JPH10286689A - Solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solder that dispenses with lead content causing a problem in environmental measures, that excels in heat resistance and thermal fatigue strength, and that enhances wettability and strength by using tin as the main component and adding a specific amount of antimony, silver, copper and nickel. SOLUTION: The composition is designed to contain, in weight %, 2.5-3.5% antimony, 1.0-3.5% silver, 1.0% or less copper or nickel, and the remainder to be tin. This solder has a melting point of 232-240 deg.C, with enhanced thermal fatigue property and with silver for the improvement in wettability of tin- antimony alloy; since the addition of silver causes lowering of the melting point, it is compensated by adding nickel and raising the melting point. The addition of copper is 1% or less, improving heat resistance and strength without impairing wettability, while its addition in excess will cause a rapid rise in the melting point. Similarly, the addition of nickel with 1.0% or less improves wettability, strength and thermal stability, but the excess addition will lower rolling workability, so that its content is confined within the above range.

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 for joining metals in electronic equipment, and more particularly to a "solder alloy" which does not contain lead and has good environmental friendliness.

[0002]

2. Description of the Related Art The properties required for performing "solder joining" include having a desired joining temperature, good "wettability" at the time of joining, excellent thermal fatigue strength and corrosion resistance, and environmentally friendly properties. It is desirable not to contain lead Pb from consideration. The "solder alloy" joint of the chip in the semiconductor device is an area joint with the metal conductor, and the "solder alloy" used for the joint to generate a large thermal strain due to the heat generation of the chip when power is applied is It will be placed in a severe use environment, and excellent thermal fatigue strength is required. Furthermore, depending on the semiconductor device, a plurality of "solder joints" may be required structurally, and in this case, a plurality of types of "solder alloys" having different joining temperatures are required, which is affected by a temperature profile in a later process. A difficult "solder alloy" is required.

[0003] Pb-Sn "solder alloys" and Sn-Sb "solder alloys" are known as conventional "solder alloys" for meeting these requirements. However, the conventional "solder alloy" has the following problems. Pb-Sn "Solder Alloy" has low tensile strength and high ductility, so it generates a large amount of strain and low fatigue strength, and has low thermal fatigue strength in combination with low heat resistance as described below. There is a disadvantage that. Pb-Sn “Solder alloy” is an alloy whose eutectic temperature is 183 ° C.
℃ to around 300 ℃, but the liquid phase temperature where only the liquid phase exists and the solid phase temperature where only the solid phase exists (18
The solid-liquid coexistence region between 3 ° C) becomes wider. Eutectic composition (63Pb
Even with high Pb “solder alloys” other than 37Sn), the solidification time during joining is usually short, and the ideal solidification process should be followed based on the binary phase diagram of high Pb-low Sn “solder alloy” And various forms of metal structures such as lead and tin, phases with high concentrations of each and a eutectic structure, and are difficult to stabilize. Further, in terms of heat resistance, there is a problem that since the eutectic temperature is 183 ° C., the material tends to deteriorate in a relatively low temperature range.

[0004] Further, Pb-Sn "solder alloy" is not desirable in terms of environmental measures because it contains Pb.

[0005]

[Problems to be solved by the invention] Pb-Sn "Solder alloy"
As a “solder alloy” that does not contain Pb and has good heat resistance in place of Sn, an Sn—Sb “solder alloy” having a melting point of 232-245 ° C. is widely known. Figure 4
It is a phase diagram which shows the phase equilibrium of Sn-Sb "solder alloy".

[0006] This state diagram is included in the Japan Institute of Metals Metals Data Book (1974 edition). Sn-Sb “solder alloy” is relatively strong and superior to Pb-Sn “solder alloy”. Sn-Sb “solder alloy” has a peritectic point (peritectic temperature of 245 ° C) at 8.5 wt% of Sb, and Sb is usually 8 watts.
Used below t%. Since melting occurs between the melting point of Sn of 232 ° C. and the peritectic temperature of 245 ° C., the solid-liquid coexistence region is narrow, the melting start temperature is high, and the heat resistance is excellent. By increasing the amount of Sb, a material excellent in strength can be obtained. However, Sn-Sb "solder alloy" had poor wettability at the time of solder joining, and the thermal fatigue strength was not sufficiently satisfactory.

The present invention has been made in view of the above points, and an object of the present invention is to provide an Sn-Sb-based "solder alloy" which is improved in Sn-Sb "solder alloy" and has excellent wettability and excellent thermal fatigue strength. It is in.

