JP3324446B2 - Mounting structure and mounting method of chip with bump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a bumped chip mounting structure and a mounting method for mounting a bumped chip on a substrate.

[0002]

2. Description of the Related Art In order to solder an electrode of a chip to an electrode of a circuit pattern on a substrate, a method of forming a bump with a metal such as copper on the electrode of the chip in advance to obtain a chip with a bump is known. Aluminum is often used as a metal for the electrodes. When soldering the chip with bumps, the bumps are mounted on the solder pre-coated on the electrodes of the substrate, and then the solder is heated and melted to solder the bumps and the electrodes.

Hereinafter, a soldering portion of a conventional bumped chip will be described with reference to the drawings. FIG. 19 is a partial sectional view of a conventional chip with a bump and a substrate. FIG.
In FIG. 1, an aluminum electrode 2 is formed on a chip 1, and a copper bump 3 is formed on the aluminum electrode 2.
The copper bump 3 is mounted on the solder 7 pre-coated on the electrode 6 of the substrate 5 and then heated to melt the solder 7. Then, the solder 7 rises along the surface of the copper bump 3 having good solder wettability by the surface tension and covers the entire surface of the copper bump 3, and the tip of the solder 7 reaches the surface of the aluminum electrode 2.

[0004]

However, when the molten solder 7 comes into contact with the surface of the aluminum electrode 2, aluminum as a material of the aluminum electrode 2 elutes into the solder from the contact portion, and the aluminum electrode 2 does not corrode. Easy to occur. When the aluminum electrode 2 is corroded, the reliability of the chip is impaired.

Accordingly, an object of the present invention is to provide a mounting structure and a mounting method of a chip with bumps in which aluminum electrodes of the chip are not corroded by solder.

[0006]

According to the first aspect of the present invention,
A copper bump is formed on an aluminum electrode of the chip by wire bonding, and the copper bump is soldered to an electrode of a substrate. The oxide film at the tip was removed, and the removed portion of the oxide film was soldered to the electrode of the substrate.

According to a second aspect of the present invention, there is provided a method of mounting a chip with bumps, the step of forming a copper bump on an aluminum electrode of the chip by wire bonding, and the step of forming an oxide film at the tip of an oxide film formed on the surface of the copper bump. And a step of soldering the removed portion of the oxide film to the electrode of the substrate.

According to a third aspect of the present invention, in the method of mounting a chip with bumps according to the second aspect, the step of removing the oxide film at the tip of the copper bump is performed by plasma etching. The oxide film is removed by etching with an electron or ion bombarding the upper surface of the bump from above.

According to a fourth aspect of the present invention, in the method of mounting a chip with bumps according to the second aspect of the present invention, the step of removing the oxide film at the tip of the copper bump comprises removing the tip of the copper bump. The portion was immersed in a flux to remove the oxide film.

According to a fifth aspect of the present invention, there is provided a method of mounting a chip with bumps according to the second aspect, wherein the step of removing the oxide film at the tip of the copper bump comprises removing the tip of the copper bump. The portion was buried in cream solder previously applied to the electrodes of the substrate, and the oxide film was removed by the flux in the cream solder.

According to a sixth aspect of the present invention, in the method of mounting a chip with a bump according to the second aspect, the step of removing the oxide film at the tip of the copper bump is performed by removing the tip of the copper bump. The part was immersed in the molten solder in the solder bath, and the molten solder and the copper bump were relatively vibrated by a vibration generator, and the oxide film was removed by the vibration.

According to a seventh aspect of the present invention, in the method of mounting a chip with bumps according to the second aspect, the step of soldering a tip of the copper bump on an electrode of a substrate is performed. The copper bumps with the solder adhered to the portions were held by holding means and pressed onto the electrodes of the substrate, and the copper bumps were vibrated by a vibration generator and soldered.

