Patent Publication Number: US-2011070122-A1

Title: Alloy Composition

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an alloy composition, particularly to an alloy composition with low melting point, low hardness, and high ductility. 
     2. Description of the Related Art 
     The development of Micro Electro-Mechanical System (MEMS) derives from the combination of semiconductor processes and Precision Machinery technologies, which leads all kinds of industrial products become lighter, slimmer, and shorter, multi-functional, more intelligent, and energy saving, for example some products for medical surgery, biotechnology, and informational technology are involved. In accord with (To accomplish the trend of those) the requirements of industrial products, the MEMS producers and researchers are tended to develop new micro machining technologies. Germany for example, as the most representative European country developed micro machining technology, also being one of the earliest countries to developed lithogrophy electroforming micro molding (also called Lithographie GaVanoformung Abformung, LIGA), enthusiastically dedicates to the researches of silicon micromachining and micromachining technologies. The developments of micromachining of semiconductor processes in the USA are mainly based on Si. By contrast, technique of micromachining that developed from Japan is much more different. The Japanese micromachining techniques are developed from traditional mechanic technologies, taking advantage over Japanese&#39;s leading electronically technique to develop various micromachining products. 
     Other micromachining technologies, such as a hot embossing process, are derived from LIGA technology. Using the hot embossing process on high polymer membranes to produce products with micro-feature design is an important and potential technology to processing technologies. Accordingly, the development of hot embossing process is an urge need to researchers to approach because the hot press molding can be used by thermo plasticity or thermosetting on high polymer. The key process to produce a product with patterns or micro structures is to put high polymer substrate, such as polycarbonate or polymethyl methacrylate acrylic, in a molding machine and then heat the substrate to a temperature higher than its glass transition temperature (Tg). Besides, a mold with patens or micro structures made by a micro-CNC or by LIGA technology is prepared to press the high polymer substrate in a vacuum chamber, so as to completely print each paten and microstructure of the mold onto the high polymer substrate for embossing. After the substrate is kept at the temperature for a certain time, the mold is cooled to a temperature lower than the glass transition temperature, and then the high polymer substrate is separated from the mold to make the products with patens and microstructures. 
     The micro machining technology is one of few options of the processing technologies that could be used on MEMS mass production. However, the micromachining technology can only be used on producing plastic micro devices. Plastic micro devices are widely used on an application market, however, metal can be more suitable on practice because of the requirements of the applied products such as its stabilities, heat conduction, electrically conductivity and so on. 
     Unfortunately, hot plasticity feature on metals are not as good as that on plastics, therefore hot press molding could not be appropriate applied on metals. Nowadays, most metal micro devices are molded by LIGA technology. As an example, soften compositions that are wildly used on prior application markets are eutectic alloys of solder, and are mainly selected from a group of Sn, Pb, Ag, Cu, Ni and other trace elements, wherein Sn is used as the principal component. For example, eutectic alloy of solder are alloyed with Sn and 37 wt % of Pb, Sn and 0.9 wt % of Cu, Sn and 3.5 wt % of Ag, Sn, 3.5 wt % of Ag and 0.5 wt % of Cu. However, the mechanical properties of the solder alloy that mentioned above can not be efficiently enhanced, even being processed by micro hot pressing and thermal reaction because the solder alloys are made by high ratio of Sn, and by melting with high temperature. Therefore it is necessary to develop a metal composition which can be mold by hot pressing, also have the characteristics of high hardness, high melting point, and high strength after a heat treatment. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an alloy composition which can overcome the disadvantages of prior art described above. 
     Another objective of the present invention is to provide an alloy composition with low melting point, low hardness, and high ductility which can perform high melting point, high hardness, high strength, high stability and great conductivity after a heat treatment, such as a hot embossing process or aging. 
     The present invention provides an alloy composition comprising 72.0-74.5 wt % of Ag and 25.5-27.0 wt % of Sn, wherein the particle diameter of Ag is between 10 nm to 200 μm. 
     The present invention provides an alloy composition comprising 29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In, wherein the particle diameter of Ag is between 10 nm to 200 μm. 
     The present invention provides an alloy composition comprising 29.0-60.0 wt % of Ag, 19.0-35.0 wt % of Sn, and 20.0-35.2 wt % of In, wherein the particle diameter of Ag is between 10 nm to 200 μm. 
     The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may best be more fully understood by reading the following detailed description and examples with references made to the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating a process of a composition of special alloy; 
         FIG. 2  is a diagram illustrating a process of a hot embossing process for the alloy composition; 
         FIG. 3  is a diagram of a molding gland to the hot embossing process for the alloy composition; 
         FIG. 4  is a diagram of a metal micro device after the hot embossing process; and 
         FIG. 5  is the metal micro device with a micro-channel. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an alloy composition which comprises a mixture of soft metal and Ag powder. 
