BZX55F18-TAP Equivalent & Substitute Parts

Part Overview

The BZX55F18-TAP is a Zener diode rated at 18 V nominal with 500 mW power dissipation in a through-hole DO-35 package. Manufactured by Vishay General Semiconductor - Diodes Division, this component is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for ongoing design support, production continuity, and component sourcing.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	18 V
Tolerance	±1%
Power - Max	500 mW
Impedance (Max)	50 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 13 V
Voltage - Forward (Vf) (Max) @ If	1.5 V @ 200 mA
Operating Temperature	175°C
Mounting Type	Through Hole
Package / Case	DO-204AH, DO-35, Axial
Grade	Automotive
Qualification	AEC-Q101
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the BZX55F18-TAP is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 18 V nominal
Power rating: 500 mW maximum
Package type: DO-35 through-hole
Mounting configuration: Axial leads

Secondary Compatibility Factors:

Voltage tolerance (±1% to ±10%)
Impedance characteristics (21 to 105 Ohms)
Reverse leakage current specifications
Forward voltage characteristics
Operating temperature range
RoHS and automotive compliance status

Substitute parts are grouped into two categories: direct equivalents from Vishay (maintaining ±1% tolerance and automotive qualification) and functional alternatives from Microchip Technology (with varying tolerance grades and compliance profiles).

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Vf (Max) @ If	Operating Temp	Product Status	RoHS Status	AEC-Q101
BZX55F18-TAP	Vishay	18 V	±1%	500 mW	50 Ohms	1.5 V @ 200 mA	175°C	Obsolete	ROHS3 Compliant	Yes
BZX55B18-TAP	Vishay	18 V	±2%	500 mW	50 Ohms	1.5 V @ 200 mA	-65°C ~ 175°C	Active	ROHS3 Compliant	Yes
1N5742C	Microchip	18 V	±1%	500 mW	45 Ohms	900 mV @ 10 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N5742D	Microchip	18 V	±1%	500 mW	45 Ohms	900 mV @ 10 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N5248B	Microchip	18 V	±5%	500 mW	21 Ohms	1.5 V @ 200 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N5538B	Microchip	18 V	±5%	500 mW	105 Ohms	1.1 V @ 200 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N6006A	Microchip	18 V	±10%	500 mW	55 Ohms	1.1 V @ 200 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N6006B	Microchip	18 V	±5%	500 mW	42 Ohms	1.1 V @ 200 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No
1N6006C	Microchip	18 V	±2%	500 mW	42 Ohms	1.1 V @ 200 mA	-65°C ~ 175°C	Active	RoHS non-compliant	No

Engineering Selection Recommendations

Primary Recommendation: BZX55B18-TAP

The BZX55B18-TAP is the preferred direct substitute for the obsolete BZX55F18-TAP. Both components are manufactured by Vishay General Semiconductor - Diodes Division and share identical electrical specifications with the exception of voltage tolerance (±2% versus ±1%) and operating temperature range extension (-65°C to 175°C versus 175°C maximum). The BZX55B18-TAP maintains ROHS3 compliance and AEC-Q101 automotive qualification, ensuring compatibility with automotive-grade applications. This part is in active production with substantial inventory availability (34,466 units).

Secondary Recommendations: 1N6006C and 1N5742C

For applications where RoHS compliance is not a requirement, the 1N6006C (Microchip Technology) provides a ±2% tolerance match with the original part and maintains the 18 V / 500 mW specification. The 1N5742C offers ±1% tolerance matching but with slightly lower impedance (45 Ohms versus 50 Ohms). Both are in active production.

Alternative Options: 1N5248B, 1N5538B, 1N6006A, 1N6006B

These parts satisfy the core 18 V / 500 mW requirements but with relaxed tolerance specifications (±5% to ±10%). Selection among these alternatives depends on circuit tolerance requirements and impedance sensitivity. All are in active production with adequate inventory.

Compliance Considerations:

The BZX55B18-TAP is the only substitute maintaining both ROHS3 compliance and AEC-Q101 automotive qualification. All Microchip alternatives are RoHS non-compliant and lack AEC-Q101 certification. For automotive applications requiring regulatory compliance, the BZX55B18-TAP is the mandatory choice.

Frequently Asked Questions (FAQ)

Q: Can the BZX55B18-TAP directly replace the BZX55F18-TAP?

A: Yes. Both parts share identical 18 V nominal voltage, 500 mW power rating, and DO-35 package configuration. The BZX55B18-TAP has a relaxed tolerance specification (±2% versus ±1%) and an extended operating temperature range (-65°C to 175°C versus 175°C maximum). For applications where the original ±1% tolerance is critical, circuit performance must be evaluated against the ±2% specification of the substitute.

Q: What is the difference between the Vishay and Microchip substitute options?

A: Vishay's BZX55B18-TAP maintains automotive-grade qualification (AEC-Q101) and ROHS3 compliance. Microchip's alternatives (1N5742C, 1N5742D, 1N5248B, 1N5538B, 1N6006A, 1N6006B, 1N6006C) are RoHS non-compliant and lack automotive certification. Selection depends on application requirements for regulatory compliance and automotive qualification.

Q: Are all substitute parts available in the same DO-35 package?

A: Yes. All listed substitute parts are specified for DO-35 through-hole package configuration with axial leads, ensuring mechanical and electrical compatibility with the original BZX55F18-TAP footprint.

Q: How do impedance differences affect circuit performance?

A: Impedance (Zzt) values range from 21 Ohms (1N5248B) to 105 Ohms (1N5538B) across the substitute options. The original BZX55F18-TAP specifies 50 Ohms. Impedance affects transient response and noise filtering characteristics. For applications sensitive to impedance performance, the BZX55B18-TAP (50 Ohms) or 1N6006B/1N6006C (42 Ohms) provide closer matching to the original specification.

Q: Which substitute is recommended for new automotive designs?

A: The BZX55B18-TAP is the only substitute maintaining AEC-Q101 automotive qualification and ROHS3 compliance. This part is the required choice for automotive applications subject to regulatory and quality standards.

Q: What is the inventory status of recommended substitutes?

A: BZX55B18-TAP: 34,466 units in stock. 1N6006C: 987 units. 1N5742C: 831 units. 1N5742D: 727 units. 1N5248B: 62,638 units. 1N5538B: 979 units. 1N6006A: 1,078 units. 1N6006B: 858 units. All substitutes are available in new original condition.

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