JP2659630B2 - Connection method between chip components and substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates also relates to a connection methods according to the molten metal of the chip component on the wiring conductors on the substrate, more particularly, IC utilizing solder bumps molten metal bumps, L
SI such as Ru <br/> relates to a high density connection methods to the chip components on the board.

[0002]

2. Description of the Related Art In recent years, as chip components such as ICs and LSIs have become smaller, more highly integrated, and have more pins, it has become essential to establish a high-density connection technology of these chip components to a substrate.
Is coming .

[0003] Conventionally, ceramic substrates, glass substrates,
As a method for connecting a chip component such as an IC to a wiring conductor formed on an epoxy resin substrate or the like, a self-alignment connection method by reflow using solder bumps is generally used. In this method, a substantially spherical solder bump is formed in advance on a connection pad of a chip component or on a wiring conductor formed on a substrate, and the chip component is placed on the wiring conductor of the substrate via the solder bump. The solder bumps are heated via the substrate, and the chip component is positioned on the wiring conductor by the action of the surface tension of the melted solder bumps. On the other hand, as a method for connecting a chip component such as an IC to a film substrate, a thermocompression method or a wire bonding method in which a gold bump and a tin plating pattern are thermocompressed under a high temperature and a high pressure is generally used.

[0004]

In the reflow connection method, since the solder bumps are subjected to the pressing force due to the weight of the chip component, the solder bumps on the connection pads 2 of the chip component 1 as shown in FIG. The bumps 3 are cooled and solidified in a state of being crushed in a barrel shape between the wiring conductors 4 on the substrate (not shown) and the connection pads 2 on the chip component 1 at the time of melting. For this reason, there is a high risk that the adjacent bumps 3 will come into contact with each other to form a bridge. In order to avoid contact between the bumps 3, 3, it is necessary to increase the wiring pitch interval between the connection pad 2 and the wiring conductor 4, so that high-density connection is difficult.

Further, in a structure in which a chip component and a substrate are connected by a molten metal such as solder, a problem of thermal fatigue caused by a difference in thermal expansion coefficient between the chip component and the substrate when a temperature cycle load is applied. It is necessary to consider that the barrel-shaped connection solder 3 formed by the reflow connection method has a small connection height ratio with respect to the cross-sectional area, so that conduction failure due to thermal fatigue easily occurs at an early stage, and high reliability is secured. Has become difficult.

Further, chip components such as ICs and LSIs connected on a substrate are generally sealed with a resin for the purpose of preventing oxidation of a conductor surface, securing insulation, and improving impact resistance. As described above, the connection height ratio of the barrel-shaped connection solder 3 to the cross-sectional area is small, so that the resin does not easily flow into the gap between the chip component 1 and the substrate, and bubbles are formed in the gap. In addition, there is a problem that a sufficient sealing effect cannot be obtained due to remaining air gaps.

On the other hand, in the above-mentioned thermocompression bonding method, high-density connection with a wiring pitch interval of about 100 μm is possible, but there is a risk of damaging chip parts such as ICs and LSIs due to high temperature and high pressure. There is a disadvantage that the cost is high because of using. Further, a high-precision, high-rigidity device is required, and when multiple pins of 300 pins or more are simultaneously connected, there is a problem that the pressing load is too large to be realized.
As shown in FIG. 5B, the gold bumps 5 connecting the connection pads 2 on the chip component 1 and the wiring conductors 4 on the substrate (not shown) are crushed in a plate or film under high pressure. Therefore, a chip component 1 when a temperature cycle load is applied
In terms of thermal fatigue caused by the difference in thermal expansion coefficient between the substrate and the substrate, and sealing with resin, the same problems as those in the reflow connection method have arisen.

In the wire bonding method, the bonding is
Since the bonding is performed one by one, a long time is required for the bonding operation.
Therefore, it is not suitable for connecting multi-pin chip components.

In view of the above problems of the prior art, it is an object of the present invention to realize a high-density connection by shortening a wiring pitch interval, and to realize a highly reliable connection structure between a chip component and a substrate at low cost. and to provide a connection methods between the chip component and the substrate.

