JP2002016168A - Substrate for mounting and semiconductor module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and surely joint the projecting electrode of a semiconductor device to the electrode pad of a substrate for mounting and to mount the semiconductor device with excellent reliability at a high non-defect rate. SOLUTION: For this substrate 3 for mounting, a device mounting area for mounting the semiconductor device 1 provided with the projecting electrode 2 on a lower surface is provided on the upper surface of an insulation substrate and the electrode pad 4 corresponding to the projecting electrode 2 is formed in the device mounting area. The surface of the electrode pad 4 is pressurized by the flat surface of a pressure flattening means and flattened. Since a desired flat mounting surface is simply and easily formed over the entire device mounting area even for the electrode pad 4 formed by a thick film printing method or the like for only the surface of the electrode pad 4 of the device mounting area requiring a flat surface, the projecting electrode 2 of the semiconductor device 1 is stably and surely jointed and the semiconductor device 1 is mounted with excellent reliability at a high-non-defect rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a semiconductor device such as a semiconductor device or a semiconductor device in which a semiconductor device is housed in a semiconductor device housing package by a so-called flip-chip mounting method in the field of information communication and the semiconductor field. More particularly, the present invention relates to a mounting board which is suitable for mounting and has improved reliability and non-defective rate at the time of mounting.

[0002]

2. Description of the Related Art In recent years, as a method of mounting a semiconductor device such as a semiconductor device or a semiconductor device containing a semiconductor device on a mounting substrate used as a wiring substrate such as a circuit board or a package for housing a semiconductor device, a so-called flip-chip mounting method is used. The law is becoming heavily used. This technique is
For example, a protruding electrode made of gold, a solder material, or the like is provided on an electrode on a mounting surface side of a semiconductor device, and an electrode pad is provided on a mounting substrate on which the semiconductor device is mounted, at a position facing the protruding electrode. In advance, the semiconductor device is placed with the projecting electrodes of the semiconductor device and the electrode pads of the mounting substrate aligned and then heated and pressed, or ultrasonic energy is applied to the projecting electrodes and the electrode pads via the semiconductor device. By applying, the protruding electrode and the electrode pad are joined,
The semiconductor device is mounted face-down on a mounting substrate.

In such flip-chip mounting, various methods are used for mechanically bonding and electrically connecting the electrode pads of the mounting substrate and the protruding electrodes of the semiconductor device.

For example, as shown in a side view of FIG. 4A, a semiconductor element 1 as a semiconductor device is prepared by applying, for example, a silver paste 5 to the tip of a protruding electrode 2 formed on the lower surface thereof. 3 is placed in contact with the electrode pad 4 formed in the element mounting area on the upper surface of the semiconductor element 1, and as shown in the same side view in FIG. Means 6) There is a method in which the projecting electrode 2 and the electrode pad 4 are connected via the silver paste 5 or the like by heating and pressing by 6.

Further, the protruding electrode of the semiconductor element is formed of gold, and the electrode pad formed on the mounting portion of the mounting substrate is also formed of gold, so that the protruding electrode and the electrode pad can be formed without using silver paste or a solder material. There is also a method in which ultrasonic waves are applied by a tool capable of aligning the ultrasonic waves and applying ultrasonic waves thereto, and the ultrasonic waves are connected to the ultrasonic waves only by heating.

In order to mount a semiconductor device with high reliability in these methods, it is necessary that the heights of the projecting electrodes of the semiconductor device are uniform and the heights of the electrode pads on the mounting board are uniform. It is very important that the electrode pads have a flat surface.

[0007]

However, in the conventional mounting substrate used in the above-described flip-chip mounting method, the bump electrodes formed on the semiconductor device have a slight variation in height. As a result, the height variation and the flatness variation of the electrode pads formed on the mounting substrate were varied, so that when the bump electrodes of the semiconductor device were joined to the bumps, the bump electrodes and the electrode pads could be brought into good contact. There is a problem in that the connection between the protruding electrode and the electrode pad may be failed.

In order to cope with this, before the projecting electrodes of the semiconductor device are aligned with the electrode pads of the mounting substrate, the projecting electrodes of the semiconductor device are pressed on a stage of good flatness made of metal, glass or the like. In this case, the height of the protruding electrodes is made uniform by leveling.

However, on the mounting substrate side,
In order to make the height of the electrode pads uniform and to make the surface flat, use a substrate with a sufficiently low flatness, and further control the height and flatness by forming electrode pads and wiring conductors with thin films. It was necessary to do. Therefore, mirror polishing is performed to reduce the flatness of the substrate surface, and the flatness of the substrate is increased by forming electrode pads and wiring conductors by a thin film process, and there is no variation in height and flatness of the electrode pads. 2. Description of the Related Art A wiring board as a mounting board and a package for housing a semiconductor element have been manufactured.

