Patent Publication Number: US-2022223540-A1

Title: Electromagnetic shielding package structure and package method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Chinese Patent Application No. 201910681409.7, filed on Jul. 26, 2019 and entitled “ELECTROMAGNETIC SHIELDING PACKAGE STRUCTURE AND PACKAGE METHOD THEREOF”, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention belongs to the field of semiconductor manufacturing, and in particular relates to an electromagnetic shielding package structure and a package method thereof. 
     BACKGROUND 
     With the trend of multi-functionalization and miniaturization of electronic products, a high-density microelectronic assembly technology has gradually become the mainstream in a new generation of the electronic products. In order to match the development of the new generation of electronic products, especially the development of smart phones, palmtop computers, ultrabooks and other products, an integrated circuit package has also developed in the direction of miniaturization, high density, high power, and high speed. As electronic components become smaller and work at higher frequencies, high-frequency chips will generate strong electromagnetic waves during transportation and transmission, which will usually cause an unexpected interference or noise to other chips in the package or electronic components outside the package. In addition, since the density of the electronic components is too high, and signal transmission lines between the electronic components are closer and closer, the electromagnetic interference from the chips outside or inside the integrated circuit package is more and more serious. Meanwhile, the electrical quality and the heat dissipation efficiency of the integrated circuit package are reduced accordingly. 
     In order to solve the problem of electromagnetic interference, in the prior art, usually, a metal cover is bonded or a metal layer is plated on the outer surface of the package to shield the emission and reception of electromagnetic waves. In the existing molding process of the package with a shielding cover, functions are realized by a substrate package mostly. The main reason is that a substrate processing technology adopts a copper clad laminate as a carrier plate, and after exposure, development, electroplating, etching and other processes, a functional line can be reserved within a cutting line, and a grounding line can extend outside the cutting line to achieve an electromagnetic shielding effect. The cost of using the substrate to achieve the shielding effect is very high, and is about 10 times higher than the cost of packaging on a base plate made of a copper raw material. In addition, in the case of using the substrate as the carrier plate, the reliability is low and the thermal conductivity is poor since raw materials used in the substrate contain a core material and ink. Compared with the package formed by packaging on the base plate made of a copper raw material, the reliability is relatively poor, only MSL3 is achievable, and the thermal conductivity is also relatively poor. 
     Therefore, it is necessary to provide a technology and a package which use the base plate made of a copper raw material as the carrier plate, and perform packaging and shielding thereon, so as to improve performance of the package and reduce a manufacturing cost. 
     SUMMARY 
     Objects of the present invention are to provide an electromagnetic shielding package structure and a package method thereof that solve the above technical problems. 
     In order to achieve one of the above objects of the present invention, an embodiment of the present invention provides a package method for an electromagnetic shielding package structure. 
     The method includes: S 1 , providing a base plate made of a copper raw material; 
     S 2 , performing electroplating in an electroplating area of the base plate to form an electroplating layer on the base plate; 
     S 3 , performing etching on the base plate on which the electroplating layer is formed to wholly form a transition layer, wherein the transition layer includes: pins, conductive connecting ribs of which one ends are connected to the pins and the other ends extend to a singulated cutting line, and the etched electroplating layer, and the pins include: functional pins and grounding pins; 
     S 4 , bonding a high temperature-resistant protective film on the back surface of the transition layer; 
     S 5 , mounting a chip on the front surface of the transition layer, and electrically connecting the chip to the functional pins; 
     S 6 , performing first encapsulating on the front surface of the transition layer; 
     S 7 , peeling off the high temperature-resistant protective film covering the back surface of the transition layer; 
     S 8 , etching the conductive connecting ribs connected to the functional pins from the back surface of the transition layer to form several grooves at the positions corresponding to the etched conductive connecting ribs, so that the transition layer excluding the electroplating layer forms a circuit layer; wherein the circuit layer includes: the functional pins, the grounding pins, and the conductive connecting ribs connected to all the grounding pins respectively; 
     S 9 , performing secondary encapsulating from the back surface of the circuit layer, wherein an encapsulation area at least includes the grooves formed in step S 8 ; 
     S 10 , cutting a half-formed package formed in step S 9  from the singulated cutting line to form several singulated packages; and 
     S 11 , sputtering a metal protective layer uniformly on a plastic package cover of the singulated package to form a shielding cover, and enabling the conductive connecting ribs and the shielding cover to be conducted to form an electromagnetic shielding package structure. 
