is the disbonding or detachment of the die from its die pad or die
die lifting is commonly referred to as a
types: 1) die lifting caused by a fracture within the die attach
material itself (cohesion failure); 2) die lifting due to delamination
between the die backside and the die attach material (adhesion failure);
or 3) die lifting due to delamination between the die attach material
and the die pad or cavity (adhesion failure).
Determining which of these mechanisms is predominant in a die
lifting issue is important in preventing its recurrence.
voids, insufficient fillet formation, and inadequate bond line thickness
of the die attach material,
which can lead to its
once the unit is
subjected to thermo-mechanical stresses. When this happens, the die
attach material fractures in the middle and results in die lifting, leaving die attach material
still sticking on both the die backside and the die pad. The
degradation of the mechanical strength of the die attach material can
also be due to: 1) contamination; 2) chemical degradation with time; and
3) chemical degradation from external factors, e.g., moisture,
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SEM photo of a lifted die
insufficient die attach fillet
can also be
caused by the aforementioned issues, i.e.,
excessive die attach voids, insufficient fillet formation, inadequate
bond line thickness, and die attach material problems.
However, they are also frequently encountered when contaminants are
present on the attachment surface. Thus, contaminants
on the die backside can lead to die attach-to-die delamination, while contaminants
on the die pad can lead to die attach-to-die pad
delamination. Either way, the resulting delamination can lead to die
lifting. Eutectic die attach delaminations may also be due to inadequate scrubbing, incorrect preform
size, and improper equipment settings.
die attach fillet formation and
die attach voids act as
that can also result in contiguous cracks at the backside of the die, especially in units that
use eutectic die attach. These cracks can propagate to a point wherein
the upper part of the die is separated from the bottom part. If the
bottom part of the die is still attached to the die attach system, then
this, technically, is still a
although extreme cases indeed give the impression that the die has
lifted off from its resting place.
accelerated by SHRT,
Temp Cycle, and Thermal Shock.
Die Crack FA
Die Attach; Failure Analysis
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