The SSOP-24 is a 24-lead shrink small outline package with gull-wing leads on two sides and a nominal lead pitch of 0.65 mm (25.6 mil). It occupies roughly half the board area of an equivalent 24-pin SOIC while remaining compatible with standard reflow soldering. Two JEDEC-registered body widths exist — 3.9 mm (MO-137) and 5.3 mm (MO-150) — and confusing them is one of the most common footprint errors in SSOP-24 designs. This article consolidates the dimensions, pinout conventions, recommended land patterns, and practical design guidance you need to get the footprint right the first time.
Key Takeaways
• Two distinct JEDEC variants share the “SSOP-24” name: the 3.9 mm-wide body (MO-137, 0.635 mm pitch) and the 5.3 mm-wide body (MO-150, 0.65 mm pitch). Always verify which one your IC uses.
• The recommended IPC-7351 pad size for a 0.65 mm pitch SSOP-24 is approximately 0.42 mm × 1.50 mm, centered at the maximum lead span.
• Peak reflow temperature for lead-free SSOP-24 devices is typically 260 °C, with a maximum time above liquidus of 60–90 s per J-STD-020.
• SSOP-24 saves 30–40% board area compared to an SOIC-24 at 1.27 mm pitch but demands tighter stencil aperture control to avoid solder bridging.
What Is the SSOP-24 Package?
SSOP stands for Shrink Small Outline Package. The “shrink” refers to the reduced lead pitch compared to the standard SOP/SOIC family, which uses 1.27 mm (50 mil) pitch. By halving the pitch to 0.635–0.65 mm, the SSOP fits 24 leads into a body that would otherwise accommodate only 12–14 at SOP spacing.
The package uses a copper-alloy lead frame encapsulated in a thermoset epoxy molding compound, with solder-plated gull-wing leads extending from the two long sides of the rectangular body. SSOP-24 packages are registered under two JEDEC outlines, and this distinction matters because the body widths differ by more than 1 mm.
[IMAGE 1: SSOP-24 package outline drawing showing body dimensions D, E, lead pitch e, and seated height A | alt: “SSOP-24 package outline drawing with labeled dimensions for body length, body width, lead pitch, and seated height”]
SSOP-24 Dimension Variants
The single biggest source of PCB layout errors with the SSOP-24 is mismatching the JEDEC variant. The two registered outlines are:
JEDEC MO-137 (narrow body, 3.9 mm width): Used by NXP (SOT556-1), STMicroelectronics, and Diodes Inc. (Type A1). Lead pitch is 0.635 mm (25 mil), and body length ranges from 8.6 mm to 8.8 mm per the NXP SOT556-1 specification.
JEDEC MO-150 (wide body, 5.3 mm width): Used by Analog Devices (G24 package, drawing 05-08-1640), Richtek, and many Asian suppliers. Lead pitch is 0.65 mm, and body length ranges from 7.90 mm to 8.50 mm per the Analog Devices package drawing.
The table below compiles dimensions from manufacturer package outlines cross-referenced against the JEDEC registrations.
| Parameter | Sym. | MO-137 Min | MO-137 Typ | MO-137 Max | MO-150 Min | MO-150 Typ | MO-150 Max | Unit |
| Body length | D | 8.60 | 8.70 | 8.80 | 7.90 | 8.20 | 8.50 | mm |
| Body width | E | 3.80 | 3.90 | 4.00 | 5.00 | 5.30 | 5.60 | mm |
| Seated height | A | — | 1.73 | 1.73 | — | — | 2.00 | mm |
| Package height | A2 | 1.40 | 1.47 | 1.55 | — | — | — | mm |
| Standoff | A1 | 0.10 | — | 0.25 | 0.05 | — | — | mm |
| Lead pitch | e | 0.635 BSC | 0.65 BSC | mm | ||||
| Lead width | b | 0.20 | — | 0.31 | 0.22 | — | 0.38 | mm |
| Lead length | L | 0.41 | — | 0.89 | 0.55 | — | 0.95 | mm |
| Lead span | HE | 5.80 | — | 6.20 | 7.40 | 7.80 | 8.20 | mm |
| Coplanarity | — | — | — | 0.10 | — | — | 0.10 | mm |
| Lead angle | θ | 0° | — | 8° | 0° | — | 8° | — |
Sources: NXP SOT556-1 rev. 2016-02-08; Analog Devices drawing 05-08-1640; Diodes Inc. SSOP-24 Type A1.
Some manufacturers — particularly Infineon with their PG-SSOP-24 family — ship variants with an exposed thermal pad on the package underside. Infineon’s PG-SSOP-24-14, for example, has an 8.65 mm body length, 3.9 mm body width, and an exposed pad that requires a dedicated thermal land on the PCB. Always check whether your specific part has an exposed pad; it changes both the footprint and the thermal path.
