Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2000-06-30
2001-11-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S343000, C428S3550RA, C428S413000, C428S447000, C428S354000
Reexamination Certificate
active
06312801
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an adhesive tape through which electronic parts at the environs of a lead frame, such as leads, diepads and radiant plate semiconductor chips, are bonded to each other.
2. Description of the Related Art
Conventional adhesive tapes for use in resin package semiconductor devices may be exemplified by lead frame-fixing adhesive tapes, adhesive tapes for radiant plates, and TAB carrier tapes. With regard to a lead frame-fixing adhesive cape, it is used to fix a lead of a lead frame, so as to enhance the production yield and productivity for the lead frame itself as well as in the whole semiconductor assembly process. Generally, the adhesive tapes are applied on lead frames by lead frame makers and these are used to mount semiconductor chips which are then packaged in a resin by semiconductor assemblers. With regard to these functions, the adhesive tapes for use in fixing lead frames are required to be superior in the reliability, the workability upon taping and the adhesiveness after work as well as to show thermal resistance sufficient to overcome the heating in the assembly process of semiconductor devices.
Examples of the conventional adhesive tapes for these purposes include those in which polyacrylonitrile, polyacrylate or an acrylonitrile-butadiene copolymer alone or in combination with thermosetting resins is coated on thermal resistant support films, such as polyimide films. Recently, the package structures of semiconductor devices, however, have become complex owing to the requirement for multi-pin structure and heat radiation in the semiconductor devices and the organic materials used in the adhesive tapes have been strictly required to be superb in electrical, physical and thermal properties and in handling. Conventional adhesive tapes do not meet the requirements for sufficient thermal properties, dimensional stability and electrical properties. Particularly, when lead pins are bonded to heat sinks or connected to semiconductor chips through conventional insulating tapes, there is a serious problem in that the metallic materials, such as lead frames, might be bent or damaged.
To solve the problems, U.S. Pat. Nos. 5,494,757 and 5,500,294 disclose liquid adhesives comprising a piperazinylethylaminocarbonyl-containing butadiene-acrylonitrile copolymer and a compound having at least two maleimide groups optionally in combination with a diamine-containing polysiloxane compound. These liquid adhesives can be adhered and cured at a relatively low temperature and have sufficient heat resistance and electrical properties, but suffer from a significant problem of generating a large quantity of out gas or being poor in water logging tolerance.
BRIEF OF THE INVENTION
It is an object of the present invention to overcome the problems encountered in prior art and to provide an adhesive tape suitable for use in fixing electronic parts, which can be adhered and cured at relatively low temperatures and is superior in thermal resistance, electrical properties, water logging tolerance and out gas generation.
In accordance with the present invention, the above object could be accomplished by a provision of an adhesive tape which is based on a heat resistant film on one side or both sides of which an adhesive composition comprising 100 weight parts of an acryl resin with an average molecular weight ranging from 100,000 to 2,000,000, containing at least one functional group selected from a carboxyl group, an alcohol group, a sulfonyl group, a glycidyl group, and an amino group, 20-500 weight parts of a bisphenol A-type epoxy resin and 10-200 weight parts of a cresol novolak epoxy or a phenol novolak epoxy resin, 10-200 weight parts of a maleimide compound having at least two intramolecular maleimide groups, an aromatic diamine compound, and an epoxy-containing liquid silicon resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention contemplates an adhesive composition comprising an acryl resin (component A), a mixed epoxy resin (component B) of a bisphenol A-type epoxy resin and a cresol novolak epoxy or a phenol novolak epoxy resin, a bismaleimide compound (component C), an aromatic diamine compound (component D), an epoxy-containing liquid silicon resin (component E) and an organic or inorganic filler (component F).
The acryl resin (component A) useful in the present invention ranges, in weight average molecular weight, from 100,000 to 2,000,000 and, in glass transition temperature, from −50 to 150° C. and contains at least one functional group selected from a carboxyl group, an alcohol group, a sulfonyl group, a glycidyl group, and an amino group. For example, if the weight average molecular weight is below 100,000, the resulting adhesive composition is poor in thermal stability, adhesiveness and thermal resistance. On the other hand, if the weight average molecular weight is over 2,000,000, poor solubility results, so that the solution is too viscous to be handled with ease.
The acryl resin is prepared by copolymerizing a mixture comprising 10-60 weight % of acrylonitrile, 20-80 weight % of alkyl acrylonitrile whose alkyl moiety contains 2-12 carbon atoms, and 0.1-20 weight % of a monomer with a double bond to at least one functional group selected from a carboxyl group, an alcohol group, a sulfonyl group, a glycidyl group and an amino group. Less than 0.1 weight % of the functional group-containing monomer deleteriously affects the adhesiveness and thermal resistance while, when the monomer is present at an amount of more than 20 weight %, poor stability in a solution state is obtained.
As for the mixed epoxy resin (component B) used in the present invention, it is obtained from a mixture of a bisphenol A-type epoxy resin and a cresol novolak epoxy resin or a mixture of a bisphenol A-type epoxy resin and a phenol novolak epoxy resin. Based on 100 weight parts of the component A, the bisphenol A-type epoxy is added at an amount of 20-500 weight parts and preferably 80-200 weight parts and the cresol novolak epoxy or phenol novolak epoxy is added at an amount of 10-200 weight parts and preferably 40-100 weight parts. If the bisphenol A-type epoxy is present at an amount of less than 20 weight parts, the resulting composition shows poor adhesiveness. On the other hand, if too much bisphenol A-type epoxy is used, low thermal resistance is given. Less than 10 weight parts of the cresol novolak epoxy or phenol novolak epoxy brings debasement into the thermal resistance of the composition. When used at an amount exceeding 200 weight parts, the cresol novolak epoxy or phenol novolak epoxy produces a problem in adhesiveness.
The bismaleimide resin (component C) useful in the present invention is a compound having at least two intramolecular maleimide groups, as represented by the following chemical formula I or II:
It is preferably used at an amount of approximately 10-200 weight parts based on 100 weight parts of the component A. For example, less than 10 weight parts of the component C causes deterioration in thermal resistance, modulus of elasticity after curing, and mechanical strength while too excessive amounts of the component C reduce the adhesiveness of the composition.
Compared with the quantity of the epoxy resin and bismaleimide resin, it is important to use a proper quantity of the component D (the aromatic diamine compound). Preferable amounts of the component D fall in the range of approximately 1-100 weight parts based on 100 weight parts of the sum of the components B and C. Excess or insufficient amounts of the component D cause a problem in solvent resistance, thermal resistance and electric resistance. In the present invention, it is recommended that aromatic diamine compounds superior in electrical properties, thermal resistance and chemical resistance are used. A curing agent may be used to promote a curing reaction.
As for the liquid silicon resin (component E), it has epoxy groups. The silicon moiety plays an important role in providing a chemical association within the
Chang Kyeong Ho
Jin Hwa Il
Kim Soon Sik
Dawson Robert
Feely Michael J
Harrison & Egbert
Saehan Industries Incorporation
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