Patent Abstract:
A method of singulating semiconductor packages, the method comprising: providing a plurality of semiconductor dies coupled to a single common leadframe, wherein a molding compound at least partially encases the semiconductor dies and the leadframe; singulating the plurality of semiconductor dies, wherein the leadframe is at least partially cut between adjacent semiconductor dies, thereby forming exposed side surfaces on leads of the leadframe; and plating the exposed side surfaces of the leads with a plating material, wherein the plating material is a different material than the leads. In some embodiments, singulating the plurality of semiconductor dies comprises performing a full cut of the leadframe. In some embodiments, singulating the plurality of semiconductor dies comprises performing separate partial cuts of the leadframe.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 61/378,776, filed Aug. 31, 2010, entitled “SINGULATION METHOD FOR SEMICONDUCTOR PACKAGE WITH PLATING ON SIDE OF CONNECTORS” and to U.S. Provisional Application Ser. No. 61/412,183, filed Nov. 10, 2010, entitled “SINGULATION AND PLATING METHOD FOR SEMICONDUCTOR PACKAGE,” both of which are hereby incorporated by reference in their entirety as if set forth herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of semiconductor packages. More specifically, the present invention relates to a singulation and plating method for semiconductor packages. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  is a perspective view of a prior art semiconductor package  100  having a top surface  110   a  and side surfaces  110   b  formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  120   a  and side surfaces  120   b  of its leads being exposed. The region  130  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. As seen in  FIG. 1 , although the top surfaces  120   a  and region  130  might be plated with a plating material, the sides  120   b  of the leads, or connectors, in a conventional package  100  are not plated. As a result of the side surfaces  120   b  of the leads not being plated, their exposed surface, typically copper, is easy to react with oxygen, thereby resulting in undesirable oxide on the surface of the leads. The contaminated surface will create problems when the semiconductor package  100  is soldered into a printed circuit board. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new, useful, and non-obvious method of singulating and plating semiconductor packages, employing plating of the side surfaces of the leads of the leadframe in order to prevent contamination of the lead surfaces. 
     In one aspect of the present invention, a method of singulating semiconductor packages comprises: providing a plurality of semiconductor dies coupled to a single common leadframe, wherein a molding compound at least partially encases the semiconductor dies and the leadframe; singulating the plurality of semiconductor dies, wherein the leadframe is at least partially cut between adjacent semiconductor dies, thereby forming exposed side surfaces on leads of the leadframe; and plating the exposed side surfaces of the leads with a plating material, wherein the plating material is a different material than the leads. 
     In some embodiments, the leads are copper. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin, silver, gold, nickel-gold, nickel-palladium, or nickel-palladium-gold. 
     In some embodiments, the leadframe has a top surface and a bottom surface opposite the top surface, and the step of singulating the plurality of semiconductor dies comprises performing a full cut of the leadframe in a single cutting operation before the step of plating the exposed side surfaces, wherein the full cut extends all the way between the top surface and the bottom surface. In some embodiments, the semiconductor dies are attached to the bottom surface of the leadframe, and the method further comprises plating the top surface of the leadframe before the step of singulating the plurality of semiconductor dies. In some embodiments, the semiconductor dies are attached to the bottom surface of the leadframe, and the method further comprises plating the top surface of the leadframe after the step of singulating the plurality of semiconductor dies. 
     In some embodiments, the leadframe has a top surface and a bottom surface opposite the top surface, and the step of singulating the plurality of semiconductor dies comprises: performing a first partial cut of the leadframe, wherein the first partial cut does not extend all the way between the bottom surface and the top surface; and performing a second partial cut of the leadframe, wherein the second partial cut is performed separately from the first partial cut and completes the singulation of the semiconductor dies all the way between the bottom surface and the top surface of the leadframe, thereby forming a plurality of singulated semiconductor packages. In some embodiments, the step of plating the exposed side surfaces is performed in between the first partial cut and the second partial cut. In some embodiments, the semiconductor dies are attached to the bottom surface of the leadframe, and the method further comprises plating the top surface of the leadframe, wherein the plating of the top surface is performed before the first partial cut. In some embodiments, the semiconductor dies are attached to the bottom surface of the leadframe, and the method further comprises plating the top surface of the leadframe, wherein the plating of the top surface is performed between the first partial cut and the second partial cut. In some embodiments, the first partial cut is performed using a blade having a first thickness and the second partial cut is performed using a blade having a second thickness, wherein the first thickness and the second thickness are different. In some embodiments, the second thickness is larger than the first thickness. In some embodiments, the second partial cut forms a step on sides of the singulated semiconductor packages. In some embodiments, the first partial cut or the second partial cut is performed using a blade having a beveled edge. 
     In some embodiments, the step of providing the plurality of semiconductor dies comprises: coupling the semiconductor dies to the single common leadframe; wire bonding the semiconductor dies to leads of the leadframe; and at least partially encasing the semiconductor dies and the leadframe in a molding compound. 
