JP2000114318A - Semiconductor chip, its manufacture, sheet for applying flux, and method for mounting semiconductor chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flip-chip mounting method by which the need for a flux residue cleaning removal process can be eliminated, and in addition, adverse effects caused by the residue of flux can be removed. SOLUTION: A flux solution layer 5 for the concentration of flux in the layer 5 becomes lower along towards the overlaying layer from the underlying layer which is a solid-state water soluble flux layer 4 formed into a uniform thickness is formed by applying water in uniform thickness to the layer 4. A ball bump 1, formed on the electrode 3 of a semiconductor chip, is dipped in the flux solution layer 5 and pulled up from the layer 5. Consequently, the flux solution 2 in the layer 5 is applied to the entire surface of the ball bump 1, in such a way that the concentration of the flux gradually becomes lower along the electrode 3 from the front end section of the bump 1. Then the semiconductor chip is mounted on a circuit board through flip-chip welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to (1) a semiconductor chip mounted on a circuit board by a flip-chip method, more specifically, a form of applying flux to solder bumps formed on electrodes of the semiconductor chip. The present invention relates to a method of manufacturing the semiconductor chip, that is, a method of applying a flux to solder bumps, (3) a sheet for applying a flux which is effective for performing the applying method, and (4) a method of mounting the semiconductor chip on a circuit board. .

[0002]

2. Description of the Related Art Conventionally, as one of the mounting techniques of a semiconductor integrated circuit such as an LSI, a flip chip method (flip chip method) has been proposed.
bonding process). In this mounting method, solder bumps are formed on the electrodes of the semiconductor chip (integrated circuit chip), and solder bumps are also formed on the electrodes of the circuit board, so that the electrodes of the semiconductor chip and the electrodes of the circuit board are aligned. After that, the chip and the substrate are temporarily press-bonded by the adhesiveness of the flux at a temperature lower than the melting point of the solder bumps, and then the press-bonded material is passed through a reflow furnace to melt and fix the solder bumps. And finally, a sealing resin is injected into the interface between the chip and the substrate to complete the process.

[0003] However, in this mounting method, the above-mentioned flux washing and removing step is required.
There has been a problem that mounting costs are high. As a mounting technique that solves this problem, there is one disclosed in Japanese Patent Application Laid-Open No. 7-78847 (title of the invention: semiconductor chip mounting method). In this mounting technology, the flux is applied only to the tip of the solder bumps of the chip, and then the chip is flip-chip bonded to the substrate, eliminating the above-mentioned flux washing and removing step and eliminating the adverse effects caused by the flux residue. are doing.

[0004]

In the case where the solder bump is a spherical bump 11 (heat-formed bump) as shown in FIG. 5, the spread of the flux on the bump proceeds smoothly. Is achieved. However, the ball bumps 21 (bumps formed by the wire bonding method) formed by wire bumping as shown in FIG. 6 are not spherical, but have a shape in which a part of the wire protrudes at the center of the disk portion. Therefore, in the case of the spherical bump 11, even if a suitable amount of flux is applied to the tip of the ball bump 21, it is not expected that the entire bump 21 is covered by the rapid spread of the flux when heated.

[0005] For this reason, the desired action of the flux such as removal of the oxide film from the metal surface cannot be obtained. In order to eliminate this problem, it was necessary to apply the flux to the entire bump by pressing the entire bump against the flux pool. 5 and 6, reference numerals 12 and 22 denote LSI electrodes.

As described above, the mounting method disclosed in the above-mentioned patent publication cannot be applied to bumps formed by wire bumping. Also, if the flux is applied to the entire bump, the amount of the flux tends to be excessive, and in this case, the flux spreads to the chip surface, and the cohesive force tilts the chip, which may cause a short circuit between adjacent electrodes. Conversely, if the amount of the flux is too small, the upper portion of the bump is not covered with the flux and an oxide film is formed at the time of connection, so that there is a problem that the pump shape after the connection is distorted.

Accordingly, an object of the present invention is to provide a method for applying a required amount of flux to a solder bump by a simple method when mounting a semiconductor chip having a solder bump formed by wire bumping on a circuit board by a flip chip method. An object of the present invention is to provide a flip-chip type mounting technique that can omit a step of cleaning and removing a residue and can eliminate an adverse effect caused by a flux residue.

