JPH065735A - Circuit board and pressurizing tool - Google Patents

Abstract

PURPOSE:To connect a bare chip IC to a circuit board with high reliability by sufficiently supplying adhesive to a periphery of a bump, a wiring layer when the IC is face bonded onto the board with the adhesive, and eliminating remainder of foam in the adhesive after the adhesive is cured. CONSTITUTION:A circuit board 6 has a supporting board 5, a wiring layer 4 formed on the board 5 and a bump 3 formed at an end of the layer 4 to connect a bare chip IC 2 to face bond the IC 2 with adhesive 7, and comprises a dummy pattern 10 between adjacent layers 4 or a shape of an end of the layer 4 is formed in a wedge state or a circular arc state. Or, as a pressurizing tool to be used in the case of face bonding, the tool in which a recess is provided on a pressurizing surface is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board for face-bonding a bare chip IC with an adhesive. More specifically, the present invention relates to a wiring board that can achieve a good connection state in terms of strength and electrical properties. Further, the present invention provides a pressure tool that can be preferably used when satisfactorily connecting such a wiring board and a bare chip IC, and a method of face-bonding the bare chip IC to the wiring board using the pressure tool. Also related to.

[0002]

2. Description of the Related Art In recent years, electronic devices such as ID cards have been downsized. Therefore, bare chip I
It has become common to mount C by face-bonding it to a flexible wiring board with an adhesive.

FIG. 5 is an explanatory view of a general method for face-bonding a bare chip IC to a flexible wiring board with an insulating adhesive. First, a bare chip IC 2 is mounted on a flat substrate 1 capable of generating a heat pulse, and its bonding surface 2a
To face up. Separately from this, a wiring substrate 6 made of a flexible support substrate 5 having a wiring layer 4 such as an inner lead having a bump 3 at the end is prepared, and a thermosetting adhesive 7 for bonding the bare chip IC 2 is made flexible. After coating on the portion of the support substrate 5 surrounded by the bump 3, the bare chip IC 2 and the bump 3 are opposed to each other (see FIG.
(A)).

Next, the flexible substrate 5 is heated while being pressed by a pressing tool 8 having a flat surface, and the thermosetting adhesive 7 is caused to flow around the bumps 3 and the wiring layer 4 in the direction of the arrow to form a bonding area. Curing with increasing
(B)).

Then, the pressure tool 7 is separated to complete the face bonding of the bare chip IC 2 to the wiring board 6 (FIG. 5C).

[0006]

However, when the bare chip IC 2 is face-bonded to the conventional wiring board 6, the adhesive strength of the bare chip IC 2 is not sufficient, as will be described below with reference to the plan view of the wiring board 6. In addition, air bubbles may remain in the adhesive after curing, and there is a problem that the reliability of bonding is not sufficient. That is, as shown in FIG. 6A, which is a plan view of the wiring substrate 6 viewed from the wiring layer 4 side, the tip 4a of the wiring layer 4 on which the bumps 3 are formed has a rectangular shape, so that insulation is achieved. When the conductive adhesive 7 is pressed by the bare chip IC 2 (the part indicated by the square dotted line in the figure), the insulating adhesive 7 hits the tip 4a of the wiring layer 4 and flows in the direction of the arrow in the figure, and as a result, As shown in FIG. 6B, when the adhesive 7 is not sufficiently supplied around the bump 3 and the wiring layer 4,
As shown in (c), air bubbles 9 are formed around the bump 3 and the wiring layer 4.
May remain, and thus there is a problem that the reliability of the contact between the bump 3 and the bare chip IC 2 is not sufficient.

The present invention is intended to solve the above-described problems of the prior art, and a bare chip I is formed on a wiring board.
When face-bonding C with an adhesive, the adhesive can be sufficiently supplied around the bumps and the wiring layer, and no bubbles remain after the adhesive is hardened, so that the bare chip can be highly reliable on the wiring board. The purpose is to be able to bond ICs.

[0008]

The inventor of the present invention specializes in the shape of the pressing surface of the pressing tool used when devising the wiring board or performing face bonding so that the adhesive exhibits a preferable flow. The inventors have found that the above-mentioned objects can be achieved by the above, and have completed the present invention.

That is, the first invention is a bare chip IC.
In a wiring substrate for face bonding with an adhesive, the wiring substrate includes a support substrate, a wiring layer formed thereon, and a bump formed at an end of the wiring layer for connecting the bare chip IC, and A wiring board having a dummy pattern provided between adjacent wiring layers.

