Abstract:
A substrate for packaging semiconductor chips is provided which is structured with conductors having opposite ends terminating in a mounting surface and intermediate portions extending beneath the surface. The ends of the conductors are arranged in repeating patterns longitudinally along the substrate separated by orthogonal strips free of conductor ends to allow for dense surface wiring. The repeating patterns are arranged to allow for chip mounting sites having sufficient spacing to allow for surface wiring. In this way chips in the same and repeat pattern can be connected by personalized surface wiring and preset substrate conductors.

Description:
This application is a continuation of application Ser. No. 285,725, filed July 22, 1981, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to packaging of semiconductor chips, and more particularly, to a chip package wherein the substrate is provided with a repeating pattern of conductor ends, with each pattern defining sites to permit the reception of a variety of different chips. The conductor ends are wired to connect both within the same pattern and with adjacent patterns. This permits the personalization of a common substrate to receive many different combinations of chips. 
     In the evolution of semiconductor technology, packaging of the chips has taken on increasing importance. The number of circuits that can be placed on a chip has dramatically increased as has the number of functions of any given chip. There are chips which are primarily memory, those which are primarily logic, and those which are mixed logic and memory. As miniaturization progresses it is becoming increasingly desirable to place a number of different chips, and different combinations of chips onto a single substrate. This chip/substrate package can be inserted as a unit into various pieces of equipment. 
     However, with prior art technology each module having a different combination of chips had to have a substrate designed specifically for each combination of chips. Indeed, even in a single chip module, each different chip required a different substrate unique to the given chip. Prior art examples of technology for providing a substrate for a given chip or specific combination of chips is represented in U.S. Pat. Nos. 4,202,007 and 4,193,082 which represent one technology for making substrates with buried wiring, and IBM Technical Disclosure Bulletin, Vol. 22, No. 5 dated October 1979, at pages 1841-1842, which represents a different technology. This prior art, however, shows only a technique for forming substrates which will accept predetermined chips or chip combinations. The necessity of designing, producing and stockpiling a different substrate for each chip and each different combination of chips is very expensive and adds significantly to the cost. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a substrate for packaging semiconductor chips is provided having a chip mounting surface. The substrate is structured with conductors having opposite ends terminating at said mounting surface with intermediate portions connecting the ends of the conductors. The ends of the conductors are arranged in repeating patterns longitudinally along the substrate separated by orthogonal strips on the surface which are free of conductor ends to allow for dense surface wiring. The intermediate portions of some conductors connect ends within a pattern and of some conductors connect ends in adjacent patterns. The conductor ends in each pattern are positioned to delineate a plurality of chip mounting sites having sufficient spacing between the conductor ends to permit the positioning of chip mounting means which may be electrically connected to the ends of the conductors by surface metallization. 
     In this way a single substrate can be personalized to accept a plurality of different chips at any given pattern location and to utilize two or more locations to mount chips with appropriate connections between. 
     The substrate of the present invention utilizes subsurface conductors to provide basic interconnection within each pattern and between adjacent patterns and surface wiring for the unique personalized chip mounting and wiring. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a chip package of this invention showing the substrate and chips mounted thereon; 
     FIG. 2 is a sectional view taken substantially along the plane designated by line 2--2 of FIG. 1; 
     FIG. 3 is a sectional view taken substantially along the plane designated by the line 3--3 of FIG. 1; 
     FIG. 4 is a sectional view taken substantially along the plane designated by the line 4--4 of FIG. 1; 
     FIG. 5 is a perspective exploded view of some of the laminae utilized to form the substrate of FIG. 1, and 
     FIGS. 6A and 6B are a plan view of another embodiment of the chip package of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, a substrate having two repeating patterns of surface termination of conductors is shown. It is to be understood that the substrate could be made longer with additional repeating patterns, but two are shown for the purpose of illustration. 
     The substrate, designated by the reference character 10, is formed from a plurality of different laminae, 12a, 12b, 12c, 12d, some of which are shown in FIG. 5. The laminae are thin sheets of green (uncured) ceramic or other dielectric material. Different laminae 12a, 12c, and 12d have formed on their faces electrical conductors 14a, 14c, 14d, respectively. The conductors 14a and 14c are in a pattern that starts at the top edge of the lamina, extends along the face below the top surface and returns again to the top surface. The conductors 14d extend from the top surface of the lamina along the face to the bottom surface. Some of the laminae represented by laminae 12b may have no conductors and are to control lateral spacing of the ends of the conductors. 
