Technical Articles From Allegro MicroSystems

Wettable Flank Plated PQFN

Apr 08, 2024 | Bradley Smith

Plastic Quad Flat Pack No-Lead (PQFN) or Quad Flat Pack No-Lead Exposed Pad (QFN-EP) packages (a.k.a. QFN) have no easily solderable, visually exposed terminations, because the package designs have terminations on the underside of the package for solder joints. The package edge has exposed copper of the termination after singulation and does not easily solder wet due to copper oxidation. Therefore, visual determination that the package has soldered effectively cannot be made optically or by x-ray. Electrical test is the only way to determine electrical connectivity of the soldered terminations. There are some applications where full electrical test of all terminations is difficult or incomplete. Thus, in high reliability applications, it may be desired to visually check for termination solder joint integrity. It is for these purposes that wettable flank, tin plated terminations of QFNs have been developed as a visual aid to the determination of board solder operation effectiveness