SSOP stands for Shrink Small Outline Package: a plastic, leadframe-based surface-mount package with gull-wing leads on its two long sides and a lead pitch below the 1.27 mm SOIC standard, typically 0.65 mm. Body widths come in 150, 209 and 300 mil, with body thickness usually between 1.65 mm and 1.85 mm, and lead counts from 8 to 64.

Construction is conventional. A copper leadframe carries a wire-bonded die inside epoxy mold compound, with solder-plated leads formed outward and down. Amkor lists NiPdAu pre-plated frame as its standard lead finish with matte tin optional, and copper wire as the standard interconnect.

Two registration systems collide in this family. JEDEC assigns MO numbers to the outlines; JEITA, still called EIAJ by some vendors, maintains a parallel set. Amkor describes the 5.3 mm SSOP body as 209 mil, a JEITA-derived width rather than a round JEDEC figure — which is why the same physical part appears as SSOP in one catalog and SOP in another.

[IMAGE 1: cross-section of an SSOP showing leadframe, die attach pad, wirebond, mold compound and gull-wing lead form | alt: “SSOP package cross section showing copper leadframe and gull-wing lead”]

SSOP dimensions and pitch, by JEDEC registration

Start from the registration, then pull the vendor drawing. These are the four registrations that carry the SSOP name, with the TSSOP family included for contrast.

JEDEC registration	Description on the register	Lead pitch	Body width	Registered lead counts
MO-137	Plastic Shrink Small Outline Package (SSOP) Family, R-PDSO/SSOP/SOIC	0.635 mm (0.025 in)	3.8 mm (0.150 in)	Vendor dependent
MO-150	SSOP, 5.3 mm body width, R-PDSO-G	0.65 mm	5.3 mm	8, 14, 16, 18, 20, 22, 24, 28, 30
MO-152	SSOP pitch family	0.4 / 0.5 / 0.65 mm	Family	Family
MO-154	SSOP, 3.9 mm body width	0.4 mm	3.9 mm	Family
MO-153 (TSSOP, for contrast)	TSSOP family	0.65 mm on the 4.4 mm body	4.3–4.5 mm (PW0016A)	8 to 68

Table 1. SSOP-family JEDEC registrations, pitch and body width. Source: JEDEC JEP95 MO index and registration pages.

MO-150 is the one to reach for first. Amkor builds 14/16, 20, 24 and 28-lead versions on a common 5.3 mm body with 1.73 mm body thickness, 0.13 mm standoff, 1.86 mm overall height and a 7.80 mm tip-to-tip lead span; only the body length changes, from 6.2 mm at 14/16 leads to 10.2 mm at 28. Renesas builds to the same registration: its PYG28 drawing (PSC-4032-04 rev 02) gives 0.65 mm nominal pitch, 10.07–10.33 mm body length, 5.20–5.38 mm body width, 1.99 mm A max and under 0.4 g package weight, based on JEDEC JEP95 MO-150.

MO-137 is where the confusion starts. It is a 0.025 in pitch, 0.150 in body-width registration, and most vendors sell parts built to it as QSOP. TI does not: its DBQ0016A drawing is titled SHRINK SMALL-OUTLINE PACKAGE, at 0.635 mm pitch, 4.81–5.00 mm body length and 3.81–3.98 mm body width, 1.75 mm max height.

Three outlines, one name

Within a single vendor’s catalog, SSOP resolves to three incompatible packages. All figures below come from the current TI mechanical drawings.

TI drawing	Code	Pitch (mm)	Body L × W (mm)	Max height (mm)	Lead width (mm)	Land row span (mm)
DB0028A	DB	0.65	9.9–10.5 × 5.0–5.6	2.00	0.22–0.38	7.0
DB0016A	DB	0.65	5.9–6.5 × 5.0–5.6	2.00	0.22–0.38	7.0
DBQ0016A	DBQ	0.635	4.81–5.00 × 3.81–3.98	1.75	0.21–0.30	5.4
DCT0008A	DCT	0.65	2.9–3.1 × 2.9–3.1	1.30	0.15–0.30	3.8

Table 2. Three Texas Instruments outlines that all carry the SSOP name. Sources: TI drawings 4214853/B, 4220763/A, 4214846/A, 4220784/D.