[0010]

The present invention according to claim 1 is provided.
The method of connecting the chip component to the substrate is such that the chip component and the wiring conductor on the substrate are brought into contact via the molten metal bump formed on the chip component or the wiring conductor on the substrate, and the molten metal bump is heated. And then cooling and solidifying, thereby connecting the chip component and the wiring conductor on the substrate via the molten metal bump. In the method of connecting the chip component and the substrate, the chip component via the molten metal bump When the molten metal bump and the wiring conductor are aligned with each other at the time of contact with the wiring conductor, a predetermined pressure is applied to the molten metal bump at the same position to make all the molten metal bumps the same height, and then the Before the molten metal bump is heated to the melting temperature, the pressure is reduced or brought into a non-pressurized state.

In the above-described configuration, preferably, the chip component is preheated before contact with the wiring conductor, or the molten metal bump is heated to a melting temperature by pulse heating.

[0012]

In the method for connecting a chip component to a substrate according to the first aspect, when the molten metal bump is melted, the gap between the chip component and the substrate is adjusted to be at least the height dimension of the molten metal bump before melting. Therefore, the molten metal bump solidified by cooling has a maximum cross-sectional area smaller than the maximum cross-sectional area before melting. Therefore, there is no danger of short-circuiting between adjacent connection pads or between wiring conductors due to contact between molten metals, and high-density connection by short-circuiting wiring pitch intervals becomes possible. In addition, since the connection height ratio to the cross-sectional area of the molten metal is increased as compared with the case where the same volume of the molten metal bump is crushed into a barrel and solidified, the connection structure between the chip component and the substrate having excellent heat resistance fatigue resistance Can be realized at low cost. Moreover, the molten metal bump and the wiring conductor are aligned at the time of contact between the chip component and the wiring conductor, and a predetermined pressure is applied to the molten metal bump at the same position so that all the molten metal bumps have the same height. Therefore, the height of the metal bumps including the variation in the height of the substrate can be kept constant, and the connection failure can be eliminated.

In the above connection method, the heating time can be shortened by preheating the chip component before contact with the wiring conductor, and the molten metal bump is heated to the melting temperature by pulse heating. Thus, heating can be performed when necessary, if necessary, and the degree of freedom of heating can be increased.

[0014]

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

FIGS. 1 to 4 show a connection method according to the present invention .
1 shows an embodiment of a connection structure between a chip component formed on a substrate and a substrate. First, referring to FIGS. 1 and 2, a film substrate 11 is used as a substrate in this embodiment, and a wiring conductor 12 is formed on the film substrate 11. The method of forming the wiring conductor 12 having a desired pattern shape is not particularly limited, but after a copper foil is previously formed on the film substrate 11 with an adhesive 13,
A method of etching a copper foil through a mask can be employed. Preferably, the surface of the wiring conductor 12 is previously plated with molten metal such as solder.

As shown in FIGS. 1 and 4, IC, LS
The chip component 21 such as I has a connection pad 22,
The connection pad 22 and the wiring conductor 12 are connected via a solder bump 23 whose central portion is narrowed like a drum. The solder bumps 23 are previously formed by fusion bonding on the connection pads 22 of the chip component 21 or on the wiring conductors 12 on the substrate 11. When the solder bumps 23 are formed on the connection pads 22 or on the wiring conductors 12, the surface tension acts. It has a substantially spherical shape, but after being heated and melted on the wiring conductor 12, the chip component 2
Due to the adjustment of the gap between the substrate 1 and the substrate 11, the resin is cooled and solidified in a state where it is stretched in a substantially drum shape. For example, when the solder bump 23 having a bump diameter of 70 to 80 μm is used, the gap between the chip component 21 and the substrate 11 is increased by 20 to 30 μm or more when the solder bump 23 is melted. It can be formed in a substantially drum shape.

