Wetting indicators are where the
reflowed joint is deliberately made into a different characteristic shape, when viewed in an x-ray image, compared to the shape of a typical or "standard"
reflowed BGA joint.
The solder paste has
reflowed correctly, and there is evidence on the pad of the joint and how the solder had successfully wetted up and around the contact to form a continuous fillet before the pin detached.
Components were placed on the boards and
reflowed according to treatment combination.
To wit, I noted some images showed where solder paste had not
reflowed under the devices, and there was the presence of foreign object(s), such as discrete components, trapped under the package.
Fourier transform IR spectra of the
reflowed flux residues show how reflow profile conditions and atmosphere affects the decrease of a peak around 1700 [cm.sup.-1] and the appearance and increase of another peak at 1600 [cm.sup.-1].
The paste
reflowed uniformly and covered leads per IPC-A-610D class 3 specifications.
The trace provides a path for the liquid elements of the printed solder paste and
reflowed molten solder to migrate.
Preconditioning #1: No preconditioning, assembly is
reflowed in air.
The reballed BGAs are then placed and
reflowed on the test platforms.