     The soft metal has characters of low melting point, low hardness, and high ductility, which can be selected form a group of tin (Sn), indium (In), indium-tin alloy, tin-based alloy, indium-based alloy and indium-tin-based alloy. As described above, the tin-based alloy can be an alloy comprising Sn and 0.9 wt % of copper (Cu); Sn and 3.5 wt % of Ag; Sn and 0.7 wt % of nickel (Ni); Sn, 3.5 wt % of Ag, and 0.5 wt % of Cu; Sn, 3.0 wt % of Ag, and 0.9 wt % of Cu; Sn and 9.0 wt % of zinc (Zn) alloy or Sn and “x” wt % of aluminum (Al) alloy. The indium-based alloy can be an alloy comprising In and 0.9 wt % of Cu; In and 1.2 wt % of Ag; In and 1.2 wt % of Ni; or In and “x” wt % of Zn. In the present invention, the alloy composition shows the characters of soft metal during a mixing process and before a heat treatment, including low melting point, low hardness, and high ductility. 
     The soft metal of the alloy composition also can be a tin-based solder alloy or an indium-based solder alloy to reduce the consumption of the Ag powder, also to improve the mechanical properties of the alloy composition. The Ag powder in the alloy composition of the present invention is ground in advance with a particle diameter between 10 nm to 200 μm, which is uniformly distributed over the texture of soft metal. 
     After the heat treatment, the soft metal and the Ag powder in the alloy composition are re-constructed into a new structural texture, which make the alloy composition tend to has characters of high melting point, high hardness, high strength, high stability and great conductivity. Furthermore, the alloy composition also can be mixed with 0.01-2.0 wt % of Cu, 0.01-2.0 wt % of Ni, or 0.01-3.0 wt % of germanium (Ge) for promoting the thermal conductivity, enhancing the corrosion resistance and mechanical properties, or for decreasing the melting point and wettability before the heat treatment respectively. 
     In fact, it is impossible to mix the pure Ag powder and the soft metal without any other substances, like Cu, Ni, gold (Au) and Zn, and accordingly the properties of the alloy composition might be changed due to the contamination of Cu, Ni, gold (Au) and Zn in the Ag powder and the soft metal. On the other hand, a particular amount of Cu powder or Ni powder could also be blended into the alloy composition if necessary. 
     Referring to  FIG. 1 , it illustrates a preferable production diagram of the alloy composition in the present invention, and it is to be understood that the process of the alloy composition is not limited thereto. 
     As show in  FIG. 1 , the alloy composition in the present invention is produced by rolling-mix method. Firstly, soften metal, such as Sn, In, or In—Sn alloy, is pressed into a plurality of metal foils  2  by a rolling equipment  1 . Secondary, the Ag powder  3  with the diameter of each particle thereof between 10 nm and 200 μm is evenly arranged between the metal foils  2 , and then the metal foils  2  with the Ag powder  3  is pressed by the rolling equipment  1  again to obtain a metal foil  2 ′. Finally, the metal foil  2 ′ is repeatedly folded and rolling pressed by the rolling equipment  1 , so that the Ag powder  3  can be completely and evenly mixed into the metal foil  2  to obtain a alloy composition  4 . Moreover, Cu metal powder and Ni metal power can be individually mixed up with the Ag metal powder  3  to obtain Ag—Cu metal powder, Ag—Ni metal powder or Ag—Cu—Ni meta for spreading on the metal foil  2  following by the process of rolling pressing by the rolling equipment  1 , folding and rolling pressing again as described above. Finally after repeatedly folding and rolling pressing, the alloy composition  4  with a plurality ratio of Cu metal powder or Ni metal powder can be obtained thereby. 
     Referring to  FIGS. 2 ,  3  and  4  illustrate a hot embossing process of the alloy composition. The alloy composition in the present invention shows the characteristics of low malting point, high ductility, and soft before the heat treatment, therefore the alloy composition is sufficient to be processed by hot embossing to manufacture into metal micro devices. For example, the alloy composition  4  in the present invention is heated by a heating equipment  5 , with a preferable heating temperature approaching to the malting point (Tm) of the alloy composition  4 , such as Tm−100° C.&lt;T&lt;Tm+100° C. Then, a mold  6  is covering pressed on the alloy composition  4  under a circumstance of a vacuum chamber or standard atmospheric pressure in order to transfer a pattern  61  from the mold  6  to the alloy composition  4 . As a result, a micro structure  41  corresponded with the pattern  61  is form on the surface of the special composition  4 . As following, the alloy composition  4  and the mold  6  are contacted and kept at a temperature for a period in order to make the metal in the alloy composition  4  undergoing the process of “isothermal solidification”, thereby an intermetallic compounds with characteristic of high malting point and high hardness will be produced. Finally, to cool down and remove the mold  6 , a micro metal device manufactured from the alloy composition  4  are obtained, wherein some microstructures, like micro-indentation or micro-channel  41  may be shaped on the surface of the alloy composition  4 . 
