We’ll compare QFP vs. QFN in this article. QFP and QFN are the typical packages for mounting large chips, such as microcontrollers.
Microprocessors can utilize BGA or other complex mounting packages, but these have the challenge of escaping traces due to their high density.
However, QFP and QFN have all their contacts exposed on the chip’s edges. This design enables easy mounting and routing.
However, the two technologies have significant differences. So let’s see what they offer.
What Is QFP?
QFP is an acronym for Quad Flat Package, a surface-mount package for ICs with pins protruding from all sides. These pins have an L or seagull wing shape with a thin, flexible design.
Their thin, flexible design enhances the package-to-PCB secondary reliability. Also, the thinness enables the chip to have multiple, short electrical connections with the board while maintaining a small profile.
Generally, large or ultra-large scale chips with this mounting package have at least 256 pins, 64 on each side. Tinier chips can have as few as 32 pins, meaning eight on each side.
But you can have rectangular QFPs, meaning the number of pins might be unequal on the sides.
These tiny package dimensions combined with multiple electrical connections and low parasitic parameters make chips with QFP ideal for high-frequency applications.
A QFP-24 chip (six pins on each side)
The chip mounting packages usually have these three base materials.
And they come in different types, which include the following.
Bumpered Quad Flat Package
This QFP features extensions on all four corners to shield the pins from mechanical damage before soldering. The thin chips can easily experience damage or bending due to their fine pitch.
And repairing them is almost impossible. So the shield is a vital addition.
Bumpered Quad Flat Package with Heat Spreaders
As you can tell, these QFPs are modified versions of the bumper type. They feature heat spreaders that enhance efficiency by allowing fast heat dissipation when handling high power levels.
Ceramic Quad Flat Packages
As the name suggests, this QFP uses ceramic as the base material, improving its quality and efficiency.
A QFP chip
Fine-Pitched Quad Flat Packages
These packages have the finest pitch, resulting in a dense pin design.
Heat-Sinked Quad Flat Package
Integrated circuits generally generate a lot of heat. This heat needs an efficient dissipation path, and the pins provide an ideal avenue. However, thin leads are not efficient for dissipating heat.
So these heatsinked chips replace some thin pins with thicker ones on opposing sides. And the corresponding copper pad on the PCB is large to accommodate the wider pin. This setup dissipates heat faster than the regular thin pin QFP.
Metric Quad FlatPackage
Standard QFPs use imperial measurements to define their sizing, pin spacing, and other dimensions. But these packages have their sizing given in metric values.
Low Profile Quad Flat Package
Based on the metric system, this package is thinner than the regular QFPs; it has a thickness of around 1.4mm. Its detailed specifications include the following.
- Lead-frame footprint: 2mm
- Lead count: 32-256
- Body size: 5x5mm to 28x28mm
- Lead pitches: four variations (0.3mm, 0.4mm, 0.5mm, and 0.65mm)
A QFP chip surface mounted on a PCB
Thin Quad Flat Package
These QFPs are variants of the low-profile type but are thinner (1mm). However, their standard lead-frame footprint is the same (2mm). And the packages have a plastic base material.
Plastic Quad Flat Package
As the name suggests, these QFPs have a plastic base material.
Other types include:
- Thermally-enhanced low-profile QFP
- Small QFP
- Very small QFP
- Very thin QFP
- Near chip-scale QFP
1. QFP Advantages
- Mature chip-mounting technology
- You can use them in sockets
- Square chips can bear a high pin density (more than the rectangular type)
2. QFP Disadvantages
- I/O limited at 500MHz
- Inadequate I/O for complex chips
- Pins can get damaged easily
3. QFP Issues
QFPs are not all perfect. And the two major issues that affect this package type include the following.
Since QFPs have tiny pins with a slim pitch, they are vulnerable to damage that is almost impossible to fix.
So handle them with care in storage and during transportation. We recommend packing them in waffles to protect the pins when in transit.
PCB Density Track
These packages can have several hundred pins with tiny pitches. So consider this factor during PCB design to evade track density challenges. And take extra care when routing the signal lines to avoid violating any design rule.
A circuit board with a mounting pad for a chip bearing a QFP package
What Is QFN?
