JPH0845940A - Solder wire and solder bump electrode - Google Patents

Abstract

(57) [Abstract] [Purpose] When reflowing solder bumps on an Al electrode of an IC chip, the process of forming a film on the Al electrode is omitted in a separate step, and the reflow process is performed at 350 ° C. (EN) Provided is a solder bump electrode with little deterioration in strength. [Constitution] Cu (0.01 to 5.0% by weight), Ni (0.
01 to 5.0% by weight), 2 or more kinds selected from Zn (0.01 to 5.0% by weight), and 0.001 to 1.0% by weight Ti, with the balance being Sn or Pb-Sn. The solder bump 3 was formed on the Al electrode 2 of the IC chip 1 by using the solder wire, and the IC chip 1 and the electrodes 2 and 5 of the substrate 4 were bonded via the solder bump 3. At this time, the solder bump 3 is subjected to a reflow treatment at 350 ° C. to correct the positional deviation between the electrodes 2 and 5 and prevent a defective joint between the IC chip 1 and the substrate 4. Even if the solder bump 3 was subjected to the reflow treatment, the deterioration of the shear strength could be suppressed to a low level, and the practical shear strength could be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder bump electrode for an IC chip and a solder wire used for the same, and more particularly to a solder bump electrode for connecting an IC chip to a substrate by a wireless bonding method via a bump, and a solder wire used therefor. Regarding

[0002]

2. Description of the Related Art In recent years, as IC chips have become more sophisticated, LS
The number of I / O terminals tends to increase. Therefore, IC
As a method for connecting a chip and a substrate, a wireless bonding method using bumps such as flip chip bonding has attracted attention. This method is suitable for the method of increasing the number of electrode pads and increasing the mounting density because the electrode bonding can be formed only on the periphery of the IC chip in the wire bonding method, while the electrode pads can be formed on the entire surface. .

Here, flip chip bonding will be described as a typical example of a wireless bonding method via bumps. In this method, as shown in FIG. 1, solder bumps 3 are formed on the Al electrodes 2 of the IC chip 1 and predetermined electrodes 5 are formed on the substrate 4 at corresponding positions. The IC chip 1 and the substrate 4 are bonded to each other via the electrodes 2 and 5 and the solder bumps 3, respectively. At this time, as shown in FIG. 2, since it is difficult to mount the IC chip 1 at a predetermined position on the substrate 4 with high accuracy, the positions of the electrodes 2 and 5 may be displaced.
In this way, with the positions of the center lines of the electrodes 2 and 5 displaced, the IC
When the chip 1 and the substrate 4 are bonded, a bonding failure occurs, which causes a malfunction of the semiconductor.

In order to deal with this, Japanese Patent Laid-Open No. 6-132353 proposes to reflow solder bumps to improve the bonding accuracy. This is because the electrode positions of the IC chip and the substrate are slightly displaced. Even if the solder bumps interposed between the two electrodes are reflowed, the self-correction is performed so that the surface area of the solder bumps in the molten state is minimized by the surface tension, and the displacement of the IC chip can be eliminated. is there. This method is effective as a method for eliminating the deviation in mounting the IC chip, but when the solder bump material on the IC chip Al electrode is reflowed, there arises a problem that the bonding strength between the IC chip and the solder bump is lowered.

In order to cope with the decrease in the bonding strength, Cr, Cu, Au or Ti, Ni, Au is formed on the IC chip Al electrode.
It has been attempted to form a multilayer sputtered film such as
However, this method has a problem that the number of steps increases, time is required, and the cost becomes high, and it is necessary to suppress the reflow treatment temperature to a low level and prevent the bonding strength from decreasing. Here, in the method of melting other connection materials in the order of higher melting point in the reflow treatment step, and finally reflowing the solder bump material at a low temperature to prevent the joint strength from decreasing, the number of steps also increases and There is a problem that not only the cost is increased but also the cost is increased. Therefore, by preventing the decrease in the bonding strength even after performing the reflow treatment at 350 ° C. without forming the multi-layer sputtered film, which was conventionally subjected to the reflow treatment at 227 ° C. after forming the multilayer sputtered film, Simultaneous melting of other connecting materials has been considered.