     In another aspect of the present invention, a singulated semiconductor package comprises: a leadframe having a die attach pad and a plurality of leads; a semiconductor die coupled to the die attach pad of the leadframe; and a molding compound at least partially encasing the leadframe and the semiconductor die, wherein side surfaces of the leads are exposed through the molding compound, and wherein the side surfaces of the leads are plated with a plating material, the plating material being a different material than the leads. 
     In some embodiments, the leads are copper. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin, silver, gold, nickel-gold, nickel-palladium, or nickel-palladium-gold. 
     In some embodiments, the mold compound comprises a top surface, a bottom surface, and side surfaces between the top surface and the bottom surface, wherein the side surfaces comprise a step. In some embodiments, the mold compound comprises a top surface, a bottom surface, and side surfaces between the top surface and the bottom surface, wherein the side surfaces comprise a beveled portion. In some embodiments, the mold compound comprises a top surface, a bottom surface, and side surfaces between the top surface and the bottom surface, wherein the side surfaces comprise a beveled portion and a non-beveled portion. 
     In some embodiments, the semiconductor die is wire bonded to the leads of the leadframe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prior art semiconductor package. 
         FIG. 2  is a perspective view of a semiconductor package in accordance with some embodiments of the present invention. 
         FIGS. 3A-H  illustrate different stages of a singulation and plating process using full cutting in accordance with some embodiments of the present invention. 
         FIGS. 4A-G  illustrate different stages of another singulation and plating process using full cutting in accordance with some embodiments of the present invention. 
         FIG. 5A  is a perspective view of the top of a semiconductor package formed with full cutting in accordance with some embodiments of the present invention. 
         FIG. 5B  is a perspective view of the bottom of the semiconductor package with full cutting in accordance with some embodiments of the present invention. 
         FIGS. 6A-H  illustrate different stages of a singulation and plating process using partial cutting in accordance with some embodiments of the present invention. 
         FIGS. 7A-G  illustrate different stages of another singulation and plating process using partial cutting in accordance with some embodiments of the present invention. 
         FIG. 8  is a cross-sectional perspective view of a partial cutting of a semiconductor package in accordance with some embodiments of the present invention. 
         FIG. 9A  is a perspective view of the bottom of a semiconductor package having a first step height formed with partial cutting in accordance with some embodiments of the present invention. 
         FIG. 9B  is a perspective view of the top of the semiconductor package having a first step height formed with partial cutting in accordance with some embodiments of the present invention. 
         FIG. 10A  is a perspective view of the bottom of a semiconductor package having a second step height formed with partial cutting in accordance with some embodiments of the present invention. 
         FIG. 10B  is a perspective view of the top of the semiconductor package having a second step height formed with partial cutting in accordance with some embodiments of the present invention. 
         FIGS. 11A-H  illustrate different stages of a singulation and plating process using partial cutting with a partial bevel-edged blade in accordance with some embodiments of the present invention. 
         FIGS. 12A-G  illustrate different stages of another singulation and plating process using partial cutting with a partial bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 13  is a cross-sectional perspective view of a partial cutting of a semiconductor package with both partial and full bevel-edged blades in accordance with some embodiments of the present invention. 
         FIG. 14A  is a perspective view of the bottom of a semiconductor package having a beveled side surface formed with a partial bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 14B  is a perspective view of the top of the semiconductor package having a beveled side surface formed with a partial bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 15A  is a perspective view of the bottom of a semiconductor package having a beveled side surface with a first height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 15B  is a perspective view of the top of the semiconductor package having a beveled side surface with a first height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 16A  is a perspective view of the bottom of a semiconductor package having a beveled side surface with a second height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. 
         FIG. 16B  is a perspective view of the top of the semiconductor package having a beveled side surface with a second height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the described embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. 
     This disclosure provides several embodiments of the present invention. It is contemplated that any features from any embodiment can be combined with any features from any other embodiment. In this fashion, hybrid configurations of the disclosed embodiments are well within the scope of the present invention. 
     The present invention provides a new, useful, and non-obvious method of singulating and plating semiconductor packages, employing plating of the side surfaces of the leads of the leadframe in order to prevent contamination of the lead surfaces. 
       FIG. 2  is a perspective view of a semiconductor package  200  in accordance with some embodiments of the present invention. The semiconductor package  200  has a top surface  210   a  and side surfaces  210   b  preferably formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  220   a  and side surfaces  220   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  230  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. 
