Electrical connectors – Including elastomeric or nonmetallic conductive portion – Adapted to be sandwiched between preformed panel circuit...
Reexamination Certificate
1999-05-18
2001-08-07
Patel, Tulsidas (Department: 2839)
Electrical connectors
Including elastomeric or nonmetallic conductive portion
Adapted to be sandwiched between preformed panel circuit...
C439S066000
Reexamination Certificate
active
06270363
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Aspects of the present invention are related to subject matter disclosed in co-pending applications entitled “Copper Stud Process For C4 Pads,” Ser. No. 09/315,374 filed on even date herewith and assigned to the assignee of the present invention, the subject matter of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel interposer for use in the assembly of electronic modules which accommodates the camber on the electronic components while providing improved interconnection.
2. Description of Related Art
In the manufacture and assembly of electronic modules, deformities on the substrate surface make interconnection difficult. Typical ceramic substrates exhibit about 25 to about 50 &mgr;m camber as measured from a flat surface of the substrate. When a device with conventional solder ball interconnections is joined to such a substrate, some of the solder balls will not contact the melting pads leading to opens in the circuitry of the module.
One prior art method of providing better interconnection between the device and substrate is through z-axis films (ZAFs). ZAFs are typically anisotropic electrically conductive adhesive films consisting of thousands of conductive particles dispersed throughout the adhesive film. Contact between the conductive particles when compressing the ZAF provide the electrical pathway.
However, as the demands for miniaturization continues, spacing between particles and the precision in spacing between particles becomes increasingly important. Too many particles may lead to shorts while too few particles may not provide an adequate conductive pathway. Prior art techniques of providing conductive particles in an array that will insure particles at every contact pad of the devices is time consuming and therefore costly.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an apparatus for providing electrical interconnection between electronic components which does not require precise alignment of the interconnections with the contact pads and compensates for substrate camber.
It is another object of the present invention to provide a method and apparatus for assembling an electronic module having improved interconnections.
A further object of the invention is to provide an electronic module which has a substantial reduction in opens between interconnections caused by camber.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
SUMMARY OF THE INVENTION
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, an interposer for electrically and mechanically connecting electronic components comprising an interposer sheet having a plurality of apertures; and a dielectric material having a substantially uniform suspension of conductive particles therein, the plurality of apertures substantially filled with the dielectric material.
Preferably, the apertures filled with the dielectric material form a plurality of conductive sites on the interposer sheet such that a number of conductive sites per unit area is greater than a number of contact pads on an electronic component for a same unit area.
Preferably, the dielectric material is selected from the group consisting of polyimide, siloxane, polyimide-siloxane, and bio-based polymeric resins derived from lignin, cellulose, wood oil and crop oil. Preferably, the conductive particles have a diameter of about 2 to about 20 &mgr;m and is a material selected from the group consisting of copper, gold, silver, nickel, palladium, platinum, and alloys thereof. In an alternative embodiment, the conductive particles may be coated with a material selected from the group consisting of tin, zinc, indium, bismuth, lead and antimony.
The present invention is directed to, in another aspect, a method of assembling an electronic module comprising the steps of (a) providing a first electronic component having one or more contact pads; (b) providing a second electronic component having one or more corresponding contact pads; (c) providing an interposer comprising a compressible interposer sheet having a plurality of apertures greater in number than a number of contact pads; and a dielectric material having a substantially uniform suspension of conductive particles therein, the plurality of apertures substantially filled with the dielectric material forming a plurality of conductive sites; (d) aligning the interposer between the first and second electronic components such that at least one conductive site is aligned between a contact pad on the first electronic component and a corresponding contact pad on the second electronic component; and (e) compressing the first and second electronic components and the interposer such that the conductive particles within the at least one conductive site meet in a substantially z-axis direction to provide interconnection between a contact pad on the first electronic component and a corresponding contact pad on the second electronic component. The method may further include step (f) heating the electronic assembly to bond the interposer to the first and second electronic components.
Preferably, in step (c) the dielectric material is selected from the group consisting of polyimide, siloxane, polyimide-siloxane, and bio-based polymeric resins derived from lignin, cellulose, wood oil and crop oil. Preferably, in step (c) the conductive particles are selected from the group consisting of copper, gold, silver, nickel, palladium, platinum, and alloys thereof. In step (c), the conductive particles may be coated with a material selected from the group consisting of tin, zinc, indium, bismuth, lead and antimony.
Preferably, in step (c) the conductive particles are present in an amount of about 30 to about 90 wt. % of the total weight of the conductive particles and the dielectric material.
The present invention is directed to, in yet another aspect, an electronic module comprising a first electronic component having at least one contact pad; a second electronic component having corresponding contact pads; and an interposer compressed between the first and second electronic components, the interposer comprising an interposer sheet having a plurality of apertures, the apertures substantially filled with a dielectric material having a plurality of conductive particles substantially uniformly suspended within the dielectric material forming a plurality of conductive sites wherein at least one conductive site electrically interconnects a contact pad on the first electronic component to a corresponding contact pad on the second electronic component, the particles within the conductive site being joined together.
Preferably, more than one conductive site is aligned between a contact pad on the first electronic component and a corresponding contact pad on the second electronic component and the particles within the conductive site are contacted together in a substantially z-axis direction to provide interconnection between the first and second electronic components.
Preferably, the dielectric material comprises a material selected from the group consisting of polyimide, siloxane, polyimide-siloxane, and bio-based polymeric resins derived from lignin, cellulose, wood oil and crop oil. Preferably, the conductive particles comprise a material selected from the group consisting of copper, gold, silver, nickel, palladium, platinum, and alloys thereof. In an alternative embodiment, the conductive particles may be coated with a material selected from the group consisting of tin, zinc, indium, bismuth, lead and antimony. Most preferably, the conductive particles are present in an amount of about 30 to about 90 wt. % of the total weight of the conductive particles and the dielectric material.
REFERENCES:
patent: 4008300 (1977-02-01), Ponn
Brofman Peter J.
Knickerbocker John U.
Ray Sudipta K.
Stalter Kathleen A.
Blecker Ira D.
Curcio Robert
DeLio & Peterson LLC
International Business Machines - Corporation
Patel Tulsidas
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