Compositions – Electrically conductive or emissive compositions – Free metal containing
Reexamination Certificate
2000-09-11
2003-02-04
Kopec, Mark (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Free metal containing
C156S330000, C525S107000
Reexamination Certificate
active
06514433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a connecting material, in particular, that comprises a thermosetting resin, for bonding and connecting elements, each element having correspondingly confronting electrodes.
DESCRIPTION OF THE RELATED TECHNIQUES
A connecting material constituted of, as a main component, a thermosetting resin has been employed for bonding elements , each element being provided with correspondingly confronting electrodes thereon, with simultaneous attainment of electro-conductive connection of the confronting electrodes with each other. For example, in a liquid crystal display (LCD), such a connection is realized between a layer of indium tin oxide (ITO) on a substrate glass board and a tape carrier package (TCP) or a driver IC. Also, in the assemblage of semiconductors, such as an IC and a LSI, on a printed circuit board, it has been practiced to build up an electrical connection between bear chips of these semiconductors and the circuit board directly using a connecting material. Here, the bonding between the circuit board and these elements to be bonded is performed by holding them in a posture in which the electrodes or terminals disposed on the chips and on the circuit board are in a correspondingly confronting relationship with each other, while interposing the connecting material therebetween, whereupon the connecting material is caused to harden to attain a mechanical firm bonding of them and assured electrical connection between the corresponding electrodes simultaneously.
In such a connecting material, a thermosetting resin has been used as the fundamental component. The connecting material is interposed between the elements to be bonded together, such as a printed circuit board and semiconductor chips, and these elements are held at such a posture that the electrodes or terminals to be electroconductively connected together disposed on them are in a correspondingly confronting relationship with each other, whereupon the elements are heat-pressed onto each other by pressing them together with heating to cause the thermosetting resin to set to thereby attain a firm bonding of them. Here, the mechanical bonding between the elements is provided by the adhesive strength of the resin and the electrical connection between the corresponding electrodes or terminals is attained by a pressed friction contact of them secured by the heat setting of the resin. This electrical connection by frictional press contact between the elements may be attained by direct contact of the electrodes or the terminals with each other or under intermediation with electroconductive particles contained in the connecting material in a dispersed state.
Due to the recent demand in the market for so-called light, thin, short and small articles in the fields represented by portable electronic articles, problems have arisen in that the bonding strength is reduced in the portion bonded with a connecting material, for example, between a semiconductor chip and a substrate circuit board or between a TCP and ITO layer, where the bonded contacting area is reduced. In addition, it has been brought into examination to install devices, such as a driver IC etc., on a flexible printed circuit board (FPC), wherein it is requested to increase the bonding strength (peeling strength) for the connecting material. In particular, films of a polyimide resin are employed practically for a FPC, for which no adequate bonding material nor connecting material exhibiting superior adhesion thereto has hitherto been known.
A technique has been known in general for improving the toughness parameter of an adhesive by rendering the adhesive mass more soft, in order to increase the adhesive strength, wherein, however, obstructive phenomena accompany, for example, lowering of the glass transition temperature (referred to in the following sometimes as Tg) and a considerable decrease in the elastic modulus. While, as for the adhesive strength, an increase may be expected by such a treatment, establishment of reliable electroconductive connection between the bonded elements under different conditions becomes difficult. It has been known, for example, that the electrical resistance increases at the junction of bonded elements in accompaniment with the reduction in the adhesive strength upon a high humidity aging at high temperatures. It is important, therefore, how this phenomenon should be suppressed as much as possible.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a connecting material for bonding and connecting elements to be bonded together, each element having electrodes thereon in a correspondingly confronting relationship, which material is highly reliable in the strength of bonding of the elements and in building up electroconductive connection between the corresponding electrodes and which can realize mechanical bonding and electrical connection effectively even when bonding an element of a polyimide resin film with a counter element, without occurrence of a reduction in the reliability of the electroconductive connection, even in services under a condition of high temperature and high humidity.
The present invention resides in the following connecting material:
(1) A connecting material for bonding and connecting elements each having electrodes thereon correspondingly confronting to each other, comprising
an adhesive component comprising a thermosetting resin,
the material having, after having been cured, the characteristic features comprising
a modulus of elasticity at 30° C., in the range of 0.9-3 GPa,
a glass transition temperature of, at the lowest, 100° C. and
a tensile elongation percentage of at least 3%.
(2) The connecting material as defined in the above (1), wherein the adhesive component further comprises 1-90% by weight of, on the one hand, a thermoplastic resin having a glass transition temperature of, at the highest, 50° C. and/or, on the other hand, a microparticulate elastomer having an average particle size of 30-300 nm.
(3) The connecting material as defined in the above (1) or (2), wherein it further comprises 0-40%, based on the volume of the adhesive component, of electroconductive particles.
(4) The connecting material as defined in any one of the above (1) to (3), wherein it exhibits a tensile elongation percentage of at least 6%.
DETAILED DESCRIPTION OF THE DISCLOSURE
For the elements to be bonded together by the connecting material according to the present invention, every pair of elements, each having electrodes correspondingly confronting to each other, in particular, a large number of electrodes to be connected electroconductively with those disposed confrontingly on the other element may serve as the object of connection. The present invention may particularly be applicable to those in which each of two elements to be bonded together has electrodes arranged within a narrow region with a closer pitch, in a small width and at a narrow interval, as in the case of assembling a driver chip or TCP on a glass substrate board in a LCD and in the case of installation of semiconductor chips, such as memories and ASIC, on a circuit board of general use. In many cases, a substrate board is used as the counter element for the above-mentioned IC chip or semiconductor chip to be bonded. The connecting material according to the present invention can be used for assembling semiconductor chips and the like on the substrate board directly or under intermediation with, for example, an interposer. Here, substrate boards made of any chosen material may be used, for example, glass/epoxy substrate boards, resin boards, glass boards and flexible resin boards. In general, a polyimide resin film has a lower adhesive nature. The connecting material according to the present invention can bond even to a polyimide resin film with reliable electroconductive connection of the electrodes disposed thereon with corresponding ones of the counter element. Of course, it can bond to substances other than a polyimide resin, wherein the adhesive strength and the reliability of
Suemasa Kaori
Takeichi Motohide
Yagi Hidekazu
Flynn ,Thiel, Boutell & Tanis, P.C.
Kopec Mark
Sony Chemicals Corporation
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