Abstract:
An apparatus is disclosed that improves density of electrical components in a circuit assembly. Electrical components  202, 204  are stacked so that they overlap each other and are encapsulated in an electronic insulating material  104 . The resulting subassembly may be integrated onto a printed circuit board or into a reverse-interconnection process assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/962,627, filed on Jul. 31, 2007, hereby incorporated by reference in its entirety; U.S. Provisional Application No. 60/963,822, filed on Aug. 6, 2007, hereby incorporated by reference in its entirety; U.S. Provisional Application No. 60/966,643, filed on Aug. 28, 2007, hereby incorporated by reference in its entirety; U.S. Provisional Application No. 61/038,564, filed on Mar. 21, 2008, hereby incorporated by reference in its entirety; U.S. Provisional Application No. 61/039,059 filed on Mar. 24, 2008, hereby incorporated by reference in its entirety; and U.S. Provisional Application No. 61/075,238 filed on Jun. 24, 2008, hereby incorporated by reference in its entirety. 
     This application is a continuation-in-part application of pending U.S. patent application Ser. No. 12/119,287, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; U.S. patent application Ser. No. 12/163,870, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; PCT Patent Application No. PCT/US2008/065131, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; U.S. patent application Ser. No. 12/170,426, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; and U.S. patent application Ser. No. 12/182,043, ASSEMBLY OF ENCAPSULATED ELECTRONIC COMPONENTS TO A PRINTED CIRCUIT BOARD; hereby incorporated by reference in their entirety. 
    
    
     COPYRIGHT NOTICE AND PERMISSION 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     FIELD OF THE INVENTION 
     The present invention relates to the field of electronic assembly and more specifically to the manufacture and assembly of electronic products having overlapping components. 
     BACKGROUND OF THE INVENTION 
     Historically, most electronic products have been assembled using a solder material and a soldering process. This has always had disadvantages, and a number of new trends are revealing or exacerbating other disadvantages. 
     One set of disadvantages relates to solder materials themselves. Since the earliest days of the electronics industry tin/lead type solders (e.g., Sn63/Pb37) have been widely used. Unfortunately, both tin and especially lead have serious chemical disadvantages. For these two metals, mining the ores, refining it, working with the refined metals during manufacturing, being exposed to the substances in manufactured products, and disposing of the products at the ends of their life cycles are all potentially damaging to human health and to the environment. 
     Recently human health and environmental concerns about tin/lead type solders have resulted in the Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (commonly referred to as the Restriction of Hazardous Substances Directive or RoHS) in the European Union. This directive restricts the use of six hazardous materials, including lead, in the manufacture of various types of electronic and electrical equipment. This directive is also closely linked with the Waste Electrical and Electronic Equipment Directive (WEEE) 2002/96/EC, which sets collection, recycling, and recovery targets for electrical goods. Together these directives are part of a growing world-wide legislative initiative to solve the problem of electronic device waste. 
     To some extent the electronics industry has always been searching for a practical substitute for tin/lead type solders, and legislative initiatives like those just noted are now motivating a number of changes. Today a common substitute for tin/lead type solders are SAC type solder varieties, which are alloys containing tin (Sn), silver (Ag), and copper (Cu). But this is merely a compromise. Mining, refining, working during manufacturing, exposure from manufactured products, and disposal are still all issues for tin, silver, and copper. It therefore suffices here to say that the undue use of some materials, like solder, is generally undesirable in electronic assemblies. Another set of disadvantages in the solder-based assembly of electronic products is the heat-based processes that are inherently required. The use of heat on and around many electronic components has always been undesirable. As a general principle, the heating of electronic components increases their failure rate and beyond a certain point outright damages such components. Tin/lead solders melt at relatively low temperatures, and their use has generally been tolerable for many components. This is not as frequently the same for SAC type solders, however, which melt at much higher temperatures. When SAC type solders are used, the likelihood of component damage is much higher, resulting in assemblies that fail during post-manufacturing testing as well as in-the-field failures. Additionally, generating and managing the heat during manufacturing have energy, safety, and financial costs. In addition, the undue use of lead-based manufacturing processes, like soldering, is also generally undesirable in electronic assemblies. 
     Increasingly yet another set of disadvantages in the solder-based assembly of electronic products is related to the “adding” of materials. When a material, like solder, is added between two components to hold them together, the additional material inherently has to occupy some space. The use of liquid-state materials, like solder in its liquid stage, in manufacturing often requires additional space around leads, terminals, and pads because both product and process designs need to account for the ability of liquid to flow easily and thus to potentially short to other leads, terminals, pads, etc. Liquid surface tension effects are also usually a major consideration in such designs, as liquid solders have high surface tensions. These all thus are factors as designers increasingly strive to miniaturize electronic assemblies. So the undue use of additional material, including solder, in manufactured assemblies and manufacturing processes is generally undesirable. 