A second aspect of the present invention is a bare chip IC.
In a wiring substrate for face bonding with an adhesive, the wiring substrate includes a support substrate, a wiring layer formed thereon, and a bump formed at an end of the wiring layer for connecting the bare chip IC, and Provided is a wiring board in which the tip of the wiring layer has a wedge shape or an arc shape.

Further, a third aspect of the present invention is a pressure tool for pressurizing a joint portion when an electronic component is joined to a flexible wiring board with an adhesive, wherein a concave portion is provided on a pressure surface of the pressure tool. A pressurizing tool characterized by being provided.

According to a fourth aspect of the present invention, an adhesive is applied to the wiring layer side of the wiring board, a bare chip IC is arranged so as to face the adhesive, and pressure is applied from the wiring board side with the tool described above. A face bonding method for bare chip ICs is provided.

The present invention will be described below in detail with reference to the drawings. In addition, the same reference numerals represent the same or equivalent constituent elements, including the drawings showing the above-mentioned related art.

FIG. 1 is a partial plan view of a preferred embodiment of the first wiring board of the present invention. The wiring board 6 of the first invention can take any form of a rigid wiring board and a flexible wiring board, but as shown in FIG. 1, the supporting board 5, preferably the flexible supporting board 5 is used. A wiring layer 4 and bumps 3 are formed on the wiring layer 4, and a ginkgo leaf-shaped dummy pattern 1 is provided between adjacent wiring layers 4.
0 is formed (FIG. 1A). Due to the presence of such a dummy pattern 10, as shown in FIG. 1B, the adhesive 7 can be sufficiently supplied to the periphery of the wiring layer 4 and the bumps 3 without a gap, and bubbles can be prevented from existing. Can be

In the first aspect of the present invention, the size and shape of the dummy pattern 10 is such that the adhesive 7, for example, an insulative epoxy adhesive can be sufficiently supplied to the periphery of the bump 3 and the wiring layer 4 without a gap. The size and shape are not particularly limited, and may be, for example, a circle (FIG. 1C) or a rectangle (FIG. 1C).
(D)) may be used. Further, the dummy patterns can be made asymmetrical according to the arrangement and width of the wiring layers, and the number thereof, and the dummy patterns need not be provided between some wiring layers.

The first wiring board of the present invention is
For example, it can be manufactured by simultaneously forming a wiring layer and a dummy pattern on a flexible substrate by screen printing using a silver paste, and then forming bumps on the wiring layer with a copper paste. The substrate, silver paste, copper paste, and the like used can be those conventionally used.

FIG. 2 is a partial plan view of a preferred embodiment of the second wiring layer of the present invention. The wiring board 6 of the second present invention can also take the form of either a rigid wiring board or a flexible wiring board, but as shown in FIG. 2, it is provided on the supporting board 5, preferably on the flexible supporting board 5. It has a structure in which the wiring layer 4 and the bumps 3 are formed, and the tip portion 4a of the wiring layer has an arc shape (FIGS. 2A and 2C) or a wedge shape (FIG. 2D). It is characterized in that. Thus, the tip 4a of the wiring layer 4
2B has an arc shape or a wedge shape, as shown in FIG. 2B, the adhesive 7 can be sufficiently supplied to the periphery of the wiring layer 4 and the bumps 3 without a gap, and bubbles 9 are not present. Can be

In the second aspect of the present invention, when the curvature of the arc of the tip portion 4a of the wiring layer 4 and the sharp angle of the wedge are used, the adhesive 7 such as an insulative epoxy adhesive surrounds the bump 3 and the wiring layer 4. The shape is not particularly limited as long as it can be sufficiently supplied without gaps. Further, the shape of the tip 4a of the wiring layer 4 can be made asymmetrical according to the arrangement and width of the wiring layer, and the number thereof.

The wiring board according to the second aspect of the present invention is
For example, a flexible support substrate can be manufactured by forming a wiring layer having an arcuate or wedge-shaped tip with a silver paste by a screen printing method, and then forming bumps with a copper paste on the wiring layer. . The substrate, silver paste, copper paste, and the like used can be those conventionally used.

By combining the first aspect of the invention and the second aspect of the invention, that is, by providing the dummy pattern and making the tip of the wiring layer arc-shaped or wedge-shaped, it is even more sufficient. Adhesive can be sufficiently supplied to the wiring layers and bumps without any gaps, and bubbles can be prevented from existing.

FIG. 3 is a perspective view of a preferred embodiment of the third inventive pressure tool. As shown in the figure, in the pressing tool 8 of the third aspect of the present invention, a recess 8b is formed substantially in the center of the pressing surface 8a.

