United States Patent (19)
`Komiyama et al.
`
`(54) METHOD OF DICING AND BONDING
`SEMCONDUCTOR CHIPS USING A
`PHOTOCURABLE AND HEAT CURABLE
`ADHESIVE TAPE
`Mikio Komiyama, Yokohama;
`75) Inventors:
`Yasunao Miyazawa, Urawa;
`Kazuyoshi Ebe, Saitama; Takanori
`Saito, Ohmiya, all of Japan
`Lintec Corporation, Tokyo, Japan
`653,232
`Feb. 8, 1991
`
`Assignee:
`Appl. No.:
`Filed:
`
`73)
`21
`22)
`
`Related U.S. Application Data
`Division of Ser. No. 380,548. Jul 14, 1989.
`62)
`Foreign Application Priority Data
`(30)
`Jul. 21, 1988 JP
`Japan ................................ 63-18358
`(5) int. Cl.' .............................................. B32B 31/OO
`52) U.S. C. .................................... 156/229; 156/235;
`56/249; 156/256; 156/273.3; 156/273.9;
`156/275.5; 156/330; 428/345
`(58) Field of Search ............... 156/272.2, 273.3, 273.9,
`156/275.5, 250, 256. 344, 229, 249, 230, 235,
`330, 428/42, 343, 345, 354, 355
`References Cited
`U.S. PATENT DOCUMENTS
`4.28.79 SA980 Green ............................... 56/273.3
`4,286,047 8/1981 Bennet et al. ................. S6A344 X
`
`(56)
`
`
`
`|||||||||||||||III
`USOOS 10388A
`(1) Patent Number:
`5,110,388
`(45) Date of Patent:
`May 5, 1992
`
`4,664,239 SA98. Aurichic ............................. 156A344
`4,698, 113 10/1987 Ogawa ............
`56A22. X
`4.720,317 A988 Kuroda et al. ..
`56A2.2 X
`4,756,968 7/988 Ebe et al. ............................ 428A343
`4.793,883 2/1988 Sheyon et al. ...................... 1562.49
`4,961,804 0/1990 Aurichio ......................... 1S6344 X
`Primary Examiner-Richard Bueker
`Assistant Examiner-Chester T. Barry
`Attorney, Agent, or Firm-Wenderoth, Lind & Ponack
`(57)
`ABSTRACT
`An adhesive tape comprising an energy bearn transmit
`table base sheet having a surface tension of not more
`than 40 dyne/cm and an adhesive layer formed on one
`surface of the base sheet, the adhesive layer comprising
`a (meth)acrylate polymer, an epoxy resin, a photopo
`lymerizable low molecular weight compound, a heat
`activatable potential curing agent for the epoxy resin
`and a photopolymerization initiator for the photopo
`lymerizable low molecular weight compound. The ad
`hesive in the adhesive layer is curable with an energy
`beam and the so cured adhesive develops tackiness
`again when heated. When the tape is used in processing
`a semiconductor wafer, it serves as a dicing tape for
`holding the wafer in position during the dicing step.
`Each piece of the diced and cured adhesive layer, that
`is attached to each chip and capable of being tackified
`by heating, provides an adhesive required for securely
`mounting the chip on the lead frame in the die-bonding
`step.
`
`8 Claims, 2 Drawing Sheets
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`E.
`E.
`E.
`E.
`E.
`E.
`Z/X/X/Z72
`st it
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`MICRON 1033
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`U.S. Patent
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`May 5, 1992
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`Sheet 1 of 2
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`5,110,388
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`2
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`l
`N. . . . .
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`F G3
`SNNNN-A
`. . . . .N-
`2
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`F G.4
`Al
`A2
`A3
`N. S. Š. Š
`G. G. E.
`Z/X/X/Z72
`3
`32
`33
`" " -
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`MICRON 1033
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`U.S. Patent
`
`May 5, 1992
`
`Sheet 2 of 2
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`5,110,388
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`A3
`A2
`Al
`NS NN NS NS N
`N- f'
`31
`32
`33
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`F G8
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`MICRON 1033
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`

`1
`
`METHOD OF DICING AND BONDING
`SEMCONDUCTOR CHIPS USING A
`PHOTOCURABLE AND HEAT CURABLE
`ADHES WETAPE
`
`O
`
`5
`
`20
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`5, 10,388
`2
`actinic radiation curability and heat curability, which
`can be used as a dicing tape in the dicing step and which
`can provide an adhesive in the mounting step.