However, in this case, the production of such a mounting substrate requires a very complicated and long process, and the production of the mounting substrate takes a long time and the production cost increases. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a semiconductor device including a semiconductor element in a wiring board or a mounting board used for a package for housing a semiconductor element. To provide a mounting substrate that can be reliably and at a high yield rate and that can bond a bump electrode of a semiconductor device to an electrode pad of a mounting substrate during so-called flip-chip mounting, and that can be manufactured in a short time and at low cost. It is in.

Another object of the present invention is to provide a flip chip mounting method in which a protruding electrode of a semiconductor device and an electrode pad of a mounting substrate are bonded with high reliability and a high yield rate.
An object of the present invention is to provide a semiconductor module using a mounting substrate that can be manufactured in a short time and at low cost.

[0013]

According to the present invention, there is provided a mounting board comprising:
A mounting substrate on which a semiconductor device having a projecting electrode on a lower surface is mounted on an upper surface of an insulating substrate, and an electrode pad corresponding to the projecting electrode is formed in the device mounting region; The surface of the pad is flattened by pressing with a flat surface of the pressing flattening means.

Further, in the mounting board of the present invention, in the above structure, a wiring conductor electrically connected to the electrode pad is formed in the device mounting area, and the surface of the wiring conductor is also formed by the pressing flattening means. Characterized by being flattened by pressing on the flat surface.

Further, in the semiconductor module of the present invention, a semiconductor device having a protruding electrode on a lower surface is mounted in the device mounting area of the mounting substrate having the above-described configuration by bonding the protruding electrode to the electrode pad. It is characterized by the following.

[0016]

According to the mounting substrate of the present invention, the surface of the electrode pad formed in the device mounting area and facing the bump electrode of the semiconductor device is pressed by the flat surface of the pressing flattening means. Because of the flatness of the electrode pad, a conventional mounting substrate with a flat surface of the electrode pad is manufactured in a complicated and long process, but only the surface of the electrode pad in the device mounting area where a flat surface is required. As for the semiconductor device, it is possible to easily and easily form a desired flat mounting surface having a uniform surface height over the entire device mounting region even with respect to an electrode pad formed by a thick film printing method or the like. Can be bonded stably and reliably, and the semiconductor device can be mounted with high reliability and a high yield rate.

When a wiring conductor electrically connected to the electrode pad is formed in the device mounting area, the surface of the wiring conductor is flattened by pressing the flat surface of the pressing flattening means together with the electrode pad. With this arrangement, only the surface of the electrode pads and wiring conductors in the device mounting area where a flat surface is required, the wiring conductors formed by the thick film printing method and the electrode pads can be easily and simply spread over the entire device mounting area. Since a desired flat mounting surface having the same surface height can be easily formed, the wiring conductor and the semiconductor device, which are generated due to the height variation and the flatness variation of the surface of the wiring conductor in the device mounting area, can be formed. The bumps of the semiconductor device can be stably and surely joined without causing troubles such as contact or short circuit of the semiconductor device, and the semiconductor device can be mounted with high reliability and a high yield rate. It is possible.

According to the semiconductor module of the present invention, since the semiconductor device is mounted on the mounting substrate of the present invention, the projecting electrodes of the semiconductor device and the electrode pads of the mounting substrate can be stably and reliably mounted. The semiconductor device can be mounted in a good connection state by reliable bonding, a highly reliable semiconductor module can be manufactured, and a high yield rate can be achieved.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view showing an example of an embodiment of a mounting substrate of the present invention and a semiconductor module using the same, showing a state where the semiconductor device 1 is mounted in a device mounting area of the mounting substrate 3. I have.

In FIG. 1, reference numeral 1 denotes a semiconductor device such as a semiconductor device or a semiconductor device in which the semiconductor device is housed in a semiconductor device housing package, and a plurality of projecting electrodes 2 are formed on the lower surface. Reference numeral 3 denotes a mounting substrate having predetermined circuit wiring formed on an insulating substrate, and a mounting substrate having a device mounting area on the upper surface on which the semiconductor device 1 is mounted. There are a plurality of electrode pads formed corresponding to the protruding electrodes 2, respectively. The electrode pad 4 is formed by, for example, a thick film printing method without using a thin film process, and a wiring conductor for leading out from the device mounting area to the outside is also integrally formed. The electrode pads 4 and the wiring conductors formed by the thick film printing method or the like as described above are usually formed because there is a variation in the film thickness microscopically, as shown outside the device mounting area. The surface is not flat when left as it is. In the mounting substrate 3 of the present invention, the surface of the electrode pad 4 to which the bump electrode 2 is bonded is pressed against the flat surface of the pressure flattening means (not shown) before the semiconductor device 1 is mounted. Since the electrode pad 4 in the device mounting area has a flat cross-sectional shape since it is flattened microscopically by pressing.