     The density of components on circuit boards may be increased by building up in a vertical direction. Components may be stacked one on top of another. This type of assembly reduces size and cost. It is also amenable to manufacture by means of reverse-interconnection process (RIP) as disclosed in related U.S. patent application Ser. No. 12/119,287, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; U.S. patent application Ser. No. 12/163,870, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; PCT Patent Application No. PCT/US2008/065131, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; U.S. patent application Ser. No. 12/170,426, ELECTRONIC ASSEMBLIES WITHOUT SOLDER AND METHODS FOR THEIR MANUFACTURE; and U.S. patent application Ser. No. 12/182,043, ASSEMBLY OF ENCAPSULATED ELECTRONIC COMPONENTS TO A PRINTED CIRCUIT BOARD; hereby incorporated by reference in their entirety and assigned to the assignee of the present invention. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide improved assemblies of electronic components on circuit boards and in RIP assemblies. 
     It is a further object of the present invention to provide a solder or solderless apparatus joining electrical components, so that numerous electronic components may be electrically interconnected. 
     It is a further object of the present invention to provide a solder or solderless apparatus joining electrical components, so that electronic components are stacked upon each other and are electrically interconnected and integrated. 
     To improve the density of electrical components in a circuit assembly, components can be overlapped. In addition, the components can be encapsulated in an electronic insulating material. This assembly offers significant design benefits in solderless assembly including an increase in routing channels, a reduction in layer count, and an elimination of solder shorts and opens however, as previously stated they can be used as components either integrated or simply bonded to one another to create a stacked assembly without encapsulation, again however, lead frame components would potentially be subject to bending out of alignment. 
     These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the figures of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The purposes and advantages of the present invention will be apparent from the following detailed description in conjunction with the appended figures of drawings in which: 
         FIG. 1  shows a circuit subassembly viewed from a lead termination side. 
         FIG. 2  is a cross-section of the apparatus shown in  FIG. 1  taken along  1 - 1 . 
         FIG. 3  shows a circuit subassembly viewed from a lead termination side. 
         FIG. 4  is a cross-section of the apparatus shown in  FIG. 3  taken along  3 - 3 . 
         FIG. 5  shows a circuit subassembly viewed from a lead termination side. 
         FIG. 6  is a cross-section of the apparatus shown in  FIG. 5  taken along  5 - 5 . 
         FIG. 7  shows a circuit subassembly viewed from a lead termination side. 
         FIG. 8  is a cross-section of the apparatus shown in  FIG. 7  taken along  7 - 7 . 
         FIG. 9  shows a circuit subassembly viewed from a circuit trace side. 
         FIG. 10  is a cross-section of the apparatus shown in  FIG. 9  taken along  9 - 9 . 
     
    
    
     In the various figures of the drawings, like references are used to denote like or similar elements or steps. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The foregoing description details specific embodiments of the invention and are included for illustrative purposes. However, it will be apparent to one skilled in the art that many combinations and permutations of the following embodiments are possible while remaining within the scope and spirit of the invention. 
       FIG. 1  shows a subassembly  100  viewed from the lead termination (also referred to “pad” or “land” in the art) side of components encapsulated in electrical/electronic insulating material  104 . Exposed are terminations such as gull wing component lead termination  102  and discrete or analog component lead termination  106 . 
       FIG. 2  is a section taken along  2 - 2  of  FIG. 1  of subassembly  100 . Shown previously in  FIG. 1 , the relative positions of electronic insulating material  104 , exposed terminations, such as gull wing component lead termination  102  and discrete or analog component lead termination  106 , are shown in  FIG. 2 . Upper gull wing component package  202 , having lead  208 , is mounted on middle component package  204 . Lead  208  extends beyond package  204  and reaches a surface of electronic insulating material  104 . Middle component package  204  is mounted on discrete or analog component  206  whose lead termination surface  106  reaches the surface of electronic insulating material  104 . Termination surface  102  and termination surface  106 , as well as other termination surfaces, are exposed and available for electrical connection to other terminations, traces, and/or a PCB. 
       FIG. 3  shows a subassembly  300  viewed from the lead termination side of components encapsulated in electronic insulating material  304 . Exposed are terminations such as blind via plated interconnection termination surface  302  and land grid array (LGA) integrated circuit (IC) package termination surface  306 . 
       FIG. 4  is a section taken along  4 - 4  of  FIG. 3  of subassembly  300 . Shown previously in  FIG. 3 , the relative positions of electronic insulating material  304 , exposed terminations, such as component lead termination  302  and component lead termination  306 , are shown in  FIG. 4 . Upper component package  402 , having area array IC package wiring substrate  410  and blind via plated interconnection lead  408 , is mounted on lower component package  404 . In turn, component package  404  has area array IC package wiring substrate  412 . Lead  408  extends beyond substrate  410  and reaches a surface of electronic insulating material  304 . A via extends from the surface of material  304  into lead  408 . Component package  404 , through substrate  412 , has termination surface  306  reaching the surface of electrical/electronic insulating material  304 . Lead  408  and termination surface  306 , as well as other termination surfaces, are exposed and available for electrical connection to other terminations, traces, and/or PCB&#39;s. 