[0013]

According to the invention as set forth in the claims, of the oxide film formed on the surface of the copper bump, the oxide film at the tip is removed and the removed portion of the oxide film is soldered to the electrode of the substrate. By doing so, the solder does not adhere to the base of the copper bump on which the oxide film having poor solder wettability remains, so that the solder does not come into contact with the aluminum electrode of the chip, and therefore the corrosion of the aluminum electrode by the solder does not occur.

(Embodiment 1) FIG. 1 is a sectional view of a plasma etching apparatus according to Embodiment 1 of the present invention, and FIGS.
Is a partial sectional view of the chip with copper bumps, and FIGS. 4 and 5 are partial sectional views of the chip with copper bumps and the substrate. In FIG. 1, an electrode 12 is provided in a vacuum chamber 11 of a plasma etching apparatus, and a ground electrode 13 is provided above the electrode 12 and is connected to a ground unit 15. The electrode 12 is connected to a high frequency power supply 14.

The chip 1 is mounted on the electrode 12 with the copper bump 3 facing upward. The copper bumps 3 are formed on the aluminum electrodes 2 by wire bonding.
An oxide film 3a is formed on the surface of the copper bump 3. Although the oxide film 3a is naturally generated by the copper bump 3 coming into contact with air after wire bonding, the present invention is used as a guard means for the oxide film 3a formed on the surface of the copper bump 3 and the aluminum electrode 2. Yes, so 150 ° C
It is desirable that the oxide film 3a is positively generated in a short time by placing the copper bumps 3 in a high temperature atmosphere of a certain degree.

This plasma etching apparatus is for partially removing the oxide film 3a on the surface of the copper bump 3, and its operation will be described below. The vacuum chamber 11 is depressurized while the chip 1 is mounted on the electrode 12, and then a plasma generating gas such as argon gas is introduced into the vacuum chamber 11, and a high-frequency voltage is applied to the electrode 12 to thereby form a vacuum chamber. Plasma is generated in 11. As a result, as shown in FIG. 2, electrons and ions 16 generated by the plasma collide with the surface of the copper bump 3, and the oxide film 3 a on the surface of the copper bump 3 is removed by the etching action of the electrons and ions 16. .

FIG. 3 shows a state of the copper bump 3 after the plasma etching. Since the copper bump 3 has a substantially hemispherical shape, electrons and ions 16 are likely to collide with the tip A, and the angle of incidence at the time of collision is large, so that the etching action is large. As a result, the oxide film 3a at the tip A is removed to form a removed portion A. On the other hand, in the base portion B close to the electrode 2, the etching action is small because the incident angle of the electrons or ions 16 colliding with the surface of the oxide film 3a is small, and therefore, the oxide film 3a in this portion is not largely removed and plasma It remains after etching.

Next, as shown in FIG. 4, the chip 1 on which the removed portion A of the oxide film 3a is formed is mounted on the electrode 26 of the substrate 25 on which solder is precoated. Then the substrate 25
Is sent to a reflow furnace and heated. As a result, the solder 7 is melted, but the removed portion A from which the oxide film 3a has been removed has good solder wettability. Therefore, the molten solder 7 is applied along the surface of the copper bump 3 due to surface tension as shown in FIG. Ascends and covers the surface of the removal portion A. However, oxide film 3 with poor solder wettability
Since the solder 7 does not adhere to the base B where a remains,
The solder 7 does not contact the surface of the aluminum electrode 2, so that the aluminum electrode 2 is not corroded by the solder 7.

(Embodiment 2) FIG. 6 is a cross-sectional view of a flux application portion according to Embodiment 2 of the present invention, and FIGS. 7 and 8 are partial cross-sectional views of the chip and the substrate with copper bumps. In the first embodiment, the plasma etching is used to remove the oxide film 3a of the copper bump 3, but in the second embodiment,
In this method, the tip portion A of the copper bump 3 is immersed in a flux to remove the oxide film 3a, thereby forming a removed portion.