As a result, it is possible to easily and easily form a desired flat mounting surface having the same surface height over the entire device mounting area even for the electrode pad 4 formed by the thick film printing method or the like. As a result, all the protruding electrodes 2 are stably brought into contact with the surface of the electrode pad 4 in a good state and are securely joined, and the semiconductor device 1 can be mounted with high reliability and a high yield. In addition, a semiconductor module in which the semiconductor device 1 is mounted on such a mounting substrate 3 can be similarly manufactured with high reliability and a high yield.

An example of a method of flattening the surface of the electrode pad 4 in the device mounting area of the mounting substrate 3 of the present invention will be described with reference to FIGS. 2 and 3 are side views each showing an example of the method.

In FIG. 2, reference numeral 3 denotes a mounting substrate in which predetermined circuit wiring is formed on an insulating substrate, and 4 denotes a projecting electrode 2 on the lower surface of the semiconductor device 1 in a device mounting area on the upper surface of the mounting substrate 3.
And a plurality of electrode pads respectively formed in correspondence with. The electrode pads 4 are formed by a thick-film printing method together with wiring conductors electrically connected thereto without using a thin-film process in order to obtain a mounting substrate 3 that can be manufactured at low cost. As can be seen, the film thickness variation is very large. Reference numeral 7 denotes a pressure flattening means processed to have a flat surface having substantially the same size as the device mounting area on the upper surface of the mounting substrate 3. In the mounting substrate 3 of the present invention, the surface of the electrode pad 4 in the device mounting area is flattened to a desired height and flatness by pressing the flat surface of the pressing flattening means 7. . Further, according to the pressure flattening means 7, when the electrode pad 4 and the wiring conductor electrically connected thereto are formed in the device mounting area, the surface of the wiring conductor also has a flat surface. To flatten the same height and flatness as the surface of the electrode pad 4.

In FIG. 3, reference numeral 3 denotes a mounting substrate, and reference numeral 4 denotes electrode pads similar to those shown in FIG. Reference numeral 8 denotes a pressure flattening means which is processed so as to have a flat surface at the same position as the electrode pad 4 on the mounting substrate 3 at substantially the same size. By using such a pressure flattening means 8, the surface of the electrode pad 4 in the device mounting area can be selectively flattened.

By pressing the surface of the electrode pad 4 in the device mounting area and the surface of the wiring conductor in the device mounting area with the flat surface by using such pressure flattening means 7 and 8 as shown in FIG. As described above, the surface of the electrode pad 4 can be made flat so that the surface to which the protruding electrode 2 of the semiconductor device 1 is joined is adjusted to a desired height and flatness, and is connected to the electrode pad 4. The surface of the wiring conductor can also be made flat without height variations or irregularities.

When the surface of the electrode pad 4 is flattened by the pressing and leveling means 7 and 8 as described above, the variation in height and the variation in flatness of each surface are, for example, 20.
It is desirable to be within μm. As the operation speed and the frequency of the semiconductor device 1 such as a high-frequency semiconductor element have been increased, the size of the protruding electrode 2 provided on such a semiconductor device 1 has a diameter of about 80 μm and a height of about 80 μm. Those having a size of about 40 μm have been used. In order to suppress the variation in height of the projecting electrodes 2 having such a size, when the projecting electrodes 2 are pressed on a flat surface to make the height uniform, when the projecting electrodes 2 made of gold, solder, or the like are deformed by pressing. Deformation can be made relatively easily up to about 50% of its height, but if pressure is applied further, deformation or destruction may occur on the semiconductor device 1 side. Therefore, when the heights of the protruding electrodes 2 are made uniform, it is preferable to limit the pressure to about 20 μm. In order to obtain a good bonding state with respect to the protruding electrodes 2 having such a height, It is desirable to keep the height variation and the flatness variation of the electrode pad 4 within 20 μm.

In the mounting board 3 of the present invention, the electrode pad 4 and the wiring conductor electrically connected thereto are formed by forming the protruding electrode 2 of Au, and the surface of the electrode pad 4 to which it is joined by thermocompression bonding or the like. Since it is preferable that the conductor is also formed of Au, a conductor formed by sequentially laminating W / Ni / Au, a conductor formed by sequentially laminating Mo / Ni / Au, or the like is used.