     As seen in  FIG. 2 , not only are the top surfaces  220   a  and region  230  plated with a plating material, but the sides  220   b  of the leads, or connectors, are plated with a plating material as well. In some embodiments, the plating material on the surfaces  220   a ,  220   b , and  230  is a material configured not to react with oxygen. As a result, the plated surfaces have a good soldering result when the semiconductor package  200  is attached to a printed circuit board. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In a preferred embodiment, the sides of the leadframe connectors are plated after they are singulated in strip form. In some embodiments, the singulation processes of the present invention, such as those discussed below, involve taking a wafer containing multiple, preferably identical, semiconductor dies coupled to a leadframe, and reducing it into individual semiconductor packages each containing one of those dies. It is contemplated that the present invention can employ a variety of different plating processes and techniques in order to plate the surfaces of the leads. In some embodiments, the present invention can employ any of the plating processes and techniques disclosed in U.S. patent application Ser. No. 12/579,574, filed Oct. 15, 2009, and entitled “METALLIC SOLDERABILITY PRESERVATION COATING ON METAL PART OF SEMICONDUCTOR PACKAGE TO PREVENT OXIDE,” which is hereby incorporated by reference in its entirety as if set forth herein 
     It is noted that reference is made in this disclosure to “top” and “bottom” surfaces. The purpose of using the terms “top” and “bottom” with respect to the surfaces is to help identify these surfaces as being opposite one another and to help identify the “side” surfaces as being the surfaces between the “top” and “bottom” surfaces. Therefore, in certain portions of this disclosure, “top” surfaces can appear to be on the bottom and “bottom” surfaces can appear to be on the top if the positioning of the semiconductor package has been changed. 
       FIGS. 3A-H  illustrate different stages of a singulation and plating process using full cutting in accordance with some embodiments of the present invention. In  FIG. 3A , a plurality of semiconductor dies  320  are each coupled to a surface of the same leadframe  310  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  320  is attached to a die attach pad on the leadframe  310 . The leadframe  310  comprises a side surface  305  that extends between a bottom surface  315  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  320  can be coupled to the leadframe  310  in a variety of different ways, including, but not limited to, using soldering flux. In  FIG. 3B , the semiconductor dies  320  are wire bonded to the leadframe  310  using wires  330 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  330 , including, but not limited to, aluminum, copper, and gold. In  FIG. 3C , a molding process is performed to encase the semiconductor dies  320 , the leadframe  310 , and the bonding wires  330  in a molding compound  340 . 
     In  FIG. 3D , a plating process is performed to plate the bottom surface  315  with a plating material  350 . In a preferred embodiment, the plating material  350  is a material configured not to react with oxygen. In some embodiments, the plating material  350  is a metallic material. In some embodiments, the plating material  350  is tin. Other materials that can be used as the plating material  350  include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In  FIG. 3E , a singulation process is performed on the leadframe strip  310 . In a preferred embodiment, the leadframe strip  310  is placed on a support  365 , and blades  360  are used to completely singulate the semiconductor packages in one full cutting operation. In some embodiments, as seen in  FIG. 3E , the bottom surface  315  is facing upward during the full cutting operation. However, it is contemplated that the bottom surface  315  can be alternatively positioned, such as facing downwards, sideways, or at an angle. 
     In  FIG. 3F , the side surfaces  305  of the leads between neighboring semiconductor dies are exposed as a result of the singulation process. The singulated semiconductor packages can now be loaded to another plating process. In  FIG. 3G , the exposed side surfaces  305  of the leads are plated with a plating material  355 . As discussed above, the plating material  355  is preferably a material configured not to react with oxygen. In some embodiments, the plating material  355  is a metallic material. In some embodiments, the plating material  355  is tin. Other materials that can be used as the plating material  350  include, but are not limited to, silver, gold, and nickel-gold. 
       FIG. 3H  shows the finished individual semiconductor packages  300 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  300  has a semiconductor die  320  and a leadframe  310  at least partially encased in the molding compound  340 , with the leads of each leadframe  310  being accessible to electrical coupling via the plating material  350  and  355  over the portions of the leads that are exposed from the molding compound  340 . Each semiconductor package  300  has side surfaces  342  that are formed from the molding compound  340 . In some embodiments, the side surfaces  342  are straight from top to bottom, as shown in  FIG. 3H . 
       FIGS. 4A-G  illustrate different stages of another singulation and plating process using full cutting in accordance with some embodiments of the present invention. In  FIG. 4A , a plurality of semiconductor dies  420  are each coupled to a surface of the same leadframe  410  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  420  is attached to a die attach pad on the leadframe  410 . The leadframe  410  comprises a side surface  405  that extends between a bottom surface  415  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  420  can be coupled to the leadframe  410  in a variety of different ways, including, but not limited to, using soldering flux. In  FIG. 4B , the semiconductor dies  420  are wire bonded to the leadframe  410  using wires  430 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  430 , including, but not limited to, aluminum, copper, and gold. In  FIG. 4C , a molding process is performed to encase the semiconductor dies  420 , the leadframe  410 , and the bonding wires  430  in a molding compound  440 . 