QFN stands for Quad Flat No-lead package. So its most obvious difference compared to QFP is that it lacks mounting pins. Also known as Small Outline No-leads (SON) or Micro Lead Frame (MLF), QFN is a near-chip-scale enveloped package. This encapsulated package has a planar copper-lead frame substrate with a matt tin coating.
The lack of pins makes this surface mounting package thin but with limited heat dissipation. So they usually have thermal pads to transfer heat to the PCB for quick cooling.
A QFN mounting pad on a PCB (note the center-positioned thermal pad to enhance heat dissipation)
QFNs can either have single or multi-contact rows, not both. Creating the single-row type involves using the saw and punch singulation processes.
The two split extensive package collections into single packages.
On the other hand, multi-contact rows undergo copper etching to create the required rows and pins.
QFNs are available in the following types.
As the name suggests, these packages have a plastic composite compound. Also, they have copper-lead frames but no lids. The applications for this QFN lie in the range of 2-3 GHz.
Air Cavity QFN
These QFNs contain an air cavity in the package. And they comprise a copper-lead frame, ceramic or plastic lead, and a plastic body. You can open this body with or without a seal.
Although more expensive than the plastic-molded type, air cavity QFNs have a broader application range (20-25 GHz).
These QFNs have a punch-tool-split single-mold cavity. But you can get them as molded single packages.
A QFN chip mounted on a board
Wettable Flank QFN
As the name suggests, these packages feature an elevated base that reflects the solder wetting. So you can inspect the pads to ensure they sit and mount accurately on the board.
Flip Chip QFN
These QFNs exclusively use flip-chip technology to link the silicon die and copper-lead frame. This connection creates a shorter path between the two.
Sawn Type Packages
This name refers to the QFN-creation process. Making the package involves splitting a large box into tiny pieces, then sorting these “sawn types” to create the package.
Wire Bond QFN
Wire-bond packages link the IC’s terminals to the PCB tracks directly using wires.
- Thin profile
- Short wires
- No lead coplanarity issues
- Low lead inductance
- Does not need specialized surface mounting equipment
A tiny, low-profile QFN chip
These packages have three primary issues.
QFN packages are challenging to install in high-mix, low-volume scenarios because they make the board and stencil design more complex. This issue arises from their high error rates during component placement and reflow soldering.
So always stick to the manufacturer’s guidelines by creating precise apertures and stencil thicknesses. If the stencil is too thick, you will apply a lot of solder. The typical thickness should be 2-3 mils.
With the aperture pad, ensure a 0.8:1 ratio with multiple tiny apertures. And the bond-pad design should lie 0.2-0.3mm away from the package footprint.
OEM Processes Compatibility Issues
These packages can experience board or component dimensional changes because they don’t have leads.
So they are not as robust when you expose them to OEM processes.
Also, circuit boards flex at times. So you’ll subject the package to high stress if you do PCB in-circuit testing or board attachment.
Usually, the leads absorb these stresses because they can flex. But they are unavailable in this package.
The slim pad-to-pad pitch in these packages increases the probability of solder bridging. And it will be challenging to desolder the QFN to rectify the solder joint issue.
QFP vs. QFN: Leads
QFPs feature L-shaped pin leads that extend on all four sides. But QFN packages don’t have pin leads; they have metalized pads. But both have these contact points on all four chip sides.
A chip with protruding pins vs. one with flat edges
QFP vs. QFN: Pin Count
Due to their thin pin pitches, QFPs can have hundreds of pins, resulting in 8-70 on each side. But QFNs have a few contact leads (usually eight) and a thermal pad.
QFP vs. QFN: Assembly Process
The differences in pins vs. pad electrical contact points make the assembly processes for these two packages different.
QFPs have pins that tend to self-align during placement and soldering. So they don’t need inspection pre-soldering (after component placement) and post-soldering.
An IC with QFP packaging mounted in a printed circuit board
However, QFNs don’t have pins. So they need careful placement followed by an inspection. After that, they go into the oven for reflow soldering, then undergo another inspection process to ensure the welding is in alignment.
A blank PCB with several mounting pads for QFP chips
As you can see, these pinned and unpinned IC surface mounting packages introduce multiple differences.
Also, they bring about varying advantages and disadvantages that affect soldering, electrical properties, and thermal performance.
We hope this comparison will help you pick the most suitable surface-mount IC package for your board. If you need further clarification, contact us for more details.