JP3308060B2 - Semiconductor device mounting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a semiconductor device,
The present invention relates to a method for mounting a flip-chip IC mounted face-down.

[0002]

2. Description of the Related Art Conventionally, as a face-down mounting method of a flip-chip IC, a solder bump formed on the surface of a connection electrode of a semiconductor chip is directly pressed into contact with a connection electrode of a wiring board under a temperature condition lower than its melting point. There is known a method in which a bump is plastically deformed and joined to a connection electrode of a wiring board.

[0003]

However, in the above mounting method, the bonding strength of the solder bump is inferior to that of the molten solder (solder reflow) method. Was. The present invention has been made in view of the above problems, and an object of the present invention is to provide a bump bonding type semiconductor chip mounting method which does not require a step of re-melting bumps and can significantly improve productivity compared to the related art. And

[0004]

According to a method of mounting a semiconductor chip of the present invention, a solder bump formed on a surface of a connection electrode of a semiconductor chip is pressed against a connection electrode of a wiring board under a temperature condition lower than its melting point. In a semiconductor device mounting method in which a solder bump is plastically deformed and alloy-bonded to a connection electrode of the wiring board, the solder bump has a deformation speed of 10 μm.
/ Sec or less.

[0005] In a preferred embodiment, the deformation speed of the solder bump is 1 to 3 µm / sec or less. In a preferred embodiment, the ratio of Sn to Pb of the solder bump is 30
To 70 to 30 parts by weight. In a preferred embodiment, the solder bump is a eutectic solder containing 61 to 65 wt% of Sn.

In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportionality constant is k, the strain rate dependence index is m, σ
= K × ε _t ^m, and the above-described pressure welding is performed in a range where the strain rate dependence index m is 0.3 or more.

[0007]

The method of mounting a semiconductor chip according to the first invention is characterized in that the deformation speed of the solder bump is set to 10 μm / sec or less. In this way, it has been found that good joining strength can be obtained without adding a solder melting step.

[0008] In a preferred embodiment, the deformation speed of the solder bump is 1 to 3 µm / sec or less. In this way, it has been found that a joining strength almost equal to that can be obtained without adding a solder melting step. In a preferred embodiment, the ratio of Sn to Pb of the solder bump is 30 to 70 parts by weight to 70 to 30 parts by weight.

According to experiments, solder in this composition range is:
Since the strain rate dependence index m described later is 0.3 or more,
It was found that good joint strength was obtained as with the eutectic solder. In a preferred embodiment, the solder bump has an Sn of 6
The eutectic solder contains 1 to 65 wt%.

According to experiments, the solder in this composition range is:
Since the strain rate dependence index m described later is 0.3 or more,
It was found that good joint strength was obtained as with the eutectic solder. In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportionality constant is k, the strain rate dependence index is m, and σ = k
× ε _t ^m , the strain rate dependent index m is equal to 0.
The pressure welding is performed in three or more ranges.

In order to explain the meaning, in order to bring the bonding strength of the solder bump closer to the melting (alloy) level, it is necessary to realize good bonding not on a part of the bonding surface but on the entire surface. Σ = k between the strain rate ε _t and the deformation resistance σ
A relationship of × ε _t ^m holds, and m is larger than a normal metal in a superplastic material such as solder. The fact that m is large means the following. That is, since the deformation resistance σ of the portion where the strain rate ε _t is large due to the locally large external force is large, this portion is hardly deformed.
Since the deformation resistance σ of a portion where the strain rate ε _t is small due to a locally small external force is small, this portion is easily deformed. That is, the small external force application part is easily deformed, and the large external force application part is hardly deformed.

If this is different from the above, if the small external force application site and the large external force application site are easily deformed in the same manner, the strain rate ε _{t of the} site where the locally large external force is applied is obtained.
Is large, the deformation amount of this part is large, and the strain rate ε _{t of the} part where a small external force is locally applied is small, so the deformation amount of this part is small, and as a result, the part where the large external force is applied is concentrated It deforms, and the amount of deformation at the small external force application site becomes insufficient, and the bonding strength at that site in the case of solder bumps becomes insufficient. In particular, since the solder bump has a hemispherical shape and a shape to which an external force is not uniformly applied, it is difficult to satisfactorily deform the entire bonding surface if m is small.