When the bare chip IC 2 is face-bonded to the flexible wiring board 6 as shown in FIG. 4A by using the pressure tool 8 of the third invention, as shown in FIG.
As shown in (b), the convex portion 5a is formed on the flexible support substrate 5.
Is formed. As a result, the bubbles existing in the adhesive 7 are collected in the convex portions 5a and the convex portions 5a function as an air reservoir, so that the bubbles can be removed from around the bumps 3 and the wiring layer 4. In addition, since the thickness of the adhesive 7 is increased at the convex portion 5a, the adhesive strength is improved, and it is possible to prevent water from entering the joint portion.

The recess 8b of the third pressure tool 8 of the present invention.
The size, position, number, etc. of can be appropriately determined according to the arrangement and pitch of the wiring layers to be joined, the type of adhesive used, and the like. For example, bare chip IC2 is 2mm x
In the case of a size of 2 mm, the pressing tool 8 has a pressing surface radius of 3 to 8 mm, and one concave portion 8b is provided in the center thereof.
It is preferable that the diameter of the concave portion 8b is 0.5 to 1.0 mm and the depth of the concave portion is 0.5 to 1.0 mm.

The pressure tool 8 of the third invention is
It can be preferably used when face-bonding the bare chip IC 2 to the flexible wiring board 6 with the adhesive 7, but not limited to this application, the flexible wiring board is provided with an electronic component, preferably a flat electronic component with an epoxy resin. It can be widely used when joining with an adhesive such as an insulating adhesive.

[0025]

According to the wiring board of the present invention, a dummy pattern is provided between adjacent wiring layers, or the tip of the wiring layer is formed in an arc shape or a wedge shape. Thus, the adhesive can be sufficiently supplied to the periphery of the bump and the wiring layer without leaving a gap, and bubbles can be prevented from existing in the cured adhesive.

Further, according to the pressing tool of the present invention, since the concave portion is formed on the pressing surface, the convex portion is formed on the wiring board when the electronic component is bonded to the flexible wiring board with the adhesive. be able to. Therefore, it is possible to increase the thickness of the joint portion and to concentrate the bubbles on the convex portions so as not to adversely affect the joint portion.

[0027]

EXAMPLES The present invention will be described in detail below based on examples.

Example 1 A PPS film having a thickness of 25 μm (Torelina # 25, manufactured by Toray Industries, Inc.) was used as a flexible substrate, and a silver paste (FA-707, manufactured by Fujikura Kasei Co., Ltd.) was applied on the PPS film as shown in FIG. Wiring pattern as shown (0.4mm width)
And a dummy pattern were screen-printed to a dry thickness of 20 μm and cured at 150 ° C. for 30 minutes.

Next, bumps were screen-printed on the tip of the wiring pattern with a copper paste (E-5000, manufactured by Mitsui Kinzoku Co., Ltd.) so that the dry thickness was 40 μm, and 750 ° C.
And cured for 30 minutes to obtain a wiring board.

On this wiring board, 0.15 mg of an epoxy thermosetting insulating adhesive (manufactured by Sony Chemical Co., Ltd.) was applied to the portion surrounded by the bumps. This is aligned with a 2 mm square bare chip IC fixed by a vacuum chuck on a pulse heating type heating tool by image processing, and then pressure bonding (0. 9 kgf), and while keeping this state, it was heated at 170 ° C. for 3 seconds to be cured and adhered, and the bare chip IC was face-bonded.

A pressure cooker test (121 ° C., 2 atm, 100% RH) was performed on 10 wiring board samples to which bare chip ICs were face-bonded. For the evaluation, the resistance value of the contact after 1 hour, 3 hours, and 5 hours was examined, and one having an initial resistance value of 1Ω of 10Ω was rejected. As a result, no sample failed even after 1 hour, 3 hours, or 5 hours.

Example 2 The shape of the tip of the wiring layer is shown in FIG.
A wiring board was obtained by repeating Example 1 except that the shape as shown in FIG. A bare chip IC was face-bonded to the obtained wiring board in the same manner as in Example 1, and a pressure cooker test was performed. As a result, 1
After 10 hours, 3 hours, and 5 hours, none of the 10 samples failed.

Example 3 The shape of the tip of the wiring layer is shown in FIG.
A wiring board was obtained by repeating Example 1 except that the shape shown in FIG. A bare chip IC was face-bonded to the obtained wiring board in the same manner as in Example 1, and a pressure cooker test was performed. As a result, none of the 10 samples failed even after 1 hour, 3 hours, and 5 hours.

