Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2000-09-28
2003-10-14
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S3550CN, C428S447000, C428S446000, C528S021000, C528S038000, C528S026000, C528S028000, C525S477000
Reexamination Certificate
active
06632523
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an adhesive composition useful for bonding articles to substrates at relatively low temperatures, especially in microelectronic applications. In particular, it relates to a solution in an organic solvent of a polyimide, an epoxy resin, and a cyanate.
A tape having an adhesive coating on both sides of a carrier film can be used to bond articles, such as microelectronic chips, to substrates, such as circuit boards. The adhesive on the tape should be non-tacky at room temperature so that the tape can be rolled up and easily unrolled. (If the tape is tacky, it must be covered with a release liner, which requires additional equipment to remove in an automated assembly line.) To maximize throughput, the tape should bond to the substrate in a tenth of a second or less at about 120 to about 160° C. and, to prevent the bonded tape from dislodging in hot environments, it should melt at a temperature over about 100° C. At the same time, the adhesive should maintain a strong bond at about 220 to 240° C. so that the bond does not break during subsequent heating operations, such as soldering. It is difficult to make an adhesive composition that meets all of these exacting requirements.
SUMMARY OF THE INVENTION
We have discovered an adhesive composition that is non-tacky at room temperature, will bond in a tenth of a second, melts at a temperature over 100° C., and will retain a strong bond at temperatures from about 220 to about 240° C. The adhesive composition is soluble in organic solvents, so it can be applied as a solution and the solvent can be evaporated to form a coating.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The adhesive composition is prepared as a solution in an organic solvent of a polyimide, an epoxy resin, and a cyanate.
The Polyimide
The polyimide can be prepared by reacting an aromatic dianhydride with a diamine. Generally, stoichiometric quantities of diamine and dianhydride are used to obtain the highest molecular weight, but the equivalent ratio of dianhydride to diamine can range from 1:2 to 2:1.
Examples of suitable aromatic dianhydrides include:
1,2,5,6-naphthalene tetracarboxylic dianhydride;
1,4,5,8-naphthalene tetracarboxylic dianhydride;
2,3,6,7-naphthalene tetracarboxylic dianhydride;
2-(3′,4′-dicarboxyphenyl) 5,6-dicarboxybenzimidazole dianhydride;
2-(3′,4′-dicarboxyphenyl) 5,6-dicarboxybenzoxazole dianhydride;
2-(3′,4′-dicarboxyphenyl) 5,6-dicarboxybenzothiazole dianhydride;
2,2′,3,3′-benzophenone tetracarboxylic dianhydride;
2,3,3′,4′-benzophenone tetracarboxylic dianhydride;
3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA);
2,2′,3,3′-biphenyl tetracarboxylic dianhydride;
2,3,3′,4′-biphenyl tetracarboxylic dianhydride;
3,3′,4,4′-biphenyl tetracarboxylic dianhydride(BPDA);
bicyclo-[2,2,2]-octen-(7)-2,3,5,6-tetracarboxylic-2,3,5,6-dianhydride;
thio-diphthalic anhydride;
bis (3,4-dicarboxyphenyl) sulfone dianhydride;
bis (3,4-dicarboxyphenyl) sulfoxide dianhydride;
bis (3,4-dicarboxyphenyl oxadiazole-1,3,4) paraphenylene dianhydride;
bis (3,4-dicarboxyphenyl) 2,5-oxadiazole 1,3,4-dianhydride;
bis 2,5-(3′,4′-dicarboxydiphenylether) 1,3,4oxadiazole dianhydride;
bis (3,4-dicarboxyphenyl) ether dianhydride or 4,4′-oxydiphthalicanhydride (ODPA);
bis (3,4-dicarboxyphenyl) thioether dianhydride;
bisphenol A dianhydride (BPADA);
bisphenol S dianhydride;
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride or 5,5-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] bis-1,3-isobenzofurandione) (6FDA); hydroquinone bisether dianhydride;
bis (3,4-dicarboxyphenyl) methane dianhydride;
cyclopentadienyl tetracarboxylic acid dianhydride;
cyclopentane tetracarboxylic dianhydride;
ethylene tetracarboxylic acid dianhydride;
perylene 3,4,9,10-tetracarboxylic dianhydride;
pyromellitic dianhydride (PMDA);
tetrahydrofuran tetracarboxylic dianhydride;
resorcinol dianhydride;
ethyleneglycol bis(anhydrotrimellitate); and
5-(2,5-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride.
The dianhydrides can be used in their tetraacid form or as mono, di, tri, or tetra esters of the tetra acid, but the dianhydride form is preferred because it is more reactive. The preferred dianhydride is ODPA because it has been found to give excellent properties. Mixtures of dianhydrides are also contemplated.
