QFN: Stands for Quad flat no-leads and is a type of flat no-leads package.
A flat no-leads package connects an integrated circuit firmly to a PCB or other flat surfaces, physically or electrically. DFN or dual flat no-leads are also a type of no leads package.
A through-hole technology is a technology used for the mounting of electronics components onto a PCB by the method of insertion of leads through the PCB and then soldering it. This method has its disadvantages and is replaced by the flat no-leads packaging as it allows mounting of an entire IC onto a PCB surface without any drilling or soldering issues.
A flat no-lead package incorporates a copper substrate in a planar form and is encapsulated in the form of a CSP plastic package. It has an external heating pad also known as the thermal pad that diffuses the heat out of the IC. It acts like a heat sink to reduce thermal risks. A QFN is much similar to that of a BGA (Ball grid Array), a flat plastic surface is made of a substrate material that allows mountings of ICs and other components onto it.
A flat no-leads includes a lead frame along with a wire bonding. The lead frame material usually consists of a copper alloy and an adhesive is used to connect the silicon bare die to the flat substrate pad. The adhesive is usually a thermally conducting material. A flat no-lead package can be categorized based on its design as a punch singualtion flat no-lead and saw singulation flat no-leads. In the former the entire package is moulded as per requirement into a shape, whereas the latter involves cutting a large set of packages into several mini parts.
The air cavity type flat no-leads has an inbuilt air cavity made in the package. A plastic moulded QFN comes in several prices and typically has limited applications for the less expensive ones. The entire design of an air cavity QFN has a total of three lead parts namely a lead frame made of a copper, a body moulded out of a plastic material and a lid. This type of QFN can be used in extreme situations of frequency upto 25- 30 GHz.
A complete QFN typically offers many advantages. The advantages include reduced leads, a much miniaturized (CSP) packaging, light weight, low cost of production and manufacture. It avoids any sort of drilling and heating issues related with printed circuit boards. A copper pad allows high electrical and thermal conduction thus increasing inner circuitry efficiency. When it comes to mass production of electronics goods, these above mentioned qualities of a QFN makes it the first choice of engineers to design an electronic circuit with.
There are a few well renowned electronics companies manufacturing QFN in bulk viz Atmel, Amkor technologies and more. These companies produces multiple variants of a QFN as per industry standards to meet the needs of the modern world.
A MLP, Micro leadframe package is a set of packages that includes an entire family of IC QFN to surface mount electronics components. There are many versions to this package. An MLP is a near chip scale package enclosed or encapsulated in a plastic casing with a frame of copper along with a substrate material.
The more recent innovations in the world of QFN include faster working chips and smaller sized chips. These QFN packages allowing surface mounting of ICs have made designing f electronic circuits much simpler and easier. Some of the many applications of QFN in the modern world of electronics comes from the growing demand of USB, and hard disk manufacturing.