Three drawings, one word, a 1.5:1 spread in maximum height and no interchangeability among them. Distributor parametric filters carry the ambiguity downstream: RS lists TI’s SN74LVC2G66DCTR as an 8-pin SSOP measuring 2.95 × 2.8 × 1.29 mm, in the same package category as a 24-pin SSOP at 8.2 × 5.3 × 1.95 mm.

The drift extends past the large vendors. Sound Semiconductor’s PSSL10 drawing is titled Plastic Shrink Small Outline Package and specifies 1.00 mm BSC pitch on a 3.8–4.0 mm body, 1.35–1.75 mm overall height, MSL 3. Its PSSL20 is 0.65 mm BSC pitch, 4.3–4.5 mm body, 6.2–6.6 mm lead span and 1.450 mm max height — TSSOP proportions wearing an SSOP label. A part described as SSOP can therefore land anywhere from 0.4 mm to 1.00 mm pitch.

SSOP against SOIC and TSSOP on the same die

Cross-vendor package comparisons are unreliable because the die changes with the vendor. The table below holds the die constant: every figure is from one datasheet, TI SCLS041J for the SN74HC595.

Package (TI code)	Body, nom (mm)	Pitch (mm)	Max height (mm)	θJA (°C/W)	Units per reel	Tape width / pocket pitch (mm)
SSOP (DB)	6.20 × 5.30	0.65	2.00	82	2000	16.0 / 12.0
SOIC (D)	9.90 × 3.90	1.27	—	73	2500	16.0 / 8.0
SOIC wide (DW)	10.30 × 7.50	1.27	2.65	57	2000	16.0 / 12.0
SOP (NS)	10.2 × 5.3	1.27	2.00	64	2000	16.2 / 12.0
TSSOP (PW)	5.00 × 4.40	0.65	1.20	108	2000	12.0 / 8.0
PDIP (N)	19.31 × 6.35	2.54	—	67	25 per tube	—

Table 3. One die, six packages. Source: Texas Instruments SN74HC595 datasheet SCLS041J, thermal information and packaging tables.

The thermal column is where designs get into trouble. Shrinking the outline raises junction-to-ambient resistance because the leadframe and paddle carry most of the heat out of the die. Work an example at 0.5 W dissipation and 85 °C ambient: the SOIC part reaches 85 + 0.5 × 73 = 121.5 °C junction, the SSOP part 126 °C, and the TSSOP part 139 °C against a 150 °C absolute maximum junction temperature. Fourteen degrees of margin disappear on a package swap that changes nothing else.

Amkor’s characterization on its own 28-lead 5.3 × 10.2 mm SSOP shows how much airflow recovers: 49.0 °C/W in still air, 36.0 °C/W at 200 LFPM and 30.0 °C/W at 500 LFPM. For signal integrity work, the same datasheet gives 2.510 nH longest-lead inductance and 0.928 nH shortest at 100 MHz on the 28-lead 5.3 × 10.2 mm body.

One geometric point that surprises people: the DB0016A SSOP and the NS0016A 1.27 mm-pitch SOP share the same 7.4–8.2 mm lead span and the same 7.0 mm land row spacing. The shrink buys length, and it leaves width alone.

[IMAGE 2: side-by-side outline comparison of SSOP-16, SOIC-16 and TSSOP-16 at true scale | alt: “SSOP package compared with SOIC and TSSOP outlines at 16 leads”]

Land pattern, stencil, and the board area you save

TI publishes an example land pattern with each drawing. For DB0016A: sixteen pads of 1.85 mm × 0.45 mm on 0.65 mm pitch, rows 7.0 mm apart, non-solder-mask-defined preferred, with a solder paste example based on a 0.125 mm thick stencil. Run the area arithmetic against the two obvious alternatives, using the example patterns from the same datasheet.

