JP2002359258A - Method for mounting electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress spreading of a resin to the outer peripheral side of an electronic component, when the resin is injected in a method of mounting for forming an underfill charging structure. SOLUTION: A method for mounting the electronic component comprises steps of mounting an IC chip 10 on a laminating substrate 20, and then heating the chip 10 by conducting the chip 10, so that the chip 10 becomes higher than a temperature of a side except for the chip 10 when the resin 14 is injected and filled as an underfill material between the chip 10 and the substrate 20 from an outer periphery of the chip 10. Thus, the resin is injected, in a state in which the viscosity of the resin 14 between opposed chip 10 and the substrate 20 is made lower than that at a site, except at places other than it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component in which after an electronic component is mounted on a wiring board, a resin is injected and filled between the electronic component and the wiring board from the outer periphery of the electronic component. Regarding implementation method.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional general mounting method of this type as an example in which an IC chip 10 as an electronic component and a wiring board 20 are flip-chip mounted. As shown in FIG. 9A, the IC chip 10 and the wiring board 20 are arranged to face each other. In the opposite part of both,
The bumps 11 for connection are formed on the IC chip 10, the electrodes 22 formed corresponding to the bumps 11 are formed on the wiring board 20, and the solder 30 is provided on each electrode 22 by printing or the like. Have been.

Then, as shown in FIG. 9B, the IC chip 10 is mounted on the wiring board 20, and the solder 30 is heated and reflowed, so that the wiring board 20 and the IC chip 10 are soldered together. To join.

[0004] Next, as shown in FIG.
The thermosetting resin (underfill material) 41 is applied to the outer peripheral portion of the IC chip 10 among 0 and disposed. Subsequently, as shown in FIG. 9D, the wiring board 20 and the IC chip 10
By heating the whole to lower the viscosity of the resin 41, the resin 41 is injected and filled between the IC chip 10 and the wiring board 20 by utilizing the capillary phenomenon. After that, the resin 41 is cured.

[0005] The mounting structure formed in this manner is called a so-called underfill filling structure. Since a resin 41 as an underfill material is filled between the IC chip 10 and the wiring board 20, The thermal stress applied to the joint of the solder 30 by the cooling / heating cycle can be reduced, and the connection life of the joint can be improved.

[0006]

However, according to the study of the present inventors, it has been found that the following problem occurs in the mounting method for forming the above-mentioned underfill filling structure. FIG. 10 shows a resin 41 in a conventional mounting method.
FIG. 3 is an explanatory diagram showing, in an enlarged manner, a state (a) at the time of application and a state (b) during the injection.

On the wiring board 20, in addition to the IC chip 10 mounted via the resin 41, components (capacitors, resistors, etc.) not shown in portions other than the mounting area of the IC chip 10 and pads for wire bonding are provided. Etc. are formed. Therefore, as shown in FIG. 10A, when applying the resin 41, the resin 41 is prevented from spreading to the outer peripheral side of the IC chip 10 as much as possible.

However, conventionally, when injecting the resin 41, the wiring board 20 and the entire IC chip 10 are heated to lower the viscosity of the resin 41.
As shown in (b), a resin 41 is applied to the outer peripheral side of the IC chip 10.
Is greatly expanded. For example, when the gap between the wiring board 20 and the IC chip 10 of 10 mm square is about 0.18 mm, the spread width W of the resin 41 is about 5 mm.

Since the resin 41 is injected into the gap between the IC chip 10 and the wiring board 20 by utilizing the capillary phenomenon by lowering the viscosity of the resin 41, it takes time to inject the resin 41 into the gap. On the other hand, the resin 41 spreads at a relatively high speed to the outer peripheral side of the IC chip 10 which is a wide space.

Due to the spread of the resin 41, the resin 41 is originally not desired to be present, for example, the resin 41 adheres to other components on the wiring board 20 or the resin 41 adheres to the wire bonding pads. The resin 41 is disposed even in the region. In order to avoid such a problem, it is necessary to increase the area of the wiring board 20, which is not preferable.

