The present invention relates, in general, to semiconductor devices and, more particularly, to transmitting heat away from semiconductor devices.
Semiconductor device manufacturers are constantly striving to reduce semiconductor device sizes while simultaneously increasing their speeds. An important consideration in making small, high speed, high circuit density semiconductor devices is providing packages capable of dissipating the heat generated by the devices. Typically, semiconductor device packages are designed such that a heat transfer medium is placed as close as possible to the source of heat i.e., the semiconductor device, and the surface area from which heat transfer occurs is optimized.
One response to the challenge of providing packages for small high density semiconductor devices has been the development of thin or low profile packages which employ printed circuit board substrates as a portion of the device package. One such package type is an overmolded pad array carrier. These packages offer many advantages over conventional package types such as dual in-line packages, plastic leaded chip carriers, and quad flat packs. For example, low profile packages do not have leads extending from the package edge in a linear array and thus do not present lead co-planarity nor skew problems during re-flow processes used to attach the package to a circuit board. Further, these packages occupy less space and offer lower lead inductance than conventional packages.
Low profile packages include thermal through-hole vias for transmitting or dissipating heat from the semiconductor devices. Although these vias provide a means for heat dissipation while maintaining a low profile package, they occupy a significant portion of the package and therefore occupy space which could be used for signal vias. Further, the thermal vias are effectively holes which provide a path for moisture and other contaminants to enter the packages.
Accordingly, it would be advantageous to have a method and an apparatus for spreading heat away from a semiconductor die housed within a low profile package. Further, the method and apparatus should not significantly increase the thickness nor the non-planarity of the package. It would be further advantageous that the method and apparatus not compromise the reliability of the package by allowing moisture to enter the package.