     In  FIG. 4D , a singulation process is performed on the leadframe strip  410 . In a preferred embodiment, the leadframe strip  410  is placed on a support  465 , and blades  460  are used to completely singulate the semiconductor packages in one full cutting operation. In some embodiments, as seen in  FIG. 4D , the bottom surface  415  is facing upward during the full cutting operation. However, it is contemplated that the bottom surface  415  can be alternatively positioned, such as facing downwards, sideways, or at an angle. 
     In  FIG. 4E , the side surfaces  405  of the leads between neighboring semiconductor dies are exposed as a result of the singulation process. The singulated semiconductor packages can now be loaded to a plating process. In  FIG. 4F , a plating process is performed to plate the bottom surfaces  415  and the side surfaces  405  with a plating material  450  and  455 , respectively. In a preferred embodiment, the plating material is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
       FIG. 4G  shows the finished individual semiconductor packages  400 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  400  has a semiconductor die  420  and a leadframe  410  at least partially encased in the molding compound  440 , with the leads of each leadframe  410  being accessible to electrical coupling via the plating material  450  and  455  over the portions of the leads that are exposed from the molding compound  440 . Each semiconductor package  400  has side surfaces  442  that are formed from the molding compound. In some embodiments, the side surfaces  442  are straight from top to bottom, as shown in  FIG. 4H . 
       FIGS. 5A and 5B  illustrate perspective views of the top and the bottom of a semiconductor package  500  formed with full cutting in accordance with some embodiments of the present invention. Semiconductor package  500  has a top surface  510   a , a bottom surface  510   c  opposite the top surface  510   a , and side surfaces  510   b  between top surface  510   a  and bottom surface  510   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  520   a  and side surfaces  520   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  530  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  520   a , side surfaces  520   b , and region  530  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces  510   b  of the semiconductor package  500  are straight, as seen in  FIGS. 5A-B . However, it is contemplated that the side surfaces of the semiconductor package can be configured in other shapes, as will be discussed in more detail below. 
       FIGS. 6A-H  illustrate different stages of a singulation and plating process using partial cutting in accordance with some embodiments of the present invention. In  FIG. 6A , a plurality of semiconductor dies  620  are each coupled to a surface of the same leadframe  610  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  620  is attached to a die attach pad on the leadframe  610 . The leadframe  610  comprises a side surface  605  that extends between a bottom surface  615  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  620  can be coupled to the leadframe  610  in a variety of different ways, including, but not limited to, using soldering flux. The semiconductor dies  620  are wire bonded to the leadframe  610  using wires  630 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  630 , including, but not limited to, aluminum, copper, and gold. In  FIG. 6B , a molding process is performed to encase the semiconductor dies  620 , the leadframe  610 , and the bonding wires  630  in a molding compound  640 . 
     In  FIG. 6C , a plating process is performed to plate the bottom surface  615  with a plating material  650 . In a preferred embodiment, the plating material  650  is a material configured not to react with oxygen. In some embodiments, the plating material  650  is a metallic material. In some embodiments, the plating material  650  is tin. Other materials that can be used as the plating material  650  include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In  FIG. 6D , a partial singulation process is performed on the leadframe strip  610 . In a preferred embodiment, blades  660  are used to partially singulate the semiconductor packages. For example, in some embodiments, the blades  660  cut through the entire leadframe  610 , but do not pass through all of the molding compound  640 , thereby forming side surface  642  of the molding compound between neighboring semiconductor dies  620 , but still leaving the individual semiconductor packages attached to one another. 
     In  FIG. 6E , the side surfaces  605  of the leads between neighboring semiconductor dies  620  are exposed as a result of the partial singulation process. The singulated semiconductor packages can now be loaded to another plating process. In  FIG. 6F , the exposed side surfaces  605  of the leads are plated with a plating material  655 . As discussed above, the plating material  655  is preferably a material configured not to react with oxygen. In some embodiments, the plating material  655  is a metallic material. In some embodiments, the plating material  655  is tin. Other materials that can be used as the plating material  650  include, but are not limited to, silver, gold, and nickel-gold. 
     In  FIG. 6G , another partial singulation process is performed on the leadframe strip  610  in order to complete the singulation of the semiconductor packages. In a preferred embodiment, blades  662  are used to singulate the semiconductor packages. In some embodiments, the blades  662  have a different shape than the blades  660  of the first partial singulation process in  FIG. 6D . In some embodiments, the blades  662  have a different thickness than the blades  660 . In some embodiments, the blades  662  have a greater thickness than the blades  660 . 
       FIG. 6H  shows the finished individual semiconductor packages  600 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  600  has a semiconductor die  620  and a leadframe  610  at least partially encased in the molding compound  640 , with the leads of each leadframe  610  being accessible to electrical coupling via the plating material  650  and  655  over the portions of the leads that are exposed from the molding compound  640 . Each semiconductor package  600  has side surfaces that are formed from the molding compound  640 . 
       FIG. 6H  shows the side surfaces of semiconductor package  600  having a first portion  642 , formed from the first partial singulation blade  660 , and a second portion  644 , formed from the second partial singulation blade  662 . Since the second singulation blade  662  was thicker than the first singulation blade  660 , a step is formed on the side of the semiconductor package  600 . 
