Abstract:
The invention achieves the above-identified object by providing a packaging, comprising steps of: (a) providing an integrated circuit unit having an active surface, a plurality of bumps disposed thereon; (b) providing a substrate having a first surface and a second surface, a plurality of pads disposed on the first surface, a metal layer formed on the second surface; (c) forming an integrated circuit assembly by connecting the bumps and pads; and (d) forming a plurality of metallic pieces by etching the metal layer.

Description:
[0001]     This application claims the benefit of Taiwan Application Serial No. 094118965, filed Jun. 8, 2005, the subject matter of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates in general to a packaging method and a package using the same, and more particularly to a packaging method using a coreless substrate and a package having a coreless substrate  
         [0004]     2. Description of the Related Art  
         [0005]     Referring to  FIG.1 , a cross-sectional view of a conventional flip-chip package. The conventional flip-chip package is a substrate and a flip chip both of which are jointed by welding. The conventional flip chip package includes a die  10  and a substrate  20 . The substrate  20  has several patterned wiring layers  24  (such as  24   a ,  24   b ,  24   c ), several insulation layers  26  (such as  26   a ,  26   b ,  26   c ), and a core layer  40 . Wiring layers  24  and insulation layers  26  are alternately stacked on the core layer  40  and covers the through hole  46  to construct a predetermined interconnecting wiring structure. Several plugs  36  penetrating the insulation layers  24  electrically connect the respective wiring layers  24 . In general, two types of plugs  36  is classified into via plug  36   a  and plating through hole (PTH) plug  36   b.    
         [0006]     In addition, the substrate  20  includes several bump pad  30  for connecting the bumps  16  oh the die  10  and several ball pads  34  on the bottom surface. The bump pads  30  are individually electrically connected to ball pads  34  through the interconnecting wiring structure. Besides, the substrate  20  further includes a under ball metallurgy (UBM)  40  and solder ball  44  for connecting another substrate, such as printed circuit board. However, the substrate including the core layer is thick, and the size of the package including this kind of substrate will be also increased. The force of the core layer  40  which is much thicker than wiring layer and insulation layer will be greatly reduced after forming the through hole, so that of the core layer  40  has to remains thick for providing sufficient support. It is therefore difficult to reduce the thickness of the substrate and also to shrink the size of the package. On the other hand, the step of forming solder ball is performed by putting the whole package in the reflow oven and reflowing cubic metal at high temperature for long time, so that the conventional package, including the substrate and the chip, is subject to damage by heat. It deteriorates the quality and shortens lifetime of the product.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the foregoing, it is an object of the present invention to provide a method for packaging and a package using the same. It is the metal layer for supporting conductive layers and insulation films in the preceding steps that will be etched as many metallic pieces in the after step. Thus, the complicated and harmful steps for forming solder ball can be omitted. In addition, the size and thickness of the package will be much smaller and thinner if a coreless substrate is applied in the package.  
         [0008]     The invention achieves the above-identified object by providing a packaging, comprising steps of: (a) providing an integrated circuit unit having an active surface, a plurality of bumps disposed thereon; (b) providing a substrate having a first surface and a second surface, a plurality of pads disposed on the first surface, a metal layer formed on the second surface; (c) forming an integrated circuit assembly by connecting the bumps and pads; and (d) forming a plurality of metallic pieces by etching the metal layer.  
         [0009]     It is another object of the invention to provide a package, comprising: a coreless substrate having a first surface and a second surface, a plurality of metallic pillar disposed on the second surface, wherein the metallic pillars comprise copper; and an integrated circuit unit electrically connected to the substrate and positioned on the first surface.  
         [0010]     Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     FIG. 1  is a cross-sectional view of a conventional flip-chip package;  
         [0012]     FIGS.  2 A˜ 2 E illustrate a packaging method according to the embodiment one of the present invention.  
         [0013]     FIGS.  3 A˜ 3 E are top view illustrating the wafer level chip size packaging method according to the embodiment two of the invention.  
         [0014]     FIGS.  4 A˜ 4 C illustrates the packaging method according to embodiment three of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
         [0016]     The present invention is provided a packaging method and a package structure using the same, in which metallic pieces for electrically connecting are formed by etching a metal layer disposed under the substrate. It allows to not only reduce the thickness of the substrate but also simplify the manufacturing procedure and saving the cost.  
