JPH08107133A - Method of connecting chip part to board - Google Patents

Abstract

PURPOSE: To provide a method of securely connecting chip parts to a board without causing a short circuit even if high-density mounting is made on wiring patterns lessened in space between them. CONSTITUTION: When a chip part is made to bear against a wiring pattern through the intermediary of metal bumps, a prescribed pressure is applied onto a pressing member so as to absorb the irregularity of the metal bumps in height, to enable the bumps to come surely into contact with the wiring pattern, the metal bumps are fused by heating, the pressing member is controlled in position and lessened in pressing force corresponding to a fusion state of the metal bumps, and furthermore the pressing member is controlled to widen the gap between the chip part and the board so as to eliminate a thermal expansion effect of the pressing member. Moreover, the pressing member is controlled to adjust the gap between the chip part and the board so as to repress an effect caused by a pressure change induced by the shrinkage of the board when the metal bumps are hardened by cooling after heating is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting chip parts on a substrate, and more particularly to a method for high density connection of chip parts such as semiconductors to a substrate using metal bumps such as solder bumps.

[0002]

2. Description of the Related Art In recent years, miniaturization of chip parts such as semiconductors,
With the high integration and the increase in the number of pins, it is essential to establish a high-density connection technology for these chip parts to the substrate.

Conventionally, ceramic substrates, glass substrates,
As a method of connecting a chip component to a substrate such as an epoxy resin substrate or a tape carrier, a self-alignment connection method by reflow using solder bumps is generally used. In this method, substantially spherical solder bumps are previously formed on the connection pads of the chip components or on the wiring pattern formed on the substrate, the chip components are placed on the wiring pattern via the solder bumps, and the solder bumps are formed. By heating, the chip components are positioned on the wiring pattern due to the surface tension of the melted solder bumps.
It is connected. On the other hand, as a method for connecting a chip component to a plastic film substrate such as a tape carrier, a thermocompression bonding method or a wire bonding method in which a gold bump and a tin plating pattern are thermocompression bonded under high temperature and high pressure is generally used.

However, in the above-described reflow-type connection method, the solder bumps are pressed by the weight of the chip component, so that the solder bumps 3 on the connection pads 2 of the chip component 1 are melted as shown in the figure. Between the wiring pattern 4 on the substrate (not shown) and the connection pads 2 on the chip component 1, the material is cooled and solidified while being crushed in a barrel shape. Therefore, there is a high risk that adjacent solder bumps 3, 3 will come into contact with each other to form a bridge. In order to avoid the contact between the solder bumps 3 and 3, it is necessary to widen the arrangement pitch interval of the connection pad and the wiring pattern 4, so that high density connection is difficult.

Further, in a structure in which the chip component and the substrate are connected by using metal bumps such as solder bumps, thermal fatigue caused by a difference in thermal expansion coefficient between the chip component and the substrate when a temperature cycle load is applied. However, since the approximately barrel-shaped connection solder 3 formed by the reflow connection method has a small connection height to cross-sectional area ratio,
Conduction failure due to thermal fatigue is likely to occur at an early stage, making it difficult to secure high reliability.

On the other hand, in the thermocompression bonding method described above, high-density connection with a wiring pitch interval of about 100 μm is possible, but there is a risk of damaging chip components due to high temperature and high pressure, and the cost is increased because gold bumps are used. Has the drawback of being high. In addition, a device with high precision and high rigidity is required,
If multiple pins of 300 pins or more are connected at the same time, there is a problem in that it is difficult to realize because the pressure load is too large. Further, as shown in the figure, since the gold bumps 5 connecting the connection pads 2 on the chip component 1 and the wiring patterns 4 on the substrate (not shown) are crushed into a plate or film under high pressure, Regarding the point of fatigue caused by the difference in thermal expansion coefficient between the chip component 1 and the substrate when a cycle load is applied, the same problem as in the reflow connection method occurs.

The wire bonding method uses one bonding
Since it is performed one by one, the bonding work takes a long time. Therefore, it is not suitable for connecting multi-pin chip parts.

As a method for solving the above-mentioned drawbacks of the connection method, a substrate made of a tape carrier having a wiring pattern formed thereon and a chip component having a solder bump formed on a connection pad are aligned with each other at a predetermined position and superposed, After heating and melting the solder bumps, it is possible to adjust the gap between the chip component and the substrate and control so that pressure is not applied to the solder bumps, so that the solder bumps are connected in a substantially drum shape. Proposed.

According to this method, since the solder bumps are melted between the chip component and the substrate and then solidify in a drum shape, the solder bumps may contact each other between adjacent connection pads or wiring patterns. In addition to eliminating the risk, the connection height ratio to the cross-sectional area of the solder is increased as compared with the case where the solder bump is crushed in a barrel shape and solidified, so that the occurrence of conduction failure due to thermal fatigue can be suppressed.

[0010]

However, in the above-described connection method, the pressure heating tool applies an appropriate load to the solder bump and melts the solder bump, but the pressure heating tool thermally expands. As a result, the gap between the chip component and the substrate becomes smaller than the gap set at the time of melting, which causes the shape of the solder bump to be barrel-shaped, which is a cause of defectiveness. Further, there is a problem that stress due to contraction of the solder bumps or the carrier tape at the time of cooling causes pressure fluctuation and a stable connection structure cannot be obtained.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is achieved by means of metal bumps formed on a chip component or a wiring pattern on the substrate through the chip component and the substrate. A method for connecting a chip component onto a substrate by bringing the metal bump into contact with the metal bump, heating and melting the metal bump, and then cooling and solidifying the metal bump. When the chip component and the wiring pattern are brought into contact with each other, a predetermined pressing force is applied by the pressing member to absorb the variation in the height of the metal bump to ensure the contact with the wiring pattern, and then the heating. Then, the metal bump is melted, and the pressure member is controlled in accordance with the melted state so as to weaken the pressing force, and thereafter, the tip portion is removed in order to remove the influence of the thermal expansion of the pressure member. Control to widen the gap between the chip component and the substrate, and when the heating is stopped and the metal bumps are cooled and solidified, the influence of the pressure fluctuation due to the contraction of the substrate during cooling is suppressed. It is characterized by controlling the gap of.