[0006]

In view of the above-mentioned conventional circumstances, the present invention omits the step of forming a film on the Al electrode as a separate step when reflowing the solder bumps on the Al electrode of the IC chip. It is intended to provide a solder wire and a bump electrode whose bonding strength is less deteriorated even if reflow treatment is performed at a temperature of ℃.

[0007]

In order to achieve the above object, the first invention of the present application is the solder wire for bump electrode of IC chip, characterized in that the composition of the solder material is the following [composition I]. Is. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn.

A second invention of the present application is a solder wire for a bump electrode of an IC chip, wherein the composition of the solder material is the following [composition II]. [Composition II] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
0 wt% Ti, 1.0-10.0 wt% Sb, 0.2-
Contains 10.0 wt% Ag, balance Sn or Pb-S
n.

In the third invention of the present application, the composition of the solder material is the following [composition I], and the composition is 350 ° C. on the Al electrode of the IC chip.
The solder wire for a solder bump electrode of an IC chip is characterized by having a shear strength of 19 MPa or more after being reflowed. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn.

Further, in the fourth invention of the present application, in the solder bump electrode formed on the IC chip Al electrode, the composition of the solder material is the following [composition I], and Cu, at the boundary between the IC chip Al electrode and the solder bump, 2 selected from Ni and Zn
A solder bump electrode for an IC chip, characterized in that an intermetallic compound containing at least one species and Ti is formed. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn.

[0011]

The structure and operation of the present invention will be further described below. First, the solder material is P
A b-Sn alloy is used as a base alloy. Here, Sn in the solder material
The lower limit of the content is 2% by weight. The upper limit is preferably about 98% by weight. If the Sn content is less than 2% by weight, there is a drawback that the surface oxidation of the solder is so severe that it cannot be put to practical use. The upper limit of the Sn content is about 98% by weight, which is an amount capable of containing an effective additive element.

The solder material of the present invention is 0.001 to
It contains 1.0 wt% Ti, and further contains Cu (0.01 to
5.0% by weight), Ni (0.01 to 5.0% by weight), Z
It is necessary to contain two or more kinds selected from n (0.01 to 5.0% by weight). The alloy solder obtained by adding Ti, Cu, Ni, and Zn to the Pb-Sn alloy in this way does not require sputter film coating treatment on the Al electrode.
Even when reflowed at 50 ° C., the shear strength of the solder bump material is less deteriorated and can be 19 MPa or more. Further, the shear strength retention rate based on the shear strength after reflow at 227 ° C. without coating treatment can be 90% or more.

The contents of Ti, Cu, Ni and Zn are Ti
(0.005 to 0.5% by weight), Cu (0.05 to 5.
0% by weight), Ni (0.05 to 5.0% by weight), Zn
It is preferably (0.05 to 5.0% by weight). At this time, without coating the sputtered film on the Al electrode, 3
Even when the reflow is performed at 50 ° C., the deterioration of the shear strength of the solder bump material is further small, and the shear strength maintenance ratio can be 100%.

Here, when the Ti content is less than 0.001% by weight, when the reflow is performed at 350 ° C. without the sputter film coating treatment, the shear strength can be maintained at 19 MPa or more, but the shear strength maintenance ratio is about 50. %. T
If the i content exceeds 5.0% by weight, there is a drawback that Ti is oxidized and the ball is eccentric when the ball is formed by arc discharge. When at least two kinds of Cu, Ni and Zn are not contained in the required amount, the shear strength is 19 M when reflowed at 350 ° C. without the sputter film coating treatment.
Does not reach Pa. If the content of at least two kinds of Cu, Ni and Zn exceeds 5.0% by weight respectively, there is a drawback that the wire is significantly hardened and the wire drawing process is hindered. Therefore, the contents of Ti, Cu, Ni and Zn are Ti (0.001 to 1.0% by weight) and Cu (0.0
1 to 5.0% by weight), Ni (0.01 to 5.0% by weight), and Zn (0.01 to 5.0% by weight).

Further, in the present invention, in addition to the above-mentioned constitution of the solder material, it is possible to include components usually contained as the solder material. Examples include 0.2 to 10 wt% Ag for improving cold workability, and 1 to 10 wt% Sb for improving the strength of the solder material and facilitating handling.

