JP2000079494A - Solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain unleaded low-melting point solder which is also superior in ductility, heat resistance and wettability by improving tin-bismuth Sn-Bi alloy. SOLUTION: This solder contains tin as the main component, 30-58 wt.% bismuth, 5 wt.% or less silver, and 0.3 wt.% or less germanium. This solder may also contain 0.2 wt.% or less nickel and 1% or less copper, in addition to tin, bismuth and silver as prescribed above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a "solder alloy" used in metal joining of electronic equipment, and more particularly to a "solder alloy" which does not contain lead and has no pollution and is environmentally friendly.

[0002]

2. Description of the Related Art When performing solder bonding in electronic equipment, etc., a "solder alloy" has a desired bonding temperature, good wettability at the time of bonding, and excellent ductility, thermal fatigue strength and corrosion resistance. Is required. In addition, it is desired that the “solder alloy” does not contain lead from environmental considerations. Conventional solder alloys include tin-lead Sn-Pb
Alloys, tin-silver Sn-Ag alloys, tin-antimony Sn-Sb alloys, and tin-bismuth Sn-Bi alloys.

[0003]

[Problems to be Solved by the Invention] Typical tin-lead Sn-P
The alloy 63Sn-37Pb (eutectic temperature 183 ° C) contains lead, which causes lead pollution and is not environmentally friendly. When performing "solder joining" of electronic devices, it is necessary to use multiple types of "solder alloys" having different joining temperatures several times due to the configuration of the device, and in order to guarantee the reliability of semiconductor components Semiconductor components have a peak temperature of 12
Heat cycle durability up to around 5 ° C is required.

[0004] A typical lead-free solder, Sn-Ag alloy, which replaces 63Sn-37Pb alloy (eutectic temperature 183 ° C), has a eutectic temperature of 221 ° C (3.5% by weight silver). Has a melting temperature of 232-245 ° C. This is because a lead-free alloy has a high melting temperature and may overheat and damage electronic components during a soldering operation. Therefore, as a lead-free solder, the melting point is lower than that of Sn-Ag alloy or Sn-Sb alloy, and when the assembly process requires soldering with different joining temperatures, these alloys can be soldered without melting and have a low melting temperature. Requires solder alloy.

[0005] As a "solder alloy" which is lead-free and has a low melting temperature, tin-based Sn added with indium
-In alloys are being considered. Eutectic point of Sn-In alloy is 118
° C. Another lead-free, low-temperature “solder alloy”, the Bi-In alloy, has a eutectic point of 75 ° C. The above-mentioned lead-free low-temperature “solder alloy” has a too low heat-resistant temperature. Tin
The Sn7.5Bi2Ag0.5Cu alloy, one of the bismuth Sn-Bi alloys, has a melting temperature of 200-220 ° C and a joining temperature of 240-250 ° C.
° C, which may or may not result in excessive heating and damage to electronic components. In addition, alloys containing several percent of bismuth, such as Sn7.5Bi2Ag0.5Cu alloy, have low ductility, have problems in workability and strength, and have a wide solid-liquid coexistence region of liquidus / solidus, and depending on parts, In some cases, bismuth concentration segregation occurs at the time of joining to cause peeling (lift-off phenomenon).

FIG. 1 is a graph showing the dependency of elongation (%) on the amount of added Bi (% by weight) for a conventional tin-bismuth Sn—Bi alloy. In the figure, ○ indicates the characteristic point of the Sn-Bi alloy, and Δ indicates the Sn-B
The characteristic points and mouths of the i-Ag alloy are characteristic points of the Sn-Bi-Sb alloy. The strain rate in elongation measurement is 0.2% / s. The ductility of Sn-Bi alloy (○) increases with the amount of Bi added,
After the peak, the concentration gradually decreases toward the eutectic composition (Bi 58% by weight). The melting point in the eutectic composition is 139 ° C. Bi30-50
In the weight percent range, the elongation of the Sn-Bi alloy is 50-90%.
Sn-Ag alloy (3.5 wt% silver) has an elongation of 20-30%,
In addition, Sn7 is a lead-free tin-bismuth Sn-Bi alloy.
Considering that 5Bi2Ag0.5Cu (melting temperature is about 200 ℃) shows an elongation of 10%, the elongation of Sn-Bi alloy in the range of Bi30-50% is sufficiently large. This is the same level of ductility as Sn-Pb “solder alloy”. The ductility of Sn-Bi-Ag alloy (◇) is Bi
In the range of 30-58% by weight, the content tends to be lower than that of the Sn-Bi alloy (）), but is still sufficiently large.