`SUMMARY OF THE INVENTION
`In accordance with one aspect of the invention there
`is provided an adhesive tape comprising an energy
`beam transmittable base sheet having a surface tension
`of not more than 40 dyne/cm and an adhesive layer
`formed on one surface of said base sheet, said adhesive
`layer comprising a (meth)acrylate polymer, an epoxy
`resin, a photopolymerizable low molecular weight com
`pound, a heat activatable potential curing agent for said
`epoxy resin and a photopolymerization initiator for said
`photopolymerizable low molecular weight compound.
`In accordance with another aspect of the invention
`there is provided a method for using the above-men
`tioned adhesive tape, which method comprises the steps
`of adhering a semiconductor wafer to said adhesive
`tape, dicing said wafer into chips together with the
`adhesive layer of said adhesive tape, irradiating the
`adhesive layer of said tape with an energy beam, pick
`ing up the chips together with pieces of the diced adhe
`sive layer adhered thereto from said base sheet, placing
`the chips on a lead frame so that the respective pieces of
`the adhesive layer may come in contact with said lead
`frame, and causing the pieces of the diced adhesive
`layer to again develop tackiness by heating thereby
`securely mounting the chips on said lead frame.
`In the method according to the invention, the adhe
`sive tape according to the invention serves as a dicing
`tape for holding the wafer in position during the dicing
`step. Each piece of the diced and cured adhesive layer,
`that is attached to each chip and capable of being tacki
`fied by heating, provides an adhesive for securely
`mounting the chip on the lead frame in the die-bonding
`step.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic cross-sectional view of an adhe
`sive tape according to the invention;
`FIGS. 2 to 7 are illustrations showing states of the
`adhesive tape of FIG. 1 in various steps of a wafer
`processing technique in which it is used; and
`FIG. 8 is a cross-sectional view of a modification of
`the adhesive tape of FIG. 1.
`DETALED DESCRIPTION OF THE
`INVENTION
`The adhesive tape and use thereof according to the
`invention will now be described in detail with reference
`to the accompanying drawings.
`As schematically shown in FIG. 1, the adhesive tape
`1 according to the invention comprises a base sheet 2
`and an adhesive layer 3 formed on one surface of the
`base sheet 2. Before use of the adhesive tape it is prefer
`able to tentatively apply a strippable release sheet (not
`shown) to the adhesive layer 3 for protection thereof.
`It is desirable that the adhesion strength between the
`base sheet 2 and adhesive layer 3 is initially high and can
`be reduced by irradiation to a level sufficiently lower
`than that between the adhesive layer and a semiconduc
`tor wafer. For this purpose the base sheet 2 should have
`a surface tension not more than 40 dyne/cm, preferably
`not more than 38 dyne/cm. Further, suitable as the base
`sheet are materials which are low in electrical conduc
`tivity and excellent in water resistance as well as in heat
`resistance. From these viewpoints, synthetic resin films
`
`This application is a division of Ser. No. 07/380,548
`filed Jul. 14, 1989.
`FIELD OF THE INVENTION
`The present invention relates to a novel adhesive tape
`and use thereof. More particularly, it relates to an adhe
`sive tape suitable for use in dicing a semiconductor
`wafer into chips and die-bonding the chips on a lead
`frame, and to use of such an adhesive tape.
`BACKGROUND OF THE INVENTION
`Wafers of semiconductor material such as silicon and
`gallium-arsenic having formed thereon integrated cir
`cuits have a relatively large diameter. In the production
`of integrated circuits (IC), such a wafer is adhered to an
`adhesive tape sometimes called a dicing tape, diced into
`chips (IC chips), which are then released (picked up)
`from the dicing tape, and adhered to (mounted on) a
`lead frame by means of an adhesive such as an epoxy
`es.
