Abstract:
Disclosed are IC package structures having stair stepped layers and which have no plated vias. Such structures can be fabricated either as discrete packages or as strips such as might be beneficial in for use with memory devices wherein critical or high speed signals can be routed along the length of the multi-chip strip package without having to have the signals ascend and descend from the interconnection substrate on which the assembly is mounted to the IC package termination and back as the signal transmits between devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This filing claims priority as a continuation in part of U.S. patent application Ser. No. 10/987,187 by Joseph C. Fjelstad, et al., filed Nov. 12, 2004 now U.S. Pat. No. 7,388,279, and entitled “Tapered Dielectric and Conductor Structures and Applications Thereof,” which claims priority from U.S. Provisional Application 60/519,945 filed Nov. 17, 2003 and entitled “Memory Package and Structures Created Therefrom,” both of which are herein incorporated by reference. This filing also claims priority from U.S. Provisional Application 60/676,863 by Joseph C. Fjelstad, filed May 2, 2005, and entitled “Memory Packages Having Stair Step Interconnection Layers,” which is also incorporated by reference herein. This application also incorporates by reference U.S. application Ser. No. 10/947,686 filed Sep. 9, 2004 by Joseph C. Fjelstad, and Entitled Multi-Surface IC Packaging Structures and Methods for Their Manufacture, and U.S. application Ser. No. 10/964,578 Filed Oct. 12, 2004 by Joseph C. Fjelstad, et al., and entitled Multi-Surface Contact IC Packaging Structures and Assemblies. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of high speed electronic interconnections for memory and the packaging of semiconductor integrated circuits for use therewith. 
     BACKGROUND 
     Memory integrated circuits “ICs” for use with most computers operate at speeds slower than current generation central processing unit “CPU” ICs creating a condition generally referred to as the “memory bottleneck”. In such condition, the CPU must remain in a wait state until the memory data is written or retrieved. The problem has been addressed, in part, by improved memory system designs. However as electronic systems move into the multi-gigabit per second data rate range, a significant gap remains between top-end operating rates of CPU ICs and memory ICs. Part of this ongoing disparity is due to the limits of current interconnection design, which often results, particularly at higher frequencies, in disturbances that contribute to signal distortion. For example, signal distortion can often be due, at least in part to so-called parasitic effects resulting from traditional interconnect designs. Because signal speed and signal integrity are two primary goals in digital signal transmission, interconnect designs that assure signal integrity during data transmission are key. Controlling signal integrity begins with the design of the circuit. Choices made in terms of circuit layout, and the materials used and the general architecture of the complete assembly, will all have impact of the quality if the signal transmission and its ultimate integrity. 
     Because parasitic effects and signal discontinuity are primary sources of signal disturbance, one of the major objectives in maintaining signal integrity is to eliminate or minimize the parasitic effects and electrical discontinuities impinging upon a signal. Parasitic effects and electrical discontinuities are caused by a number of factors such as sharp changes in direction, changes in material, circuit feature flaws and even interconnections, such as solder balls used to connect IC packages to next level interconnection substrates. All these can affect signal integrity by introducing undesirable changes in impedance and creating signal reflections. There is also concern about signal skew, cause by differing signal lengths, which is important in assuring proper signal timing. 
     The first place in an electronic system such parasitic effects are encountered, beyond those encountered within the IC structure itself, is the IC package which is used to connect the IC die to a next level interconnection system. While current generation IC packages are presently reasonably well suited to meeting current needs, as the electronics industry moving to ever higher data signaling rates, the formerly minor concerns associated with packages and interconnection paths have now reached a level of critical importance. 
