Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-27
2002-12-03
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S428000, C523S434000, C525S113000, C525S122000, C525S524000
Reexamination Certificate
active
06489380
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resin composition useful in the formulation of die attach adhesives, encapsulants, underfills, via fills, prepreg binders, polymer solder masks and polymer bumps on flip chip or BGA assemblies.
As uses for semiconductor devices continue to increase, there is a growing demand for adhesive compositions and resin formulations useful in the packaging of such devices both on the board and substrate level. Adhesives are used, for example, to attach dies to semiconductor packages under a variety of conditions. Underfills are used to reduce stress and increase the reliability of solder ball joints found between the substrate, i.e., package, and the die. Encapsulants are used to completely encapsulate, seal and bond a die to a semiconductor package. Via fills are used in both board and laminate substrates to fill the vias in the substrate. Binders found in the manufacture of printed circuit boards and laminate substrates are needed as part of the structural composite of the laminate, serving to bind various metal layers and circuitry together into a single functioning unit. The alternating layers of circuitry, metal planes and vias, along with a matte material, such as glass fibers (which help with structural integrity), are bound together with the organic polymer binder to create the total laminate. Simple layered structures of glass and binder are often sold in a pre-cured state call “prepregs”, which are later head-bonded or laminated together as part of the process that creates the laminate substrate or printed circuit board.
To be useful in the manufacture of semiconductor devices, die attach adhesives and the like must meet certain performance, reliability and manufacturability requirements as dictated by the particular application. Performance properties for which there are typically minimum requirements include adhesion, coefficient of thermal expansion, flexibility, temperature stability, moisture resistance and the like. Reliability requirements are typically evaluated by the device's sensitivity to moisture-induced stress. Manufacturability requirements generally include specific requirements for rheology, cure rates and usable pot life and the like. For both the via fill and laminate structures, properties must be met that exhibit superior dimensional stability to processes such as plating, machining, sanding and baking.
Moisture resistant and flexible materials are highly desirable for the manufacture of semiconductor devices. Moisture inside a package turns to steam and expands rapidly when the package is exposed to high temperatures (for instance during solder reflow, infrared or convection baking, or if the package is contacted by molten solder). Under certain conditions, moisture induced pressure will initialize package failure such as internal delamination in the interfaces, internal cracking, wire necking, bond damage. and of course the obvious external crack i.e. popcorning.
Resin compositions comprising a cyanate ester and epoxy resins have been demonstrated to be useful as die attach adhesives, underfills, and the like. While the performance characteristics for such resin compositions are adequate for some applications, there is a continuing need to improve reliability and manufacturing performance of the compositions. Currently available compositions address some, but not all, of the following performance criteria: long pot life, fast cure. and high adhesion. Currently available materials tend to exhibit high rigidity with a Young's modulus of 4-7 GPa at room temperature and low moisture resistance. A need therefore exists for compositions that exhibit adequate flexibility while providing sufficient moisture resistance.
SUMMARY OF THE INVENTION
In one embodiment, the present invention is directed to a composition comprising an organic component and a filler, wherein the organic component comprises at least one longchain cycloaliphatic epoxy resin, at least one short-chain cycloaliphatic epoxy resin, at least one cyanate ester, and at least one Lewis acid catalyst. Preferably the composition further comprises a bronsted acid co-catalyst and/or a flexibilizing modifier.
In another embodiment, the invention is directed to a method for preparing a die attach adhesive comprising preparing a formulation comprising a composition as described above, dispensing the formulation onto a substrate, and curing the formulation.
In still another embodiment, the invention is directed to a method for preparing an underfill comprising preparing a formulation comprising a composition as described above to a rheology suitable for dispensing purposes, dispensing the formulation onto a substrate, and curing the formulation.
In yet another embodiment, the invention is directed to a method for preparing an encapsulant comprising preparing a formulation comprising a composition as described above. dispensing the formulation onto an electrical component, and curing the formulation.
The invention is also directed to a method for preparing a via fill comprising: preparing a formulation comprising a composition as described above, printing the formulation into one or more holes in a substrate, and curing the formulation.
Additionally, the invention is directed to a method for preparing a prepreg binder comprising preparing a formulation comprising a composition as described above, impregnating the formulation into a matte, and B-staging the formulation.
Another aspect of the invention is a method for preparing a polymer solder mask comprising preparing a formulation comprising a composition as described above and at least one catalyst capable of serving as a photoinitiator, applying a film of the formulation onto a substrate to form a formulation-coated substrate, photoimaging the formulation-coated substrate, curing the formulation, and developing the formulation-coated substrate.
Yet another aspect of the invention is a method for preparing polymer bumps on a flip chip or BGA assembly comprising preparing a formulation comprising a composition as described above, printing the formulation onto a substrate to form polymer bumps, B-staging the formulation, contacting the polymer bumps with a bond pad to form an electrical contact, and curing the formulation onto the bond pad.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment, the present invention is directed to a composition particularly suitable for die attach adhesives, underfills and the like. The composition comprises an organic component and a filler. The organic component comprises a long-chain cycloaliphatic epoxy resin, a short-chain cycloaliphatic epoxy resin, a cyanate ester, and a Lewis acid catalyst.
One or more long-chain cycloaliphatic epoxy resins are included to impart flexibility to the composition. A long-chain cycloaliphatic epoxy resin is one having a long chain containing at least 4 carbon atoms between the cycloaliphatic groups. Preferably the long chain does not contain any cyclic groups. Particularly suitable long-chain cycloaliphatic epoxy resins useful in the present invention include, but are not limited to, bis[3,4-epoxy-cyclo-hexyl-methyl]-adipate (CAS # 3130-19-6) (for example, that sold under the trademark ERL4299 by Union Carbide of Danbury, Conn.), and cycloaliphatic mono- and di-epoxy oligosiloxanes such as epoxidized &agr;,&ohgr;-di-(3,4 cyclohexene-2-ethyl)-tetramethyl disiloxane, epoxidized &agr;,&ohgr;-di-(3,4 cyclohexene-2-ethyl-hexamethyl trisiloxane, and epoxidized &agr;-3,4-cyclohexene-2-ethyl pentamethyldisiloxane (these resins can be obtained, for example, as described in J. Poly. Sci. Poly. Chem., 28:479-502 (1990), the disclosure of which is incorporated herein by reference). The total amount of long-chain cycloaliphatic epoxy resins in the composition preferably ranges from about 5% to about 20 % by weight, more preferably about 12% to about 15% by weight, still more preferably about 13.4% by weight, based on the total weight of the organic component.
One or more short-chain cycloaliphatic epoxy resins a
Grieve Alan
Iwamoto Nancy E.
Li Shao Wei
Wevick Henry
Zhou Xiao-Qi
Fish Robert D.
Johnson Matthey Electronics Inc.
Rutland & Tucker, LLP
Sellers Robert E. L.
Thompson Sandra P.
LandOfFree
Long and short-chain cycloaliphatic epoxy resins with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Long and short-chain cycloaliphatic epoxy resins with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Long and short-chain cycloaliphatic epoxy resins with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2931367