`For dicing tapes suitable for use in such a wafer pro
`cessing technique, it is required that they should exhibit
`a strong adhesion to the semiconductor wafer in the
`step of dicing the wafer into IC chips on the one hand,
`while they should also have such a reduced adhesion to
`the IC chips in the step of picking up the IC chips so
`that the IC chips may be readily released without carry
`ing adhesive residues from the dicing tapes. Thus, in
`prior art dicing tapes, adhesive and releasing properties.
`which are conflicting, are required, and use of a dicing
`tape whose adhesive and releasing properties are not
`well balanced in wafer processing invites such a prob
`len that the dicing and/or picking up steps of the pro
`cess cannot be smoothly carried out. In particular,
`when a prior art dicing tape is used in wafer processing,
`a part of the adhesive of the dicing tape is transferred to
`the picked up 1C chips and adversely affects the charac
`teristics of the resulting C. Accordingly, it has been
`necessary to remove the undesirable residual adhesive
`from the IC chips before they are mounted on a lead
`frame. While complete removal of the residual adhesive
`is difficult, the step of removing the adhesive not only
`makes the processing complicated, but also invites a
`problem of environmental pollution if an organic sol
`SO
`vent is used, for the removal of the residual adhesive.
`Furthermore, a separate adhesive such as an epoxy
`resin has been used for mounting the IC chips on a lead
`frame, as described in Japanese Patent Laid-open Publi
`cation No. 60-198,757. The use of a separate adhesive
`involves another problem such that unceasing applica
`tion of appropriate amounts of the adhesive is techni
`cally very difficult, which results that in a case of a very
`small IC chip in the applied adhesive frequently bulging
`out of the chip, whereas in a case of a relatively large IC
`chip the amount of the applied adhesive tends to be too
`small to provide a desired adhesion.
`OBJECT OF THE INVENTION
`The invention intends to solve the above-discussed
`problems associated with the prior art and an object of
`the invention is to provide an adhesive tape suitable for
`use in processing semiconductor wafers which has both
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`a polycarboxylic acid such as terephthalic acid, iso
`are particularly preferred. As will be stated later, the
`phthalic acid and tetrahydrophthalic acid: N,N-diglyci
`adhesive tape according to the invention, when used, is
`dyl and N-alkyl-N-glycidyl compounds of an aromatic
`irradiated with an energy beam such as an electron
`amine such as aniline isocyanurate; and alicyclic epox
`beam or ultraviolet ray. When it is to be irradiated with
`ides derived from an alicyclic olefin by oxidation of its
`an ultraviolet ray, it must be light transmit table, but it is 5
`olefinic double bond or bonds, such as vinylcyclohex
`not required to be light transmittable when it is to be
`ene diepoxide. 3,4-epoxycyclohexylmethyl-3,4-dicy
`irradiated with an electron beam. Practically, suitable as
`clohexane carboxylate and 2-(3,4-epoxy)cyclohexyl
`the base sheet 2 are films of such synthetic resins as
`5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane. The epox
`polyester, polyethylene, polypropylene, polybutene,
`ide compounds illustrated above may be used alone or
`polybutadiene, vinyl chloride ionomer, ethylene-netha- 10
`in combination. Of these, diglycidyl ethers of a bisphe
`crylic acid copolymer, vinyl chloride-urethane copoly
`nol are particularly preferred. As such preferred epoxy
`mer as well as cross-linked films of such resins. The
`resin those which are commercially available are "Epi
`films may or may not be treated with a silicone.
`kote' 828 having a molecular weight of 380, “Epikote"
`The base sheet 2 may be either of a single layer or
`834 having a molecular weight of 470, "Epikote" 1001
`laminated. The thickness of the base sheet is normally 15
`having a molecular weight of 900, "Epikote" 1002 hav
`from 25 to 200 um.
`ing a molecular weight of 1060, "Epikote" 1055 having
`The adhesive layer 3 of the adhesive tape according
`a molecular weight of 1350 and "Epikote" 1007"having
`to the invention comprises a (meth)acrylate polymer, an
`a molecular weight of 2900.