     The net effect of this complex web of interactive elements is that they collectively combine to make it extremely difficult to predict and design for reliable high performance at higher processing speeds. Additionally, at higher processing speeds, parasitic effects and signal discontinuities and reflections can contribute to the thermal demands placed on a system. Thus, as memory circuit speeds climb, there is need for new approaches to design of memory package interconnections to overcome the looming and highly complex electrical and thermal problems associated with traditional approaches to IC memory packaging. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is best illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which 
         FIG. 1  shows an example of prior art; 
         FIG. 2  shows an example of prior art; 
         FIG. 3  shows an example of prior art; 
         FIG. 4  shows an example of prior art; 
         FIG. 5  shows an embodiment of a memory chip package assembly having a stair stepped interconnection layer; 
         FIG. 6  shows an exploded perspective view of an embodiment of a multi-chip memory package assembly having a stair stepped interconnection layer; 
         FIG. 7  show an embodiment of a multi-chip memory package assembly in assembled form with a plurality of discrete base materials having conductor patterns with I/O contacts which are each bonded to a common and shared base conductor pattern having its own separate I/O contacts; 
         FIG. 8  show an embodiment of a multi-chip memory package assembly in assembled form with a continuous base material and having disposed on it a plurality of conductor patterns bonded to (or built up additively in a sequential process) a base conductor pattern and having I/O contacts having a joining material attached; 
         FIG. 9  shows an embodiment of memory module with multi-chip memory packages assembled to the surface of the memory module; 
         FIG. 10  shows an IC die with center bond pads and having selected I/O terminations redistributed to second locations to provide secondary terminations; 
         FIG. 11  shows a perspective view of and embodiment of a portion of a strip package with an enlarged area to provide greater detail; 
         FIGS. 12  A and B disclose assembled. enlarged, and exploded views of an embodiment of a strip package having bridge circuits which cross the bonding apertures to create a multi drop connection path; and 
         FIG. 13  A-D show in cross section, partial views of various IC package strips embodiments having different interconnection pathways constructions to meet alternative interconnection path requirements. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein using descriptions and figures are IC package structures having stair step connections for use with memory devices and which improve control of the quality of an electronic signal that passes though a memory chip package and between memory chips. Moreover, the nature of the memory package assembly disclosed offers a structure better suited to thermal management than current package designs. 
     The embodiments disclosed herein address the limitations of current design and manufacturing practices employed in the fabrication of electronic memory device and system interconnections and the present inability of those design and manufacturing practices to address fully and adequately the needs for improved electronic signal integrity as the electronic signal transitions between memory chips on an electronic memory module. 
     An objective of the present disclosure to describe memory package structures which provide direct and uniform controlled impedance across the surface of a memory package by routing high speed signals on a controlled impedance first layer. 
     Another objective is to describe a first layer having one or more signal paths which provides a substantially skew free address line for clocking signals on the package while routing other signals, such as power and ground, on a second stair stepped layer wherein both metal layers are interconnected to the IC memory die. 
     It is yet another objective of the present disclosure to describe memory package structures which reduce the number of I/O required on the package due to the package structure&#39;s ability to transmit data directly between chips within the package. 
     It is yet another objective of the present disclosure to describe memory package structures which provide for improved thermal dissipation. 
     The present embodiments offer novel alternative approaches to addressing and meeting the stated objectives thus solving certain problems associated with current design approaches. Throughout this disclosure, many specific details are recited which are not essential to make or use the embodiments described herein. Accordingly, these details are offered for purposes of clarity and enablement, and are not intended to limit the spirit and scope of the embodiments described herein, which includes variations and equivalent structures and processes. For example, the IC die (IC chip) is shown in the attached drawings as having two central rows of bond pads. The depiction of this detail is not intended to limit the scope or application of IC chips described herein. Alternative embodiments such as those comprising a single row of bond pads, or more than two rows of bond pads are fully intended as falling within the scope of the embodiments described herein. The advantages are best illustrated with figures as show herewith, wherein: 
       FIG. 1  depicts an embodiment previously disclosed in U.S. patent application Ser. No. 10/964,578 (Publication 20050093152). A single chip IC package structure having stair stepped electrical interconnections on more than one level and interconnected by means of wires. 
       FIG. 2  depicts an embodiment of a previously disclosed IC package structure for interconnecting stacked memory packages having electrical interconnections on two surfaces and interconnected to a common IC contact by means of wires, which each connect to a different level and eliminating electrical stubs. 
       FIG. 3  depicts an embodiment disclosed in U.S. Pat. No. 7,014,472. A memory module has high speed interconnections traversing the module assembly and disposed for interconnections at the distal ends of the assembly. Traditional interconnection(s) are displayed on the bottom of the memory module for interconnection to a connector such as a PC board mounted DIMM connector. 
