SST 6.3/5K Surface Mount Board Fuse - Equivalent & Substitute Parts

Part Overview

The SST 6.3/5K 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 equivalent and substitute parts necessary for ongoing design support and production continuity. The SST series has been superseded by the 0680L and 0680H series, which maintain identical electrical ratings and mechanical dimensions while offering active product status and improved availability.

Key Parameters

Parameter	Value
Current Rating	6.3 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Slow Blow
Package / Case	2-SMD, Square End Block
Mounting Type	Surface Mount
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 (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution for the SST 6.3/5K is determined by strict equivalence across the following 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)
Package / Case: 2-SMD, Square End Block (exact match required)
Mounting Type: Surface Mount (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)

All substitute parts listed below meet these criteria. Differences in Breaking Capacity, Melting I²t, DC Cold Resistance, and Approval Agency certifications do not affect functional substitution for standard applications but may influence selection based on specific circuit protection requirements.

Parameter Comparison

Part Number	Manufacturer	Series	Product Status	Current Rating (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Package	Breaking Capacity AC (A)	Breaking Capacity DC (A)	Melting I²t	DC Cold Resistance (Ω)	Approval Agency	Inventory (Pcs)
SST 6.3/5K	Bel Fuse Inc.	SST	Obsolete	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	—	62	0.012	AEC-Q200, CE, CSA, cULus	1,096
0680L6300-01	Bel Fuse	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	5,386
0680L6300-05	Bel Fuse	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	41,434
0680L6300-11	Bel Fuse	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	843
0680L6300-15	Bel Fuse	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	1,144
0680L6300-21	Bel Fuse Inc.	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	887
0680L6300-25	Bel Fuse	0680L	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	50	100	43	0.015	AEC-Q200, CE, cURus	792
0680H6300-01	Bel Fuse Inc.	0680H	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	100	500	32	0.023	cURus	1,100
0680H6300-05	Bel Fuse Inc.	0680H	Active	6.3	125	125	Slow Blow	2-SMD, Square End Block	100	500	32	0.023	cURus	4,526

Engineering Selection Recommendations

Direct Substitutes (0680L Series)

The 0680L6300-01, 0680L6300-05, 0680L6300-11, 0680L6300-15, 0680L6300-21, and 0680L6300-25 are direct functional equivalents to the SST 6.3/5K. All maintain identical electrical and mechanical specifications. The 0680L series carries Active product status and holds AEC-Q200 and CE certifications, matching the original part's compliance profile. The primary difference is packaging configuration (Tape & Reel), which is standard for active production parts. These parts are recommended as primary substitutes due to superior availability and active manufacturer support.

Parametric Equivalents (0680H Series)

The 0680H6300-01 and 0680H6300-05 are parametric equivalents that meet all core electrical and mechanical requirements. The 0680H series offers enhanced breaking capacity (100 A AC, 500 A DC versus 50 A AC) and lower melting I²t (32 versus 43), providing superior fault protection characteristics. These parts carry cURus certification. The 0680H series is suitable for applications requiring higher fault current withstand capability while maintaining identical current and voltage ratings.

Compliance Considerations

All substitute parts are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity ratings. The original SST 6.3/5K held CSA certification in addition to AEC-Q200 and CE; the 0680L series maintains AEC-Q200 and CE certifications. Applications requiring CSA certification should verify compliance requirements with the design authority before substitution.

Frequently Asked Questions (FAQ)

Q: Can the 0680L6300 series directly replace the SST 6.3/5K?

A: Yes. The 0680L6300 series maintains identical current rating (6.3 A), voltage ratings (125 V AC/DC), response time (Slow Blow), package type (2-SMD, Square End Block), and physical dimensions. All electrical and mechanical parameters required for substitution are equivalent.

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

A: Both series meet the core electrical specifications of the SST 6.3/5K. The 0680H series provides higher breaking capacity (100 A AC, 500 A DC versus 50 A AC, 100 A DC) and lower melting I²t (32 versus 43). Selection between series depends on circuit protection requirements and fault current withstand specifications.

Q: Does packaging format affect electrical performance?

A: No. The SST 6.3/5K and all substitute parts use identical 2-SMD, Square End Block package geometry and electrical characteristics. Packaging format (Tape & Reel for active parts) is a supply chain consideration only and does not affect circuit performance.

Q: Are there certification differences between substitute options?

A: The original SST 6.3/5K held AEC-Q200, CE, CSA, and cULus certifications. The 0680L series holds AEC-Q200, CE, and cURus certifications. The 0680H series holds cURus certification. Applications with specific certification requirements should verify compliance before substitution.

Q: Which substitute part offers the best availability?

A: The 0680L6300-05 offers the highest current inventory (41,434 pieces), followed by 0680L6300-01 (5,386 pieces) and 0680H6300-05 (4,526 pieces). All substitute parts carry Active product status with ongoing manufacturer support.

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