Patent Publication Number: US-9899335-B2

Title: Method for fabricating package structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a divisional of copending application U.S. Ser. No. 14/463,999, filed on Aug. 20, 2014, which claims under 35 U.S.C. §119(a) the benefit of Taiwanese Application No. 103125448 filed Jul. 25, 2014, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to package structures, and, more particularly, to a package structure that is protected from electromagnetic interferences and a method for fabricating the same. 
     2. Description of Related Art 
     With the rapid growth in electronic industry, most electronic products have been developed towards the goal for miniaturization and high speed, particularly as the modern communication techniques have been widely incorporated in various electronic products. However, as the electronic products include high frequency chips, and these chips are easily affected by electromagnetic interferences (EMI) due to the adjacent integrated circuits and digital signal processors (DSP), an electromagnetic shielding treatment is often required. 
     A conventional radio frequency (RF) module  1  that is protected from EMI is illustrated in  FIGS. 1A to 1C . A plurality of RF chips  11   a  and  11   b  and non-RF electronic components  11  are electrically connected and incorporated on a packaging substrate  10 . The RF chips  11   a  and  11   b  and the non-RF electronic components  11  are encapsulated by an encapsulating layer  13  such as epoxy resin. A thin metal film  14  is formed on the encapsulating layer  13 . The RF chips  11   a  and  11   b , the non-RF electronic components  11  and the packaging substrate  10  in the RF module  1  can be prevented from damages caused by outside moist or contaminants by the encapsulating layer  13 , and the RF chip  11   a  and  11   b  are protected from EMI via the thin metal film  14 . 
     Although the periphery of the RF module  1  is encapsulated by the thin metal film  14  and protected from EMI, if the RF chips  11   a  and  11   b  are low frequency components, it is difficult for the single thin metal film  14  to protect the RF module  1  from EMI efficiently. 
     Therefore, there is an urgent need for overcoming the drawbacks of the prior art. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing problems, the present invention provides a package structure, comprising: a carrier; at least one electronic component disposed on the carrier; an encapsulant formed on the carrier for encapsulating the electronic components; a first shielding layer formed on the encapsulant; and at least one second shielding layer formed on the first shielding layer, wherein the first shielding layer and the at least one second shielding layer are made of different materials. 
     The present invention further provides a method for fabricating a package structure, comprising: providing a package body that has a carrier, at least one electronic component disposed on the carrier, and an encapsulant formed on the carrier for encapsulating the electronic components; forming a first shielding layer on the encapsulant; and forming at least one second shielding layer on the first shielding layer, wherein the first shielding layer and the at least one second shielding layer are made of different materials. 
     In an embodiment, the package body has a plurality of the electronic components, and is defined with a plurality of package units, each of which has one of the electronic components. In another embodiment, the method further comprises forming a plurality of trenches among the package units; forming the first shielding layer on the encapsulant and in the trenches; performing a singulation process along the trenches for separating the package units, with the first shielding layer remained on the package units; and forming the second shielding layer on the first shielding layer. 
     In an embodiment, the electronic component is an RF chip, the first shielding layer is made of an insulative material or a conductive material, and the second shielding layer is made of a conductive material. 
     In an embodiment, the trenches penetrate the encapsulating layer, or the trenches extend into the carrier. In another embodiment, the first shielding layer is formed along surfaces of the trenches, or the trenches are filled with the first shielding layer. In yet another embodiment, the first shielding layer is further formed on the carrier, the carrier has a step-like periphery that is covered by the first shielding layer, the first shielding layer has a step-like portion corresponding to the step-like periphery, and the side surface of the first shielding layer is flush the side surface of the carrier. 
     In summary, a package structure and a method for fabricating the same according to the present invention feature in forming on the encapsulant a plurality of shielding layers, including the first and second shielding layers, for improving the shielding effect, thereby protecting the electronic components from external electromagnetic interferences. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein: 
         FIGS. 1A-1C  are cross-sectional views illustrating a method for fabricating an encapsulating layer of a conventional RF module; 
         FIGS. 2A-2F  are cross-sectional views illustrating a method for fabricating a package structure in accordance with a first embodiment of the present invention, wherein  FIG. 2D ′ is another embodiment of  FIG. 2D , and  FIG. 2F ′ is another embodiment of  FIG. 2F . 
         FIGS. 3A and 3B  are cross-sectional views illustrating a method for fabricating a package structure in accordance with a second embodiment of the present invention, wherein  FIG. 3B ′ is another embodiment of  FIG. 3B ; 
         FIGS. 4A and 4B  are cross-sectional views illustrating a method for fabricating a package structure in accordance with a third embodiment of the present invention. 
         FIG. 5  is a cross-sectional view illustrating a method for fabricating a package structure in accordance with a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is described in the following with specific embodiments, so that one skilled in the pertinent art can easily understand other advantages and effects of the present invention from the disclosure of the present invention. 
