JPS61194796A - Junction structure of electronic component and method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electronic component bonding structure and method for directly bonding an electronic component to a wiring board surface.

[Technical background of the invention]

As a method for attaching electronic components such as LSI chips and liquid crystal display panels to wiring boards, there is a method of directly bonding electronic components to the wiring board surface.

Conventionally, this method involves forming a plurality of electronic component connection terminals in an array on the electronic component bonding surface of the wiring board surface, which correspond to the plurality of external circuit connection terminals formed on the wiring board bonding surface of the electronic component. , apply an anisotropic conductive adhesive over each electronic component connection terminal to the electronic component bonding surface of this wiring board, stack the electronic components on top of it, and then place the electronic components and the wiring board relative to each other in this state. A method has been adopted in which an electronic component and a wiring board are adhesively bonded by pressing the terminals of the electronic component to conductively connect each other.

The anisotropically conductive adhesive is an insulating adhesive mixed with conductive particles in a proportion such that the conductive particles do not come into contact with each other. The adhesive layer exhibits conductivity in the thickness direction but insulating properties in the plane direction (lateral direction). When the component and the wiring board are pressed relative to each other, each terminal of the electronic component and each terminal of the wiring board are electrically connected (conductively connected via the conductive particles).

[Problems with background technology]

However, although the method of adhesively bonding electronic components and wiring boards with the above-mentioned anisotropic conductive adhesive can attach electronic components to wiring boards in a short time, this method
There is a problem in that not all of the terminals of the electronic component and each terminal of the wiring board are necessarily electrically connected, resulting in poor reliability.

This is because the distribution of conductive particles in the anisotropic conductive adhesive varies irregularly, whereas LSI
Since the terminal width of electronic components such as chips and liquid crystal display panels is very narrow, there are places in the anisotropically conductive adhesive where the distance between the conductive particles is wider than the terminal width, and the terminal is attached to these places. Coincidentally, in this portion, conductive particles are not interposed between the terminals of the electronic component and the wiring board, and the terminals of this portion are not electrically connected. Note that if the mixing ratio of conductive particles in the anisotropic conductive adhesive is increased, the spacing between the conductive particles will also become smaller, so all terminals can be connected almost reliably. When the mixing ratio of conductive particles in the conductive adhesive is increased,
In areas where the conductive particles are closely spaced, the conductive particles come into contact with each other and short-circuit adjacent terminals.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to efficiently bond electronic components in a time comparable to that of the method of adhesively bonding electronic components with an anisotropic conductive adhesive. Provided is a bonding structure for electronic components and a method therefor, which allows the electronic component to be attached to a wiring board, and also allows each terminal of the electronic component to be reliably electrically connected to each terminal on the board surface without causing any conductive defects. It's about doing.

[Summary of the invention]

That is, in the bonding structure of the electronic component of the present invention, the maximum particle size in the insulating adhesive is between the bonding surfaces of the electronic component and the wiring board, and A bond in which a large number of conductive particles smaller than the width of a narrow terminal and smaller than a terminal spacing between the electronic component and the wiring board are embedded at equal intervals smaller than the width of the narrow terminal. The terminals of the electronic component and the wiring board are electrically connected through the conductive particles, and the electronic component and the wiring board are adhesively bonded using the insulating adhesive. .

Further, in the method for joining electronic components of the present invention, after applying an insulating adhesive to one of the joining surfaces of the electronic component and the wiring board, a mesh screen is placed on top of the insulating adhesive. Conductive particles are dispersed from the mesh screen, and the conductive particles that have entered each opening of the mesh screen are pushed into the insulating adhesive to form a large number of conductive particles in the insulating adhesive. The electronic component and the wiring board are embedded at regular intervals, and then the electronic component and the wiring board are stacked and pressed relatively to bond the electronic component and the wiring board together.

