Laminates

Details Laminates Laminates

1997-10-22

2001-10-16

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Composite

Of metal

C360S100100, C428S463000, C428S473500, C430S069000, C174S258000

Reexamination Certificate

active

06303230

ABSTRACT:

FIELD OF TECHNOLOGY
This invention relates to laminates which serve as materials suitable for HDD (hard disk drive) suspensions.
BACKGROUND TECHNOLOGY
Partial removal of the insulator on an electric conductor has often been practiced for the purpose of exposing the electric conductor in a terminal. A technique thereby employed is to paste a punched-out insulating film on the electric conductor and pattern the electrically conducting portion. Another technique is to remove the insulator underneath the patterned electric conductor by a special chemical [Japan Kokai Tokkyo Koho No. Sho 52-22071 (1977)] or by laser [Japan Kokai Tokkyo Koho No. Sho 62-22071 (1987)]. The former technique, based on fabrication by punching, poses problems of difficulties in attaining accuracy and also of expenditure for molds. On the other hand, the latter technique requires hazardous chemicals such as strong alkali and costly equipment for generation of laser and plasma and also poses the problem of low productivity.
An HDD (hard disk drive) suspension has been prepared by etching a stainless steel foil and a thin-film magnetic head is mounted on the tip of the suspension and packaged by wire bonding with a gold wire. A general structure of such HDD suspension is described in PETEROTECH, Volume 18, Number 11, page 351.
In recent years, however, active studies directed to smaller size and higher density and capacity of HDD suspensions are under way and the indispensable theme of such studies is low rise of suspensions (sliders). From this viewpoint, the conventional gold wire is an obstacle to low rise and, in addition, its resistance to air flow is detrimental to high-speed manufacture.
To solve the problem in question, an attempt has been made to form patterns of insulating polyimides directly on a stainless steel foil and then form a copper ciurcuit on the polyimides as disclosed in Japan Kokai Tokkyo Koho No. Sho 60-246015 (1985).
A technique such as this, however, still faces difficulties in forming a fine circuit. There are also problems, although latent, such as poor adhesion of polyimides to the substrate stainless steel foil and a long period of time, too long for an operation on an industrial scale, required for alkali etching of polyimide precursors.
An object of this invention is to provide laminates of high reliability and fabrication accuracy and excellent workability which allow the preparation of circuit boards by fabrication of the insulator.
Another object of this invention is to provide laminates of high reliability and fabricability useful for the preparation of HDD suspensions.
DISCLOSURE OF THE INVENTION
Accordingly, this invention relates to laminates which consist of an electric conductor and layers, formed one on top of another, of polyimide precursors and photosensitive resins.
This invention also relates to laminates which consist of a stainless steel foil and layers, formed one on top of another, of polyimide precursors and photosensitive resins and are useful for the preparation of HDD suspensions and, preferably, said polyimide precursors have a main structural unit represented by the following general formula (2)
wherein A is the divalent residue of an aromatic group containing 17 or less carbon atoms, B is —CO—, —SO
2
— or —O— and m is an integer from 0 to 100.
Photosensitive resins may vary in structure, their choice being optional, and they may be either negative-working or positive-working. Photosensitive resins are normally ultraviolet-reactive or electron beam-reactive and they are composed of base oligomers, reactive diluents, photoinitiators, photosensitizers, pigments, polymerization inhibitors and the like. As base oligomers are known epoxy acrylates, urethane acrylates and polyester acrylates.
Ultraviolet-curable acrylic resins are particularly desirable as photosensitive resins because of their resistance to alkali and to penetration of water during etching of a layer of polyimide precursors. Most desirable are acrylic photosensitive resins which can be developed and stripped by acids. Their thickness is preferably 2 to 100 &mgr;m. A film with a thickness of less than 2 &mgr;m lacks strength, though fabrication accuracy is high, and tends to cause problems such as peeling during etching of polyimide precursors. A film with a thickness in excess of 100 &mgr;m, though strong and highly reliable, suffers from loss of fabrication accuracy and increase in cost.
Polyimide precursors are synthesized by treating diamines (or their derivatives) with tetracarboxylic acid dianhydrides (or their derivatives) in a polar solvent at 0 to 200° C. The occurrence of imidation in the course of this reaction is undesirable as it decreases solubility and extends the etching time during patterning.
Polar solvents include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenols, cyclohexanone, dioxane, tetrahydrofuran and diglyme.
Diamines (or their derivatives) include p-phenylenediamine, m-phenylenediamine, 2′-methoxy-4,4′-diaminobenzanilide, 4,4′-diaminodiphenyl ether, diaminotoluene, 4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis(anilino)ethane, diaminodiphenyl sulfone, diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis(p-aminophenyl) propane, 2,2-bis(p-aminophenyl)hexafluoropropane, 1,5-diaminonaphthalen e, diaminobenzotrifluoride, 1,4-bis(p-aminophenoxy) benzene, 1,3-bis(p-aminophenoxy)benzene, 4,4′-(p-aminophenoxy)biphenyl, diaminoanthraquinone, 4,4′-bis(3-aminophenoxyphenyl)diphenyl sulfone, 1,3-bis(anilino)hexafluoropropane, diaminosiloxanes represented by the following general formula
(wherein R
2
and R
4
are divalent organic groups, R
1
and R
3
are monovalent organic groups and p and q are integers greater than 1), 2,2-bis[4-(p-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(3-aminophenoxy) phenyl]hexafluoropropane, 2,2-bis[4-(2-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)-3,5-di(trifluoromethyl)phenyl]hexafluoropropane, p-bis(4-amino-2-trifluoromethylphenoxy)benzene, 4,4′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 4,4′-bis(4-amino-3-trifluoromethylpheno xy)biphenyl, 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl sulfone, 4,4′-bis(4-amino-5-trifluoromethylphenoxy)diphenyl sulfone, 2,2-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]hexafluoropropane, benzidine, 3,3′,5,5′-tetramethylbenzidine, octafluorobenzidine, 3,3′-dimethoxybenzidine, o-tolidine, m-tolidine, 2,2′,5,5′,6,6′-hexafluorotolidine, 4,4″-diaminoterphenyl and 4,4′″-diaminoquaterphenyl or diisocyanates resulting from the reaction of these diamines with phosgene.
Any of these diamines (or their derivatives) may be used and it is desirable that the main components are diamines containing the main structural unit represented by the aforementioned general formula (2), that is, diamines whose A is the divalent residue of an aromatic group with 17 or less carbon atoms. When the main components are diamines with more than 17 carbon atoms, the time for alkali etching of polyimide precursors becomes extremely long, which lowers productivity and makes high-accuracy fabrication difficult. Hence, it is desirable that 80 mol % or more of the diamines are aromatic diamines with 17 or less carbon atoms.
Tetracarboxylic acid anhydrides (or their derivatives) include the following and it is to be understood that, although tetracarboxylic acids are shown as examples, their esters, acid anhydrides, and acid halides can certainly be used; pyromellitic acid, 3,3′,4,4′-biphenyltetracarboxylic acid, 3,3′, 4,4′-benzophenonetetracarboxylic acid, 3, 3′,4,4′-(diphenyl sul

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