Abstract:
The present invention directs to fabrication methods of single-sided or double-sided multi-layered substrate by providing a lamination structure having at least a core structure and first and second laminate structures stacked over both surfaces of the core structure. The core structure functions as the temporary carrier for carrying the first and second laminate structures through the double-sided processing procedures. By way of the fabrication methods, the production yield can be greatly improved without increasing the production costs.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chip package structure and a fabricating method thereof. More particularly, the present invention relates to a fabrication method of a multi-layered substrate and the multi-layered substrate thereof. 
     2. Description of Related Art 
     The board on chip (BOC) packaging concept, which uses a board substrate mounted above the silicon chip(s) as the lead-on-chip (LOC) technology, has been developed for high frequency applications. The BOC substrates or certain window ball grid array (BGA) substrates are essentially single-sided substrates i.e. circuit patterns and fiducials are only located on one side of the substrates. At present, rather wasteful approaches are employed to fabricate these single-sided substrates, as the dummy side of the substrates went through the similar processing steps and then removed. Therefore, not only the raw materials and processing chemicals are wasted but also the efforts spent on the dummy side become futile. 
     It is desirable to develop suitable manufacturing procedure for such substrate using the present manufacturing line. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a fabrication method of a multi-layered substrate, which is capable of doubling the productivity or yield and is compatible with the present manufacturing processes. 
     The present invention is also directed to a fabrication method of fabricating a multi-layered substrate structure, which can provide single-sided or double-sided substrate structure. 
     As embodied and broadly described herein, the present invention directs to a method of fabricating a multi-layered substrate by providing a double-sided lamination structure having at least a core structure and first and second laminate structures stacked over both surfaces of the core structure. The core structure functions as the temporary carrier for carrying the first and second laminate structures through the double-sided processing procedures. 
     The laminate structure can be either a single-clad laminate having a metal layer at one side or a double-clad laminate having two metal layers respectively at both sides. 
     As embodied and broadly described herein, when the first and second laminate structures are single-clad laminates, after the two outermost metal layers of the double-sided lamination structure are patterned and protected with mask layers, single-sided substrates are obtained by separating the first and second laminate structures from the core structure. 
     As embodied and broadly described herein, when the first and second laminate structures are double-clad laminates, after the two outermost metal layers of the double-sided lamination structure are patterned and protected with mask layers, the first and second laminate structures are separated from the core structure, turned inversely and re-laminated to a carrier for further processing. The metal layer at the other side of the first/second laminate structure can be either removed or further patterned to provide single-sided substrates or double-sided substrates. 
     In an embodiment of the present invention, the fabrication method may further comprise forming a plurality of plated-through holes in the double-sided lamination structure by drilling and plating. 
     In an embodiment of the present invention, the fabrication method may further comprise performing a surface plating process to form a Ni/Au layer located on the metal layer that is not covered by the mask layer. 
     The present invention further provides a multi-layered substrate structure. The substrate structure includes a base having a top surface, a bottom surface, and at least a through-hole passing through the base, patterned first and second metal layers formed respectively on the bottom surface and the top surface of the base, a first plating layer covering a sidewall of the through-hole and the bottom surface surrounding a bottom opening of the through hole, and a second plating layer covering the first plating layer and the top surface surrounding the top opening of the through hole. 
     In the present invention, the multi-layered substrate structure has the plated-through holes with double plating layers, which reinforces the plated-through holes for better electrical performances 
     In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is flow chart of process steps for fabricating a substrate according to an embodiment of the present invention. 
         FIGS. 2A-2G  are cross-sectional views showing the substrate according to the fabricating process steps of an embodiment in the present invention. 
         FIG. 3  is flow chart of process steps for fabricating a multi-layered substrate according to another embodiment of the present invention. 
         FIGS. 4A-4G  are cross-sectional views showing the multi-layered substrate according to the fabricating process steps of another embodiment in the present invention. 