     As a further improvement of an embodiment of the present invention, step S 1  specifically includes: 
     S 1 - 1 , providing a copper coil raw material; and 
     S 1 - 2 , performing acid washing or alkali washing pretreatment on a copper surface to clean the copper surface to acquire the base plate. 
     As a further improvement of an embodiment of the present invention, step S 2  specifically includes: 
     S 21 , bonding a photoresist film on the base plate; 
     S 22 , removing part of the photoresist film through an exposure machine and a development machine to expose the electroplating area on the base plate; 
     S 23 , electroplating nickel, palladium, gold or silver in the electroplating area of the base plate; and 
     S 24 , peeling off the remaining photoresist film on the base plate. 
     As a further improvement of an embodiment of the present invention, step S 3  specifically includes: 
     S 31 , bonding the photoresist film on the base plate on which the electroplating layer is formed; 
     S 32 , removing part of the photoresist film through the exposure machine and the development machine to expose an etching area; 
     S 33 , etching off the base plate in the etching area to reserve the transition layer bonded to the photoresist film; and 
     S 34 , peeling off the remaining photoresist film to form the transition layer. 
     As a further improvement of an embodiment of the present invention, between step S 3  and step S 4 , the method further includes: dividing the transition layer formed in step S 3  into strips with a punch mold or router manner. 
     As a further improvement of an embodiment of the present invention, step S 7  further includes: removing a residual adhesive layer caused by removing the protective film on the back surface of the circuit with a chemical agent. 
     As a further improvement of an embodiment of the present invention, the area of the secondary encapsulation further includes: a non-plastic package area between the electroplating layers on the back surface of the circuit layer. 
     As a further improvement of an embodiment of the present invention, the metal protective layer sputtered on the plastic package cover of the singulated package sequentially includes an inner stainless steel layer, a copper layer, and an outer stainless steel layer from inside to outside. 
     In order to achieve one of the above objects of the present invention, an embodiment of the present invention provides an electromagnetic shielding package structure, wherein the electromagnetic shielding package structure includes: a circuit layer made of a copper material, wherein the circuit layer includes functional pins, grounding pins, and conductive connecting ribs connected to all the grounding pins respectively and extending toward the side surface of the electromagnetic shielding package structure; 
     a shielding cover disposed on the front surface of the circuit layer and forming a cavity with the circuit layer, wherein the side wall of the shielding cover extends to the side surface of the circuit layer and is connected to each of the conductive connecting ribs; 
     an electroplating layer disposed on the front surface and the back surface of the circuit layer; 
     a chip disposed in the cavity and electrically connected to the functional pins; and 
     a plastic package material filling a gap between the cavity and the circuit layer, wherein the plastic package material isolates the shielding cover from contacting the functional pins. 
     As a further improvement of an embodiment of the present invention, the side wall of the shielding cover extends to the electroplating layer; and 
     the plastic package material is further configured to fill a gap between the electroplating layers. 
     Compared with the prior art, in the electromagnetic shielding package structure and the package method thereof according to the present invention, the transition layer is directly formed on the base plate made of a copper raw material, the first encapsulating is performed on the transition layer, the conductive connecting ribs connected to the functional pins are removed by the etching process, and the secondary encapsulating is performed to fill the grooves of the conductive connecting ribs, so that the functional pins are wrapped in the plastic package material, the grounding pins are electrically connected to the shielding cover on the outer wall surface of the plastic package body through the conductive connecting ribs, and further the grounding pins inside the plastic package body are connected to a shielding metal to realize shielding, thereby improving the performance of the package, and reducing the manufacturing cost and use cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic flowchart of a package method for an electromagnetic shielding package structure according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram corresponding to steps of the package method shown in  FIG. 1  according to the present invention; 
         FIGS. 3 and 4  are respectively schematic structural diagrams of a connection relationship between conductive connecting ribs and pins in the forming process of an electromagnetic shielding package structure according to the present invention; 
         FIG. 5  is a schematic structural diagram of a WB-type package product; 
         FIG. 6  is a schematic structural diagram of an FC-type package product; 
         FIG. 7  is a schematic structural diagram of an SMT-type package product; 
         FIG. 8  is a partially schematic structural diagram of an electromagnetic shielding package structure in a forming process in another embodiment of the present invention; 
         FIG. 9  is a schematic structural diagram of an electromagnetic shielding package structure packaged by the package method described in  FIG. 8 ; and 
         FIG. 10  is a schematic structural diagram of an electromagnetic shielding package structure packaged by the package method described in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the present invention will be described in detail in combination with specific embodiments shown in the drawings. However, the present invention is not limited to these embodiments, and the structural, method, or functional changes made by those skilled in the art according to these embodiments are all contained in a protection scope of the present invention. 