The present invention has been made based on the above-described novel problem found by the present inventor. In a mounting method for forming an underfill filling structure, when a resin is injected, the resin fills the outer peripheral side of the electronic component. The purpose is to suppress the spread of the resin.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, after the electronic component (10) is mounted on the wiring board (20), the electronic component is connected to the electronic component from the outer periphery. In the mounting method of an electronic component in which the resin (41) is injected and filled between the electronic component and the wiring board, when the resin is injected, the viscosity of the resin between the opposing electronic component and the wiring board is reduced. It is characterized by being lower than other parts.

According to this, when the resin is injected, the viscosity of the resin remaining on the outer periphery of the electronic component other than between the electronic component and the wiring board is smaller than that of the resin injected between the electronic component and the wiring board. As a result, the spread of the resin toward the outer peripheral side of the electronic component can be suppressed.

Here, the viscosity of the resin between the opposing part of the electronic component and the wiring board is made lower than that of the other parts, as in the second aspect of the present invention.
0) can be realized by applying heat to the electronic component so that the temperature is higher than the other parts. According to this, since the temperature between the opposing parts of the electronic component and the wiring board is higher than that of the other parts, the viscosity of the resin between the opposing parts can be appropriately reduced to be lower than that of the other parts. .

Further, the heat is applied to the electronic component (10) so that the temperature of the electronic component (10) is higher than that of the other parts.
By appropriately energizing the electronic component 0) to generate heat, the electronic component can be appropriately realized.

Further, it is preferable that the viscosity of the resin between the opposing part of the electronic component and the wiring board is made lower than that of the other parts.
It can also be properly realized by injecting the resin (41) while applying vibration only to the resin (41).

Further, in the invention according to claim 5,
The resin (41) is injected with the electronic component (10) positioned below the wiring board (20). According to this, since gravity is applied to the resin whose viscosity has decreased during the injection, it is possible to suppress the spread of the resin to the outer peripheral side of the electronic component.

The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention shown in the drawings will be described below. FIG. 1 is a schematic sectional view showing a mounting structure of an electronic component according to a first embodiment of the present invention. FIG. 1 shows a state in which two IC chips 10 as electronic components are flip-chip mounted on a laminated substrate 20 as a wiring substrate.

In this embodiment, each IC chip 10 functions as a microcomputer and has a thickness of 10 mm square and a thickness of 0.75 mm.
It is a chip of about the size. A solder bump 11 is formed on one surface of the IC chip 10 facing the laminated substrate 20. The solder bump 11 is formed by a solder ball or the like, and has a height of about 0.15 mm in this example.

As the laminated substrate 20, an ordinary ceramic laminated substrate in which a plurality of ceramic layers 20a are laminated can be employed. The wiring 21 a and the through hole 2 located between the respective layers 20 a are provided inside the laminated substrate 20.
2a and the like, the internal wiring layer 21 is formed, and the IC chip 1
A surface electrode 22 electrically connected to the internal wiring layer 21 via a through hole 22a is formed on one surface facing the surface 0.

In this embodiment, the laminated substrate 20 is formed by laminating a plurality of layers (three layers in the illustrated example) made of alumina, and the internal wiring layer 21 is made of W (tungsten), Mo (molybdenum), or the like. The surface electrode 22 has an underlayer of N
Au / Ni plating with i (nickel) and Au (gold) on the surface is applied.

The solder bumps 11 of the IC chip 10 and the surface electrodes 22 of the laminated substrate 20 are electrically and
Mechanically connected. Then, portions other than the solder joints between the IC chip 10 and the laminated substrate 20 are filled with an underfill material 40 made of a thermosetting resin material.

The underfill material 40 relieves the thermal stress applied to the joint of the solder 30 by the cooling and heating cycle, and improves the connection life of the joint. The underfill material 40 is made of a resin having a linear expansion coefficient close to that of the solder 30. ing. In this example,
An epoxy resin containing about 70% of a filler made of silica (for adjusting a coefficient of linear expansion) is used.