         FIG. 5  shows a cross-sectional view of an example of the double-sided substrate structure of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention is described below in detail with reference to the accompanying drawings, and the embodiments of the present invention are shown in the accompanying drawings. However, the present invention can also be implemented in a plurality of different forms, so it should not be interpreted as being limited in the following embodiments. Actually, the following embodiments are intended to demonstrate and illustrate the present invention in a more detailed and completed way, and to fully convey the scope of the present invention to those of ordinary skill in the art. In the accompanying drawings, in order to be specific, the size and relative size of each layer and each region may be exaggeratedly depicted. 
     It should be known that although “first”, “second” and the like are used in the present invention to describe each element, region, layer, and/or part, such words are not intended to restrict the element, the region, the layer, and/or the part, but shall be considered to distinguish one element, region, layer, or part from another. Therefore, under the circumstance of without departing from the teaching of the present invention, the first element, region, layer, or part can also be called the second element, region, layer, or part. 
     In addition, “under”, “on”, and similar words for indicating the relative space position are used in the present invention to illustrate the relationship between a certain element or feature and another element or feature in the drawings. It should be known that, beside those relative space words for indicating the directions depicted in the drawings, if the element in the drawing is inverted, the element described as “under” another element or feature becomes “on” another element or feature. 
       FIG. 1  is flow chart of process steps for fabricating a substrate according to an embodiment of the present invention.  FIGS. 2A-2G  are cross-sectional views showing the substrate according to the fabricating process steps of an embodiment in the present invention. 
     Firstly, in Step  10  &amp;  FIG. 2A , a double-sided lamination structure  100  is provided, which has a first metal layer  106   a  and a first passivation or dielectric layer  104   a  disposed on a top surface  102   a  of the core structure  102  and a second metal layer  106   b  and a second passivation layer  104   b  disposed on a bottom surface  102   b  of the core structure  102 . The material of the first and the second metal layers  106   a ,  106   b  may be copper formed by electroplating or copper foil lamination, for example. The first and second passivation layers may be formed from the same or different resin materials, for example. The core structure  102  may be a release film or a peelable mask film, for example. The release film may be made of a Teflon-based material (such as Tedlar® film), and has very limited adhesion toward the passivation layer. If the release film is used, adhesive resin may be applied on the corners or the borders of the release film for enhancing the adhesion. If the peelable mask film is employed, the peelable mask film should achieve sufficient adhesion with the passivation layer during processing and remain peelable at the end of processing. For example, the peelable mask film can be applied on the borders (shaped as the picture frame) of the passivation layers. 
     In Step  12  &amp;  FIG. 2B , a drilling process is performed by, for example, mechanical drilling or laser drilling to form through holes passing through the double-sided lamination structure  100 . Then, an optional plating process is performed to electroplate the sidewalls of the through holes so as to form plated-through holes  108 . The plating step may also be used to reinforce the Cu foil only. 
     In Step  14  &amp;  FIG. 2C , after first and second patterned photoresist layers  110   a ,  110   b  are respectively formed on the first and second metal layers  106   a ,  106   b , the first and second metal layers  106   a ,  106   b  are patterned, using the first and second patterned photoresist layers  110   a ,  110   b  as the etching masks. 
     In Step  16  &amp;  FIG. 2D , after removing the remained first and second patterned photoresist layers  110   a ,  110   b , first and second mask layers  112   a ,  112   b  are respectively formed on the first and second passivation layers  104   a ,  104   b  and partially covering the first and second metal layers  106   a ,  106   b . The first and second mask layers may be solder mask layers, for example. 
     In Step  18  &amp;  FIG. 2E , a surface plating process is performed to form a nickel/gold layer  114   a/b  on the exposed surfaces of the first and second metal layers  106   a ,  106   b  respectively. 
     In Step  20  &amp;  FIG. 2F , a punching/routing process may be performed to cut bond channels into the substrates to form a BOC type substrate. In the same pass or in a separate punching/routing pass, the strips may be cut from the panel or the border frame of the double-sided lamination structure  100  may be cut off. 
