SS14 PCB Design Guide: Footprint, Pinout, and Alternatives
1 A, 40 V surface-mount Schottky barrier rectifier in SMA (DO-214AC) — the SMD equivalent of the 1N5819, with the same electrical ratings in a compact reflow-compatible package.
The SS14 is a 1 A, 40 V Schottky barrier rectifier in an SMA (DO-214AC) surface-mount package. Vishay specifies a maximum instantaneous forward voltage of 0.50 V at 1 A and lists low-voltage, high-frequency inverters, freewheeling, DC/DC converters, and polarity protection as typical applications. This page is specifically grounded in Vishay document 88746; parts sold under the same generic SS14 designation by another manufacturer need that manufacturer's datasheet checked separately.
The tradeoff is reverse leakage. A Schottky barrier leaks orders of magnitude more than a PN junction, and the leakage rises fast with temperature. Vishay guarantees 0.2 mA max reverse current at 25 degC and 5.0 mA at 100 degC, both at the full 40 V blocking voltage. In a battery-powered device or a precision analog front-end, 5.0 mA of leakage at operating temperature can drain more energy than the forward drop ever saved. The 40 V reverse rating is the middle of the SS1x family (SS12 = 20 V, SS16 = 60 V), and it is low by rectifier standards: a 24 V rail with an inductive transient can sail past 40 V, so a design that runs near the rating needs a TVS or snubber upstream — the guardring on the die is for transient overvoltage protection, not repetitive avalanche.
SS14 is a multi-sourced generic part number. STMicroelectronics, onsemi, Diodes Incorporated, and others make diodes sold under the SS14 designation, each with its own datasheet and guaranteed limits. This page cites Vishay's document 88746. When a rating is near the edge of your design, verify the datasheet of the manufacturer actually on your reel. The mistakes that kill SS14s or the circuits around them are predictable: treating the 0.50 V forward drop as a constant at all currents, ignoring the 25x increase in reverse leakage from 25 degC to 100 degC, mounting the SMA package with inadequate copper for heat spreading, confusing the base MPN with the orderable suffix, and assuming the 40 V rating gives generous headroom on a switching rail. Each is covered below.
What breaks boards
Reverse leakage jumps 25x from 25 degC to 100 degC. Size the standby budget for the hot number, not the cold one.
Vishay specifies IR <= 0.2 mA at 25 degC and IR <= 5.0 mA at 100 degC, both at the rated DC blocking voltage. That 25x change can matter in battery-powered and always-connected circuits. Evaluate leakage at the expected operating temperature rather than carrying the room-temperature limit into the power budget.
The 88 degC/W thermal figure depends on the datasheet's copper-pad test condition.
The typical RthetaJA value of 88 degC/W is specified for PCB mounting with 5 mm x 5 mm copper pad areas. Treat it as a layout-dependent reference, not a package constant that survives any footprint and copper geometry. Use the forward-drop curves, expected duty cycle, ambient temperature, and actual board copper when checking junction temperature.
40 V VRRM is the family's middle child. Any switching-ring on a 24 V rail can exceed it.
SS14 is the 40 V member of the SS1x family (SS12 = 20 V, SS13 = 30 V, SS14 = 40 V, SS15 = 50 V, SS16 = 60 V). A 24 V nominal rail with ringing from an LC filter or a fast-switching MOSFET can easily sail past 40 V peak. The datasheet does not list a non-repetitive peak reverse voltage (VRSM), so design to the 40 V VRRM with engineering margin. If the rail is 24 V or higher with any switching energy, consider the SS15 (50 V) or SS16 (60 V) instead, or add a TVS clamp upstream. Do not treat SS14 as a universal drop-in for 1N4007-class rectifiers — those are rated for 1000 V. The dV/dt rating of 10,000 V/us is generous for a Schottky, but that measures the voltage ramp the diode can block, not the peak voltage it can withstand.
Guardring transient protection is not an avalanche rating. Do not subject SS14 to repetitive reverse breakdown.
The datasheet lists 'Guardring for overvoltage protection' as a feature but provides no avalanche-energy rating. Do not convert that feature line into permission for repetitive operation above the 40 V VRRM. If the circuit can generate recurring reverse-voltage excursions beyond the rating, use an appropriately rated clamp or a higher-voltage rectifier.
SS14 is a base MPN — multiple orderable suffixes exist. Pin down the exact variant on your BOM.