In the connection structure of the above embodiment, since the solder bumps 23 are melted between the chip component 21 and the substrate 11 and solidified in a drum shape, the solder bumps 23 are connected between the adjacent connection pads 22 or 22. The risk of a short circuit between the wiring conductors 12 due to the contact between the solder bumps 23 is eliminated . In experiments, it was confirmed that high connection reliability was obtained by employing the above configuration even when the wiring pitch interval was 100 μm or less. Further, since the connection height ratio to the cross-sectional area of the solder is increased as compared with the case where the solder bumps having the same area are crushed into a barrel and solidified, the occurrence of conduction failure due to thermal fatigue can be controlled. Since the gap between the chip component 21 and the substrate 11 can be increased, when the chip component 21 is sealed with the resin 24 after the connection of the chip component 21, as shown in FIG. The inside of the resin 24 can be easily turned into the inside, and complete sealing can be achieved.

In the above embodiment, the solder bump is used as the molten metal bump. However, another alloy bump made of a low melting point alloy similar to the solder may be used. Further, the solder bump 23 may be solidified in a straight body between the chip component 21 and the wiring conductor 12 of the substrate 11. Further, as the substrate, a ceramic substrate, a glass substrate, a resin substrate such as epoxy, etc. can be used in addition to the above-mentioned film substrate.

[0019] FIG. 6 is a process diagram showing an embodiment of a method of connecting the chip component and the substrate according to the present invention. Although the wiring conductor 12 on the substrate 11 is exaggeratedly shown in FIG. 1, the thickness of the wiring conductor 12 made of, for example, copper foil is about 20 to 30 μm. Referring to FIG. 6, in this embodiment, the solder bumps 23 formed on the connection pads 22 of the chip component 21 are connected to the wiring conductors 1 on the film substrate 11.
The connection pads 22 on the chip component 21 and the wiring conductors 12 on the substrate 11 are connected via solder by heating and melting on the chip 2 and then cooling and solidifying. The feature is that the gap between the component 21 and the substrate 11 is adjusted to be equal to or larger than the height dimension of the solder bump 23 before melting.

More specifically, in this embodiment,
First, the film substrate 11 is pressed from behind (step (a)
), The wiring conductors 12 on the film substrate 11 are pressed against the substantially spherical solder bumps 23 formed on the connection pads 22 of the chip component 21 by the pressing force (step (b)).
). As described above, it is preferable that the surface of the wiring conductor 12 is previously plated with a low melting point metal such as solder.
In the pressurizing step, a predetermined pressing force is applied to the top of the solder bump 23, so that the height variation of the solder bump 23 can be eliminated.

Next, after the pressure applied to the solder bumps 23 is reduced or made non-pressurized, the solder bumps 23 are heated to a melting temperature to melt the solder bumps 23 ( Step (c)).

In this heating step, the solder bumps 23 are heated via at least one of the substrate 11 and the chip component 21. As described above, all the solder bumps 23 are previously adjusted to the same height. Therefore, all the solder bumps 23 are uniformly heated and melted at a uniform temperature. In this embodiment, the solder bumps 23
Is melted through a pressing step, so that the solder bumps 23 can be securely bonded to the wiring conductors 12 even if the flux required for the reflow soldering is omitted.

Further, in this embodiment, as described above, after the pressure applied to the solder bumps 23 is reduced or brought into a non-pressurized state, the solder bumps 23 are heated to the melting temperature. The solder bump 23 can be melted in a state where the compressive stress in the solder bump 23 is extremely small or no compressive stress is generated. Therefore, the spread of the molten solder bumps 23 can be reduced, and the risk that adjacent solder bumps come into contact with each other to form a bridge can be reduced.

FIG. 7 shows an example in which the solder bump 23 is heated to the melting temperature while the pressing force is applied to the solder bump 23.
This is shown for comparison with the above embodiment. The pressurizing steps (steps (a) and (b)) in this comparative example are the same as steps (a) and (b) shown in FIG. 6, but in this comparative example, the heating step (step (c)) Therefore, the solder bumps 23 are melted while the pressing force is applied to the solder bumps 23,
It can be seen that the solder bumps 23 spread greatly laterally, increasing the risk of contact with adjacent solder bumps.