[0008]

According to the present invention, there is provided, according to the present invention, tin as a main component, 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver, and copper of 1.0 to 3.5% by weight. 1.0% by weight or less, or tin-based as the main component, 2.5 to 3.5% by weight of antimony, and 1.
This is achieved by including nickel in an amount of 0 to 3.5% by weight and not more than 1.0% by weight of nickel.

In Sn-Sb “solder alloy”, Sb is added to enhance the thermal fatigue properties at a melting point of 232 ° C. to 240 ° C., but the wettability is improved and the strength is further increased by Ag, Cu, Ni. Achieved by the addition of Addition of Ag improves fatigue strength and wettability. Ag is present at a high concentration at the crystal grain boundaries, and the fatigue strength is improved because the movement of the crystal grain boundaries is suppressed. However, Sn
-Ag alloy has a eutectic point at Sn-3.5wt% Ag (eutectic temperature 22
1 ° C), and the addition of Ag lowers the melting point, so the addition of Cu and Ni raises the melting point and can compensate for the lowering of the melting point. The strength of the alloy containing 3 wt% and the alloy containing 6 wt% is at the same level. Ag addition amount is 3.5w
If it exceeds t%, the melting point (liquidus temperature) becomes high, and it is necessary to increase the bonding temperature to ensure wettability, and the solid-liquid coexistence region becomes large.

[0010] The addition of Cu can reduce the Sn content without impairing the wettability.
Solid solution inside to improve heat resistance and alloy strength. Cu 3wt
% Or more, the melting point (liquidus temperature) sharply rises, and as pointed out in JP-A-5-50286, the amount of formation of intermetallic compounds (Cu ₃ Sn, etc.) increases, Strength is impaired. Even if 0.5% by weight of Cu is added, the strength is improved.

[0011] The addition of Ni brings about the thermal stability of the alloy due to its high melting point (1450 ° C), the effect of refining the crystal structure, the effect of improving the thermal fatigue properties by forming Ni-Sn compounds, and the Cu substrate. The formation of an intermetallic compound (Cu ₃ Sn), which lowers the bonding strength when bonding with a metal, is suppressed. When the amount of Ni increases (5 wt% or more), it becomes difficult to melt the alloy, and the viscosity increases at the time of joining, and the spreadability decreases. Ni content is 1.0 wt
%, The strength and wettability are improved. If the Ni content exceeds 1 wt%, the steel becomes hard and the rolling workability deteriorates.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION "Solder alloy" contains tin as a main component, 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver, and 1.0% by weight of copper. Sn-Sb-based "solder alloy" containing the following amounts, tin as a main component, 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver, 1.0% by weight of nickel Sn containing the following amount
-Sb-based "solder alloy" or tin as a main component, 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver, 1.0% by weight or less of copper, A Sn—Sb-based “solder alloy” containing nickel in an amount of 1.0% by weight or less is used.

FIG. 1 is a principal part enlarged tetrahedral diagram showing an optimum composition region of a "solder alloy" composed of Sn, Sb, Ag, and Cu.
FIG. 2 is an enlarged regular tetrahedron diagram showing an optimum composition region of a “solder alloy” composed of Sn, Sb, Ag, and Ni. FIG. 3 shows Sn, Sb, A
FIG. 4 is an enlarged regular tetrahedral diagram showing an optimum composition region of a “solder alloy” composed of g, Ni + Cu.

In this figure, the optimal composition regions are f ₁ , f ₂ , f ₃ , f ₄ ,
_{f 5, f 6, f 7} , f 8 , or _{f 1, f 2, f 3} ,, f 4, f 9, f 10, f
_11, f _12, in a region enclosed. Where f ₁ , f ₂ , f ₃ ,
The plane enclosed by f ₄ , is not included. When n is an integer of 1 to 12, f _n (Sb wt%, Ag wt%, Cu wt% or Ni wt% or (Cu + Ni) wt%, Sn wt%) is the “solder alloy” in the tetrahedron. The composition is shown. The weight percent of the metal is the length of the perpendicular drawn from each composition to four planes, with the height of the tetrahedron being 100. (Cu + Ni)% by weight is 1.0% by weight or less for each of Cu and Ni.