That is, the present invention is used for (1) a method of applying a flux to a solder bump formed on an electrode of a semiconductor chip, (2) a method of applying a flux to the solder bump for that purpose, and (3) a method of applying the method. A flux application sheet and (4) a method for mounting a semiconductor chip on a circuit board are provided with a simple configuration.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor chip mounted on a circuit board by a flip chip method, wherein a solder bump is formed on an electrode, and a flux solvent solution is applied to the solder bump. Wherein the solvent solution of the flux is applied such that the concentration of the flux dissolved in the solvent gradually decreases from the tip of the solder bump toward the electrode.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor chip according to the first aspect, wherein a solder bump is formed on an electrode of the semiconductor chip by an appropriate method, and a solder bump is formed on an appropriate member. Apply flux to
Forming a layer made of a solvent that dissolves the flux on the flux, and by directly contacting the solvent layer and the flux, on the flux, the flux concentration increases with distance from the interface between the solvent layer and the flux to the solvent layer side. After forming a flux solution layer, the solder bump of the semiconductor chip is immersed in the flux solution layer from the tip end side of the solder bump, and then pulled up.

According to a third aspect of the present invention, in forming the flux solution layer on the flux in the second aspect, a water-permeable sheet impregnated with a solvent is overlapped on the flux by contacting the flux. Alternatively, after the water permeable sheet is overlaid on the flux in contact with the flux, the water permeable sheet is impregnated with a solvent.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor chip according to the third aspect, wherein a solid water-soluble flux is used as the flux, and water is used as the solvent.

According to a fifth aspect of the present invention, there is provided a flux coating sheet for use in the method of manufacturing a semiconductor chip according to the fourth aspect, wherein the flux is applied to a solid water-soluble flux in contact with the flux. It is characterized in that the sheets are stacked and integrated.

According to a sixth aspect of the present invention, when a semiconductor chip is mounted on a circuit board by a flip chip method, a solder bump is formed on an electrode of the semiconductor chip by an appropriate method, and the semiconductor chip is mounted on an appropriate member. The flux is applied, a layer made of a solvent that dissolves the flux is formed on the flux, and the solvent layer and the flux are brought into direct contact with each other on the flux, from the interface between the solvent layer and the flux to the solvent layer side. Forming a flux solution layer in which the flux concentration decreases as the distance from the solder bump increases, the solder bump of the semiconductor chip is immersed in the flux solution layer from the tip end side of the solder bump, and then pulled up, so that a flux solvent solution is applied to the solder bump. After manufacturing the semiconductor chip, the semiconductor chip is mounted on the circuit board. Characterized by connection-Chip method.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the following, a ball bump formed by wire bumping (FIG. 6) is illustrated as an example of the solder bump, but the present invention is not limited to this, and may be applied to a normal spherical bump (FIG. 5). it can.

First Embodiment (Claim 1) FIG. 1 relates to a main part of a semiconductor chip, and is a schematic cross section showing a solder bump 1 having a flux solution 2 having a predetermined flux concentration distribution applied to the entire surface. FIG.
Reference numeral 3 denotes an LSI electrode provided on a semiconductor chip (not shown). The flux solution 2 is obtained by dissolving a paste or solid flux in an appropriate solvent, and the concentration of the flux is from the tip of the bump 1 (the end farther from the LSI electrode 3) toward the LSI electrode 3. It is applied to the solder bump 1 so as to gradually decrease.

Usually, the above-mentioned paste-like flux mainly comprises a base resin, an activator and a solvent for dissolving them, and the above-mentioned solid flux mainly comprises a base resin and an activator. Further, as the flux, a flux prepared by dissolving a water-soluble base resin and an activator in water can also be used. In this case, water may be used as the solvent for applying the flux solution 2.

By applying the flux to the solder bump 1 as shown in FIG. 1, a sufficient amount of flux to cover the connection electrode is secured at the tip of the bump. In addition, since a necessary minimum amount of flux is applied to portions other than the tip of the bump, the desired effect of the flux can be obtained, and the step of cleaning and removing the flux residue is not required.

Embodiment 2 (Claim 2) FIG. 2 is a schematic sectional view showing a method of applying the flux solution 2 to the surface of the solder bump 1 in the form of FIG. 1, and this method will be described below. As shown in FIG. 2A, solder bumps 1 are formed on LSI electrodes 3 of a semiconductor chip (not shown). On the other hand, a paste-like or solid flux layer 4 is formed with a uniform thickness on a shallow dish (not shown) having a flat bottom surface. For example, after applying a paste-like flux to the bottom surface to an appropriate thickness, the applied thickness of the flux is made uniform with a squeegee (not shown), or a liquid flux having a high concentration and good fluidity is applied to the plate. , And an appropriate amount of the solvent is removed by evaporation.

Next, a solvent for dissolving the flux layer 4 is gently poured into the above-mentioned dish, and the solvent is brought into contact with the flux layer 4 to form a solvent layer having a thickness of, for example, 50 to 500 μm. Let stand still. As a result, the surface portion of the flux layer 4 gradually dissolves and diffuses in the solvent layer, so that the flux concentration on the flux layer 4 gradually decreases from the surface side of the flux layer 4 toward the upper layer of the solvent layer. 5 are formed. When the flux layer 4 is water-soluble, water can be used as the solvent.

