A QSOP-16 package has a 4.80 mm to 5.00 mm body, a 5.79 mm to 6.20 mm lead span and 16 gull-wing leads on a 0.635 mm pitch, registered as JEDEC MO-137 variation AB. Three suppliers publish recommended land patterns for it and they do not agree. This page gives the outline, compares those patterns, and shows what the differences do to your toe fillet, solder mask and paste volume.

[IMAGE 1: QSOP-16 outline with body length, lead span, height and 0.635 mm pitch dimensioned, and the three published land patterns overlaid in different colors | alt: “QSOP-16 package dimensions and land pattern with 0.635 mm pitch”]

Key takeaways

• Outline is JEDEC MO-137-AB. Body 4.80 – 5.00 mm, lead span 5.79 – 6.20 mm, height 1.75 mm max, pitch 0.635 mm.
• Published land patterns run from 1.45 mm × 0.35 mm pads (Diodes) to 1.6 mm × 0.41 mm (TI).
• TI’s pattern is roughly an IPC-7351 nominal geometry; the Diodes pattern is closer to a least-material footprint.
• With TI’s 0.41 mm pad and 0.05 mm mask relief, the mask dam is 0.125 mm — barely above the 0.1 mm most fabricators guarantee.

QSOP-16 dimensions

A QSOP-16 measures 4.80 mm to 5.00 mm long and 3.81 mm to 3.99 mm wide across the body, spans 5.79 mm to 6.20 mm across the lead tips, and stands 1.75 mm tall at maximum, with 16 gull-wing leads on a 0.635 mm pitch. Both the Analog Devices RQ-16 and Diodes drawings cite JEDEC MO-137.

Dimension	Analog Devices RQ-16	Diodes QSOP-16	Texas Instruments DBQ0016A
Body length, D	4.80 – 5.00 mm	4.80 – 5.00 mm	4.81 – 5.00 mm
Body width, E1	3.81 – 3.99 mm	3.81 – 3.99 mm	3.81 – 3.98 mm
Lead span, E	5.79 – 6.20 mm	5.79 – 6.20 mm	5.80 – 6.19 mm
Height, A	1.35 – 1.75 mm	1.55 – 1.73 mm	1.75 max
Lead width, b	0.20 – 0.30 mm	0.20 – 0.30 mm	0.21 – 0.30 mm
Foot length, L	0.41 – 1.27 mm	0.41 – 1.27 mm	0.41 – 0.88 mm
Pitch, e	0.635 BSC	0.635 BSC	0.635
Weight	Not stated	0.0813 g approx.	Not stated

Table 1. QSOP-16 outline from three supplier drawings. The envelope agrees; the foot-length tolerance does not, and TI’s tighter 0.88 mm maximum is what its land pattern is drawn against.

Three published land patterns, compared

Land pattern parameter	Diodes	Renesas M16.15B	Texas Instruments DBQ0016A
Pad size	1.450 × 0.350 mm	1.53 × 0.38 mm	1.6 × 0.41 mm
Pad pitch	0.635 mm	0.635 mm	0.635 mm
Span across pad outer edges	6.400 mm	Not stated directly	7.0 mm (derived)
Span across pad inner edges	3.500 mm (derived)	Not stated directly	3.8 mm (derived)
Copper gap between adjacent pads	0.285 mm (derived)	0.255 mm (derived)	0.225 mm (derived)

Table 2. Published land patterns for the QSOP-16. Values marked derived are arithmetic on the published figures, not printed on the drawings. TI states a 5.4 mm dimension across the pattern; read as the span between opposing pad centers it gives the 7.0 mm and 3.8 mm figures above.

The spread is larger than it looks. Against a 6.19 mm maximum lead span, the TI pattern leaves about 0.40 mm of pad beyond the lead tip; the Diodes pattern leaves 0.10 mm. That is the difference between a visible toe fillet and one an inspector takes on trust.

The same TI drawing set confirms the reading. Its TSSOP-16 example uses a 5.8 mm span with 1.5 mm pads against a 6.6 mm maximum lead span, giving 0.35 mm of toe land — the IPC-7351 nominal solder-joint goal. TI draws to nominal; Diodes draws closer to least.

