JPH0520921A - Conductive paste and mounting board using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a conductive paste capable of relieving the stress due to thermal stress when connecting the electrode pad of an electronic part and the electrode group on the substrate, and to use it for reliability. To get a high mounting board. [Constitution] A conductive filler and a polyvinyl butyral binder represented by the general formula:
Conductive paste consisting of solvent and solid lubricant. And a mounting board in which an electrode pad of an electronic component and a terminal electrode group on the board are connected via the conductive paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste used for connecting a chip-shaped electronic component represented by an IC chip to a terminal electrode on a substrate, and a mounting substrate using the same.

[0002]

2. Description of the Related Art In the past, solder was often used to connect a connection terminal of an electronic component and a circuit pattern terminal on a board. However, in recent years, for example, IC flat packages are downsized and the connection terminals are so-called. The pitch interval has become narrower and it has become difficult to cope with it by the conventional soldering technique.

Recently, in calculators, electronic timepieces, liquid crystal displays, etc., there is a movement to directly attach a bare IC chip to an electrode on a substrate to efficiently use a mounting area. There is a strong demand for fine electrical connection means. As a method of electrically connecting the bare IC chip to the electrodes of the substrate, a thermosetting conductive paste is used for the protruding contacts (Au bumps) formed on the electrode pads of the IC chip and the terminal electrode group of the substrate. It is known how to connect.

[0004]

However, in the conventional thermosetting type conductive paste, since the thermal expansion coefficient of the IC chip and that of the circuit board are different, there is a problem that the connection portion is likely to be deteriorated by the stress due to the thermal stress. .

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

[0006]

In order to solve the above-mentioned problems, the present invention realizes a conductive adhesive capable of stress relaxation using polyvinyl butyral represented by the general formula (Chem. 1) as a binder. In the electrical connection between the chip and the terminal electrode of the circuit board, the conductive paste is used to alleviate stress due to thermal stress.

[0007]

According to the above-mentioned method of the present invention, by using a conductive paste containing polyvinyl butyral represented by the general formula (Formula 1) as a binder, stress due to thermal stress generated in a thermal shock test or the like is relaxed, Furthermore, by adding a lubricant, the contact state between the conductive fillers can be kept good, and highly reliable electrical connection can be achieved.

[0008]

DETAILED 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 below in detail 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, as the conductive paste 1, Ag powder (particle size 0.2 to 9 μm), A
gPd alloy powder (particle size 0.1 to 15 μm), Au powder (particle size
0.5 to 1.2 μm) and polyvinyl butyral represented by the general formula (Chemical Formula 1) as a binder (Union Carbide Co., Ltd.)
Made, number average molecular weight about 120,000), solvent diethylene glycol monobutyl ether, solid lubricant tungsten disulfide, molybdenum disulfide, β tantalum sulfide,
What was produced using titanium selenide and β niobium selenide was used. The content rate of the conductive filler at this time was 85 vol% with respect to the solid content volume. The amount of solvent was 10 wt% in terms of vehicle concentration. The solid lubricant was added to the conductive filler in a weight ratio of 0.02 to 0.08. Conductive paste 1
Is transferred to the IC chip 2 provided with Au bumps 4, and
The bump 4 was connected to the Au thick film electrode 5 on the glass substrate 6 via the conductive paste 1 to prepare a sample.

At this time, it is possible to cover the IC chip 2 with a sealant in order to supplement the adhesive strength. The mounting board manufactured as described above was subjected to a thermal shock test at −40 ° C./30 minutes to + 125 ° C. for 30 minutes. For comparison, the same test was performed on the sample to which the solid lubricant was not added. The resistance value between the IC chip 2 and the Au thick film electrode 5 is 2 with respect to the initial value.
The number of times of doubling is shown in (Table 1).

[0012]

[Table 1]

The conductive paste of the present invention is considerably extended in life as compared with the conventional thermosetting conductive paste. In particular, the filler is Au and its content is 80-
90% was good.

In this embodiment, A is used as the conductive filler.
Although the g, AgPd, and Au powders have been described, the present invention is not limited thereto, and AgAu mixed powder can be used. Further, as another embodiment, the same effect as that of the IC chip can be obtained for a chip-shaped electronic component.

Regarding the molecular weight of polyvinyl butyral
It was carried out for 100,000 or less, but 100,000 to 150,00
The results were not as good as those of 0. Tungsten disulfide, molybdenum disulfide, β tantalum sulfide, titanium selenide, and β niobium selenide were used as the solid lubricants in this example, but the solid lubricant is not limited thereto. Molybdenum chloride and tantalum selenide can also be used.

[0016]

As described above, by using the conductive paste of the present invention, it is possible to connect the IC chip and the substrate which are excellent in alleviating the stress caused by the thermal stress.

[Brief description 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 Electrode pad of IC chip 4 Au bump (protruding electrode) 5 Au thick film electrode 6 glass substrates

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/32 B 9154-4E

Claims (8)

[Claims] 1. A conductive filler, a binder, a solvent and a solid lubricant, wherein the binder has the general formula: A conductive paste characterized by being polyvinyl butyral represented by. 2. The conductive filler is made of at least one of Ag, Pd, and Au, has a particle size distribution of 15 μm or less, and has a volume content of 80 to 90% of the solid content volume. The conductive paste according to claim 1. 3. The conductive filler is made of at least one of Ag, Pd, and Au and has a particle size distribution of 15 μm or less, and the solid lubricant is a sulfide of tungsten, molybdenum, titanium, niobium, or tantalum. Characterized by comprising at least one kind of selenide, the total volume content of the conductive filler and the solid lubricant is 80 to 90%, and the weight ratio of the solid lubricant to the conductive filler is 0.02 to 0.08. The conductive paste according to claim 1. 4. The number average molecular weight of polyvinyl butyral is
100,000-150,000, solid lubricant is tungsten,
The conductive paste according to claim 1, which is made of one or more of sulfides and selenides of molybdenum, titanium, niobium, and tantalum. 5. The conductive filler is Au, the shape is spherical, the particle size distribution is 5 μm or less, and the solid lubricant is at least one of sulfides or selenides of tungsten, molybdenum, titanium, niobium, and tantalum. The total volume content of conductive filler and solid lubricant is 80 ~
The conductive paste according to claim 1, which is 90% and the weight ratio of the solid lubricant to the conductive filler is 0.02 to 0.08. 6. The conductive filler is Au, the shape is spherical, the particle size distribution is 5 μm or less, and the volume content is 8 of solid content volume.
0 to 90%, the number average molecular weight of polyvinyl butyral is 100,000 to 150,000, and the solid lubricant is one or more of sulfides or selenides of tungsten, molybdenum, titanium, niobium, and tantalum. The conductive paste according to claim 1, characterized in that. 7. A protruding contact formed on an electrode pad of a chip-shaped electronic component and a terminal electrode on a circuit board are provided.
A mounting board, which is connected by the conductive paste described in any one of 2, 3, 4, 5, and 6. 8. An electrode pad of a chip-shaped electronic component and a terminal electrode on a circuit board are connected by the conductive paste according to any one of claims 1, 2, 3, 4, 5, and 6. And mounting board.