       FIG. 4  depicts an embodiment disclosed in U.S. patent application Ser. No. 10/987,187 in the form of a multi chip memory IC package structure in strip form wherein all of the interconnections are disposed on a common monolithic interconnection substrate in a single metal layer. 
       FIG. 5  discloses a perspective view of a stair step memory IC package assembly  500  comprising a first dielectric material layer  502  disposed on top of an IC die  501 . A first set of conductors and their respective terminations  504   a  are arranged along the exposed surface of the first dielectric layer  502 . A second dielectric material layer  503  is disposed on top of the first dielectric layer. A second set of conductors and their respective terminations  504   b  are arranged along the exposed surface of the second dielectric layer. The conductors  504   a  and  504   b  include a narrow end  504   c  for connection to the IC die by means of interconnecting bond wires  506 , and a flat circular region  504   d  for electrically engaging contact members (not shown) of a next level interconnection substrate (not shown). The first elongated aperture  505   a  is formed in dielectric material layer  502 , and a second elongated aperture  505   b  is formed in dielectric layer  503 . The two apertures  505   a ,  505   b  are aligned above each other to form a center access area providing egress for the bond wires  506  that electrically couple the conductors  504   a ,  504   b  to their respective termination contacts  507  in the IC die  501 . The outer periphery of the second (upper) aperture  505   b  is slightly larger than the outer periphery of the first (lower) aperture  505   a . The enlarged outer periphery of aperture in  505   b  serves to expose circuit wire bond terminations on  505   a  for wire bonding (or other suitable joining method) which are proximate to the inner edge of the aperture on dielectric material layer  502 . Bond wires  506  are used to interconnect the IC die terminations  507  to the circuit terminations  504   a  and  504   b  on dielectric layers  502  and  503  respectively. While the structure is shown with only two layers of conductors, it is not so limited and more layers may be used if needed or desired. Those familiar with the art of PCB and IC package manufacture will know that an additional protective dielectric insulating layer, such as a solder mask or cover layer or by means of a build up polymer layer, is commonly applied to circuits leaving only the termination I/O exposed. For clarity of description this layer is omitted. 
       FIG. 6  discloses an exploded perspective view of the elements of construction for an embodiment of multi-chip memory IC package assembly, including a plurality of IC die  501  positioned above an assembly support base structure (i.e. carrier)  602  which may be either permanent or temporary. In embodiments wherein the support base structure is temporary, the IC die  501  are removed from the support base  602  at some time after the first dielectric material layer  502  is bonded to the plurality of IC die  501 . In embodiments wherein the support base structure  602  is a permanent part of the circuit, the IC die  501  are advantageously bonded to the carrier base. 
     The support base structure  602  has a plurality of cavities  603  having an appropriate size and shape for receiving respective IC die  501 . According to an alternative embodiment, an individual die may be abutted directly against an adjacent die within a single cavity formed in the support base (carrier) structure  602 , thereby eliminating the need for individual cavities  603  sized to securely receive a respective die. The die terminations  507  are arranged in dual lines along the center of each IC die ( 501 ). The dual-path alignment of die terminations  507  shown in  FIG. 6  is offered only for example, and more or fewer paths are envisioned, as well as alternative shapes and alignments of die terminations, which can include, without limitation, alignments forming circular or elliptical shapes, spirals, star-shapes, and polygons. 
