QFN Package

When it comes to discussing chips, pins are a crucial aspect as they serve as the vital medium for physical and electrical connections between the chip and external circuits. Due to the direct impact of pin length on signal transmission performance, one often hears about a chip packaging type called QFN packaging. So, what exactly is QFN and what are its advantages? Let’s explore it together in the following content.

What is QFN Packaging

When mentioning QFN, people might immediately associate it with PLCC (Plastic Leaded Chip Carrier), but in reality, there are significant differences between them. QFN stands for Quad Flat No Leads, typically appearing in square or rectangular shapes, where “No Leads” signifies its primary feature of lacking external pins. In contrast, the pins of PLCC packaging are folded into the interior of the package, hence the pins are not visible externally, though they do exist. QFN IC chip also features one or more pads at the center of the package’s bottom, which are not only used for connecting internal chip circuits but also provide better heat dissipation capability. Multiple points surrounding the large pad are used to connect with solder paste printed on the PCB through reflow soldering.

quad flat no leads package

Advantages of QFN Packaging

When considering chip packaging, packaging efficiency is an important consideration factor, referring to the ratio of chip area to the actual package area. The closer this ratio is to 1, the higher the packaging efficiency. The packaging efficiency of QFN typically ranges from 0.3 to 0.4, and without additional heat dissipation pads at the bottom, this value can even reach 0.5, while medium-sized packages like SOP have packaging efficiency ranging from 0.1 to 0.2. If the advantage of QFN in terms of size is not intuitively perceived, comparing QFN with TQFP and SOP clearly shows that QFN packaged chips have the smallest volume and are much lighter in weight.

QFN vs. SOP and TQFP size comparison

In addition to size advantages, QFN is also highly praised for its performance. The most significant feature of this packaging is the absence of external pins, and the presence of pads at the bottom provides chips with outstanding electrical and thermal performance. With no external pins, the conductive paths in QFN are very short, resulting in low self-inductance coefficients and wire resistance inside the package, which improves electrical performance. Meanwhile, the pads at the bottom also act as heat sinks, enabling direct soldering onto the circuit board. When the chip operates, the heat generated quickly dissipates through the pads to the entire circuit board, increasing both the heat dissipation area and speed.

Furthermore, due to its powerful functions, QFN is often more expensive than other chip packages, but its cost-effectiveness advantage is often overlooked. Generally, at the same price, QFN can achieve higher performance, making it more useful in the mid-to-high-end market.

Application of QFN chip packaging in mid-to-high-end electronics market

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