     In Step  22  &amp;  FIG. 2G , a separating process is performed to the double-sided lamination structure  100 , so that two single-sided substrate structures  120   a ,  120   b  are obtained. The first single-sided substrate structure  120   a , including the first passivation layer  104   a , the patterned first metal layer  106   a , the first mask layer  112   a  and the first nickel/gold layer  114   a , is detached from the top surface  102   a  and separated from the core structure  102 . Similarly, the second single-sided substrate structure  120   b , including the second passivation layer  104   b , the patterned second metal layer  106   b , the second mask layer  112   b  and the second nickel/gold layer  114   b , is detached from the bottom surface  102   b  and separated from the core structure  102 . If strips were punched/routed out of the panel, then the separating process forms individual strips. If only the border was cut off, then individual panels are formed which need to be cut into strips in a later process step. 
     According to the fabrication process of the present invention, metal layers and passivation layers can be stacked on both surfaces of the temporary carrier as the double-sided lamination structure, and both sides of the lamination structure can be processed and then separated to provide single-sided substrates. As the single-sided substrates are detached from the temporary carrier, the bottom surface or the blank backside of the single-sided substrates is protected by the temporary carrier and turns out to be a pretty smooth surface, having a roughness R z ≦5 um, for example. That is, the bottom surface or the blank backside of the single-sided substrates is significantly smoother than the conventional backside where copper has been etched or polished. 
       FIG. 3  is flow chart of process steps for fabricating a multi-layered substrate according to another embodiment of the present invention.  FIGS. 4A-4G  are cross-sectional views showing the multi-layered substrate according to the fabricating process steps of another embodiment in the present invention. 
     Firstly, in Step  30  &amp;  FIG. 4A , a double-sided lamination structure  300  is provided, which has a first laminate structure  310   a  disposed on a top surface  302   a  of the core structure  302  and a second laminate structure  310   b  disposed on a bottom surface  302   b  of the core  302  structure. The first laminate structure  310   a  includes a first metal layer  306   a , a second metal layer  308   a  and a first passivation layer  304   a  sandwiched there-between, while the second laminate structure  310   b  includes a third metal layer  306   b , a fourth metal layer  308   b  and a second passivation layer  304   b  sandwiched there-between. The first and second laminate structures  310   a ,  310   b  may be copper clad laminates (CCL), and the material of the metal layers may be copper formed by electroplating or copper foil lamination, for example. The first and second passivation layers  304   a ,  304   b  may be formed from the same or different resin materials, for example. The core structure  302  may be a release film or a peelable mask film, for example. 
     The double-sided lamination structure  300  can be formed by joining the core structure  302  with two laminate structures  310   a ,  310   b  in sequence or simultaneously, for example. The release film may be made of a Teflon-based material (such as Tedlar® film), and has very limited adhesion toward the passivation layer or the metal layer. If the release film is employed as the core structure  302 , adhesive resin may be applied on the corners or the borders of the release film for enhancing the adhesion. If the peelabel mask film is employed as the core structure  302 , it is preferred to choose the size or the shape of the peelable mask film for achieving sufficient adhesion and remaining peelable at the end of processing. For example, the peelable mask film can be applied on the borders (shaped as the picture frame) of one or both of the laminate structures  310   a ,  310   b.    
     Alternatively, as shown in FIG.  4 A′, the core structure  302 ′ of the lamination structure  300 ′ is an aluminum layer and the lamination structure  300 ′ can be formed by laminating and pressing the metal layers and the passivation layers to both surfaces of the aluminum layer sequentially or simultaneously, for example. Such lamination structure  300 ′ can be obtained through direct lamination or be commercially available. For the commercially available lamination structure  300 ′, adhesive resin is usually applied on the borders (shaped as the picture frame) of one or both of the laminate structures  310   a ,  310   b.    
     In Step  32  &amp;  FIG. 4B , a drilling process and a plating process are performed to form plated-through holes  310  passing through the double-sided lamination structure  300  ( 300 ′). 
     In Step  34  &amp;  FIG. 4C , after first and second patterned photoresist layers  312   a ,  312   b  are respectively formed on the second and fourth metal layers  308   a ,  308   b , the second and fourth metal layers  308   a ,  308   b  are patterned, using the first and second patterned photoresist layers  312   a ,  312   b  as the etching masks. 