     A first dielectric layer  601  has a plurality of apertures  604  (analogous to  505   a ), each aperture forming an elongated linear shape configured to provide access to the dual line formation of the die terminations  507  formed on an upper surface of a respective die  501 . The apertures, however, may be formed in any shape which will allow for exposure of and access to the die terminations  507 . Conductors  605  disposed on the upper surface of the first dielectric layer include narrow conductive trace portions  606   b  that either terminate at large circular surface region  606   a  (analogus to  504   d  of  FIG. 5 ), or at the edge of a respective aperture  604  formed in the first dielectric layer. Some of the conductors  605  do not have either end terminating at a large circular surface region  606   a , but remain narrow conductive trace portions  606   b  having each end terminating at a different aperture, thereby functioning to connect adjacent IC die that are assembled within a common IC package. The distal ends of each of the narrow conductive trace portions  606   b  are oriented around the outer periphery of a respective aperture  604  in a predetermined arrangement configured to optimize direct connection between a conductor  605  and its respective die termination  507 . Wire bonds are used couple the circuit ends of respective conductive trace portions to wire bond pads on a respective IC die, as illustrated in various figures herein, including  FIGS. 5 ,  11 ,  12 A and  13 A. The large circular portions  606   a  can be used to accept solder balls (not shown) to facilitate interconnection of at least some of the conductors  605  as arranged on the surface of the first (lower) dielectric layer  601  for to a next level electronic element in the completed IC package assembly. It is not essential, however, that every conductor  605  is coupled to a signal source. Embodiments are envisioned wherein some of the conductors are unused. Similarly, it is not essential that every conductor  504   b  of the second dielectric layer (discussed below) be coupled to a signal source. 
     A plurality of second dielectric (insulating base material) layers  503  have elongated apertures  505   b  conforming to a shape and location of the arrays of die terminations  507 . By making the die terminations accessible through the aligned upper and lower apertures  505   b ,  604 , conductive bond wires can be coupled to respective die terminations during fabrication. A second plurality of electrical conductors  504   b  are arranged on the surface of the second dielectric layer in a predetermined arrangement to facilitate direct connection between a conductor  504   b  and its respective die termination  507 . The conductors  504   b  on the plurality of second dielectric layers are also depicted as having a large circular surface region  504   d  and a narrow conductive trace  504   c , as described in  FIG. 5 . The narrow conductive trace portions of these conductor are oriented around the outer periphery of a respective aperture  505   b  in a predetermined arrangement to facilitate direct connection between a conductor  504   b  and its respective die termination  507 . 
     These upper dielectric layers  503  with circuits  504   b  are shown as individual and discrete circuit structures which are bonded to the base circuit layer  601 . According to a first alternative embodiment, a single contiguous dielectric upper layer is disposed atop the lower dialectic layer  601  and secured by appropriate means. According to another alternative embodiment, the upper dielectric layer  503  could be fabricated on the base layer  601  using a build up layer or similar process. Moreover, while the structure of  FIG. 6  is shown with only two conductive layers (i.e., dielectric layers  601 ,  503  having conductors  605 ,  504   b  disposed thereon),  FIG. 6  is offered for illustrative purposes, and is not intended to limit the appended claims, which envision embodiments incorporating any number of conductive layers. By way of example, in another embodiment, the dielectric layer  601  may have a second metal layer on the side opposite the circuits  605 . The second metal layer can function as a voltage source layer, a ground reference layer, or may provide additional circuit traces for select circuit connections other than ground, providing a micro-strip structure or sequence of signal traces that are configured to exhibit a desired impedance value, and/or trace lengths configured to equalize signal path lengths for select signals, thereby reducing or eliminating signal skew for select signals. 
     When the assembly is complete, it may be desirable to remove the support base by a suitable means to reduce the height of the completed assembly at which time an optional thin overmold (not shown) may be applied. 
       FIG. 7  depicts a perspective view of the elements illustrated and defined in  FIG. 6  in an assembled embodiment  700 . The IC die (not visible) or a plurality of IC dies are disposed within the support base structure (carrier)  602 . As discussed in conjunction with  FIG. 6 , the respective die may be disposed in individual cavity members, or abutted against each other in a single cavity. The first (lower) dielectric (i.e. insulator) layer  701  is bonded to the top of the IC memory die  501  (not shown in  FIG. 7 , visible in  FIG. 6 ), to the peripheral edges of the carrier  602 , or to both the die and the carrier. In embodiments wherein the die  501  are not permanently disposed within the carrier  602 , the first (lower) dielectric layer  701  is bonded to the die only, and not to the carrier. A plurality of second (upper) dielectric layers  702  are bonded to or otherwise disposed or built up on the top surface of the first dielectric layer  701 . In all embodiments disclosed herein, circuits of a lower dielectric layer can be coupled to respective IC terminals by bond wire prior to, or subsequent to, the bonding of the next upper dielectric layer(s) to a lower dielectric layer. Spatial limitations and manufacturing processes will inform the fabrication process of the most advantageous order for performing these respective steps. After all bond wires  506  from the various dielectric layers have been connected to their respective IC terminals  507  ( FIG. 5 ), the apertures ( FIG. 5 ) are filled with a suitable encapsulant  703 . I/O terminations such as solder balls  704  are visible around the peripheries of the dielectric layers may be attached to the large circular surface regions ( 504   c  in  FIG. 5 ). 
