Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-09-15
2003-05-20
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S442000, C523S443000, C523S444000, C523S466000, C523S468000, C525S504000, C525S523000, C525S524000, C525S903000
Reexamination Certificate
active
06566422
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a connecting material for bonding and connecting elements to be bonded together having a plurality of electrodes opposite to those on the other element, in particular, a connecting material containing a thermosetting resin.
DESCRIPTION OF THE RELATED TECHNIQUES
For assembling a semiconductor, such as an IC, LSI or so on, on a substrate circuit board, a practice has-been employed, in which a semiconductor chip, such as a bear chip, is mounted directly on the substrate circuit board using a connecting material. Here, the bonding of such a chip with the circuit board is performed by holding them in a posture in which the electrodes or terminals disposed on the chip and on the circuit board are in a correspondingly confronting relationship to each other, while interposing the connecting material therebetween, whereupon the connecting material is caused to harden to attain mechanical firm bonding of them and an assured electroconductive connection between the corresponding electrodes simultaneously.
In such a connecting material, a thermosetting resin has been used as the fundamental constituent. The connecting material is interposed between the substrate circuit board and the semiconductor chip and they are held at such a posture that the electrodes or terminals to be electroconductively connected together disposed on them are in a correspondingly opposing relationship to each other, whereupon the resulting assemblage is heat-pressed from both sides by pressing it with heating to cause the thermosetting resin to set to thereby attain a firm bonding of them Here, the mechanical bonding of the chip with the substrate circuit board is established by the bonding strength (adhesive strength) of the resin and the electroconductive 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 electroconductive connection between the opposing electrodes may be attained by direct contact of the electrodes with each other or under intermediation by bridging therebetween by electroconductive particles contained in the connecting material in a dispersed state.
The substrate circuit board having assembled thereon semiconductor chip(s) is required to have a heat resistance for withstanding the condition in the step of reflowing of the solder in which the substrate board is exposed to a high temperature. The resulting assembly of the circuit board may be put in service under an environmental condition of relatively high temperature and relatively high humidity, so that it should withstand such a condition. However, the heat resistance and the fastness to environmental condition of conventional connecting materials are not enough and, thus, a problem has been brought about in that occurrence of defective electrical connection in the assembly is sometimes detected not only in the examination tests for the heat resistance and for the fastness to environmental condition, such as heat shock test, pressure cooker test (PCT) and solder-reflowing test, but also in the practical production process steps, when the assembly is exposed to a high temperature. Such a faulty electroconductive connection occurs often in assemblies having semiconductor chips with a narrow-pitched pattern in which a large number of electrodes are arranged within a confirmed region.
Examination of the reason-therefor has reached a discovery that a discrepancy or displacement in the settled positions of the electrodes occurs on connecting two elements with each other, of which coefficients of linear expansion are different from each other, using a connecting material, when the connecting material is brought to a temperature above the glass transition temperature (Tg) of the adhesive resin in the connecting material, as in the case where the material is exposed to such a high temperature as in the reflowing of solder, whereby a faulty electroconductive connection is caused. Here, it is assumed that decrease in the fastness to environmental conditions may be caused by a possible inter layer exfoliation of the bonding layer at the interfaces between the connecting material layer and the elements after a prolonged service, since the internal stresses in the cured layer of the connecting material resulting from the hardening contraction of the adhesive resin, which is large for an adhesive resin exhibiting a high adhesive strength, are concentrated at these interfaces.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a connecting material for bonding and connecting elements having electrodes thereon in a correspondingly confronting relation to each other, while attaining assured electroconductive connection between the corresponding electrodes, which connecting material exhibits a high heat resistance and will not suffer from occurrence of faulty electrical connection, even when the elements have a large number of electrodes arranged at a narrow interval and even if the connecting material is exposed to a condition of a high temperature.
Another object of the present invention is to provide a connecting material for bonding and connecting elements having electrodes thereon in a correspondingly confronting relation to each other, which connecting material exhibits a high heat resistance and a high fastness to environmentalconditions and can maintain a highly reliable electroconductive connection even in services under an environmental condition of high temperature and high relative humidity.
Thus, the present invention resides in the following connection material:
(1) A connecting material (the first connecting material) for bonding and connecting elements having electrodes thereon in a correspondingly confronting relation to each other, comprising
an adhesive component comprising a thermosetting resin and an inorganic filler,
the material having, after having been cured, characteristic features comprising
a modulus of elasticity in the range of 1-12 GPa,
a glass transition temperature (Tg) in the range from 120 to 200° C.,
a coefficient of linear expansion (&agr;1) of 50 ppm/° C. or lower at temperatures below the Tg and
a coefficient of linear expansion (&agr;2) of 110 ppm/° C. or lower at temperatures above the Tg, wherein the difference (&agr;2−&agr;1) does not exceed over 60 ppm/° C.
(2) A connecting material (the second connecting material) for bonding and connecting elements having electrodes thereon in a correspondingly confronting relation to each other, comprising
an adhesive component comprising a thermosetting resin and an inorganic filler,
the material having, after having been cured, characteristic features comprising
a linear contraction of 0.25% or less and
a coefficient of linear expansion (&agr;1) or 35 ppm/° C. or lower at temperatures below the Tg of the cured material.
(3) The connecting material as defined in the above (2), wherein it has, after having been cured, a moisture absorbability of 2% or lower.
(4) The connecting material as defined in any one of the above (1) to (3), wherein the adhesive component comprises 20-75% by weight of the thermosetting resin, 25-80% by weight of the inorganic filler and 0-40% by weight of a thermoplastic resin.
(5) The connecting material as defined in any one of the above (1) to (4), wherein it further comprises 0-30%, based on the volume of the adhesive component, of electroconductive particles having an average particle size of 1-10 &mgr;m.
DETAILED DESCRIPTION OF THE DISCLOSURE
The first and the second connecting materials according to the present invention are defined using characteristic features of material properties different from each other, while their compositions are defined to be similar, wherein the first connecting material is superior in heat resistance and the second connecting material is excellent both in heat resistance and in fastness to environmental conditions.
For the elements to be bonded together by the connecting material according to the present invention, every pair of
Shinozaki Junji
Takeichi Motohide
Yagi Hidekazu
Aylward D.
Dawson Robert
Flynn ,Thiel, Boutell & Tanis, P.C.
Sony Chemicals Corporation
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