JP2000315855A - Facedown mounting substrate and facedown mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always realize stable electrical continuity, without being affected by fluidity of anisotropic conductive paste(ACP) and degree of dispersion of conducting particles. SOLUTION: In this facedown mounting substrate, a terminal 12 formed in a substrate 7 is covered with a protective film 11 so that an aperture part is formed, a bump 1 of a metal protruding part is formed in an IC element 5, and electrical connection is made by interposing conductive adhesive agent in which conducting particles 4 are dispersed. A second connection surface 12a of the aperture part is set larger than a first connection surface 1a of the bump 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a face-down mounting board and a face-down mounting method, and more particularly to a flip-chip mounting method which is a face-down mounting using an anisotropic conductive adhesive (hereinafter, also referred to as ACP). The present invention relates to a technique adapted to a structure of a wiring board and an IC to be used.

[0002]

2. Description of the Related Art A flip-chip, which is a face-down mounting method, has been known as a semiconductor mounting technique. This method was developed as a semiconductor mounting method for large-sized computers, but in recent years this mounting method has been applied to general-purpose and small-sized semiconductor mounting substrates in order to respond to the demand for more pins and smaller drive ICs for electronic devices. Has also been introduced.

For example, in a driver substrate for a thermal line print head, a driver IC for individually driving a heater, which is a heating portion of the head, is provided with a driver IC of 3,000 to 3,000.
Since it is necessary to mount 4000 bits (bits),
The heater and the terminal of the driver IC are connected for each bit, but the flip-chip method using solder bumps is adopted because they can be connected collectively.

Further, in mounting a driver on a liquid crystal display device, an anisotropic conductive film (hereinafter, also referred to as ACF) is used on an IC substrate on a glass substrate around the panel due to the necessity of miniaturizing the display device. A flip-chip mounting method has been used in which a driver IC having a metal projection (hereinafter, also referred to as a bump) formed thereon is mounted.

In order to perform the above-mentioned batch soldering, a reflow soldering process is used. The condition of this soldering is that the substrate is heated in two stages at about 100 ° C. and 180 ° C., and the final heating is performed at 240 ° C. for 10 to 20 seconds.
Heating for c is performed. In the case of connection using a flip chip bonding machine, the melting point of the solder is 183.
Heated above 200 ° C for ° C.

In the case of ACF, since it has been hardened to some extent in the previous step, it needs to be reflowed as a resin.
It was necessary to apply a high temperature of 0 ° C. or higher, and it was inevitable that the processing conditions would be high.

According to recent small liquid crystal display devices, area centers on which color filters are mounted, etc.
Since new electronic devices that require a connection at a temperature of less than ° C. are attracting attention, the effects of high temperatures on devices and materials when using such new electronic devices are not negligible.

In view of the above, a technique of mounting a substrate such as an ACF by using an anisotropic conductive paste (ACP) in which conductive particles are dispersed in an epoxy adhesive to enable a low temperature has been attracting attention in recent years. .

[0009]

However, the above-mentioned ACP is initially in a liquid state. With reference to the drawings, a connection method using a conventional ACP will be described.

FIG. 6A is a sectional view showing a connection state, in which a gold bump 101 is formed on a silicon base 105 and an anisotropic conductive paste (ACP) 3 is interposed. The conductive particles 4 in the ACP are sandwiched between the wirings 112 formed on the substrate 107 so as to achieve electrical conduction. In this case, when the thermocompression bonding is performed after the application of the ACP on the substrate, the conductive particles 4 may flow out around the bumps 101 and the terminals 112 together with the liquid adhesive, and the conductive particles 4 may not remain. From that
There is a problem of not being electrically connected.

FIGS. 6B and 6C are cross-sectional views showing the connection state, in which the terminal 112 is surrounded by a protective film 111. In this case, since the protective film 111 surrounds the peripheral portion of the terminal 112, a space 112a is formed. In the space 112a, the conductive particles 4 are sufficiently filled as shown in FIG. It has been pointed out that it cannot be crushed and cannot be conducted.

Conventionally, in order to solve such a problem, measures have been taken by optimizing the application amount of ACP, pressurization, heating conditions and pressurization timing.

However, since the fluidity of the anisotropic conductive paste (ACP) and the degree of dispersion of the conductive particles are likely to vary, the stability is lacking. Measures were desired.

Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems.
P), regardless of the fluidity and the degree of dispersion of the conductive particles,
It is an object of the present invention to provide a face-down mounting board and a face-down mounting method that can always stably establish electrical conduction.

[0015]

According to the face-down mounting substrate and the face-down mounting method of the present invention, in order to solve the above-mentioned problems and achieve the object, a wiring formed on the substrate and a protection covering the wiring are provided. For a film and a wiring board provided with terminals formed at the openings of the protective film, a metal layer is provided on the terminal on the IC side and a metal protrusion is provided on the metal layer,
A face-down mounting board for bonding a surface of the substrate, on which wiring and terminals are provided, and a surface of the IC, on which metal projections are provided, with a conductive adhesive, and simultaneously making an electrical connection between the terminals, The size of the opening of the protective film of the connection terminal on the substrate side is larger than the size of the metal protrusion.

Also, a wiring formed on the substrate, a protective film covering the wiring, and a wiring substrate provided with terminals formed in the opening of the protective film or a protective film for protecting the wiring substrate on the opening of the protective film. A substrate on which a projection that is more convex than the film is formed;
A metal layer is provided on the terminal on the side and a metal protrusion is provided on the metal layer, and the surface of the substrate on which the wiring and the terminal are provided and the surface on which the metal protrusion is provided on the IC side are bonded with a conductive adhesive. ,
At the same time, in a face-down mounting board which takes electrical connection between terminals, a bank is arranged so as to surround a projection of the connection terminal on the wiring board side or an opening of the protective film on the wiring board side. I have.

Further, the height of the bank surrounding the opening or the terminal protruding from the protective film on the substrate side is smaller than the height of the metal projection on the IC side.

Further, the height of the opening or the height of the bank is set lower than the height of the first connection surface.

Further, the opening or the bank is characterized by forming at least one cut.

Further, the cut is provided at an intermediate part or a corner part.

Further, the opening or the bank is formed of an organic resin material.

Further, the organic resin material is a photosensitive organic resin material.

Further, the substrate is characterized in that a multi-terminal drive driver IC for driving a thermal line head or for a liquid crystal display device is mounted as the IC element.

Further, the terminal formed on the substrate is covered with a protective film so as to have an opening, a metal projection is formed on the terminal of the IC element, and a conductive film is formed between the opening and the metal projection. A face-down mounting method in which a conductive adhesive in which particles are dispersed is interposed, and the terminal and the metal protrusion are electrically connected to each other by heating and pressurizing, wherein the metal protrusion has a lower surface than the first connection surface. The second connection surface of the opening is set large so that the conductive particles are reliably interposed between the first connection surface and the second connection surface.

Further, the terminal formed on the substrate is covered with a protective film so as to have an opening, and a projection which is protruded from the protective film is formed at an edge of the opening, so that the terminal of the IC element is formed. A metal projection is formed, and a conductive adhesive in which conductive particles are dispersed is interposed between the opening and the metal projection. By heating and pressing, between the terminal and the metal projection. A face-down mounting method for electrical connection,
The second connection surface of the opening is set to be larger than the first connection surface of the metal protrusion, and a bank is formed around the protrusion, and the conductive particles are formed in a range surrounded by the bank. It is characterized in that it is reliably interposed between the first connection surface and the second connection surface.

Further, the height of the opening or the height of the bank is set lower than the height of the first connection surface.

The opening or the bank is
At least one cut is formed, and an excessive amount of the conductive adhesive can be removed from the cut.

According to the above configuration, the second connection surface is surrounded by the opening formed by the protective film on the substrate side, and the first connection surface is set so as to be positioned inside the second connection surface. Since the conductive particles at the time of heating and pressurization are stopped inside the opening, the outflow is prevented, and the conductive particles remain reliably to enable electrical conduction.

Further, an IC is provided around the opening on the substrate side.
The formation of a bank lower than the height of the metal projection of the element further suppresses the outflow of conductive particles, and the formation of a cut in the bank restricts the outflow of conductive particles appropriately and is unnecessary for bonding. Such a liquid portion is discharged to the outside from the cut, and the conductive particles remain more reliably between the bump and the wiring, so that the connection can be reliably performed.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a wiring portion and a passivation film of an IC according to a first embodiment of the present invention.
FIG. 4 is a diagram illustrating a state in which an IC element is flip-chip mounted on a substrate.

