JP2002331386A - Solder and soldered wiring substrate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide solder containing only an extremely little Pb, low in a melting point, excellent in wettability, and excellent in mechanical properties, and provide a soldered wiring substrate using the soldering not exerting a bad influence on the environment, and excellent in reliability for long term connection. SOLUTION: The solder contains Sn as a main component, besides Ag and Cu, and contain an extremely little amount of Pb, in particular, 1-3 wt.% Ag, 0.3-1 wt.% Cu and 0.3-2.0 wt.% Pb.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder used for mounting components on a wiring board constituting an electronic device or the like.

[0002]

2. Description of the Related Art In recent years, the problem of global environmental protection has been closed up, and interest in the environment has been increasing on a global scale. In the field of the electronics industry, the problem of Pb (lead) contained in solder mainly used as a bonding material for component mounting has attracted much attention.

[0003] Most of electronic devices are disposed of when they are no longer needed, and the Pb eluted from the solder on the wiring board of these discarded electronic devices due to chronic acid rain in recent years.
Is causing water pollution. However, a technique for removing Pb from the discarded wiring board solder has not been established yet. For this reason, development of a technique capable of reducing the amount of Pb contained in the solder material has been awaited.

On the other hand, when an electronic component is joined to a wiring board, it is necessary to provide a solder having an appropriate melting point that does not cause thermal damage to the electronic component and that ensures the heat resistance of the wiring board. Furthermore, it is necessary to ensure the wettability with the material constituting the land that will be the joint of the wiring board.

[0005] From such a viewpoint, Sn not containing Pb is used.
-Ag-based solder, Sn-Bi-based solder, and the like have attracted attention. For example, Japanese Patent No. 3027441 discloses Sn-Ag-
An example of a Cu-based solder, and an example of a Sn-Ag-Cu-Bi-based solder are disclosed in U.S. Pat. No. 4,879,096.

[0006]

However, in the case of Sn-Ag solder containing no Pb, the peak temperature at the time of soldering exceeds at least 230 ° C., and it is difficult to produce a solder having the proper melting point. Further, when Cu is contained, although the effect of lowering the melting point is obtained, the improvement of the wettability is not sufficient. Further, when Bi is contained, the melting point is reduced and the wettability is improved. However, when Bi is contained excessively, elongation, which is an important factor in mechanical properties of solder, particularly resistance to strain generated by thermal cycling and the like, is improved. The aperture characteristics are significantly reduced. Furthermore, when Pb is contained in the electrode of the electronic component to be soldered, the solder constituent material and Pb are alloyed to lower the melting point, impairing the heat resistance of the joint and shortening the service life. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a reduced Pb content and a low melting point.
An object of the present invention is to provide a solder having excellent wettability and excellent mechanical properties. It is another object of the present invention to provide a wiring board that is soldered using this solder and that suppresses adverse effects on the environment and has high reliability at the joints.

[0008]

The solder of the first configuration according to the present invention contains Sn as a main component, and contains about 1 to 3% by weight of Ag, about 0.3 to 1% by weight of Cu, .3-2.
About 0% by weight of Pb.

[0009] The solder of the second configuration according to the present invention is the solder of the second configuration, and has an A content of about 2.5% by weight.
g, about 0.5% by weight of Cu, and about 1.0% by weight of Pb.

[0010] The wiring board of the first configuration according to the present invention comprises:
It is soldered using the solder of the first or second configuration.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Sn-1.5Ag-0.5Cu-1.0P according to Embodiment 1 of the present invention
b and Sn- containing no Pb as Comparative Example 1.
1.5Ag-0.5Cu solder and JISZ2
After machining according to the 2014 test piece, each test piece was subjected to a tensile test at room temperature (25 ° C.) and a tensile speed of 5 mm / min. As a result, as shown in Table 1,
The values equivalent to those of Comparative Example 1 containing no Pb were obtained in both tensile strength, elongation, and drawing, and no decrease in mechanical properties due to the contained Pb was observed.

[0012]

[Table 1]

Further, each of the above-mentioned solders was placed in a table-top type flow soldering test tank at a pitch of 1.27 mm.
200mm x 200m with multiple electrode connectors inserted
The bridge generation rate was measured using a Cu-sulfur / pre-flux substrate made of FR-4 material having a thickness of mx 1.6 mm (total number of electrodes: 1800). The solder bath temperature was set at 250 ° C., and the conveyor speed was 0.9 m / min. Note that a standard RMA type flux was used. As a result, the rate of occurrence of bridges was 4.7% in Comparative Example 1, but was reduced to 0.7% in the solder of the present embodiment.