Next, a mounting method of the present embodiment will be described based on the above connection structure. FIG. 2 is an explanatory view showing this mounting method in the order of steps, and FIG. 3 is an explanatory view showing various injection methods in an injection step following FIG. 2 (d). The corresponding cross section is shown.

First, as shown in FIG. 2A, the mask K1
And the squeegee K2, the surface electrode 2 of the laminated substrate 20
The solder paste 30a is printed on the portion of the IC chip 10 connected to the solder bump 11 of the IC chip 10 (solder printing step). In this example, the thickness of the printed solder paste 30a is about 100 μm.

Next, as shown in FIG. 2B, one surface of the IC chip 10 and one surface of the laminated substrate 20 are arranged to face each other, and the solder bumps 11 and the surface electrodes 22 are aligned. Then, as shown in FIG. 2C, the IC chip 10 is mounted on one surface of the laminated substrate 20, and the solder is reflowed by heating, so that the IC chip 10 and the surface electrodes 22 of the laminated substrate 20 are connected to each other. The connection is made via the solder 30 (connection step).
Thereafter, a cleaning step is performed to remove dirt such as solder flux.

Next, as shown in FIG.
0, a thermosetting resin 41 serving as an underfill material is applied to the outer peripheral portion of the IC chip 10 (in this example, 3).
(Approximately 0 to 40 mg) (application step). This resin 4
1 can be applied using a dispenser, a printing method, or the like.

Subsequently, as shown in FIG.
IC by utilizing the capillary phenomenon by lowering the viscosity of
A resin 41 is injected and filled between the chip 10 and the laminated substrate 20 (injection step). In the injection step, the present embodiment is characterized in that the viscosity of the resin 41 between the opposing surface of the IC chip 10 and the laminated substrate 20 is lower than the viscosity of the resin 41 in other parts.

Specifically, making the viscosity of the resin 41 between the opposed portions lower than that of the other portions is as shown in FIG.
As shown in FIG. 2A, the current can be realized by energizing the IC chip 10 and causing the IC chip 10 to generate heat so that the temperature of the IC chip 10 becomes higher than that of other parts in the work.

In the injection step of this embodiment, the IC chip 10, the laminated substrate 20, and the resin 41 in the state shown in FIG.
It is carried out in a high-temperature bath at 60 ° C. Then I
By energizing the C chip 10 to generate heat, the temperature between the opposing surfaces is set to 80 to 10 which is the injection temperature of the resin 41 of this example.
Keep at 0 ° C. for about 30 minutes.

In addition to the above-described energization of the IC chip 10, as shown in FIG. 3B, a hot plate (heating jig) K3 heated only to the IC chip 10 may be brought into contact. Heat can be applied to the IC chip 10 so that the temperature of the IC chip 10 is higher than other parts of the work. Thereby, the viscosity of the resin 41 between the opposing portions can be made lower than the viscosity of the resin 41 in other portions.

In addition, making the viscosity of the resin 41 between the opposing portions lower than that of the other portions can be achieved by the IC chip 1.
It can also be properly realized by injecting the resin 41 while applying vibration only to zero.

For example, as shown in FIG. 3C, by bringing the piezoelectric element K4 into contact with the IC chip 10 and vibrating the piezoelectric element K4 via the power source K5, only the IC chip 10 can be vibrated. . Alternatively, a mounter used to mount the IC chip 10 on the laminated substrate 20 may be provided with a vibration mechanism.

After the injection step is completed as described above, the resin 41 filled between the IC chip 10 and the laminated substrate 20 is cured. In this example, 150 ° C., 1
Heating is performed for a time to cure the resin 41. Thus,
The mounting structure shown in FIG. 1 is completed.

According to the mounting method of the present embodiment described above, when the resin 41 is injected, the viscosity of the resin 41 between the opposing surfaces of the IC chip 10 and the laminated substrate 20 is lower than that of other parts. Therefore, the viscosity of the resin 41 remaining on the outer periphery of the IC chip 10 other than the space between the opposed sides becomes higher than that of the resin 41 injected between the opposed sides.

