JPH04246840A - Ic mounting method - Google Patents

Abstract

PURPOSE:To provide the title IC mounting method of stable electrical connection solving the problem of defective connection due to the minor gap between the IC chip and a circuit substrate in relation to the connecting method of the IC chip applicable to electronic equipment to the circuit substrate such as liquid crystal panel, etc. CONSTITUTION:A spacer 6 thicker than the bump contacts 2 of an IC chip 1 is fixed between the IC chip 1 and a circuit substrate 5 using a bonding agent and then the bump contacts 2 of the IC chip 1 coated with a conductive bonding agent 4 and the electrode terminals 6 of the circuit substrate 5 are aligned and coupled with one another while said bonding agent 4 is thermoset so as to electrically connect the IC chip 1 to the circuit substrate 5.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses a conductive adhesive to connect protruding contacts formed on input/output pads of electric microcircuit elements such as IC chips and electrode terminals formed on a circuit board. The present invention relates to an IC mounting method for electrically connecting.

0002

2. Description of the Related Art Conventionally, soldering has been commonly used to connect electric microcircuit elements such as ICs to electrode terminals on circuit boards. However, in recent years, for example, in IC flat packages, etc., due to the miniaturization of IC chips and the increase in the number of connection terminals, the so-called pitch interval between connection terminals has become gradually narrower, and it has become difficult to cope with this problem using conventional soldering techniques. In addition, recently there has been a movement toward efficient use of mounting area by directly attaching bare IC chips to electrodes on glass substrates in calculators, electronic design, liquid crystal displays, etc.; There was a strong desire to develop a means of connection.

[0003] A method for electrically connecting a bare IC chip to an electrode on a circuit board is to apply a conductive adhesive to the conductive protruding contacts formed on the electrode pad of the IC chip, and then connect the electrode terminals of the circuit board. There is a technology for electrically connecting the IC chip and the circuit board by aligning the IC chip and the circuit board and curing the adhesive (Electronic Materials, September 1990 issue, ``Low-temperature process mounting technology for higher density and greater versatility'').

[0004] A conventional IC mounting method in a liquid crystal panel will be explained below with reference to the drawings.

14 to 17 are process diagrams showing a conventional IC mounting method, and FIG. 18 is an enlarged sectional view of the X section in FIG. 17. 14 to 18, reference numeral 1 denotes an IC chip, and gold protrusion contacts 2 having a height of 30 μm and a diameter of 80 μm are formed on 150 electrode pads (not shown) at a pitch of 150 μm using a plating method. 3 is a support on which a flexible conductive adhesive 4 film is formed. 5 is a circuit board such as a liquid crystal panel, and an IT board to which the IC chip 1 is connected.
An electrode terminal 6 made of an O electrode is formed.

In the conventional IC mounting method, as shown in FIG. 14, an IC chip 1 having protruding contacts 2 formed on electrode pads is first mounted on a support 3 on which a film of conductive adhesive 4 of about 25 μm is formed. The protruding contacts 2 of the IC chip 1 are immersed in the film of the conductive adhesive 4 for 2 seconds as shown in FIG. 15, so that the conductive adhesive 4 is applied to the protruding contacts 2 as shown in FIG. be done. Thereafter, the IC chip 1 coated with the conductive adhesive 4 is aligned and bonded to the ITO electrode 6 on the liquid crystal panel 5, and the conductive adhesive 4 is cured and connected by heating at 100° C. for 3 hours. is completed.

[0007]

[Problems to be Solved by the Invention] However, in the conventional method described above, although the conductive adhesive 4 is sufficiently spread over the ITO electrode 6 as shown in FIG.
The film of conductive adhesive 4 between the protruding contact 2 and the ITO electrode 6 is 5.
Liquid crystal panel 5 (coefficient of thermal expansion: approx. 5 x 10-6/°C) has been tested in thermal shock tests (-40°C to +80°C) with a thickness of less than μm.
The flexibility of the conductive adhesive 4 cannot sufficiently absorb the stress caused by the difference in thermal expansion coefficient between the IC chip 1 and the IC chip 1 (thermal expansion coefficient: approx. 3 x 10-6/°C), and the
0 cycles), the conductive adhesive 4 peels off and an open phenomenon occurs, and the conductive adhesive 4 spreads too much (up to 120 μm), causing a short circuit between adjacent ITO electrodes 6.

[0008] The present invention is intended to solve these problems, and aims to provide an excellent IC mounting method that provides stable electrical connections.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the IC mounting method of the present invention involves interposing a spacer thicker than the thickness of the protruding contact between the IC chip and the circuit board.
The first method is to mix conductive or insulating particles as a spacer into the conductive adhesive (the second method).

