JPH1116916A - Forming method of bump electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce bonding failure rate even if a pad electrode is substituted for Au electrode and improve working efficiency, by raising the pad electrode temperature up to a specific temperature for edge bonding. SOLUTION: A wire W mainly composing either one element out of Pb, Sn, In is wedge-bonded on a pad electrode 2 on a substrate 1 using a wedge bonder to form wedge bumps 3 by cutting off the wire W. At this time, a glass epoxy substrate is used as the substrate 1 for Au plating on a Cu wiring to form pad electrodes 2. Besides, the substrate 1 is heated upward by a heater 8 for specifying the temperature to be 70-150 deg.C. Through these procedures, a solder wire favorable in cost is used as for the bump electrode forming material while Au electrode in excellent corrosion resistance is used as for the pad electrode for settling the discrepancies such as bonding or wedge clogging, etc., in the case of forming the bump electrode by wedge bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a bump electrode on an electronic component, and more particularly to a method for forming a bump electrode useful for mounting a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as a method for connecting an electrode of a semiconductor element or a semiconductor device to a substrate electrode, a wire connection method and a bump connection method are known. Wire connection method
In this method, the tip of a wire is first bonded on an electrode such as a semiconductor element, the wire is wired in a loop, and then the second bonding is performed on an electrode such as a substrate. This connection method is a method that can be mass-produced by a bonding device. However, the work of connecting the electrodes one by one requires a lot of man-hours, and the wires are wired in a loop. And there is a drawback that there is a limit to high-density mounting.

On the other hand, the bump connection method is a so-called wireless connection method in which an electrode of a semiconductor element or the like and an electrode of a substrate or the like are connected by a metal projection (bump electrode). Pad electrodes are arranged in an area array on the semiconductor element. Although the above-mentioned drawbacks in the wire connection method can be solved because they can be arranged, it cannot be said that there are no following problems. That is, as a conventional bump electrode forming method, for example, as shown in FIG. 8 of JP-A-2-237119, a barrier metal is formed on a substrate by a vapor deposition method, then a resist is formed, and then a resist is formed on the substrate electrode. There is known a method in which a bump electrode is formed by a plating method, and a bump electrode is completed by removing a resist and etching an unnecessary portion of a barrier metal. According to this method, a large-scale bump manufacturing facility is newly required, and there is a problem that a manufacturing process is complicated. Therefore, a technique capable of forming a bump electrode more easily has been desired.

As a means for responding to such a demand, there is known a method of forming a bump electrode in which a metal ball is held by a ball holder and joined to the upper surface of the electrode, as disclosed in, for example, JP-A-8-236527. However, in the forming method, it is difficult to manufacture a metal ball having a small diameter variation, and it is troublesome to select a metal ball having a predetermined diameter, so that there is a practical limit in cost. Further, as disclosed in Japanese Patent Application Laid-Open No. Sho 60-134444, a method of forming a bump by ball bonding using a ball formed by heating and melting the tip of a wire is conventionally known. , 200-25
Since it is necessary to heat the substrate at 0 ° C., there is a possibility that the substrate may be damaged when a resin binder substrate is used, and there is a problem that the material of the substrate to be used is limited.

On the other hand, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-237119, the tip of a wire is pressed and joined to an electrode with a wedge-shaped tool, and then the wire is cut from the pressed tip to form a metal. By forming bumps (wedge bumps), the above-mentioned problems caused by metal balls and ball bonding can be solved, and bump electrodes having excellent shapes can be formed by a simple method. Are known. JP-A-2-237119 discloses the use of an Al wire, an Au wire, and a Pb-Sn eutectic solder wire as a material for forming a bump electrode by wedge bonding.

[0006]

However, the method of forming a bump electrode by wedge bonding will be discussed in more detail.
When a wire, an Au wire, or the like is used, the melting point is too high with respect to the substrate, and particularly, Au is expensive. Therefore, although the use of a Pb-Sn eutectic solder wire has been considered, in the case of mounting an electronic component such as a semiconductor device which requires high reliability, when an Au electrode having excellent corrosion resistance is used, a wedge bond is required. There is a problem that non-delivery frequently occurs. If wedge bond non-adhesion occurs, reworking bonding is required, resulting in a problem that work efficiency is reduced.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to reduce a bond non-bonding rate even when a bump is formed on a Au electrode by wedge bonding using a solder wire. An object of the present invention is to provide a method for forming a bump electrode by wedge bonding.

