BK/EFF-5 Equivalent & Substitute Parts

Part Overview

The BK/EFF-5 is a 5 A 250 V AC/DC board mount fuse with fast blow response time, designed for through-hole radial mounting in vertical orientation. This component is classified as obsolete, necessitating identification of active equivalent parts for ongoing design support and procurement continuity. The fuse features a radial can package with 50 A breaking capacity and operates across a temperature range of -55°C to 125°C. Equivalent substitute parts maintain identical electrical ratings and mechanical compatibility while offering active product status and enhanced compliance certifications.

Substiute Parts

BK/EFF-5

Eaton - Electronics DivisionIn Stock: 860BK/EFF-5 Datasheet

Current PartRFQ

SR-5F-5A-BK

Eaton - Electronics DivisionIn Stock: 1039SR-5F-5A-BK Datasheet

SimilarRFQ

MRF 5-AMMO

Bel Fuse Inc.In Stock: 901MRF 5-AMMO Datasheet

DirectRFQ

MRF 5-BULK

Bel Fuse Inc.In Stock: 1606MRF 5-BULK Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the BK/EFF-5 is determined by strict equivalence across the following critical parameters: current rating (5 A), voltage rating (250 V AC), fuse type (board mount, cartridge style excluded), response time (fast blow), mounting configuration (through-hole radial vertical), breaking capacity (50 A), and physical dimensions (0.329" Dia x 0.303" H).

The identified substitute parts are grouped into two categories:

Category 1: Direct Dimensional and Electrical Equivalents Parts MRF 5-BULK and MRF 5-AMMO (Bel Fuse Inc., MRF series) maintain exact dimensional specifications (0.329" Dia x 0.303" H), identical DC cold resistance (0.01 Ohms), and matching melting I²t value (15). These parts are active products with comprehensive compliance certifications including AEC-Q200, CE, CSA, cULus, PSE, SEMKO, and VDE.

Category 2: Dimensional Variant with Equivalent Electrical Performance Part SR-5F-5A-BK (Eaton - Electronics Division, SR-5F series) maintains all critical electrical parameters but features slightly larger dimensions (0.335" Dia x 0.319" H). This part is active with cULus and PSE certifications. The dimensional variance requires verification of PCB layout compatibility during implementation.

All substitute parts maintain the 50 A breaking capacity, fast blow response characteristic, and through-hole radial mounting configuration required for direct functional replacement.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitutes: MRF 5-BULK and MRF 5-AMMO

The MRF 5-BULK and MRF 5-AMMO parts from Bel Fuse Inc. are the preferred substitutes for the obsolete BK/EFF-5. These parts maintain exact dimensional compatibility (0.329" Dia x 0.303" H), identical DC cold resistance (0.01 Ohms), and matching melting I²t characteristics (15). Both parts are active products with comprehensive compliance certifications including AEC-Q200, CE, CSA, cULus, PSE, SEMKO, and VDE. The MRF 5-BULK variant is packaged in bulk format, while MRF 5-AMMO is supplied in tape and box configuration. Selection between these two depends on procurement and assembly requirements rather than electrical or mechanical performance.

Secondary Substitute: SR-5F-5A-BK

The SR-5F-5A-BK from Eaton - Electronics Division serves as an alternative substitute when MRF series parts are unavailable. This part maintains all critical electrical parameters and is an active product with cULus and PSE certifications. However, the dimensional variance (0.335" Dia x 0.319" H versus 0.329" Dia x 0.303" H) and elevated DC cold resistance (0.018 Ohms versus 0.01 Ohms) require PCB layout verification prior to implementation. The operating temperature range is also reduced to -40°C ~ 125°C compared to the -55°C ~ 125°C of the primary substitutes.

Compliance Considerations

All substitute parts maintain the 50 A breaking capacity and fast blow response time required for circuit protection. The MRF series parts offer the broadest compliance profile, including automotive-grade AEC-Q200 certification. Selection should prioritize parts meeting the specific regulatory requirements of the target application.

Frequently Asked Questions (FAQ)

Q: Can MRF 5-BULK and MRF 5-AMMO be used interchangeably with BK/EFF-5?

A: Yes. Both MRF parts maintain identical electrical ratings (5 A, 250 V AC), response time (fast blow), breaking capacity (50 A), and physical dimensions (0.329" Dia x 0.303" H). The difference between these two is packaging format only: MRF 5-BULK is supplied in bulk packaging, while MRF 5-AMMO is supplied in tape and box format. Selection depends on assembly process requirements.

Q: What is the significance of the dimensional difference in SR-5F-5A-BK?

A: The SR-5F-5A-BK has slightly larger dimensions (0.335" Dia x 0.319" H) compared to the BK/EFF-5 (0.329" Dia x 0.303" H). While the difference is minimal, PCB layout verification is required to confirm that the larger diameter and height do not create clearance conflicts with adjacent components or board features. The elevated DC cold resistance (0.018 Ohms versus 0.01 Ohms) may also affect circuit performance in applications with tight resistance tolerances.

Q: Are all substitute parts RoHS compliant?

A: Yes. MRF 5-BULK, MRF 5-AMMO, and SR-5F-5A-BK are all ROHS3 compliant. The original BK/EFF-5 RoHS status was not specified in the available documentation.

Q: Which substitute part has the broadest compliance certifications?

A: The MRF 5-BULK and MRF 5-AMMO parts from Bel Fuse Inc. carry the most comprehensive certification profile, including AEC-Q200 (automotive), CE, CSA, cULus, PSE, SEMKO, and VDE. These certifications make the MRF series suitable for automotive, industrial, and consumer applications requiring multiple regulatory approvals.

Q: What is the difference in melting I²t between the substitute parts?

A: The MRF 5-BULK and MRF 5-AMMO have a melting I²t of 15, while SR-5F-5A-BK has a melting I²t of 55. The original BK/EFF-5 has a melting I²t of 16. The melting I²t value characterizes the thermal energy required to melt the fuse element. The MRF series parts more closely match the original BK/EFF-5 characteristic, while the SR-5F-5A-BK exhibits significantly different thermal behavior. This difference may affect circuit protection response in applications with specific I²t requirements.

Q: Can SR-5F-5A-BK be used in applications requiring -55°C operation?

A: No. The SR-5F-5A-BK has an operating temperature range of -40°C ~ 125°C, which does not extend to -55°C. Applications requiring operation at -55°C must use either MRF 5-BULK or MRF 5-AMMO, both of which support the full -55°C ~ 125°C temperature range.

Q: Are there any inventory considerations for selecting a substitute?

A: Yes. Current inventory levels are: BK/EFF-5 (808 pcs), SR-5F-5A-BK (1028 pcs), MRF 5-AMMO (877 pcs), and MRF 5-BULK (1569 pcs). MRF 5-BULK has the highest available inventory. However, inventory levels are subject to change and should be verified at the time of procurement.