In FIG. 6, a chip 1 is held at the lower end of the holding head 30 by vacuum suction. The chip 1 and the copper bump 3 are the same as in the first embodiment. Reference numeral 31 denotes a flux application unit formed of a thin container, in which a flux 33 is stored. As shown in FIG. 6, the holding head 30 is lowered to
Is immersed in the flux 33. At this time, the vertical stroke of the holding head 30 is controlled so that the flux 33 is not applied to the base B of the copper bump 3. As a result, the oxide film 3a on the surface of the copper bump 3 becomes flux 33
Only the tip A immersed in is removed. At this time, the depth of the flux 33 in the flux application section 31 is
The flux 33 may be applied only to the tip A by setting the top of the copper bump 3 to contact the bottom of the flux application section 31.

Next, as shown in FIG. 7, the holding head 30 was moved, the flux 33 was applied to the tip A, and the copper bump 3 from which the oxide film 3a was removed was pre-coated with the solder 7. It is positioned on the aluminum electrode 2. Next, as shown in FIG. 8, the holding head 30 is lowered,
The copper bump 3 is mounted on the solder 7. Thereafter, the substrate 25 is sent to a reflow furnace, where it is heated and soldered. Subsequent steps are the same as in the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. 9 and 10 are partial sectional views of a chip and a substrate with copper bumps according to Embodiment 3 of the present invention. The chip 1 and the copper bumps 3 are the same as in the first embodiment, and a holding head 3 for holding the chip 1
0 is omitted. In FIG. 9, the electrode 26 of the substrate 25
A cream solder 27 is applied on the top. The cream solder 27 contains solder particles and flux components. First, the holding head 30 is moved so that the copper bumps 3 of the chip 1 held by the holding head 30 are located above the electrodes 26.
Align.

Next, as shown in FIG.
0 and lower the tip A of the copper bump 3 with the cream solder 2
7 buried. At this time, the lifting stroke of the holding head 30 is controlled so that the base B of the copper bump 3 is not buried in the cream solder 27. Next, the substrate 25 is sent to a reflow furnace in this state and heated. As a result, the oxide film 3 a at the tip end A buried in the cream solder 27 on the surface of the copper bump 3 is removed by the flux component in the cream solder 27. As a result, the copper bumps 3 are soldered to the electrodes 26 on the substrate 25 as in the first embodiment.

As described above, in the third embodiment,
By embedding the tip A of the copper bump 3 in the cream solder 27, the oxide film 3a at the tip A is removed by the flux in the cream solder 27.

(Embodiment 4) Next, Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 11 is a sectional view of a solder bath according to a fourth embodiment of the present invention, FIGS. 12 and 13 are partial sectional views of the chip with copper bumps, and FIGS. 14 and 15 are partial sectional views of the chip with copper bumps and the substrate. It is.

In FIG. 11, molten solder 37 is stored in a solder tank 40. The heater 4 is provided in the solder tank 30.
3 for maintaining the temperature of the molten solder 37 within a certain temperature range. A vibration generator 42 is provided in the solder tank 40.
The vibration is transmitted to the molten solder 37 by driving the vibration generator 42. As the type of the vibration, one having a vibration frequency in an ultrasonic range is preferably used. The holding head 30, the chip 1, and the copper bumps 3 are the same as in the first embodiment.

FIG. 12 shows a state in which the tip A of the copper bump 3 is immersed in the molten solder 37 by lowering the holding head 30. At this time, the lifting stroke of the holding head 30 is controlled so that the base B is not immersed in the molten solder 37. When the vibration generator 42 is driven in this state, the vibration is transmitted to the molten solder 37, and the molten solder 37 vibrates relatively to the copper bumps 3. The oxide film 3 a in contact with the molten solder 37 is broken by the mechanical action of the vibration and is removed from the surface of the copper bump 3. That is, only the oxide film 3a at the tip A is removed.

Next, as shown in FIG.
Increase 0. Then, the oxide film 3a is removed, and the molten solder 37 adheres in a substantially ball shape to the tip A having good solder wettability, and thereafter the molten solder 37 is solidified. At this time, the base B
The oxide film 3a remains without being removed.