In the above embodiment of the connection method according to the present invention, it is preferable to use pulse heating as a heating method in order to minimize the influence of heat on the chip components. Further, in order to shorten the heating time up to the melting temperature, it is preferable to preheat the chip component 21.

Still referring to FIG. 6, in the above embodiment of the connection method according to the present invention, when the solder bump 23 is melted, the substrate 11 or the chip component 21 (the chip component 21 in this embodiment) is turned off. Finely moved, the chip component 21 and the substrate 11
Is adjusted to be equal to or larger than the height dimension of the solder bump 23 before melting.
The chip component 21 is formed so that 3 has a substantially straight body or arc shape.
The gap between the substrate and the substrate 11 is adjusted (step (b)
). And while maintaining the adjusted gap size,
The solder bumps 23 are cooled and solidified.

As described above, in this embodiment, when the solder bump 23 is melted, the gap between the chip component 21 and the substrate 11 is adjusted to be equal to or larger than the height dimension of the solder bump 23 before melting. The solidified solder bump 23 has a maximum cross-sectional area smaller than the maximum cross-sectional area before melting. Therefore, adjacent connection pads 22,
There is no danger of short circuit between the wiring conductors 22 or between the wiring conductors 12 due to the contact between the solder bumps, and high-density connection by shortening the wiring pitch interval becomes possible. Also, since the connection height ratio to the cross-sectional area of the solder is increased as compared with a case where the same volume of solder bumps is crushed into a barrel and solidified, the connection structure between the chip component and the substrate having excellent heat fatigue resistance is reduced. It can be realized at cost.

In particular, as in this embodiment, the solder bumps 2
Reference numeral 3 denotes a chip component 21 having a substantially straight body or drum shape.
When the gap between the substrate and the substrate 11 is adjusted, the solder bump 2 cooled and solidified between the chip component 21 and the substrate 11 is formed.
Since 3 has a substantially straight body or drum shape, a connection structure between the chip component and the substrate, which can be connected more densely and has excellent thermal fatigue resistance, can be realized at low cost.

FIGS. 8 to 10 illustrate the above-described present invention.
It illustrates an embodiment of a connecting device for carrying out the that connection method. Referring first to FIGS. 8 and 9,
The connection device includes a bonding stage 31 for holding the chip component 21, and the belt-like film substrate 11 is placed above the bonding stage 31 in a state of tension via the guide rollers 32, 33 while facing the chip component 21. Is held. Above the film substrate 11, the molten metal bump 23 formed on the connection pad 22 of the chip component 21 and the substrate 1 are pressed by pressing the film substrate 11 from behind.
A bonding tool 34 for contacting the upper wiring conductor 12 is provided.

The bonding tool 34 includes a pressing cylinder 35 serving as a pressing mechanism, and a bonding head 36 provided at the tip of a movable rod 35a of the pressing cylinder 35.
And a lock mechanism 35b for chucking the movable rod 35a and stopping the movement thereof. The bonding tool 34 further includes a bonding head 36 and the film substrate 11 through which the solder bumps 23 are pulse-heated to a melting temperature. Pulse heat heating unit 37 for heating
Is incorporated.

The bonding stage 31 is a chip component 2
1 is mounted on the bonding table 38 and the bonding table 3
An X-axis adjusting mechanism 39 for adjusting the position of the bonding table 8 with respect to the bonding head 36 in the X-axis direction; a Y-axis adjusting mechanism 40 for adjusting the position of the bonding table 38 with respect to the bonding head 36 in the Y-axis direction; When the chip component 21 is melted, the chip component 21 is finely moved in the Z-axis direction.
And a Z-axis fine adjustment mechanism 41 for adjusting the gap between the metal bump and the film substrate 11 to be equal to or larger than the height of the molten metal bump 23 before melting. In this embodiment, a preheating unit (not shown) for preheating the chip component 21 is incorporated in the bonding table 38. Here, the Z-axis fine adjustment mechanism 41 uses a pulse motor 41a and a ball screw shaft / nut mechanism (not shown) that converts the rotation of the motor into a linear motion.
A mechanism for finely moving the bonding table 38 via the axis adjusting mechanisms 39 and 40 is used.
Fine movement in the axial direction may be performed.

