Patent Publication Number: US-2012042513-A1

Title: Manufacturing method of printed circuit board embedded chip

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. divisional application filed under 37 CFR 1.53(b) claiming priority benefit of U.S. Ser. No. 12/230,874 filed in the United States on Sep. 5, 2008, which claims earlier priority benefit of Korean Patent Application No. 10-2008-0060175 filed with the Korea Intellectual Property Office on Jun. 25, 2008, the disclosures of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to an electronic component embedded printed circuit board and a manufacturing method thereof; and more particularly, to an electronic component embedded printed circuit board in which heat emission efficiency is improved by formation of a pit through adjusting fluidity of an insulator in the vicinity of a chip of which a part is buried in an insulation layer and the chip of which a part is buried in the insulation layer may be reutilized in case that the insulation layer is an thermoplastic resin based insulation layer, and a manufacturing method thereof. 
     2. Description of the Related Art 
     Recently, development of a printed circuit board with various types of electronic elements has attracted public attention as a part of a technology for implementing a multi-functioned and small-sized package. 
     Up to now, discrete chip resistors or discrete chip capacitors are individually mounted on surfaces of most of printed circuit boards, but recently, a method of manufacturing a printed circuit board with the electronic elements is a technology of substituting chip elements inserted into an inner layer of the board for passive elements such as the conventional chip resistors and discrete chip capacitors by inserting the chip elements such as the discrete chip resistors or the discrete chip capacitor into the inner layer of the board by using new materials and processes. 
     The board with the electronic elements has high-functionality in addition to merits such as multi-functionality and miniaturization. This is why to provide a measure to enhance a problem in reliability which may occur in wire bonding used in a flip chip or a BGA (Ball Grid Array) or in electrical connection of the electronic elements using a solder ball. 
     In a conventional method of a printed circuit board with electronic elements such as an IC (Integrated Chip), and the like, as a structure in which the electronic elements are incorporated only on one surface of a core board or one surface of a build-up layer is adopted, the printed circuit board cannot help being configured in an asymmetric structure vulnerable to bending under a thermal stress environment. Accordingly, there is a problem that the board is bent in a direction where the electronic elements are positioned under the thermal stress environment. 
     There was a limitation that the printed circuit board cannot incorporate electronic elements having a predetermined thickness or more due to this problem. In addition, there is a limitation that lamination materials used in the printed circuit board cannot be manufactured in a predetermined thickness or less due to an electrical insulation property. In this case, a critical thickness for preventing bending is essentially limitative due to a characteristic of a material. 
     The conventional method of manufacturing the electronic component embedded printed circuit board will now be described in short. First, through-holes having sizes corresponding to sizes of the electronic components to be mounted on a core substrate is formed by providing the core substrate configured by laminating and curing a prepreg on a glass cross. 
     Next, the electronic components are inserted into the through-holes formed on the core substrate and a filler is charged in the through-holes inserted with the electronic components. The electronic component is fixed to the core substrate by curing the filler for approximately 10 minutes and the electronic component is exposed by grinding the filler and the core substrate with a grinding paper. 
     Hereinafter, a resin insulation layer is laminated on the electronic component and a via hole is formed through laser processing or drilling processing. A plating layer is formed by performing electroless plating or electrolyte plating on the insulation layer and a resist pattern is formed by etching, thereby manufacturing an electronic component embedded printed circuit board having a predetermined circuit pattern. 
     Since the electronic component embedded printed circuit board manufactured in such manner is configured in a structure in which the electronic component is buried in a core substrate composed of the insulation layer, heat generated in the electronic components is not smoothly discharged to an outside. 
     In the conventional printed circuit board, since the electronic components are inserted into the through-holes formed on the core substrate, and is fixed and coupled to the core substrate with the filler, the expensive electronic components are disposed in case that mounting errors of the electronic components occur. Therefore, loss in manufacturing cost is increased. 
     Since the through-holes for mounting the electronic components on the core substrate should be manufactured in a predetermined size, process loss is increased and working efficiency is lowered. 
     SUMMARY 
     Accordingly, the present invention is contrived to solve the above-described demerits and problems of a conventional electronic component embedded printed circuit board. An object of the present invention is to provide an electronic component embedded printed circuit board which can maximize a heat radiation characteristic of the electronic component by coupling a part of an electronic component to be exposed by using fluidity of an insulation layer forming a core layer and forming a plating layer surrounding a surface of the exposed electronic component, and reduce a thickness of a printed circuit board by positioning the electronic component in the boundary of the plating layer being in contact with the core layer of the printed circuit board. 