       FIGS. 7A-G  illustrate different stages of another singulation and plating process using partial cutting in accordance with some embodiments of the present invention. In  FIG. 7A , a plurality of semiconductor dies  720  are each coupled to a surface of the same leadframe  710  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  720  is attached to a die attach pad on the leadframe  710 . The leadframe  710  comprises a side surface  705  that extends between a bottom surface  715  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  720  can be coupled to the leadframe  710  in a variety of different ways, including, but not limited to, using soldering flux. The semiconductor dies  720  are wire bonded to the leadframe  710  using wires  730 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  730 , including, but not limited to, aluminum, copper, and gold. In  FIG. 7B , a molding process is performed to encase the semiconductor dies  720 , the leadframe  710 , and the bonding wires  730  in a molding compound  740 . 
     In  FIG. 7C , a partial singulation process is performed on the leadframe strip  710 . In a preferred embodiment, blades  760  are used to partially singulate the semiconductor packages. For example, in some embodiments, the blades  760  cut through the entire leadframe  710 , but do not pass through all of the molding compound  740 , thereby forming side surface  742  of the molding compound between neighboring semiconductor dies  720 , but still leaving the individual semiconductor packages attached to one another. 
     In  FIG. 7D , the side surfaces  705  of the leads between neighboring semiconductor dies  720  are exposed as a result of the partial singulation process. The singulated semiconductor packages can now be loaded to a plating process. In  FIG. 7E , the bottom surfaces  715  and the exposed side surfaces  705  of the leads are plated with a plating material  750  and  755 , respectively. As discussed above, the plating material is preferably a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In  FIG. 7F , another partial singulation process is performed on the leadframe strip  710  in order to complete the singulation of the semiconductor packages. In a preferred embodiment, blades  762  are used to singulate the semiconductor packages. In some embodiments, the blades  762  have a different shape than the blades  760  of the first partial singulation process in  FIG. 7C . In some embodiments, the blades  762  have a different thickness than the blades  760 . In some embodiments, the blades  762  have a greater thickness than the blades  760 . 
       FIG. 7G  shows the finished individual semiconductor packages  700 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  700  has a semiconductor die  720  and a leadframe  710  at least partially encased in the molding compound  740 , with the leads of each leadframe  710  being accessible to electrical coupling via the plating material  750  and  755  over the portions of the leads that are exposed from the molding compound  740 . Each semiconductor package  700  has side surfaces that are formed from the molding compound  740 . 
       FIG. 7G  shows the side surfaces of semiconductor package  700  having a first portion  742 , formed from the first partial singulation blade  760 , and a second portion  744 , formed from the second partial singulation blade  762 . Since the second singulation blade  762  was thicker than the first singulation blade  760 , a step is formed on the side of the semiconductor package  700 . 
       FIG. 8  is a cross-sectional perspective view of a partial cutting of a semiconductor package  800  in accordance with some embodiments of the present invention. In  FIG. 8 , semiconductor package  800  comprises a semiconductor die and a leadframe encased within a molding compound, with the side surface of leads  820   b  being exposed from the molding compound. During the partial singulation cutting of the semiconductor package  800 , a cutting blade  860  cuts through the molding compound and/or the leadframe. In  FIG. 8 , the cutting blade  860  is shown cutting through the bottom surface  810   c  of the semiconductor package  800 , which is positioned with its bottom surface  810   c  facing upwards. In some embodiments, different blades are used for different cuttings. For example, in  FIG. 8 , blade assembly  860  comprises a blade  862  extending from a shank  864 , which is used by a tool to hold and manipulate the blade  862 . During a first cutting operation, a first blade can be stopped at a certain depth of the semiconductor package  800 . In a subsequent cutting operation, a second blade having a different thickness as the first blade can be used to cut through the remaining portion of the semiconductor package  800 . In some embodiments, this subsequent cutting operation is performed from an opposite side of the semiconductor package  800  as the first cutting operation. As a result of the different thicknesses of the blades, a step can be formed between a first side surface  810   b , formed by the thinner blade, and a second side surface  815   b , formed by the thicker blade. 
       FIGS. 9A and 9B  illustrate perspective views of the bottom and top of a semiconductor package  900  having a first step height formed with partial cutting in accordance with some embodiments of the present invention. In some embodiments, the semiconductor package  900  is singulated and its step is formed using a blade assembly such as blade  860  in  FIG. 8 . Semiconductor package  900  has a top surface  910   a , a bottom surface  910   c  opposite the top surface  910   a , and side surfaces between top surface  910   a  and bottom surface  910   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  920   a  and side surfaces  920   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  930  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  920   a , side surfaces  920   b , and region  930  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces of the semiconductor package  900  have a first portion  910   b , formed from a first partial singulation blade, and a second portion  915   b , formed from a second partial singulation blade that is thicker than the first partial singulation blade. As a result of the second singulation blade being thicker than the first singulation blade, a step is formed on the side of the semiconductor package  900 . 