As the pressure flattening means 7 and 8, the flat surface for pressing the surface of the electrode pad 4 is mirror-finished.
For example, a ceramic tool or a metal tool made of SUS or cemented carbide may be used.

The magnitude of the pressure when the electrode pads 4 are flattened by the pressure flattening means 7 and 8 depends on the material, size, thickness, etc. of the electrode pads 4, as well as desired height variations and the like. What is necessary is just to set suitably according to the value of the flatness variation. Further, the electrode pad 4 may be heated at the same time as the pressing.

[0030]

Next, specific examples of the mounting board of the present invention and a semiconductor module using the same will be described.

First, as the insulating substrate of the mounting substrate, a thickness of 0.
A 6 mm alumina ceramic substrate was used. In the device mounting area on the substrate, the Au layer on the surface was 5 μm thick at a position facing the protruding electrodes formed on the lower surface of the semiconductor element as the semiconductor device. Was provided with an electrode pad made of a 25 μm W / Ni / Au layer. In addition, in the device mounting area, in addition to the electrode pads, a bias wiring and an RF wiring for high-frequency transmission were also formed of a W / Ni / Au layer having an Au layer on the surface having a thickness of 5 μm and an overall thickness of 25 μm. Each of the electrode pad / bias wiring and the RF wiring was formed by a thick film printing method without using a thin film process.

On the other hand, a semiconductor element as a semiconductor device
The device material used was GaAs having a thickness of 0.1 mm, on the lower surface of which a plurality of protruding electrodes made of gold having a diameter of 60 μm were formed. Further, as a pressure flattening means for flattening the surface of the electrode pad in the device mounting area, a ceramic tool having the same size as the semiconductor element and having a flat surface whose surface was mirror-polished was prepared.

Then, the mounting substrate is mounted on a stage of a flip chip mounting machine, and the ceramic tool is mounted on a chip mounting head of the mounting machine, and it is necessary to display about 200 N (in SI unit system. The surface of the electrode pads and wiring conductors in the device mounting area was flattened with a pressure of about 9.8 N.) to improve their flatness and height variation.

After the step, while the substrate is heated to 200 ° C., the semiconductor elements are aligned, and the respective projecting electrodes are brought into contact with the corresponding electrode pads, and ultrasonic waves are applied to the semiconductor elements. The semiconductor element was flip-chip mounted by bonding the electrode to the electrode pad, and the semiconductor module A of the present invention using the mounting substrate of the present invention was manufactured.

As a comparative example, a device was prepared using the same semiconductor element and mounting substrate as described above, but without performing the step of flattening the surface of the electrode pad in the device mounting area. This mounting substrate is placed on the stage of a flip chip mounting machine, and while the substrate is heated to 200 ° C., the semiconductor elements are aligned and each protruding electrode is brought into contact with the corresponding electrode pad, and ultrasonic waves are applied to the semiconductor element. The semiconductor element was flip-chip mounted by bonding the protruding electrode to the electrode pad by applying a voltage to the semiconductor chip B, thereby producing a semiconductor module B.

Further, as another comparative example, using the same semiconductor element and the mounting substrate on which the electrode pads and the wiring conductors are formed by the thin film process as described above, the surface of the electrode pads in the device mounting area is flattened. Those which did not perform the process were prepared. This mounting substrate is placed on the stage of a flip chip mounting machine, and while the substrate is heated to 200 ° C., the semiconductor elements are aligned and each protruding electrode is brought into contact with the corresponding electrode pad, and ultrasonic waves are applied to the semiconductor element. The semiconductor element was flip-chip mounted by bonding the protruding electrode to the electrode pad by applying the voltage to the semiconductor chip C, thereby producing a semiconductor module C.

Each of these semiconductor modules A
When B and C were examined for the presence or absence of mounting failure, no mounting failure occurred in the semiconductor module A, but about 80% in the semiconductor module B.
%, A bonding failure was caused due to a variation in the height of the electrode pad, and a mounting failure was observed. In addition, in the semiconductor module C, as in the case of the semiconductor module A of the present invention, no occurrence of mounting failure was observed.

As a result, according to the semiconductor module A of the present invention, as compared with the semiconductor module B in which the step of flattening the device mounting area was not performed, no mounting failure occurred and the connection reliability was improved. You can see that there is. According to the semiconductor module A of the present invention, a thin film whose process is very complicated and costly is high only by performing a simple and easy process of flattening the surface of the electrode pad in the device mounting area by the pressure flattening means. It has been found that the semiconductor element can be mounted with the same reliability as the semiconductor module C using the mounting substrate on which the electrode pads and the wiring conductors are formed by the process.

