Patent Publication Number: US-2015061103-A1

Title: Embedded die package

Description:
BACKGROUND 
     An embedded die package has an integrated circuit die embedded in a laminate block with a construction similar to the laminate structure of a printed circuit board. Embedded die packages are often produced in a ball grid array (BGA) format with the BGA positioned at the bottom of the package. Passive components may be connected to the IC die. Such passive components may be positioned on the top of the laminate block or may be embedded in the laminate block. Circuit layers within the laminate block are connected to filled or plated through-holes extending through the laminate block. 
     Embedded die packages have been produced by a number or companies for several years. One such embedded die package is produced by Texas Instruments Inc., which uses the term “microsystem package” and the trademark “MicroSIP™”in referring to this product. Embedded die packages are described in detail in “Design Summary for MicroSiP™-enabled TPS8267xSiP”, Texas Instruments 1Q 2011 MicroSiP™ Design Summary SLIB006 published 2011, available at www.ti.com, and in “Texas Instruments” Embedded Die Package” by Romain Fraux from Systems Plus Consulting, May 2012, Issue N 23 of 3D Packaging, which are both hereby incorporated by reference for all that is disclosed therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a conventional embedded die package. 
         FIG. 2  is a schematic cross sectional perspective view of the embedded die package of  FIG. 1 . 
         FIG. 3  is a top plan view of an example embodiment of an embedded die package. 
         FIG. 4  is a schematic cross sectional perspective view of the embedded die package embodiment of  FIG. 3 . 
         FIG. 5  is a top front perspective view of the embedded die package of  FIGS. 1 and 2  mounted on a printed circuit board. 
         FIG. 6  is a schematic cross sectional view illustrating the singulation of a substrate having embedded dies therein into a plurality of embedded die packages such as illustrated in  FIGS. 2 and 3 . 
         FIG. 7  is a schematic perspective view of the substrate of  FIG. 6 . 
         FIG. 8  is a top plan view of a portion of an embedded die substrate with filled through-holes, after singulation thereof. 
         FIG. 9  is a top plan view of an embedded die substrate with plated through-holes, after singulation thereof. 
         FIG. 10  is a schematic, bottom perspective view of an example embedded die package having a plurality of filled sectioned through-holes. 
         FIG. 11  is a flow chart illustrating a method of making an electrical assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a top plan view of a conventional embedded die package  10 . The package  10  comprises a rectangular box shaped laminate block  11 . The laminate block  11  has a top face  12 , bottom face  14 ,  FIG. 2 , and a plurality of lateral side faces  16 ,  18 ,  20 , and  22 . An IC die  30  is embedded in the laminate block  11 . In this particular embodiment the die  30  is part of a sensor assembly and must have access to the external environment. Thus, the die  30  is positioned within a cavity  31  extending from the top face  12  of the laminate block  11 . In another embodiment, in which access to the die  30  from the external environment is not a requirement, no cavity  31  is provided. The IC die  30 , as best shown in  FIG. 2 , comprises a means for electrically connecting the die  30  to an underlying circuit board  200 ,  FIG. 5 . One such means may be a ball grid array  32  having a plurality of solder balls  34  (only one shown). The underlying circuit board  200 ,  FIG. 5 , has an array of surface contacts (not shown) adapted to be bonded to the balls  34  of the ball grid array  32 . The die  30  may also have a plurality of other electrical contacts  37  that may be positioned on a top surface of the die  30 . 
     The laminate block  11  has a plurality of cylindrical through-holes  40  with vertical axes Z 0 Z 0 . The cylindrical through-holes  40  extend between the top face  12  and bottom face  14  of the laminate block  11 . Each through-hole  40 , as illustrated in  FIG. 2 , may be a “filled through-hole” that is filled with conductive material  44 , such as copper. The through-holes  40 , rather than being filled through-holes, may be “plated through-holes” that have a conductive plating layer applied to the cylindrical side wall of the through-hole  40 . The through-holes  40  are set back from an adjacent side face  22  of the laminate block  11 . The setback distance “a” must be sufficiently large to prevent cracking of the laminated block  11  in the area between the through-hole  40  and the side face  22 . The magnitude of the setback distance “a” directly affects the area of the embedded die package footprint. 