`epoxy resin, a photopolymerizable low molecular
`The epoxy resin is used in the adhesive composition
`weight compound, a heat activatable potential curing 20
`for forming the adhesive layer 3 in an amount of nor
`agent for the epoxy resin and a photopolymerization
`mally from 5 to 2000 parts by weight, preferably from
`initiator for the photopolymerizable low molecular
`100 to 1000 parts by weight, per 100 parts by weight of
`weight compound.
`the (meth)acrylate polymer.
`By the term "(meth)acrylate polymer" used herein is
`The photopolymerizable low molecular weight com
`meant polymers primarily (at least 50 mol %) compris- 25
`pound which can be used herein is a compound having
`ing structural units derived from at least one (meth)a-
`crylate, i.e. acrylate or methacrylate. Examples of the
`at least one carbon-carbon double bond which is cross
`linkable by irradiation with an energy beam such as an
`suitable (meth)acrylate include, for example, glycidyl
`ultraviolet ray and electron beam, and has a molecular
`acrylate and methacrylate as well as alkyl and hydroxy
`weight of, normally from 100 to 30,000, preferably from
`alkyl (meth)acrylates. in which the alkyl moiety has 30
`300 to 10,000. Examples of preferred photopolymeriz
`from 1 to 14 carbon atoms, such as methyl, ethyl and
`able oligomers are those having functional groups such
`butyl acrylates and methacrylates, and 2-hydroxyethyl
`as hydroxy and carboxy, and include, for example, ure
`acrylate and methacrylate.
`thane acrylate, epoxy acrylate, polyester acrylate, poly
`The (meth)acrylate polymer which can be used
`ether acrylate, oligomer of (meth)acrylic acid and
`herein may be a homopolymer of a (meth)acrylate, or it 35
`oligomer of itaconic acid. Of these, epoxy acrylate and
`may be a copolymer of at least two (meth)acrylates.
`urethane acrylate are particularly preferred.
`Alternatively, it may be a copolymer of at least one
`The photopolymerizable low molecular weight con
`(meth)acrylate and at least one comonomer copolymer
`pound is used in the adhesive composition for forming
`izable there with containing at least 50 mol % of units
`the adhesive layer 3 in an amount of normally from 10
`derived from said at least one (meth)acrylate. Examples 40
`to 1000 parts by weight, preferably from 50 to 600 parts
`of the comonomer include, for example, acrylic and
`by weight, per 100 parts by weight of the (meth)acry
`methacrylic acid, acrylonitrile, methacrylonitrile, vinyl
`late polymer.
`acetate, vinylpyrrollidones and vinyl group-containing
`The heat activatable potential curing agent for the
`siloxanes. Particularly preferred (meth)acrylate poly
`epoxy resin is a compound having or potentially having
`mers which can be used herein are copolymers of at 45
`at least two active hydrogen atoms which are inactive
`least one alkyl (meth)acrylate, in which the alkyl moi
`at ambient temperature but are activated, when heated,
`ety has from 1 to 8 carbon atoms and at least one glyci
`to react with the epoxy resin thereby effecting or pro
`dyl (meth)acrylate containing up to 80 mol %, in partic
`moting curing of the epoxy resin. As such a heat activat
`ular from 5 to 50 mol % of units derived from said at
`able potential curing agent for the epoxy resin, use can
`least one glycidyl (meth)acrylate, and copolymers of at 50
`be made of various onium salts, in particular aliphatic
`least one alkyl (meth)acrylate, in which the alkyl moi
`and aromatic sulfonium salts, and other high melting
`ety has from 1 to 8 carbon atoms and at least one (meth
`active hydrogen-containing compounds, alone or in
`Dacrylic acid containing up to 50 mol %, in particular
`combination. Among others, aliphatic sulfonium salts
`from 5 to 20 mol % of units derived from said at least
`are preferred.
`55
`one (meth)acrylic acid.
`The amount of the heat activatable potential curing
`The alkyl (meth)acrylate polymer used herein is sub
`agent used in the adhesive composition for forming the
`stantially free from a C-C double bond, and normally
`adhesive layer 3 may practically be within the range
`has a molecular weight of from about 40,000 to about
`from 0.1 to 50 parts by weight, preferably from 1 to 10
`1,500,000, preferably from about 100,000 to 1,000.000.