Package (drawing)	Pad size (mm)	Pattern envelope (mm)	Land area (mm²)
SOP-16, 1.27 mm pitch (NS0016A)	1.85 × 0.6	8.85 × 9.49	84.0
SSOP-16, 0.65 mm pitch (DB0016A)	1.85 × 0.45	8.85 × 5.00	44.3
TSSOP-16, 0.65 mm pitch (PW0016A)	1.5 × 0.45	7.30 × 5.00	36.5

Table 4. Land area at 16 leads, computed from the example board layouts in TI SCLS041J.

SSOP removes 47 % of the land area against the 1.27 mm-pitch SOP of the same body width. Going further to TSSOP removes another 18 %, and costs 26 °C/W.

The stencil is not the limiting factor at this pitch. A 1.85 × 0.45 mm aperture in 0.125 mm foil gives an area ratio of (1.85 × 0.45) ÷ [2 × (1.85 + 0.45) × 0.125] = 1.45, well above the 0.66 threshold in IPC-7525B clause 3.2.1.2, and an aspect ratio of 0.45 ÷ 0.125 = 3.6. The real constraint is the 0.20 mm of bare laminate left between adjacent pads.

If you generate footprints from a library, IPC-7351B offers three density levels — Most (Level A) for hand rework, Nominal (Level B) for general production, Least (Level C) for maximum density. Level B matches TI’s published example closely enough for most work.

What goes wrong at 0.65 mm pitch

Bridging. Pads 0.45 mm wide on 0.65 mm centers leave 0.20 mm gaps. Excess paste volume, print smear, or placement error consumes that margin directly. Keep apertures 1:1 with the pad rather than oversizing them, and use non-solder-mask-defined pads, which is what the vendor drawing marks as preferred.

Coplanarity. Leads on a 5.3 mm body are long and thin — 0.22 to 0.38 mm wide with 0.05 mm minimum standoff and a 0.1 mm seating-plane callout on DB0028A. A lead bent in handling will not straighten itself in reflow. Tube-shipped product deserves incoming inspection; tape-and-reel product is better protected.

Moisture sensitivity. MSL belongs to the part, not to the outline. TI ships the SN74HC595 in DB as Level-1-260C-UNLIM with NiPdAu finish, which carries no floor-life clock. Amkor characterizes its SSOP/QSOP line at JEDEC level 3, 30 °C/60 % RH, 192 hours, and Sound Semiconductor specifies MSL 3 on its SSOP drawings. Read the bag label rather than assuming from the package name.

Rework. 0.65 mm drag-solders cleanly with flux and braid. The 0.635 mm variants on the 3.9 mm body are harder, because the shorter pads leave less landing room for the iron tip.

[IMAGE 3: SSOP-16 land pattern with pad dimensions and 0.20 mm inter-pad gap annotated | alt: “SSOP package land pattern showing 1.85 by 0.45 mm pads on 0.65 mm pitch”]

Ordering, second sources and lifecycle

Five rules keep an SSOP selection from turning into a respin.

1. Specify the outline drawing. DB0028A, PYG28, PSSL20 — the drawing number is unambiguous where the package name is not.
2. Confirm the pitch before assuming 0.65 mm. The same three letters cover 0.4 mm through 1.00 mm parts.
3. Check maximum height against the enclosure. A 2.00 mm SSOP will not drop into a slot cut for a 1.20 mm TSSOP.
4. Check carrier tape. Moving from SSOP to TSSOP on the same board changes the feeder from 16 mm to 12 mm and changes the pocket pitch.
5. Read the JEDEC reference note. DB0028A cites JEDEC registration MO-150; footprints built to MO-150 from any vendor will land.

Second sourcing across vendors within MO-150 is comparatively safe, because the registration pins pitch and lead span while body length steps predictably with lead count. Below MO-150 — the 0.635 mm and 0.4 mm registrations — assume nothing and pull both drawings side by side.

Choosing between SSOP, SOIC and TSSOP

• Height budget under 1.5 mm: TSSOP or thinner. SSOP is out at 2.00 mm maximum.
• Dissipation above roughly 0.3 W with no exposed pad: wide-body SOIC. DW measures 57 °C/W against SSOP’s 82 on the same die.
• Hand assembly, prototype spins, or field rework expected: stay at 1.27 mm pitch.
• Board area binding and height available: SSOP, and expect roughly half the land area of the equivalent 1.27 mm part.
• Migrating from an existing 1.27 mm SOP at the same body width: SSOP shortens the pattern by about 4.5 mm at 16 leads without moving the pad rows.