       FIGS. 10A and 10B  illustrate perspective views of the bottom and top of a semiconductor package  1000  having a second step height formed with partial cutting in accordance with some embodiments of the present invention. Semiconductor package  1000  is almost identical to semiconductor package  900 , except for the height of the step on its side surface. Semiconductor package  1000  has a top surface  1010   a , a bottom surface  1010   c  opposite the top surface  1010   a , and side surfaces between top surface  1010   a  and bottom surface  1010   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  1020   a  and side surfaces  1020   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  1030  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  1020   a , side surfaces  1020   b , and region  1030  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces of the semiconductor package  1000  have a first portion  1010   b , formed from a first partial singulation blade, and a second portion  1015   b , formed from a second partial singulation blade that is thicker than the first partial singulation blade. As a result of the second singulation blade being thicker than the first singulation blade, a step is formed on the side of the semiconductor package  1000 . As mentioned above, semiconductor package  1000  is almost identical to semiconductor package  900 , except for the height of the step on its side surface. The first portion  910   b  and the second portion  915   b  of the side surfaces in  FIG. 9  are substantially equal in height, whereas the first portion  1010   b  of the side surface in  FIGS. 10A-B  is substantially smaller in height than the second portion  1015   b  of the side surfaces in  FIGS. 10A-B . 
       FIGS. 11A-H  illustrate different stages of a singulation and plating process using partial cutting with a partial bevel-edged blade in accordance with some embodiments of the present invention. In  FIG. 11A , a plurality of semiconductor dies  1120  are each coupled to a surface of the same leadframe  1110  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  1120  is attached to a die attach pad on the leadframe  1110 . The leadframe  1110  comprises a side surface  1105  that extends between a bottom surface  1115  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  1120  can be coupled to the leadframe  1110  in a variety of different ways, including, but not limited to, using soldering flux. The semiconductor dies  1120  are wire bonded to the leadframe  1110  using wires  1130 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  1130 , including, but not limited to, aluminum, copper, and gold. In  FIG. 11B , a molding process is performed to encase the semiconductor dies  1120 , the leadframe  1110 , and the bonding wires  1130  in a molding compound  1140 . 
     In  FIG. 11C , a plating process is performed to plate the bottom surface  1115  with a plating material  1150 . In a preferred embodiment, the plating material  1150  is a material configured not to react with oxygen. In some embodiments, the plating material  1150  is a metallic material. In some embodiments, the plating material  1150  is tin. Other materials that can be used as the plating material  1150  include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In  FIG. 11D , a partial singulation process is performed on the leadframe strip  1110 . In a preferred embodiment, blades  1160  are used to partially singulate the semiconductor packages. For example, in some embodiments, the blades  1160  cut through the entire leadframe  1110 , but do not pass through all of the molding compound  1140 , thereby forming side surface  1142  of the molding compound between neighboring semiconductor dies  1120 , but still leaving the individual semiconductor packages attached to one another. 
     In  FIG. 11E , the side surfaces  1105  of the leads between neighboring semiconductor dies  1120  are exposed as a result of the partial singulation process. The singulated semiconductor packages can now be loaded to another plating process. In  FIG. 11F , the exposed side surfaces  1105  of the leads are plated with a plating material  1155 . As discussed above, the plating material  1155  is preferably a material configured not to react with oxygen. In some embodiments, the plating material  1155  is a metallic material. In some embodiments, the plating material  1155  is tin. Other materials that can be used as the plating material  1150  include, but are not limited to, silver, gold, and nickel-gold. 
     In  FIG. 11G , another partial singulation process is performed on the leadframe strip  1110  in order to complete the singulation of the semiconductor packages. In a preferred embodiment, blades  1162  are used to singulate the semiconductor packages. In some embodiments, the blades  1162  of have a different shape than the blades  1160  of the first partial singulation process in  FIG. 11D . In some embodiments, the blades  1162  have a beveled edge. 
       FIG. 11H  shows the finished individual semiconductor packages  1100 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  1100  has a semiconductor die  1120  and a leadframe  1110  at least partially encased in the molding compound  1140 , with the leads of each leadframe  1110  being accessible to electrical coupling via the plating material  1150  and  1155  over the portions of the leads that are exposed from the molding compound  1140 . Each semiconductor package  1100  has side surfaces that are formed from the molding compound  1140 .  FIG. 11H  shows the side surfaces of semiconductor package  1100  having a first portion  1142 , formed from the first partial singulation blade  1160 , and a second portion  1144 , formed from the second partial singulation blade  1162 . A beveled surface  1146 , formed from the beveled edge of the second partial singulation blade  1162 , extends from the first portion  1142  to the second portion  1144 . 
