JP2000049192A - Flip-chip element mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mounting method in which even electrode pads arranged at fine pitch can be connected surely each other. SOLUTION: A large number of contact holes 11 are made through an insulating sheet 10 by punching and filled with solder paste 12 by screen printing. An insulating sheet 10 is then mounted on a substrate 30 while matching the contact holes 11 with electrode pads 31 and a semiconductor element 20 is mounted thereon while matching the contact holes 11 with electrodes 22. The solder paste 12 is spread into vertical gaps by applying a pressure from above and below. Finally, it is heated entirely at 200-220 deg.C to melt the solder paste 12 by reflow thus connecting both electrode pads 22, 31 electrically through a bump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip chip type element mounting method for connecting an electrode pad formed on an active element surface of an element to an electrode pad of a substrate via a bump.

[0002]

2. Description of the Related Art A conventional flip chip type element mounting method will be described with reference to the process chart of FIG. As shown in FIG. 2A, a plurality of electrode pads 2 connected to an internal circuit are formed on the active element surface 1a of the semiconductor element 1, and the periphery thereof is protected by a passivation film 3. The solder bumps 4 are formed on the electrode pads 2 by means such as screen printing or electrolytic plating.

Subsequently, the semiconductor element 1 on which the solder bumps 4 are formed is mounted on the substrate 5 while being positioned. As shown in FIG. 2B, an electrode pad 6 is also formed on the substrate 5, and its periphery is protected by a passivation film 7. The semiconductor element 1 includes a solder bump 4 and a substrate 5.
Is aligned so as to correspond to the electrode pad 6 of the first embodiment.

After mounting the semiconductor element 1 on the substrate 5, the solder bumps 4 are melted by reflow. The solder bumps 4 are melted into a spherical shape as shown in FIG.
The two electrode pads 2 and 6 are electrically connected. Finally, in order to protect the solder bumps 4, the gap between the semiconductor element 1 and the substrate 5 is filled with an insulating resin 8 as shown in FIG.

[0005]

However, in the conventional device mounting method described above, if the solder amount is increased in order to increase the bump height in order to increase the connection strength of the solder bump, the shape after reflow becomes spherical. For this reason, not only the height but also the width of the solder bumps are widened, and the bump pitch is widened, so that there is a problem that it is impossible to cope with the high density of the electrode pads. Also, in the conventional method, there is no means for regulating the flow range of the solder bump during reflow,
There is also a problem that the ratio between the width and the height of the solder bump after the reflow varies from bump to bump, and a connection failure between the electrode pads occurs in the bump having an insufficient height.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to increase the pitch of electrode pads without increasing the width even when the height of the bump is increased. It is another object of the present invention to provide a flip-chip type element mounting method that can cope with the above problem and that can reliably connect between electrode pads.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, a flip-chip type device mounting method according to the present invention is provided between an electrode pad formed on an active element surface of a device and an electrode pad of a substrate. In a mounting method in which a bump is interposed and the bump is melted by reflow to electrically connect the two electrode pads, a connection hole is formed in the insulating sheet through the sheet according to the position of the electrode pad, and the inside of the connection hole is formed. Filling the bump material, placing the insulating sheet between the substrate and the element so that the electrode pads correspond to the connection holes, and connecting the two electrode pads by melting the bump material by reflow It is characterized by.

According to the above method, since the spread of the bump material due to the reflow is limited to the inside of the connection hole of the insulating sheet, the height can be arbitrarily set while suppressing the spread in the width direction. In addition, the width of the bump material is regulated in the width direction, so that the height of the bump can be kept constant.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flip-chip type device mounting method according to the present invention will be described below. FIG.
FIG. 2 is a process diagram showing a mounting method according to the embodiment.

As shown in FIG. 1A, a large number of connection holes 11 having the same diameter penetrating the sheet are formed in an insulating sheet 10 having a thickness of about 100 μm by punching. The insulating sheet 10 is made of an epoxy resin or a silicon-based resin having a function of bonding the semiconductor element and the substrate by heat treatment. The connection hole 11 is a straight hole having a circular cross section, and the formation position is determined according to the position of the semiconductor element to be mounted and the position of the electrode pad on the substrate.

Punching is performed using a punching machine.
It is performed in the following procedure. First, the insulating sheet 10 is pasted on a metal frame for processing by a punching machine with glue. The metal frame is positioned and fixed by applying the corners of the metal frame to the positioning abutting portions provided on the stage of the punching machine from two directions. Next, coordinate data of the electrode pads formed on the substrate is input to the punching machine, and the punching machine is operated based on the data, thereby punching out a portion of the sheet corresponding to the electrode pads. The punching machine includes a vertically movable punch for punching. The stage on which the insulating sheet 10 is mounted is moved based on the coordinate data, and the punch is moved up and down at predetermined positions to connect holes 11. To form. In addition, the punch whose outer diameter is equal to the diameter of the connection hole 11 is used. Connection hole 1
After all the layers 1 are formed, the insulating sheet 10 is peeled from the metal frame to obtain the insulating sheet 10 in which the connection holes 11 are formed at predetermined positions.