Vishay offers SS14 in several orderable variants: SS14-E3 (commercial, RoHS-compliant), SS14-M3 (halogen-free, RoHS-compliant), SS14HE3 (AEC-Q101 qualified automotive), and SS14HM3 (halogen-free automotive). Each is available in 1800-piece 7-inch reels (/61T or /H suffix) or 7500-piece 13-inch reels (/5AT or /I suffix). The base electrical specs are identical across all variants, but automotive qualification paperwork exists only for the HE3/HM3 suffixes. When a BOM says 'SS14' without a suffix, the distributor may substitute any variant. This matters for automotive programs, halogen-free assembly requirements, and pick-and-place reel compatibility — a 13-inch reel for a 7-inch feeder wastes the entire reel. The device marking code S4 is common to all SS14 variants; the cathode band denotes the cathode end.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| VRRM (max repetitive peak reverse voltage) | 40 V | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, VRRM row, SS14 column |
| VRMS (max RMS voltage) | 28 V | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, VRMS row, SS14 column |
| IF(AV) (max average forward rectified current) | 1.0 A at TL (see derating curve, fig. 1) | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, IF(AV) row |
| IFSM (peak forward surge current) | 40 A (8.3 ms single half sine-wave superimposed on rated load) | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, IFSM row |
| VF at 1.0 A (max instantaneous forward voltage) | 0.50 V (pulse test: 300 us pulse width, 1 % duty cycle) | Vishay 88746 Rev 23-Apr-2020, Electrical Characteristics table, VF(1) row, SS12-SS14 column |
| IR at 25 degC (max reverse leakage) | 0.2 mA (at rated DC blocking voltage, TA = 25 degC) | Vishay 88746 Rev 23-Apr-2020, Electrical Characteristics table, IR(2) at TA = 25 degC row |
| IR at 100 degC (max reverse leakage) | 5.0 mA (at rated DC blocking voltage, TA = 100 degC) | Vishay 88746 Rev 23-Apr-2020, Electrical Characteristics table, IR(2) at TA = 100 degC row, SS14-SS16 column |
| TJ, TSTG (operating junction and storage temperature) | -65 to +150 degC | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, TJ and TSTG rows |
| Thermal resistance | RthetaJA 88 degC/W typ, RthetaJL 28 degC/W typ (5 mm x 5 mm copper pad areas) | Vishay 88746 Rev 23-Apr-2020, Thermal Characteristics table |
| Device marking code | S4 (cathode band denotes cathode end) | Vishay 88746 Rev 23-Apr-2020, Maximum Ratings table, Device marking code row, SS14 column |
Verified against the manufacturer datasheet on 2026-07-12. Confirm the current revision before production use.
Alternatives
- 1N5819: Through-hole equivalent: 1 A, 40 V Schottky barrier rectifier in DO-41. Same electrical ratings in a through-hole package. Thermal performance differs due to the larger DO-41 lead frame and longer leads.
- SS34: Surface-mount step-up: 3 A, 40 V Schottky barrier rectifier in SMC (DO-214AB). Same voltage rating with triple the current capacity for higher-power freewheeling and rectification applications.
- SS16: Higher-voltage sibling in the same SS1x family and SMA package: 1 A, 60 V Schottky. Use when the 40 V VRRM of the SS14 is too tight for the rail with switching noise or ringing.
- B140-E3: Alternative Vishay 1 A, 40 V Schottky in SMA from a different product family (document 88946). Different die and slightly different VF/IR characteristics. Check the specific datasheet before substituting at the margins.
Common questions
- SS14 vs 1N5819: which one do I need?
- Both are commonly specified as 1 A, 40 V Schottky rectifiers, but the package and manufacturer-specific limits differ. Vishay's SS14 is surface-mount SMA (DO-214AC), while the 1N5819 page covers a through-hole DO-41 device. Choose by assembly method and then verify forward voltage, leakage, and thermal conditions against the exact manufacturer's datasheet rather than treating the names as universally interchangeable.
- How hot does an SS14 get at 1 A?
- The datasheet gives a typical RthetaJA of 88 degC/W only for its stated 5 mm x 5 mm copper-pad condition. Junction temperature depends on the actual forward voltage at the operating current, conduction duty cycle, ambient temperature, board copper, and nearby heat sources. Use the datasheet curves and your real layout rather than publishing one universal temperature for 1 A operation.
- Can I use an SS14 for reverse-polarity protection?
- Yes, for low-voltage DC inputs in surface-mount designs. Place it in series with the positive rail (anode to input, cathode to load): the Schottky's low forward drop means less voltage lost to the protection diode than a standard rectifier. The tradeoff is reverse leakage: at elevated temperature, the diode's reverse current can draw milliamps from a connected but reversed supply, and in a battery application that leakage drains the cell even when polarity is correct if the diode is placed in shunt (crowbar) configuration. For series protection on a 5 V or 12 V rail at up to 1 A, the SS14 is a standard choice.
- What is the SS14 marking code, and does it distinguish orderable variants?
- The device marking code is S4 for all SS14 variants, regardless of the orderable suffix (E3, M3, HE3, HM3). The cathode band denotes the cathode end. The marking alone does not tell you whether the part is commercial or automotive grade — only the full orderable part number and manufacturer's label on the reel provide that information. If you need to prove automotive qualification traceability, buy the SS14HE3 or SS14HM3 suffix explicitly.
- SS14 vs SS34 vs SS16: which one belongs on my BOM?
- SS14 is 1 A / 40 V — the baseline surface-mount Schottky for low-voltage freewheeling and rectification. Step up to SS34 (3 A / 40 V in SMC) when the forward current exceeds 1 A. Step sideways to SS16 (1 A / 60 V in SMA) when the 40 V reverse rating is too tight for the rail. All three share the same Schottky operating principles; the choice is a current and voltage headroom decision based on your specific circuit. The SS16 keeps the same SMA footprint as the SS14, making it a drop-in voltage upgrade in many layouts.
Sources
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