Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1999-03-11
2001-06-12
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C361S729000, C361S784000
Reexamination Certificate
active
06246016
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to mounting techniques for electronic components and, more specifically, to an edge-mountable integrated circuit (IC) package and method of attaching the same to a printed wiring board (PWB).
BACKGROUND OF THE INVENTION
The burgeoning electronics industry has been driven by consumer and commercial needs for more and more complex electronic assemblies in ever smaller spaces. With the conversion from vacuum tubes to integrated circuits, electronics transitioned from individual hand-wired components on a major chassis to printed wiring board (PWB) assemblies with integrated circuit subassemblies thereon. In the early days of electronics, virtually all of the electronic parts were interconnected by wires routed primarily on the underside of the chassis. As transistors, and then integrated circuits, came into widespread use, it became possible to group major electronic functions together on designated areas of the chassis. The chassis evolved to a “motherboard” when it became possible to move some functions to smaller PWBs or “daughterboards.” The terms “motherboard” and “daughterboard” in this context are not limited to computer applications but include any electronic devices with PWBs that function in the general manner described.
PWB assemblies comprise a substantially flat, rectangular package having two parallel major surfaces and a number of minor surfaces, or edges, normal to the major surfaces. The major and minor surfaces are designated as such to indicate that a surface area of the major surface is greater than a surface area of the minor surface. Arbitrarily for the sake of this discussion, motherboards are considered to be mounted horizontally; however daughterboards, may mount horizontally or vertically. Of course, there are applications where the motherboard is vertical. Horizontal mounting places the major surfaces of the motherboard and daughterboard substantially parallel. Vertical mounting places the major surface of the daughterboard normal to the major surface of the motherboard. Vertical mounting also allows designers to package more electronics into less area of the motherboard, thereby reducing the overall footprint of the electronic devices. Therefore, some means of mechanically attaching and electrically interconnecting the PWB subassemblies/daughterboards to the motherboard is extremely important. Interconnecting the daughterboards for removable/replaceable functions, such as a modem, video card, disk drive controllers, etc., is usually accomplished by edge card connectors with friction fit contacts spaced 0.1″ apart on center. Some daughterboard functional subassemblies, however, are essential to the overall function of the electronic device and therefore require permanent connection to the motherboard. Traditionally, permanently installed, single in-line packages (SIPs) are electrically connected to the motherboard with either plug connectors or edge card connectors that can be reflow soldered to the motherboard. Alternatively, electrical connections between the daughterboard and the motherboard may be accomplished with wire when the boards are mechanically coupled without electrical interconnnections. Of course, plug connectors, edge card connectors and wire connections add to the complexity and cost of the total assembly. Both of these techniques are expensive and have the additional disadvantage of unwanted inductance upon assembly.
Accordingly, what is needed in the art is an edge-mountable integrated circuit package and a method of attaching the package to a printed wiring board that minimizes both inductance, space and cost.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides an edge-mountable integrated circuit (IC) package and methods of manufacturing and assembling the same onto a printed wiring board (PWB). In one embodiment, the package includes: (1) a substrate having a major surface and a substantially planar edge and (2) a conductive coating having a first region located on a portion of the major surface and a second region located on a portion of the substantially planar edge, the second region being substantially planar to allow the second region to be reflow soldered to the adjoining printed wiring board PWB.
The present invention therefore avoids the edge connectors and wire bonds of the prior art, allowing a substrate to be joined edge-on directly to a PWB. The present invention is effected by providing a conductive coating on the edge of the substrate, which then can be used in an otherwise conventional solder reflow process to join the substrate to the PWB.
In one embodiment of the present invention, the package further includes a second conductive coating having a first region located on a second portion of the major surface and a second region located on a second portion of the substantially planar edge, the second region of the second conductive coating being substantially planar to allow the second region to be concurrently reflow soldered to the adjoining PWB. Thus, a single edge can accommodate more than one region (terminal). In one embodiment to be illustrated and described, the second region extends over less than half a width of the substantially planar edge, allowing conductive coatings to be placed in tandem along the length of the substantially planar edge. Each conductive coating can be routed to its respective adjacent major surface, effectively doubling the number of terminals that the package is allowed to have. Of course, tandem location need not be provided.
In one embodiment of the present invention, the substrate is composed of a resin-impregnated glass fiber. However, other conventional and later-discovered substrate materials that are capable of accommodating a conductive coating are within the broad scope of the present invention.
In one embodiment of the present invention, the first region comprises a conductive trace. Thus, the coating may be coupled to, or form a part of, a conventional surface or inter-layer trace for conducting current along or under the major surface.
In one embodiment of the present invention, the package further includes first and second extensions projecting from the substantially planar edge and adapted to engage corresponding first and second apertures in the PWB. In a more specific embodiment of the present invention, the package further includes the PWB and wherein the first and second apertures have an offset periphery to impress a bending moment on the substrate when the first and second extensions are engaged in the corresponding apertures. In an embodiment to be illustrated and described, the apertures may be formed by a rotating tool having a diameter exceeding the thickness of the substrate. The apertures can be employed to place the substrate in a bind, frictionally securing the substrate to the PWB pending reflow soldering.
In one embodiment of the present invention, the substantially planar edge contains first and second notches. The first notch is located proximate a first edge of the conductive coating. The second notch is located proximate a second edge of the conductive coating. The notches ensure that the substantially planar edge having the conductive coating stands out such that it can contact the PWB. This is advantageous if the PWB is not absolutely planar.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from
Roessler Robert J.
Woods, Jr. William L.
Lucent Technologies - Inc.
Paladini Albert W.
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