       FIG. 8  depicts a perspective view of an IC package having a single upper dielectric layer  801  coupled across the top of the lower dielectric layer  701 . A plurality of IC die  501  (visible in  FIG. 6 ) are disposed within carrier  602 . A lower dielectric strip (i.e. interconnection substrate)  701  is disposed above and coupled or attached to the top of the IC memory die, the periphery of the carrier, or both. In embodiments wherein the die  501  are not permanently disposed within the carrier  602 , the first (lower) dielectric layer  701  is bonded to the die only, and not to the carrier. A second (upper) contiguous dielectric strip  801  bonded to the top of the first dielectric strip  701 . The apertures (not visible) of the upper and lower dielectric strips are aligned during fabrication. After the bond wires  506  have been connected to their respective IC terminals  507  ( FIG. 5 ), the apertures are filled with a suitable encapsulant  703 . I/O terminations such as solder balls  704  visible around the peripheries of the dielectric layers may be attached to the large circular surface regions ( 504   d  in  FIG. 5 ). In the embodiment depicted in  FIG. 8 , the second (upper) strip  801  is shown as being a formed from separate piece that is distinct from, and bonded, to the lower dielectric strip. However, alternative embodiments are envisioned wherein the upper dielectric strip is built up on the base circuit strip using build up layer circuit manufacturing techniques. The structure is shown with two circuit layers, each layer having separate conductive circuit pathways on insulating base materials. However, the specific number of dielectric layers shown in  FIG. 8  is intended only as an example, and any number of dielectric layers may be used in conjunction with the embodiments described herein. 
       FIG. 9  depicts a side elevational view of the assembled multi chip memory packages  700  of  FIG. 7  mounted on and interconnected to a memory module  900  such as a DIMM memory card. Centrally located on the module is an advanced memory buffer (AMB) package  901  which accesses and addresses the memory IC packages  700  by way of lateral signal paths  904 , while power, ground and other signals for both the memory and AMB chip are accessed in traditional manner by way of conductors  903  connected to edge card terminations  902  on the memory module. The construction of the memory chip packages can be modified as desired to provide direct access to the AMB. 
       FIG. 10  shows an embodiment of a complementary cross-path IC die  1000  having parallel complementary inner and outer rows of bond pads on the upper surface of a modified IC die. Two parallel inner rows  1001  of bond pads are disposed between two parallel outer rows  1002  of bond pads  1002 . A conductor path  1003  coupled to a bond pad from the left hand row of the inner rows  1001  extends to the right, passing between two bond pads of the right hand row of the inner rows  1001 , and is coupled to a complementary bond pad on the right hand row of the outer rows  1002 . A conductor path  1003  coupled to a respective bond pad from the right hand row of the inner rows  1001  extends to the left, passing between two IC terminals in the left hand row of the inner rows  1001 , and is coupled to a complementary bond pad on the left hand row of the outer rows  1002 . Conductor paths  1003  can be etched, bonded, or otherwise coupled to the surface of the IC die. Referring to  FIGS. 6 and 10 , when IC terminals of adjacent first and second IC die  507  are to be connected by means of narrow signal paths  606   b ,  605  of  FIG. 6 , the complementary cross-path embodiment of  FIG. 10  allows any IC terminal on a first IC die to be connected to any IC terminal on an adjacent IC die. This complementary cross-path structure is therefore useful in IC die utilizing parallel IC terminal arrays. The bond pads  1001 ,  1002  are coupled to the signal paths  606   b ,  605  by a suitable means such as wire bonding. The signal path provided through this embodiment can exhibit a variety of advantageous design characteristics, such as fewer electrical stubs, or a more optimal signal path length, thereby reducing signal reflection, skew, and other deleterious signal phenomena. 