Therefore, according to the present embodiment, the spread of the resin 41 to the outer peripheral side of the IC chip 10 can be suppressed. Incidentally, in this example, 10 mm square, thickness 0.7
In the case where the gap (opposing interval) with the laminated substrate 20 is about 0.18 mm in the IC chip 10 of about 5 mm, the final spread width W (see FIG. 1) of the resin 41 (underfill material 40) is 2 mm. (About 5 mm conventionally).

As shown in FIG. 3 (a), when the IC chip 10 is energized to generate heat, the energization is also applied to the wiring of the laminated substrate 20 facing the IC chip 10. You may go. This also makes it possible to realize that the temperature of the IC chip 10 is higher than that of other parts of the work. Further, a heater circuit may be provided in these energized portions as needed.

When the temperature of the IC chip 10 is higher than that of the other portions, the temperature between the opposing surface of the IC chip 10 and the laminated substrate 20 is substantially equal to the temperature at which the resin 41 is injected. However, auxiliary heating may be performed from the outside if necessary. In the above-described example, auxiliary heating is performed in a high-temperature bath at 60 ° C.

It is preferable that the temperature difference between the above-mentioned facing and the other part is not less than 20 ° C.
In consideration of the range in which electronic components such as the chip 10 can generate heat, 80
C. or less is preferred.

The above-mentioned auxiliary heating is performed in the case of FIG. 3B and also in the case of injecting the resin 41 while applying vibration only to the IC chip 10 as shown in FIG. 3C. Good. The frequency of the vibration applied only to the IC chip 10 is preferably in the range of 10 to 100 kHz.

(Second Embodiment) FIG. 4 shows an injection step in an electronic component mounting method according to a second embodiment of the present invention. In the first embodiment, in the resin injection step, the IC
Resin 41 between opposing chip 10 and laminated substrate 20
The viscosity of the resin 4 on the outer peripheral side of the IC chip 10 is reduced by lowering the viscosity of the
1 was suppressed.

In the present embodiment, the steps up to the step of coating and arranging the resin 41 on the outer peripheral portion of the IC chip 10 (coating step) are performed in the same manner as in the first embodiment. Thereafter, the IC chip 10, the substrate 20, and the resin 41 are put in a high-temperature bath, and the temperature in the bath is set to a temperature at which the resin 41 can be injected.

At this time, as shown in FIG. 4A, using a holding jig or the like in the high-temperature bath, the IC chip 10 is positioned below the Is held, and the resin 41 is injected in this state. At this time, as shown in FIG. 4B, resin injection may be performed with the substrate 20 inclined while the IC chip 10 is positioned below the laminated substrate 20. After the resin injection, it is the same as the first embodiment.

According to the present embodiment, gravity is applied to the resin 41 whose viscosity has decreased at the time of injection, as shown by a white arrow in FIG. The spreading speed of 41 decreases. Therefore, the spread of the resin 41 to the outer peripheral side of the IC chip 10 can be suppressed.

Also, as in the present embodiment, the IC chip 1
0 is positioned below the laminated substrate 20 and the resin 4
Performing the implantation of 1 can be effectively applied to the case shown in FIG. FIG. 5 shows an IC chip 10
FIG. 4 is a diagram schematically showing an enlarged portion between the substrate and the laminated substrate 20.

When the IC chip 10 is a wafer level CSP (chip size package) or the like, a layer made of a resin such as polyimide is formed on the surface of the chip 10 where the underfill material is filled. In FIG. 5, this layer is shown as a polyimide layer 10a. An electrode (not shown) is pulled out of the chip 10 using the polyimide layer 10a as an insulating layer, and is connected to an electrode (not shown) of the laminated substrate 20 made of ceramic via the solder 30.

Here, as shown in FIG. 5, if the resin 41 serving as an underfill material is injected in a state where the IC chip 10 is located above the laminated substrate 20, as shown in FIG. Voids) are likely to occur.

The reason is that the wettability to the resin 41 is
This is because the polyimide layer 10a on the chip 10 side is different from the ceramic forming the surface of the laminated substrate 20. That is, as shown in FIG. 5A, since the polyimide layer 10a has higher wettability than a ceramic such as alumina, the injected resin 41 flows faster on the polyimide layer 10a side, and Flows slowly at.