         [0017]     Embodiment One  
         [0018]     Referring to FIGS.  2 A˜ 2 E, these illustrate a packaging method according to the embodiment one of the present invention. It is noted that the substrate completely shown in  FIG. 2A  will be simplified in  FIG. 2B ˜ 2 E to make the whole package clear. The packaging method of the present embodiment includes following steps. Firstly, an integrated circuit unit  110  and a substrate  120  are provided as shown in  FIG. 2A . The integrated circuit unit  110 , such as die, semiconductor unit or wafer, has an active surface  111 , and several bumps  112  are disposed on the active surface  111 . On the other hand, the substrate  120  has a first surface  120   a  and a second surface  120   b . Several pads  133  are disposed on the first surface  120   a  and relative to bumps, and a metal layer  130  is formed on the second surface  120   b . Preferably, the metal layer  130  comprises copper.  
         [0019]     Then, the integrated circuit unit  110  is flipped so as to allow bumps  112  to be opposite to pads  122 , and bumps  112  is connected to the pads  122 , i.e. by welding, to form an integrated circuit assembly as shown in  FIG. 2B . If the integrated circuit units  110  are several unpackaged and singulated dies, they will be respectively put on the substrate  120  so as to allow bumps  112  to be opposite to pads  122 , and then dies and the substrate  120  are connected to each other by welding bumps  112  into pads  122 .  
         [0020]     Next, a dam  124  is formed on the first surface  120   a  of the substrate, and positioned around the integrated circuit unit  110  as shown in  FIG. 2C . Afterward, an underfill  126 , such as liquid adhesive, is added between the integrated circuit unit  110  and substrate  120 , and limited within the dam  124  as shown in  FIG. 2D .  
         [0021]     In addition, several metallic pieces  132  are formed by etching the metal layer  130 . For example the metallic pieces  132  etched from the metal layer  130  including copper are several copper pillars as shown in  FIG. 2E . The conductivity of the copper pillar is better than the conventional solder ball. Also, the complicated and harmful steps for forming solder ball can be omitted. The step of forming solder ball is performed by putting the whole package in the reflow oven and reflowing cubic metal at high temperature, so that the conventional package is subject to damage by heat. The package of the present invention, whose metallic pieces are made by etching the metal layer instead, therefore owns good quality and elongated lifetime. The packaging method preferably further includes a step of forming a protective layer, such as an organic solderability preservative (OSP), on the metallic. It prevents the metallic pieces from oxidation, so allows to avoid the disconnect problem between metallic pieces and another substrate in the process of next packaging level.  
         [0022]     Finally, the integrated circuit assembly is divided into several packages by sawing.  
         [0023]     It is noted that the substrate  120  can be either a general substrate with a core layer or a coreless substrate. The substrate  120  is preferably a coreless substrate because the package using a coreless substrate is much thinner that conventional one. Referring to  FIG. 2A , the coreless substrate  120  is an electrical interconnecting structure consists of several complex layers, each of which includes a substrate without a core layer and a predetermined wiring layout formed thereon. Every two conductive wiring layer are insulated by one insulation layer, and electrically connected to each other thorough a filled via-hole embedded in the insulation layer. The substrate is preferably the metal layer  130  for supporting several thin and soft conductive layers and insulation films from being broken.  
         [0024]     The method for forming electrical interconnecting structure is stated below. Referring to  FIG. 2A , a first conductive layer  141  is formed on the metal layer  130  for developing the wire upward, and an insulation film is formed thereon. Next, a via-hole is formed in the insulation film, and then a second conductive layer  142  is formed on the first conductive layer  141  and insulation film by sputtering, depositing, physically or chemically method. After the second conductive layer  142  is patterned, another insulation film is formed thereon. The second conductive layer  142  extends horizontally and fans in to area so as to be opposite to the bumps of the die, and is electrically connected to the first conductive layer  141  through the filled via-hole. In the same way, a third conductive layer  143  is further formed on the second conductive layer  142  and exposed on the first surface  120   a  of the substrate as a pad, which is made to be opposite to the bumps.  