The reason why the solder material of the present invention has the above-described structure can sufficiently reduce the deterioration of the shear strength of the solder bump material even if the solder material is reflowed at 350 ° C. without performing the sputter film coating treatment on the Al electrode. Although it has not been clarified, when the solder bump material is reflowed on the Al electrode at 350 ° C., conventionally, the Al component is diffused in the solder bump material and the Al electrode tends to disappear.
In the present invention, as shown in FIG. 3, an intermetallic compound 6 is formed at the boundary between the Al electrode 2 and the solder bump material 3a, and at least two kinds of Cu, Ni and Zn and Ti are contained in the compound 6. It is considered that the inclusion of Al functions to prevent the Al component from diffusing into the solder bump material even when reflowed on the Al electrode at 350 ° C.

Next, a method of manufacturing the solder wire will be described. The following two methods can be exemplified as the method for manufacturing the solder wire according to the present invention. In the first method, the solder material having the above-mentioned structure is melted, and casting, extrusion, and wire drawing are performed to finish a wire having a diameter of 30 to 100 μm. The second method is to melt the solder material having the above-mentioned structure, obtain a wire by a rapid solidification method in which the molten metal is injected into water, and then perform wire drawing to finish a wire having a diameter of 30 to 100 μm. In the present invention, the second method, the rapid solidification method, is preferably adopted. The reason is that a uniform composition can be obtained, good mechanical properties can be obtained, and the handling of bump formation becomes easy.

The method of forming the solder bumps and the joining of the IC chip and the substrate will be described below with reference to FIG. Formation of Solder Ball In FIG. 1A, the solder wire 7 is led out of its tip from the capillary 8 and the solder ball 10 is formed using the torch 9 as a heating source. Solder ball crimping (b) In the figure, the solder ball 10 is crimped onto the Al electrode 2 on the IC chip 1 by lowering the capillary 8. Here, an Al alloy such as Al-Si or Al-Cu-Si is usually used as the Al electrode. Formation of Solder Bumps In FIG. 1C, the capillary 8 is pulled up, the neck portion of the solder ball 10 is broken, and the solder ball 1
0 remains on the Al electrode 2. The remaining solder balls 10 are called solder bumps 3. Bonding of IC Chip 1 and Substrate 4 In the diagram (d), the IC chip 1 and the substrate 4 are bonded to each other via electrodes 2 and 5 and solder bumps 3. At this time, as described above, so-called reflow treatment is performed to heat the solder bump material until it reaches a molten state. By performing this reflow process, it is possible to self-correct the bonding failure due to the positional displacement of the electrodes 2 and 5 of the IC chip 1 and the substrate 4 by utilizing the surface tension of the melted solder bump material.

[0019]

EXAMPLES Examples will be described below. [Example 1] 50 wt% Sn, 0.001 wt% Ti,
0.5 wt% Cu, 0.5 wt% Ni, 5.0 wt% S
b, 5.0 wt% Ag, and the balance Pb, 100 g of the solder alloy was melted in an argon gas atmosphere, and was jetted from a quartz nozzle with a hole diameter of 300 μm at an argon gas pressure of 25 g.
A solder wire was obtained by rapid solidification in a cylindrical drum formed with a water layer rotating at 0 rpm. This wire was drawn to form a solder wire with a diameter of 50 μm. Using the solder wire obtained here, the solder bump 3 was formed on the Al—Si alloy electrode 2 of the IC chip 1 according to the procedure of FIGS. 20 solder bump samples were prepared according to the same procedure as in FIGS. 4 (a) to 4 (c), and 10 solder bump samples were coated with rosin-based flux (trade name: α5003TR) manufactured by Japan Alpha Metals Co., Ltd. Then, the solder bumps were reflowed by heating at 227 ° C. and 350 ° C. using a heating table in an argon gas atmosphere. Shear strength was measured for each of 10 solder bump materials subjected to two types of reflow treatment. The results are shown in Table 2. Then, the intermetallic compound 6 shown in FIG. 3 was measured using an X-ray diffraction apparatus. Table 2 shows the types of confirmed Ti, Cu, Ni and Zn components.

[Method of Measuring Shear Strength] Solder bump material and I
The shear load between the C-chip Al electrodes was measured using a bonding strength tester, and the shear strength (MPa) per joint area measured by an optical microscope was displayed.