     The laminate block  11  comprises a plurality of laterally extending circuit layers such as an intermediate circuit layer  54 ,  FIG. 2 , which may electrically connect electrical contacts  37  on the integrated circuit die  30  to the conductive filling  44  of the various through-holes  40 . One typical circuit configuration  25 , which could be provided on a top face of the laminate block  11  or on an intermediate circuit layer of the laminate block  11 , is illustrated in  FIG. 1 . 
       FIG. 3  is a top plan view of an embedded die package  110 , according to one example embodiment. The embedded die package  110  comprises a box shaped (regular parallelepiped shaped) laminate block  111  having a plurality of sectioned through-holes  140  positioned about the periphery thereof.  FIG. 4  is a schematic cross sectional view of a portion of the embedded die package  110  of  FIG. 3 . An IC die  130  is embedded in the laminate block  111 . The method by which the IC die  130  is embedded in the laminate block  11  may be a conventional method known in the art. The method by which the laminate block  11  is formed may also be a conventional method known in the art. 
     Unlike the prior art, through-holes  140  are “sectioned through-holes” that have the shape of an axially sectioned/sliced cylinder, i.e., a cylinder sectioned by a cutting plane that extends substantially parallel to its central axis. In some embodiments the sectioned through-holes  140  have a substantially semicircular cross section. The center of curvature of the sectioned through-holes  140  may be positioned in substantial alignment with the adjacent side wall of the block  111 , e.g., sidewall  122 . The sectioned through-hole  140  may have a plating layer  142  provided on the arcuate surface of the block  111  that defines the sectioned through-hole  140 . In addition to sectioned through-holes  140 , the block  111  may have a plurality of conventional filled or plated through-holes  144 ,  FIG. 3 , (not shown in  FIG. 4 ) positioned inwardly of the periphery of block  111 . Some of these conventional through-holes  144  may be connected to one or more of the sectioned through-holes  140  by patterned circuits  143 . 
     The IC die  130  has structure for electrically connecting the die  130  to corresponding contact surfaces  230  of a printed circuit board  200 , of which only a broken away portion is shown in  FIG. 4 . In one embodiment, the electrical connection structure may comprise a ball grid array (BGA)  132  having a plurality of solder balls  134  (only one shown). Ball grid arrays and connection thereof to circuit boards are known in the art. The integrated circuit die  130  may also include a plurality of contact surfaces  135 ,  137  that are connected as by intermediate laminate layer circuitry  154  to conductive material such as plating  142  provided in the sectioned through-holes  140 . Since there is no laminate material positioned outwardly of the sectioned through-hole  140 , the problem of laminate breaking and pealing is obviated by this construction. Also, the size of the embedded die package  110  produced by this method may be made smaller than that of a conventional embedded die package having the same sized die. 
       FIG. 5  is a perspective view of an embedded die package  110  with sectioned through-holes  140  mounted on a printed circuit board  200 . The printed circuit board  200  has a plurality of contact surfaces  210  provided on a top face  202  of the circuit board  200 . The contact surfaces  210  are arranged around the periphery of the embedded die package  110 . The circuit board contact surfaces  210  are electrically connected to the exposed conductive material in the sectioned through-holes  140  (e.g., copper or silver plating or filling). The electrical connection may be provided by conventional solder bonds  220  or other connection material. The large exposed surface of the conductive material, both at the top and sidewall of the laminate block  111  provides better solder wetting than the prior art structure and improves the quality of the solder bond and the reliability of the resulting circuit board/embedded die package assembly  200 / 110 . The ball grid array or other bottom contact surfaces  132  of the die  130  are connected to oppositely positioned contact surfaces  230  on the circuit board  200 , as shown in  FIG. 4 . Such connections are conventional and known in the art. The circuit board  200  may be a conventional printed circuit board or wiring board or interposer or other electrical connection board. 