     It should be noted that all the drawings are not intended to limit the present invention. Various modification and variations can be made without departing from the spirit of the present invention. Further, terms, such as “upper”, “lower”, “first”, “second” and “one” etc., are merely for illustrative purpose and should not be construed to limit the scope of the present invention. 
       FIGS. 2A-2F  are cross-sectional views illustrating a method for fabricating a package structure  2  in accordance with a first embodiment of the present invention. The package structure  2  is capable of generating electromagnetic waves, and is a radio frequency (RF) module, for example. 
     As shown in  FIG. 2A , a carrier  20  having an upper surface  20   a  and a lower surface  20   b  is provided, and a plurality of electronic components  21  are disposed on the upper surface  20   a  of the carrier  20 . 
     A circuit layer and an insulative protection layer  201  are formed on the upper surface  20   a  of the carrier  20 . The circuit layer includes a plurality of electrical connection pads  200  that are exposed from the insulative protection layer  201 . In an embodiment, the carrier  20  is in a variety of types, and includes a dielectric layer (not show), a grounding part (not shown) and an inner circuit (not shown) formed inside the carrier  20 , and the inner circuit can be selectively electrically connected with the electrical connection pads  200 . The carrier  20  has no specific limitation. 
     In an embodiment, the electronic components  21  are RF chips or other types of semiconductor chips, such as Bluetooth chips or Wireless Fidelity (Wi-Fi) chips. In an embodiment, the electronic components  21  are Bluetooth chips or Wi-Fi chips, and other electronic components (not shown) that do not cause electromagnetic interferences can be disposed on the upper surface  20   a  of the carrier  20 . 
     In an embodiment, the electronic components  21  are wire bonding chips, and are electrically connected with the corresponding electrical connection pads  200   a  of the carrier  20  using a plurality of bonding wires  210 . 
     As shown in  FIG. 2B , an encapsulant  23  is formed on the upper surface  20   a  of the carrier  20  for encapsulating the electronic components  21 , so as to form a package body  2   a.    
     In an embodiment, the encapsulant layer  23  is an encapsulating adhesive having opposing first surface  23   a  and second surface  23   b , and coupled to the upper surface  20   a  of the carrier  20  via the second surface  23   b  of the encapsulant  23 . 
     In an embodiment, the electronic components  21  are not exposed from the first surface  23   a  of the encapsulant  23 . 
     In an embodiment, the package body  2   a  is defined with a plurality of package unit  2   b , and each of the package units  2   b  has at least one of the electronic components  21 . 
     As shown in  FIG. 2C , a plurality of trenches  230  are formed among of the package units  2   b , allowing a portion of the upper surface  20   a  of the carrier  20  to be exposed from the trenches  230 . 
     In an embodiment, the trenches  230  penetrate the encapsulant  23   b , without extending into the carrier  20 . 
     As shown in  FIG. 2D , a first shielding layer  24  is formed on the first surface  23   a  of the encapsulant  23 . 
     In an embodiment, the first shielding layer  24  is formed along the surface of encapsulant  23  inside the trenches  230 . 
     In another embodiment, as shown in  FIG. 2D ′, the trenches  230  are filled with the first shielding layer  24 ′. 
     In an embodiment, the first shielding layer  24  is made of an insulative material or a conductive material, and the first shielding layer  24  and the encapsulant layer  23  are made of different materials. 
     As shown in  FIG. 2E , the package units  2   b  are singulated out along the trenches  230  in a singulation process, and the first shielding layer  24  is remained on the package units  2   b.    
     In an embodiment, the carrier  20  has a step-like periphery  22  that is constituted by the encapsulant  23 , and the first shielding layer  24  has a step-like portion corresponding to the step-like periphery  22 . 
     As shown in  FIG. 2F , a second shielding layer  25  is formed on the first shielding layer  24  and a side surface  20   c  of the carrier  20 , to form the package structure  2 . In an embodiment, the first shielding layer  24  and the second shielding layer  25  are made of different materials. 
     In an embodiment, the second shielding layer  25  is made of a conductive material, and is formed by a chemical plating method, such as sputtering and coating processes. 
     In an embodiment, the second shielding layer  25  is made of copper (Cu), nickel (Ni), iron (Fe), aluminum (Al), etc. 
     In an embodiment, the second shielding layer  25  is selectively electrically connected to the grounding part of the carrier  20  (since the grounding part is exposed from the side surface  20   c  of the carrier  20 ). 
     In an embodiment, a package structure  2  as shown in  FIG. 2F  is formed after the process illustrated in  FIG. 2D ′, and the side surface  24   a  of the first shielding layer  24 ′ is flush with the side surface  20   c  of the carrier  20 . 
       FIGS. 3A and 3B  are cross-sectional views illustrating a method for fabricating a package structure in accordance with a second embodiment of the present invention, wherein  FIG. 3B ′ is another embodiment of  FIG. 3B . The second embodiment differs from the first embodiment in the depth of the trenches. 