`parts by weight, per 100 parts by weight of the epoxy
`The epoxy resin which can be used herein is an or- 60
`resin, irrespective of the presence of any epoxy groups
`ganic material having an average of at least 1.8 vicinal
`in the (meth)acrylate polymer and/or photopolymeriz
`epoxy groups per molecule, and normally has an aver
`able low molecular weight compound.
`age molecular weight of from 100 to 1000. Examples of
`In addition to the heat activatable potential curing
`the epoxy resin include, for example, glycidyl ethers of
`agent for epoxide functionality, a heat curing agent such
`a phenol such as Bisphenol A, Bisphenol F, resorcinol, 65
`as a polyisocyanate compound may be incorporated in
`phenol novolac and resorcinol novolac; glycidyl ethers
`the adhesive composition for the purpose of modifying
`of a polyhydric alcohol such as butanediol, polyethyl
`adhesive properties of the adhesive layer. When used,
`ene glycol and polypropylene glycol; glycidyl esters of
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`Where a strippable release sheet is provided, it is first
`the amount of the heat curing agent may be normally
`removed, and the adhesive tape 1 is placed, turning the
`from 0.1 to 30 parts by weight, and preferably from 5 to
`adhesive layer 3 upward (FIG. 1).
`20 parts by weight, based on 100 parts by weight of the
`(meth)acrylate polymer.
`On the face side of the adhesive layer 3 is applied a
`semiconductor wafer A to be processed (FIG. 2).
`The adhesive composition for forming the adhesive
`layer 3 further comprises a photopolymerization initia
`In this state the wafer A is diced together with the
`adhesive layer 3 of the adhesive tape 1 into chips A1,
`tor for the photopolymerizable low molecular weight
`compound. Examples of the photopolymerization initia
`A2. A3 and so on by a suitable dicing means such as a
`tor include, for example, benzophenone, acetophenone,
`dicing saw (FIG. 3). In this step, the wafer A is com
`pletely diced into chips. Whereas the adhesive layer 3 is
`benzoin, benzoin alkyl ether, benzil and benzil dimeth
`substantially diced. In other words, at least 50%, prefer
`ylketal, alone or in combination. Of these, alpha-sub
`ably 100% of the whole thickness of the adhesive layer
`stituted acetophenones are preferred.
`is cut. The deeper the cut, the better.
`The photopolymerization initiator is used in the adhe
`The base sheet 2 is then expanded in two perpendicu
`sive composition for forming the adhesive layer in an
`larly intersecting directions within the plane of the
`amount of normally from 0.1 to 10 parts by weight,
`sheet to facilitate the subsequent picking up operation
`preferably from 1 to 5 parts by weight, per 100 parts by
`(FIG. 4). While the illustrated method involves a step of
`weight of the photopolymerizable low molecular
`expanding, this step is not always necessary. In a case
`weight compound.
`wherein this step is carried out, the base sheet 2 should
`Besides the above-mentioned components, the adhe
`naturally have extensibility in machine and transverse
`sive layer 3 may be further incorporated with a leuco
`20
`dye, a light scattering inorganic compound, an expand
`directions. However, base sheets having no extensibility
`may also be used where no expansion treatment is car
`ing agent and an antistatic agent.
`Examples of the leuco dye include, for example, 3-N-
`ried out.
`(p-tolylamino)-7-anilinofluoran and 4,4',4'-trisdime
`Before the chips are picked up, the adhesive layer 3 is
`thylaminotriphenylmethane. The amount of the leuco
`irradiated with energy beam B to polymerize or cure
`the photopolymerizable compound contained in the
`dye, when used, is normally from 0.01 to 10 parts by
`weight per 100 parts by weight of the (meth)acrylate
`adhesive layer 3 from the side of the base sheet 2 on
`polymer.
`which the adhesive layer 3 is not formed (FIG. 4). As
`As the light scattering agent, suitable is a fine particu
`the energy beam ultraviolet ray having a center wave
`length of about 365 nm is preferred, and upon irradia
`late inorganic compound such as silica and alumina
`having a particle size of from 1 to 100 m, preferably
`tion with such ultraviolet ray intensity of radiation and
`irradiation time are preferably set within the ranges of
`from 1 to 20 m. The amount of the light scattering
`inorganic compound, when used, is normally from 0.1
`from 20 to 500 mW/cm2 and from 0.1 to 150 seconds,
`respectively.
