Compositions – Electrically conductive or emissive compositions
Reexamination Certificate
1999-11-12
2001-11-06
Gupta, Yogendra (Department: 1751)
Compositions
Electrically conductive or emissive compositions
C252S502000, C252S503000, C252S511000, C252S512000, C252S519200, C252S520200, C525S122000, C525S113000, C525S434000, C427S096400, C427S097100, C428S206000, C428S210000, C174S264000, C174S256000, C174S257000, C174S263000
Reexamination Certificate
active
06312621
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to formulations suitable for use as a via fill. Vertical interconnects are discussed in an article of March 9-12, 1997 in Braselton, Ga. by D. Pommer et al., entitled “Vertical Interconnect in Multilayer Applications Using Ormet® Conductive Composites”; and electrically conductive pastes are discussed in EP0708582A1; the disclosures of both are expressly incorporated herein by reference.
SUMMARY OF THE INVENTION
Formulations suitable for use as via fill may be formulated by combining electrically and/or thermally conductive particulate filler, an electrically and thermally conductive polymer, bleed- suppressing agents and a resin system vehicle for electrically and/or thermally conductive versions. Alternatively to a conductive filler, a non-conductive filler may be used for a non-conductive version.
In accordance with one embodiment of the invention the formulation involves a conductive highly moisture resistant cycloaliphatic epoxy/cyanate ester formulation such as may be suitable for use as a via fill for circuit boards and laminate substrates. Advantageously, the via fill formulation may comprise a resin mixture of two cycloaliphatic epoxies, cyanate ester, and epoxidized polybutadiene and a lewis acid catalyst such as a zirconate, titanate, tin, vanadium, zinc, boron or aluminum-based catalyst, as well as electrically and/or thermally conductive particulate filler, including conductive polymers. Conductive polymer may be included to enhance thermal and electrical conductivity and control Theological properties and surface energy properties. Cycloaliphatic epoxies and polybutadiene are useful to adjust the flexibility of the cured system to match the properties to organic-based laminate structures with which the formulation may be used. Additional flexibility may be obtained through use of other long chain polymers such as siloxanes, acrylates, long chain epoxies, urethanes, etc.
The via fill formulations are capable of being adjusted for increased pot life stability and enhanced rheology during via printing, low voiding, high adhesion to copper and high moisture resistance after curing. Pastes formulated from these materials may show enhanced stability under Level 1 Jedec preconditioning.
REFERENCES:
patent: 5571593 (1996-11-01), Arldt et al.
patent: 5716663 (1998-02-01), Capote et al.
patent: 5906042 (1999-05-01), Lan et al.
patent: 5977490 (1999-12-01), Kawakita et al.
patent: 6057402 (2000-05-01), Zhou et al.
patent: 0708582A2 (1996-04-01), None
patent: WO95/13901 (1995-05-01), None
Gallagher et al., “Vertical Interconnect in Multilayer Applications Using Ormet® Conductive Composites”, 1997 International Symposium on Advanced Packaging Materials, pp. 35-37.
Grieve Alan
Iwamoto Nancy E.
Pedigo Jesse L.
Zhou Xiao-Qi
Fish Robert D.
Fish & Associates, LLP
Gupta Yogendra
Hamlin Derrick G.
Johnson Matthey Electronics Inc.
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