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Mechanical Failure Mechanisms
Published in Judy Pecht, Michael Pecht, Long-Term Non-Operating Reliability of Electronic Products, 2019
The die, substrate, leadframe, and case of a microelectronic package typically have different thermal expansion coefficients. For example, dies are usually made of silicon, gallium arsenide, or indium phosphide, while the substrate is typically alumina, beryllia, or copper, with a coefficient of thermal expansion different from the die material. During temperature cycling, tensile stresses develop in the central portion of the die and shear stresses develop at the edges. Ultimate fracture of the brittle die can occur suddenly and without any plastic deformation when surface cracks at the center or edge of the die reach critical size and propagate during thermal cycling.
Thermomechanical Analysis and Design
Published in Michael Pecht, Handbook of Electronic Package Design, 2018
Fatigue damage is also observed in the die itself. Figure 8.19 shows an example of a fatigue crack that has propagated through the active area of a ceramic die. Vertical die cracks often result from excessive voids in the die attach, as shown by X-ray radiography methods in Figure 8.20. The die typically consists of several different materials, such as silicon, silicon dioxide, and gallium arsenide. Most of these are brittle materials and fail by brittle fracture mechanisms [36] under thermomechanical residual and cyclic stresses from manufacturing and operational loads. Fatigue design of these components can, therefore, be successfully addressed by fracture mechanics tools, such as Paris’ fatigue crack propagation law given in Eqn. (8.50) [37]. Of course, such an analysis would require fracture and crack propagation data that are almost nonexistent in the current literature for commonly used die materials.
Cost Requirements Cascade and Purchasing
Published in Ali Jamnia, Introduction to Product Design and Development for Engineers, 2018
Table 15.6 provides an estimate of processing time for each bracket design. Bracket A may be machined from a block of aluminum. This process involves removing nearly 80% of the material from a blank piece. It is both costly and time consuming. Alternatively, a custom extrusion die may be made to produce a near-net-shape extrusion. These extruded parts may be machined to the net shape at a fraction of the cost. The die cost for this purpose has been estimated at about $4500. This estimate is based on previous experience and consultation with a potential supplier.
High-Speed On-Chip Signaling: Voltage or Current-Mode?
Published in IETE Journal of Research, 2021
Due to the advancement of CMOS technology, the density of transistors and the speed of integrated circuits have gone through a tremendous revolution in the last five decades [2]. The silicon industry follows Moore's law where the number of transistors integrated in a single die grows exponentially [3]. The huge number of transistors in a die has led the silicon industry to integrate all the digital, analog, and data communication modules in a single chip. However, most system-on-chips (SOCs) are interconnect limited, since the interconnect does not scale as well as the transistors. Hence, designing an interconnect within an optimal power and performance budget has become very critical for modern microprocessors.