Subsequently, as shown in FIG. 1B, a solder paste 12 is filled as a bump material in the connection holes 11 of the insulating sheet 10 by screen printing. The amount of the solder paste is set to be the same height as the sheet thickness of the insulating sheet 10.

Next, as shown in FIG. 1C, the insulating sheet 10 filled with the solder paste 12 is
And the substrate 30. On the active element surface 21 of the semiconductor element 20, a plurality of electrode pads 22 connected to an internal circuit are formed.
3 protected. On the other hand, a large number of electrode pads 31 are also formed on the substrate 30, and the periphery thereof is protected by a passivation film 32.

When arranging the insulating sheet 10, the insulating sheet 10 is first placed on the substrate 30 so that the connection holes 11 and the electrode pads 31 correspond to each other.
Then, the connection hole 11 and the electrode 2 are placed on the insulating sheet 10.
2 and the semiconductor element 2
0 is mounted.

Markers for adjusting the outer shape are formed on the substrate 30, the insulating sheet 10, and the semiconductor element 20 in advance, and the outer shape is adjusted by using the markers at the time of alignment.

When the insulating sheet 10 is disposed between the semiconductor element 20 and the substrate 30, the electrode pads 22, 31
And the height of the passivation films 23 and 32
A gap is generated between the solder paste 12 and each of the electrode pads 22 and 31. Here, when pressure is applied from above and below so as to sandwich the semiconductor element 20 and the substrate 30, a force spreading in the width direction acts on the resin layer of the insulating sheet 10, and the solder paste 12 in the connection hole 11 is moved right and left. Compression from both sides. Due to this compression, the solder paste 12 enters the upper and lower gaps as shown in FIG. 1D and comes into contact with the electrode pads 22 of the semiconductor element 20 and the electrode pads 31 of the substrate 30.

Here, the whole is heated to 150 ° C. to 170 ° C. to cure the resin of the insulating sheet 10 and
0 and the substrate 30 are bonded and fixed. Finally, the whole 20
By heating the solder paste 12 to about 0 ° C. to 220 ° C. and melting the solder paste 12 by reflow, the solder paste 12 becomes a bump to electrically connect the two electrode pads 22 and 31. Since the flow range of the molten solder paste is limited by the connection holes 11, it does not spread in the width direction, so that the spread in the height direction is constant without dispersion from bump to bump as in the prior art.

According to the method of the above-described embodiment, the shape of the bump formed by the reflow is not a spherical shape as in the related art, but closer to a straight shape. Further, by appropriately selecting the thickness of the insulating sheet 10, a bump having an arbitrary height can be formed without increasing the width of the bump. For this reason, even when the height of the bump is increased, it is possible to cope with high density by keeping the pitch of the bump small. Moreover, since the height of the bumps can be kept constant, all the bumps are connected to the electrode pads 22 and 31 of the semiconductor element 20 and the substrate 30 in the same state,
Connection failure is unlikely to occur, and the electrode pads 22 and 31 can be reliably connected.

[0019]

As described above, according to the method of the present invention, the width of the bump to be formed is limited by reflowing the connection hole formed in the insulating sheet with the bump material being filled. By keeping the pitch of the bumps small, it is possible to cope with high density. In addition, since the height of the formed bumps is kept constant, all the bumps are connected to the electrode pads of the element and the substrate in the same state, and it is possible to prevent the occurrence of connection failure between the electrode pads.

In the case where the element and the substrate are bonded by an insulating sheet, the element and the substrate can be fixed not only at the bump portion but also at the front surface of the sheet. To reduce the burden on
Stronger fixation becomes possible.

[Brief description of the drawings]

FIG. 1 is a process diagram showing step by step a method of mounting a flip-chip device according to an embodiment of the present invention.

FIG. 2 is a process diagram showing step by step a conventional flip-chip element mounting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Insulating sheet 11 Connection hole 12 Solder paste 20 Semiconductor element 21 Active element surface 22 Electrode pad 23 Passivation film 30 Substrate 31 Electrode pad 32 Passivation film

Claims (2)

[Claims] 1. A flip for interposing a bump between an electrode pad formed on an active element surface of an element and an electrode pad of a substrate, melting the bump by reflow, and electrically connecting the two electrode pads. In a chip-type element mounting method, a connection hole penetrating a sheet according to a position of the electrode pad is formed in an insulating sheet, a bump material is filled in the connection hole, and the insulating sheet is connected to the electrode pad. And the connection holes are arranged between the substrate and the element so as to correspond to each other, and the two electrode pads are connected by melting the bump material by reflow. Implementation method. 2. The method according to claim 1, wherein the insulating sheet is a resin sheet for bonding the element and the substrate by heat treatment.