In addition to the difference in wettability between the polyimide layer 10a and the ceramic, the laminated substrate 20 has larger irregularities on the surface, and the friction of the resin 41 on the laminated substrate 20 due to gravity is larger. This also causes the difference in the flowability.

When the filler 41a is mixed with the resin 41, the density of the filler in the resin 41 on the side of the laminated substrate 20 increases due to the sedimentation of the filler 41a due to gravity, which may cause an increase in viscosity. It causes a difference in flowability.

Further, in addition to the above-described difference in wettability, other factors are added, so that the resin 4 on the substrate 20 side is formed.
There is a large difference between the flowability of No. 1 and the flowability of the resin 41 on the polyimide layer 10a side. Then, as shown in FIG. 5 (b), the resin 41 on the side of the polyimide layer 10a, which proceeds further,
Collides with the solder 30 and entrains air to generate fine voids.

As described above, when the resin 41 is injected between the substrate 20 and the electronic component 10 mounted thereon,
If the flowability of the resin 41 on the side of the electronic component 10 is greater than the flowability of the resin 41 on the side of the substrate 20, if the substrate 20 is positioned below the electronic component 10, Voids are likely to be generated when implanting.

In this regard, in this embodiment, FIG.
As shown in (a) and (b), the injection of the resin 41 in a state where the IC chip 10 is positioned below the laminated substrate 20 makes it possible to reduce the occurrence of voids.

That is, as shown in FIG. 6, by lowering the IC chip 10 at the time of injecting the resin 41, on the side of the IC chip 10 having a high flowability in material, an increase in friction due to gravity and an increase in the filler 41a are caused. The sedimentation causes an increase in viscosity, and the flowability of the resin 41 is lower than when the IC chip 10 is located on the upper side.

On the other hand, in the resin 41 flowing on the side of the ceramic substrate 20 which is low in material flowability, an increase in friction due to gravity and an increase in viscosity due to sedimentation of the filler 41a are eliminated. For this reason, the difference in the flowability of the resin 41 between the IC chip 10 and the substrate 20 is reduced, so that the entrainment of air as shown in FIG. 5 does not easily occur, and the generation of voids is also reduced.

In this embodiment, when the resin 41 is injected with the IC chip 10 positioned below the laminated substrate 20, the IC chip 10 is cooled and the substrate 20 is heated. A method of injecting the resin 41 may be adopted.

According to this method, the flowability on the substrate 20 side can be further increased, so that the method can be used as one method for reducing the flowability difference between the IC chip 10 side and the substrate 20 side. For example, the IC chip 10 is cooled by blowing cold air or radiating heat using a heat sink, and the substrate 20 is heated by energizing a heater incorporated in the substrate 20 and wiring of the substrate 20. It can be carried out.

As a method for injecting a resin for reducing the generation of voids due to such a difference in flowability, a method as shown in FIG. 7 can be employed. In this method, the substrate 20 on which the IC chip 10 is mounted is
10, and the rotating plate K10 is rotated so that centrifugal force is applied from the substrate 20 toward the IC chip 10.

According to this, from the substrate 20 to the IC chip 1
By applying centrifugal force in the same manner as when gravity is applied to zero, the same operation and effect as in the case shown in FIG. 6 can be obtained.

(Other Embodiments) As the resin 41 serving as the underfill material, in addition to the above-described epoxy resin containing silica as a filler, an epoxy resin or an acrylic resin is used as a main agent. As the filler to be mixed with the main component, silica, alumina, or the like can be used, and the main component and the filler may be appropriately selected.

As shown in FIG. 8, the portion of the substrate 20 where the resin 41 is applied on the outer periphery of the IC chip 10 is as follows.
(A) one side of the IC chip 10, (b) multiple sides (two sides in the figure), (c) one point,
(D) Multiple points (two points in the figure) may be used.

The injection temperature of the resin 41 is determined by the resin material. When the injection temperature is about room temperature or lower than room temperature, the entire work is cooled and the whole work is cooled below the injection temperature. Lower, in which IC chip 1
Each method shown in FIG. 3 may be used so that the temperature between the opposing position of 0 and the substrate 20 is higher than the temperature of the other portions.