Referring to FIG. 10A, the pressure cylinder 3
5 is partitioned into an upper chamber and a lower chamber, and a drive control system for the pressurizing cylinder 35 includes a pressurized air supply source 42,
First switching valve 43 for controlling supply and discharge of pressurized air to and from the upper chamber
And a second switching valve 44 for controlling the supply and discharge of the pressurized air to and from the lower chamber.
Before the 3 is heated to the melting temperature, a pressure reducing mechanism for reducing the pressure of the pressurizing cylinder 35 or setting it to a non-pressurized state is configured.

Next, referring to FIGS. 8 to 10, the operation steps of the above-described connecting device when the connecting method shown in FIG. 6 is performed will be described. First, as shown in FIG. 10A, pressurized air is supplied to the upper chamber of the cylinder 35 via the first switching valve 43,
The lower chamber of the cylinder 35 is opened to the atmosphere. As a result, the movable rod 35 a descends, and the film substrate 11 is pressed by the bonding head 36 at the tip of the movable rod, so that the wiring conductor 12 (FIG. 9) on the substrate 11 comes into contact with the solder bump 23 on the chip component 21. Then, as shown in FIG. 10B, a predetermined pressing force F is applied to the solder bumps 23.

Thereafter, as shown in FIG. 10C, pressurized air is supplied to the lower chamber of the cylinder 35 through the second switching valve 44, so that the pressing force applied to the solder bump 23 is reduced. The pressure is reduced or no pressure is applied. And
As shown in FIG. 10D, when the pulse heating unit 37 (FIG. 8) is energized in a state where the movable rod 35a is locked by the lock mechanism 35b, the solder bump 2
3 is pulse heat heated until it reaches the melting temperature. Next, when the solder bumps 23 are in a molten state, FIG.
0 (e), the chip component 21 is finely moved downward by the Z-axis fine adjustment mechanism 41 (FIG. 8),
The gap between the substrate and the substrate 11 is adjusted. Thus, the solder bumps 23 are cooled and solidified while being stretched in the vertical direction.

FIG. 11 shows a process of heating and melting the solder bump 23 while applying a pressing force to the solder bump 23 for comparison with an operation process by the above-described apparatus. As shown in FIGS. 11B to 11C, the movable rod 35a is locked with the locking mechanism 3 while the pressing force F is applied to the solder bumps 23.
When chucking is performed by 5b, a compressive stress remains inside the movable rod 35a and the like below the chucking portion. Therefore, as shown in FIG. Also, a residual pressure load f is applied to the solder bumps 23, so that the melted solder bumps 23 largely spread laterally.

On the other hand, the connection method of the present invention is implemented.
According to the connection device of the above-described embodiment, the spread of the solder bumps 23 can be prevented by reducing the pressure or applying no pressure as shown in FIGS.
Bridge formation between adjacent solder bumps can be prevented. According to the apparatus of the embodiment, the above-described FIG.
Through the step of 0 (e), the solder bump 23 has a maximum cross-sectional area smaller than the maximum cross-sectional area before melting, and preferably has a columnar shape with a central portion constricted in a straight or drum shape. . Therefore, the risk of short-circuiting between adjacent connection pads 22 or between the wiring conductors 12 due to contact between solders is reduced, and high-density connection by shortening the wiring pitch interval becomes possible. Also, since the connection height ratio to the cross-sectional area of the molten metal increases as compared to a case where the same volume of solder bumps is crushed into a barrel and solidified,
A connection structure between a chip component and a substrate having excellent thermal fatigue resistance can be realized at low cost.