In FIG. 1, an IC element 5 mounted on a wiring board 7 includes an aluminum pad 6, a barrier metal 2 made of a titanium metal and a lead alloy, and a passivation film 1.
0 is formed as shown in the figure, and a bump 1 made of gold, which is a metal protrusion, is formed on an aluminum pad 6. The bump 1 is connected to another electronic element on a wiring board 7 through the pump 1. And an electric signal is exchanged between them.

On the other hand, on the wiring board 7 on which a predetermined circuit pattern is formed so as to mount the IC element 5, a large number of terminals 12 connected to the circuit pattern are provided on the bump 1 as shown in FIG.
Are formed at positions opposite to the terminals 12, respectively.
Protective films 11 and 13 having openings as shown in the figure.
It is covered with.

Further, the bump 1 and the terminal 1 which are metal projections are provided.
2 is a conductive adhesive in which countless fine conductive particles 4 are uniformly dispersed in an adhesive made of epoxy resin.
The CP3 is interposed, and the electrical connection between the terminal 12 and the bump 1 is made conductive by the conductive particles 4a contributing to conduction.

At this time, the second area surrounded by the opening is larger than the area 16 of the first connection surface 1a of the bump 1 which is a metal projection.
By setting the area 15 of the connection surface 12a to be large, the second connection surface 1 surrounded by the opening having the area 15
The first connection surface 1a having the area 16 is reliably positioned inside 2a, so that a predetermined number of conductive particles 4a can be reliably interposed.

The wiring board 7 is made of non-alkali glass, the wiring also serves as a connection terminal, and the protective film of the wiring board forms an opening of the terminal. As for the bump formation, the wafer after the semiconductor formation process is washed, and then a barrier metal film is formed with a titanium metal film at a thickness of 4000 ° by sputtering. In addition, tungsten or titanium tungsten is used.

Further, in order to attach the bump 1 by plating, for example, gold or lead
0 ° is formed. A bump is formed by patterning a gold or lead film at a position where a bump is to be formed in a predetermined shape, and further using a titanium layer of a barrier metal as an electrode in a shape where a bump forming portion is removed with a plating resist. Here, the size of the bump 1 is 60 μm square and the pitch is 115 μm.

The terminal portion on the side of the wiring board 7 covers the wiring portion with an inorganic or organic protective film, and the terminal portion has an opening formed by removing the protective film in a square shape. This opening is 75 μm square considering the bonding accuracy ± 10 μm on the device side, and the space between the openings is set to 40 μm.

In order to obtain the state shown in FIG. 1, a predetermined amount of ACP is previously applied to a predetermined position by a dispenser or transfer on a bonding apparatus, and then a bonding tool sucks the back surface of the IC element from the chip tray. lift. Furthermore, the IC adsorbed on the bonding tool side
The alignment mark of the chip is recognized by the camera, the alignment mark on the wiring board 7 is recognized by the camera, and the IC chip is aligned with a predetermined position on the wiring board 7 and pressed.

At this stage, the tip of the bump 1 reaches the terminal 12, but when only the pattern is formed on the substrate side as in the prior art,
Although the fluid flows out from between the bump patterns due to the fluidity of the ACP 3, in the above case, the flow of the conductive particles 4 is suppressed at the step portion of the protective film 11 on the wiring substrate 7 side. The conduction is ensured without disappearing.

Thereafter, heating is performed from the tool side in a pressurized state to cure the adhesive. The heating conditions are 150 ° C. and 70 s for a liquid epoxy adhesive.
Curing is completed in about ec. Note that the tool is preferably made of ceramics that are not easily deformed when pressed and heated, and is heated by pulse heat.

By employing the above-described structure and the pressurizing and heating method, it is possible to lower the connection temperature, and furthermore, the conductive particles are less likely to flow out during the thermocompression bonding, so that conduction can be reliably achieved.

FIG. 2 shows a second embodiment of the present invention.
It is sectional drawing which showed the mode that the C element was flip-chip mounted on the board | substrate.

In FIG. 2, the same reference numerals are given to the components already described, and the description thereof is omitted. The protective film 11 is a projection 11 overlapping the edge of the terminal 12.
a. The bank 14 is formed of a photosensitive organic resin material, which is an organic resin material, so as to surround the protrusion 11a from the periphery.