It is also possible to adopt a method in which the application and injection steps are repeated a plurality of times with the amount of one application being smaller than the finally required amount. Further, the application and the injection may be performed simultaneously.

The electronic component may be a power element or the like other than the IC chip. The mounting form of the electronic component may be BGA (ball grid array), CSP (chip size package), or the like, in addition to the flip chip. The bumps of the electronic component may be flip chip bumps or stud bumps formed by wire bonding, in addition to the solder balls.

As the type of the wiring substrate, a ceramic substrate, a printed substrate, or the like can be applied, and the structure may be a single-layer substrate or a multilayer substrate. The electrodes of the wiring board connected to the electronic components include Au, Ag,
Cu, Ni, etc., Au, Ag, C
It may be made of a thick film material mainly containing u or the like.

The arrangement of the solder 30 is determined by the printing method (FIG. 2).
In addition to (a), the dispensing method may be used. Further, the bonding between the electronic component and the wiring board may be performed by, for example, providing a conductive adhesive on the wiring board by printing, dispensing, stamping, or the like, in addition to performing the above-described solder 30 by reflow, and by heating or the like. It may be performed by curing the conductive adhesive, or may be performed by thermocompression bonding in which heating and pressing are performed.

In short, the present invention relates to a method of mounting an electronic component in which after mounting an electronic component on a wiring board, a resin is injected and filled between the electronic component and the wiring board from the outer periphery of the electronic component. In the above, the resin injection step is a main part, and the other parts can be changed in design as appropriate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a mounting structure of an electronic component according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for mounting an electronic component according to the first embodiment.

FIG. 3 is an explanatory view showing a method of injecting a resin in the mounting method, wherein FIG.
(B) shows a method of heating only the IC chip using a heating jig, and (c) shows a method of applying vibration to only the IC chip.

FIG. 4 is a schematic cross-sectional view showing a resin injection method in an electronic component mounting method according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically showing a resin injection part in the electronic component according to the second embodiment.

FIG. 6 is a schematic cross-sectional view for explaining another operation and effect of the resin injection method in the electronic component mounting method according to the second embodiment.

FIG. 7 is a view for explaining another resin injection method for obtaining the function and effect shown in FIG. 6;

FIG. 8 is a diagram showing various examples of resin application positions.

FIG. 9 is a process chart showing a conventional general method of mounting an electronic component.

FIG. 10 is an explanatory diagram showing, in an enlarged manner, a state at the time of application of a resin and an intermediate state at the time of injection in a conventional mounting method.

[Explanation of symbols]

 10: IC chip, 20: laminated substrate, 41: resin.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E314 AA32 BB06 CC17 FF02 FF05 FF19 GG01 5F061 AA01 BA04 CA04

Claims (5)

[Claims] After mounting an electronic component (10) on a wiring board (20), a resin (41) is injected and filled between the electronic component and the wiring board from the outer periphery of the electronic component. In the electronic component mounting method, when the resin is injected, the viscosity of the resin between the opposing electronic component and the wiring board is set to be lower than that of other parts. Characteristic electronic component mounting method. 2. When injecting the resin (41), heat is applied to the electronic component (10) so that the temperature of the electronic component (10) is higher than that of other portions, so that the electronic component and the electronic component are heated. 2. The electronic component mounting method according to claim 1, wherein the viscosity of the resin between the opposing portion and the wiring substrate is lower than that of other portions. 3. The electronic component according to claim 2, wherein the electronic component is energized to generate heat so that the temperature of the electronic component becomes higher than other portions. The mounting method of the described electronic component. 4. The method for mounting an electronic component according to claim 1, wherein the injection of the resin is performed while applying vibration only to the electronic component. 5. After the electronic component (10) is mounted on the wiring board (20), a resin (41) is injected and filled between the electronic component and the wiring board from the outer periphery of the electronic component. In the electronic component mounting method described above, the resin is injected in a state where the electronic component is positioned below the wiring board.