JPH04329208A - Electrically conductive paste and mounting substrate using the same - Google Patents

Abstract

PURPOSE:To provide a highly reliable electric connection by using a non- hardenable electrically conductive paste, and thereby easing the stress attributable to the thermal stress generated at the time of, for example, cold/hot impact test. CONSTITUTION:The electrically conductive paste 1 comprises an electrically conductive filler for which an Ag powder (particle size: 0.2 to 9mum), an Ag-Pd alloy powder (particle size: 0.1 to 15mum), and an Au powder (particle size: 0.5 to 1.2mum) are used, and a binder for which a non-hardenable silicone resin and white petrolatum are used. When the content of the Ag powder is 90wt.%, the paste 1 exhibits a minimum volumetric resistirity almost independently of the kind of the binder.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a conductive paste used for connecting chip-shaped electronic components such as IC chips to a group of terminal electrodes on a board, and a mounting board using the same. be.

0002

[Prior Art] In the past, solder was often used to connect the connection terminals of electronic components and the circuit pattern terminals on the board, but in recent years, with the miniaturization of IC flat packages, etc. The pitch spacing has become progressively narrower, making it increasingly difficult to address with traditional soldering techniques.

[0003] Recently, there has also been a movement toward efficient use of mounting area by directly attaching bare IC chips to electrodes on substrates for calculators, electronic watches, and liquid crystal displays. Fine electrical connection means are strongly desired. A method for electrically connecting a bare IC chip to an electrode on a substrate is to connect the protruding contacts (Au bumps) formed on the electrode pads of the IC chip and the terminal electrode group on the substrate using a thermosetting conductive paste. There are known methods for connecting.

0004

[Problems to be Solved by the Invention] However, with conventional thermosetting conductive pastes, there was a problem in that the thermal expansion coefficients of the IC chip and the circuit board were different, so that the connection parts were likely to deteriorate due to stress caused by thermal stress. .

The present invention has been made in view of the above problems, and its purpose is to alleviate stress caused by thermal stress when connecting an electrode pad of an electronic component to an electrode group on a substrate. The object of the present invention is to obtain a conductive paste and to obtain a highly reliable mounting board using the same.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention realizes a non-hardening conductive adhesive capable of stress relaxation using liquid resin or gel, and uses it to bond IC chips and circuit boards. The present invention attempts to alleviate stress caused by thermal stress by using the non-hardening conductive paste in electrical connection with terminal electrodes.

[0007]

[Operation] According to the above-described method of the present invention, by using a non-hardening conductive paste, it is possible to alleviate stress caused by thermal stress caused by a thermal shock test, etc., and a highly reliable electrical connection can be achieved. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conductive paste according to an embodiment of the present invention and a mounting board using the same will be described in detail below with reference to the drawings.

FIG. 1 is a structural sectional view of a mounting board using the conductive paste of the present invention. In FIG. 1, 1 is a conductive paste, 2 is an IC chip, 3 is an electrode pad of the IC chip, 4 is an Au bump (protruding contact), 5 is an Au thick film electrode, and 6
is a glass substrate.

In the embodiment of the present invention, Ag powder (particle size 0.2 to 9 μm) is added to the conductive filler as the conductive paste 1.
, AgPd alloy powder (particle size 0.1 to 15 μm), Au powder (particle size 0.5 to 1.2 μm), non-hardening silicone resin (manufactured by Toray Silicone Co., Ltd.) as a binder, and white petrolatum (Nacalai Tesque). (manufactured by Co., Ltd.) was used. When the content of Ag powder is 90% by weight, the conductive paste has a minimum systematic resistivity, almost independent of the type of binder.

For AgPd alloy powder and Au powder, the volume resistivity of the conductive paste is at its minimum when the content is 93% by weight and 97% by weight, respectively. The conductive paste 1 is transferred onto the IC chip 2 provided with the Au bumps 4, and the Au bumps 4 are connected to the Au thick film electrodes 5 on the glass substrate 6 via the conductive paste 1. At this time, it is also possible to cover the IC chip 2 with a sealant to supplement the adhesive strength.

For comparison with the conventional method, a mounting board was prepared using epoxy resin as a binder. -40℃/30 minutes to +125℃ for the mounting board prepared as above.
IC chips 2 and A when subjected to heat stress for 30 minutes at ℃
Table 1 shows the initial value of the resistance value between the u-thick film electrodes 5 and the number of times the resistance value becomes 10 times or more.

[0013]

[Table 1]

Comparing the non-hardening conductive paste of the present invention with the conventional thermosetting conductive paste, the difference is 2 to 5.
The lifespan is doubled.

In this example, A is used as the conductive filler.
Although the above description has been made of powders of Ag, AgPd, and Au, the present invention is not limited thereto, and it is also possible to use AgAu mixed powder. Further, as another example, the same effect as that of an IC chip can be obtained with a chip-shaped electronic component.

[0016]

As described above, by using the conductive paste of the present invention, it is possible to connect an IC chip and a substrate with excellent relaxation of stress caused by thermal stress. Further, since the conductive paste of the present invention does not require curing treatment, the mounting process can be simplified, and furthermore, it is excellent in repairability of IC chips.

[Brief explanation of drawings]

FIG. 1 is a structural sectional view showing a first embodiment of the present invention.

[Explanation of symbols]

1 Conductive paste 2 IC chip 3　IC chip electrode pad 4 Au bump (protruding electrode) 5　Au thick film electrode 6 Glass substrate

Claims (11)

[Claims] 1. A conductive paste comprising a conductive filler and a binder, which does not harden by heating. 2. The conductive paste according to claim 1, wherein the binder comprises at least one of liquid or gel silicone and aliphatic hydrocarbon semisolid resin such as vaseline. 3. Claim 1, wherein the conductive filler is made of at least one of Ag, Pd, and Au.
or 2. The conductive paste according to any one of 2. [Claim 4] The particle size distribution of the conductive filler is 15 μm.
The conductive paste according to claim 3, characterized in that: 5. The conductive paste according to claim 1, wherein the conductive filler is made of Ag. 6. The conductive paste according to claim 1, wherein the conductive filler is made of Au. 7. The conductive paste according to claim 1, wherein the conductive filler is made of an alloy of Ag and Pd and contains at least 70% by weight of Ag. 8. The conductive paste according to claim 1, wherein the conductive paste contains a conductive filler in an amount equal to or more than the conductive filler exhibiting the minimum volume resistivity. 9. The conductive paste according to claim 4, wherein the binder is liquid silicone and has a viscosity of 0.7 to 5 Pa·s. 10. A mounting board characterized in that a protruding contact formed on an electrode pad of a chip-shaped electronic component and a terminal electrode on a circuit board are connected by a non-hardening conductive paste. 11. A mounting board characterized in that an electrode pad of a chip-shaped electronic component and a terminal electrode on a circuit board are connected by a non-hardening conductive paste.