         [0025]     In particular, it is the metal layer for supporting conductive layers and insulation films in the preceding steps that will be etched as many metallic pieces in the after step. Thus, the method of the present embodiment has simplified process, which decreases the cost, and the package to which applies the method owns the substrate of greatly decreased thickness.  
         [0026]     Referring to  FIG. 2E , it is a cross sectional view of the package according to embodiment one of the present invention. The package of the present embodiment includes a coreless substrate  120  and an integrated circuit  110 . The coreless substrate  120  has a first surface  120   a  and a second surface  120   b ; several pads  122  are exposed on the first surface  120   a , and several metallic pieces are exposed on the second surface  120   b . The integrated circuit unit  110  is disposed on the first surface  120   a , and electrically connected to the substrate  120 . The integrated circuit  110  including several bumps  112  is correspondingly connected to the pads  122  on the first surface  120   a  of the substrate, the package stated above is therefore classified as a flipped-chip package. The package further includes underfill  126  filled the space existed between the integrated circuit unit  110  and the substrate  120 . Compared with the conventional package, the package using the coreless substrate is much thinner and smaller so as to allow the whole package or the apparatus containing thereof to be miniaturized.  
         [0027]     Embodiment Two  
         [0028]     It is the integrated circuit unit of the present embodiment that differs from that of the embodiment one. The whole wafer is directly applied to the method for packaging in the present embodiment, as so called wafer level chip size package (WLCSP). Besides, a coreless substrate, whose interconnecting structure is easily made to fit in with the wafer, is preferably applied in the WLCSP method, because the process for manufacturing the coreless substrate is substantially the same as that for the wafer.  
         [0029]     FIGS.  3 A˜ 3 E are top view illustrating the wafer level chip size packaging method according to the embodiment two of the invention. Firstly, a wafer  210  and a coreless substrate  220 , both of which have similar size and electrically interconnect structure matching each other are provided as shown in  FIG. 3A . Next, the whole wafer  210  is flipped and then connected to the coreless substrate  220  as an integrated circuit assembly as shown in  FIG. 3B . The connection of the wafer and the coreless substrate is preferably preformed by welding. Then, a dam  224  is disposed on the coreless substrate  220  and positioned around the wafer  210  as shown in  FIG. 3C . Afterward, an underfill  226 , such as liquid adhesive, is added between the wafer  210  and the coreless substrate  220  and limited within the dam  224  as shown in  FIG. 3D . Next, several metallic pieces  132 , such as copper pillars, are formed by etching the metal layer as shown in  FIG. 3E . Finally, the integrated circuit assembly is divided into several packages by sawing. The WLCSP method of the present embodiment not only owns advantages stated in the preceding embodiment but also can greatly increase the productivity  
         [0030]     Embodiment Three  
         [0031]     It is the metallic piece of the present embodiment that differs from that of the embodiment one, but the other elements remains the same so as to omit the description thereof. FIGS.  4 A˜ 4 C illustrates the packaging method according to embodiment three of the present invention. Firstly, the integrate circuit assembly including an integrated circuit unit  310  and a substrate  320  as shown in  FIG. 4A . Next, several metallic piece, such as ball pads  332 , are formed by etching the metal layer  330  as shown in  FIG. 4B . The metal layer preferably including copper, and ball pads are preferably are several copper pads. Finally, several solder balls  334  are correspondingly formed on the ball pads  332  as shown in  FIG. 4C .  
         [0032]     As described hereinbefore, the packaging method and package using the same has many advantages. It is the metal layer for supporting conductive layers and insulation films in the preceding steps that will be etched as many metallic pieces in the after step. Thus, the method of the present embodiment has simplified process, which decreases the cost, and the package to which applies the method owns the substrate of greatly decreased thickness. Further, it not only provides support in the manufacturing process but also reduces the thickness of the finished package or the apparatus containing the package. Also, the complicated and harmful steps for forming solder ball can be omitted. The step of forming solder ball is performed by putting the whole package in the reflow oven and reflowing cubic metal at high temperature, so that the conventional package is subject to damage by heat. The conductivity of the copper pillar is better than the conventional solder ball. Thus, The package of the present invention, whose metallic pieces are made by etching the metal layer instead, owns good quality and elongated lifetime. In addition, the size and thickness of the package will be much smaller and thinner if a coreless substrate is applied in the package.  
         [0033]     While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.