     Another object of the present invention is to provide a method of manufacturing an electronic component embedded printed circuit board in which an electronic component may be mounted on the board by using fluidity of an insulation layer through selective heating of the electronic component or the insulation layer without forming an additional cavity on an insulation layer forming a core layer and the electronic component in which a part of the electronic component is buried may be reutilized in case that the insulation layer is made of a thermoplastic resin. 
     In order to achieve the above-described object, there is provided An electronic component embedded printed circuit board including an insulating layer forming a core layer; an electronic component inserted to project a part thereof on an upper part of the insulating layer; a metallic seed layer formed on the insulating layer including a projected surface of the electronic component; a plating layer formed on the metallic seed layer; circuit patterns electrically connected to pads of the electronic component through via-holes formed on the insulating layer; and a solder resist layer formed on the insulating layer and including solder balls attached onto the via-holes electrically connected to the circuit patterns. 
     The insulating layer may be made of any one of a thermoplastic resin, a thermosetting resin, and a UV curing resin. 
     The electronic component is pressed onto the insulating layer at predetermined pressure by being tightly coupled to absorbing apparatuses such as a vacuum press, and the like, whereby the electronic component is inserted into the insulating layer so that a part of the electronic component is exposed on the insulating layer. 
     At this time, any one of the insulating layer and the electronic component is selectively heated, whereby the insulating layer is granted fluidity when the electronic component and the insulating are coupled to each other. 
     A pit may be formed on the insulating layer in the periphery of the electronic component at the time of press-coupling the electronic component. The metallic seed layer covering an exposed surface of the electronic component is formed on the exposed surface of the electronic component and the insulating with the pit at the time of forming the metallic seed layer on the exposed surface of the electronic component and the insulating layer. 
     In case that the insulating layer is made of the thermoplastic resin, the electronic component is removable by reheating the thermoplastic resin before curing the thermoplastic resin or after curing the thermoplastic resin by cooling, thereby reutilizing the electronic component. 
     Meanwhile, the metallic seed layer is formed on the surface of the electronic component, which is exposed on the insulating layer. The plating layer having a predetermined thickness is formed on the metallic seed layer. 
     At this time, the metallic seed layer may be formed by evaporation, electroless plating, or sputtering. The plating layer formed on the metallic seed layer may be formed by electrolytic plating. 
     In order to achieve another object of the present invention, there is provided a method of manufacturing an electronic component embedded printed circuit board including the steps of: mounting an electronic component on an insulating layer so that a part of the electronic component is exposed on the insulating layer by pressing the electronic component onto the insulating layer; fixing the electronic component by curing the insulating layer; forming a metallic seed layer on a top surface of the insulating layer including an exposed surface of the electronic component; forming a plating layer on the metallic seed layer; forming via-holes at positions on the insulating layer, which correspond to pads of the electronic component and forming circuit patterns electrically conducted with the pads; and forming a solder resist layer having the via-holes electrically connected to the circuit patterns. 
     After the step of forming the solder resist layer, the method of manufacturing the electronic component embedded printed circuit board further includes the step of forming solder balls in portions where the via-holes electrically connected to the circuit patterns. 
     In the step of mounting the electronic component on the insulating layer, when any one of the electronic component and the insulating layer is selectively heated, a metallic tape or foil may be attached onto a bottom surface of the insulating layer on which the electronic component is mounted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a cross-sectional view of an electronic component embedded printed circuit board in accordance with an embodiment of the present invention; 
         FIGS. 2 to 8  are cross-sectional views illustrating a manufacturing process of an electronic component embedded printed circuit board in accordance with the present invention; and 
         FIGS. 9 to 13  are cross-sectional views illustrating a manufacturing process of an electronic component embedded printed circuit board in accordance with another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     Electronic Component Embedded Printed Circuit Board 
     First,  FIG. 1  is a cross-sectional view of an electronic component embedded printed circuit board in accordance with an embodiment of the present invention. As shown in the figure, an electronic component embedded printed circuit board  100  includes an insulating layer  110 , an electronic component  120  of which a part is buried in the insulating layer  110 , a plating layer  140  formed on the insulating layer  110 , circuit patterns  114 , and a solder resist layer  150  insulated from the circuit pattern  114 . 
     The insulating layer  110  may be made of a thermoplastic resin, a thermosetting resin, a UV curing resin, or a mixed resin of the resins. The part of the electronic component  120  is buried to project on the insulating layer  110 . 
