JP5075569B2 - Wiring board and IC chip mounting method - Google Patents

Description

  The present invention relates to a technique for mounting an IC chip on a wiring board such as a liquid crystal display device.

  Conventionally, for example, an anisotropic conductive adhesive film has been used as means for mounting an IC chip on a wiring (glass) substrate such as a liquid crystal display device (see, for example, Patent Document 1).

  In order to mount an IC chip using this anisotropic conductive adhesive film by the COG (Cip On Glass) method, anisotropic conductive adhesion is performed between the connection terminals (bumps) of the IC chip and the connection electrodes of the wiring board. Thermocompression bonding is performed by interposing a film and heating and pressing the IC chip with a thermocompression bonding head.

However, conventionally, a connection failure may occur with respect to a specific bump among the bumps provided on the IC chip.
For example, as shown in FIG. 8 (a), the bumps 103 and 104 provided on the edge of the chip body 102 of the IC chip 101 are poorly connected to the bumps (in the ellipses A and B) provided on the short side. May occur.

Further, as shown in FIG. 8B, among the bumps 203 to 205 provided on the long side portion of the chip body 202 of the IC chip 201, the IC chip 201 in which the bumps are provided in a staggered manner on one long side. In such a case, connection failure may occur in the outer bump 204 (in the ellipse C).
JP-A-8-7658

  The present invention has been made to solve the above-described problems of the prior art, and it is possible to connect an IC chip using an anisotropic conductive adhesive capable of improving conduction reliability without causing a connection failure. The purpose is to provide technology.

In order to achieve the above object, the invention according to claim 1 is a wiring substrate having a plurality of connection electrodes on a connection side surface of a substrate body, on which an IC chip is mounted by an anisotropic conductive adhesive. Among the plurality of connection electrodes, the height of the connection electrode in the region specified in advance is set higher than the heights of the other connection electrodes.
The invention according to claim 2 is the invention according to claim 1, wherein the connection side surface of the substrate body is formed in a rectangular shape, and the plurality of connection electrodes are provided at the edge of the connection side surface of the substrate body. Among the plurality of connection electrodes, the height of the connection electrode provided at the short side edge of the connection side is higher than the height of the connection electrode provided at the long side edge of the connection side. is there.
According to a third aspect of the invention, in the first aspect of the invention, the plurality of connection electrodes are provided in a plurality of rows along the edge of the connection side surface, and the connection among the plurality of rows of connection electrodes. The height of the connection electrode provided outside the edge of the side surface is set higher than the height of the connection electrode provided inside the edge of the connection side surface.
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a difference between a height of the connection electrode in the predetermined area and a height of the other connection electrode is used. It is 5% to 95% of the particle size of the conductive particles of the anisotropic conductive adhesive.
According to a fifth aspect of the present invention, the wiring board is a glass substrate for a liquid crystal display device.
According to a sixth aspect of the present invention, an anisotropic conductive adhesive is disposed between the IC chip on which the projecting connection electrode is formed and the wiring substrate according to any one of the first to fifth aspects, and heating is performed. And an IC chip mounting method including a step of bonding the wiring board and the IC chip and electrically connecting corresponding electrodes by applying pressure.

In the case of the present invention, among the plurality of connection electrodes provided on the connection side surface of the substrate body, a region specified in advance (for example, a short side edge region of the rectangular connection side surface or an edge portion of the connection side surface) Since the height of the connection electrode in the outer region of the edge when the mounting terminals are provided in a plurality of rows along the mounting terminals is higher than the height of the other connection electrodes, an anisotropic conductive adhesive is used. Thus, when thermocompression bonding is performed, the specific conductive particles, which are not sufficiently crushed by the conventional technology, can be sufficiently compressed.
As a result, according to the present invention, since the compressed state of the conductive particles on each mounting terminal of the IC chip can be made uniform, the conduction reliability can be improved in various types of IC chips.
In particular, according to the present invention, since the conduction reliability can be improved without using conductive particles having a large diameter, it is useful for an IC chip having fine pitch bumps.

  ADVANTAGE OF THE INVENTION According to this invention, the connection technique of the IC chip using the anisotropic conductive adhesive which can improve conduction | electrical_connection reliability without generating a connection failure can be provided.