       FIG. 5  shows a subassembly  500  viewed from the lead termination side of components encapsulated in electronic insulating material  504 . Exposed are terminations such as distal end of pin grid array termination  502  and LGA IC package termination surface  506 . 
       FIG. 6  is a section taken along  6 - 6  of  FIG. 5  of subassembly  500 . Shown previously in  FIG. 5 , the relative positions of electronic insulating material  504 , exposed terminations, such as component lead termination  502  and component lead termination  506 , are shown in  FIG. 6 . Upper component package  602 , having area array IC package wiring substrate  610  and pin grid array lead  608 , is mounted on lower component package  604 . In turn, component package  604  has area array IC package wiring substrate  612 . Lead  608  extends beyond substrate  610  and reaches a surface of electronic insulating material  504 . Component package  604 , through substrate  612 , has termination surface  506  reaching the surface of electronic insulating material  504 . Lead  608  and termination surface  506 , as well as other termination surfaces, are exposed and available for electrical connection to other terminations, traces, and/or PCB&#39;s. 
       FIG. 7  shows a subassembly  700  viewed from the lead termination side of components encapsulated in electronic insulating material  704 . Exposed are terminations such as distal end of ball grid array (BGA) termination  702  and OFN IC package termination surface  706 . 
       FIG. 8  is a section taken along  8 - 8  of  FIG. 7  of circuit assembly  700 . Shown previously in  FIG. 7 , the relative positions of electronic insulating material  704 , exposed terminations, such as distal end of ball grid array (BGA) termination  702  and OFN IC package termination surface  706 , are shown in  FIG. 8 . Upper component package  802 , having area array IC package wiring substrate  810  and ball termination  808 , is mounted on a first lower component package  804  and a second lower component package  805 . Ball termination  808  reaches a surface of electronic insulating material  704 . Second component package  805  has termination surface  706  reaching the surface of electrical/electronic insulating material  704 . Ball termination  702  and termination surface  706 , as well as other termination surfaces, are exposed and available for electrical connection to other terminations, traces, and/or PCB&#39;s. 
       FIG. 9  shows a circuit subassembly  900  viewed from the circuit trace side. Exposed are traces such as trace  908 . 
       FIG. 10  is a section taken along  10 - 10  of  FIG. 9  of circuit subassembly  900 . Previously shown in  FIG. 9 , the relative position of trace  908  is shown in  FIG. 10 . Upper gull wing component package  1002 , having lead  1008 , is mounted on middle component package  1004 . Lead  1008  extends beyond package  1004  and reaches a surface of electrical/electronic insulating material  904 . Middle component package  1004  is mounted on discrete or analog component  1006  whose lead termination surfaces reach the surface of electronic insulating material  904 . Termination surface  902 , as well as other termination surfaces, are exposed and available for electrical connection to other terminations, traces, and/or a PCB. Vias filled with electrically conductive material, such as filled via  1014 , connect termination surfaces to traces. In turn, traces such as trace  908 , connect filled vias surfaces with one another (shown also in  FIG. 9 ). 
     The foregoing description details specific embodiments of the invention and are included for illustrative purposes. However, it will be apparent to one skilled in the art that many combinations and permutations of the described embodiments are possible while remaining within the scope and spirit of the invention. For example, numerous similar or different types of electrical components may be mounted and overlap each other in multiple layers. Examples of types of electrical components include, but are not limited to, discrete or analog components, gull wing components, IC, LGA, BGA, CGA, QFN, QFP, TSOP, OFN, and PGA components, and other lead frame package and area array components. Preferably such components are fully tested and burned in before being committed to assembly. 
     As indicated above, this application is a continuation-in-part of applications U.S. patent application Ser. Nos. 12/119,287, 12/163,870, 12/170,426, 12/182,043, and PCT Patent Application No. PCT/US2008/065131, hereby incorporated by reference in their entirety. The subassemblies shown in  FIGS. 1 to 10  can be incorporated into the reverse-interconnection process (RIP) assemblies disclosed and described in the above referenced applications. That is, the subassemblies can be mounted on a substrate with vias extending through the substrate to lead terminations (Ser. No. 12/119,287) and/or traces. The substrate may be flexible (Ser. No. 12/163,870). The subassemblies may be mounted back to back (PCT/US2008/065131). The subassemblies may be mounted on a foil base (Ser. No. 12/170,426). And the subassemblies may be joined and interconnected to a central bonding material which is connected to a PCB (Ser. No. 12/182,043). 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and that the breadth and scope of the invention should not be limited by any of the above described exemplary embodiments, but should instead be defined only in accordance with the following claims and their equivalents.