     Pads  121  formed on a bottom surface of the electronic component  120  buried in the insulating layer  110  are electrically connected to the circuit patterns  114  through via-holes  113  formed on the insulating layer  110 . A part exposed on the insulating layer is surrounded by a metallic seed layer  130  being in close contact with the metallic plating layer  140 . 
     At this time, the metallic seed layer  130  is formed on an entire top surface of the insulating layer  110  including a surface of the electronic component  120  exposed to the insulating layer  110 . 
     The metallic plating layer  140  is formed on the metallic seed layer  130 . The metallic seed layer  130  and the plating layer  140  which are in contact with the exposed surface of the electronic component  120  allow heat generated from the electronic component  120  to be easily emitted to an outside through the metallic seed layer  130  and the plating layer  140 . 
     More specifically, in case of the electronic component  120  of which the part is buried in the insulating layer  110 , A part of the electronic component  120  excluding the buried part is fixed to project on a top surface of the insulating layer  110 , whereby a top surface and a part of a side surface of the electronic component  120 , which are parts projecting on the insulating layer  110  are surrounded by the metallic seed layer  130  and the plating layer  140 . 
     That is, the electronic component  120  is buried on an interface between the insulating layer  110  and the plating layer  140 , a contact area of the electronic component  120  with the metallic plating layer  140  may be maximized and discharge efficiency may be maximized when the heat generated from the electronic component  120  is discharged through a contact portion of the metallic seed layer  130  and the plating layer  140  to an outside in contrast to a conventional printed circuit board in which the electronic component is completely buried in the insulating layer. 
     The electronic component  120  is joined to the insulating layer so that an upper part of the electronic component  120  is exposed by pressing an absorbing device (not shown) in provisional curing of the insulating layer  110 . Any one component between the insulating layer  110  and the electronic component  120  is selected and heated at a predetermined temperature, that is, a temperature to provide fluidity suitable for joining of the electronic component  120  to the insulating layer  110  by pressing in order to maintain the insulating layer  110  in the provisional curing state. 
     At this time, a metallic tape or foil  111  (see  FIGS. 2 to 7 ) may be attached onto a bottom surface of the insulating layer  110  in order to maintain the insulating layer&#39;s own form when the insulating layer  110  has the fluidity by being heated. The circuit pattern  114  connected to the via-holes  113  may be configured by etching at the time of forming a circuit after forming the plating layer  140  for discharging the heat of the electronic component  120 . 
     Meanwhile, when the electronic component  120  is pressed onto the insulating layer  110  at a predetermined pressure through an additional absorbing device, a pit  112  may be formed on the insulating layer  110  in the periphery of the electronic component  120  by pressing force of the electronic component  120 . 
     The pit  112  formed on the insulating layer  110  may be formed at the time of adjusting heating temperature for adjusting the fluidity of the insulating layer  110  or at the time of pressing the electronic component  120  by regulating viscosity in resin selection. 
     When the electronic component  120  is joined to the insulating layer  110 , a reason why the pit is formed in the periphery of the electronic component  120  is to improve a heat radiation characteristic of the electronic component  120  by increasing a contact area between the electronic component  120  and the metallic seed layer  130  at most by enabling the metallic seed layer  130  to grow even in an inside of the pit  112  at the time of forming the metallic layer  130  on the surface of the electronic component  120 . 
     As described above, in the printed circuit board  100  having the above-described technical configuration, the insulating layer  110  may adopt various types of insulating resins, for example, a thermosetting resin, a thermoplastic resin, a UV (UltraViolet) curing resin, and the like such as LCP, ABF, PR, PSR, liquid PI, and the like. Among them, in case that the insulating layer  110  is made of the thermoplastic resin, the electronic component  120  may be reutilized. 
     That is, when the printed circuit board  100  is manufactured through a post process after mounting the electronic component  120  so that the part of the electronic component  120  is exposed on the insulating layer  110  and curing the insulating layer  110 , the electronic component  120  is separated from the insulating layer  110  and may be reutilized by reheating the insulating layer  110  made of the thermoplastic resin in case that the post process has a defect. 
     Accordingly, in case that the insulating layer  110  is made of the thermoplastic resin, the electronic component  120  may be reutilized, thereby the electronic component embedded printed circuit board with the expensive electronic component  120 . 
     Meanwhile, the plating layer  140  for radiating the heat generated in the electronic component  120  to the outside in contact with the insulating layer  110  may be substituted by a conductive paste. That is, the plating layer  140  serves to radiate the heated generated in the electronic component  120  by heat conductive performance. Therefore, the conductive paste is plated directly on the insulating layer  110  serving to radiate the heat and an exposed surface of the electronic component  120  exposed on an upper part of the insulating layer  110 , and is cured, thereby configuring a conductive paste layer for heat radiation. 