0010

[Operation] Therefore, according to the present invention, a spacer is provided between the IC chip and the circuit board and is thicker than the protrusion contact on the IC chip, thereby creating a gap between the protrusion contact of the IC chip and the electrode terminal of the circuit board. Since the conductive adhesive between the protruding contact and the electrode terminal can be thickened, the conductive adhesive becomes more flexible and can absorb stress during thermal shock tests, etc., and the electrode terminal By reducing the contact area, the spread of the conductive adhesive is restricted and short circuits between adjacent electrode terminals can be eliminated.

In the second method as well, the spacer particles mixed in the conductive adhesive connect the electrode terminals of the circuit board and the IC.
Since the chip is connected with a gap equal to the spacer particle between the tip and the protruding contact point, the same effect as the first method can be obtained.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in an embodiment of the present invention, parts having the same functions will be given the same reference numerals, detailed explanations will be omitted, and differences will be explained.

(Embodiment 1) FIGS. 1 to 7 are process diagrams showing an IC mounting method according to a first embodiment of the present invention, and FIG.
It is an enlarged sectional view of the X part inside. In FIGS. 1 to 8, 7 is a spacer made of a resin ball with a diameter of 40 μm, and is adhesively fixed with an ultraviolet curing adhesive 8 (acrylic resin).

Next, a method of implementing the above configuration will be explained. First, as shown in FIG.
An ultraviolet curable adhesive 8 with a thickness of about 10 μm or less is transferred and applied between the electrodes 6 by a stamping method, and after an appropriate amount of resin balls 7 are sprinkled as shown in FIG. 2, an output 8 is applied as shown in FIG.
It is irradiated with a 0W ultraviolet lamp 9 for 30 seconds to cure. Thereafter, as shown in FIG. 4, the IC chip 1 with the protruding contacts 2 formed on the electrode pads was moved onto the support 3 on which a film of conductive adhesive 4 with a thickness of about 25 μm was formed, and as shown in FIGS. As shown, the protruding contacts 2 of the IC chip 1 are immersed in a film of conductive adhesive 4 for 2 seconds, and then applied to the protruding contacts 2. Thereafter, as shown in FIG. 7, the IC chip 1 on which the conductive adhesive 4 has been applied is aligned with the ITO electrode 6 on the liquid crystal panel 5 and bonded. Then, by heating at 100° C. for 3 hours, the conductive adhesive 4 is cured and the connection is completed.

In this embodiment, an insulating resin ball 7 larger than the protruding contact 2 is interposed between the IC chip 1 and the ITO electrode 6 of the liquid crystal panel 5. As the gap between the protruding contact 2 of the IC chip 1 and the ITO electrode 6 on the liquid crystal panel 5 is wide, approximately 10 μm or more, the contact area between the ITO electrode 6 and the conductive adhesive 4 becomes small, and the adhesive spreads. The diameter was also reduced from the maximum of 120 μm in the conventional example to 100 μm, and there were no short-circuit defects between adjacent ITO electrodes 6 during connection. In addition, since the film thickness of the conductive adhesive 4 between the protruding contact 2 of the IC chip 1 and the ITO electrode 6 is more than twice that of the conventional one, the ability to absorb and relax stress due to the difference in thermal expansion coefficient increases, and the thermal shock test It was confirmed that even after 200 cycles (at −40 to +80° C.), there was no open phenomenon of the IC chip 1 due to peeling of the conductive adhesive 4.

(Embodiment 2) FIGS. 9 to 13 show the second embodiment of the present invention.
FIG. 13 is a process diagram showing the IC mounting method of the embodiment, and FIG. 13 is an enlarged sectional view of the X section in FIG. 12. In FIGS. 9 to 13, 10 is a spacer made of a 20 μm diameter conductive ball made of styrene polymer plated with nickel and gold.
It is mixed in the conductive adhesive 4 in an amount of 5% by weight.

Next, a method of implementing the above configuration will be explained. First, as shown in FIG. 9, the IC chip 1 with the protruding contacts 2 formed on the electrode pads is moved onto a support 3 on which a film of conductive adhesive 4 mixed with conductive balls 10 is formed. As shown in FIG. 10, the protruding contacts 2 of the IC chip 1 are immersed in a film of conductive adhesive 4 for 2 seconds, and the protruding contacts 2 are coated as shown in FIG. Thereafter, as shown in FIG. 12, the IC chip 1 on which the conductive adhesive 4 has been applied is aligned and bonded to the ITO electrode 6 on the liquid crystal panel 5. and,
The conductive adhesive 4 is cured by heating at 100° C. for 3 hours to complete the connection.