According to the experimental results, it has been found that, when the strain rate dependence index m is 0.3 or more, the bonding strength of the solder bump is comparable to that of the molten solder.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The device of this embodiment is a COG (Chi) in which a semiconductor chip is mounted on a glass substrate (liquid crystal display device).
FIG. 1 shows a state in which an IC chip 2 is directly bonded to a glass substrate 1, FIG. 2 shows a main part of the IC chip 2 after bonding, and FIG. 3 shows a main part of the IC chip 2 before bonding.

An aluminum electrode 3 is formed on the surface of the IC chip 2 as a chip-side connection electrode, and the surface is covered with a passivation layer 4. Further, a part of the aluminum electrode 3 is exposed, and a barrier metal 5 made of chromium or titanium is formed on the aluminum electrode 3 in this exposed portion. Copper bumps 6 are arranged on the barrier metal 5, and solder 7 is arranged on the surface of the copper bumps 6.
As the solder 7, Pb-63Sn (eutectic solder)
Is used, and the melting point of this solder is 183 ° C. In the manufacturing process, after the barrier metal 5 is deposited, continuous plating of copper and solder is performed, and the electrode tip is made hemispherical by reflowing at 250 ° C. in an inert atmosphere .

Glass substrate (wiring substrate) before bonding
1 is shown in FIG. 4 (plan view). A conductive pattern 10 is formed on the glass substrate 1 as a chip-side connection terminal. The conductive pattern 10 has a three-layer structure in which an ITO (indium tin oxide) layer 11, a nickel layer 12, and a gold layer 13 are sequentially laminated on soda glass. This laminated structure is formed by depositing and plating ITO / Ni / Au. Here, the gold layer 13 on the surface is an antioxidant for the ITO layer 11 and the nickel layer 12 as the wiring base material.

At the time of bonding, the glass substrate 1 is placed at a predetermined position, and the IC chip 2 is
Is transported above the glass substrate 1 and alignment is performed. Then, the IC chip 2 is placed on the glass substrate 1. Then, a necessary load per bump is applied from the back surface (the upper surface in FIGS. 1 and 2) of the IC chip 2 by a dangsten (W) heating head, and the temperature of the heating head is set to 120.
Keep at １７175 ° C. and hold for 10-30 seconds. That is, at a temperature lower than the melting point of 183 ° C. of the solder 7, the IC chip 2 and the glass substrate 1 are pressurized and joined while plastically deforming the solder 7.

At this time, since the heating temperature is equal to or lower than the melting point of the solder 7, the solder 7 is not melted but is soft, and the joint is deformed and comes into surface contact. In addition, when the solder 7 is joined while being plastically deformed by applying the pressure, the surface of the solder 7 is advanced, and fresh solder is exposed to form a joining interface. Then, Au in the conductive pattern 10 is used.
(Gold) is almost diffused into the solder 7 near the joint,
It is found that nickel also diffuses a little into the Sn particles at the interface.
It was confirmed by cross-sectional analysis by the DX analysis method.

Further, by adjusting the pressing force by the heating head according to the number of terminals and the size of the terminals, the connection area and the shape of the solder bumps can be easily adjusted. It should be noted that the local heating may be performed by irradiating a laser to the bump portion without using the heating head. Here, the above-mentioned joining conditions will be described in detail.

The heating time (10 to 30 seconds) is a time sufficient for conducting heat from the heating head to the substrate side and an upper limit time for securing productivity. FIG. 5 shows a change in the bonding strength when the deformation speed (μm / sec) of the solder bump 7 is variously changed. However, the diameter of the solder bump 7 is about 250 μm and its thickness (after deformation)
Is a maximum of about 40 μm, and the thickness of the copper bump 6 is a maximum of about 30 μm.
μm.

As a bonding apparatus, a flip chip mounter (model name: flip chip mounter (special order product)) manufactured by Miss FA Corporation was used, and 44 solder bumps 7 were simultaneously bonded. The deformation speed of the solder bump 7 is flip-chip.
Can be considered equal to the descent speed of the top mounter
Therefore, the deformation speed was controlled by controlling the descending speed of the flip chip mounter, and the test was performed 40 times at each deformation speed. As can be seen from FIG. 5, the average deformation speed is 10 μm
At a strain rate of 10 -1 (1 / sec) in terms of strain rate εt, the bonding strength per bump electrode 7 is 80 g weight and 3 μm.
The bonding strength per one bump electrode 7 at 85 m (3 × 10 -1 (1 / sec) in terms of strain rate εt) is 85 g.
At 1 μm (strain rate εt conversion × 10 −2 (1 / sec)), a bonding strength of 7 g per 7 bump electrodes was obtained.