Hereinafter, preferred embodiments of the mounting method of the present invention will be described with reference to the drawings.
As will be described later, the anisotropic conductive adhesive 7 used in the present invention is one in which conductive particles 9 are dispersed in an insulating adhesive resin 8. It can be applied to any of the shapes.

  1A and 1B are schematic views showing examples of an IC chip and a wiring board used in the present invention. FIG. 1A is a plan view and FIG. 1B is a front view of the wiring board. . FIGS. 2A and 2B and FIGS. 3A and 3B are explanatory views showing the principle of the present invention.

  As shown in FIGS. 1 (a) and 1 (b), an IC chip 1 used in the present invention has, for example, a rectangular-shaped chip body 2, and its connection side surface 2a is formed in a rectangular shape.

  A plurality of mounting terminals 3, 4, and 5 using bumps as connection electrodes are provided at the edges (long side and short side) of the connection side surface 2 a of the IC chip 1 with a predetermined pitch.

  In the case of this example, the mounting terminals 3, 4, 5 are made of Au (gold) on electrode parts 20 made of patterned Al (aluminum), as shown in FIGS. 3A and 3B, for example. The bumps 40 and 50 are formed. In FIGS. 3A and 3B, reference numeral 21 denotes a passivation film.

Here, in order to form the Au bump on the Al electrode portion, for example, a known plating method described below (see, for example, Japanese Patent No. 2936680) can be used.
That is, in the plating method, an Si substrate on which an Al wiring (electrode part) and an insulating film are formed is prepared, an opening for connecting the Al wiring to the outside is formed in the insulating film, and Ti (titanium) is formed on the entire surface. ) Is sputtered to form a Ti film, and Pd (palladium) is sputtered to form a Pd film. Next, a resist is deposited thereon and patterned to form a resist mask having openings for forming Au bumps.
Further, Au plating is performed on the Pd film from the above-mentioned openings to form an Au plating layer, and then the above-described resist mask is removed, and the Pd film and Ti film are etched using the gold plating layer as a mask. . As a result, an Au bump formed on the Al electrode portion is obtained.

On the other hand, the wiring substrate 11 of this example has a substrate body 12 made of, for example, glass, and connection electrodes 13 and 14 corresponding to the mounting terminals 3, 4 and 5 of the IC chip are provided on the connection side surface, that is, the connection region 12a. , 15 are provided at a predetermined pitch.
Here, the connection region 12a of the substrate body 12 is formed in a rectangular shape, and the connection electrodes 13 and 15 are provided on the long side edges thereof, respectively. A connection electrode 14 is provided on the short side edge of the substrate body 12.

Here, when the wiring substrate 11 is a glass substrate for a liquid crystal display device, the connection electrode 13 on one long side edge and the connection electrode 14 on the short side edge of the connection region 12a are, for example, Al. It can be formed by etching using sputtering and photolithography.
The connection electrode 15 on the other long side edge can be formed by sputtering using ITO and etching by photolithography.

  In the present invention, among the plurality of connection electrodes, the height of the connection electrode in the region specified in advance is set higher than the heights of the other connection electrodes.

  In the present embodiment, as shown in FIGS. 1A and 1B, the connection electrodes 14 provided on the short side edges (regions indicated by ellipses C and D) of the connection region 12a of the wiring board 11 are provided. The height is configured to be higher than the height of the connection electrodes 13 and 15 provided on the long side edge of the connection region 12a.

  In the case of the present invention, the method of making the height of the connection electrode 14 on the short side edge of the wiring board 11 higher than the height of the connection electrodes 13 and 15 on the long side edge is not particularly limited. From the viewpoint of simplicity of the manufacturing process, for example, as shown in FIG. 3B, it is preferable to provide a metal raised portion 14a on the connection electrode 14 to make the electrode portion multilayer.

  In this case, as a method of forming the raised portion 14a, for example, etching using aluminum and etching by photolithography can be employed.

  Thus, the wiring substrate 11 is obtained in which the height of the connection electrode 14 at the short side edge of the wiring substrate 11 is higher than the height of the connection electrodes 13 and 15 at the long side edge by the raised portion 14a. be able to.