[0007] Sn-Bi obtained by adding 30 to 58% by weight of Bi to Sn
Alloys are known to have good ductility, as described above, but to have a lower melting temperature. 30 to 58 such Bi
When Sb, Ag or Ge is further added to the Sn-Bi alloy containing wt%, the heat resistance (among others, creep characteristics) of the obtained Sn-Bi alloy is improved. However, of Sb, Ag or Ge
When Sb and Ge are added, wettability is poor, and when Ag and Ge are added, heat resistance is improved, but wettability is not clear.

The present invention has been made in view of the above points, and an object of the present invention is to improve a tin-bismuth Sn-Bi alloy having a low melting point and good ductility so that the melting point is low, the ductility is good, and the heat resistance is improved. An object of the present invention is to provide a lead-free low-melting-point “solder alloy” having excellent wettability.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor device comprising tin as a main component and bismuth in an amount of 30 to 58%.
It is achieved by containing not more than 5% by weight of silver, not more than 5% by weight of silver, and not more than 0.3% by weight of germanium. According to the second invention, tin is a main component, 30 to 58% by weight of bismuth, 5% by weight or less of silver, 0.2% by weight or less of nickel,
This is achieved by containing 1% by weight or less of copper.

According to a third aspect of the present invention, tin is a main component, 30 to 58% by weight of bismuth, 5% by weight or less of silver, 0.3% by weight or less of germanium, 0.2% by weight or less of nickel, By 1% by weight or less. A tin-bismuth Sn-Bi alloy containing tin as a main component and containing 30 to 58% by weight of bismuth has a melting temperature of 140%.
Or around 180 ° C, with other metal elements added
The i-based alloy becomes a low melting point “solder alloy”.

The ductility of a tin-bismuth Sn-Bi alloy containing tin as a main component and containing 30 to 58% by weight of bismuth is equivalent to that of a Sn-Pb "solder alloy". Ag-Ge, Ag-Ni-Cu, or Ag-Ge, for tin-pismuth Sn-Bi alloy containing tin as main component and bismuth in 30-58% by weight
When Ni and Cu are added at a predetermined ratio, a "solder alloy" having better heat resistance and wettability in addition to melting temperature characteristics and ductility can be obtained. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION "Solder alloy" is Sn, Bi, Ag, Ge,
It can be prepared by melting Ni and Cu raw materials in an electric furnace. Each raw material used had a purity of 99.99% by weight or more. Sn is a main component in the “solder alloy” component. BI is
30 to 58% by weight, Ag is 5% by weight or less, Ge is 0.3% by weight or less, Ni is 0.2% by weight or less, and Cu is 1% by weight or less. The alloy composition contains Sn as a main component and contains 30 to 58% by weight of Bi, 5% by weight or less of Ag, and 0.3% by weight or less of Ge, and Sn contains 30% to 58% by weight or less of Bi, 5% by weight or less of Ag, and Ni0.2% Wt% or less and Cu1 wt% or less, and further contains Sn as a main component and Bi30 to 58 wt% or less.
It contains less than 5% by weight of Ag, less than 0.3% by weight of Ge, less than 0.2% by weight of Ni, and less than 1% by weight of Cu.

EXAMPLE A tensile strength test was performed at room temperature at a tensile rate of 0.2% / s using a test piece having a diameter of 3 mm. In order to examine heat resistance, a test piece of the same shape was used, and the applied stress was 0.2 kg / mm.
^{In 2} , the creep deformation resistance was measured. The wettability was evaluated by the meniscograph method. For example, Sn22Bi alloy or Sn43Bi
Tensile strength, elongation, creep deformation resistance,
Table 1 shows the measurement results of the wetting force.