After that, as shown in FIG. 14, the holding head 30 is moved, and the copper bumps 3 are positioned and mounted on the electrodes 26 of the substrate 25. Next, the substrate 25 is sent to a reflow furnace and heated. As a result, as shown in FIG.
The solder 37 is melted and the copper bump 3 is soldered to the electrode 26. At this time, since the oxide film 3a having poor solder wettability, the base B
Does not reach the molten solder 37, and the aluminum electrode 2
Never touch.

As described above, in the fourth embodiment, the tip A of the copper bump 3 is immersed in the molten solder 37 of the solder bath 40,
By vibrating the molten solder 37, only the oxide film 3a at the tip A is removed.

Embodiment 5 Next, Embodiment 5 of the present invention will be described with reference to the drawings. FIG. 16 is a sectional view of a solder bath according to the fifth embodiment of the present invention, and FIGS. 17 and 18 are partial sectional views of the chip with copper bumps and the substrate. In FIG. 26, a molten solder 37 is stored in a solder tank 40. The solder tank 40 is provided with a heater 43 to maintain the temperature of the molten solder 37 within a certain temperature range. The holding head 30, the chip 1, and the copper bumps 3 are the same as those of the fourth embodiment except that the holding head 30 is provided with a vibration generator 44.

As shown in FIG. 16, the holding head 30 holding the chip 1 is lowered to immerse the tip A of the copper bump 3 in the molten solder 37. At this time, the base B is
The elevating stroke of the holding head 30 is controlled so as not to be immersed inside. When the vibration generator 44 is driven in this state, the vibration is transmitted to the chip 1 via the holding head 30, and the copper bump 3 vibrates relatively to the molten solder 37.
As the type of the vibration, one having a vibration frequency in an ultrasonic range is preferably used. The oxide film 3 a in contact with the molten solder 37 is broken by the mechanical action of the vibration and is removed from the surface of the copper bump 3. That is, only the oxide film 3a at the tip A is removed.

Next, when the holding head 30 is raised, the oxide film 3a of the copper bump 3 is removed, and the molten solder 37 adheres in a substantially ball shape to the tip A having good solder wettability. Solidifies.

Thereafter, as shown in FIG. 17, the holding head 30 is moved to position the copper bump 3 on the electrode 26 of the substrate 25, and the holding head 30 is lowered to move the copper bump 3
The solder 37 attached to the electrode 26 lands on the electrode 26. Next, the vibration generator 44 is driven while the copper bump 3 is pressed against the electrode 26 by the holding head 30. Thereby, the contact surface between the solder 37 and the electrode 26 is joined by the vibration and the pressing force. FIG. 18 shows a state where the copper bumps 3 are soldered to the electrodes 26 in this manner. At this time, since the oxide film 3a has already been removed, there is no need to apply a flux to the upper surface of the electrode 26, and therefore, the electrode 26 is not corroded by the flux. Since the aluminum electrode 2 does not contact the solder 37, the aluminum electrode 2 is not corroded by the solder 37.

The method of joining the copper bump 3 to the electrode 26 by using vibration and pressing force by using the vibration generator 44 is not limited to the present embodiment, but can be applied to the first to fourth embodiments. .

[0036]

According to the present invention, of the oxide film formed on the surface of the copper bump, the base oxide film is left as a guard means for preventing the molten solder from creeping up to the aluminum electrode and corroding the aluminum electrode. Since only the oxide film at the tip of the copper bump is removed and the removed portion of the oxide film is soldered to the electrode of the substrate, the solder does not adhere to the surface of the oxide film having poor solder wettability. In addition, the solder does not come into contact with the aluminum electrode of the chip, so that the aluminum electrode is not corroded by the solder. In addition, if a method of relatively vibrating the molten solder and the copper bumps is used as a method of removing the oxide film, the chip can be soldered to the substrate without using a flux, so that the flux remains after the soldering. It does not corrode the electrodes of the substrate.