Example 4 A wiring board having the structure shown in FIG. 6 (a) was used.
A wiring board was obtained by repeating Example 1 except that the pressure tool shown in FIG. 3 having a concave portion on the pressure surface was used as the pressure tool and the amount of the adhesive used was 0.1 mg. The thickness of the convex portion of the adhesive layer of the obtained wiring board was about 100 to 150 μm, which was 2 to 3 times the usual thickness.

A pressure cooker test was conducted on the obtained wiring board in the same manner as in Example 1 except that the bare chip IC was face-bonded in the same manner as in Example 1 and the humidity was set to 85% RH. As a result, none of the 10 samples failed even after 5 hours.

Comparative Example 1 A wiring board was obtained by repeating Example 1 except that no dummy pattern was provided. A bare chip IC was face-bonded to the obtained wiring board in the same manner as in Example 1,
A pressure cooker test was conducted. As a result, after 1 hour, 8 out of 10 samples failed and 3
All failed after 5 hours and 5 hours. Further, the pressure cooker test was performed again in the same manner as in Example 1 except that the humidity was changed to 85% RH. As a result, after 2.5 hours, 2 out of 10 samples failed, and after 5 hours, 8 samples failed.

[0037]

According to the present invention, when face bonding a bare chip IC to a wiring board with an adhesive, the adhesive can be sufficiently supplied around bumps and wiring layers, and after the adhesive is hardened. Since it is possible to prevent bubbles from remaining, the bare chip I can be highly reliable on the wiring board.
C can be joined.

[Brief description of drawings]

FIG. 1 is a partial plan view of a preferred embodiment of a first wiring board of the present invention.

FIG. 2 is a partial plan view of a preferred embodiment of a second wiring board of the present invention.

FIG. 3 is a perspective view of a preferred embodiment of a third inventive pressure tool.

FIG. 4 is an explanatory diagram of a case where an electronic component is bonded to a substrate by using a pressure tool according to a third aspect of the present invention.

FIG. 5 is an explanatory diagram of a general method for face-bonding a bare chip IC to a wiring board with an adhesive.

FIG. 6 is a partial plan view of a conventional wiring board.

[Explanation of symbols]

 1 Base 2 Bare Chip IC 3 Bump 4 Wiring Layer 5 Supporting Substrate 6 Wiring Substrate 7 Adhesive 8 Pressure Tool 9 Bubble 10 Dummy Pattern

[Procedure amendment]

[Submission date] August 11, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

FIG. 5 is an explanatory view of a general method for face-bonding a bare chip IC to a flexible wiring board with an insulating adhesive. First, a bare chip IC 2 is mounted on a flat substrate 1 capable of generating a heat pulse, and its bonding surface 2a
To face up. Separately, prepare the wiring substrate 6 made of a flexible supporting substrate 5 on which the wiring layer 4, such as the inner lead is formed with a van-flop 3 to the end, the thermosetting adhesive 7 for bonding the bare chip IC2 after application to the portion surrounded by the van-flop 3 of the flexible support substrate 5 is made to face the bare chip IC2 and bumps 3 (FIG. 5
(A)).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Next, the pressure tool 8 is separated to complete the face bonding of the bare chip IC 2 to the wiring board 6 (FIG. 5B).

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

Next, copper paste (E-5000, Mitsui Kinzoku Co., Ltd.) on the tip portion of the wiring pattern by screen printing so as to 40μm bump at a dry thickness in, 1 50 ° C.
And cured for 30 minutes to obtain a wiring board.

Claims (4)

[Claims] 1. A wiring board for face-bonding a bare chip IC with an adhesive, wherein the wiring board is a support substrate, a wiring layer formed thereon, and a bare chip IC.
A wiring board comprising a bump formed at an end portion of a wiring layer for connecting the wiring layers, and a dummy pattern is provided between adjacent wiring layers. 2. A wiring board for face-bonding a bare chip IC with an adhesive, wherein the wiring board is a support substrate, a wiring layer formed thereon, and a bare chip IC.
A wiring board comprising a bump formed at an end portion of a wiring layer for connecting to each other, and a tip of the wiring layer having a wedge shape or an arc shape. 3. A pressure tool for pressurizing a joint portion when an electronic component is joined to a flexible wiring board with an adhesive, wherein a depression surface is provided on a pressing surface of the pressure tool. Pressurizing tool. 4. An adhesive is applied to the wiring layer side of the wiring board according to claim 1 or 2, and a bare chip IC is arranged so as to face the adhesive, and the pressure tool according to claim 3 is applied from the wiring board side. A face bonding method for bare chip ICs, characterized by applying pressure.