       FIG. 11  provides a perspective view and enlargement of a portion of a strip package embodiment  1100  having conductors  1101  disposed along the package edges to interconnect directly to an adjacent IC die or IC chip in the strip package (not shown). In the enlargement, noncontiguous conductive traces  1101  are electrically coupled by bond wires  1102   a  and  1002   b  to form a contiguous circuit path  1103  suitable for multi drop interconnection to adjoining ICs in the strip package. 
       FIGS. 12A and 12B  respectively show an assembled top plan view and an exploded view of an embodiment of a portion of an IC package structure  1200 . The package assembly includes a first or interior dielectric layer  1201  (the lower dielectric layer in  FIG. 12B ), which is disposed in the interior of the IC package structure between the IC die  501  and the second (upper) dielectric layer  503 . The interior dielectric layer has a left edge  1209 , a right edge  1210 , and a plurality of apertures  1204  arranged in a line along the center portion of the first dielectric layer. Adjacent apertures  1204  are separated by a dielectric bridge  1203 , formed from a continuous portion of the first dielectric layer extending across the center portion of the first dielectric layer. According to the linear arrangement of the apertures  1204  on the interior dielectric layer, for “n” apertures, there are therefore “n−1” dielectric bridges. Conductive paths  1202  extend laterally across the first dielectric layer from the left edge  1209  to the right edge  1210  allowing connection to adjacent ICs on either side (not shown). Electrical continuity from edge to edge is maintained because each of the conductive paths  1202  crosses one of the dielectric bridges  1203 , thereby traversing the center section the first dielectric layer. Multiple separate conductive paths, however, can traverse across a single dielectric path. As discussed in conjunction with the enlarged view, the apertures  1204  between the dielectric bridges allow access to bond pads  507  on the IC die  501  and other connective members during fabrication of the IC package  1200 . 
     A second (upper) dielectric layer  503  is disposed above the interior dielectric layer, and has a single aperture  504   b  extending down the center portion of the layer  530 . As discussed above, the shape and location of apertures on the respective layers is according to the location of the bond pads and circuit connection points on an IC die to which the various dielectric layers are coupled. The size of the apertures is sufficient to grant access to the bond pads and connection points during fabrication, according to the size of the tools used in fabrication. Circuit paths  504   b  are disposed on the upper surface of the upper layer  503 . The circuit paths include rounded planar surface areas  504   d  for interconnection with a next level electronic element, and narrow trace sections  504   c  extending to the periphery of the aperture  504   b  and oriented in predetermined positions for interconnection with respective terminals on the IC die. 
     The enlarged view above  FIG. 12  A provides greater detail of certain structures in  FIGS. 12A  and B. The wire bond termination  1204  on dielectric layer  1201 . The larger aperture  505   b  of dielectric layer  503  is identified by peripheral edges  1207   a    1207   b . The two bond wires  506  in the upper portion of the enlarged view form wire bond connections from select IC die bond pads  507  to respective circuit terminations  504   d  on the upper dielectric layer  503 . The two bond wires  506  in the lower portion of the enlarged view form wire bond connections from select IC die bond pads  507  to conductive circuit terminations  1202   a  on the lower dielectric layer  1201 . The surface of dielectric layer  1201  is seen extending across the aperture from the right peripheral edge  1208 A to the left peripheral edge  1208 B to form a dielectric bridge  1203 , and circuits  1202  disposed on the surface of dielectric layer  1201  are seen on the dielectric bridge  1203 , thereby allowing these circuit paths to traverse the aperture  1204 . 
     Returning briefly to  FIG. 12A , an encapsulant  703  is disposed within the cavity formed by the aligned apertures. It is shown open at the upper end to expose detail for enlargement. According to a preferred fabrication embodiment, the encapsulant  703  is not deposited in the center cavity until the interior dielectric layer  1201  has been bonded to the IC die  501 , the second dielectric layer  503  has been bonded to the interior dielectric layer  1201 , and all required bond wires have been secured to their respective terminals and connection points. 