     In Step  36  &amp;  FIG. 4D , after removing the remained first and second patterned photoresist layers  312   a ,  312   b , first and second mask layers  314   a ,  314   b  are respectively formed on the first and second passivation layers  304   a ,  304   b  and partially covering the second and fourth metal layers  308   a ,  308   b . The first and second mask layers may be solder mask layers, for example. 
     In Step  38  &amp;  FIG. 4E , a surface plating process is performed to form a nickel/gold layer  316   a/b  on the exposed surfaces of the second and fourth metal layers  308   a ,  308   b  respectively. Optionally, a protective layer (not shown) may be further formed over both surfaces of the double-sided lamination structure  300  ( 300 ′). 
     In Step  40 , a punching/routing process may be optionally performed to cut off the border frame of the double-sided lamination structure  300  ( 300 ′). 
     In Step  42  &amp;  FIG. 4F , the first and second laminate structures  310   a ,  310   b  are detached from the top and bottom surfaces  302   a ,  302   b  of the core structure  302  ( 302 ′). For the lamination structure  300 , as the border frame is punched off, it is easy to separate the first and second laminate structures  310   a ,  310   b  from the core structure  302  by peeling with or without using an exatco knife blade, for example. For the commercially available lamination structure  300 ′, as the border frame is removed along with the adhesive resin frame, the laminate structures  310   a ,  310   b  can be straightforwardly peeled apart. However, for the directly-laminated lamination structure  300 ′, the separating process may require more force by using radius drums to peel the laminate structures  310   a ,  310   b  from the aluminum layer. Alternatively, for easier split, it is preferred to arrange small pieces of release films at corners before the direct lamination. 
     In Step  44  &amp;  FIG. 4G , the first and second laminate structures  310   a ,  310   b  are re-laminated together. As the first and second laminate structures  310   a ,  310   b  are laminated to a carrier film  320 , the first and third metal layers  306   a ,  306   b  of the first and second laminate structures  310   a ,  310   b  become the external layers (i.e. face the outside). The carrier film  320  can be a peelable film, for example. 
     If the single-sided substrate structure is desired, the obtained first and second laminate structures  310   a ,  310   b  can be further processed to remove the first and third metal layers  306   a ,  306   b . For single sided substrates, PTH plating may be optional. 
     If the double-sided substrate structure is desired, the first and third metal layers  306   a ,  306   b  of the obtained first and second laminate structures  310   a ,  310   b  can be further processed following the above described Steps  32 - 42 . 
       FIG. 5  shows a cross-sectional view of an example of the double-sided substrate structure of the present invention. The double-sided substrate structure  500  includes two patterned metal layers  506 ,  508  respectively disposed on both surfaces of the base  504  and mask layers  505 ,  507  over the patterned metal layers  506 ,  508 . 
     If considering following the above steps to process both metal layers of the structure  500 , it is optional to perform the drilling and plating process twice or just once. If the plated-through holes  510  are drilled twice and plated twice during processing, the resultant plated-through hole  510  has a first plating layer  512   a  covering the sidewall of the through hole and the surface surrounding the bottom opening of the through hole and a second plating layer  512   b  covering the first plating layer and the surface surrounding the top opening of the through hole. It can reinforce the corners of the plated-through holes and increase the total thickness of the plating layers. The material of the first and second plating layer can be copper or copper alloys, for example. 
     According to the fabrication process of the present invention, copper clad laminates can be stacked on both surfaces of the aluminum carrier, the release film, or the peelable mask film as the lamination structure, and the lamination structure can be processed and separated to provide pseudo single-sided substrates. In addition, the pseudo single-sided substrates can be re-laminated and processed (the other side) to provide single-sided or double-sided substrates. 
     To sum up, the fabrication process of the present invention can efficiently provide single-sided substrates or double-sided substrates based on the currently standard two-layer manufacturing technology. Furthermore, the productivity can be practically doubled without wasting the processing materials or the production line. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.