-ability of the lead. To avoid this, the thermal link should not be kept around materials (such as cardboard or rubber, etc.) which generate sulfurous acid gas.

When storage in cardboard boxes is required, thermal links should be double packed and sealed in polybags such as polyethylene.

 
Recommendation
SCHOTT recommends the following tests upon receipt and after mounting of the thermal link, as it may have undergone some mechanical load or thermal influence during transportation or when being mounted.
  1. Appearance check
  2. Resistance check (comparing before with after), or conductive check
  3. X-ray inspection
  4. Operation check for sampling
Be careful when mounting the thermal link because external force, heat or a harmful atmosphere (containing excessive humidity or sulfurous acid gas) may damage the thermal link.
If applicable, it is recommended that the general consumers, who are unaware of the usage cautions for thermal links, be informed not to mount, remove, or replace the thermal link through a note to this effect in the user's manual and other related material.
All reasonable care has been taken to present the data here and the values contained in this document were obtained under certain testing conditions by us. They are not guaranteed and are for reference only. For any clarifications or more information about these cautions, please kindly contact SCHOTT.
 
The information herein is based on the documents as of August 2018, and is subject to change without notice. Therefore it is recommended to refer to latest individual information such as drawing for mass production designing. The latest product information will also be made available on www.schott.com/epackaging for your reference.

AllIt is prohibited to reprint or copy the contents herein without prior written agreement from SCHOTT Japan Corporation.

Please note that should any problems relevant to the industrial property of third parties occur with the use of products from SCHOTT Japan Corporation, the company would not assume any responsibility for matters other than the ones directly related to the structure or the manufacturing process of the products supplied by SCHOTT Japan Corporation.

Although continuous efforts to improve the quality and reliability of our products are in place, the possibility of defects cannot be entirely eliminated. Therefore when using our electronic component products, please ensure that sufficient safety measures are included in the design of the final application, such as redundancy, fire containment and malfunction prevention against physical injuries, fire disasters and social damages in consideration of the said defect occurrences.

Our products are classified into 2 groups: “Standard” and “Special”. The recommended applications of the products according to its quality level are indicated below. If you intend to use our products for applications other than “Standard” level, please consult with our sales representative in advance.

"Standard"

Computers, office equipment, communication equipment, measuring equipment, audio & visual equipment, home electric appliances, machine tools, personal electrical equipment and industrial robots, etc.

"Special"

Transportation equipment (automobiles, trains, ships and others), aircrafts, aerospace equipment, medical equipment for life support, etc.



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