     In combination with  FIGS. 1 and 2 , an embodiment of the present invention provides a package method for an electromagnetic shielding package structure, the method includes: 
     S 1 , providing a base plate  10  made of a copper raw material; 
     S 2 , performing electroplating in an electroplating area of the base plate  10  to form an electroplating layer  20  on the base plate  10 ; 
     S 3 , performing etching on the base plate  10  on which the electroplating layer  20  is formed to wholly form a transition layer, wherein in combination with  FIG. 3  which mainly shows conductive connecting ribs in the transition layer, the transition layer at least includes: pins  31 , the conductive connecting ribs  33  of which one ends are connected to the pins  31  and the other ends extend to a singulated cutting line, and the etched electroplating layer  20 , and the pins  31  include: functional pins  31   a  and grounding pins  31   b;    
     S 4 , covering the back surface of the transition layer with a high temperature-resistant protective film  40 ; 
     S 5 , mounting a chip  50  on the front surface of the transition layer, and electrically connecting the chip  50  to the functional pins  31   a;    
     S 6 , performing first encapsulating on the front surface of the transition layer; 
     S 7 , peeling off the high temperature-resistant protective film  40  covering the back surface of the transition layer; 
     S 8 , etching off the conductive connecting ribs  33  connected to the functional pins  31   a  from the back surface of the transition layer to form several grooves  62  at the positions corresponding to the etched conductive connecting ribs, so that the transition layer excluding the electroplating layer  20  forms a circuit layer  30 , wherein in combination with  FIG. 4  which mainly shows the conductive connecting ribs in the circuit layer formed after processing the transition layer, the circuit layer  30  at least includes: the functional pins  31   a , the grounding pins  31   b , and the conductive connecting ribs  33  connected to all the grounding pins  31   b  respectively; 
     S 9 , performing secondary encapsulating from the back surface of the circuit layer  30 , wherein an encapsulation area at least includes the grooves  62  formed in step S 8 ; 
     S 10 , cutting a half-formed package formed in step S 9  from the singulated cutting line to form several singulated packages; and 
     S 11 , sputtering a metal protective layer uniformly on a plastic package cover of the singulated package to form a shielding cover  70 , and enabling the conductive connecting ribs  33  and the shielding cover  70  to be conducted to form an electromagnetic shielding package structure. 
     In a specific embodiment of the present invention, step S 1  specifically includes: S 1 - 1 , providing a copper coil raw material, wherein the thickness of the provided copper coil raw material may be selected according to the thickness of a product, and since the copper raw material is a metal alloy material, the reliability and heat dissipation of an encapsulated product with the copper raw material as a carrier plate can be improved; and S 1 - 2 , performing acid washing or alkali washing pretreatment on a copper surface to clean the copper surface to acquire the base plate  10 . Step S 1  aims to remove lipids and other substances on the copper surface for the purpose of cleaning the copper surface. 
     In a specific embodiment of the present invention, first film bonding is performed in step S 2  for subsequent electroplating. Specifically, step S 2  specifically includes: S 21 , bonding a photoresist film on the base plate  10 , wherein the photoresist film is usually bonded to the front surface and back surface of the base plate  10 , and the photoresist film may be a dry photoresist film or a wet photoresist film; S 22 , removing part of the photoresist film through an exposure machine and a development machine to expose the electroplating area on the base plate  10 , wherein in this step, after pattern exposing and developing are performed at the position where the photoresist film is bonded and removing part of the photoresist film, the copper surface of the base plate  10  is exposed; S 23 , electroplating nickel, palladium, gold or silver in the electroplating area of the base plate  10 ; and S 24 , peeling off the remaining photoresist film on the base plate  10 , wherein in this step, the remaining photoresist film on the base plate  10  can be peeled off with a film peeling solution. It should be noted that the purpose of disposing the conductive connecting ribs  33  in the present invention is to connect the grounding pins  31   b  and the shielding cover  70  through the conductive connecting ribs  33  to achieve shielding. Thus, in this specific embodiment, the conductive connecting ribs  33  connected to the functional pins  31   a  need to be etched off subsequently. In this way, the conductive connecting ribs  33  connected to the functional pins  31   a  are excluded from the electroplating area, that is, when in electroplating, the conductive connecting ribs  33  connected to the functional pins  31   a  do not need to be electroplated, but the conductive connecting ribs connected to the grounding pins  31   b  need to be electroplated when being divided into the electroplating area. 
