SCT640B Equivalent & Substitute Parts

Part Overview

The SCT640B is a Silicon Controlled Rectifier (SCR) rated for 600V off-state voltage and 40A on-state current in a TO-220-3 through-hole package. Manufactured by SMC Diode Solutions, this thyristor is designed for standard recovery applications requiring high voltage and moderate current switching capability. The SCT640B is classified as obsolete, making identification of equivalent and substitute parts essential for ongoing system support and component procurement.

Key Parameters

Parameter	Value	Unit
Voltage - Off State	600	V
Current - On State (It (RMS)) (Max)	40	A
Voltage - Gate Trigger (Vgt) (Max)	1.5	V
Current - Gate Trigger (Igt) (Max)	35	mA
Voltage - On State (Vtm) (Max)	1.55	V
Current - Hold (Ih) (Max)	75	mA
Current - Off State (Max)	10	µA
Current - Non Rep. Surge 50, 60Hz (Itsm)	460	A @ 50Hz
Operating Temperature Range	-40 to 125	°C (TJ)
Package / Case	TO-220-3	-
Mounting Type	Through Hole	-
SCR Type	Standard Recovery	-

Substitute Part Grouping Explanation

Substitution of the obsolete SCT640B is determined by strict equivalence across electrical and mechanical parameters. The primary substitute identified is the SCT640C, which shares the same base product number (SCT640) and maintains electrical compatibility through identical voltage and current ratings.

The substitution criteria are based on the following key parameters:

Voltage - Off State: 600V (must match exactly)
Current - On State (It (RMS)) (Max): 40A (must match exactly)
Voltage - Gate Trigger (Vgt) (Max): 1.5V (must match exactly)
Current - Gate Trigger (Igt) (Max): 35mA (must match exactly)
Voltage - On State (Vtm) (Max): 1.55V (must match exactly)
Current - Hold (Ih) (Max): 75mA (must match exactly)
Package / Case: TO-220-3 (must match exactly)
Mounting Type: Through Hole (must match exactly)
SCR Type: Standard Recovery (must match exactly)

Parameter Comparison

Parameter	SCT640B (Main Part)	SCT640C (Substitute)	Match Status
Manufacturer	SMC Diode Solutions	SMC Diode Solutions	Identical
Category	Thyristors	Thyristors	Identical
Description	SCR 600V 40A TO220B	SCR 600V 40A TO220B	Identical
Base Product Number	SCT640	SCT640	Identical
Voltage - Off State	600 V	600 V	Identical
Current - On State (It (RMS)) (Max)	40 A	40 A	Identical
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.5 V	Identical
Current - Gate Trigger (Igt) (Max)	35 mA	35 mA	Identical
Voltage - On State (Vtm) (Max)	1.55 V	1.55 V	Identical
Current - Hold (Ih) (Max)	75 mA	75 mA	Identical
Current - Off State (Max)	10 µA	Not specified	-
Current - Non Rep. Surge 50, 60Hz (Itsm)	460 A @ 50Hz	Not specified	-
Operating Temperature Range	-40 to 125 °C (TJ)	Not specified	-
Package / Case	TO-220-3	TO-220-3	Identical
Mounting Type	Through Hole	Through Hole	Identical
SCR Type	Standard Recovery	Standard Recovery	Identical
Product Status	Obsolete	Active	Different
ECCN	EAR99	EAR99	Identical
HTSUS	8541.30.0080	8541.30.0080	Identical

Engineering Selection Recommendations

The SCT640C is the manufacturer-recommended substitute for the obsolete SCT640B. Both components share identical electrical specifications across all critical parameters: 600V off-state voltage, 40A on-state current, gate trigger characteristics, and on-state voltage drop. The TO-220-3 package and through-hole mounting type are identical, ensuring direct mechanical compatibility in existing PCB designs.

The primary distinction is product status: the SCT640B is obsolete, while the SCT640C is active and currently in production. This transition from SCT640B to SCT640C represents a standard product lifecycle update within the SCT640 series from SMC Diode Solutions. Both components maintain identical ECCN (EAR99) and HTSUS (8541.30.0080) classifications, confirming regulatory equivalence.

Current inventory availability shows 906 pieces of SCT640C in stock, supporting immediate procurement for new designs and legacy system support.

Frequently Asked Questions (FAQ)

Q: Can the SCT640C directly replace the SCT640B in existing designs?

A: Yes. The SCT640C is electrically and mechanically identical to the SCT640B across all specified parameters. The TO-220-3 package, through-hole mounting, and electrical ratings (600V, 40A) are unchanged. Direct substitution is supported without circuit modification.

Q: Why is the SCT640B classified as obsolete?

A: The SCT640B has reached end-of-life status. The SCT640C represents the active production equivalent within the same SCT640 product family, maintaining full electrical and mechanical compatibility.

Q: Are there any compliance or regulatory differences between SCT640B and SCT640C?

A: No. Both components share identical ECCN (EAR99) and HTSUS (8541.30.0080) classifications. Regulatory compliance status is equivalent.

Q: What is the relationship between SCT640B and SCT640C?

A: Both components share the same base product number (SCT640) and are manufactured by SMC Diode Solutions. The SCT640C is the active production successor to the obsolete SCT640B, with identical electrical and mechanical specifications.

Q: Is the TO-220-3 package the same for both parts?

A: Yes. Both the SCT640B and SCT640C use the TO-220-3 through-hole package. PCB footprints and thermal management designs are directly compatible.

Q: What are the critical electrical parameters for substitution?

A: Substitution is valid when the following parameters match: 600V off-state voltage, 40A on-state current (RMS), 1.5V maximum gate trigger voltage, 35mA maximum gate trigger current, 1.55V maximum on-state voltage, and 75mA maximum hold current. The SCT640C meets all these requirements.

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