In other words, the present invention adhesively joins electronic components and a wiring board through a bonding material in which conductive particles are embedded in an insulating adhesive. Similar to the method, by simply pressing the electronic component and wiring board relatively and curing the adhesive, it is now possible to bond the electronic component to the wiring board with both terminals electrically connected to each other. At the same time, the maximum diameter of the conductive particles is smaller than the width of the narrower terminal of both terminals of the electronic component and the wiring board, and smaller than the spacing between any of the terminals of the electronic component and the wiring board. , and by embedding the conductive particles in the insulating adhesive at equal intervals smaller than the width of the narrow terminal, at least one conductive particle is necessarily interposed between all the corresponding terminals. This eliminates the occurrence of poor conduction due to variations in the distribution of conductive particles when an anisotropic conductive adhesive is used.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

First, to explain the bonding structure of electronic components, in FIGS. 1 to 3, 1 is a wiring board, and on the surface of this wiring board, as shown in FIG. 3, there are a plurality of wirings 2, 2. ...
is formed. Each wiring 2゜21. ... are led out from the LSI chip joint part of the wiring board 1, and each wiring 2, 2 . The end on the LSI chip joint side of...
A plurality of external circuit connection terminals 11.11. are arranged and formed on the wiring board bonding surface of the LSI chip 10. ...and corresponding LSI chip connection terminals 2a, 2a, respectively.
It is said that... In addition, each of these terminals 2a, 2
The width of a, . . . is the width of each terminal 11 .
11. The width is said to be slightly narrower than the width of...

3, all the LS chips are connected to the LSI chip bonding surface on the first surface of the substrate.
It is a bonding material formed so as to cover the I chip connection terminals 2a, 2a,..., and this bonding material 3 is
A large number of conductive particles 4, 4 .・・・
・It is buried. These conductive particles 4, 4.・・・
- is the external circuit connection terminal 11 of the LSI chip 10
．． 11. ... and the narrow terminals behind the LSI chip connection terminals 2a, 2a, ... on the first side of the wiring board (in this embodiment, the LSI chip connection terminals 2 on the first side of the wiring board
a, 2a,...) width and LSI chip 10
Terminals for connecting external circuits 11.11゜...Particle size smaller than the spacing between the terminals (for example, inside the terminals and the spacing between
~250μ, the particle size is 20~40μ), and this conductive particle 4.4. ...is insulating adhesive 3
The terminals 2a, 2a, . . . are embedded at regular intervals smaller than the width of each of the terminals 2a, 2a, . The conductive particles 4, 4°, etc. include, for example, nickel particles plated with gold, solder particles, copper particles plated with gold or silver, or graphite particles.

Further, in FIG. 3, 2tl, 2b, . . . are for connecting a plurality of external circuits arranged on one side edge of the wiring board 1 on the wiring board bonding surface (terminal arrangement part) of the liquid crystal display panel 20. Terminal 21.21. The display panel connection terminals are arranged in correspondence with the display panel connection terminals 2b, 2b, ..., and the display panel connection terminals 2b, 2b, . . . The largest particle size in the insulating adhesive applied to the display panel connection terminals 2b, 2b.

... and the external circuit connection terminal 21 of the liquid crystal display panel 20
21, . . . and the display panel connection terminals 2b, 2b, . . . and the external circuit connection terminals 21, 21. Conductive particles smaller than any terminal spacing between the narrow width terminals 2b
, 2b, . . . The bonding materials 3 are embedded at equal intervals smaller than the width of the bonding materials 3.

The LSI chip 10 has its respective external circuit connection terminals 11, 11, . ... on the bonding material 3 in correspondence with the IsI chip connection terminals 2a, 2a, ... on the wiring board 1 side, and press this LSI chip 10 and the wiring board 1 relatively. By curing the insulating adhesive 3a of the bonding material 3 in this state,
As shown in the figure, each terminal 11.11 of the LSI chip 10
．． ... and each terminal 2a of the wiring board 1.

2a, . . . and conductive particles 4, 4, .・・・
・They are adhesively bonded by the insulating adhesive 3a in a state where they are electrically connected.