  The principle of the present invention will be described below with reference to FIGS. 2 (a) and 2 (b) and FIGS. 3 (a) and 3 (b). Here, a case where the IC chip 1 is mounted on the wiring board 11 is considered. Also, one of the connection electrodes 13 and 15 on the long side edge will be described as an example.

  When the wiring board 11 is mounted, as shown in FIG. 2A, the anisotropic conductive adhesive 7 is disposed between the wiring board 11 and the IC chip 1 and thermocompression bonding is performed. Heating and pressing are performed from the chip 1 side.

  In this case, the reached temperature of the IC chip 1 is about 200 to 250 ° C., but the reached temperature on the wiring board 11 side is about 100 to 150 ° C., which is lower than that of the IC chip 1. It is in an extended state. For this reason, the shrinkage of the chip body 2 of the IC chip 1 is large after cooling after mounting, for example, as shown in FIG. 2B, the warp of the IC chip 1 becomes larger than the wiring substrate 11, and as a result, Warpage occurs in the entire mounting part.

  In this state, stress is easily applied to the short side edge 2b of the edges of the connection side surface 2a of the IC chip 1, so that the conductive particles 9b of the anisotropic conductive adhesive 7 as shown in FIG. Is smaller than the conductive particles 9 in other regions (long side edge in this example), and the deformation (compression) rate of the conductive particles 9b tends to be insufficient.

  Therefore, as shown in FIG. 3B, by providing a raised portion 14a on the connection electrode 14 at the short side edge portion 12b of the connection region 12a of the wiring board 11, the height of the connection electrode 14 is increased. The height is higher than the height of the connection electrode 15 at the long side edge of the connection region 12a.

  Thereby, between the IC chip 1 and the wiring board 11, the space | interval between the mounting terminal 4 and the connection electrode 14 of the short side part side edge of the connection area | region 12a is set between the connection electrode 15 and the mounting terminal 5 of the long side part side edge. Therefore, the compression rate can be made uniform by pressing the conductive particles 9 with a uniform force at each mounting terminal portion at the edge of the connection side surface 2a of the IC chip 1.

  In the case of the present invention, the difference in height between the connection electrodes 13 and 15 on the long side portion side edge and the connection electrode 14 on the short side portion side edge in the wiring board 11 is not particularly limited. From the viewpoint of making the compressed state of the conductive particles 9 uniform and improving the conduction reliability, it is preferably 5% to 95% of the particle size of the conductive particles 9, and more preferably 30% to 60%.

  Specifically, for example, when the particle diameter of the conductive particles 9 is 3 μm to 5 μm, the height difference between the connection electrodes 13 and 15 and the connection electrode 14 can be set to 0.5 μm to 3 μm.

In this case, the elastic modulus of the conductive particles 9 is more effective when a range of ^{100kgf / mm 2 ~1000kgf / mm 2} .

  4 (a) (b), FIG. 5 (a) (b) and FIG. 6 (a) (b) show other embodiments of the present invention. These parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 4A and 4B, the IC chip 1A used in the present embodiment has mounting terminals 3, 4A, 5 as connection electrodes on the long side edge of the connection side surface 2a of the chip body 2. Is provided.

  Then, on one of the long side edges of the connection side surface 2a of the IC chip 1A, two rows of mounting terminals 3 and 4A are arranged in a staggered pattern along the long side edge.

  On the other hand, the wiring board 11A of the present embodiment has connection electrodes 13, 14A, corresponding to the mounting terminals 3, 4A, 5 of the IC chip 1A described above, on the long side edge of the connection region 12a of the chip body 12, respectively. 15 is provided.

  Here, on one of the long side edges of the connection region 12a of the wiring board 11A, two rows of connection electrodes 13 and 14A are arranged in a staggered pattern along the long side edge.

  And among these connection electrodes 13, 14 </ b> A, 15, the height of the connection electrode 14 </ b> A (a region indicated by an ellipse E in FIG. 4A) provided outside one long side edge of the connection region 12 a is It is comprised so that it may become higher than the height of the connection electrodes 13 and 15 provided inside this long side edge part.