       FIGS. 12A-G  illustrate different stages of another singulation and plating process using partial cutting with a partial bevel-edged blade in accordance with some embodiments of the present invention. In  FIG. 12A , a plurality of semiconductor dies  1220  are each coupled to a surface of the same leadframe  1210  (e.g., a leadframe strip). In a preferred embodiment, each of the semiconductor dies  1220  is attached to a die attach pad on the leadframe  1210 . The leadframe  1210  comprises a side surface  1205  that extends between a bottom surface  1215  of the leadframe and the top surface of the leadframe (i.e., the surface to which the semiconductor dies are attached). It is contemplated that the semiconductor dies  1220  can be coupled to the leadframe  1210  in a variety of different ways, including, but not limited to, using soldering flux. The semiconductor dies  1220  are wire bonded to the leadframe  1210  using wires  1230 . It is contemplated that a variety of different types of materials can be used to form the bonding wires  1230 , including, but not limited to, aluminum, copper, and gold. In  FIG. 12B , a molding process is performed to encase the semiconductor dies  1220 , the leadframe  1210 , and the bonding wires  1230  in a molding compound  1240 . 
     In  FIG. 12C , a partial singulation process is performed on the leadframe strip  1210 . In a preferred embodiment, blades  1260  are used to partially singulate the semiconductor packages. For example, in some embodiments, the blades  1260  cut through the entire leadframe  1210 , but do not pass through all of the molding compound  1240 , thereby forming side surface  1242  of the molding compound between neighboring semiconductor dies  1220 , but still leaving the individual semiconductor packages attached to one another. 
     In  FIG. 12D , the side surfaces  1205  of the leads between neighboring semiconductor dies  1220  are exposed as a result of the partial singulation process. The singulated semiconductor packages can now be loaded to a plating process. In  FIG. 12E , the bottom surfaces  1215  and the exposed side surfaces  1205  of the leads are plated with a plating material  1250  and  1255 , respectively. As discussed above, the plating material is preferably a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In  FIG. 12F , another partial singulation process is performed on the leadframe strip  1210  in order to complete the singulation of the semiconductor packages. In a preferred embodiment, blades  1262  are used to singulate the semiconductor packages. In some embodiments, the blades  1262  have a different shape than the blades  1260  of the first partial singulation process in  FIG. 12C . Preferably, the blades  1262  are beveled. In some embodiments, the blades  1262  have a different thickness than the blades  1260 . In some embodiments, the blades  1262  have a greater thickness than the blades  1260 . 
       FIG. 12G  shows the finished individual semiconductor packages  1200 , similar to the semiconductor package  200  in  FIG. 2 . Each semiconductor package  1200  has a semiconductor die  1220  and a leadframe  1210  at least partially encased in the molding compound  1240 , with the leads of each leadframe  1210  being accessible to electrical coupling via the plating material  1250  and  1255  over the portions of the leads that are exposed from the molding compound  1240 . Each semiconductor package  1200  has side surfaces that are formed from the molding compound  1240 .  FIG. 12G  shows the side surfaces of semiconductor package  1200  having a first portion  1242 , formed from the first partial singulation blade  1260 , and a second portion  1244 , formed from the second partial singulation blade  1262 . A beveled surface  1246 , formed from the beveled edge of the second partial singulation blade  1262 , extends from the first portion  1242  to the second portion  1244 . 
       FIG. 13  is a cross-sectional perspective view of a partial cutting of a semiconductor package  1300  with both partial and full bevel-edged blade assemblies  1360   a  and  1360   b , respectively, in accordance with some embodiments of the present invention. In  FIG. 13 , semiconductor package  1300  comprises a semiconductor die and a leadframe encased within a molding compound, with the side surface of leads  1320   b  being exposed from the molding compound. During the partial singulation cutting of the semiconductor package  1300 , a cutting blade cuts through the molding compound and/or the leadframe. In  FIG. 13 , the cutting blade is shown cutting through the bottom surface  1310   c  of the semiconductor package  1300 , which is positioned with its bottom surface  1310   c  facing upwards. In some embodiments, a partially or fully bevel-edged blade can be used to form a beveled side surface  1315   b  of the semiconductor package  1300 . In some embodiments, the side surface of the semiconductor package  1300  comprises a non-beveled side surface  1310   b  and the beveled side surface  1315   b . In some embodiments, the non-beveled side surface  1310   b  is formed from a straight-edged blade, such as blade  860  shown in  FIG. 8 , and the beveled side surface  1315   b  is formed from a bevel-edged blade, which can either be partially beveled, such as blade  1362   a  of blade assembly  1360   a , or fully beveled, such as blade  1362   b  of blade assembly  1360   b . In some embodiments, the partially bevel-edged blade  1362   a  and the fully bevel-edged blade  1362   b  extend from shanks  1364   a  and  1364   b , respectively. In some embodiments, the shanks  1364   a  and  1364   b  are used to hold and manipulate the blades  1362   a  and  1362   b , respectively. As seen in  FIG. 13 , partially beveled blade  1362   a  comprises a non-beveled portion extending from the shank  1364   a  to a beveled portion, while fully beveled blade  1362   b  is tapered all the way from the shank  1364   b  to its end. 