     As shown in  FIG. 3A , a plurality of trenches  330  are formed among the package units  2   b , penetrate the encapsulant  23 , and extend into the carrier  20 . 
     As shown in  FIGS. 3B and 3B ′ and  FIGS. 2D to 2F , a method for fabricating the package structure  3 ,  3 ′ of another embodiment is illustrated. 
     In an embodiment, the carrier  20  has a step-like periphery  22 ′, and the encapsulant  23  is not formed on the step-like periphery  22 ′ of the carrier  20 , allowing the step-like periphery  22 ′ of the carrier  20  to be exposed from the side surface  23   c  of the encapsulant  23 . 
       FIGS. 4A and 4B  are cross-sectional views illustrating a method for fabricating a package structure in accordance with a third embodiment of the present invention. The third embodiment differs from the first and second embodiments in that the trenches are not formed in the third embodiment. 
     As shown in  FIG. 4A , a package body  4   a  is formed that has a carrier  40 , an electronic component  41  disposed on the carrier  40 , and an encapsulant  23  that encapsulates the electronic component  41 . 
     In an embodiment, the electronic component  41  is a flip-chip, and is electrically connected to the corresponding electrical connection pads  200  of the carrier  40  via a plurality of solder balls  410 . 
     As shown in  FIG. 4B , a first shielding layer  24  is formed on the encapsulating layer  23 , and a second shielding layer  25  is formed on the first shielding layer  24 . 
     In an embodiment, the side surface  40   c  of the carrier  40  is flush with the side surface  23   c  of the encapsulant  23 , and the periphery of the carrier  40  does not exceed the side surface  23   c  of the encapsulant  23 . 
       FIG. 5  is a cross-sectional view illustrating a method for fabricating a package structure in accordance with a fourth embodiment of the present invention. The fourth embodiment differs from the first to third embodiments in that the numbers of the electronic components and the second shielding layers. 
     As shown in  FIG. 5 , the package structure  5  has a plurality of electronic components  51  and a plurality of second shielding layers  55 . 
     In an embodiment, the second shielding layers  55  are made of different materials, and the adjacent second shielding layers  55  are made of different materials. 
     With the first shielding layers  24  and  24 ′ and the second shielding layer  25  and  55  formed on the encapsulant  23  to function as an EMI shielding component, the electronic components  21 ,  41 , and  51   a  are protected from electromagnetic interferences from, for example, a Bluetooth chip. 
     Furthermore, if the electronic components  21 ,  41  and  51  are low frequency components, multiple shielding layers provide a better protection result from electromagnetic interferences. 
     A package structure  2 ,  2 ′,  3 ,  3 ′,  4 ,  5  further comprises: a carrier  20 ,  40 , at least one electronic component  21 ,  41 ,  51 , an encapsulant  23 , a first shielding layer  24 ,  24 ′, and at least one second shielding layer  25 ,  55 . 
     The package structure  2 ,  2 ′,  3 ,  3 ′,  4 ,  5  is an RF module. 
     The carrier  20 ,  40  has a plurality of electrical connection pads  200 . 
     The electronic components  21 ,  41 ,  51  are disposed on the carrier  20 ,  40  and are electrically connected with the electrical connection pads  200 . In an embodiment, the electronic component  21 ,  41 ,  51  is an RF chip, such as a Bluetooth chip or a Wi-Fi chip. 
     The encapsulant  23  is formed on the carrier  20 ,  40  and encapsulates the electronic components  21 ,  41 ,  51 . 
     The first shielding layer  24 ,  24 ′ is formed on the encapsulant  23 , and is made of an insulative material. 
     The second shielding layer  25 ,  55  is formed on the first shielding layer  24 ,  24 ′, and the second shielding layer  25 ,  55  and the first shielding layer  24 ,  24 ′ are made of different materials. In an embodiment, the second shielding layer  25 ,  55  is made of a conductive material. 
     In an embodiment, the first shielding layer  25 ,  55  is further formed on the carrier  20 ,  40 . 
     In an embodiment, the carrier  20 ,  40  has a step-like periphery  22 ,  22 ′. Hence, the first shielding layer  24  covers the step-like periphery  22 ,  22 ′, and the first shielding layer  24  has a step-like portion corresponding to the step-like periphery  22 ,  22 ′. 
     The first shielding layer  24 ′ covers the step-like periphery, and the side surface  24   a  of the first shielding layer  24 ′ is flush with the side surface  20   c  of the carrier  20 . 
     In summary, the package structure and a method for fabricating the same feature in forming multiple shielding layers on the encapsulating layer, so as to protect the electronic components from electromagnetic interferences. 
     Moreover, if the electronic component is a low frequency component, multiple shielding layers can provide a better protection result against electromagnetic interferences. 
     The present invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the present invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.