In addition, in FIG. 1 and FIG. 2, 18 is the wiring board 1.
A molding resin such as epoxy resin is used to mold the LSI chip 10 bonded to the LSI chip 10, and this molding resin 18 is applied after the LSI chip 10 is bonded. Also, the second
In the figure, 12 is a base material of the SI chip 10 (in this case, an N-type base material), 13 is a P-type diffusion layer, and 14 is an N-type diffusion layer, and the main surface of the chip on which these diffusion layers 13 and 14 are formed. is an insulating film 15 made of silicon oxide (Si 02 ).
is formed, and a wiring 16 made of aluminum is formed on it.
is formed. This wiring 16 is connected to the insulating WA 15
It is electrically connected to a predetermined diffusion layer among the diffusion layers 13 and 14 through the opening provided in the wiring 16, and the pad portion 16a formed at the lead-out end of the wiring 16 is directly used as the external circuit connection terminal 11. . Reference numeral 17 denotes an insulating protective film made of silicon oxide that covers the wiring 16, and this protective film 17 is formed over the entire surface of the chip except for the terminal 2a portion.

Further, the liquid crystal display panel 20 is pressed so that its wiring board bonding surface is stacked on the bonding material 3 formed on the display panel bonding surface of the wiring board 1, and the insulating adhesive 3a of the bonding material 3 is cured. Thus, it is adhesively bonded to the wiring board 1 in the same manner as the LSI chip 10 described above.

Next, the procedure for bonding electronic components to the wiring board 1 will be described with reference to FIG. 4 for bonding the LSI chip 10.

First, each wiring 2.2. . . . and LSI chip connection terminals 2a, 2a, . . . and display panel connection terminals 2b,
2b, etc. are formed on one side of the wiring board.
An insulating adhesive 3a is applied to a uniform thickness over the entire chip bonding surface as shown in FIG. 4(a). Note that this insulating adhesive 13a is made of the conductive particles 4.4. Depending on the particle size of the largest particle among ..., for example, if the particle size of the largest particle is 40μ, the layer thickness on the terminals 2a, 2a is 40~
Apply to a thickness of about 60μ.

Next, on the coating layer of this insulating adhesive 3a, as shown in FIG.
)) Place the mesh screen 5 as shown in FIG. This mesh screen 5 is made of a resin AiM such as Tetron or a thin plate of stainless steel or the like in which minute openings are formed by etching or the like. . . , which is larger than the particle size of the largest particle and which is connected to external circuit connection terminals ii, il, . . . of the LSI chip 10 and the LS on one side of the wiring board.
The width of the narrower terminal among the I chip connection terminals 2a, 2a, . . . (in this embodiment, the LSI chip connection terminals 2a, 2a, . .

2a... A large number of openings 5a, 5a smaller than the interval between
, . . . are formed at regular intervals smaller than the width of each of the terminals 2a, 2a, .

Note that the thickness of the mesh screen 5 is approximately the same as the particle size of the largest diameter conductive particles 4, or slightly thicker than that.

After this, as shown in FIG. 4(C), conductive particles 4, 4 are applied over the entire surface of the mesh screen 5.
．． ... to a substantially uniform thickness, and then pressurized from above with a pressure jig such as a roller 6 as shown in FIG. 4(d) to open each opening 5a, 5 of the mesh screen 5.
a,... Conductive particles contained within 4.4. ... into the insulating adhesive 3a. In this case, conductive particles 4, 4. If all the particle sizes of ... are the maximum particle size, one conductive particle 4゜4, ... enters each opening 5a, 5a, ... of the mesh screen 5, so that insulating adhesive is formed. One conductive particle at equal intervals in the agent 3a 4.4.
... are pushed in, but the conductive particles 4.4. Since making the particle sizes of the conductive particles 4. and .
4. ...is also used. Therefore, conductive particles 4, 4 . When spraying...
The conductive particles 4 with the largest diameter are located in the openings 5 of the mesh screen 5.
a, and are pushed into the insulating adhesive 3a, and a plurality of small-diameter conductive particles 4 enter the openings 5a of the mesh screen 5 and are pushed into the insulating adhesive 3a. However, the conductive particles 4 pushed into the insulating adhesive 3a
,4. ... are substantially equal intervals.

In this way, conductive particles 4゜4, .
After pushing ..., the conductive particles scattered 4゜4, ...
Conductive particles 4 that are sucked by vacuum suction, pushed into the insulating adhesive 3a, and held by the insulating adhesive 3a
,4. The conductive particles 4° 4, . . . excluding . . . are removed as shown in FIG. 4(e). Note that the removed conductive particles 4, 4°, . . . are collected and reused.