SSOP-24 Pinout Convention
Pin numbering follows the standard JEDEC convention for dual-inline surface-mount packages. Pin 1 is identified by a molded dot, notch, or chamfer on one end of the package body. Counting proceeds counterclockwise when viewed from above: pins 1–12 run down the left side, and pins 13–24 run up the right side, with pin 13 directly opposite pin 12.
The actual signal assignment on each pin is entirely IC-specific. There is no standardized SSOP-24 pinout — the pin functions are defined by the component datasheet, not by the package itself.
Recommended Footprint and Land Pattern
The IPC-7351 standard provides a systematic method for calculating land patterns based on component tolerances and three density levels: Most (Level A, largest pads), Nominal (Level B), and Least (Level C, smallest pads).
For a 0.65 mm-pitch SSOP-24 at Nominal density, the following pad dimensions are typical:
| Parameter | MO-137 (3.9 mm) | MO-150 (5.3 mm) | Unit |
| Pad width (Y) | 0.42 | 0.42 | mm |
| Pad length (Z) | 1.50 | 1.50 | mm |
| Pad center span (X) | 5.50 | 7.80 | mm |
| Pad pitch | 0.635 | 0.65 | mm |
| Courtyard (L × W) | 9.30 × 6.85 | 10.0 × 9.5 | mm |
Sources: Richtek Footprint-SSOP-24 application note; NXP SOT556-1 reflow soldering footprint.
Solder paste stencil: For 0.65 mm pitch, use a laser-cut stainless steel stencil with apertures reduced to 80–90% of the pad area. A typical aperture for the pad above is 0.35 mm × 1.30 mm with a stencil thickness of 0.12 mm (5 mil). This produces approximately 0.06 mm³ of paste per pad — enough for a reliable fillet without excess that bridges to adjacent pads.
Solder mask: Maintain a minimum solder mask web of 0.08 mm between adjacent pads. At 0.65 mm pitch with 0.42 mm pads, this leaves 0.23 mm gap, which is marginal. Many fabricators require solder-mask-defined (SMD) pads rather than non-solder-mask-defined (NSMD) at this pitch.
[IMAGE 2: SSOP-24 recommended land pattern with pad dimensions labeled | alt: “SSOP-24 PCB land pattern showing pad width, pad length, pad pitch, and courtyard dimensions per IPC-7351”]
SSOP-24 vs TSSOP-24 vs SOIC-24
Engineers evaluating the SSOP-24 typically compare it against two alternatives: the thinner TSSOP-24 and the wider-pitch SOIC-24. The table below captures the parameters that drive package selection.
| Parameter | SOIC-24 | SSOP-24 (MO-150) | TSSOP-24 (MO-153) |
| Lead pitch | 1.27 mm | 0.65 mm | 0.65 mm |
| Body width | 7.50 mm | 5.30 mm | 4.40 mm |
| Body height (max) | 2.65 mm | 2.00 mm | 1.20 mm |
| Lead-tip span | ≈10.3 mm | 8.20 mm | 6.40 mm |
| Board area (approx.) | ≈105 mm² | ≈66 mm² | ≈50 mm² |
| Hand-solderable? | Yes, readily | Yes, with care | Yes, fine tip needed |
| Typical θJA | 70–90 °C/W | 80–110 °C/W | 100–140 °C/W |
The TSSOP-24 wins on board area and profile height but has higher thermal resistance due to its thinner body and reduced lead frame area. The SSOP-24 is the middle ground: substantially smaller than SOIC while still thick enough to dissipate moderate heat through its leads.
For signals above 50–100 MHz, the shorter lead length of both SSOP and TSSOP reduces parasitic inductance compared to SOIC, providing measurable signal-integrity improvement.
Common ICs in the SSOP-24 Package
The SSOP-24 houses a wide range of IC functions. The following are verified examples with their package designations:
| IC | Manufacturer | Function | Package Note |
| TLC5947 | Texas Instruments | 24-ch 12-bit PWM LED driver | SSOP-24 (not TSSOP) |
| TLE94112EL | Infineon | 12-ch half-bridge motor driver | PG-SSOP-24-9 |
| NCV7356 | onsemi | Single-wire CAN transceiver | SSOP-24, CASE 940D |
| BD9409F | ROHM | Boost LED driver for LCD | SSOP-A24 |
| ADG1206 | Analog Devices | 16:1 analog multiplexer | SSOP-24 (RS-24) |
Always confirm the exact pin count and package variant code in the component datasheet before committing a footprint. Some vendors use “SSOP” and “TSSOP” interchangeably in marketing materials, even when the packages differ physically.