     In a specific embodiment of the present invention, second film bonding is performed in step S 3 . Specifically, step S 3  specifically includes: S 31 , bonding the photoresist film on the base plate  10  on which the electroplating layer  20  is formed, wherein the photoresist film may also be a dry photoresist film or a wet photoresist film; S 32 , removing part of the photoresist film through the exposure machine and the development machine to expose an etching area, wherein in this step, after pattern exposing and developing are performed at the position where the photoresist film is bonded and removing part of the photoresist film, the copper surface of the base plate  10  is exposed; S 33 , etching off the base plate  10  in the etching area to reserve the transition layer bonded to the photoresist film, wherein in this step, the reserved base plate  10  covered by the photoresist film and the electroplating layer are circuits needing to be reserved; and S 34 , peeling off the remaining photoresist film to form the transition layer. According to different package types, in addition to the pins  31  and the conductive connecting ribs  33 , the transition layer may also include a base island  35 , which will be described in the following. 
     Between step S 3  and step S 4 , the method further includes: dividing the transition layer formed in step S 3  into strips with a punch mold or router manner to facilitate subsequent cutting. 
     For the transition layer formed in step S 4 , respective components may be connected to each other or disconnected. In this way, the high temperature-resistant protective film  40  is bonded to the back surface of the transition layer. The high temperature-resistant protective film  40  is bonded to the back surface of the transition layer, and fills a gap between the electroplating layers  20  on the back surface of the transition layer, so that the respective components are connected through the protective film, which is convenient for subsequent encapsulation and use. 
     For step S 5 , in combination with  FIG. 5 , for a WB-type package product, the chip  50  is disposed on the front surface of the base island  35  through adhesive glue, and then the chip  50  is electrically connected to the functional pins  31   a  via welding wires  51 . 
     In combination with  FIG. 6 , for an FC-type package product, the chip  50  is electrically connected to the pins through bumps  53 . 
     In combination with  FIG. 7 , for an SMT package product, the chip  50  herein is a passive component such as an inductor, a capacitor, a resistor, or a sensor, and is directly welded on the functional pins  31   a.    
     For step S 6 , the first encapsulating is performed from the front surface of the transition layer, plastic packaging of epoxy resin may be performed on the front surface of the transition layer, and a plastic package material  60  fills all the gaps above the high temperature-resistant protective film  40 . 
     Step S 7  corresponds to step S 5 , after the first encapsulation is completed, the temporarily bonded high temperature-resistant protective film  40  needs to be torn off to facilitate the secondary encapsulation. 
     In a preferred embodiment of the present invention, step S 7  further includes: removing a residual adhesive layer caused by removing the protective film on the back surface of the circuit with a chemical agent. The chemical agent, such as potassium hydroxide and organic amine and other mixed alkaline lotion. 
     In step S 8 , on the back surface of the transition layer, the conductive connecting ribs  33  connected to the functional pins  31   a  are not electroplated, and are still the copper surface. The conductive connecting ribs  33  at these positions may be etched off with an etching solution, and the conductive connecting ribs  33  connected to the grounding pins  31   b  are reserved. In this way, the connection between the functional pins  31   a  and the side wall is cut off, and only the connection between the grounding pins  31   b  and the side wall through the conductive connecting ribs  33  is reserved to form the circuit layer  30 . In this step, after the conductive connecting ribs  33  at the corresponding positions are etched off, on the back surface of the product that is not finally formed in step S 7 , the several grooves  62  are formed at the positions corresponding to the etched conductive connecting ribs. The bottom of each groove  62  exposes the plastic package material  60  encapsulated for the first time, and at least one side wall of each groove  62  exposes the functional pin  31   a.    
     In step S 9 , the secondary encapsulating is performed from the back surface of the circuit layer  30 . There are two encapsulation manners. In the example shown in  FIG. 2 , all the gaps above the back surface of the circuit layer  30  are filled with the plastic package material  60 . In the present embodiment, epoxy resin glue is used to fill the back surface of the circuit layer  30 . The filled area includes each groove  62  formed in step S 8  and the area not covered with the plastic package material  60  between the back surface of the circuit layer  30  and the electroplating layer  20 . At this point, through the plastic packaging of the epoxy resin glue, the side wall surface of the package of the chip  50  is stopped from being exposed, so as to facilitate subsequent metal shielding. 
     In combination with  FIG. 8 , when in the secondary encapsulation, the filled area only includes each groove  62  formed in step S 8 , and the non-plastic package area between the electroplating layers  20  on the back surface of the circuit layer  30  is not subjected to secondary plastic packaging. At this point, the side wall surface of the chip  50  is also blocked from being exposed by the plastic packaging of the epoxy resin, so as to facilitate subsequent metal shielding. 