[0012]

The above-mentioned means operates as follows.

Before heating, melting and cooling of solder bumps
By minimizing the effects of thermal expansion and contraction during cooling until solidified, the gap between the chip component and the substrate can always be maintained in a constant relationship.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of connecting chip components according to an embodiment of the present invention will be described below in accordance with the procedure.

First, the chip component 1 is adsorbed on the surface of the receiving stage 5 so that the connection pads (not shown) on which the solder bumps 3 are formed face upward and the chip component 1 does not move. It is mounted, and a substrate composed of the tape carrier 2 is laid on it so that the wiring pattern (not shown) faces the connection pads, and the tape carrier 2 is for pressing and heating from the back side where the wiring pattern is not formed. The tape carrier 2 is pressed at a predetermined pressure by lowering the tool 4 of.

Next, the receiving stage 5 on which the chip component 1 is mounted is raised, the pressure sensor 6 detects an increase in the pressure applied to the receiving stage 5, and the solder bump 3 contacts the wiring pattern of the tape carrier 2. After checking, the ascending of the receiving stage 5 is stopped (state of FIG. 2).

Next, the temperature of the tool 4 is raised to heat and melt the solder bumps 3 from the side of the carrier tape 2. At this time, heating of the tool 4 causes thermal expansion of the tool 4 itself and heating of the tape carrier 3 causes thermal expansion of the tape carrier 3. Of these, the load balance between the tool 4 and the tape carrier 2 is lost due to the thermal expansion of the tape carrier 3, and if nothing is controlled, the tool 4 is 5 μm.
Since the tool 4 is lowered to some extent, the tool 4 is raised by this amount and the initial positional relationship between the tape carrier 3 and the tool 4 is maintained. Further, since the tool 4 itself descends by about 8 μm due to the thermal expansion of the tool 4 itself, the descending amount of this tool 4 descends and absorbs the receiving stage 5. By these controls, the influence of the thermal expansion of the tool 4 and the tape carrier 3 is eliminated, and the gap formed by the melted solder bumps 3 is supplied to the gap without decreasing to the initial set gap.

Next, the tool 4 and the receiving-side stage 5 are moved to a predetermined position in order to leave a gap between the chip component 1 and the tape carrier 2 so that the molten solder bump 3 has a substantially drum shape. Move (state of FIG. 3).

Then, the melted solder bumps 3 are cooled and solidified, but the pressure applied to the tool 4 increases due to the contraction of the tape carrier 2 during cooling. In order to absorb this increase in pressure, the pressure is slowly increased at a speed at which the pressure does not change (while measuring the pressure applied to the tool 4 by a pressure sensor (not shown)). At the same time, the solder bumps 3 contract due to the cooling of the solder bumps 3 and stress is applied in the direction of peeling from the chip component 1 or the tape carrier 2.
In order to prevent this, the receiving stage 5 is raised and controlled so that the pressure change during contraction does not occur.

Finally, waiting for the solidification of the cooled solder bumps 3, the tool 4 is released from the tape carrier 2, and the chip component 1 is adsorbed and released from the receiving side tool 5 to complete the connection.

In the above embodiment, the tape carrier is used as the substrate, but the same effect can be obtained by using a substrate on which other wiring patterns are formed. .

[0022]

[Effect] By performing the control as described above, the gap between the melted solder bumps does not change from the initially set gap, so that the solder bumps are crushed and adjacent bumps come into contact with each other. It is possible to prevent a short circuit from occurring and to achieve highly reliable connection (the recent solder bumps with a narrow pitch interval have a height of 60).
Although it is as low as approximately μm, the narrowing of approximately 13 μm due to thermal expansion causes the solder bumps to be considerably crushed and causes swelling, which causes a short circuit. Further, since a stable hourglass-like shape is obtained, an excellent effect that a connection structure that is stable in strength is also obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining steps of a connection method that is an embodiment according to the present invention.

FIG. 2 is an explanatory diagram showing a state in which a tape carrier is brought into contact with solder bumps of a chip component.

FIG. 3 is an explanatory diagram showing a state in which a tool and a receiving-side stage are controlled so that the shape of a molten solder bump becomes a drum shape.

[Explanation of symbols]

 1 chip part 2 tape carrier 3 solder bump 4 tool 5 receiving stage

Claims (1)

[Claims] 1. A chip component or a wiring pattern on a substrate is brought into contact with the wiring pattern on the substrate via a metal bump formed on a wiring pattern on the chip component or the substrate, and the metal bump is heated and melted, and then cooled and solidified. A method of connecting a chip component to a substrate by connecting the chip component to the substrate by performing a predetermined pressing force by a pressure member when the chip component and the wiring pattern are brought into contact with each other via the metal bump. After absorbing the variation in height of the metal bumps and making sure contact with the wiring pattern, the metal bumps are heated to melt the metal bumps, and the pressure member is adjusted according to the melted state. The pressure is controlled to weaken the pressure, and then control is performed to widen the gap between the chip component and the substrate in order to eliminate the influence of the thermal expansion of the pressure member, and then the heating is stopped to stop the metal. When cooling and solidifying the bumps, the gap between the chip component and the substrate is controlled so as to suppress the influence of pressure fluctuation due to contraction of the substrate during cooling, and a method of connecting the chip component onto the substrate. .