FR107W - 1A/1000V Fast Recovery Rectifier Diode

What Is FR107W and How Does It Work?

It is a fast recovery silicon rectifier diode. Forward bias = current flows from anode to cathode. Reverse bias = it blocks up to 1000V. The "fast recovery" part means when you switch it from forward to reverse bias, it stops conducting in about 500 nanoseconds - fast enough for switching frequencies up to ~50kHz.

Compare this to a standard 1N4007 rectifier (trr ~2µs) - the FR107W recovers 4x faster, which means significantly less reverse recovery loss in a switching converter. But compared to an ultrafast UF4007 (trr ~75ns), it is 6x slower. So the FR107W sits in the middle: faster than a standard rectifier, cheaper than an ultrafast.

Position in the product line: Workhorse mid-speed rectifier. Not for high-frequency LLC converters (you want UF-series), not for 50Hz bridge rectifiers where a 1N4007 is cheaper and works fine. Best use case is flyback secondary rectification, PFC boost diodes, and anywhere you have medium-frequency switching (20kHz–50kHz) and need the 1000V rating.

What Are the Specifications of FR107W?

What 500ns trr actually means in practice: At 50kHz switching frequency (20µs period), 500ns is 2.5% of the period - the diode spends 2.5% of each cycle in reverse recovery. Acceptable. At 200kHz (5µs period), that becomes 10% - the recovery losses start to hurt efficiency and heat up the diode. At 500kHz+, the losses become dominant. Rule of thumb: FR107W is comfortable up to ~50kHz.

Marking

The FR107W is typically marked "F7" on the body. Cathode is indicated by a band at the cathode end.

What Is FR107W Used For?

Flyback Converter Secondary Rectification

The classic use case. A flyback converter at 30kHz–50kHz switching frequency needs a diode that can handle high voltage (V_rrm = V_out + V_in × turns ratio) and recover fast enough not to burn. The FR107W with 500ns trr and 1000V rating covers most medium-power flyback designs.

PFC Boost Diode (Low-to-Medium Frequency)

Power factor correction boost stages running at 20kHz–50kHz. Not recommended for CCM PFC at high power - the 500ns trr causes too much reverse recovery loss - but for basic boost PFC under 100W, it works.

Snubber / Clamp Diode

RCD snubber across the primary winding of an isolated converter, or as a clamp diode in flyback RCD circuits. The 1000V rating is essential here - the reflected voltage on the primary side can exceed 800V.

Freewheeling Diode (Medium-Speed Switching)

Freewheeling path for inductive loads (relays, solenoids, small motors) switched at moderate frequency. The 500ns recovery means it does not linger in conduction when the switch turns off.

High-Voltage Reverse Protection

Reverse polarity protection on high-voltage DC rails (up to 1000V). The 1A rating limits it to low-power circuits, but for auxiliary supplies it is a compact solution.

FR107W Cross-Reference and Alternatives

Direct Cross-Reference (Same FR107W from different brands)

Functional Alternatives

Quick selection guide:

• Need the exact SMD footprint: Stick with FR107W (SOD-123FL).
• Faster recovery in SMD: US1M (75ns, SMA) - redesign PCB layout for the larger SMA footprint.
• Cheapest option: Through-hole FR107 (DO-41) is pennies and works everywhere.
• Upgrade for higher frequency: UF4007 (75ns) - drops in for any DO-41 board, faster recovery = less heat.

How to Verify Genuine FR107W?

Markings: The marking is "F7" on the package body, with a cathode band. Laser marking should be clear and permanent. Blurry or painted-on markings are suspicious.

Forward voltage check: With a multimeter diode test, you should read ~0.5V–0.7V at low current (the test current of most DMMs is ~1mA). Open circuit in reverse.

Reverse leakage test: Measure leakage at 1000V - requires a high-voltage source. Genuine parts show ≤5µA at 25°C. Significantly higher leakage indicates a substandard die or a lower-voltage part relabeled.

Batch traceability: At ICMASS, we source from manufacturers with full traceability. We test random samples from each batch for trr to ensure you get fast recovery, not a standard rectifier marked as FR.

Frequently Asked Questions About FR107W

Q1: What is the difference between FR107 and FR107W?

A: Only the package. FR107 is through-hole DO-41, FR107W is surface-mount SOD-123FL. Electrical specs are identical. Choose by your PCB assembly process.

Q2: Can I replace FR107W with UF4007?

A: UF4007 is DO-41 (through-hole). For SMD, use US1M instead. Both are upgrades: 75ns trr vs 500ns, same 1000V/1A rating.

Q3: Can I replace FR107W with a standard 1N4007?

A: Only for 50/60Hz rectification. 1N4007 has 2µs trr - in a switching converter above a few kHz, it will overheat and fail. Do not substitute a standard rectifier for a fast recovery diode.

Q4: Why is my FR107W getting hot in a flyback converter?

A: Three possibilities. (1) Frequency too high - above 50kHz the 500ns trr causes excessive reverse recovery loss, switch to UF4007 or US1M. (2) Forward current too high - check your duty cycle and peak current. (3) Insufficient copper pour on the PCB - SOD-123FL relies on PCB copper for cooling.

Q5: What does 500ns reverse recovery time mean in practice?

A: The diode keeps conducting for 500ns after the voltage reverses. At 50kHz that is ~2.5% duty cycle loss. At 200kHz it is ~10% - which is why FR107W is not recommended for high-frequency designs.

Q6: What is the surge current capability of FR107W?

A: 30A for 8.3ms. Covers inrush in most 1A designs. For repetitive surges, derate aggressively.

Q7: Is FR107W RoHS compliant?

A: Yes, all current production FR107W parts are RoHS compliant and lead-free.

Q8: What is the difference between FR107W and US1M?

A: Package and speed. FR107W is SOD-123FL, 500ns. US1M is SMA, 75ns. US1M is faster but needs larger PCB footprint.

Q9: Can I use FR107W for LED lighting?

A: Yes, in AC-powered LED driver bridge rectifiers. For dimmable or PFC-corrected designs above 50kHz, use a faster diode like US1M.

Q10: What is the difference between FR107W and HER108?

A: HER108 is through-hole DO-41 with 75ns trr and lower Vf (1.0V). FR107W is SMD with 500ns trr and 1.3V Vf. HER108 is the better part for efficiency, but FR107W is the SMD option.

Pricing & Availability

Stock: Available from multiple manufacturers. Typical lead time 3-5 business days.

Minimum order: 50 pieces for loose quantities. Full reel (3000 pcs) for production orders.