In the connection device of the above embodiment, the fine adjustment mechanism 41 in the Z-axis direction is provided on the bonding stage 31 side. Alternatively, a similar fine adjustment mechanism may be provided on the bonding tool 34 side. Further, a pressing mechanism and a depressurizing mechanism may be constituted by using a pulse motor and a pressure sensor such as a load cell. Further, the bonding stage 31 is pressed so that the film substrate 11 is pressed toward the chip component 21 from below. The bonding tool 34 and the bonding tool 34 may be positioned upside down in the above embodiment. When a ceramic substrate, a glass substrate, a resin substrate, or the like is used as a substrate, the substrate is held by a bonding tool,
The substrate may be configured to be pressed toward the chip component.

[0038]

As is clear from the above description, according to the method for connecting a chip component to a substrate according to the present invention, a high-density connection can be achieved by shortening the wiring pitch interval, and a low-cost and highly reliable chip is provided. A connection structure between the component and the board can be obtained. In addition, by preheating the chip component before contact with the wiring conductor, the heating time can be reduced, and by heating the molten metal bump to the melting temperature by pulse heating, it is necessary when necessary. And the degree of freedom of heating can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing one embodiment of a connection structure between a chip component and a substrate formed by a connection method and a connection device of the present invention.

FIG. 2 is a schematic plan view of the connection structure shown in FIG. 1 as viewed from above.

FIG. 3 is a schematic side view showing an example in which the chip component having the connection structure shown in FIG. 1 is sealed with a resin.

4 is an essential part perspective view showing a solder connection relationship between a wiring conductor on a substrate and a chip component having the connection structure shown in FIG. 1;

FIG. 5 is a perspective view of a main part showing a connection state between a wiring conductor on a substrate and a chip component in a conventional connection structure between a chip component and a substrate, wherein (a) is formed by a reflow soldering method; (B) shows a connection state formed by a thermocompression bonding method using gold bumps.

FIG. 6 is a process explanatory view showing one embodiment of a method for connecting a chip component and a substrate according to the present invention.

FIG. 7 is a process explanatory view showing a comparative example of a method of connecting a chip component and a substrate.

FIG. 8 illustrates a method for connecting a chip component and a substrate according to the present invention.
Main part schematic perspective view showing an embodiment of a connecting device for facilities.

9 is a partial cross-sectional side view schematically showing a state in which a molten metal bump on a chip component and a wiring conductor on a substrate are pressed against each other by the connection device shown in FIG. 8;

FIG. 10 is a process explanatory view showing work steps until the molten metal bump on the chip component and the wiring conductor on the substrate are connected by the connection device shown in FIG. 8;

FIG. 11 is a process explanatory view showing work steps up to connection of a molten metal bump on a chip component and a wiring conductor on a substrate in a comparative example of a connection device.

DESCRIPTION OF SYMBOLS 11 Film substrate 12 Wiring conductor 21 Chip component 22 Connection pad 23 Solder bump 31 Bonding stage 34 Bonding tool 35 Pressing cylinder (Pressing mechanism) 37 Pulse heat heating unit 41 Z axis fine adjustment mechanism 43 First switching Valve 44 2nd switching valve (pressure reducing mechanism)

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-235352 (JP, A) JP-A-2-10844 (JP, A) JP-A-61-156745 (JP, A) JP-A-57-157 206037 (JP, A) JP-A-63-250831 (JP, A) JP-A-3-16237 (JP, A)

Claims (3)

(57) [Claims] 1. A chip component and a wiring conductor on a substrate are brought into contact via a molten metal bump formed on a chip component or a wiring conductor on a substrate, and the molten metal bump is heated and melted, and then cooled. In the method of connecting a chip component and a substrate, wherein the chip component and the wiring conductor on the substrate are connected via a molten metal bump by solidifying the chip component, the wiring between the chip component and the wiring conductor via the molten metal bump At the time of contact, the molten metal bump and the wiring conductor are aligned, and a predetermined pressing force is applied to the molten metal bump at the same position to make all the molten metal bumps the same height. A method of connecting a chip component and a substrate, wherein the pressure is reduced or brought into a non-pressurized state before heating. 2. The method for connecting a chip component to a substrate according to claim 1, wherein the chip component is preheated before the contact with the wiring conductor. 3. The method for connecting a chip component to a substrate according to claim 1, wherein the molten metal bump is heated to a melting temperature by pulse heating.