In this way, a large number of conductive particles 4 are contained in the insulating adhesive 3.
,4. After forming the bonding material 3 embedded with..., the mesh screen 5 is removed and the LSI chip 10 is placed on the bonding material 3 with its external circuit connection terminals 11.1.
1... is the LSI chip connection terminal 2a on one side of the wiring board.
, 2a, . . . , and press the LSI chip 10 and wiring board 1 relatively (for example, by
The chip 10 is pressurized) to electrically connect the terminals 11 and 2a of both the LSI chip 10 and the wiring board 1 through the conductive particles 4, and in this pressed state, the insulating adhesive 3a is cured to form an LSI The chip 10 is adhesively bonded to the wiring board 1.

Although the method for bonding the LSI chip 10 has been described here, the liquid crystal display panel 20 is also bonded in the same manner as described above.

The insulating adhesive 3a may be a room temperature curing type, a thermoplastic adhesive generally called a hot melt type, a thermosetting type, or a UV ink. When using a room temperature curing adhesive or UV ink as 3a, electronic components are bonded immediately after forming the bonding material 3 by embedding conductive particles 4゜4,... in the insulating adhesive 3a. Alternatively, a release paper may be placed on the formed bonding material 3 to protect the insulating adhesive 3 from naturally hardening, and the release paper may be peeled off when electronic components are bonded and the electronic components may be bonded immediately. good. In addition, when using a thermoplastic adhesive or thermosetting adhesive called a hot melt type as the insulating adhesive 3a, after forming the bonding material 3, the insulating adhesive is bonded using a drying oven or infrared rays for the previous layer. The agent 3a is dried at a temperature of 70 to 130°C, and when bonding electronic components, the electronic components are stacked on top of the bonding material 3 and the adhesive is heated at a temperature of 100 to 130°C using a press jig or pressure roller.
It may be heated and pressurized at a temperature of 50°C.

Therefore, in the above bonding structure, the electronic components such as the LSI chip 10 and the liquid crystal display panel 20 and the wiring board 1 are bonded by embedding conductive particles 4, 4°, etc. in the insulating adhesive 3a. Since the electronic components and the wiring board 1 are adhesively bonded via the material 3, the terminals of the electronic components and the wiring board 1 can be electrically connected to each other by simply pressing the electronic components and the wiring board 1 relatively and curing the insulating adhesive 3a. It is possible to bond the electronic components in a connected state, and therefore, it is possible to efficiently attach the electronic components in a time comparable to that of the method of adhesively bonding electronic components using an anisotropic conductive adhesive. Further, in this bonding structure, the conductive particles 4, 4. ..., the maximum diameter of electronic components and wiring board 1
The conductive particles 4,4. ···of,
Since they are embedded in the insulating adhesive 3a at regular intervals smaller than the width of the narrow width terminals, at least one conductive particle 4 is necessarily interposed between all the corresponding terminals. Therefore, unlike when an anisotropic conductive adhesive is used, poor continuity does not occur due to variations in the distribution of conductive particles, so there is no possibility of poor continuity between each terminal of the electronic component and each terminal of the wiring board 1. A reliable conductive connection can be made without causing any damage.

Roughly, in the above bonding method, a mesh screen 5 is stacked on the insulating adhesive 3a applied to the surface of the wiring board 1, and the conductive particles 4, 4.・
. . , and conductive particles 4° 4, . . . are scattered at each opening 5a of the mesh screen 5.

5a, . . . Conductive particles 4, 4. Since the bonding material 3 is formed by pushing . . . into the insulating adhesive 3a, the conductive particles 4゜4, .
The distribution of ・can be ensured at equal intervals.

In the above embodiment, the bonding material 3 for adhesively bonding electronic components is formed on the wiring board 1 side, but as shown in FIG. Alternatively, the external circuit connection terminals 11.11. of the LSI chip 10 may be formed on the surface. . . may have a structure as shown in FIG. 5, in which bumps 16b are formed by plating gold or the like on the pad portion 16a shown in FIG. 2.