`to 10 parts by weight per 100 parts by weight of the
`(meth)acrylate polymer.
`While the dicing step is carried out prior to the irradi
`As the expanding agent, use can be made of higher
`ation step in the illustrated method, the irradiation may
`be effected prior to the dicing, in particular where no
`fatty acids and derivatives thereof, silicone compounds
`and polyol compounds. The amount of the expanding
`expansion is carried out. Furthermore, while the irradi
`agent, when used, is normally from 0.1 to 10 parts by
`ation in the illustrated method is carried out before the
`weight per 100 parts by weight of the (neth)acrylate
`chips come to a pick-up station where the pick-up oper
`polymer.
`ation is carried out, the irradiation may be effected at
`the pick-up station, in particular where the expansion is
`Suitable as the antistatic agent are carbon black and
`anionic and cationic surfactants. The amount of the
`carried out.
`antistatic agent, when used, is normally from 0.05 to 10
`When the adhesive used herein is cured by irradiation
`parts by weight per 100 parts by weight of the (meth)a-
`with an energy beam, its adhesion strength to the wafer
`crylate polymer.
`is increased well above a level of its adhesion strength
`If desired, electrical conductivity may be imparted to
`to the base sheet. This is believed to be due to the pres
`the the adhesive layer 3 by incorporating therein an
`ence of the epoxy resin in the adhesive.
`Next, in a pick-up station, the wafer chips A1, A2, A3
`electrically conductive substance such as gold, silver,
`and so on are successively pushed up by a pushing rod
`copper, nickel, aluminum, stainless steel and carbon.
`Such an electrically conductive substance is preferably
`(not shown), picked up from the base sheet 2 by a suit
`used in an amount of from 10 to 400 parts by weight
`able means, such as a vacuum collet 6, as shown in FIG.
`based on 100 parts by weight of the (meth)acrylate
`5, and collected in a wafer box (not shown). Since the
`polymer.
`cured adhesive has a greater adhesion strength to the
`The adhesive tape according to the invention can be
`wafer than to the base sheet 1, the wafer chips can
`readily be released together with the cured adhesive
`prepared by coating the base sheet 2 on one surface
`thereof with a suitable adhesive composition for form
`attached thereto from the base sheet 1. FIG. 6 depicts
`the wafer chip A1 picked up by the vacuum collet 6. As
`ing the desired adhesive layer 3 by means of a gravure
`seen from FIG. 6, the picked up wafer chip A carries a
`coater or a bar coater. If desired, necessary amounts of
`necessary components for forming the adhesive layer 3
`piece 31 of the diced and irradiated adhesive layer 3.
`60
`may be dissolved or dispersed in an appropriate solvent,
`Since the cured adhesive attached to the wafer chips is
`and the resulting composition may applied on the base
`no longer sticky, the wafer chips collected in the wafer
`box do not stick to each other.
`sheet 2.
`The thickness of the adhesive layer 3 is normally
`In the illustrated method the energy beam irradiation
`from 3 to 100 um, and preferably from 10 to 60 m.
`is effected at once, but it may be done partially in sev
`The method for using the adhesive tape 1 of FIG. 1 in
`eral times. For instance, especially, in a case wherein
`the expansion of the base sheet has been carried out,
`wafer processing will now be described. Reference
`only the portion of the base sheet 1 corresponding to
`numbers refer to the accompanying drawings.
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`An adhesive composition comprising the above
`each of the wafer chips Ai, A2. As and so on may be
`indicated components in indicated amounts was applied
`irradiated from the back side of the base sheet 1 by
`on a polyethylene film having a surface tension of 32
`means of an irradiating tube. pushed up by the same
`dyne/cm and a thickness of 100 un, and dried under
`tube and picked up by the vacuum collet so that the
`heating at 100 C. for 1 minute to prepare an adhesive
`irradiation may be carried out at the pick-up station.
`tape having an adhesive layer of a thickness of 30 um.