In this case, the method of making the height of the connection electrode 14A outside the long side edge of the connection region 12a of the wiring board 11A higher than the height of the connection electrode 13 inside the long side edge is the same as in the above embodiment. The method can be adopted.
That is, in the case of the present invention, although not particularly limited, from the viewpoint of simplicity of the manufacturing process, as shown in FIGS. 4B and 6B, raising the connection electrode 14A with a metal. It is preferable to provide the part 14a to make the electrode part multilayer.

  In the present embodiment, no connection electrode is provided on the short side edge of the connection region 12a of the wiring board 11A.

  In the wiring substrate 11A in which the two rows of connection electrodes 13 and 14A are arranged in a zigzag pattern along the long side edge, when heating and pressurization are performed from the IC chip 1A side during mounting, FIG. a) As shown in (b), the central portion of the chip body 2 tends to sink compared to the long side edge.

  For this reason, after mounting the IC chip 1A, a difference occurs in the height between the central portion of the chip body 2 and the long side edge. This difference is particularly large (approximately several μm) at the long side edge 2c on the side where the two rows of mounting terminals 3 and 4A are provided.

  Here, as shown in FIG. 6A, when the heights of the connection electrodes 13 and 14A of the wiring board 11A are equal, the pressing force on the conductive particles 9c of the connection electrodes 14A on the outer edge of the long side is reduced. The conductive particles 9 are smaller than the other conductive particles 9, and the deformation (compression) rate of the conductive particles 9c is insufficient.

  Therefore, in the present embodiment, as shown in FIG. 6B, the height of the connection electrode 14A outside the long side edge 12c of the connection region 12a of the wiring board 11A is set, and the raised portion 14a is formed thereon. By providing, it is made higher than the height of the connection electrode 13 inside the long side edge 2c.

  As a result, as in the above embodiment, the distance between the mounting terminal 4A and the connection electrode 14A can be made equal to the distance between the mounting terminal 5 and the connection electrode 15 between the IC chip 1A and the wiring board 11A. The compression rate can be made uniform by pressing the conductive particles 9 with a uniform force at each mounting terminal portion at the edge of the wiring board 11A.

  In the case of the present invention, the difference in height between the connection electrode 14A and the connection electrodes 13 and 15 in the wiring board 11A is not particularly limited. From the viewpoint of improving the resistance, the difference in height between the connection electrode 14A and the connection electrodes 13 and 15 is preferably 5% to 95% of the particle diameter of the conductive particles 9.

  Specifically, for example, when the particle diameter of the conductive particles 9 is 3 μm to 5 μm, the difference between the connection electrode 14A and 13 and 15 can be 0.5 μm to 3 μm.

In this case, the elastic modulus of the conductive particles 9 is more effective when a range of ^{100kgf / mm 2 ~1000kgf / mm 2} .

The present invention is not limited to the above-described embodiment, and various changes can be made.
For example, the connection electrodes that increase the height among the plurality of connection electrodes are not limited to all those arranged at the edge (short side or long side) of the connection side as in the above-described embodiment. Some of the connection electrodes may be used.

  For example, as shown in FIG. 7, an IC chip 1B in which a plurality of connection electrodes 3 and 5 are formed on the long side edge of the connection region 2a, and a plurality of connection electrodes 13 on the long side edge of the connection region 12a. When the wiring board 11B on which is formed is used, the height of any of the connection electrodes 13B and 15B (for example, corresponding to the mounting terminals 3B and 5B having a low height of the IC chip 1B) on the wiring board 11B is set respectively. It can be made higher than the height of the other connection electrodes 13 and 15.

  In addition, various changes can be made according to the IC chip, such as making the height of the connection electrodes at the corners of the connection side surface of the chip body higher than the connection electrodes in other regions.

  Further, regarding the method of increasing the height of the connection electrode in a specific region, in addition to the above-described method of providing a raised portion on the connection electrode to form a multilayer, for example, the connection electrode is initially formed thick, The surface layer portion of the connection electrode in a region other than the region where the height is increased may be removed by etching or the like to reduce the electrode height in the region.

  Furthermore, the present invention can be applied not only to glass wiring boards for liquid crystal display devices but also to various types of wiring boards.

  Examples of the present invention will be described below in detail together with comparative examples.