     In step S 10 , with a cutting machine, the product is cut into singles from strip arrangement. At this point, the side wall of the single product is blocked by the plastic package material to prevent the functional pins  31   a  from being electrically connected to the side wall, while under the action of the conductive connecting ribs  33 , the conductive connecting ribs  33  extend to the side wall of the single product, so as to ensure that the grounding pins  31   b  are electrically connected to the side wall, which is convenient for connecting the grounding pins  31   b  to the metal shielding cover  70  subsequently. 
     After step S 10 , the method further includes: cleaning the singulated package to remove foreign matter and/or grease on the surface of the singulated package. The cleaning manner, for example, is alcohol immersion and ultrasonic cleaning. 
     In step S 11 , in combination with  FIGS. 2 and 8 , the plastic package cover of the product includes 5 surfaces except the back surface. In a preferred embodiment of the present invention, the metal protective layer includes 3 layers, which successively include an inner stainless steel layer, a copper layer and an outer stainless steel layer from inside to outside. The purpose of sputtering the inner stainless steel layer is to increase a binding force with the plastic package material, the thickness of this layer is usually 0.1 μm, and the purpose of sputtering the outer stainless steel layer is to protect the middle copper layer from oxidization. The thickness of the middle copper layer is usually 5 to 9 μm, and the thickness of the outer stainless steel layer is usually 0.1 to 0.3 μm. After sputtering the metal protective layer on the outer wall surface of the singulated package, the conductive connecting ribs  33  connected to the grounding pins  31   b  extend to the side wall surface, so that the functional pins  31   b  can be electrically connected to the shielding cover  70  made of a metal material through the conductive connecting ribs  33 . 
     In combination with  FIG. 9  and referring to related illustrations of the above method, an embodiment of the present invention provides an electromagnetic shielding package structure manufactured by the method described above. The electromagnetic shielding package structure includes: a circuit layer  30  made of a copper material, wherein the circuit layer includes functional pins  31   a , grounding pins  31   b , and conductive connecting ribs  33  connected to all the grounding pins  31   b  respectively and extending toward the side surface of the electromagnetic shielding package structure; a shielding cover  70  disposed on the front surface of the circuit layer  30  and forming a cavity with the circuit layer  30 , wherein the side wall of the shielding cover  70  extends to the side surface of the circuit layer  30  and is connected to each of the conductive connecting ribs  33 ; an electroplating layer  20  disposed on the front surface and the back surface of the circuit layer  30 ; a chip  50  disposed in the cavity and electrically connected to the functional pins  31   b ; and a plastic package material  60  filling a gap between the cavity and the circuit layer  30 , wherein the plastic package material  60  isolates the shielding cover  70  from contacting the functional pins  31   a.    
     In combination with  FIG. 10 , in another embodiment of the present invention, the side wall of the shielding cover  70  extends to the electroplating layer  20 ; and the plastic package material  60  is also configured to fill a gap between the electroplating layers  20 . 
     Those skilled in the art can clearly understand that, for the convenience and conciseness of description, the specific structure of the electromagnetic shielding package structure described above and the replacement manners of respective components may refer to the corresponding description in the foregoing method embodiments, which will not repeated herein. 
     In summary, in the electromagnetic shielding package structure and the package method thereof according to the present invention, the transition layer is directly formed on the base plate made of the copper raw material, the first encapsulating is performed on the transition layer, the conductive connecting ribs connected to the functional pins are removed by the etching process, and the secondary encapsulating is performed to fill the grooves of the conductive connecting ribs, so that the functional pins are wrapped in the plastic package material, the grounding pins are electrically connected to the shielding cover on the outer wall surface of the plastic package body through the conductive connecting ribs, and further the grounding pins inside the plastic package body are connected to a shielding metal to realize shielding, thereby improving the performance of the package, and saving the manufacturing cost and use cost. 
     It should be understood that although the present invention is described in terms of embodiments in this description, not every embodiment includes only one independent technical solution. The statement mode of the description is merely for clarity, and those skilled in the art should regard the description as a whole. The technical solutions in various embodiments may also be combined properly to develop other embodiments that can be understood by those skilled in the art. 
     The series of detailed illustration listed above are merely for specifically illustrating the feasible embodiments of the present invention, but not intended to limit the protection scope of the present invention. Any equivalent embodiments or variations made without departing from the technical spirit of the present invention shall fall within the protection scope of the present invention.