`The wafer chips A. A. As and so on are then placed
`A silicon wafer was applied onto the adhesive layer
`on a lead frame 7 by means of a die-bonder (not shown)
`surface of the adhesive tape so prepared. The adhesive
`so that the respective pieces 31, 3, 33 and so on of the
`tape adhered to the silicon wafer at an adhesion strength
`adhesive layer may come in contact with the lead
`frame, and heated at a temperature of normally from
`of 360 g/25 mm. as measured in accordance with JIS Z
`0237. The adhesive layer was then irradiated with 200
`100 to 300° C., preferably from 150' to 250 C., for a
`mW/cm of an ultraviolet ray for 2 seconds using a 80
`period of normally from 1 to 120 minutes, preferably
`W/cm high pressure mercury lamp. By this irradiation
`from 5 to 60 minutes so as to cause the cured adhesive
`the adhesion strength between the adhesive layer and
`contained in the pieces of the diced adhesive layer to
`again develop tackiness (FIG. 7). By this heating the
`the silicon wafer increased to 900 g/25 mm, while the
`adhesion strength between the adhesive layer and the
`adhesion strength of the adhesive layer to the wafer
`polyethylene base sheet after the irradiation was 60
`chip is increased to at least 1000 g/25 mm, and at the
`g/25 mm.
`same time the wafer chips are firmly adhered to the lead
`The adhesive tape was employed in processing a
`frame 7 at an adhesion strength of substantially the same
`20
`silicon wafer as follows. A silicon wafer of the same
`level. Thus, the wafer chips can be securely mounted on
`quality having a diameter of 5 inches was applied onto
`the lead frame 7.
`the adhesive layer of the tape, and fully cut together
`In accordance with still another aspect of the inven
`with the adhesive layer by means of a dicing saw sup
`tion there is provided an adhesive composition compris
`ing a (meth)acrylate polymer having at least 50 mol %
`plied by DISCO Co., Ltd. at a cutting rate of 50
`25
`mm/sec into 5 mm square IC chips. The adhesive layer
`of units derived from at least one (meth)acrylate, from 5
`to 2000 parts by weight, based on 100 parts by weight of
`was irradiated through the polyethylene base sheet with
`the (meth)acrylate polymer, of an epoxy resin having a
`the above-mentioned ultraviolet ray for 2 seconds. The
`IC chips were picked up and then directly placed on a
`molecular weight of from 100 to 10000, from 10 to 1000
`parts by weight, based on 100 parts by weight of the
`lead frame by means of a die-bonder so that pieces of the
`(meth)acrylate polymer, of a photopolymerizable low
`cured adhesive layer attached to the chips may come in
`molecular weight compound having a molecular
`contact with the lead frame. The chips were then
`weight of from 100 to 30,000, a heat activatable poten
`heated at a temperature of 170° C. for a period of 30
`tial curing agent for said epoxy resin and a photopolym
`minutes whereby they could be securely mounted on
`erization initiator for said photopolymerizable low mo
`the lead frame.
`lecular weight compound.
`35
`The adhesive composition according to the invention
`provides an adhesive layer which is curable by irradia
`tion with an energy beam and the so cured adhesive
`layer is capable of developing tackiness again by heat
`ing.
`The invention will now be further described by the
`following examples, wherein parts are by weight unless
`otherwise specified.