[Examples 2 to 26, Comparative Examples 1 to 9] Tests were conducted in the same manner as in Example 1 except that the composition of the solder wire was as shown in Table 1. The measurement results are shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

As is clear from Examples 1 to 26 in Tables 1 and 2, the Sn content in the solder material is about 10 to 98% by weight, which is a Pb-Sn alloy or an Sn-based alloy, and 0 0.001-1.0 wt% Ti, 0.01-
5.0 wt% Cu, 0.01 to 5.0 wt% Ni, 0.
By forming a solder bump using a solder wire containing two or more of 01 to 5.0 weight Zn, the shear strength can be obtained even if the reflow treatment is performed at 350 ° C. without performing the sputter film coating treatment on the Al electrode. Is 19 MPa or more, and the shear strength maintenance ratio based on the shear strength after reflow treatment at 227 ° C. which is the conventional reflow treatment temperature is 9
It can be seen that it is 0% or more.

Here, 0.005 to 0.5% by weight of Ti is used.
Cu, N to be included and to be added in addition to two or more kinds
When 0.05 to 5.0% by weight of each of i and Zn is contained, a more excellent effect is exhibited, and the shear strength is 30 MPa or more even if direct reflow treatment is performed at 350 ° C., and the shear strength retention rate is 100%. It turns out that this is the end.

On the other hand, although the Pb-Sn alloy is used as the base alloy, 0.001 to 1.0 wt% Ti, or 0.01 to 5.0 wt% Cu, 0.01 to 5.0 wt% % Ni and 0.01 to 5.0% by weight of Zn are not contained, as is clear from Comparative Examples 1 to 9, even if the reflow treatment is performed at 350 ° C., the shear strength is none. 25 MPa or less, and the shear strength maintenance rate is 45 in each case.
It turns out that it is less than or equal to%.

[0027]

As described above, according to the present invention, the composition of the solder wire used for forming the solder bump is set to the above-mentioned structure, so that the solder bump material on the IC chip Al electrode is not subjected to the sputtered film coating process. Even if the reflow treatment was performed at ℃, the deterioration of the shear strength could be suppressed to a low level, and the practical shear strength could be obtained. Therefore, it is necessary to form the film on the Al electrode in a separate step, and to form the bump electrode and the semiconductor device in comparison with the conventional one in which another connection material needs to be melted and a reflow process needs to be performed in a separate step. The number of manufacturing steps is reduced, time is not required, and cost can be reduced.

[Brief description of drawings]

FIG. 1 is a simplified diagram showing an outline of a flip chip bonding method.

FIG. 2 is a simplified diagram showing a case where an IC chip is displaced in a flip chip bonding method.

FIG. 3 is a simplified diagram showing an embodiment of a solder bump electrode according to the present invention, showing a state after reflow processing.

FIG. 4 is a simplified diagram showing an outline of a method of forming solder bumps and joining of an IC chip and a substrate.

[Explanation of symbols]

 1: IC chip 2: Al electrode 3: Solder bump 4: Substrate 5: Electrode 6: Intermetallic compound

Claims (4)

[Claims] 1. A solder wire for an IC chip bump electrode, wherein the composition of the solder material is the following [composition I]. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn. 2. A solder wire for an IC chip bump electrode, wherein the composition of the solder material is the following [composition II]. [Composition II] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
0 wt% Ti, 1.0-10.0 wt% Sb, 0.2-
Contains 10.0 wt% Ag, balance Sn or Pb-S
n. 3. A solder for an IC chip bump electrode, wherein the composition of the solder material is the following [Composition I], and the shear strength after reflowing at 350 ° C. on the IC chip Al electrode is 19 MPa or more. Wire. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn. 4. In a solder bump electrode formed on an IC chip Al electrode, the composition of the solder material is the following [composition I].
And an intermetallic compound containing Ti and two or more kinds selected from Cu, Ni and Zn is formed at the boundary between the IC chip Al electrode and the solder bump.
C chip solder bump electrode. [Composition I] Cu (0.01 to 5.0% by weight), Ni
(0.01 to 5.0% by weight), Zn (0.01 to 5.0)
2% or more, and 0.001-1.
It contains 0 wt% Ti and the balance is Sn or Pb-Sn.