An HQFP package is a quad flat package with metal added to move heat out of the die faster than the leads alone can. The H prefix denotes a heat sink. That is where the agreement ends: the name covers at least five different internal constructions, and they range from a 15% improvement to more than doubling the power the die can dissipate. Read the drawing before you trust the acronym.

Key takeaways

• HQFP is a style class, not a specific package outline.
• Five constructions share the name: fused lead, die-pad heat spreader, drop-in heat spreader, drop-in or integral heat slug, and exposed die pad.
• Only some of them expose metal you can solder to. Several do not.
• The limiting thermal resistance is the molding compound between the die pad and the inner lead tips, not the leadframe alloy.
• Measured on a 304-lead MQFP, internal enhancements cut θJA by 53% to 62%.

What HQFP means

HQFP stands for heat-sink quad flat package: a gull-wing QFP with additional metal — a spreader, a slug, or an exposed die pad — routing heat from the die toward the board or the case. It is a descriptive family, not a registered outline, so the construction has to be read off the package drawing.

[IMAGE 1: five cross-sections side by side showing fused lead, die-pad heat spreader, drop-in heat spreader, drop-in heat slug and exposed die pad constructions | alt: “HQFP package cross-sections comparing heat spreader, heat slug and exposed die pad constructions”]

Vendor metadata confirms the umbrella reading. NXP’s package summary for SOT1435-1 lists the package style descriptive code as HQFP (thermal enhanced quad flat package) while the package type code is HX2QFN16 — a no-lead part. HQFP is the class; HLQFP, HTQFP and the rest are the members. The same ambiguity shows inside a single document: NXP’s SOT470-4 is titled HLQFP100, but its outline figure is labelled HQFP100.

Two documented meanings, and how to tell them apart

Most pages define HQFP one of two ways, and both are in use.

The first is added internal metal — a spreader or slug — sometimes exposed at the package surface. The second is a lead-based approach: thicker pins, usually located centrally, replace some standard thin pins and are soldered to larger copper pads on the PCB. That is the fused-lead construction, and it needs a different footprint from a thermal land.

Tell them apart from the bottom view. Exposed metal in the centre means a slug or die pad. No exposed metal, but a group of wider or doubled leads mid-side, means fused leads. Datasheets often flag the first case with a suffix: NXP denotes the exposed pad version with -EP, and describes the pad as acting as a ground connection and/or a heat sink.

The five constructions sold under one name

Construction	What it is	Metal exposed?	Solderable to PCB?
Fused lead	Selected leads tied to the die pad	No	Through the leads only
Die-pad heat spreader	The spreader replaces the leadframe die pad	Usually not	No
Drop-in heat spreader	A thin plate encased in the molding compound during assembly	No	No
Drop-in heat slug	A thicker plate whose bottom surface remains exposed after assembly	Yes	Often not — see below
Exposed die pad	Deep down-set leadframe pad flush with the body	Yes	Yes, by design

One trap sits in the fourth row. TI’s packaging work notes that a limitation of the heat-slug approach is the inability to solder the exposed portion of the metal slug to a PCB thermal land, since many viable metal slug versions do not have a solderable surface finish. Exposed metal is not the same as a solderable pad. Check the finish before you draw a thermal land under it.

Trade names track these constructions. Amkor markets the MQFP with a drop-in heat slug as PowerQuad4, and the integral heat slug version — where the die is attached directly to the slug with adhesive tape and the leadframe carries no pad — as PowerQuad2.

What each construction is actually worth

Package and construction	θJA	θJC	Baseline for comparison
100-pin MQFP, 14 × 20 × 2.70 mm, fused lead	38 °C/W	7 °C/W	48–60 °C/W plain, same body
160-pin MQFP, 28 × 28 × 3.50 mm, die-pad heat spreader	30 °C/W	9 °C/W	37 °C/W plain, same body
208-pin MQFP, 28 × 28 × 3.50 mm, drop-in heat spreader	27 °C/W	9 °C/W	34 °C/W plain, same body
144-lead LQFP, exposed pad soldered	15.68 °C/W	0.13 °C/W	27.52 °C/W with the pad unsoldered

The first three rows come from the Cirrus Logic Package Information Guide v5.0, June 2001, measured in still air at 50% PCB metallization with TA = 70 °C and TJ = 125 °C. The fourth is TI’s modeled PowerPAD data on the recommended board.

Two readings fall out. Internal spreaders buy roughly 20% off θJA. Exposing solderable metal and attaching it buys far more, because it replaces a plastic path with a metal one — TI measures the heat split changing from 80% conduction through the leads on a standard package to 87% conduction on an exposed-pad package, of which 77% goes straight into the board.

Published test data agrees on the ceiling. Across drop-in heat spreader, drop-in heat slug and integral heat slug variants of a 304-lead 40 mm MQFP, the reduction in θJA runs between 53% and 62%, and the 62% case more than doubles the power the die can dissipate.

Why the gap matters more than the copper

[IMAGE 2: internal plan view of a QFP showing the die pad, the gap to the inner lead tips, and the molding compound path between them | alt: “HQFP package internal view showing the pad to inner lead tip gap that limits thermal performance”]

Engineers reach for a better leadframe alloy. The data says spend the effort elsewhere. The limiting factor in a leaded package is the thermal resistance of the molding compound between the pad and the leads.