F ₁ (2.5, 1.0, 0, 96.5), f ₂ (3.5, 1.0,
0, 95.5), f ₃ (3.5, 3.5, 0,93.0), f ₄ (2.5, 3.5,
_{0, 94.0), f 5 (} 2.5, 1.0, 1.0, 95.5), f 6 (3.5, 1.
0,1.0, 94.5), f ₇ (3.5, 3.5, 1.0, 92.0), f ₈ (2.5,
3.5, 1.0, 93.0), f ₉ (2.5, 1.0, 2.0, 94.5), f ₁₀ (3.
5, 1.0, 2.0, 93.5) , f 11 (3.5, 3.5, 2.0, 91.0),
f ₁₂ (2.5, 3.5, 2.0, 92.0) “Solder alloy” is produced by melting Sn, Sb, Ag, Cu, and Ni raw materials in an electric furnace.

[0016]

EXAMPLE A metal having a purity of 99.99 wt% or more was used in the experiment. This ingot is cast into a mold and a tensile test piece (3 mm
φ) was prepared, and the wettability was measured using a part of the smelting raw material. The tensile test was performed at room temperature. The wettability was measured by a meniscograph method using a flux (RMA type). Heat the solder material to 280 ° C and melt it, 2 mm
After immersion using a copper wire of φ, the wetting force was measured.

Table 1 shows the melting point, tensile strength, elongation at break, and wetting force of each composition of the alloy. The numbers indicating the compositions in the table represent% by weight.

[0018]

[Table 1]

When the amount of Sb in the Sn—Sb alloy is increased, the tensile strength increases, but the wettability tends to decrease. Ag
When the added amount is increased, the strength is improved. However, the increase in strength level was almost the same whether Ag was added at 3 wt% or 6 wt%. Ag is effective in improving the wettability without significantly lowering the melting point, but when it exceeds 3.5 wt%, the melting temperature (liquidus) rises and the working temperature needs to be raised. The solid-liquid coexistence temperature range with the crystallization temperature of 221 ° C (solidus) is also widened. Therefore, the appropriate amount of Ag added for improving the strength and improving the wettability is 1 to 3.5 wt%.

When Cu or Ni is added to Sn-3wt% Sb, the strength is improved, and it can be seen that a strengthening effect is brought about. Sn-3wt% Sb-1wt% Ag-1wt% Cu with 0.5wt% and 1.0wt% of Ni added shows excellent wettability, indicating that the addition of composite improves wettability as well as strength. . In Sn-3% wtSb-3wt% Ag, the one with Cu and Ni added at 0.5wt% has the highest strength and the wettability is Sn-5wt% Sb `` Solder alloy '', Sn-8wt% Sb Superior to "solder alloy". Sn-3wt% Sb 3wt% Ag, 0.5wt% for "solder alloy"
The strength is increased 3 to 5 times by adding Cu and 0.5wt% Ni in combination. Even if Cu and Ni are added alone, they are effective in improving the strength, but adding them in combination is more effective in improving the thermal fatigue strength.

The Sn-Sb alloy has a melting point in the range of 230-245 ° C. and is characterized by having excellent heat resistance, but has a disadvantage in that it has poor wettability. As can be seen from the measurement results obtained in the above examples, by adding Ag, Cu, Ni, 4w
Compared to a Sn-Sb "solder alloy" containing tb or more of Sb, a "solder alloy" having remarkably superior strength, heat resistance, and improved wettability can be obtained.

[0022]

According to the present invention, the "solder alloy" contains tin as a main component, 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver and 1.0 to 3.5% by weight of copper. weight%
Or tin as a main component, 2.5 to 3.5% by weight of antimony, and 1.0 to 3% of silver.
5% by weight and 1.0% by weight or less of nickel. Compared to Sn-Sb "Solder alloy" containing 4% by weight or more of Sb, it has remarkably superior strength and heat resistance. Thus, a "solder alloy" having improved wettability was obtained. Since this alloy does not contain lead, an environmentally desirable "solder alloy" was obtained.

[Brief description of the drawings]

Fig. 1 Enlarged regular tetrahedron diagram showing the optimal composition region of a "solder alloy" composed of Sn, Sb, Ag, and Cu

Fig. 2 Enlarged main part tetrahedron diagram showing the optimal composition region of "Solder alloy" composed of Sn, Sb, Ag, Ni

FIG. 3 is an enlarged regular tetrahedron diagram showing an optimum composition region of a “solder alloy” composed of Sn, Sb, Ag, Ni + Cu

Fig. 4 Phase diagram showing phase equilibrium of Sn-Sb "solder alloy"

Claims (2)

[Claims] 1. A "solder alloy" containing tin as a main component, containing 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver and 1.0% by weight or less of copper. . 2. A "solder alloy" containing tin as a main component, containing 2.5 to 3.5% by weight of antimony, 1.0 to 3.5% by weight of silver and 1.0% by weight or less of nickel. .