Next, as shown in FIGS. 2A and 2B, the solder bump 1 of the semiconductor chip is brought close to the flux solution layer 5 from the tip end side, and almost the entire solder bump 1 is immersed in the flux solution layer 5. . Then, FIG.
The semiconductor chip is gradually pulled up as shown in FIG. As a result, the flux solution layer 5 (that is, the flux) is applied to the entire surface of the solder bump 1 in a form in which the flux concentration distribution of the flux solution layer 5 is transferred to the solder bump 1 almost as it is. In this case, the entire solder bump 1 may be immersed in the flux solution layer 5, but without doing so, there is no problem since the flux solution spreads over the surface of the solder bump 1, and the flux is applied in the form shown in FIG. Can be applied.

As described above, in this embodiment, a coating of a solvent that dissolves the coating is formed on the flux layer 4 and the coating is brought into direct contact with the flux layer 4.
Since the flux solution layer 5 having a predetermined flux concentration distribution is formed on the flux layer 4, the flux application form shown in FIG. 1 can be obtained by a simple operation.

Embodiment 3 (Claims 3 and 4) FIG. 3 is a schematic cross-sectional view showing another method for obtaining the flux application form of FIG. In this embodiment, a water-permeable sheet 6, for example, a paper having a thickness of 200 μm, is immersed in a solvent that dissolves the flux layer 4 to impregnate the solvent. Then, the water permeable sheet 6 is left on the paste-like or solid flux layer 4. As a result, the surface portion of the flux layer 4 gradually dissolves and diffuses in the solvent layer, so that the flux concentration on the flux layer 4 gradually decreases from the surface side of the flux layer 4 toward the upper layer of the solvent layer. Layer 5 is formed. Then, FIG.
(A) After substantially the entire solder bump 1 is pressed against the water-permeable sheet 6 in the order shown in (b), the semiconductor chip is gradually pulled up as shown in FIG. 3 (c).

It should be noted that instead of the above method, the flux layer 4
After stacking the permeable sheet in contact with this on top,
The flux solution layer 5 shown in FIG. 3A can also be formed by gently spraying a solvent on the water-permeable sheet and impregnating the water-permeable sheet with the solvent.

In these embodiments, when the solvent layer is formed, a water-permeable sheet impregnated with a solvent is used. Therefore, the movement and stirring of the solvent in the water-permeable sheet can be suppressed. The flux solution layer 5 having distribution can be formed and maintained more reliably, and the flux is transferred (coated) to the solder bumps.
Operation becomes easier. Further, by using a solid water-soluble flux as the flux and water as the solvent, handling becomes easier, and the operation of transferring the flux to the solder bumps can be performed more easily.

Embodiment 4 (Claim 5) FIG. 4 shows a flux coating in which a water-permeable sheet 6, for example, a paper having a thickness of 300 μm, is laminated on a solid flux layer 4 in contact therewith and integrated. FIG. 2 is a schematic cross-sectional view showing the use sheet 7. This sheet 7 is for forming the flux solution layer 5 shown in FIG. 3A, and when used, the water-permeable sheet 7 may be impregnated with the solvent for the flux layer 4. In order to produce the sheet 7, a paste-like flux is applied to one surface of the water-permeable sheet 6 to a uniform thickness with a squeegee, and then the solvent in the flux is dried and removed.

In this embodiment, the solid flux and the water-permeable sheet are integrated, so that the handling is convenient, and the desired flux concentration distribution can be obtained by a simple operation of impregnating the water-permeable sheet with a flux solvent. A flux solution layer having the same can be formed. Further, by using a water-soluble flux as the solid flux, a desired flux solution layer can be formed more easily.

When a semiconductor chip provided with solder bumps 1 coated with flux in the form shown in FIG. 1 is mounted on a circuit board by a flip chip method, the electrodes of the semiconductor chip and the electrodes of the circuit board are connected to each other. After the semiconductor chip and the circuit board are pre-pressed by the adhesiveness of the flux at a temperature lower than the melting point of the solder bump, the solder bump is melted and fixed by passing the press-bonded product through a reflow furnace. The process is completed by injecting a sealing resin into the interface between the chip and the substrate (claim 6). In this case, it is not necessary to wash and remove the flux residue with a solvent.

[0029]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) In a flux application mode in which a flux solvent solution is applied to a solder bump formed on an electrode of a semiconductor chip, the flux concentration of the flash solvent solution gradually decreases from the tip of the solder bump toward the electrode. Therefore, a sufficient amount of flux to cover the connection electrode is secured at the tip of the bump, and the mounting form of the semiconductor chip on the circuit board is accurate. Further, since the amount of excess flux can be minimized, the step of cleaning and removing the flux residue can be omitted. Besides,
The adverse effect caused by the flux residue does not occur.