Further, in the above embodiment, the bonding material 3 is interposed over the entire bonding surface between the wiring board 1 and the electronic component, but the bonding material 3 may be interposed only in the terminal arrangement portion. , instead of applying it to the wiring board 1 or electronic components,
It may be formed into a sheet shape in advance and sandwiched between the wiring board 1 and the electronic component.

〔Effect of the invention〕

According to this invention, since electronic components and wiring boards are adhesively bonded via a bonding material in which conductive particles are embedded in an insulating adhesive, electronic components can be adhesively bonded using an anisotropic conductive adhesive. In addition to being able to efficiently attach electronic components to a wiring board in as short a time as the method, the maximum diameter of the conductive particles can be adjusted to the width of the narrower terminal of both the electronic component and the wiring board. By making the spacing between the narrow width terminals smaller than the width of the narrow terminals and embedding the conductive particles in an insulating adhesive at equal intervals smaller than the width of the narrow width terminals, Since at least one conductive particle is always interposed, it is possible to eliminate the occurrence of poor conduction due to variations in the distribution of conductive particles when using an anisotropic conductive adhesive, and to ensure that each terminal of an electronic component can be reliably electrically connected to each terminal on the board surface without causing electrical continuity defects.

[Brief explanation of drawings]

Figures 1 to 4 show an embodiment of this invention.
Figure 1 is an enlarged cross-sectional view taken along the line B-B in Figure 3, Figure 2 is an enlarged cross-sectional view taken along the line A-A in Figure 1, Figure 3 is a perspective view of the wiring board and electronic components, FIG. 4 is a sectional view taken along a terminal arrangement line of a wiring board showing a method for joining electronic components in the order of steps. FIG. 5 is a sectional view taken along the terminal arrangement line of a wiring board and electronic components, showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Wiring board, 2... Wiring, 2a... LSI chip connection terminal, 2b... Display panel connection terminal, 3
... Bonding material, 3a... Insulating adhesive, 4... Conductive particles, 5... Mesh screen, 5a... Opening, 6... Roller, 10... LSI chip, 11...
・External circuit connection terminal, 20...Liquid crystal display panel, 2
1...Terminal for external circuit connection. Applicant's representative Patent attorney Takehiko Suzue Figure 1 (%3121) B-BaX Omae ffoE2]) Figure 2 Figure 3 (The Hz of the shock-jumping board and the Kasumi 4-mark product!> Figure 4 Po [0

Claims (2)

[Claims] (1) An electronic component with a plurality of external circuit connection terminals formed on the surface to be bonded to the wiring board is directly bonded to a wiring board surface with a plurality of electronic component connection terminals formed thereon corresponding to each terminal of the electronic component. In the bonding structure of electronic components, the largest particle size in the insulating adhesive is between the bonding surfaces of the electronic component and the wiring board, and A bonding material is interposed in which a large number of conductive particles smaller than the width of the terminal and smaller than the spacing between any of the terminals of the electronic component and the wiring board are embedded at equal intervals smaller than the width of the narrow terminal. the terminals of the electronic component and the wiring board are electrically connected through the conductive particles, and the electronic component and the wiring board are adhesively bonded using the insulating adhesive. Joint structure of parts. (2) An electronic component having a plurality of external circuit connection terminals formed on the surface to be bonded to the wiring board is directly bonded to a wiring board surface having a plurality of electronic component connection terminals formed thereon corresponding to each terminal of the electronic component. In the method for bonding electronic components, after applying an insulating adhesive to one of the bonding surfaces of the electronic component and the wiring board, terminals of both the electronic component and the wiring board are coated on the insulating adhesive. a mesh screen in which a large number of openings smaller than the width of the narrower terminals and smaller than any terminal spacing between the electronic component and the wiring board are formed at equal intervals smaller than the width of the narrower terminals; The conductive particles that have entered each opening of the mesh screen are pushed into the insulating adhesive to form a large number of conductive particles in the insulating adhesive. embedding conductive particles at regular intervals, and then stacking the electronic component and the wiring board and pressing them relatively to adhesively join the electronic component and the wiring board. Method.