Next, the same test was carried out by changing the composition of Sn and Pb of the solder bump 7 in the range of 30 to 70 parts by weight to 70 to 30 parts by weight. As a result, almost the same characteristics as those in FIG. 5 were obtained. That is, when the average deformation speed is 10 μm or less, a significantly better bonding strength can be obtained as compared with the conventional deformation speed (30 to 50 μm / s). Bonding strength almost comparable to solder was achieved. In particular, if the solder bump is made of eutectic solder containing 61 to 65 wt% of Sn,
Since the strain rate dependent index m described later becomes large, good joining strength was obtained.

Next, the strain rate ε _t of the above eutectic solder
And the relationship between the deformation resistance σ. FIG. 6 shows the result. For the test, a tensile tester (model name: servo pulser (special order product)) manufactured by Shimadzu Corporation was used, and the cross-sectional area of the plate-shaped test product was 20 mm ² . The strain rate ε _t is determined by the empirical formula σ =
It was determined by kε _t ^m , and σ when ε _t was changed was measured.

As can be seen from FIG. 6, the strain rate ε _t is 1
Up to × 10 ⁻¹ (1 / sec), the strain rate dependent index m is 0.3 or more, and this is a region where the deformation resistance σ increases as the strain rate ε _t increases. Can be uniformly deformed even if it differs in each part. And even if the solder shows superplasticity, the strain rate ε _t is 3 (1/1 /
sec) or more, especially 6 (1 / sec) or more, the deformation resistance σ does not increase in spite of the increase in the strain rate ε _t , and only this part is locally deformed, and the entire area is plastically deformed. It can be presumed that the bonding strength is reduced due to this.

Although the conductive pattern 10 (wiring material) is Au / Ni / ITO in the above embodiment, Au, Ni, S
n, Ag, Ag-Pd, Ag-Pt, Cu, etc. may be used as long as they are soldered, and Pb-63S
A solder having a composition other than n may be used. In short, any low melting metal containing at least tin may be used. Further, although the solder 7 is provided on the copper bumps 6 (protruding electrodes) in the above embodiment, it is not necessary to particularly provide the protruding electrodes, and a method of supplying solder balls between the chip 2 and the substrate 1 may be used. The gold layer 13 can be omitted. Instead of the nickel layer 12, a metal that can be alloyed with the solder bump 7 can be employed.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a bonding portion (terminal portion) of the present embodiment.

FIG. 2 is a diagram showing a state after bonding.

FIG. 3 is a diagram showing a terminal portion of an IC chip before bonding.

FIG. 4 is a diagram showing a terminal portion of a glass substrate before bonding.

FIG. 5 is a diagram showing a measurement result of a relationship between a deformation speed and a bonding strength.

FIG. 6 is a diagram showing a measurement result of a relationship between a strain rate and a deformation resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate (wiring board) 2 Semiconductor chip 3 Aluminum electrode (semiconductor chip connection electrode) 7 Solder bump 10 Conductive pattern (wiring board connection electrode)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-136216 (JP, A) JP-A-63-152136 (JP, A) JP-A-61-80828 (JP, A) JP-A-60-1985 53039 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/60 311

Claims (5)

(57) [Claims] 1. A solder bump formed on a surface of a connection electrode of a semiconductor chip is pressed against a connection electrode of a wiring board under a temperature condition lower than its melting point, and the solder bump is plastically deformed to be in contact with the connection electrode of the wiring board. A method for mounting a semiconductor device to be alloy-joined, wherein a deformation speed of the solder bump is set to 10 μm / sec or less. 2. The deformation speed of the solder bump is 1 to 3 μm.
Implementation of semi <br/> conductor device according to claim 1, characterized in that the / sec or less. 3. The solder bump according to claim 1, wherein the ratio of Sn to Pb is 30 to 70 parts by weight to 70 to 30 parts by weight.
A mounting method of the semiconductor device described in the above. 4. The solder bump has a Sn content of 61 to 65 wt.
% Claim 1, characterized in that are KyoAkirasei solder containing
A mounting method of the semiconductor device described in the above . 5. A strain observed rate epsilon _t, the deformation resistance sigma, the proportionality constant k, and the strain rate dependence exponent m, and σ = k × ε _t ^m, and the strain rate dependence exponent m is 0.3 or more 2. The method for mounting a semiconductor device according to claim 1, wherein the pressing is performed within a certain range.