     It is preferable that the conductive paste is configured by mixing a paste with comparatively excellent heat conductive efficiency and an adhesive. For example, it is preferable that the conductive paste is composed of a silver (Ag) paste or a copper (Cu) paste. 
     After this, the solder resist layer  150  with via-holes  151  is formed on one surface of the insulating layer  110  having the circuit patterns  114  formed thereon through a general multilayer printed circuit board manufacturing method. Solder balls  160  are individually in the via-holes  151 . 
     Method of manufacturing Electronic Component Embedded Printed Circuit Board According to First Embodiment 
       FIGS. 2 to 8  are cross-sectional views illustrating a manufacturing process of an electronic component embedded printed circuit board in accordance with a first embodiment of the present invention. 
     As shown in the figures, in the method of manufacturing the electronic component embedded printed circuit board in accordance with the embodiment of the present invention, first, an electronic component  120  having a plurality of pads  121  formed on a bottom surface thereof is mounted on an upper part of an insulating layer  110  made of a resin by face-down pressing. 
     The insulating layer  110  may be made of a thermoplastic resin, a thermosetting resin, a UV curing resin, or a mixed resin of them. Heating any one of the insulating layer  110  and the electronic component  120  at predetermined temperature grants fluidity to the insulating layer  110  at the time of pressing the electronic component  120  onto the insulating layer  110 . 
     At this time, a metallic tape or foil  111  may be attached onto a bottom surface of the insulating layer  110  in order to maintain the insulating layer&#39;s own form when the insulating layer  110  is granted the movablility. 
     The electronic component  120  inserted into the insulating layer  110  is pressed onto an upper part of the insulating layer  110  with a top surface of the electronic component  120  absorbed by a vacuum pressing member  200 . Accordingly, the electronic component  120  is mounted on the insulating layer  110  with only a part of the electronic component  120  buried in the insulating layer  110  by using the only fluidity without an additional cavity by adjusting pressing force of the pressing member  200 . 
     In addition, when the electronic component  120  is mounted on the insulating layer  110  with a part of a lower part of the electronic component  120  buried in the insulating layer  110 , a pit  112  is formed on the insulating layer  110  in the periphery of the electronic component  120 . 
     It is preferable that the insulating layer  110  is made of a resin which can show a viscosity characteristic enough to create the pit  112  at the time of selecting the resin configuring the insulating layer  110 . 
     Next, the electronic component  120  is fixed with the part of the electronic component  120  exposed on the insulating layer  110  by curing the insulating layer  110  mounted with the electronic component  120 . At this time, a curing process may depend on a type of the resin configuring the insulating layer  110 . In case of the thermoplastic resin, the insulating layer  110  is cured by natural cooling at room temperature while in case of the thermosetting resin or the UV resin, the insulating layer  110  is completed cured by irradiating UV. 
     Herein, in case that the insulating layer  110  is made of the thermoplastic resin, the insulating layer  110  is also granted the fluidity by reheating the insulating layer  110  when a fixation position of the electronic component  120  is distorted or a process error occurs after the insulating layer  110  is cured. Accordingly, the electronic component  120  can be reutilized by separating the electronic component  120  from the insulating layer  110 . 
     Next, a metallic seed layer  130  is formed on a top surface of the insulating layer  110  and an exposed surface of the electronic component  120  projecting on the insulating layer  110 . 
     It is preferable that the metallic seed layer  130  is formed in a thin metal film by a process such as sputtering, electroless plating, or the like. The metallic layer  130  is collectively formed even on an inner surface of the pit  112  formed on the insulating layer  110  in the periphery of the electronic component  120 . 
     As described above, a reason why the pit  112  is formed in the insulating layer  110  and the metallic seed layer  130  is formed on up to a side surface of the electronic component  120  within the pit  112  including the inner surface of the pit  112  is to maximize a radiation characteristic by increasing a contact area of the metallic seed layer  130  being in contact with the side surface as well as the exposed top surface of the electronic component  120 . 
     After this, a plating layer  140  is formed on the metallic seed layer  130 . 
     The plating layer  140  is formed on the metallic seed layer  130  in a predetermined thickness by electrolytic plating. 
     It is preferable that the plating layer  140  is made of a metallic material having high heat conductive efficiency. The plating layer  140  is made mainly of Ag or Cu, whereby heat generated in the electronic component  120  is transmitted to the plating layer  140  through the metallic seed layer  130  and is emitted to an outside. 