SSOP package FAQ

What does SSOP stand for?

SSOP stands for Shrink Small Outline Package. It describes a plastic surface-mount package with gull-wing leads on two sides and a pitch shrunk below the 1.27 mm SOIC standard. The name is a family label covering several JEDEC registrations, so it identifies a style rather than a specific set of dimensions.

What is the pitch of an SSOP package?

0.65 mm covers most SSOP parts, and that is the pitch registered under JEDEC MO-150 for the 5.3 mm body width. Variants exist at 0.635 mm under MO-137, and at 0.4 mm and 0.5 mm under MO-152 and MO-154. Some vendor drawings labelled SSOP even specify 1.00 mm. Always confirm against the drawing.

Is SSOP the same as TSSOP?

No. Height is the dividing line. TI’s SSOP DB0016A is 2 mm max height while the TSSOP PW0016A is 1.2 mm max, and the two use different body widths — 5.0–5.6 mm against 4.3–4.5 mm — despite sharing 0.65 mm pitch. TSSOP also runs hotter for the same die.

Can I fit a TSSOP part on an SSOP footprint?

Not on the 5.3 mm body version. The TSSOP-16 lead span is 6.2–6.6 mm against 7.4–8.2 mm for the SSOP-16, and the recommended land rows sit 5.8 mm apart against 7.0 mm. The TSSOP leads land more than half a millimetre short of the SSOP pads on each side.

What is the difference between SSOP and QSOP?

QSOP is a vendor name for parts built to JEDEC MO-137, 0.025 in pitch on a 0.150 in body width. Physically it is a narrow-body SSOP. Amkor lists SSOP and QSOP together on one datasheet, with the QSOP-16 referenced to MO-137 and the SSOP parts to MO-150. TI calls its MO-137-class parts SSOP anyway.

[IMAGE 4: decision flowchart from height budget and power dissipation to package choice | alt: “SSOP package selection flowchart comparing height and thermal constraints”]

What to do next

If the part you want exists in MO-150 SSOP and in TSSOP, and your enclosure allows 2 mm, take the SSOP: lower thermal resistance, wider leads, easier rework, at a cost of roughly 8 mm² of extra land area per 16-lead device. Choose TSSOP when height is the binding constraint and the thermal budget has 25 °C/W of slack. Stay at 1.27 mm pitch whenever a technician will hold an iron over the board in the field.

Before release, do one thing regardless of which way you go: open the vendor outline drawing, read the JEDEC reference line, and build the footprint from that drawing rather than from a library entry named after the package.

Internal links to place

• [INTERNAL LINK: TSSOP package dimensions → TSSOP pitch, body widths and exposed-pad variants]
• [INTERNAL LINK: SOIC package guide → SOIC narrow vs wide body and MS-012/MS-013]
• [INTERNAL LINK: IPC-7351 land pattern density levels → choosing Level A, B or C for fine pitch]
• [INTERNAL LINK: moisture sensitivity levels explained → MSL ratings, floor life and baking]
• [INTERNAL LINK: QFN vs SSOP → when to leave gull-wing packages behind]

External references cited

• JEDEC JEP95 MO index — https://www.jedec.org/sites/default/files/MOIND_DT.pdf
• JEDEC MO-137E registration — https://www.jedec.org/standards-documents/docs/mo-137e
• Amkor SSOP/QSOP datasheet DS360R — https://amkormarcomexternal.blob.core.windows.net/amkordotcom/wp-content/uploads/2018/02/SSOP-QSOP_DS360.pdf
• TI SN74HC595 datasheet SCLS041J — https://www.ti.com/lit/ds/symlink/sn74hc595.pdf
• TI DB0028A mechanical drawing 4214853/B — https://www.ti.com/lit/ml/mpds510a/mpds510a.pdf
• Renesas PYG28 outline PSC-4032-04 — https://www.renesas.com/en/document/psc/package-outline-drawing-package-code-pyg28-28-ssop-53-mm-body-065mm-pitch