JPH1034376A - Lead-free solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-free soldering alloy specially having an excellent heat resistant fatigue characteristic and holding as much as possible such a characteristic as a Pb contained soldering alloy in spite of not containing Pb. SOLUTION: This lead-free solder is composed of, by wt., 0.1-10% Bi, 0.1-5% Ag, 0.05-2% Cu, 0.0005-0.1% Ni, 0.0005-0.01% P and the balance Sn. Also, further, by wt., 0.01-0.5%. In is added into this composition. Also, a cream solder containing the powder of the soldering alloy, a formed solder using the soldering alloy and a resin flux cored solder using the soldering alloy are included in this lead-free solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-free solder alloy containing no Pb.

[0002]

2. Description of the Related Art Conventionally, an alloy in which Pb (lead) is added to Sn (tin) or Sn + Bi (bismuth) is used as a base. Pb acts to lower the melting point of Sn of 232 ° C. in the alloy, and an alloy containing 37% by weight of Pb forms a eutectic solder having a melting point of 183 ° C., and has been widely used due to its proper melting point. . Thus, Pb was an essential component in the solder alloy composition.

[0003] However, Pb is a harmful element for humans and animals, and when the solder containing Pb is discarded, Pb components gradually melt out due to acid rain or the like and cause serious environmental pollution such as infiltration into groundwater. Is clear. In order to respond to the worldwide demand that such environmental pollution by Pb should be prevented, Pb
Research on lead-free solders containing no lead has been advanced, and many technologies have already been disclosed. In these techniques, P
In order to replace the function of b, silver (Ag), bismuth (B
i), antimony (Sb), zinc (Zn), cadmium (Cd), copper (Cu), magnesium (Mg), nickel (Ni), titanium (Ti), indium (Ti) and the like are used in combination. . However, some of these elements are toxic and extremely expensive, and they have not always sufficiently replaced the function of Pb.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is
The present invention provides a lead-free solder alloy that does not contain Pb and that retains the properties of the Pb-containing solder alloy as much as possible, and that is particularly excellent in thermal fatigue resistance.

[0005]

According to the present invention, there is provided a lead-free solder comprising:
In order to solve the above-mentioned problem, the component is Bi0.1 to 10
Wt%, Ag 0.1-5 wt%, Cu 0.055-2 wt%, Ni 0.0005-0.1 wt%, P0.0005-
0.01% by weight and the balance being Sn. Further, the present invention provides the above composition in which In 0.01 to 0.5 is added.
It relates to a solder alloy to which wt% is added. The present invention also provides
It includes cream solder containing powder of the above solder alloy, molded solder using the above solder alloy, and tinned solder using the above solder alloy.

[0006] The solder of the present invention can exhibit excellent characteristics without containing harmful Pb at all by adopting the above configuration. The characteristics of each constituent element on the solder characteristics will be described below. Sn is a main component of the solder alloy, has no toxicity per se, and has excellent properties of wetting to a joining base material, and is an essential component as a solder base material. By adding Ag to Sn,
It can improve the mechanical properties and lower the melting point. The compounding amount of Ag is 0.1 to 5% by weight, preferably 0.7 to 3% by weight in the solder alloy. 0.1% by weight
If the amount is less than 5% by weight, the effect is insufficient. If it exceeds 5% by weight, the melting temperature becomes high, and the cost is disadvantageous.

When Bi is added to Sn in which Ag is added, mechanical strength is improved and the melting temperature can be lowered. The content of Bi is 0.1 to 10% by weight, preferably 0.5 to 5% by weight. If the amount of Bi is less than 0.1% by weight, the effect is insufficient. If the amount is more than 10% by weight, the mechanical strength is improved, but the mechanical elongation is extremely reduced and thermal fatigue is likely to occur. If Cu is further added to the one obtained by adding Ag and Bi to Sn, mechanical strength and fatigue resistance can be improved. Cu in the formulation
Add 2% by weight. When the content is less than 0.05% by weight, the effect is small. When the content is more than 2% by weight, the melting temperature rises, so that it cannot be used under the conventional use conditions or the components mounted on the substrate are thermally damaged.

A feature of the present invention is that a superior effect is exhibited particularly by the combination of P and Ni. P can improve the thermal fatigue properties and mechanical properties (strength and elongation) of the solder. Moreover, these properties are significantly improved with increasing amounts of P. The compounding amount of P is 0.0005 to 0.01% by weight. If the amount is less than 0.0005% by weight, the effect is not obtained. If the amount exceeds 0.01% by weight, the mechanical strength is improved, but the surface tension of the molten solder increases,
A problem occurs in wetting in the atmosphere. Further, it has been found that by adding Ni, the thermal fatigue resistance is further improved. The effect becomes more remarkable by blending Ni with P. The amount of Ni is 0.0005 to 0.1% by weight. When the amount is less than 0.0005% by weight, the effect is not obtained. When the amount is more than 0.1% by weight, the improvement of the thermal fatigue property is reduced. In can also improve thermal fatigue properties and mechanical properties. Incorporation of In improves these properties without impairing other properties. The compounding amount of In is 0.01 to 0.5% by weight, preferably 0.01 to 0.3% by weight in the solder composition. If the amount is less than 0.01% by weight, the effect is not exhibited. If the amount is more than 0.5% by weight, the generation of oxides increases, which is not preferable. The present invention relates to Sn, A
By setting g, Bi, Cu, Ni, and P within the above ranges, it is possible to provide a lead-free solder having more excellent thermal fatigue characteristics than conventional Sn-Ag, Sn-Zn, and Sn-Sb-based lead-free solders. it can.