In the semiconductor module A, the bonding strength between the protruding electrode of the semiconductor element and the electrode pad of the mounting substrate was a sufficient bonding strength equivalent to that of the semiconductor module C.

Thus, it was confirmed that according to the mounting substrate of the present invention, a semiconductor module having a high yield rate and a high connection reliability can be manufactured.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. Various changes and improvements may be made without departing from the gist of the present invention. No problem. For example, in the embodiment, a ceramic tool is used for the pressure flattening means, but it goes without saying that a metal tool may be used.

[0042]

As described above, according to the mounting board of the present invention, the surface of the electrode pad formed in the device mounting area, which faces the bump electrode of the semiconductor device, is formed by the flat surface of the pressure flattening means. Because it is flattened by pressurizing, the surface of the electrode pad in the device mounting area that requires a flat surface can be easily and easily applied to the electrode pad formed by thick film printing etc. over the entire device mounting area. Since a desired flat mounting surface can be easily formed, the bump electrodes of the semiconductor device can be stably and surely joined, and the semiconductor device can be mounted with high reliability and a high yield rate.

Also, when a wiring conductor electrically connected to the electrode pad is formed in the device mounting area, the surface of the wiring conductor is also flattened by pressing the flat surface of the pressing flattening means. Only the surface of the electrode pad and the wiring conductor in the device mounting area where a flat surface is required, and the wiring flat formed by the thick film printing method can be easily and easily provided with the electrode pad together with the electrode pad over the entire device mounting area. Since a stable mounting surface can be formed, problems such as contact or short-circuit between the wiring conductor and the semiconductor device caused by variations in the height and flatness of the surface of the wiring conductor in the device mounting area may occur. In addition, the bumps of the semiconductor device can be stably and reliably joined, and the semiconductor device can be mounted with high reliability and a high yield rate.

Further, according to the semiconductor module of the present invention, since the semiconductor device is mounted on the mounting substrate of the present invention, the projecting electrodes of the semiconductor device and the electrode pads of the mounting substrate can be stably and reliably mounted. The semiconductor device can be mounted in a good connection state by reliable bonding, a highly reliable semiconductor module can be manufactured, and a high yield rate can be achieved.

As described above, according to the present invention, when a semiconductor device is flip-chip mounted on a mounting substrate, the projection electrodes of the semiconductor device and the electrode pads of the mounting substrate can be bonded with high reliability and a high yield. In addition, a mounting substrate that can be manufactured in a short time and at low cost can be provided.

Further, according to the present invention, the bump electrodes of the semiconductor device and the electrode pads of the mounting substrate can be bonded to each other with high reliability and a high yield rate, thereby enabling flip-chip mounting.
A semiconductor module using a mounting substrate that can be manufactured in a short time and at low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of an embodiment of a mounting board and a semiconductor module using the same according to the present invention.

FIG. 2 is a side view showing an example of a method for flattening the surface of an electrode pad on a mounting substrate according to the present invention.

FIG. 3 is a side view showing another example of a method for flattening the surface of an electrode pad in a mounting substrate of the present invention.

FIGS. 4A and 4B are side views for explaining a step of flip-chip mounting a semiconductor element.

[Explanation of symbols]

 1 semiconductor device 2 projecting electrode 3 mounting substrate 4 electrode pad 7 8 pressure flattening means

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 29, 2000 (2006.2.
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

Then, the mounting substrate is mounted on a stage of a flip chip mounting machine, and the ceramic tool is mounted on a chip mounting head of the mounting machine. Were flattened by pressing, and their flatness and height variation were improved.

Claims (3)

[Claims] 1. A mounting substrate, comprising: a device mounting region on a top surface of an insulating substrate on which a semiconductor device having a protruding electrode on a lower surface is mounted; and an electrode pad corresponding to the protruding electrode is formed in the device mounting region. A mounting substrate, wherein a surface of the electrode pad is flattened by pressing with a flat surface of a pressing flattening means. 2. A wiring conductor electrically connected to the electrode pad is formed in the device mounting area, and the surface of the wiring conductor is also flattened by pressing the flat surface of the pressing flattening means. The mounting substrate according to claim 1, wherein: 3. A semiconductor device having a projecting electrode on a lower surface is mounted on the device mounting region of the mounting substrate according to claim 1 or 2 by bonding the projecting electrode to the electrode pad. Semiconductor module.