[0008]

According to a first aspect of the present invention, there is provided a bump electrode forming method comprising the steps of: forming a bump electrode on a pad electrode formed on a substrate wiring;
In a bump electrode forming method in which wedge bonding is performed using a wire containing any one of b, Sn, and In as a main component and the wire is cut at a neck portion, the pad electrode temperature is increased from 70 ° C. to 150 ° C. In the following, wedge bonding is performed by controlling heating.

Preferably, the pad electrode is made of Au or an Au alloy. The wedge bonding preferably applies ultrasonic waves, and the ultrasonic wave application time is preferably 1 to 30 msec.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments. The material for forming a bump electrode used in the present invention needs to have an alloy composition containing any one of Pb, Sn, and In as a main component. Here, the main component refers to a component which is the largest in components constituting the alloy. Of these, the main component is preferably at least 50%, more preferably at least 60%.

As a specific composition system, Pb, S
n or In as one of the main components, Fe, Ni,
A composition system containing at least one of Ag at 1 to 10% by weight can be mentioned.

[0012] As a method for producing the above-mentioned material, an ingot is usually extruded and drawn, but the tensile strength can be increased by drawing and manufacturing an element wire obtained by a liquid quenching method. .

The shape of the above-mentioned material may be any of a wire shape and a tape shape, but is preferably a wire shape in consideration of productivity. Considering the size required for the bump electrode, the diameter of the wire is preferably 0.03 to 1.0 mm.

In the present invention, the copper clad laminate for a printed circuit is generally called a substrate. Examples thereof include a resin binder substrate, a ceramic substrate, and a lead frame. In this context, the resin binder substrate refers to a copper-clad laminate for a printed circuit in which a resin is mainly used as a binder for a base material. Examples thereof include a paper-phenol copper-clad laminate, a paper-epoxy copper-clad laminate, a glass-epoxy copper-clad laminate, and a glass-BT epoxy copper-clad laminate. In the present invention, among these substrates, the glass / epoxy copper-clad laminate and the glass / BT epoxy copper-clad laminate are preferably used.

In the present invention, the pad electrode on the substrate is
Refers to a buffer electrode formed on the wiring. Figure 2 for an example
In FIG. 1B, reference numeral 11 in the figure denotes a substrate, on which wirings (circuits) not shown are formed, and pad electrodes 12 are formed at a plurality of predetermined positions on the wirings. The pad electrode 12 is formed by forming a Ni base as necessary, and then forming an alloy pad electrode containing any one of Au, Ag, Cu, Sn, and Pb as a main component, such as a Pb-Sn alloy pad or a Cu pad. Is formed as Among these, it is preferable to use any one of Ag, Pb, and Sn as a main component because the bonding property of the wedge bump by wedge bonding is improved. Also, considering corrosion resistance, A
It is preferable to use u. The plating method is used to form the pad electrode.

Au, Ag, Pt, Pd as pad electrodes
When any one of Pb and Sn is used as a main component, and a coating containing any one of Pb and Sn as a main component is formed on the surface thereof, the bonding property of the wedge bump by wedge bonding is improved. Is preferred.

In the bump electrode forming method according to the present invention, any of the above electrode materials may be used. In particular, when Au having excellent corrosion resistance is used as the electrode material, a highly reliable semiconductor device is manufactured. It is particularly effective and preferably used.

Hereinafter, a method for forming a bump electrode will be described in detail. In the bump electrode forming method according to the present invention, a bump electrode is formed on a pad electrode on a substrate by wedge bonding. At this time, the pad electrode temperature is 7
It is necessary to perform heating so as to exceed 0 ° C. and 150 ° C. or less. When Au is used as the pad electrode material, the non-adhesion rate increases when the pad electrode temperature is 70 ° C. or lower. If the temperature exceeds 150 ° C., the clogging of the wire into the wedge tool becomes remarkable.