In order to obtain a solder alloy from the metal raw material having the composition of the present invention, a conventional solder production method may be used. In order to obtain a cream solder containing the solder alloy of the present invention, as is generally performed, a solder alloy is powdered into a powdered solder, and a suitable resin such as rosin,
It can be obtained by uniformly kneading with a flux containing a solvent such as glycols or polyhydric alcohols as a main component, and further containing an additive such as an activator, a viscosity modifier and an antioxidant by a conventional method. It can be prepared by a general method known in the art of molded solder and solder containing solder.

[0010]

EXAMPLES Examples 1 to 4 Each metal raw material having the composition shown in Table 1 was melted at 400 ° C. for 20 minutes to obtain a uniform alloy. (If possible, specify the method of manufacturing typical solder alloys, including the melting vessel and equipment.) The obtained alloys are evaluated according to the following evaluation methods to obtain tensile strength, elongation, and wetting properties. (Wetting time and wetting stress) and thermal fatigue resistance were evaluated. The results are shown in Tables 1 and 2.

[0011] creating the solder of Comparative Examples 1-6 with the composition described in Comparative Examples 1-6 in Table 1. The characteristics of the solders of Comparative Examples 1 to 6 were evaluated in the same manner as in the examples, and the results are shown in Tables 1 and 2.

[0012]

[Table 1]

[0013]

[Table 2]

[Evaluation method of solder alloy] Tensile strength and elongation: The solder alloy was kept at 400 ° C.
It was poured into a graphite mold heated to 270 ° C. and cooled at 6 ° C./sec to obtain a tensile test specimen having the shape shown in FIG. The test piece was subjected to a tensile test at room temperature at a tensile speed of 5 mm / min, and the elongation at break and the strength were determined. Wetting properties (for copper): 2 by meniscograph method
The wetting time and the wetting stress at 30 to 270 ° C. were evaluated. Nulling time: (About evaluation method of judging time and judgment criteria) Nulling stress: (〃
)

Thermal fatigue characteristics: Solder alloy 100 mm × 1
Eight 8-pin connectors were soldered on a 00 mm × 1.8 mm paper phenol substrate (back side: copper foil) at 250 ° C. This attachment mode is as shown in FIG.
This sample was subjected to a thermal shock test with a cycle of + 80 ° C. (30 minutes) to −40 ° C. (30 minutes), and the number of cracked pins was checked every 50 cycles up to 500 cycles. The crack occurrence rate was expressed by the following equation. (Crack occurrence rate) = (Number of cracked pins) / (Total number of pins)

[0016]

The lead-free solder alloy of the present invention contains no lead, has excellent thermal fatigue properties, and has good solderability.

[Brief description of the drawings]

FIG. 1 is a plan view and a side view showing the shape of a test piece for evaluating tensile properties of solder.

FIG. 2 is a cross-sectional view showing a mounting mode of a test piece for evaluating a thermal shock test of solder.

[Explanation of symbols]

1: Solder 2: Land (copper foil) 3: Phenolic resin board 4: Connector resin 5: Pin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yozo Yoshiura 3-8-10, Mitsutanaka, Yodogawa-ku, Osaka-shi, Osaka Inside Nihon Genma Co., Ltd. (72) Inventor Toshiyuki Moribayashi 3-chome, Mitsuya-naka, Yodogawa-ku, Osaka, Osaka No. 8-10 Inside Nihon Genma Co., Ltd.

Claims (7)

[Claims] 1. 0.1 to 10% by weight of Bi, 0.1 to 5% of Ag
Wt%, Cu 0.055-2 wt%, Ni 0.0005-
A lead-free solder alloy comprising 0.1% by weight, 0.0005 to 0.01% by weight of P, and the balance Sn. 2. The lead-free solder alloy according to claim 1, further comprising 0.01 to 0.5% by weight of In. 3. A cream solder containing the lead-free solder alloy powder according to claim 1. 4. A molded solder using the lead-free solder alloy according to claim 1. 5. A solder containing tin using the lead-free solder alloy according to claim 1. 6. A substrate using the salt-free solder alloy according to claim 1. 7. An electronic product using the salt-free solder alloy according to claim 1.