The diamine used in preparing the polyimide is preferably aromatic as aromatic diamines give the best properties. Examples of aromatic diamines include:
m- and p-phenylenediamine;
2,4-diaminotoluene (TDA);
2,5- and 2,6-diaminotoluene;
p- and m-xylenediamine;
4,4′-diaminobiphenyl;
4,4′-diaminodiphenyl ether or 4,4′-oxydianiline; (ODA)
3,4′-oxydianiline;
4,4′-diaminobenzophenone;
3,3′,3,4′, or 4,4-diaminophenyl sulfone or m,m-, m,p- or p,p- sulfone dianiline;
2,2-bis[4-(4-aminophenoxy)phenyl] sulfone;
2,2-bis[4-(3-aminophenoxy)phenyl] sulfone;
4,4′-diaminodiphenyl sulfide;
3,3′-diaminodiphenyl sulfone (APS);
3,3′ or 4,4′-diaminodiphenylmethane or m,m- or p,p-methylene dianiline;
3,3′-dimethylbenzidine;
2,2′-bis[(4-aminophenyl)-1,4-diisopropyl]benzene or 4,4′-isopropylidenedianiline or bisaniline P(BAP);
2,2′-bis[(4-aminophenyl)-1,3-diisopropyl]benzene or 3,3′-isopropylidenedianiline or bisaniline M;
methylene dianiline;
1,4-bis(4-aminophenoxy)benzene;
1,3-bis(4-aminophenoxy)benzene;
1,3-bis(3-aminophenoxy)benzene (APB);
4,4′-bis(4-aminophenoxy)biphenyl;
2,4-diamino-5-chlorotoluene;
2,4-diamino-6-chlorotoluene;
2,2-bis-[4(4-aminophenoxy)phenyl] propane (BAPP);
trifluoromethyl-2,4-diaminobenzene;
trifluoromethyl-3,5-diaminobenzene;
2,2-bis(4-aminophenyl)-hexafluoropropane (6F diamine);
2,2-bis(4-phenoxy aniline) isopropylidene;
2,4,6-trimethyl-1,3-diaminobenzene;
4,4diamino-5,5′-trifluoromethyl diphenyloxide;
3,3′-diamino-5,5′-trifluoromethyl diphenyloxide;
4,4′-trifluoromethyl-2,2′-diamino biphenyl;
2,5-dimethyl-1,4-phenylenediamine (DPD);
2,4,6-trimethyl-1,3-diaminobenzene;
diaminoanthraquinone;
4,4-oxybis[(2-trifluoromethyl)benzeneamine] (1,2,4-OBABTF);
4,4′-oxybis[(3-trifluoromethyl)benzeneamine];
4,4′-thiobis[(2-trifluoromethyl)benzeneamine];
4,4′-thiobis[(3-trifluoromethyl)benzeneamine];
4,4′-sulfoxylbis[(2-trifluoromethyl)benzeneamine];
4,4′-sulfoxylbis[(3-trifluoromethyl)benzeneamine];
4,4′-ketobis[(2-trifluoromethyl)benzeneamine];
4,4′-[(2,2,2-trifluoromethyl-1-(trifluoromethyl)-ethylidine)bis(3-trifluoromethyl)benzeneamine]; and
4,4′-dimethylsilylbis[(3-trifluoromethyl)benzeneamine].
The preferred aromatic diamine is APB as it gives excellent properties. Mixtures of aromatic diamines are also contemplated.
The polyimide is preferably a polyimidesiloxane because polyimidesiloxanes have good processibility and low water absorption. To prepare a polyimidesiloxane, a diamine or dianhydride that contains siloxane groups is included as part of the diamine or the dianhydride. A polyimidesiloxane can be made from about 1 to about 80 wt % siloxane-containing monomers and about 20 to about 99 wt % monomers that do not contain siloxane. Preferably, it is made from about 20 to about 60 wt % siloxane-containing monomers and about 40 to about 80 wt % monomers that do not contain siloxane. The siloxane-containing monomer can be either aromatic or non-aromatic, but non-aromatic monomers are preferred as they are more readily available. Siloxane diamines are preferred to siloxane dianhydrides as they are more readily available. Examples of siloxane diamines that can be used have the formula:
Examples of siloxane dianhydrides that can be used have the formula:
where R
1
, R
2
, and R
3
are mono, di, and triradicals, respectively, each independently selected from a substituted
Neff Jerrine L.
Rosenfeld Jerrold C.
Baker & McKenzie
Dawson Robert
Flaim John G.
Keehan Christopher
O'Brien Kevin M.
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