     In  FIG. 5  illustrates the alloy composition with micro structure  41  of microchannel on the surface. The alloy composition  4  which had been finished the thermal reaction and had become a micro metal device, consists characteristics of high melting point, high hardness, high strength, high stability and great conductivity, therefore the alloy composition could be applied on Micro Electro-Mechanical System (MEMS). In summary, the alloy composition  4  in the present invention, have characteristics of low malting point, high ductility, and soft before the hot embossing process, therefore the alloy composition can be applied on the hot embossing process for overcoming the weakness of normal metal in hot embossing process, like high malting point and poor plasticity. On the other hand, after the hot embossing process, the alloy composition  4  in the present invention may become a good micro metal device with high hardness, high malting point, high strength, high stability and great conductivity that can expand the application of the micro metal device. On the other hand, the application of the alloy composition in the present invention is not restricted to hot press molding. Take another hot embossing process for example. An initial alloy composition (before heat treatment) of present invention has characteristics of low malting point, high ductility, and soft. Therefore the alloy composition can be applied on the process of microelectronics packaging process, such as assemble a micro-circuit contacts between chips or assemble a connect between circuit board containing and a chip. However, after a thermal reaction of reflow, solder chips welding together. From a prior art knows that electronic products will be heated after overcurrent, therefore a weld which is made by the alloy composition will become 
     the material that consist the characteristics of high melting point, high hardness, high strength, high stability and great conductivity because the alloy composition accomplished the reaction of the hot embossing that induced by overcurrent. 
     In four preferable examples described as following summarize the alloy composition with different metallic ratio in the present invention. 
     In the example 1, the alloy composition, with Sn as the soft metal, comprises 72.0-74.5 wt % of Ag and 24.5-27.0 wt % of Sn, particular for 74 wt % of Ag and 26 wt % of Sn. The alloy composition in the example 1 is heated under a temperature between 230° C. and 400° C., more preferable at 260° C. for hot embossing process. After the heat treatment, a large number of Ag 3 Sn intermetrallic compound or an organizational structure of Ag 3 Sn intermetrallic compound are produced in the internal structure of the metal micro-component which could greatly increased the melting point and hardness of the metal micro-component. 
     In the example 2, the alloy composition; with In as the soft metal, comprises 29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In, particular for 29-32 wt % of Ag and 66.5-70 wt % of In and most preferable for 31.7 wt % of Ag, 68.1 wt % of In and 0.2 wt % of Cu. The alloy composition in the example 2 is heated under a temperature between 100° C. and 160° C., more preferable at 156° C. for hot embossing process. After the heat treatment, a large number of AgIn 2  intermetrallic compound or an organizational structure of AgIn 2  intermetrallic compound are produced in the internal structure of the metal micro-component which could greatly increased the melting point and hardness of the metal micro-component. 
     In the example 3, the alloy composition, with In selected as the soft metal, comprises 29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In, particular for 67-67.5 wt % of Ag and 31.5-35 wt % of In and most preferable for 66.7 wt % of Ag, 32 wt % of In and 0.3 wt % of Ni. The alloy composition in the example 3 is heated under a temperature between 150° C. and 250° C., more preferable at 220° C. for hot embossing process. After the heat treatment, a large number of AgIn 2  intermetrallic compound or an organizational structure of AgIn 2  intermetrallic compound are produced in the internal structure of the metal micro-component. 
     In the example 4, the alloy composition, with indium-tin alloy selected as the soft metal, comprises 29.0-60 wt % of Ag, 19-35 wt % of Sn and 20-35.2 wt % of In, particular for 35 wt % of Ag, 30 wt % of Sn and 35 wt % of In. The alloy composition in the example 4 is heated under a temperature between 150° C. and 250° C., more preferable at 200° C. for hot embossing process. After the heat treatment, a large number of intermetrallic compounds, Ag 3 Sn, Ag 2 In, AgIn 2  and AgInSn 2  for example, are produced in the internal structure of the metal micro-component. 
     Thus, to further adjust the ratio between Ag and the soft metal of the alloy composition, the operated temperature of the micro-compression molding can be differentially set in accord with the need of use. 
     As described above, mixing the Ag powder with the soft metal can obtain the alloy composition in the present invention, with characters of low melting point, low hardness and high ductility which can be used on the hot embossing process. After the heat treatment, the hot embossing process, the intermetrallic compound of the alloy composition are transformed and tented to show high melting point, high hardness, high strength, high stability and great conductivity to improve the feature of the alloy composition. 
     The alloy composition in the present invention can also be used as a solder for the surface mount technology (SMT) of electrical device. Therefore the electrical device can be welded on a board (such as a motherboard or a mobile phone board), and 3D packaging has been used for application. The alloy composition of the present invention can sustain a overheating that occurred to the process of 3D packaging. However, it is need to be understood that an example that mentioned above is one of the applications of the alloy composition in the present invention. 
     The alloy composition in present invention, with characters of low melting point, low hardness, and high ductility, can be applied to hot embossing process. The alloy composition would transfer to an intermetallic compounds, which could effectively enhance the performances of the alloy composition after a heat treatment (such as hot embossing process), including high melting point, high hardness, high strength, high stability and great conductivity. 
     Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.