[Creation of anisotropic conductive adhesive film]
As an insulating adhesive resin, 30 parts by weight of an epoxy resin (EP828 manufactured by Japan Epoxy Resin Co., Ltd.), 40 parts by weight of a phenoxy resin (PKHH manufactured by InChem), 30 parts by weight of an epoxy curing agent (HX3941HP manufactured by Asahi Kasei Co., Ltd.), conductive particles (Sekisui Chemical) 25 parts by weight of an average particle size of 3 μm manufactured by the company was dissolved and mixed with a mixer using toluene / ethyl acetate as a solvent to obtain a paste.

  And the paste mentioned above was apply | coated on PET film which performed the peeling process, it heated for 8 minutes with the electric oven set to 70 degreeC, and the anisotropic conductive adhesive film whose dry film thickness is 20 micrometers was created.

<Example 1>
The IC chip (1A) having the staggered mounting terminals shown in FIGS. 4 (a) and 4 (b), and the staggered Al connection electrode formed on a transparent glass plate having a thickness of 0.5 mm so as to correspond thereto. A rectangular wiring board (11A) was used.

Here, the height of the Al connection electrode (14A) on the outer side edge of one long side of the wiring board (11A) is set to 1 μm by multilayering of the wiring film, and the Al connection electrode ( The height of 13) was 0.2 μm.
On the other hand, the height (thickness) of the ITO connection electrode (15) on the other long side edge side of the wiring board was set to 0.2 μm.

The widths of the connection electrodes (14A) and (13) on the outer and inner side edges of the long side were 20 μm, and the pitch between the connection electrodes was 25 μm.
On the other hand, all the IC chip mounting terminals were formed to a height of 15 μm.

<Comparative Example 1>
The height of the connection electrode (14A) on the outer edge of the long side of the wiring board was set to 0.2 μm, and all the heights of the connection electrodes were made the same. Otherwise, the wiring board having the same configuration as in Example 1 was used. .

<Example 2>
An IC chip (1) having mounting terminals in a straight arrangement shown in FIGS. 1 (a) and 1 (b), and an Al connection electrode in a straight arrangement were formed on a transparent glass plate having a thickness of 0.5 mm so as to correspond to this. A wiring board (11) was used.
Here, the height of the Al connection electrode (14) at the short side edge of the wiring board (11) is set to 1 μm by multilayering the wiring film.
On the other hand, the heights of the Al connection electrode (13) and the ITO connection electrode (15) on the long side edge portion side of the wiring board were each 0.2 μm.

  In the case of this example, the width of the connection electrode (14) on the short side edge and the connection electrode (13, 15) on the long side edge was 30 μm, and the pitch between the connection electrodes was 50 μm.

<Comparative example 2>
The height of the connection electrodes (13, 14, 15) on the long side edge portion and the short side edge portion side is set to 0.2 μm so that all the connection electrode heights are the same. A wiring board having a configuration was used.
<Example 3>
An IC chip (1B) having mounting terminals arranged in a straight line shown in FIG. 7 and a wiring board (11B) in which Al connection electrodes arranged in a straight line are formed on a transparent glass plate having a thickness of 0.5 mm so as to correspond thereto. Was used.
Here, the height of the specific mounting terminals (3B, 5B) of the IC chip (1B) is 14 μm, and is 1 μm lower than the heights of the other mounting terminals (3, 5).
On the other hand, for the wiring board (11B), the heights of the Al connection electrodes (13B, 15B) at both long side edges corresponding to the mounting terminals (3B, 5B) formed with a low height of the IC chip (1B). Was made 1 μm by multilayering the wiring film.
On the other hand, the heights of the other Al connection electrode (13) and the ITO connection electrode (15) on the side of the long side edge of the wiring board were each 0.2 μm.

  In the case of this example, the width of the connection electrodes (13, 15) of the wiring board was 30 μm, and the pitch between the connection electrodes was 50 μm.

<Comparative Example 3>
The height of the connection electrodes (13, 15) on both long side edges was set to 0.2 μm, and the heights of all the connection electrodes were the same. Otherwise, a wiring substrate having the same configuration as in Example 2 was used.

[Evaluation]
What was mentioned above as an anisotropic conductive adhesive film was used, and each IC chip was thermocompression-bonded on each wiring board mentioned above.