     The plating layer  140  serves to improve emission efficiency of the heat of the electronic component  120  by bringing the plating layer  140  and the surface of the electronic component  120  into direct contact with each other via the metallic seed layer  130 . 
     Next, via-holes  113  are formed at positions on the insulating layer  110  corresponding to pads  121  of the electronic component  120  and circuit patterns  114  electrically conducted with the pads  121  are formed on the insulating layer  110 . 
     After a solder resist layer  150  is formed on one surface of the insulating layer  110  on which the circuit patterns  114  are formed by applying a general multilayer printed circuit board manufacturing method and the via-holes  151  electrically conducted with the circuit patterns  114  are formed on the solder resist layer  150 , solder balls  160  for mounting a substrate are individually formed in portions where the via-holes  151  are formed, whereby an electronic component embedded printed circuit board  100  is manufactured. 
     Method of Manufacturing Electronic Component Embedded Printed Circuit Board According to Second Embodiment 
     Hereinafter,  FIGS. 9 to 13  are cross-sectional views illustrating a manufacturing process of an electronic component embedded printed circuit board in accordance with another embodiment of the present invention. 
     In detailed description of the electronic component embedded printed circuit board in accordance with this embodiment of the present invention, duplicated description is suppressed with respect to the same manufacturing process and constituent members as the first embodiment as possible, and like reference numerals refer to like elements throughout. 
     As shown in the figures, in an electronic component embedded printed circuit board  100  in accordance with the embodiment of the present invention, first, an electronic component  120  having a plurality of pads  121  formed on a bottom surface thereof is mounted on an upper part of an insulating layer  110  with an upper part of the electronic component  120  projecting on the insulating layer  110  by using a vacuum pressing member  200 . 
     At this time, a metallic tape or foil  111  may be attached onto a bottom surface of the insulating layer  110  in order to maintain the insulating layer&#39;s own form when the insulating layer  110  is granted movablility. 
     Next, the electronic component  120  is fixed with a part of the electronic component  120  exposed on the insulating layer  110  by curing the insulating layer  110  mounted with the electronic component  120 . 
     Herein, in case that the insulating layer  110  is made of a thermoplastic resin, the insulating layer  110  is also granted the fluidity by reheating the insulating layer  110  when a fixation position of the electronic component  120  is distorted or a process error occurs after the insulating layer  110  is cured. Accordingly, the electronic component  120  can be reutilized by separating the electronic component  120  from the insulating layer  110 . 
     Next, after a conductive paste layer  170  is formed on the insulating layer  110  and an exposed surface of the electronic component  120  projecting on the insulating layer  110 , the conductive paste layer  170  is cured. 
     The conductive paste layer  170  is composed of a silver (Ag) paste or a copper (Cu) paste which is a paste having high heat conductive efficiency, whereby heat generated in the electronic component  120  is transmitted to the conductive paste layer  170  and is emitted to an outside. 
     The conductive paste layer  170  may easily be formed by a squeeze method or a screen printing method. Bringing the insulating layer  110  and the surface of the electronic component  120  into direct contact with each other improves emission efficiency of the heat of the electronic component  120 . 
     When the conductive paste layer  170  is collectively formed on the insulating layer  110  and the surface of the electronic component  120 , the conductive paste layer  170  may be formed by a simple process and at low cost in comparison with a process of forming the plating layer  140  of the first embodiment, thereby saving whole manufacturing cost of the printed circuit board. 
     Next, at positions on the insulating layer  110 , which correspond to pads  121  of the electronic component  120 , via-holes  113  are formed and then circuit patterns  114  electrically conducted with the pads  121  are formed. 
     After a solder resist layer  150  is formed on one surface of the insulating layer  110  on which the circuit patterns  114  are formed by applying a general multilayer printed circuit board manufacturing method and the via-holes  151  electrically conducted with the circuit patterns  114  are formed on the solder resist layer  150 , solder balls  160  for mounting a substrate are individually formed in portions where the via-holes  151  are formed, whereby an electronic component embedded printed circuit board  100  is manufactured. 
     As described above, in a chip embedded printed circuit board in accordance with the present invention, as the metallic seed layer and a metallic plating layer covers an entire exposed surface of an electronic component mounted on an insulating layer, there are advantages in that a radiation characteristic of the electronic component can be maximized and a thickness of the printed circuit board can be maximized. 
     In the present invention, in case that the insulating layer is made of a thermoplastic resin, the electronic component may be reutilized when a process error occurs, thereby saving product cost. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.