A QFP or Quad Flat Package is a surface mount integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 pins with a pitch ranging from 0.4 to 1.0 mm are common. Other special variants include low profile QFP and thin QFP.
A package related to QFP is PLCC which is similar but has pins with larger pitch, 1.27 mm (or 1/20 inch), curved up underneath a thicker body to simplify socketing (soldering is also possible). It is commonly used for NOR Flash memories and other programmable components.
The quad flat-pack has connections only around the periphery of the package. To increase the number of pins, the spacing was decreased from 50 mil (thousandths of an inch) (as found on small outline packages) to 20 and later 12 mil. However, this close lead spacing made solder bridges more likely and put higher demands on the soldering process and alignment of parts during assembly. The later pin grid array and ball grid array packages, by allowing connections to be made over the area of the package and not just around the edges, allowed for higher pin counts with similar package sizes, and reduced the problems with close lead spacing.
The basic form is a flat rectangular (often square) body with leads at four sides but with numerous variations in the design. These differ usually only in lead number, pitch, dimensions, and materials used (usually to improve thermal characteristics). A clear variation is Bumpered Quad Flat Package with extensions at the four corners to protect the leads against mechanical damage before the unit is soldered.
Heat sink Quad Flat Package, Heat-sink Very-thin Quad Flat-pack No-leads (HVQFN) is a package with no component leads extending from the IC. Pads are spaced along the sides of the IC with an exposed DIE that can be used as ground. Spacing between pins can vary.
A thin quad flat pack (TQFP) provides the same benefits of the metric QFP, but is thinner. Regular QFP are 2.0 to 3.8 mm thick depending on size. TQFP packages range from 32 pins with a 0.8 mm lead pitch, in a package 5 mm by 5 mm by 1 mm thick, to 256 pins, 28 mm square, 1.4 mm thick and a lead pitch of 0.4 mm.
TQFPs help solve issues such as increasing board density, die shrink programs, thin end-product profile and portability. Lead counts range from 32 to 176. Body sizes range from 5 mm x 5 mm to 20 x 20 mm. Copper lead-frames are used in TQFPs. Lead pitches available for TQFPs are 0.4 mm, 0.5 mm, 0.65 mm, 0.8 mm, and 1.0mm. PQFP, or plastic quad flat pack, is a type of QFP, as is the thinner TQFP package. PQFP packages can vary in thickness from 2.0 mm to 3.8 mm. A Low-profile Quad Flat Package is a surface mount integrated circuit package format with component leads extending from each of the four sides. Pins are numbered counter-clockwise from the index dot. Spacing between pins can vary; common spacings are 0.4, 0.5, 0.65 and 0.80 mm intervals.
Some QFP packages have an Exposed Pad. The exposed pad is an extra pad underneath or on top of the QFP that may act as a ground connection and/or as a heat sink for the package. The pad is typically 10 or more mm², and with the pad soldered down onto the ground plane heat is passed into the PCB. This exposed pad also gives a solid ground connection. These type of QFP packages often have a -EP suffix (e.g. a LQFP-EP 64), or they have an odd number of leads, (e.g. a TQFP-101).
Other quad flat package types
BQFP Bumpered Quad Flat Package
BQFPH Bumpered Quad Flat Package with heat spreader
CQFP Ceramic Quad Flat Package
EQFP Plastic Enhanced Quad Flat Package
FQFP Fine Pitch Quad Flat Package
LQFP Low Profile Quad Flat Package
MQFP Metric Quad Flat Package
NQFP Near chip-scale Quad Flat Package.
SQFP Small Quad Flat Package
TQFP Thin Quad Flat Package
VQFP Very small Quad Flat Package
VTQFP Very Thin Quad Flat Package