JP2000208533A - Die bonding zn alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bonding Zn alloy, which has no problems with respect to wire die bonding and junction reliability, and is preferred for use in assembling electronic components, etc., and does not contain Pb. SOLUTION: This Zn alloy contains Ge of 2 to 9 wt.%, Al of 2 to 9 wt.%, and further Mg of 0.01 to 0.5 wt.% as necessary, and the rest comprises Zn and inevitable impurities. Alternatively, this Zn alloy contains one or more kinds of Sn and In of 5 to 25 wt.%, and further Ge of 0.1 to 7 wt.% as necessary, and the rest comprises Zn and inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die bonding Zn alloy used for die bonding of semiconductor devices.

[0002]

2. Description of the Related Art Solder is used for die bonding of power transistor elements and the like. Solders for this purpose include:
1) The element can be joined at a temperature of about 350 ° C. 2) The solder does not melt even at a temperature of about 250 ° C. so that the wire bonding in the next step is performed normally. 3) Use of the element In such a case, it is necessary to have characteristics such as not deteriorating the bonding property. Conventionally, a Pb-based solder represented by Pb-5% Sn has been used.

In recent years, there has been an increasing movement to restrict the use of Pb in consideration of environmental pollution. In response to such a movement, there has been a demand for Pb-free solders in the field of die bonding solders for semiconductor devices.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method for producing Pb, which is suitable for use in die bonding of a semiconductor device.
It is an object of the present invention to provide a solder alloy containing no.

[0005]

In order to achieve the above object, a Zn alloy for die bonding according to the present invention comprises (1)
Ge is contained in an amount of 2 to 9% by weight, and Al is contained in an amount of 2 to 9% by weight.
(2) Ge is contained in an amount of 2 to 9% by weight, and Al is contained in an amount of 2 to 9% by weight.
9% by weight, and further contains 0.01 to 0.5% by weight of Mg, with the balance being Zn and unavoidable impurities. (3) 5 to 25% by weight of at least one of Sn and In. (4) containing 5 to 25% by weight of at least one of Sn and In, further containing 0.1 to 7% by weight of Ge, and the balance of Zn and unavoidable impurities. It is characterized by being composed of unavoidable impurities.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the configuration of the present invention will be described below.

The alloys of the first and second inventions have a melting point of 4
This is based on Zn at 20 ° C., the wettability of which is improved by adding Ge, and the die bonding temperature is lowered by adding Al.

The reason why the concentration of Ge is set to 2 to 9% by weight is that if the concentration is less than the lower limit concentration, the wettability is insufficiently improved and the probability of occurrence of bonding failure during die bonding increases.
Conversely, if the concentration exceeds the upper limit, the alloy hardness becomes too high, and chip cracks occur in an environmental resistance test such as a heat cycle test.

On the other hand, the reason why the concentration of Al is set to 2 to 9% by weight is that if the concentration is less than the lower limit, the effect of lowering the die bonding temperature is insufficient. This is because not only saturation is caused, but also wettability is reduced, resulting in poor bonding at the time of die bonding.

[0010] Mg in the second invention is an element that functions to improve the corrosion resistance of the alloy and thereby improve the reliability of bonding during use of the device. Mg concentration of 0.0
The reason for setting the content to 1 to 0.5% by weight is that if the concentration is less than the lower limit concentration, the effect of addition is insufficient. Because it becomes.

The alloys according to the third and fourth inventions have a melting point of 4
The die bonding temperature is lowered by adding Sn or / and In to Zn at 20 ° C. Sn and In also have a function of improving the wettability of the alloy and a function of reducing the hardness of the alloy to improve the reliability of element bonding.

When Sn or / and In is added, Sn
Alternatively, a liquid phase is formed at a temperature of about 200 ° C. or about 145 ° C., which is the eutectic temperature of In and Zn, but we assume that the concentration of Sn or / and In is within the composition range of the present invention. It was found that the amount of liquid phase generated at around 250 ° C. was suppressed to a very small amount, and no problem was caused in an electronic component assembling process such as wire bonding.

[0013] The reason why the concentration of Sn or / and / or In is set to 5 to 25% by weight is that if the concentration is less than the lower limit concentration, the effect of lowering the die bonding temperature is insufficient and the alloy hardness is too high and the heat cycle is too high. This is because the probability of chip cracking increases in an environmental resistance test such as a test. Conversely, when the concentration exceeds the upper limit concentration, the amount of liquid phase generated at a temperature of about 250 ° C. becomes too large, and in a process such as wire bonding. This is because inconvenience occurs.