According to the configuration shown in FIG. 2, even if the ACP 3 has a large fluidity, it can be prevented from flowing outside by keeping the ACP 3 in the area surrounded by the bank portion 14. Is held down, so that conduction is performed more reliably. FIG. 3A is a plan view showing a state in which a cut 16 is provided in the bank portion 14 in the second embodiment, and FIG.
-It is an X-ray arrow sectional drawing. In FIG. 3, the bank 14
Are formed so as to surround the square terminal 12 as shown in the figure, and a cut 16 for discharging the resin is provided in the middle thereof.
Are formed at four places.

FIG. 4A is a plan view showing how the bank portion 14 is formed substantially linearly in the second embodiment, and FIG. It is X-ray arrow sectional drawing.

In FIG. 4, cuts 16 are formed at the four corners of the bank 14. Further, on the terminal 12, a projection 17 made of plating is further formed.

To form the bank shown in FIGS.
In the flowchart of FIG. 5, the protective film 11 of the substrate 7 is formed in step S1, and the process proceeds to step S2, in which a dry film having a predetermined thickness is attached with a photosensitive dry film, a coating resist, or the like to secure adhesion. Perform pre-bake. Next, pattern processing is completed by exposing and developing a predetermined pattern surrounding the terminal portion on the substrate side, and post-baking is performed to complete the formation of the bank portion 14 (step S3). When the height of the bump 1 is 20 μm, the thickness (height) of the bank portion 14 needs to be set at a slightly lower value of 16 μm in consideration of the amount of deformation of the bump at the time of pressure bonding. When the bank portion 14 is higher than the bump 1, the bank portion 14 comes into contact with the element surface of the IC first, and the terminals are not connected. Here, the case of a coating resist is almost the same except that the coating process is different.

As described above, the bank portion 14 is provided around the terminal 12.
ACP is applied to a predetermined position on the substrate 7 with a dispenser or transfer on a bonding apparatus by a dispenser or transfer (step S4), and then the bonding tool sucks and lifts the back surface of the IC from the chip tray. Further, the alignment mark of the IC chip adsorbed on the bonding tool side is recognized by the camera, the alignment mark on the substrate is recognized by the camera, and the IC chip is aligned with a predetermined position on the substrate and crimped (step S5). It is completed through the above steps.

At this time, the resin between the bumps and the board-side terminals is discharged from the cuts 16 of the bank portion 14 at the time of pressure bonding. At this time, the conductive particles 4 slightly flow out along with the discharge of the ACP 3, but since they are overwhelmingly less than in the conventional case,
A large amount will remain inside the bank portion 14. For this reason, the flow of the conductive particles between the bump and the substrate terminal is suppressed, so that the conductive particles are not completely eliminated from between the bump and the pattern, and the conduction is ensured. Further, in the case of an adhesive using a liquid epoxy adhesive, a heating condition of 150 ° C., 70 ° C.
The curing is completed in about sec.

When the cut 16 is located at the corner as shown in FIG. 4, the flow of the conductive particles slightly increases. Also, as shown in FIG. 3, it was confirmed that the conductive particle density inside the corner became high when it was in the middle of the bank portion 14.

As described above, since the number of conductive particles remaining between the bump and the terminal on the substrate side is large, it is desirable that the cut is located in the middle of the bank.

Through the above steps, a pattern was formed on a glass substrate, and after applying ACP, IC mounting was performed. As a result, good results were obtained in comparison with the conventional one.

According to each of the above embodiments, even when the terminal portion for connection on the substrate side is more convex than the protective film, the periphery is partially surrounded by cut banks, so that the conductive particles can flow out. , And the adhesive between the bumps and the terminals can be discharged without any trouble, so that the connection can be reliably performed.

According to the present invention, by surrounding the periphery of the terminal portion with the protective film on the substrate side, the outflow of the conductive particles at the time of pressurization is suppressed, and the connection can be reliably performed.

Further, a bank lower than the height of the bump formed on the IC side is formed around the opening on the substrate side, and a bank is provided so as to surround the opening of the terminal on the substrate side.
Alternatively, by providing it on the side, the outflow of the conductive particles at the time of pressurization is further suppressed, and connection can be made more reliably.

