QFN Rework
QFN packages or Quad Flat No Leads packages physically and electrically connect integrated circuits to printed circuit boards. QFN is just one of the package technologies that can be used to connect integrated circuits to the surface of PCBs without through holes.
There are two different types of QFN, namely Air-Cavity QFNs, which has an air cavity designed into the package and Plastic-Moulded QFNs, which has the air in the package minimised. Both are recognised for their thin profile, low weight and reduced lead inductance and therefore are often chosen for applications where size, weight and thermal and electrical performance are important.
QFNs can be reworked as with any other package but each requires slightly different methods. The steps for a successful QFN rework are:
- Board preheat
- Reflow of component solder
- Vacuum removal of component
- Cleaning and preparation of PWB lands
- Screening of solder paste
- Placement and reflow of new component
- Inspection of solder joints