Ge in the fourth invention has the function of improving the wettability of the alloy and slightly lowering the die bonding temperature. The reason for setting the concentration of Ge to 0.1 to 7% by weight is that if the concentration is less than the lower limit concentration, the effect of addition is insufficient. This is because the probability of occurrence of chip cracks in the environmental resistance test increases.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the first and second inventions: A Zn alloy having a composition shown in Tables 1 and 2 is melted in an atmosphere using Zn, Ge, Al, and Mg each having a purity of 99.9% by weight. Was melted. The obtained ingot was subjected to a heat treatment at 250 ° C. and cold-rolled to obtain a 0.1 mm thick sample.

As to the evaluation of the obtained sample, as to the die bonding property, whether a 3 mm square Au vapor-deposited dummy chip can be bonded to the Ag plating L / F using a solder die bonder (EDB-200, manufactured by Dage). or not,
When bonding was possible, the lowest die bonding temperature at which bonding was possible was determined.

Whether or not wire bonding, which is the next assembly step, is performed normally (wire bonding property) is determined by using a commercially available gold wire and a ball bonder (manufactured by KAIJO, FB).
−118), and a wire bonding test was performed between the vapor-deposited Al surface on the chip and the Ag-plated surface on the L / F on which die bonding was performed in the same manner as described above.

The wire bonding test was conducted at a stage temperature of 250 ° C.
The case where the wires were not joined was evaluated as “poor”.

To evaluate the bonding reliability, after performing die bonding, an epoxy resin (manufactured by Sumitomo Bakelite;
-65 ° C./15
After performing a temperature cycle test of 0 ° C. 1000 cycles or a constant temperature and humidity test of holding at a temperature of 80 ° C. and a humidity of 80% for 1000 hours, the resin is opened, and the chip bonding portion is observed.
A case where no crack occurred at the chip or the joint interface was evaluated as “good”, and a case where cracks occurred was evaluated as “poor”.

Tables 1 and 2 show the results of the above evaluation. "Defective" in the column of the minimum die bonding temperature in Table 1 means that a sample in which bonding could not be obtained occurred.
Further, "-" in the wire bonding property and the bonding reliability means that the test was not performed.

As is clear from Tables 1 and 2, the Zn alloys according to the first and second aspects of the present invention can be die-bonded at a temperature of about 350 ° C. and have a good wire-die bonding property and bonding reliability. It turns out that there is no problem.

[0022]

[Table 1]

[0023]

[Table 2]

Third and Fourth Embodiments: Zn alloys having the compositions shown in Tables 3 and 4 were prepared using Zn, Sn, In, and Ge having a purity of 99.9% by weight in an atmosphere melting furnace. It was melted. The obtained ingot was subjected to a heat treatment at 120 ° C. and cold-rolled to obtain a sample having a thickness of 0.1 mm.

The obtained samples were evaluated for die bonding property, wire bonding property, and bonding reliability in the same manner as in the previous period. Tables 3 and 4 show the results.

As apparent from Tables 3 and 4, the Zn alloys according to the third and fourth aspects of the present invention can be die-bonded at a temperature of about 350 ° C., and have problems in wire-die bonding property and bonding reliability. It turns out that there is no.

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

As is apparent from the above, according to the present invention, a Pb-free solder alloy suitable for use in assembling electronic parts and the like can be provided.

Claims (4)

[Claims] 1. A Zn alloy for die bonding, comprising 2 to 9% by weight of Ge, 2 to 9% by weight of Al, and the balance of Zn and unavoidable impurities. 2. A composition containing 2 to 9% by weight of Ge and 2 to 9% of Al.
A Zn alloy for die bonding, wherein the Zn alloy contains 0.01% to 0.5% by weight of Mg, and the balance consists of Zn and unavoidable impurities. 3. An amount of at least one of Sn and In of 5 to 25% by weight.
A Zn alloy for die bonding, characterized in that the balance comprises Zn and inevitable impurities. 4. An amount of at least one of Sn and In of 5 to 25% by weight.
And 0.1 to 7% by weight of Ge, with the balance being Zn
And a Zn alloy for die bonding, comprising an unavoidable impurity.