[0014]

[Table 1] Sn43Bi2Ag alloy with 2% by weight of Ag added to Sn43Bi alloy
It can be seen that the tensile strength, heat resistance (creep deformation resistance), and wettability are improved compared to the Sn43Bi alloy. The improvement in heat resistance can be seen from the decrease in creep deformation resistance. Sn43Bi2Ag alloy with 0.05% by weight Ge added
The 43Bi2Ag0.05Ge alloy has significantly improved wettability and further improved tensile strength and heat resistance (creep deformation resistance) compared to the Sn43Bi2Ag alloy.

The Sn43Bi2Ag alloy was further added with 0.5% by weight of Cu and 0.1% by weight of Cu.
Sn43Bi2Ag0.5Cu0.1Ni alloy with 1 wt% Ni added
Compared to 43Bi2Ag alloy, the wettability is slightly reduced but the tensile strength and heat resistance (creep resistance) are further improved. The addition of Ni is expected to increase the heat resistance of the alloy because Ni has a high melting point and oxidation resistance.
And the formation of an intermetallic compound, the ductility is drastically reduced. In the Sn43Bi2Ag0.5Cu0.1Ni alloy, Cu, which forms a solid solution with Ni, is added together with Ni to suppress a decrease in ductility.

The Sn43Bi2Ag alloy was further added with 0.05% by weight of Ge and 0.1% by weight.
Sn43Bi2Ag0.05Ge doped with 5 wt% Cu and 0.1 wt% Ni
Compared to Sn43Bi2Ag alloy, 0.5Cu0.1Ni alloy has remarkably improved wettability, and both tensile strength and heat resistance (creep deformation resistance) are further improved. Sn43Bi2Ag0.05Ge0.5
The wettability of Cu0.1Ni alloy is almost the same as Sn43Bi2Ag0.05Ge alloy.

Next, FIG. 2 shows the result of investigation on the wettability when Ge was added to Sn58Bi2Ag0.5Cu0.1Ni. Evaluation was performed by a meniscograph method at 210 ° C. using 1 mm φ copper. The wetting force was clearly improved up to 0.3% as the amount of Ge added, and when it exceeded 0.3%, the wetting force decreased rather than the initial value. This is presumably because the oxide film of Ge was formed too much, and the bondability with copper was lowered.

[0018]

According to the first invention, the novel Sn-Bi alloy contains tin as a main component, 30 to 58% by weight of bismuth, 5% by weight or less of silver, and 0.3% by weight or less of germanium. Lead-free, low melting point “solder alloy” with excellent tensile strength, heat resistance, and wettability in addition to ductility
Is obtained.

According to the second invention, the novel Sn—Bi alloy contains tin as a main component, 30 to 58% by weight of bismuth, 5% by weight or less of silver, 0.2% by weight or less of nickel,
Since copper is contained in an amount of 1% by weight or less, a lead-free low melting point "solder alloy" having excellent tensile strength, heat resistance and wettability in addition to ductility can be obtained. Further, according to the third invention, the novel Sn-Bi alloy contains tin as a main component and bismuth at 3%.
0 to 58% by weight, 5% by weight or less of silver, 0.3% by weight or less of germanium, 0.2% by weight or less of nickel, 1% by weight or less of copper. Lead-free low melting point "solder alloy" with excellent wettability and wettability.

[Brief description of the drawings]

FIG. 1 is a diagram showing the dependency of elongation (%) on the amount of added Bi (% by weight) for a conventional tin-bismuth Sn—Bi alloy.

FIG. 2 is a graph showing the effect of the amount of Ge added (% by weight) on the wettability of a Sn—Bi alloy.

Claims (3)

[Claims] 1. A tin-based material comprising 30 to 58% by weight of bismuth, 5% by weight or less of silver, and 0.3% by weight of germanium.
"Solder alloy" characterized by containing not more than weight%. 2. A solder containing tin as a main component and containing 30 to 58% by weight of bismuth, 5% by weight or less of silver, 0.2% by weight or less of nickel and 1% by weight or less of copper. alloy". 3. A composition comprising tin as a main component, 30 to 58% by weight of bismuth, 5% by weight or less of silver, and 0.3% of germanium.
"Solder alloy" characterized by containing not more than 0.2% by weight of nickel, not more than 0.2% by weight of nickel, and not more than 1% by weight of copper.