       FIGS. 13  A- 13 D show in cross section, partial views of various IC die package strip embodiments having different interconnection pathway constructions to meet alternative interconnection path requirements. While the various embodiments are all illustrated with two metal layers (conductive paths disposed on one surface of each of two layered dielectric substrates), this specific number of layers is offered only for example, and embodiments can be utilized with any number of metal layers. For example, an additional conductive layer, disposed either on the top or bottom side of the IC die as oriented in  FIGS. 13A-13D , could be used as a ground layer with transmission paths having a predetermined impedance, or a predetermined path length, and thereby configured to reduce signal reflection, signal skew, or counter other transmission effects that erode signal integrity. 
     In  FIG. 13A , an IC die  1301  is depicted with two circuit layers disposed thereupon. The first layer comprises a first dielectric (insulating) layer  1302  with a bottom surface bonded to the IC die. Conductive paths  1303   a ,  1303   b  are etched, or otherwise disposed upon the top surface of the first layer dielectric layer  1302   a . The second layer comprises a second dielectric layer  1302   b  having a bottom surface affixed to the top surface of the first layer, and conductive paths  1304   a ,  1304   b  formed on the upper surface of the second dielectric layer  1302   b . The cross sectional view discloses IC terminations  1306  disposed on the surface of the IC die  1301  within the apertures a and a′ and more clearly shows the inner edges of the first (lower) dielectric layer  1302  extending horizontally further toward the center of the aperture than the inner edges of the second (upper) dielectric layer  1302   b , thereby creating a tapered or stair-step effect around the cavity formed by apertures a and a′ A wire bond  1305  is used to connect from wire bond terminations  1306  on the IC  1301  to the conductors. Phantom bond wires  1307  are illustrated to represent bond wires connected to other bond pads and other connections on other layers. The assembly is shown with an encapsulant  1308  to protect the wire bonds after assembly. 
     Owing to the limitations of space in  FIGS. 13A-13D , many elements that are known to those skilled in the art have been omitted from these Figures, including, but not limited to, protective insulation on conductive paths  1304   a  and  1304   b , or solder balls or other joining material used to electrically couple the bond wires to specific conductive terminals. The omission of these, and other elements from various Figures described herein has been done to reduce visual clutter and enhance illustrative clarity. Accordingly, the omission of such well known structural elements from select Figures is not intended to limit the scope of the embodiments described herein, or of the appended claims. 
       FIG. 13B  shows in a cross section view substantially the embodiment shown in  FIG. 11  wherein a conductive path  1309  is interconnected to a first termination point (i.e. bond pad)  1307  on the IC chip  1301  and to a second termination point (e.g bond pad)  1310  completing a circuit across the IC die between wire bonds to first layer circuits  1303   a  and  1303   b.    
       FIG. 13C  shows in a cross section view what is substantially the embodiment shown in  FIG. 12 , wherein a conductive circuit pathway  1311  is continuous and bridges and traverses above the chip but is also interconnected to the native chip termination  1307  to provide a multi drop connection path. 
       FIG. 13  D shows in a cross section a view of an embodiment wherein redistribution circuits  1312   a  and  1312   b  are provided on the surface of the IC die  1301  and are interconnected to a first termination point (i.e. bond pad)  1307  on the IC die  1301  disposed beneath the redistribution circuits, and interconnected to circuit paths  1314   a  and  1314   b  above the redistribution circuits by second termination members  1313   a  and  1313   b  representing any suitable connection means, such as any of several flip chip bonding methods. 
     Restating here for emphasis, while the structures illustrated in this disclosure have shown with wire bonds being made to two rows of central bond pads on the IC die, the structures are not so limited and could also be used for created using a single bond pad in the center of the IC die or at the edges of the IC die or combinations thereof. 
     Although the invention has been described briefly with reference to specific exemplary embodiments thereof, it will be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. Moreover, many specific details have been included herein which are not essential to make and use every embodiment of the invention. These details have been included to assist the reader in more easily understanding and comprehending the embodiments described herein. Accordingly, the specification and drawings of this disclosure should be regarded in an illustrative rather than a restrictive sense.