The gullwing lead
cannot wet all of the excessive solder volume, and the excess flows off the SMT pad, bridging to the adjacent pad.
While it has been observed on fine-pitch QFPs, the gullwing lead
has more resilience and resistance to stress than the C-5 and C-4 attachment types.
As a result, the gullwing lead
will heat faster and stay at a higher temperature throughout reflow.
This gullwing lead
(FIGURE 1) shows variation in the plated surfaces.
The QFP, which is similar to the PLCC but has a denser I/O array of gullwing leads
, is typically used for packages of 150 leads.
004" offset may be noticeable on gullwing leads
, but could likely go undetected on chip components.