Pick on assembly, not preference. Use the TI geometry for hand rework, low volume or visual toe inspection; use the Diodes geometry when routing between the rows is tight. Do not mix the outer span from one with the inner span from the other — the two sit 0.45 mm apart along the board, so a hybrid puts the heel in the wrong place.

Solder mask and stencil at 0.635 mm pitch

Mask dams break first. TI specifies 0.05 mm of mask relief around its 0.41 mm pad, opening the mask to 0.51 mm and leaving a 0.125 mm dam. Most fabricators guarantee 0.1 mm and slivers under 0.075 mm lift during processing, so that leaves about 0.025 mm of margin. The 0.35 mm Diodes pad under the same relief gives a 0.185 mm dam.

Stencils are easier. TI shows apertures 1:1 with the pads on a 0.127 mm foil, giving an area ratio near 1.29 for the TI pad and 1.11 for the Diodes pad, both well above the 0.66 release threshold. The TI aperture deposits about 29% more paste per joint.

For wave soldering, Diodes notes that adding 0.2 mm to the span gives a more robust pattern. Reflow is still the better process at this pitch.

[IMAGE 2: close-up of two adjacent QSOP-16 pads showing copper pad, solder mask opening and the resulting dam width, dimensioned for the 0.41 mm and 0.35 mm pad cases | alt: “QSOP-16 land pattern solder mask dam width at 0.635 mm pitch”]

Thermal: one device, four packages

Cross-package thermal comparisons are usually apples to oranges. The TI TS5V330 publishes all four options for the same die, per JESD 51-7.

Package	TI designator	θJA
SOIC-16	D	73 °C/W
QSOP-16	DBQ	90 °C/W
TSSOP-16	PW	108 °C/W
VQFN-16	RGY	39 °C/W

Table 3. Junction-to-ambient thermal resistance for one device in four packages, from the TI TS5V330 data sheet, revision D. The VQFN figure is calculated per JESD 51-5.

The QSOP sits between the SOIC and the TSSOP, as the lead cross-section predicts. At 90 °C/W a part dissipating 300 mW runs 27 °C above ambient: fine at 25 °C, marginal at 85 °C against a 125 °C limit.

A lifecycle note from the same document: that device’s QSOP version is marked obsolete while the TSSOP version stays in production. Check part status before committing a footprint.

Frequently asked questions

What are the QSOP-16 dimensions?

The body is 4.80 mm to 5.00 mm long and 3.81 mm to 3.99 mm wide, the lead span is 5.79 mm to 6.20 mm, and maximum height is 1.75 mm. Lead pitch is 0.635 mm and lead width is 0.20 mm to 0.30 mm, per JEDEC MO-137 variation AB.

What land pattern should I use for a QSOP-16?

Start from one supplier drawing rather than averaging several. TI publishes 1.6 mm by 0.41 mm pads on a 0.635 mm pitch with a 5.4 mm span; Diodes publishes 1.45 mm by 0.35 mm with a 6.4 mm outer span. The TI geometry gives more toe fillet, the Diodes geometry more routing room.

What is the QSOP-16 pad pitch?

A basic 0.635 mm, equal to 0.025 in. That places it just above the 0.625 mm threshold IPC-7351B uses to separate its two gull-wing land pattern tables, so the wider-pitch side fillet goals apply.

Is a QSOP-16 footprint the same as an SSOP-16?

It is the same as a narrow-body SSOP-16 on the MO-137 outline, which is what most suppliers mean. It is not the same as an SSOP-16 on a 5.3 mm body and 0.65 mm pitch, which is a different registration and a different footprint.

What to do next

Pull the drawing for the exact part you are buying, not a generic QSOP-16, and check three numbers: 0.635 mm pitch, 5.79 mm to 6.20 mm lead span, and the foot-length maximum, where suppliers differ. Build the land pattern from that one drawing and record its revision on the library part.

Before release, run a mask-dam check at 0.1 mm and confirm your fabricator holds it. If the dam fails, the fix is the smaller pad, not a smaller mask relief.