     The required number of the laminae, both with conductors and without, are assembled in face-to-face relationship with the conductor sides oriented in the same direction to form the substrate 10 with their top edges forming a chip mounting surface 16 and their opposite edges forming a reverse surface 18. The assembled ceramic laminae are cured in a conventional manner to form a unitary structure. The method of forming the laminae and the substrate from the laminae is well known in the art and described in said U.S. Pat. Nos. 4,202,007 and 4,193,082 commonly assigned. 
     As seen in the drawing, the completed substrate has on its top surface two patterns of conductor ends 20 separated by an area or strip 22 free of conductor ends. In the drawing the ends of the conductors on the chip mounting surface are shown as dashes (-) which roughly approximates their shape. When surface metallization connects to the conductor ends, as will be described infra, this connection is shown by a circle around the dash. The respective conductors are designated in FIG. 1 by the reference characters 14a, 14c, and 14d at the left hand side. Each dash on the same horizontal line is on the same lamina. The interconnect pattern can be determined from FIGS. 2, 3 and 4. With this technique alternate patterns and conductor free strips can be repeated many times. 
     The spacing of the conductor ends within each of the patterns 20 is so arranged that there is space provided within the patterns to provide for chip mounting sites. These sites can accommodate chip mounting metal pads 24 which are suitable for flip chip bonding of semiconductor chips as well as surface metallization or wiring 26 for connecting chip pads, and/or conductor ends. (This arrangement can also be utilized for wire bonding, or other types of chip bonding.) These pads 24 can be arranged within the site to accommodate selected chips which are to be mounted on the substrate and interconnected thereto by conventional flip chip solder bonding techniques. It will be apparent that many different configurations of chip mounting pads 24 or wiring metallization could be applied at each of the patterns to accommodate the requisite selection of chip mix which is to be used on the substrate. This then allows for the personalization of a single substrate to accommodate a wide variety and mix of chips. Four possible chips in two adjacent patterns are shown, the chips being designated 28, 30, 32, and 34. 
     A combination of the subsurface conductors 14a, 14c, 14d, and mounting surface wiring 26 interconnect the various chips 28, 30, 32, and 34 together, and to input/output (I/O) pins 36 are attached to the rear surface 18 of the substrate. In some cases other types of I/O connections such as edge connections or &#34;bump&#34; connections may be employed rather than I/O pins. As can be seen in FIGS. 1, 2 and 3, the configuration of the conductors 14a and 14c provide subsurface connection between various points on the chip mounting surface. For example, the conductors 14a provide wiring connection between one extreme side of a pattern and the other side, while the conductors 14c provide wiring connections within each pattern as well as subsurface connection between one pattern and the next adjacent pattern beneath the strip 22 on the mounting surface. 
     The strip 22 on the mounting surface provides a relatively large surface area free of the ends of conductor to accommodate a large amount of surface wiring which may require long orthogonal segments, and which wiring connects both conductor ends in the same pattern as well as conductor ends from one pattern across the strip 22 to the conductor ends in the next pattern. Thus by the use of repeating conductor end patterns on the surface interconnected by subsurface conductors together with spaces between the repeating pattern for wiring having long orthogonal segments a single substrate can be used for many combinations of chips. 
     It should be noted that the figures are somewhat simplified in several respects from conventional actual physical embodiments for the purpose of clarification. The modifications include showing only a few laminae forming a substrate whereas many more could be used to provide denser connection and/or a wider substrate. Also, only a selected sample of surface connections and wiring is shown, and this wiring could be much denser. Also, most chips would have more solder connection points than those shown. However, for the sake of clarity, a minimal showing of these various elements is made to illustrate the invention. FIGS. 6A and 6B show a more detailed embodiment of the invention which clearly illustrates the multiple chip mounting and high density features of the invention. 
     The above described technique of formng the substrate from laminae utilizing the edges thereof to form the chip mounting surface is the preferred technology. However, the technology using laminae bonded together in face-to-face relationship with the face of one lamina as the surface as disclosed in said IBM Technical Disclosure Bulletin, Vol. 22, No. 5, October 1979, at pages 1841-1842 could also be used.