     The manner by which an embedded die package  110  with sectioned through-holes  140  is produced will now be described with reference to  FIGS. 6-9 . Initially cylindrical through-holes  324  are bored through the substrate  300  at predetermined locations associated with edge portions of laminated blocks  310 ,  312  that are to be formed from the substrate  300 . The hole boring may be done with conventional drills in a conventional manner known in the art. After boring the cylindrical through-holes  324 , the through-holes  324  may be filled with conductive material such as copper or the like in a conventional manner known in the art. Alternatively, the through-holes  324  may be plated with conductive material, as is also known in the art. The embodiment illustrated in  FIG. 8  illustrates an embodiment in which the through-hole  324  has been filled with conductive material  344 .  FIG. 9  illustrates an embodiment in which the conductive material is a plating layer  346 . Two sectioned through-holes  342 ,  FIGS. 8 and 9 , are produced in adjacent laminate blocks, e.g.,  310 ,  312  from the cylindrical through-hole  324  as a result of singulation. 
     As illustrated by  FIGS. 6 and 7 , the laminated substrate  300  is constructed in a grid pattern of integrally formed rectangular block portions, e.g.,  310 ,  312 ,  314 ,  316 , etc. The rectangular block portions are substantially identical. Each block portion comprises a plurality of circuit layers, such as  154 , and has an IC die, such as die  130 , embedded therein. The grid pattern defines a plurality of saw streets  304 ,  FIG. 7 . Cylindrical through-holes  324  are positioned in alignment along each saw street  304 . 
     Next, the substrate  300  is provided with a backing of conventional saw tape  326 ,  FIG. 6 , and is moved to a conventional sawing station. At the sawing station a plurality of saw cuts are made along the saw streets  304 . The saw streets  304  each intersect a plurality of aligned through-holes  324 . The through-holes prior to singulation are represented in dashed and solid lines in  FIGS. 8 and 9 .  FIGS. 8 and 9  are top plan views of adjacent embedded die packages  310 A,  312 A formed from the substrate  300 . The saw singulation produces a plurality of substantially identical embedded die packages  310 A,  312 A, etc. that correspond to substrate  300  portions  310 ,  312 , etc. In other embodiments, rather than saw singulation, the various substrate portions  310 ,  312 , etc., may be singulated by laser singulation or by die stamping or by any other singulation method now known or later developed. 
       FIG. 10  is a bottom perspective view of an embedded die package  510  having a top face  552 , a bottom face  554 , and a plurality of side faces  556 ,  558 ,  560 ,  562 . The package  510  has a plurality of filled sectioned through-holes  570 . Alternatively, the filled sectioned through-holes  570  may be replaced by plated sectioned through-holes such as illustrated in  FIG. 9 . An embedded die  530  in this embodiment has a bottom surface portion configured as a ball grid array  580 , which is adapted to be mounted to corresponding contact surfaces (not shown) on a top face of a printed circuit board such as board  210  illustrated in  FIG. 5 . 
       FIG. 11  is a flow chart of a method of making an electrical assembly. The method may comprise, as illustrated at  602 , making a laminate substrate, and, as illustrated at  604 , embedding a plurality of integrated circuit dies in the laminate substrate. The method may further include, as shown at  606 , forming a plurality of through-holes in the laminate substrate and adding conductive material to the through-holes. The method may also include, as shown at  608 , making at least one saw cut extending through the laminate substrate and through the plurality of through-holes and the conductive material therein to form at least one laminate block with a cut face and a plurality of sectioned through-holes. 
     Various embodiments of an embedded die package and of a method of making an embedded die package have been described in detail herein. Various alternative embodiments that are not expressly described herein will occur to those skilled in the art after reading this disclosure. It is intended that the appended claims be broadly construed so as to cover such alternative embodiments, except as limited by the prior art.