THF686K015P1F Equivalent & Substitute Parts

Part Overview

The THF686K015P1F is a 68 µF hermetically sealed tantalum capacitor rated at 15 V with axial through-hole mounting, manufactured by Cornell Dubilier Electronics (CDE). This component is classified as obsolete, indicating discontinued production and limited availability in the market. The part operates across a temperature range of -55°C to 125°C with an equivalent series resistance (ESR) of 95 mOhm and ±10% capacitance tolerance.

Due to its obsolete status, sourcing original THF686K015P1F units presents supply chain challenges. Active substitute components from Vishay Sprague maintain the core electrical specifications (68 µF capacitance, ±10% tolerance, hermetically sealed construction, axial through-hole mounting) while offering improved performance characteristics and assured long-term availability.

Key Parameters

Parameter	Value	Significance for Substitution
Capacitance	68 µF	Must remain constant across all substitutes
Tolerance	±10%	Must remain constant across all substitutes
Voltage Rating	15 V	Substitutes must equal or exceed this rating
Type	Hermetically Sealed Tantalum	Must remain constant across all substitutes
Mounting Type	Through Hole Axial	Must remain constant across all substitutes
Operating Temperature	-55°C to 125°C	Substitutes may extend upper limit; minimum must be maintained
ESR (Equivalent Series Resistance)	95 mOhm	Lower ESR values indicate performance improvement
Product Status	Obsolete	Active substitutes ensure future availability

Substitute Part Grouping Explanation

Substitution logic for the THF686K015P1F is based on strict adherence to the following criteria:

Mandatory Matching Parameters:

Capacitance: 68 µF (exact match required)
Tolerance: ±10% (exact match required)
Type: Hermetically sealed tantalum construction
Mounting: Through-hole axial configuration
Operating temperature minimum: -55°C (must be maintained or exceeded)

Allowable Variation Parameters:

Voltage rating: Substitutes rated at 25 V, 30 V, 35 V, 75 V, or 100 V are acceptable. Higher voltage ratings provide design margin and are electrically compatible in circuits designed for 15 V operation.
ESR: Lower values represent performance improvements in high-frequency applications and transient response.
Operating temperature maximum: Extension to 200°C provides enhanced thermal capability without compromising baseline performance.
Physical dimensions: Minor variations in diameter and length are acceptable provided through-hole axial mounting remains compatible with PCB layouts.

All substitute parts listed are manufactured by Vishay Sprague and carry active product status, ensuring supply chain continuity and technical support availability.

Parameter Comparison

Part Number	Manufacturer	Capacitance	Tolerance	Voltage Rating	ESR (mOhm)	Operating Temp. Range	Size (Dia x L)	Product Status
THF686K015P1F	Cornell Dubilier	68 µF	±10%	15 V	95	-55°C to 125°C	0.289" x 0.686"	Obsolete
109D686X9025C2	Vishay Sprague	68 µF	±10%	25 V	4.3	-55°C to 125°C	0.219" x 0.608"	Active
135D686X9025C2	Vishay Sprague	68 µF	±10%	25 V	4.3	-55°C to 125°C	0.203" x 0.453"	Active
135D686X9025C6	Vishay Sprague	68 µF	±10%	25 V	4.3	-55°C to 200°C	0.203" x 0.453"	Active
135D686X9030F2	Vishay Sprague	68 µF	±10%	30 V	2.9	-55°C to 125°C	0.296" x 0.641"	Active
135D686X9030F6	Vishay Sprague	68 µF	±10%	30 V	2.9	-55°C to 200°C	0.296" x 0.641"	Active
135D686X9035F2	Vishay Sprague	68 µF	±10%	35 V	2.9	-55°C to 125°C	0.296" x 0.641"	Active
135D686X9035F6	Vishay Sprague	68 µF	±10%	35 V	2.9	-55°C to 200°C	0.296" x 0.641"	Active
135D686X9075F2	Vishay Sprague	68 µF	±10%	75 V	3	-55°C to 125°C	0.296" x 0.641"	Active
135D686X9075F6	Vishay Sprague	68 µF	±10%	75 V	3	-55°C to 200°C	0.296" x 0.641"	Active
ST68-100T2KI	Vishay Sprague	68 µF	±10%	100 V	2.1	-55°C to 125°C	0.312" x 0.641"	Active

Engineering Selection Recommendations

Primary Selection Criteria:

Supply Chain Continuity: All listed substitutes carry active product status from Vishay Sprague, ensuring availability and technical support. The original THF686K015P1F is obsolete and subject to supply constraints.
Voltage Margin Selection: Choose substitute voltage ratings based on circuit design requirements:
- 25 V rated parts (109D686X9025C2, 135D686X9025C2, 135D686X9025C6): Provide minimal voltage margin above the 15 V requirement. Suitable for applications with stable, regulated power supplies.
- 30 V and 35 V rated parts (135D686X9030F2, 135D686X9030F6, 135D686X9035F2, 135D686X9035F6): Offer moderate voltage margin. Recommended for general industrial applications.
- 75 V and 100 V rated parts (135D686X9075F2, 135D686X9075F6, ST68-100T2KI): Provide maximum voltage margin. Suitable for applications with transient overvoltage conditions or high-reliability requirements.
Temperature Range Consideration: Parts designated with "F6" suffix (135D686X9025C6, 135D686X9030F6, 135D686X9035F6, 135D686X9075F6) extend operating temperature to 200°C. Select these variants for applications requiring enhanced thermal performance or operation in elevated ambient conditions.
ESR Performance: Substitute parts exhibit significantly lower ESR values (2.1 to 4.3 mOhm) compared to the original (95 mOhm). This improvement reduces ripple voltage and heat generation, particularly beneficial in switching power supply and high-frequency filtering applications.
Physical Compatibility: Verify PCB layout accommodation for dimensional variations. The 135D series parts (0.203" to 0.296" diameter) are more compact than the original THF686K015P1F (0.289" diameter), facilitating space optimization. The ST68-100T2KI (0.312" diameter) is slightly larger.
Compliance Status: All substitute parts maintain RoHS non-compliant status consistent with the original component. REACH and ECCN classifications remain unchanged.

Frequently Asked Questions (FAQ)

Q1: Can I directly replace THF686K015P1F with any of the listed substitutes?

A: Yes, all listed substitutes are electrically and mechanically compatible. The 68 µF capacitance, ±10% tolerance, hermetically sealed construction, and through-hole axial mounting are identical. Higher voltage ratings (25 V through 100 V) are backward-compatible with 15 V circuit designs. Verify physical dimensions fit your PCB layout before final selection.

Q2: Why do substitute parts have lower ESR values?

A: ESR reduction reflects advances in tantalum capacitor manufacturing technology. Lower ESR improves transient response, reduces ripple voltage, and decreases heat dissipation. This represents a performance enhancement over the original THF686K015P1F design.

Q3: What is the difference between 135D686X9030F2 and 135D686X9030F6?

A: Both parts are identical except for operating temperature range. The F2 variant operates -55°C to 125°C (matching the original). The F6 variant extends to -55°C to 200°C, providing enhanced thermal capability. Select F6 for high-temperature applications; F2 for standard industrial use.

Q4: Should I select the highest voltage rating (100 V) for maximum safety margin?

A: Higher voltage ratings provide design margin but increase component size and cost. Select voltage ratings based on actual circuit requirements and transient overvoltage conditions. For 15 V nominal circuits without significant overvoltage events, 25 V to 35 V ratings provide adequate margin. Reserve 75 V and 100 V selections for applications with documented transient conditions or high-reliability requirements.

Q5: Are there physical size constraints I should consider?

A: Yes. The original THF686K015P1F measures 0.289" diameter × 0.686" length. Substitute parts vary: 135D series (0.203" to 0.296" diameter) are more compact; ST68-100T2KI (0.312" diameter) is slightly larger. Verify your PCB layout accommodates the selected substitute's dimensions, particularly in space-constrained designs.

Q6: What is the significance of the "109D" versus "135D" series designation?

A: Both are Vishay Sprague wet tantalum capacitor series. The 109D series (TANTALEX™) and 135D series represent different product lines with identical electrical specifications for this 68 µF application. Both are active and fully supported. Selection between them is based on availability and physical size requirements.

Q7: Is the ST68-100T2KI "SuperTan®" designation significant?

A: SuperTan® is Vishay Sprague's premium tantalum capacitor line. The ST68-100T2KI offers the lowest ESR (2.1 mOhm) and highest voltage rating (100 V) among all substitutes. Select this part for demanding applications requiring superior transient response and maximum voltage margin.

Q8: Can I use these substitutes in new designs, or only as replacements?

A: All listed substitutes carry active product status and are suitable for both replacement and new design applications. Using active parts in new designs ensures long-term component availability and technical support throughout the product lifecycle.

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