       FIGS. 14A and 14B  illustrate perspective views of the bottom and top of a semiconductor package  1400  having a beveled side surface formed with a partial bevel-edged blade in accordance with some embodiments of the present invention. Semiconductor package  1400  is almost identical to semiconductor package  900 , except that semiconductor package  1400  has a beveled side surface  1414   b . Semiconductor package  1400  has a top surface  1410   a , a bottom surface  1410   c  opposite the top surface  1410   a , and side surfaces between top surface  1410   a  and bottom surface  1410   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  1420   a  and side surfaces  1420   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  1430  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  1420   a , side surfaces  1420   b , and region  1430  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces of the semiconductor package  1400  have a first portion  1410   b , formed from a first partial singulation blade, and a second portion  1412   b , formed from a second partial singulation blade that is thicker than the first partial singulation blade. Additionally, the second partial singulation blade is a partially bevel-edged blade, such as blade  1362   a  in  FIG. 13 . As a result of the second singulation blade using a partially bevel-edged blade, a beveled side surface  1414   b  is formed on the side of the semiconductor package  1400  between the first portion  1410   b  and the second portion  1412   b , which are non-beveled. 
       FIGS. 15A and 15B  illustrate perspective views of the bottom and top of a semiconductor package  1500  having a beveled side surface with a first height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. Semiconductor package  1500  is almost identical to semiconductor package  900 , except that semiconductor package  1500  has a beveled side surface  1512   b . Semiconductor package  1500  has a top surface  1512   a , a bottom surface  1510   c  opposite the top surface  1510   a , and side surfaces between top surface  1510   a  and bottom surface  1510   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  1520   a  and side surfaces  1520   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  1530  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  1520   a , side surfaces  1520   b , and region  1530  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces of the semiconductor package  1500  have a first portion  1510   b , formed from a first partial singulation blade, and a second portion  1512   b , formed from a second partial singulation blade. The first portion  1510   b  is non-beveled. The second partial singulation blade is a full bevel-edged blade, such as blade  1362   b  in  FIG. 13 . As a result of the second singulation blade using a full bevel-edged blade, a beveled side surface  1512   b  is formed on the side of the semiconductor package  1500 . 
       FIGS. 16A and 16B  illustrate perspective views of the bottom and top of a semiconductor package  1600  having a beveled side surface with a second height formed with a full bevel-edged blade in accordance with some embodiments of the present invention. Semiconductor package  1600  is almost identical to semiconductor package  1500 , except for the height of the beveled portion of its side surface. Semiconductor package  1600  has a top surface  1610   a , a bottom surface  1610   c  opposite the top surface  1610   a , and side surfaces between top surface  1610   a  and bottom surface  1610   c , preferably all formed by a molding compound. A leadframe is encased in the molding compound, with the top surfaces  1620   a  and side surfaces  1620   b  of its leads being exposed. In some embodiments, the leads are copper. However, it is contemplated that other materials besides copper can be used to form the leads. In some embodiments, the region  1630  of the leadframe corresponding to the die attach pad of the leadframe is also exposed. The top surfaces  1620   a , side surfaces  1620   b , and region  1630  are plated with a plating material. In some embodiments, the plating material on the surfaces is a material configured not to react with oxygen. In some embodiments, the plating material is a metallic material. In some embodiments, the plating material is tin. Other materials that can be used as the plating material include, but are not limited to, silver, gold, nickel-gold, nickel-palladium, and nickel-palladium-gold. 
     In some embodiments, the side surfaces of the semiconductor package  1600  have a first portion  1610   b , formed from a first partial singulation blade, and a second portion  1612   b , formed from a second partial singulation blade. The first portion  1610   b  is non-beveled. The second partial singulation blade is a full bevel-edged blade, such as blade  1362   b  in  FIG. 13 . As a result of the second singulation blade using a full bevel-edged blade, a beveled side surface  1612   b  is formed on the side of the semiconductor package  1600 . 
     As mentioned above, semiconductor package  1600  is almost identical to semiconductor package  1500 , except for the height of the beveled side surface. The first portion  1510   b  and the beveled portion  1512   b  of the side surfaces in  FIGS. 15A-B  are substantially equal in height, whereas the first portion  1610   b  of the side surface in  FIGS. 16A-B  is substantially smaller in height than the second portion  1612   b  of the side surfaces in  FIGS. 16A-B . 
     The variations in cutting shapes and heights discussed above and shown in the figures can be achieved by varying the shape of the cutting blade and its cutting depth. 
     The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be readily apparent to one skilled in the art that other various modifications may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention as defined by the claims.

Technology Classification (CPC): 7