FIG. 1 shows an example in which the substrate 1 is placed on a heating device 8 and the pad electrode 2 is heated to the above-mentioned temperature to perform wedge bonding. (A) As shown in the figure, the tip of the wire W is pressed against the pad electrode 2 with a wedge-shaped tool T, and preferably, ultrasonic waves are applied to join. The output of the ultrasonic wave is 0.2 to 2.0 W, and the application time is 0.8 to 40.
It is preferably 0 msec. More preferably,
With an applied output of 0.2 to 2.0 W and an applied time of 1.0 to 30.0
msec, most preferably, applied power of 0.3 to 1.6 W
And the application time is 1.0 to 30.0 msec. Next, as shown in FIG. 2 (b), after slightly raising the tool T obliquely upward, a notch is formed at the boundary (neck portion) between the tip end joined to the pad electrode 2 and the wire W using a cutter C. After that, the wire W is raised together with the tool T, and the tip end and the wire W are cut at the notch portion to form the wedge bumps 3. Alternatively, the tip is joined to the pad electrode 2 and then the tool T is slightly raised obliquely upward, and then the tool T is lowered again to remove the wire W
And in this state, a notch is formed in the boundary (neck) using a cutter C. Thereafter, the wire W is raised together with the tool T, and the tip and the wire W are cut at the notch. May be formed. When the wire W to be used has a diameter of 0.3 mm or less, the cutter C
Without using the wire, the wire W can be cut by pulling the wire W in a state where the tip is pressed.

Here, the wedge bump refers to a bump in a state where a material for forming a bump electrode is wedge bonded and cut from the material.

As described above, a material for forming a bump electrode (wire in the above example) is bonded by wedge bonding, and the material is cut at a neck portion to form a wedge bump. Then, the wedge bump is heated at 70 to 250 ° C. The heating method is preferably used in order to improve the bonding property between the pad electrode and the bump electrode. A more preferred heating temperature is 100 to 200 ° C. When performing the main heating, A
An r, N2 atmosphere is preferred. The main heating is not particularly necessary when the bondability between the pad electrode and the bump electrode is sufficiently obtained, but is effectively used when further improvement in the bondability is required.

After the wedge bump is formed as described above, heating is performed to form the wedge bump into a ball shape to form a ball bump. When performing this heating, Ar, N
Two atmospheres are preferred. The heating temperature varies depending on the composition of the material for forming the bump electrode.
It is preferred to heat at ° C.

Next, an example of mounting an electronic component such as a semiconductor device having a wedge bump formed thereon will be described with reference to FIG. FIG. 2A shows a state in which the pad electrode 12 is heated via the substrate 11 by the heating device 18 having a built-in heater 19, and the wedge bump 13 is formed by the procedure of FIG. (B) The figure shows the wedge bump 13
Is heated to form a ball bump 13 '.
Further, as shown in FIG.
The semiconductor device 14 is mounted on the substrate 11 by bonding the pad electrode 15 of the semiconductor device 14 to the pad electrode 12 of the substrate 11 through the above. Finally, the semiconductor element 14 is sealed with a sealing resin 16 as shown in FIG.
7 is completed.

As described above, the bump electrode used in the present invention is a semiconductor device having a semiconductor element mounted on a substrate,
It is suitable for use as an electronic component such as a hybrid IC in which the mounted component is further mounted on a substrate.

[0025]

EXAMPLES Examples of the method of the present invention employing the above-described various conditions will be described below. (Example 1) Predetermined amounts of Sn and Ag were added to Pb, melted in a melting furnace, and then cast to form 60% by weight Sn and 2% by weight A.
g, a 100 mm diameter ingot having a composition consisting of the balance Pb was obtained, extruded to a diameter of 2 mm, and drawn to a diameter of 0.1 mm by wire drawing.
mm wire. As shown in FIG. 1A, the wire was wedge-bonded to a pad electrode on a substrate using a wedge bonder, and the wire was cut to form a wedge bump. Using a glass / epoxy substrate as the substrate, a Cu electrode was plated with Au to form a pad electrode. Further, the substrate was heated from below to set the pad electrode temperature to 90 ° C. Wedge bonding has a load of 120 g,
The test was performed under the conditions of an output of 0.2 W and an output time of 5 msec. Until the clogging of the wedge tool occurred, bump formation by wedge bonding was performed up to 10,000 times, and the number of unbonded bonds by microscopic observation with respect to the number of times of bonding was defined as the bond nonbonding ratio, and the test was performed together with the number of bonds before the wedge clogging. The test results showed that the bond failure rate was 10%, and no clogging of the wedge tool occurred up to 10,000 times. Tables 1 and 2 show the test conditions and test results. In Table 2, as the number of bonds up to the wedge clogging, those which did not cause clogging even after 10,000 times of wedge bonding were indicated as 10,000 or more.