  In this case, the pressure bonding conditions were a temperature of 200 ° C., a pressure of 30 MPa, and a time of 10 seconds. Further, aging was performed for 500 hours under the conditions of a temperature of 85 ° C. and a relative humidity of 85%, and a continuity test between the mounting terminals was performed. . The results are shown in Tables 1, 2, and 3.

  On the other hand, the collapsed state of the conductive particles in the IC chip after thermocompression bonding was visually observed using a microscope.

  In this case, the case where the conductive particles are uniformly crushed is indicated by “◯”, and the state where the conductive particles are not uniformly crushed between the mounting terminals and the state where the conductive particles are not sufficiently crushed is indicated by “X”.

[Evaluation results]
About Example 1, Example 2, and Example 3, after aging, it is controlled by the resistance rise of 8 ohms or less, the long side edge part outer side (Example 1), the short side (Example 2), and It can be seen that the conduction between the mounting terminals of Example 3 in which the low bumps are formed is stable for a long time.

  Further, it was confirmed that the conductive particles were uniformly crushed between the mounting terminals and the connection electrodes.

  On the other hand, in Comparative Example 1, a resistance increase of 34Ω was observed after aging, and there were portions where the degree of collapse of the conductive particles was not sufficient on the mounting terminals outside the long side edge.

Further, in Comparative Example 2, a resistance increase of 39Ω was observed after aging, and there were portions where the conductive particles were not sufficiently crushed on the mounting terminals on the short side edge.
Furthermore, in Comparative Example 3, a resistance increase of 42Ω was observed after aging, and there was a portion where the degree of collapse of the conductive particles was not sufficient on the mounting terminal whose height was lowered.
From the above, the effect of the present invention could be verified.

(A): It is a schematic plan view which shows the example of the IC chip and wiring board used for this invention. (B): It is a front view of the wiring board. (A) (b): It is explanatory drawing which shows the principle of this invention. (A) (b): It is explanatory drawing which shows the principle of this invention. (A): It is a schematic plan view which shows the other example of the IC chip and wiring board used for this invention. (B): It is a side view of the same wiring board. (A) (b): It is explanatory drawing which shows the principle of this invention. (A) (b): It is explanatory drawing which shows the principle of this invention. It is a schematic plan view which shows the other example of the IC chip and wiring board used for this invention. (A): It is a schematic plan view which shows the external appearance structure of the IC chip which concerns on a prior art example. (B): It is a schematic plan view which shows the external appearance structure of the IC chip based on another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 IC chip 2 Chip body 2a Connection side surface 2b Short side edge 3,4 Mounting terminal 7 Anisotropic conductive adhesive 9 Conductive particle 11 Wiring board 12 Substrate body 12a Connection area

Claims (6)

A wiring board having a plurality of connection electrodes on a connection side surface of a substrate body, and an IC chip is mounted by an anisotropic conductive adhesive,
A wiring board in which a height of a connection electrode in a predetermined region among the plurality of connection electrodes is higher than a height of another connection electrode.   The connection side surface of the substrate body is formed in a rectangular shape, and the plurality of connection electrodes are provided at the edge portion of the connection side surface of the substrate body, and the short side edge portion of the connection side surface among the plurality of connection electrodes. The wiring board according to claim 1, wherein a height of the connection electrode provided on the connection side is set higher than a height of the connection electrode provided on a long side edge of the connection side surface.   The plurality of connection electrodes are provided in a plurality of rows along the edge of the connection side surface, and among the connection electrodes of the plurality of rows, the height of the connection electrode provided outside the edge of the connection side surface is The wiring board according to claim 1, wherein the wiring board is made higher than a height of a connection electrode provided inside an edge of the connection side surface.   The difference between the height of the connection electrode in the predetermined region and the height of the other connection electrode is 5% to 95% of the particle size of the conductive particles of the anisotropic conductive adhesive to be used. 4. The wiring board according to any one of items 1 to 3.   The wiring substrate according to any one of claims 1 to 4, wherein the wiring substrate is a glass substrate for a liquid crystal display device. An anisotropic conductive adhesive is disposed between the IC chip on which the projecting connection electrode is formed and the wiring substrate according to any one of claims 1 to 5,
An IC chip mounting method including a step of bonding the wiring board and the IC chip and electrically connecting corresponding electrodes by heating and pressing.

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