Embodiment 2 FIG. The Sn-3.0Ag-0.5Cu-1.0Pb solder according to the second embodiment of the present invention and, as Comparative Example 2, Sn-3.0Ag containing no Pb.
-0.5Cu solder was prepared and machined according to JISZ22014 test pieces, and each test piece was subjected to a tensile test at room temperature (25 ° C.) and a tensile speed of 5 mm / min. As a result, as shown in Table 2, the same values as those of Comparative Example 2 containing no Pb were obtained in both tensile strength, elongation, and drawing, and no decrease in mechanical properties due to the inclusion of Pb was observed.

[0015]

[Table 2]

Further, each of the above-mentioned solders was placed in a table-top type flow soldering test tank at a pitch of 1.27 mm.
200mm x 200m with multiple electrode connectors inserted
The bridge generation rate was measured using a Cu-sulfur / pre-flux substrate made of FR-4 material having a thickness of mx 1.6 mm (total number of electrodes: 1800). The solder bath temperature was set at 250 ° C., and the conveyor speed was 0.9 m / min. Note that a standard RMA type flux was used. As a result, in comparison with Comparative Example 2, the bridge generation rate was 4.5%, whereas the solder of the present embodiment was reduced to 0.6%.

Further, from Tables 1 and 2, the solder according to this embodiment and the solder according to Embodiment 1 are as follows.
It can be seen that the mechanical characteristics and the rate of occurrence of bridges are equivalent. The melting point obtained from the liquidus temperature described in the present embodiment and the first embodiment is the same as that in the present embodiment (218 ° C.).
However, compared to the first embodiment (223 ° C.), the temperature can be reduced by about 5 ° C., and the thermal effect on the electronic component can be reduced. Also, the workability of soldering is improved.

Embodiment 3 Sn-2.5Ag-0.5Cu-1.0Pb solder according to Embodiment 3 of the present invention and Sn-2.5Ag containing no Pb as Comparative Example 3.
-0.5Cu solder was prepared and machined according to JISZ22014 test pieces, and each test piece was subjected to a tensile test at room temperature (25 ° C.) at a tensile speed of 5 mm / min. As a result, as shown in Table 3, the tensile strength,
In both elongation and drawing, values equivalent to those of Comparative Example 3 containing no Pb were obtained, and no decrease in mechanical properties due to the inclusion of Pb was observed.

[0019]

[Table 3]

Further, each of the above-mentioned solders was placed in a table-top type flow soldering experiment tank at a pitch of 1.27 mm.
200mm x 200m with multiple electrode connectors inserted
The bridge generation rate was measured using a Cu-sulfur / preflux substrate made of FR-4 material having a thickness of mx 1.6 mm (total number of electrodes: 1800). The solder bath temperature was set at 250 ° C., and the conveyor speed was 0.9 m / min. Note that a standard RMA type flux was used. As a result, the bridge generation rate in Comparative Example 3 was 4.3%, while the solder according to the present embodiment could be reduced to 0.4%.

The solder according to the present embodiment has the same solder melting point and the same bridge generation rate as the solder according to the second embodiment, but has the mechanical characteristics,
Since the elongation is increased by about 3% and the drawing is increased by about 4%, the thermal fatigue resistance is improved.

Embodiment 4 In order to investigate the effect of the Pb content on the thermal fatigue properties, Sn-2.5Ag-
Three types of solder in which the content of Pb was changed in the range of 0 to 2% by weight in 0.5Cu (Pb content: S1; 0, S2; 1.0,
S3; 2.0% by weight), individually placed in a desktop type flow soldering test tank, and a jumper wire 1 having a wire diameter of 0.5 mmφ and a surface layer of about 10 μm plated with Sn-10Pb was prepared. , As shown in FIG.
The single-sided wiring Cu / pre-flux wiring board 2 made of FR-4 material having a thickness of 0 mm × 70 mm × 1.6 mm was inserted into the wiring board 2, and the jumper wire 1 and the land 3 of the wiring board 2 were soldered by flow soldering.

For comparison, a conventional Sn-37Pb (Sn-Pb eutectic) solder was similarly evaluated. The hole diameter of the wiring board used in the test was 0.9 mm, and the land diameter was 1.3 mm. Solder bath temperature is 2
The temperature was set at 50 ° C., and the conveyor speed was 0.9 m / min. The flux used was a standard RMA type.

After the sample wiring board is manufactured, the temperature is set at -40 ° C. (30 ° C.).
2) and 125 ° C. (30 minutes), and the opposite side of the soldered jumper wire 1 as shown in FIG. 2
With the wiring board 2 soldered only on one side as shown in FIG.
At a pulling speed of 20 mm / min.
And the land 3 were measured for bonding strength.