PCB Layout and Assembly Considerations
Reflow soldering profile: ROHM’s SSOP-A24 package information (TSZ02201) specifies a peak reflow temperature of 260 °C ±3 °C with a preheat zone of 120–150 °C and preheat time under 60 s. For SAC305 lead-free solder, maintain 60–90 s above the 217 °C liquidus point. Ramp rate should stay below 2 °C/s to avoid thermal shock.
Moisture sensitivity: Most SSOP-24 devices are rated MSL 3 per J-STD-020, giving a floor life of 168 hours at ≤30 °C / 60% RH after opening the moisture barrier bag. If floor life is exceeded, bake at 125 °C for 24 hours before reflow. Failure to bake can cause popcorn cracking — internal delamination from vaporized moisture that produces no visible external damage but degrades long-term reliability.
Solder bridging prevention: At 0.65 mm pitch, solder bridging is the most common assembly defect. Three countermeasures reduce bridge risk significantly: (1) reduce stencil apertures to 85% of pad area, (2) verify solder paste volume stays near 0.05–0.06 mm³ per pad, and (3) maintain a minimum 0.08 mm solder mask web between pads.
Thermal management: Without an exposed pad, SSOP-24 packages dissipate heat primarily through their leads and the copper traces they connect to. Increasing the copper area on the power and ground pads, and adding thermal vias under the package body to an inner ground plane, can reduce θJA by 10–20 °C/W depending on the board stackup. For ICs dissipating more than 0.5 W, consider an exposed-pad variant (e.g., Infineon PG-SSOP-24-14) or upgrade to a QFN.
Hand soldering: The 0.65 mm pitch is at the practical limit for hand soldering. Use a chisel tip no wider than 1.0 mm, apply flux generously, and use the drag-soldering technique. Inspect under magnification (≥10×) afterward. A SSOP-to-DIP adapter board is available for prototyping — Logical Systems PA-SSD6SM18-24 accepts both SSOP and TSSOP at 0.65 mm pitch.
FAQ
What is the pitch of an SSOP-24 package?
The lead pitch is 0.635 mm (25 mil) for the narrow-body MO-137 variant and 0.65 mm (25.6 mil) for the wide-body MO-150 variant. The difference is 15 µm — within manufacturing tolerance — and most EDA libraries treat both as 0.65 mm pitch. Always confirm the exact pitch from the component datasheet rather than relying on the generic “SSOP-24” designation.
What is the difference between SSOP-24 and TSSOP-24?
Both use 0.65 mm lead pitch and 24 pins, but they differ in body width and height. The SSOP-24 (MO-150) has a 5.3 mm body width and up to 2.0 mm seated height, while the TSSOP-24 (MO-153) has a 4.4 mm body width and a maximum height of about 1.2 mm. The TSSOP is thinner and narrower, saving board area, but has higher thermal resistance. Their footprints are not interchangeable.
Can I hand-solder an SSOP-24?
Yes, with the right technique. You need a fine chisel or conical tip (0.5–1.0 mm), liquid or gel flux, thin solder wire (0.5 mm or less), and at least 10× magnification for inspection. Drag soldering — applying solder to one lead, then dragging the iron across the remaining leads with flux — works reliably. Solder wick removes any bridges.
What JEDEC standard covers the SSOP-24?
Two registrations apply. JEDEC MO-137 covers the narrow-body SSOP family with 0.150″ (3.81 mm nominal) body width and 0.025″ pitch. JEDEC MO-150 covers the 5.3 mm body-width family with 0.65 mm pitch. Both are published under JEDEC Publication 95 (JEP95). The specific variation letter identifies the exact pin count.
What is the moisture sensitivity level of a typical SSOP-24?
Most SSOP-24 devices are rated MSL 3 per IPC/JEDEC J-STD-020, requiring them to be soldered within 168 hours of opening the moisture barrier bag at factory conditions (≤30 °C, 60% RH). Some thinner-body or exposed-pad variants may carry MSL 1, meaning unlimited floor life. Check the moisture sensitivity caution label on the component reel packaging.
Decision Guide
Choose the SSOP-24 when your design needs more than 20 pins in a dual-inline surface-mount package, your board area cannot accommodate 1.27 mm-pitch SOIC, and your power dissipation stays below roughly 0.5 W without an exposed pad. It is a mature, widely sourced package with strong second-source availability across TI, NXP, Infineon, ROHM, and STMicroelectronics.
Switch to a TSSOP-24 if profile height matters — wearables, thin-form-factor boards, or stacked assemblies. Switch to a QFN or exposed-pad SSOP if your IC dissipates more than 0.5 W and thermal resistance is the binding constraint. If your contract manufacturer flags repeated solder bridging at 0.65 mm pitch, verify stencil apertures and mask webs before downgrading to a larger package — the problem is almost always process, not package.