`EXAMPLE 1
`
`5
`
`10
`
`5
`
`45
`
`(Methacrylate polymer having a solid
`content of 35% by weight and
`containing a copolymer of methyl acrylate
`and glycidyl methacrylae, the copolymer
`containing 20 mol % methyl acrylate
`and having a molecular weight of about
`300,000
`Bisphenol diglycidyl ether based
`epoxy resin having a number average
`molecular weight of 500 (supplied by
`YUKA SHELLEPOXY K. K. under a trade
`name of Epikote 834)
`Photopolymerizable epoxy acrylate
`oligomer having two C-C double bonds
`and a molecular weight of 730 as
`measured by GPC using polystyrene
`as standard (supplied by SHIN
`NAKAMURA CHEMICA Co. Ltd. under a
`Tade name of NK-ester EA-800)
`Heat activatable potential curing
`gent for epoxy resins: aliphatic
`Sulfonium salt (supplied by ASAH. DENKA
`KOGYO K. K. under a trade name of CP-66)
`Photopolymerization initiator:
`2.2-dimethoxy-2-phenylacetophenone
`
`100 parts
`(solid basis)
`
`600 parts
`
`100 parts
`
`50
`
`55
`
`18 parts
`
`65
`
`5 parts
`
`EXAMPLE 2
`
`(Meth)acrylate polymer having a solid
`content of 35% by weight and containing
`a copolymer of butyl acrylate and
`acrylic acid, the copolymer containing
`80 mol % of butyl acrylate and having
`a molecular weight of about 500,000
`Bisphenol diglycidyl ether based
`epoxy resin having a solid content of
`30% by weight and a number average
`molecular weight of 900 (supplied by
`YUKA SHELLEPOXY K. K. under a trade
`name of Epikote 1001)
`Photopolymerizable urethane acrylate
`oligomer having two C-C double bonds
`and a molecular weight of 5,000 as
`measured by GPC using polystyrene
`as standard (supplied by DANICH ISEKA
`COLOR & MFG. CO.,LTD. under a trade
`name of 14-33)
`Heat activatable potential curing
`agent for epoxy resins: aliphatic
`sulfonium salt (supplied by ASAHI DENKA
`KOGYO K. K. under a trade name of CP-66)
`Photopolymerization initiator:
`2.2-dimethoxy-2-phenylacetophenone
`Heat curing agent: aromatic
`polyisocyanate (supplied by TOYO INK
`MFG. CO. LTD. under a trade name of
`BHS-8315)
`Electrically conductive filler:
`particulate nickel having a particle
`size of 5 um
`
`100 parts
`(solid basis)
`
`400 parts
`(solid basis)
`
`70 parts
`
`8 parts
`
`5 parts
`5 parts
`
`750 parts
`
`An adhesive composition comprising the above
`indicated components in indicated amounts was applied
`on a polypropylene film having a surface tension of 35
`
`MICRON 1033
`
`

`

`O
`
`15
`
`5,110,388
`10
`9
`heating, thereby securely mounting the chips on said
`dyne/cm and a thickness of 60 un, and dried under
`heating at 100 C. for 1 minute to prepare an adhesive
`lead frame.
`Thus, according to another modification of the inven
`tape having an adhesive layer of a thickness of 30 pum.
`tion there is provided a method for using an adhesive
`A silicon wafer was applied onto the adhesive layer
`tape comprising an adhesive layer composed of a (meth
`surface of the adhesive tape so prepared. The adhesive
`)acrylate polymer, an epoxy resin, a photopolymeriz
`tape adhered to the silicon wafer at an adhesion strength
`able low molecular weight compound, a heat activat
`of 150 g/25 mm. The adhesive layer was then irradiated
`able potential curing agent for said epoxy resin and a
`with an ultraviolet ray as in Example 1. By this irradia
`photopolymerization initiator for said photopolymeriz
`tion the adhesion strength between the adhesive layer
`able low molecular weight compound, said method
`and the silicon wafer increased to 500 g/25 mm, while
`the adhesion strength between the adhesive layer and
`comprising the steps of adhering a semiconductor wafer
`the polypropylene base sheet after the irradiation was
`to said adhesive tape formed on a release sheet, irradiat
`40 g/25 mm.
`ing the adhesive layer with an energy beam, dicing said
`The adhesive tape was employed in processing a
`wafer into chips together with the adhesive layer, pick
`silicon wa?er in the manner as described in Example 1.
`ing up the chips together with pieces of the diced adhe
`Good results were obtained as in Example 1.
`sive layer adhered thereto from said release sheet, plac
`ing the chips together with pieces of the diced adhesive
`EFFECT OF THE INVENTION
`layer adhered thereto on a lead frame so that the respec
`The adhesive layer of the adhesive tape according to
`tive pieces of the adhesive layer may come in contact
`the invention can be cured by irradiation with an energy
`20
`with said lead frame, and causing the pieces of the diced
`beam, and the so cured adhesive layer is capable of
`adhesive layer to again develop tackiness by heating.
`developing tackiness again by heating. Furthermore,
`thereby securely mounting the chips on said lead frame.
`the adhesive tape has such a uniqu