FIG. 3 shows the relationship between the maximum value of the pull-out strength of the jumper wire 1 after the heat cycle test thus obtained and the number of cycles. All the solders were equivalent to the Sn-Pb eutectic solder. Therefore, when the amount of Pb added to the Sn-2.5Ag-0.5Cu solder is in the range of up to 2.0% by weight, the long-term connection reliability of the solder joint can be assured as before.

Embodiment 5 In order to investigate the influence on the elongation due to the content of Pb, Sn-2.5Ag-0.5C
5 types of solder in which the content of Pb was changed in the range of 0 to 2% by weight of u (Pb content: S4; 0, S5; 0.5, S6;
1.0, S7; 2.0, S8; 3.0% by weight), and were machined according to JISZ22014 test pieces, and then each test piece was subjected to a tensile test. For comparison, Sn-37Pb (Sn-Pb eutectic) solder was similarly evaluated. The test was performed at room temperature (25 ° C.) at a tensile speed of 5 mm / min.

Further, each of the above-mentioned solders was placed in a table-type flow soldering test tank at a pitch of 1.27 mm.
200mm x 200m with multiple electrode connectors inserted
A bridge generation rate was measured using a Cu-sulfur / pre-flux wiring board made of FR-4 material having a thickness of mx 1.6 mm (total number of electrodes: 1800). The solder bath temperature was set at 250 ° C., and the conveyor speed was 0.9 m / min. Note that a standard RMA type flux was used.

FIG. 4 shows the relationship between the elongation obtained in the tensile test, the bridge occurrence rate obtained in the above measurement, and the solder composition. From this, it can be seen that the bridge generation rate mainly due to insufficient wettability is significantly reduced when the Pb content is 0.5% by weight or more. On the other hand, it can be seen that the elongation showing the mechanical properties sharply decreases in the range where the Pb content exceeds 2.0% by weight. In particular, Sn-2.5Ag-0.5Cu-1.
0Pb has a low rate of occurrence of bridges, can secure drawing characteristics, and is excellent in wettability and mechanical characteristics.

Embodiment 6 FIG. Similarly to Embodiments 1 to 5, Ag 1 to 3%, Cu 0.3 to 1%, Pb 0.
Various solders were prepared in the range of 3 to 2.0%, and the liquidus temperature (solder melting point) was measured in the same manner. As a result, the liquidus temperature was in the range of 214 to 226 ° C. It was confirmed that the temperature was within a practical temperature range where no damage was caused and the heat resistance of the wiring board could be secured.

[0030]

As described above, according to the present invention, the composition of the solder is approximately 1 to 3% by weight of Sn containing Sn as a main component.
g, about 0.3 to 1% by weight of Cu, and 0.3 to 2.0% by weight.
Since Pb is contained in an amount of about% by weight, it is possible to provide a solder having a low adverse effect on the environment, a low melting point, excellent wettability, and excellent mechanical properties.

The solder is composed of Sn as a main component and about 2.5% by weight of Ag and about 0.5% by weight of C
Since u and about 1.0% by weight of Pb are included, the rate of occurrence of bridges is particularly low, and good elongation characteristics and drawing characteristics can be secured.

Further, since the electronic components and the like are soldered to the wiring board using the above-mentioned solder, there is an effect that the long-term connection reliability of the solder joint can be ensured. In particular, even when Pb is contained in the electrode of the wiring board, lowering of the melting point can be prevented, and heat resistance can be ensured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a wiring board for measuring solder joint strength according to a fourth embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a solder joint strength measuring method according to a fourth embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between lead pull-out strength and the number of heat cycles according to Embodiment 4 of the present invention.

FIG. 4 is a diagram showing a relationship between a bridge generation rate and elongation and a solder composition according to a fifth embodiment of the present invention.

[Explanation of symbols]

1 jumper wire, 2 wiring board, 3 land, 6 solder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukinobu Sakagami 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Kohei Murakami 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd. F-term (reference) 5E319 AB01 AC01 BB01 BB08 CC24 CD28 GG03

Claims (3)

[Claims] 1. An alloy containing Sn as a main component and containing about 1 to 3% by weight of Ag, about 0.3 to 1% by weight of Cu, and about 0.3 to 2.
A solder containing about 0% by weight of Pb. 2. The solder according to claim 1, comprising about 2.5% by weight of Ag, about 0.5% by weight of Cu, and about 1.0% by weight of Pb. 3. A wiring board characterized by being soldered using the solder according to claim 1 or 2.