SST 6.3/1K Surface Mount Board Fuse - Equivalent & Substitute Parts

Part Overview

The SST 6.3/1K is a 6.3 A, 125 V AC/DC surface mount board fuse manufactured by Bel Fuse Inc. in a 2-SMD, Square End Block package. This part is classified as obsolete, making direct substitution necessary for new designs and production continuity. The fuse provides slow-blow response characteristics suitable for circuit protection in applications requiring 6.3 A current limiting at 125 V AC or DC operating conditions.

Key Parameters

Parameter	Value
Current Rating	6.3 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Slow Blow
Mounting Type	Surface Mount
Package / Case	2-SMD, Square End Block
Size / Dimension	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)
Operating Temperature	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution for SST 6.3/1K is determined by strict equivalence across the following critical parameters:

Current Rating: 6.3 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Surface Mount (exact match required)
Package / Case: 2-SMD, Square End Block (exact match required)
Physical Dimensions: 0.240" L x 0.100" W x 0.100" H (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)
RoHS Compliance: ROHS3 Compliant (exact match required)

Substitute parts are classified into two categories:

Direct Manufacturer Substitutes (0680L Series): Parts 0680L6300-01, 0680L6300-05, 0680L6300-11, 0680L6300-15, and 0680L6300-21 are active production alternatives from Bel Fuse Inc. These maintain identical electrical and mechanical specifications with the SST 6.3/1K while differing only in packaging configuration (Tape & Reel) and internal construction details (Melting I²t: 43 vs. 62).

Parametric Equivalents (0680H Series): Parts 0680H6300-01 and 0680H6300-05 are parametric equivalents that maintain the same current, voltage, and physical specifications but feature enhanced breaking capacity (100A AC, 500A DC vs. 50A) and lower melting I²t (32 vs. 62). These are suitable for applications requiring higher fault current withstand capability.

Parameter Comparison

Parameter	SST 6.3/1K	0680L6300-01	0680L6300-05	0680L6300-11	0680L6300-15	0680L6300-21	0680L6300-25	0680H6300-01	0680H6300-05
Current Rating (A)	6.3	6.3	6.3	6.3	6.3	6.3	6.3	6.3	6.3
Voltage Rating AC (V)	125	125	125	125	125	125	125	125	125
Voltage Rating DC (V)	125	125	125	125	125	125	125	125	125
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block
Size / Dimension	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Breaking Capacity @ Rated Voltage	50A	50A AC, 100A DC	50A AC, 100A DC	50A AC, 100A DC	50A AC, 100A DC	50A AC, 100A DC	50A AC, 100A DC	100A AC, 500A DC	100A AC, 500A DC
Melting I²t	62	43	43	43	43	43	43	32	32
DC Cold Resistance (Ohms)	0.012	0.015	0.015	0.015	0.015	0.015	0.015	0.023	0.023
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

For Direct Replacement (0680L Series): Parts 0680L6300-01, 0680L6300-05, 0680L6300-11, 0680L6300-15, 0680L6300-21, and 0680L6300-25 are recommended as primary substitutes for SST 6.3/1K. All are active production parts from Bel Fuse Inc. with ROHS3 compliance and AEC-Q200 or CE certification. These parts maintain identical electrical and mechanical specifications and are available in Tape & Reel packaging for production environments. The 0680L6300-05 variant offers the highest inventory availability (41,434 units in stock).

For Enhanced Fault Current Withstand (0680H Series): Parts 0680H6300-01 and 0680H6300-05 are parametric equivalents suitable for applications requiring higher breaking capacity (100A AC, 500A DC). These parts maintain the same current, voltage, and physical specifications as SST 6.3/1K but feature improved fault current handling. Selection of 0680H variants is appropriate when circuit protection requirements demand enhanced breaking capacity beyond the original 50A specification. Note that 0680H series carries cURus certification only, compared to the broader AEC-Q200, CE, cURus certifications of 0680L variants.

Packaging Consideration: SST 6.3/1K is supplied in bulk packaging, while all substitute parts are supplied in Tape & Reel format. This difference does not affect electrical or mechanical compatibility but may require adjustment to procurement and assembly processes.

Frequently Asked Questions (FAQ)

Q: Can 0680L6300 series parts directly replace SST 6.3/1K in existing designs?

A: Yes. The 0680L6300 series maintains identical current rating (6.3 A), voltage rating (125 V AC/DC), response time (Slow Blow), mounting type (Surface Mount), package type (2-SMD, Square End Block), and physical dimensions (0.240" L x 0.100" W x 0.100" H). All are ROHS3 compliant and operate across the same temperature range (-55°C ~ 125°C). Direct PCB-level substitution is supported without design modification.

Q: What is the difference between 0680L and 0680H series fuses?

A: Both series maintain identical current, voltage, and physical specifications. The primary differences are breaking capacity and melting I²t. The 0680L series provides 50A AC / 100A DC breaking capacity with 43 melting I²t, while the 0680H series provides 100A AC / 500A DC breaking capacity with 32 melting I²t. The 0680H series is suitable for applications requiring enhanced fault current withstand capability.

Q: Are there certification differences between substitute parts?

A: Yes. The 0680L6300 series carries AEC-Q200, CE, and cURus certifications. The 0680H6300 series carries cURus certification only. Selection should be based on application-specific certification requirements.

Q: Does the Tape & Reel packaging of substitute parts affect compatibility?

A: No. Tape & Reel packaging is a supply format difference only and does not affect electrical, mechanical, or thermal characteristics. The fuse component itself is identical to bulk-packaged variants. Assembly equipment compatibility with Tape & Reel format should be confirmed with manufacturing operations.

Q: Which substitute part offers the best inventory availability?

A: The 0680L6300-05 variant has the highest inventory availability at 41,434 units in stock, making it the optimal choice for high-volume production requirements.

Q: Can 0680H6300 parts be used in applications originally designed for SST 6.3/1K?

A: Yes. The 0680H6300 series is a parametric equivalent that maintains all critical electrical and mechanical specifications. The enhanced breaking capacity (100A AC, 500A DC vs. 50A) and lower melting I²t (32 vs. 62) provide improved fault current handling without affecting normal operation. Application-specific certification requirements should be confirmed before selection.

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