Microelectronic devices generally have a die (i.e., a chip) that includes integrated circuitry having a high density of very small components. In a typical process, a large number of dies are manufactured on a single wafer using many different processes that may be repeated at various stages (e.g., implanting, doping, photolithography, chemical vapor deposition, plasma vapor deposition, plating, planarizing, etching, etc.). The dies typically include an array of very small bond-pads electrically coupled to the integrated circuitry. The bond-pads are the external electrical contacts on the die through which the supply voltage, signals, etc., are transmitted to and from the integrated circuitry. The dies are then separated from one another (i.e., singulated) by dicing the wafer and backgrinding the individual dies. After the dies have been singulated, they are typically “packaged” to couple the bond-pads to a larger array of electrical terminals that can be more easily coupled to the various power supply lines, signal lines, and ground lines.
An individual die can be packaged by electrically coupling the bond-pads on the die to arrays of pins, ball-pads, or other types of electrical terminals, and then encapsulating the die to protect it from environmental factors (e.g., moisture, particulates, static electricity, and physical impact). In one application, the bond-pads are electrically connected to contacts on an interposer substrate that has an array of ball-pads. FIG. 1A schematically illustrates a packaged microelectronic device 10 including an interposer substrate 20 having an array of ball-pads 22 and a microelectronic die 30 attached to the interposer substrate 20. The microelectronic die 30 has been encapsulated with a casing 40 to protect the die 30 from environmental factors.
One drawback of this conventional arrangement is that stresses within the device 10 can cause bowing or warpage of the device after encapsulation. FIG. 1B, for example, is a highly exaggerated view of the device 10 after the device has bowed. The bowing can be caused by several factors, such as asymmetrical stress distribution within the device caused by the difference between the coefficients of thermal expansion of the interposer substrate 20, the microelectronic die 30, and the casing 40. The warpage of the interposer substrate 20 can cause failure in solder links between the interposer substrate 20 and a printed circuit board (not shown) to which the interposer substrate 20 is attached or delamination between the die 30, the interposer substrate 20, and/or the casing 40. Accordingly, there is a need to reduce stresses in microelectronic devices.