[0057]

As described above, according to the present invention,
It is possible to provide a face-down mounting board and a face-down mounting method that can always achieve stable electrical conduction regardless of the fluidity of the anisotropic conductive paste (ACP) and the degree of dispersion of conductive particles.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a substrate and an IC after flip-chip mounting according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a substrate and an IC after flip-chip mounting according to a second embodiment of the present invention.

3 (a) is a plan view of a bank portion 14, and FIG.
-It is an X-ray arrow sectional drawing.

FIG. 4 (a) is a plan view of a bank portion 14, and FIG.
-It is an X-ray arrow sectional drawing.

FIG. 5 is a flowchart showing a substrate mounting step.

FIGS. 6A to 6C are cross-sectional views of a conventional substrate and an IC after flip-chip mounting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bump (metal protrusion part) 2 Barrier metal 3 ACP (Anisotropic conductive adhesive) 4 Conductive particle 4a Conductive particle which contributes to connection 5 IC element 6 Pad 7 Wiring board 10 Passivation film 11 Protective film 12 Terminal part 14 Bank part 16 Break of bank 17 Protrusion by plating of board terminal

Claims (12)

[Claims] 1. A wiring layer provided on a substrate, a protective film covering the wiring, and a wiring substrate provided with terminals formed at openings of the protective film. A metal projection is provided on the layer, and the surface of the substrate on which the wiring and terminals are provided and the surface of the IC provided with the metal projection are bonded with a conductive adhesive, and electrical connection between the terminals is simultaneously established. A face-down mounting board, wherein a dimension of an opening of the protective film of a connection terminal on the board side is larger than a dimension of the metal protrusion. 2. A wiring formed on a substrate, a protective film covering the wiring, and a wiring substrate provided with a terminal formed in an opening of the protective film or a protection film for protecting the wiring substrate on the opening of the protective film. A substrate having projections formed from the film, a metal layer on the terminal on the C side and a metal projection on the metal layer, and a surface provided with wiring and terminals of the substrate with a conductive adhesive. In a face-down mounting board that adheres to a surface provided with a metal projection on the IC side and simultaneously establishes electrical connection between terminals, the protrusion of the connection terminal on the wiring board side or the protective film on the wiring board side A face-down mounting board, wherein a bank is arranged so as to surround the opening. 3. The height of a bank surrounding the opening or a terminal protruding from the protection film on the substrate side is lower than the height of a metal projection on the IC side. A face-down mounting board as described in Crab. 4. The face-down mounting board according to claim 2, wherein the opening or the bank has at least one cut. 5. The device according to claim 4, wherein the opening or the cut is provided at a middle part or a corner part.
The face-down mounting board according to 1. 6. The face-down mounting board according to claim 2, wherein the opening or the bank is formed of an organic resin material. 7. The face-down mounting board according to claim 6, wherein the organic resin material is a photosensitive organic resin material. 8. The substrate according to claim 1, wherein a multi-terminal drive driver IC for driving a thermal line head or for a liquid crystal display device is mounted as the IC element.
A face-down mounting board according to any one of claims 1 to 7. 9. A terminal formed on the substrate is covered with a protective film so as to have an opening, a metal projection is formed on a terminal of the IC element, and a conductive portion is formed between the opening and the metal projection. A face-down mounting method in which a conductive adhesive in which particles are dispersed is interposed, and the terminal and the metal protrusion are electrically connected by heating and pressurization, wherein: A face-down mounting method, wherein a second connection surface of the opening is set large so that the conductive particles are reliably interposed between the first connection surface and the second connection surface. 10. A terminal formed on a substrate is covered with a protective film so as to have an opening, and a protruding portion projecting from the protective film is formed at an edge of the opening. Forming a metal protrusion on the opening, interposing a conductive adhesive in which conductive particles are dispersed between the opening and the metal protrusion, and heating and pressurizing the electric connection between the terminal and the metal protrusion. A face-down mounting method for establishing an electrical connection, wherein a second connection surface of the opening is set to be larger than a first connection surface of the metal protrusion, and a bank portion is formed around the protrusion. A face-down mounting method, wherein the conductive particles are reliably interposed between the first connection surface and the second connection surface in a range surrounded by the bank portion. 11. The face-down mounting according to claim 9, wherein the height of the opening or the height of the bank is lower than the height of the first connection surface. Method. 12. The opening or the bank portion has at least one cut formed therein, and an excess amount of the conductive adhesive can be removed from the cut. The face-down mounting method according to any one of the above.