Three published sensitivities make the point, all from Electronics Cooling’s leadframe analysis:

• θJA rises about 14 °C/W for every millimetre of increase in the gap between the die pad and the inner lead tips, on a 28 mm 160-lead QFP. The normal gap is 0.7 mm to 1.0 mm.
• Nearly doubling leadframe thermal conductivity from 170 to 301 W/m·°C reduces θJA by only about 1 °C/W, on a 176-lead 24 mm TQFP.
• θJA falls about 1 °C/W for each millimetre of increase in pad size, on a 208-lead 28 mm TQFP.

Run the arithmetic. Moving across the normal gap range, from 0.7 mm to 1.0 mm, costs roughly 4.2 °C/W. Doubling the copper grade buys back about 1 °C/W. The geometry inside the mold is worth around four times what the alloy is worth — which is exactly why every enhanced construction works by inserting metal across that gap rather than by improving the leads.

One more option is easy to miss. A molding compound with thermal conductivity around four times that of the standard silica-filled material can reach performance comparable to the drop-in heat spreader, with no metal added at all.

The JEDEC outlines behind the name

If you need something citable on a drawing, cite one of these rather than “HQFP.”

Outline	Registered title	Issue	Date
MO-173	TFH-PQFP-G/TQHS Thin Quad Heat Spreader Family Registration	A	October 1995
MO-189	Plastic Quad Flat Heat Slug Package (2.0 mm thick, 2.00 mm footprint, quad and dual-sided leads)	A	March 1996
MO-188	Power PQFP Heat Slug Package (H-PQFP-G)	B	February 2000
MS-026	Low/Thin Profile Plastic Quad Flat Package, 2.00 mm footprint, optional heat slug	D	January 2001
MO-204	Plastic Quad Flat Package Outline With Exposed Heat Sink	B	May 2001

Note the split in the JEDEC titles themselves: heat spreader, heat slug and exposed heat sink are three registered families, not synonyms.

Four mistakes that cause returns

1. Drawing a thermal land under a non-solderable slug. Exposed metal without a solderable finish gives you paste with nowhere to go.
2. Assuming HQFP means exposed pad. Two of the five constructions expose nothing; a fused-lead part needs copper under the leads, not the body.
3. Specifying a premium leadframe alloy for thermal reasons. Roughly 1 °C/W for a doubling of conductivity. Spend the money on board copper.
4. Comparing θJA figures across sources. Board construction dominates the number. Compare only within one document, on one board.

HQFP FAQ

What does HQFP stand for?

HQFP stands for heat-sink quad flat package: a gull-wing QFP with added metal to improve heat flow out of the die. It is a family description rather than a registered outline, and vendors use it as a style class covering several distinct constructions. NXP, for example, applies HQFP as a package style code across both leaded and no-lead thermally enhanced parts.

Is HQFP the same as HLQFP or HTQFP?

Not quite — they are members of it. HLQFP is the low-profile body version and HTQFP the thin-body version, both normally with an exposed die pad. HQFP is the umbrella. NXP documents show the overlap directly: one package drawing is titled HLQFP100 while the figure inside it is labelled HQFP100.

Does the heat slug on an HQFP have to be soldered?

Only if it can be. An exposed die pad is designed to be soldered and loses most of its benefit if it is not. A drop-in heat slug is different: many slug finishes are not solderable, and TI notes this as a specific limitation of the approach. Confirm the surface finish on the package drawing before designing a land.

How much does a heat slug actually improve thermal performance?

On a 304-lead 40 mm MQFP, published test data puts the θJA reduction from drop-in heat spreader, drop-in heat slug and integral heat slug constructions at 53% to 62% against the standard package. The 62% case more than doubles the power the die can dissipate. Internal spreaders on smaller MQFPs typically deliver closer to 20%.

What to do next

Do not order against the acronym. Pull the package drawing, look at the bottom view, and classify the part into one of the five constructions — that single step tells you whether you are designing a thermal land, a fused-lead copper pour, or nothing at all. Then take θJA from the device datasheet rather than a family figure, and check whether the quoted number assumes the metal is attached. If the part exposes solderable metal, treat it as an exposed-pad design and follow that footprint discipline. If it does not, your thermal budget has to come from board copper and airflow, because the package has already given you everything it will.

Internal links

• [INTERNAL LINK: HLQFP and exposed-pad LQFP → land pattern, stencil and thermal via design]
• [INTERNAL LINK: LQFP package guide → body thickness, pitch and footprint basics]
• [INTERNAL LINK: θJA, θJC and ΨJT explained → reading thermal metrics on a datasheet]
• [INTERNAL LINK: JEDEC package outline numbering → how to read MS and MO designations]
• [INTERNAL LINK: QFN vs QFP thermal packages → choosing between leadless and leaded]

Sources

• Electronics Cooling, B. Guenin, Packaging: designing for thermal performance: https://www.electronics-cooling.com/1997/05/packaging-designing-for-thermal-performance/
• NXP, SOT1435-1 package information: https://www.nxp.com/docs/en/package-information/SOT1435-1.pdf
• Texas Instruments, SNOA921, PowerPAD thermally enhanced plastic packages: https://www.ti.com/lit/an/snoa921/snoa921.pdf
• Cirrus Logic, Package Information Guide v5.0: https://d3uzseaevmutz1.cloudfront.net/pubs/misc/PackageGuide5.pdf
• JEDEC, Master Index for JEDEC Publication No. 95: https://www.jedec.org/sites/default/files/Master.pdf