[Brief description of the drawings]

FIG. 1 is a sectional view of a plasma etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the chip with a copper bump according to the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of the chip with a copper bump according to the first embodiment of the present invention.

FIG. 4 is a partial sectional view of a chip and a substrate with a copper bump according to the first embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of the chip and the substrate with copper bumps according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view of a flux application section according to a second embodiment of the present invention.

FIG. 7 is a partial cross-sectional view of a chip with a copper bump and a substrate according to a second embodiment of the present invention.

FIG. 8 is a partial sectional view of a chip and a substrate with copper bumps according to a second embodiment of the present invention.

FIG. 9 is a partial cross-sectional view of a chip with a copper bump and a substrate according to a third embodiment of the present invention.

FIG. 10 is a partial cross-sectional view of a chip with a copper bump and a substrate according to a third embodiment of the present invention.

FIG. 11 is a sectional view of a solder bath according to a fourth embodiment of the present invention.

FIG. 12 is a partial sectional view of a chip with a copper bump according to a fourth embodiment of the present invention.

FIG. 13 is a partial sectional view of a chip with a copper bump according to a fourth embodiment of the present invention.

FIG. 14 is a partial sectional view of a chip and a substrate with copper bumps according to a fourth embodiment of the present invention.

FIG. 15 is a partial cross-sectional view of a chip and a substrate with copper bumps according to a fourth embodiment of the present invention.

FIG. 16 is a sectional view of a solder bath according to a fifth embodiment of the present invention.

FIG. 17 is a partial sectional view of a chip and a substrate with copper bumps according to a fifth embodiment of the present invention.

FIG. 18 is a partial sectional view of a chip and a substrate with copper bumps according to a fifth embodiment of the present invention.

FIG. 19 is a partial cross-sectional view of a conventional chip and substrate with bumps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chip 2 electrode 3 Copper bump 3a Oxide film 5, 25 Substrate 6, 26 Electrode 7, 27, 37 Solder 11 Vacuum chamber 12 High frequency electrode 30 Holding head 31 Flux application part 33 Flux 40 Solder tank 42 Vibration generator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 H01L 23/50 H05K 3/34

Claims (7)

(57) [Claims] 1. A mounting structure of a chip with bumps, wherein a copper bump is formed on an aluminum electrode of a chip by wire bonding, and the copper bump is soldered to an electrode of a substrate. A mounting structure for a chip with bumps, wherein an oxide film at a tip portion of the oxide film is removed, and the removed portion of the oxide film is soldered to an electrode of a substrate. A step of forming a copper bump on the aluminum electrode of the chip by wire bonding, a step of removing an oxide film at a tip end of an oxide film formed on a surface of the copper bump, and a step of removing the oxide film. Soldering the substrate to an electrode of a substrate. 3. The step of removing the oxide film at the tip end of the copper bump includes etching and removing the oxide film by colliding electrons or ions from above with the upper surface of the copper bump by plasma etching. The mounting method for a chip with bumps according to claim 2. 4. The bumped chip according to claim 2, wherein the step of removing the oxide film at the tip of the copper bump removes the oxide film by immersing the tip of the copper bump in a flux. Implementation method. 5. The step of removing the oxide film at the tip of the copper bump includes burying the tip of the copper bump in cream solder previously coated on an electrode of a substrate, and using the flux in the cream solder. 3. The method for mounting a chip with bumps according to claim 2, wherein 6. The step of removing the oxide film at the tip of the copper bump includes immersing the tip of the copper bump in molten solder in a solder bath and causing the molten solder and the copper bump to vibrate relatively by a vibration generator. 3. The method according to claim 2, wherein the oxide film is removed by the vibration. 7. The step of soldering the removed portion of the oxide film to the electrode of the substrate, wherein the copper bump having the solder attached to the tip is held by holding means and pressed onto the electrode of the substrate, and a vibration generator is provided. The method for mounting a chip with bumps according to claim 2, wherein the copper bumps are vibrated and soldered.