(Examples 2 to 17 / Comparative Examples 1 and 2) Table 1 shows the substrate material, wedge bonding load, output and output time as ultrasonic conditions, and pad electrode temperature as test conditions.
A wire was manufactured and a wedge bump was formed in the same manner as in Example 1 except for the following. Tables 1 and 2 show these test conditions, the bond non-adhesion rate and the number of bonds up to wedge bond clogging as test results.

[0027]

[Table 1]

[0028]

[Table 2]

From the above measurement results, when bumps are formed by wedge bonding on a pad electrode using a solder wire, it is necessary to reduce the pad non-adhesion rate and to increase the number of bonds up to clogging of the wedge bond. It has been confirmed that it is useful to perform wedge bonding by heating the electrode temperature to more than 70 ° C. and 150 ° C. or less. That is, in Examples 1 to 17 according to the present invention, the pad electrode temperature was heated to more than 70 ° C. and 150 ° C. or less,
Comparative Examples 1 and 2 where the temperature is 70 ° C. or less or exceeds 150 ° C.
From the comparison with the above, it was confirmed that advantageous effects on the object of the present invention can be obtained.

Further, from the comparison between the embodiment 7 and the other embodiments, the application output is 0.2 to 2.0 W and the application time is 1.0 to 3
A more favorable effect is obtained at 0.0 msec. Further, from the comparison between Example 1 and the other examples, the applied output is 0.3 to 1.6 W and the application time is 1.0 to 30.0 msec.
It was confirmed that the most favorable effect was obtained at the time.

When Examples 1 and 7 are compared with Comparative Example 2, Comparative Example 2 can obtain more favorable results in terms of the bond non-adhesion rate. Is 200 times, which is not suitable for practical use.

[0032]

As described above, according to the present invention, any one of Pb, Sn, and In is formed on a pad electrode on a substrate wiring.
In a bump electrode forming method in which wedge bonding is performed using a wire containing a seed as a main component and the wire is cut at a neck portion, the pad electrode temperature is increased from 70 ° C. to 150 ° C.
By performing the wedge bonding by heating below, even if an Au electrode is used as the pad electrode, the bond non-adhesion rate can be reduced and the work efficiency can be improved.
Therefore, while a solder wire, which is advantageous in terms of cost, is used as a material for forming a bump electrode, an Au electrode having excellent corrosion resistance is used as a pad electrode, and when a bump electrode is formed by wedge bonding, non-bonding or clogging of the wedge may occur. As a method of forming a bump electrode which can solve the above problem and make the advantages of the bump connection method capable of high-density mounting more effective, it can be suitably used for assembling electronic components and semiconductor devices.

When the pad electrode is made of Au or an Au alloy, the pad electrode has high corrosion resistance and the like, and can be suitably used for assembling highly reliable electronic components and semiconductor devices. Further, it is particularly preferable that the wedge bonding is performed by applying an ultrasonic wave, and the application time of the ultrasonic wave is 1 to 30 msec in order to reduce the bond non-bonding rate, and the above-described effect is more effective. It can be.

[Brief description of the drawings]

FIG. 1 is a simplified diagram showing an example of an embodiment of a bump electrode forming method according to the present invention.

FIG. 2 is a simplified diagram showing an example of a mode in which a semiconductor device is mounted on a substrate using bump electrodes formed in the present invention.

[Explanation of symbols]

 1, 11: Substrate 2, 12: Pad electrode on substrate 3, 13: Wedge bump 8, 18: Heating device 14: Semiconductor element 17: Semiconductor device T: Wedge-shaped tool W: Wire

Claims (4)

[Claims] 1. A wedge-bonding method using a wire containing any one of Pb, Sn, and In as a main component on a pad electrode formed on a substrate wiring, and cutting the wire at a neck portion. In the electrode forming method, the pad electrode is heated to a temperature of more than 70 ° C. and 150 ° C. or less to perform wedge bonding. 2. The method according to claim 1, wherein the pad electrode is made of Au or an Au alloy. 3. The bump electrode forming method according to claim 1, wherein said wedge bonding applies an ultrasonic wave. 4. The application time of the ultrasonic wave is 1 to 30 msec.
4. The method for forming a bump electrode according to claim 3, wherein c.