JP3142912B2 - Solder material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder material, and more particularly to a Pb-Sn solder material used for soldering an Au-coated electrode portion such as a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor chip is connected to a substrate by a semiconductor device connection, more specifically, a wireless bonding method, in particular, a flip chip bonding method or a tape carrier bonding method, as shown in FIG. A Pb-Sn solder bump 3 is provided by pressing on a base metal 2 formed of a Ti layer, a Ni layer, and an Au layer (FIG. 1A), and is subjected to a reflow treatment at a predetermined temperature in a flux. The Ni layer of the substrate 4 is welded and connected to the bumps 3 (FIG. 1B).

The Au layer of the base metal 2 has a high concentration and is necessary for preventing the Ni layer from being oxidized. However, since the bump 3 which is a solder material is bonded to the Au layer, the solder layer in the bonding interface region is formed. Au elutes into the material and Au-S
There has been a problem in that the reliability of the semiconductor device is impaired, for example, the precipitation of the n-compounds, embrittlement and reduction in fatigue life.

In order to solve the problem, conventionally, 200
The thickness of the Au layer of about 300 nm (nanometer) is
Improvements have been made to reduce the film thickness to about the same level (the Au concentration in the bonding interface region is about 0.3 wt%). Since no distribution was obtained, a thick portion of the Au film was formed, and as a result, failure of the device could not be prevented.

In view of the above-mentioned circumstances, the present invention provides a Pb-Sn-based solder material which prevents embrittlement due to joining between an Au layer of an Au-coated electrode portion and a solder material and improves fatigue life. The purpose is to provide.

[0006]

The solder material of the present invention is characterized in that 0.0001 to 0.5 wt% of P or 0.0001 to 1.0 wt% of Sb is added to Pb-Sn solder. .

[0007]

According to the present invention, when P (phosphorus) or Sb (antimony) is added to Pb-Sn solder, when the solder material is bonded to the Au layer, it is deposited in the solder material. Thus, the crystal grains of the Au-Sn compound are refined and a uniform dispersion state is obtained, so that embrittlement accompanying precipitation of the Au-Sn compound can be prevented.

The above P and Sb are added in an amount of 0.00
If the content is less than 01 wt%, the above-mentioned effects cannot be obtained, and the amount of P added is
If the amount exceeds 0.5 wt%, and if the added amount of Sb exceeds 1.0 wt%, the solder material itself becomes hard and brittle, and the bonding strength and fatigue life decrease. Therefore, the addition amounts of P and Sb are set to 0.0001 to 0.5 wt% for P and 0.0001 to 1.0 wt% for Sb.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pb-2Sn solder (containing 2 wt% Sn) and Pb-5Sn solder (containing 5 wt% Sn) from among Pb-Sn based solder materials (containing 2 to 5 wt% Sn) which are generally used. Containing), and set P to 0 to 0.
Samples of Nos. 1 to 21 shown in the table were prepared by adding a predetermined amount of 6 wt% and Sb in a range of 0 to 2.0 wt%.

Using each sample, FIG. 1 (A)
As described in (B), the bump 3 is made of Au of the base metal 2.
After forming on the layer, the Ni layer of the substrate 4 was welded on the bump 3, and the number of thermal cycles was measured for each sample to check the fatigue strength (life).

Each of the above-mentioned samples is prepared by thinning a solder material having the respective composition into a thin wire by a rapid solidification method. The tip of the wire of each of the samples is heated to form a ball. The bump 3 was formed by cutting the sample wire while pulling it on the Au layer 2 by pulling. Also, Au of the base metal 2
The thickness of the layer is set to about 330 nm (the Au concentration in the bonding interface region is about 1 wt%), which is slightly larger than the conventional general film thickness of 200 to 300 nm in order to make the effect of Au remarkable.

For the measurement of the number of heat cycles, each sample was measured as shown in FIG.
In the assembled state shown in (B), at room temperature, 5 minutes → -55 ° C, 3
One cycle was defined as 0 minutes → room temperature · 5 minutes → −150 ° C. · 30 minutes, and the number of cycles at which the electric resistance reached 10Ω per bump was measured. The measurement results are as shown in the table.

[Table 1]

[0013] In this technical field, the number of thermal cycles is around 1000 cycles as a criterion. Therefore, considering the table, the addition of P (samples 2 to 6, 14 to 17 ), The lower limit was 0.0001 wt%, and the upper limit was 0.5 wt%.
Regarding the addition of Sb, see (Samples 7 to 12, 18 to 2
1) It was confirmed that 0.0001 wt% was the lower limit and 1.0 wt% was the upper limit. In addition, the upper limit of the above P and Sn
Although the thermal cycle is about 1000 cycles even when the amount slightly exceeds 0.5 wt% and 1.0 wt%, the number of thermal cycles tends to decrease at the above upper limit, and the effect according to the increase cannot be obtained. In consideration of this, the upper limit was set.

In the above embodiment, the solder material for connection of the semiconductor device has been described, but it is easily understood that the use is not limited. Also, the case where the base metal 2 formed on the chip 1 is a multilayer film composed of a Ti layer, a Ni layer, and an Au layer has been described.
The same effect can be obtained with a multilayer film including a Au layer and an Au layer.
Furthermore, although the case where the above-mentioned solder material is manufactured in a thin wire shape by the rapid solidification method has been described, the present invention is not limited thereto, and a general manufacturing method may be freely used.

[0015]

According to the present invention, by adding P or Sb, when a solder material is joined to a layer having a high Au concentration, embrittlement due to precipitation of an Au-Sn compound in the solder material is prevented. As a result, the fatigue life can be improved, and the reliability of a product using this solder material can be improved.

Further, there are no disadvantages of the prior art for thinning the thickness of the Au layer, and there are secondary effects such as easy film forming means.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of use of a solder material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Base metal 3 Solder bump 4 Substrate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 35/26 C22C 11/00-11/10

Claims (1)

(57) [Claims] In a solder material for soldering an electrode portion provided with an Au coating, a Pb-based solder containing 2 to 5 wt% of Sn contains 0.0001 to 0.5 wt% of P or 0.0001 to 1.
A solder material to which 0 wt% of Sb has been added.