Die Shear Testing is the process of determining the strength of adhesion of a semiconductor die to the package's die attach substrate (such as the die pad of a lead frame or the cavity of a hermetic package), by subjecting the die to a stress that's parallel to the plane of die attach substrate, resulting in a shearing stress between: 1) the die-die attach material interface; and 2) the die attach material-substrate interface.
The general purpose of die shear testing is to assess the over-all quality of the die attach process, including the integrity of the materials and the capabilities of the processes used in mounting the die (and other elements, if any) to the package substrate. Mil-Std-883 Method 2019 is the most widely-used industry standard for performing this test.
A typical die shear tester consists of: 1) a mechanism that applies the correct load to the die with an accuracy of +/- 5% of full scale or 50 g, whichever tolerance is greater; 2) a die contact tool which makes the actual contact with the full length of the die edge to apply the force uniformly from one end of the edge to the other; 3) provisions to ensure that the die contact tool is perpendicular to the die attach plane; 4) provisions to ensure that the fixture holding the die may be rotated with respect to the contact tool so that the die edge and contact tool may always be aligned in parallel to each other; and 5) a binocular microscope (10X min magnification) and lighting system to facilitate the observation of the die and contact tool while the test is being performed.
The force applied to the die during die shear testing must be sufficient to shear the die from its mounting or twice the lower specification limit for the die shear strength, whichever occurs first. The direction of the applied force must be perpendicular to the die edge and parallel to the die attach or substrate plane. After the initial contact has been made and the application of force starts, the relative position of the tool must not change vertically, i.e., it must be prevented from contacting either the die attach material or the substrate.
Failures from die shear testing include: 1) failure to meet the specified die shear strength requirements; 2) a separation that occurs at less than 1.25X the minimum die shear strength and evidence of less than 50% adhesion of the die attach material; and 3) a separation that occurs at less than 2X the minimum die shear strength and evidence of less than 10% adhesion of the die attach material.
The mode of separation must also be classified into and recorded as any of the following: 1) shearing of the die itself with silicon remaining; 2) separation of the die from the die attach material; and 3) separation of both the die and die attach material from the package substrate.
The die shear strength requirements are plotted in Figure 2019.4 of Mil-Std-883 Method 2019.
