Editorial Team - PCB Directory
Jan 20, 2023
A QFN (Quad-Flat-No-Lead) package is a semiconductor package used to connect an ASIC (application-specific integrated circuit) to a PCB using the Surface-Mount Technology. It is a small, lead-free package that provides average heat dissipation in the PCBs. QFN is a lead frame-based package, also known as a CSP (Chip Scale Package) that allows leads to be seen and touched after assembly.
The QFN packages go by different names depending on the manufacturer, such as MLF (micro lead frames) and FL (flat no lead).
Structure of a QFN Package
The die in the QFN Package is enclosed in a lead frame. The copper alloy that makes up the lead frame has a matte tin coating. Wire bonding is used to affix the die and frame together. Flip-chip technology is employed by some manufacturers for this interconnection because it provides superior electrical performance to the traditional one. The bottom surfaces have metalized terminal pads. These terminal pads offer electrical connections to the PCB and are located along the bottom surface's four edges.
An exposed pad is located on the package's bottom side. This pad offers the PCB an effective heat path and also allows for ground connection. The exposed pad is soldered to the circuit board. QFNs can operate at 2–3W without the need for forced air cooling.
The epoxy material used to secure the die to the exposed pad is known as the die attach.
Types of QFN Packages
Punch-Type: The package is formed into a single mould cavity and separated using a punch tool in punch-type singulation. This means that when using this technique, only one package is moulded into shape.
Sawn-Type: The mould array process (MAP) is used to mould these containers. With this technique, numerous packages are divided into smaller pieces. The sawn-type packages are divided into individual packages with the aid of a final saw process.
Plastic-Molded QFNs: This package is quite affordable. The two components of the plastic-molded QFN are a copper lead frame and a plastic compound; it lacks a lid. However, it is only compatible with applications that use 2 to 3 GHz.
Air-Cavity QFN: The package of this QFN has an air cavity. It also has three components: a copper lead frame, a plastic-molded body, and a lid made of ceramic or plastic (without seal and opened). Furthermore, due to the nature of its construction, this type of QFN is expensive. However, it can be utilized for microwave applications between 20 and 25 GHz.
Flip Chip QFN: The flip-chip is moulded into a low-cost package. Additionally, the box connects flip-chips to a substrate (copper lead frame). It is the best Quad Flat No-Lead for electrical performance because of its short electrical path.
Wire Bond QFN: This package is directly connected to PCB tracks, semiconductors, or integrated circuits via wires to the chip terminals.
The fundamental procedures for the surface-mount assembly of the QFN components are as follows:
Advantages of QFN Packages
Drawbacks of QFN Packages
The QFN is an excellent package, but it has certain drawbacks which include:
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