(2) A flux solution having a predetermined flux concentration distribution on the flux by forming a layer made of a solvent that dissolves the flux on the flux and directly contacting the solvent layer with the flux. Since the layer is formed, the flux application form according to claim 1 can be obtained by a simple operation.

(3) Claim 3 Since a water-permeable sheet impregnated with a solvent is used in forming the flux solution layer, the movement and stirring of the solvent in the water-permeable sheet can be suppressed, so that a desired flux concentration distribution can be obtained. Can be more reliably formed, and the operation of transferring (applying) the flux to the solder bumps becomes easier.

(4) Claim 4 Since a solid water-soluble flux is used as the flux and water is used as the solvent, the handling is further facilitated, and the operation of transferring the flux to the solder bumps can be performed more easily.

(5) Claim 5 Since a water-permeable sheet is laminated on a solid flux in contact with the solid flux to form an integrated flux coating sheet, handling is convenient, and a flux solvent is applied to the water-permeable sheet. By a simple operation of impregnation, a flux solution layer having a desired flux concentration distribution can be formed. By using a water-soluble flux as the solid flux, a desired flux solution layer can be formed more easily.

(6) Claim 6 In this method of mounting a semiconductor chip, the semiconductor chip on which the solder bump having the flux application form according to claim 1 is formed is mounted on the circuit board by a flip chip method. The mounting form of the semiconductor chip becomes accurate, the step of cleaning and removing the flux residue can be omitted, and the adverse effect due to the flux residue does not occur.

The invention according to claims 1 to 6 is not limited to the above-mentioned ball bump, but can be applied to the above-mentioned spherical bump as required.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a solder bump to which a flux solution having a predetermined flux concentration distribution is applied according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a method for obtaining a flux application form shown in FIG. 1 according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing another method for obtaining the flux application form shown in FIG. 1 according to still another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing a flux application sheet according to still another embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a spherical solder bump.

FIG. 6 is a schematic sectional view showing a solder bump (ball bump) formed by wire bumping.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solder bump 2 Flux solution 3 LSI electrode 4 Flux layer 5 Flux solution layer 6 Water permeable sheet 7 Flux coating sheet 11 Spherical bump 12 LSI electrode 21 Ball bump 22 LSI electrode

Claims (6)

[Claims] 1. A semiconductor chip mounted on a circuit board by a flip chip method, wherein solder bumps are formed on electrodes, and a flux solvent solution is applied to the solder bumps. A semiconductor chip, wherein a solvent solution of the flux is applied so that the concentration gradually decreases from the tip of the solder bump toward the electrode. 2. The method of manufacturing a semiconductor chip according to claim 1, wherein solder bumps are formed on electrodes of the semiconductor chip by an appropriate method, and a flux is applied on an appropriate member. Forming a layer composed of a solvent that dissolves the solvent layer, and by directly contacting the solvent layer and the flux, on the flux, a flux solution in which the flux concentration decreases as the distance from the interface between the solvent layer and the flux to the solvent layer side decreases A method of manufacturing a semiconductor chip, comprising forming a layer, immersing solder bumps of the semiconductor chip in the flux solution layer from the tip end side of the solder bumps, and then pulling up. 3. The method according to claim 2, wherein, when forming the flux solution layer on the flux, a water-permeable sheet impregnated with a solvent is brought into contact with the flux and overlapped with the flux, or the water-permeable sheet is placed on the flux. A method for manufacturing a semiconductor chip, comprising: impregnating a water-permeable sheet with a solvent after contacting and stacking. 4. The method according to claim 3, wherein a solid water-soluble flux is used as the flux and water is used as the solvent. 5. A flux application sheet comprising a solid water-soluble flux and a water-permeable sheet laminated on the solid water-soluble flux in contact therewith. 6. When a semiconductor chip is mounted on a circuit board by a flip chip method, solder bumps are formed on electrodes of the semiconductor chip by an appropriate method, and a flux is applied on an appropriate member, and the flux is applied on the flux. Forming a layer composed of a solvent that dissolves, on the flux by directly contacting the solvent layer and the flux, a flux solution layer whose flux concentration decreases as the distance from the interface between the solvent layer and the flux to the solvent layer side decreases Is formed, and the solder bump of the semiconductor chip is immersed in the flux solution layer from the tip end side of the solder bump, and then pulled up, to produce a semiconductor chip in which a flux solvent solution is applied to the solder bump. Are connected to the circuit board by a flip-chip method. How to mount semiconductor chips.