Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-10-09
2004-09-21
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C427S536000, C427S569000
Reexamination Certificate
active
06793759
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for creating adhesion of materials that do not ordinarily exhibit adherent properties. The materials include a polymeric material and a substrate. The polymeric material can be used to connect two components of an electronic device together, such as an integrated circuit chip and a chip carrier.
BACKGROUND
Polymers have found applications in a wide range of technologies but not all polymer materials possess the required physical and chemical properties for good adhesion. Plasma treatment is one means of modifying polymer surfaces to improve adhesion while maintaining the desirable properties of the bulk material.
Adhesion of polymeric materials to similar materials can be improved by plasma, corona, dielectric discharge barrier, or flame treatment with or without assistance of a subsequent thermal treatment during joining process. Examples are films of polyethyleneterephthalate or polyethylene that were bonded to themselves or to each other by lamination under heat and pressure treatment. The mechanisms of adhesion were of the physisorption nature of London dispersion forces and hydrogen bonds. These adhesive joints are susceptible to the effect of external agents such as water or organic solvents and durability can be poor. Other systems related to plasma-treated surfaces, have been focused on surface chemistry changes after plasma treatment of less wettable surfaces such as poly vinyl chloride and polymer fabrics.
One method for improving adhesion is plasma treatment of a substrate, applying a wet or adhesive formulation in an uncured state to the treated surface, and thereafter curing the formulation. For example, one method for bonding two layers of siloxane-polyimide polymers includes bonding by etching (or cleaning) the first layer by using plasma before applying the second layer by spin coating. This method suffers from the drawback of not providing dry adhesion. Plasma treatment is used as an alternative method of surface treating a substrate in a similar manner as a chemical treatment like a hydrochloric or sulfo chromic acid solution. Surface chemical treatment has also been proposed for improved bonding. Treating cured silicone rubber with bromine water etches the low energy surface to produce a high energy surface to which various curable polymeric systems may be directly cured on and bonded. This process has many disadvantages related to handling and disposal of dangerous and toxic chemicals.
Methods for improving adhesion using plasma treatment in electronics applications have been disclosed. For example, one method for improving adhesion between an encapsulant and an IC chip, and between the encapsulant and the chip carrier, employs plasma treatment of either the IC chip or the chip carrier. Another method employs plasma surface modification of a thermoplastic substrate to improve adhesion to an addition curable silicone adhesive. These are both wet applications (i.e., an uncured encapsulant composition is applied to the plasma-modified surface and then cured). Another method discloses that corona or plasma treatment of a tackifier layer in a liquid crystal display improves adhesion between the tackifier and the polarizing sheet or the phase shift sheet. However, none of these methods create adhesion between nonadhesive surfaces.
Plasma surface treatment has also been used in metal deposition or lamination. One method discloses that plasma treatment of fluoro-polymers can improve metal deposition by thermal evaporation, electroless deposition or thermal beam evaporation. Another method discloses that a laminate composed of an insulated base film of a synthetic resin, a metal foil and a silicone adhesive layer, can be made by applying plasma surface treatment of the base film prior to adhesive bonding. These methods suffer from the drawback of not creating adhesion between two dry surfaces by using plasma.
SUMMARY OF THE INVENTION
This invention relates to a method for creating adhesion. The method can be used during fabrication of an electronic device or an electronic device package. The method comprises:
a) plasma treatment of a polymeric material,
b) plasma treatment of an adherend, and
c) thereafter contacting the polymeric material and the adherend; thereby creating adhesion of the polymeric material and the adherend.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
All amounts, ratios, and percentages are by weight unless otherwise indicated. The following is a list of definitions, as used herein.
Definitions
“A” and “an” each mean one or more.
“Combination” means two or more items put together by any means or method.
“Cured” means substantial completion of a chemical process by which molecules are joined together by crosslinking into larger molecules to restrict molecular movements.
“Nonadhesive” means that a polymeric material would not normally adhere to a substrate without treatment.
“Plasma treatment” means exposing a substrate to a gaseous state activated by a form of energy externally applied and includes, but is not limited to, corona discharge, dielectric barrier discharge, flame, low pressure glow discharge, and atmospheric glow discharge treatment. The gas used in plasma treatment can be air, ammonia, argon, carbon dioxide, carbon monoxide, helium, hydrogen, krypton, neon, nitrogen, nitrous oxide, oxygen, ozone, water vapor, combinations thereof, and others. Alternatively, other more reactive gases or vapors can be used, either in their normal state of gases at the process application pressure or vaporized with a suitable device from otherwise liquid states, such as hexamethyldisiloxane, cyclopolydimethylsiloxane, cyclopolyhydrogenmethylsiloxanes, cyclopolyhydrogenmethyl-co-dimethylsiloxanes, reactive silanes, combinations thereof, and others.
Methods
This invention relates to a method for creating adhesion of a polymeric material and a substrate. The method can be used during fabrication of electronic devices and electronic device packages. In one embodiment of the invention, the method comprises:
a) plasma treatment of a polymeric material,
b) plasma treatment of a substrate,
c) plasma treatment of a semiconductor,
d) contacting the polymeric material and the substrate, and
e) contacting the semiconductor and the polymeric material.
In one embodiment of the invention, steps a, b, c, d, and e can be carried out in any of the following orders: abcde, acbde, abced, acbed, bacde, baced, bcade, bcaed, cabde, cabed, cbade, cbaed, abdce, badce, acebd, caebd, abdace, badace, abdcae, badcae, aceabd, caeabd, acebad, or caebad. One skilled in the art would recognize that when a semiconductor and a substrate are both bonded to the polymeric material, plasma treatment of the polymeric material may be carried out more than once, i.e. step a may be repeated. For example, in one embodiment, plasma treatment is carried out on the polymeric material and the substrate, and the polymeric material and the substrate are contacted. Plasma treatment is then carried out separately on the semiconductor and on a different surface of the polymeric material than that contacted with the substrate. The polymeric material and the substrate are then contacted. Plasma treatment can be carried out on all or a portion of the surface of the polymeric material, the substrate, or the semiconductor.
Alternatively, steps a, b, and c can be carried out concurrently and thereafter steps d and e are carried out in any order. Alternatively, steps a, b, and c are carried out in any order, and thereafter steps d and e are carried out concurrently. Alternatively, steps a, b, and c are carried out concurrently, and thereafter steps d and e are carried out concurrently.
In one embodiment of the invention, the polymeric material is contacted with the substrate and optionally the semiconductor as soon as practicable after plasma treatment. In an alternative embodiment, the polymeric material, the substrate, and optionally the semiconductor may optionally each be stored independently before contacting in step d, step e, or both. In one e
Chaudhury Manoj Kumar
Goodwin Andrew James
Lee Yeong Joo
Parbhoo Bhukandas
Aftergut Jeff H.
Brown Catherine U.
Dow Corning Corporation
Haran John T.
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