Patent Application
20080233682
Currently pure indium may be used as a thermal interface material (TIM). In some cases, the TIM may be used to attach a heat spreader and a silicon die during microelectronic packaging applications, for example. However, the price of raw indium has been skyrocketing in recent years. Thus, it is desirable to reduce the amount of indium in TIM applications to lower manufacturing cost.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the advantages of this invention can be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings in which:
a-1h represent structures according to an embodiment of the present invention.
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.
Methods and associated structures of forming a microelectronic structure are described. Those methods may include forming a core portion of a thermal interface material (TIM), wherein the core portion comprises a high thermal conductivity and does not comprise indium, and forming an outer portion of the TIM on the core portion. Methods of the present invention enable the formation of a TIM comprising a lower cost core material that may serve as a volume occupier to reduce cost.
a-1h illustrate embodiments of methods of forming a TIM 100.
In one embodiment, an outer portion 102 may be formed on the core portion 104 of the TIM 101 (
In one embodiment, the core portion 104 may comprise a discontinuous core portion 104 (
The discontinuous core portion 104 may be produced by making a porous preform of low cost metal, and may be formed from metal powders by cold compaction, sintering, or hot compaction, for example. In some embodiments, empty space within the discontinuous core portion 104 can be filled with a solder matrix material 105, by utilizing a liquid metal infiltration process, for example.
In one embodiment, the TIM 100 may comprise materials that change melting temperature after a undergoing a subsequent process temperature. For example, a transient liquid phase (or Phase Changing) system may be employed, in which the TIM 100 may comprise a low assembly temp and higher re-melting temperature after assembly. The particular materials employed in the transient liquid phase system may depend upon the particular application, but in general the liquid phase system may comprise materials that exhibit extensive solubility in each other and form little to no intermetallic compounds between the core portion and the outer portion 102. For example, in one embodiment, the core portion 104 of the TIM 100 may comprise a tin material, and the outer portion 102 may comprise a tin-indium alloy, such as but not limited to tin-52 indium (FIG. d).
In one embodiment, after the core portion 104 and the outer portion 102 have been assembled together (by various methods such as sheet rolling and pre-form utilization) the TIM 100 may undergo subsequent temperature processing, such as during a bonding process, for example (
During such a subsequent temperature process, the outer portion 102 may interdiffuse into the core portion 104. The interdiffusion of the outer portion material 102 may result in little to no intermetallic formation between the core portion 104 and the outer portion 102. After temperature processing, the TIM 100 may comprise a homogenized TIM alloy, which may comprise a higher melting temperature than before such temperature processing, due to phase changes that may occur within the TIM 100 (
In another embodiment, a reacting system may be employed, wherein the TIM 100 may comprise improved thermal conductivity, but may not substantially comprise increased melting temperature after subsequent thermal processing, as in the phase change system previously described. In one embodiment, the core portion 104 of the TIM 100 may comprise at least one of silver, copper, nickel, and other such high thermal conductivity materials. In one embodiment, the outer portion may comprise tin, indium or combinations thereof, for example. After temperature processing, an intermetallic 103 may be formed between the core portion 104 and the outer portion 102 of the TIM 100 (
h depicts a package structure 106, wherein the TIM 100 may be disposed between a die 110 and a heat sink structure 108, and also may be disposed between a heat spreader structure 107 and the heat sink structure 108. The TIM 100 may comprise any of the TIM embodiments of the present invention. In one embodiment, the die 110 may comprise a silicon die, and the package structure 106 may comprise a ceramic package and/or an organic package structure.
Thus, the benefits of the embodiments of the present invention include, but are not limited to, utilizing a cored microstructure TIM material wherein the core portion comprises a low cost material. Such as low cost, high thermal conductivity material may serve as a volume occupier to reduce manufacturing cost. An optional matrix material within the core portion may serve as a binder or space filler for the low-cost core if desired. The outer portion may serve as a wettable active layer to form a metallic bond during a reflow process, for example.
Although the foregoing description has specified certain steps and materials that may be used in the method of the present invention, those skilled in the art will appreciate that many modifications and substitutions may be made. Accordingly, it is intended that all such modifications, alterations, substitutions and additions be considered to fall within the spirit and scope of the invention as defined by the appended claims. In addition, it is appreciated that certain aspects of microelectronic devices are well known in the art. Therefore, it is appreciated that the Figures provided herein illustrate only portions of an exemplary microelectronic structure that pertains to the practice of the present invention. Thus the present invention is not limited to the structures described herein.