In this embodiment, the conductive balls 10 having a diameter of 20 μm are mixed into the conductive adhesive 4, so that the IC chip 1 is formed as shown in FIG.
A conductive ball 10 is placed under any one of the plurality of protruding contacts 2.
interposes, and as a result, the gap between the protruding contact 2 on the IC chip 1 and the ITO electrode 6 on the liquid crystal panel 5 becomes wide, approximately 20 μm or more, and the contact area between the ITO electrode 6 and the conductive adhesive 4 becomes smaller. The adhesive spreading diameter was reduced from the maximum of 120 μm in the conventional example to 100 μm, and there were no short-circuit defects between adjacent ITO electrodes 6 during connection. In addition, the stress absorption and relaxation power due to the difference in the thermal expansion coefficient of the conductive adhesive 4 increases, and the thermal shock test (-40 to +80°C) 200
IC due to peeling of the conductive adhesive 4 even after the cycle
It was confirmed that there was no open phenomenon of chip 1.

As described above, according to the above embodiment, since the resin ball 7 or the conductive ball 10, which is larger than the protruding contact 2, is interposed between the IC chip 1 and the liquid crystal panel 5, the protruding contact 2 and the ITO electrode 6 are interposed between the protruding contact 2 and the ITO electrode 6. The gap between the conductive adhesive 4 and the conductive adhesive 4 became wider, and the spread diameter of the conductive adhesive 4 became smaller. Therefore, there were no short-circuit defects between adjacent ITO electrodes 6.

[0020]

[Effects of the Invention] As is clear from the above embodiments, the present invention provides a method of interposing an insulating spacer larger than a protruding contact between an IC chip and a circuit board (first method) and using a conductive adhesive. By mixing conductive or insulating particles for a spacer (second method), the gap between the protruding contacts formed on the electrode pads on the IC chip and the electrode terminals on the circuit board is approximately 20 μm or more. and can be widened,
Since the contact area between the electrode terminal and the conductive adhesive becomes smaller, the adhesive spread diameter can be reduced, and the conductive adhesive becomes more flexible, absorbing stress during thermal shock tests, etc.
Therefore, it is possible to obtain a stable electrical connection without phenomena such as short-circuit failures due to peeling of the conductive adhesive.

[Brief explanation of the drawing]

[Fig. 1] Adhesive application process diagram in the IC mounting method of the first embodiment of the present invention.

[Figure 2] Process diagram of spacer dispersion in the same example

[Figure 3
] Process diagram of adhesive curing in the same example

[Figure 4] Diagram of the process of moving and loading IC chips in the same example

[Figure 5] Diagram of the process of applying conductive adhesive in the same example

[Figure 6] Diagram of the process of applying conductive adhesive in the same example

[Figure 7] Process diagram for positioning and bonding IC chips in the same example

[Fig. 8] Enlarged sectional view of the X section in Fig. 7

FIG. 9 is a process diagram for moving an IC chip in the second embodiment of the present invention.

[Figure 10] Process diagram of applying adhesive to IC chip in the same example

[Fig. 11] Diagram showing how adhesive is applied to the IC chip in the same example.

FIG. 12: Alignment of IC chip in the same example.
Joining process diagram

[Fig. 13] Enlarged sectional view of the X part in Fig. 12

[Figure 14] Process diagram for moving and loading IC chips in a conventional IC mounting method

[Figure 15] Process diagram for applying adhesive to an IC chip in the conventional IC mounting method

[Fig. 16] Diagram showing how adhesive is applied to an IC chip in the conventional IC mounting method.

[Figure 17] Alignment of IC chip in the conventional example
Joining process diagram

[Fig. 18] Enlarged sectional view of the X part in Fig. 17

[Explanation of symbols]

1 IC chip 2 Protruding contact 4 Conductive adhesive 5 Liquid crystal panel (circuit board) 6 ITO electrode (electrode terminal) 7 Resin ball (spacer) 10 Conductive ball (spacer)

Claims (2)

[Claims] 1. An IC mounting method in which an electrode terminal of a circuit board and a protruding contact are connected using a conductive adhesive on the top of a protruding contact formed on an electrode pad on an IC chip, comprising:
After fixing a spacer thicker than the thickness of the protruding contact of the IC chip between the IC chip and the circuit board with an adhesive,
An IC mounting method in which protruding contacts of an IC chip coated with a conductive adhesive are aligned and connected to electrode terminals of the circuit board. 2. The IC mounting method according to claim 1, wherein the conductive adhesive contains particles of a conductor or insulator having a diameter larger than the thickness of the protruding contact as a base material.