Solder alloy, cast article, formed article, and solder joint

Abstract

A solder alloy has an alloy composition consisting of, in mass %, Cu: 0.1% to 2.0%, Ni: 0.01% to 0.4%, P: 0.001% to 0.08%, and Ge: 0.001% to 0.08%, with the balance being Sn. The alloy composition satisfies the following relations (1) to (3): (Cu+5Ni)≤0.945% (relation (1)), (P+Ge)≤0.15% (relation (2)), 2.0≤(Cu+5Ni)/(P+Ge)≤1000 (relation (3)). In the above relations (1) to (3), Cu, Ni, P, and Ge each represents a content (mass %) thereof in the solder alloy.

Claims

1. A solder alloy, having an alloy composition consisting of, in mass %: Cu: 0.1% to 0.6%; Ni: 0.01% to 0.4%; P: 0.001% to 0.08%; Ge: 0.001% to 0.08%; and optionally at least one selected from the group consisting of Mn, Cr, Co, Si, Ti, and rare earth elements in a total amount of 1% or less, with the balance being Sn, wherein the alloy composition satisfies the following relations (1) to (3): $\begin{array}{cc}\left(Cu+5Ni\right)\le 0.945\%& \mathrm{Relation}\left(1\right)\\ \left(P+Ge\right)\le 0.15\%& \mathrm{Relation}\left(2\right)\\ 2.0\le \left(Cu+5Ni\right)/\left(P+Ge\right)\le 1000& \mathrm{Relation}\left(3\right)\end{array}$ wherein, in the above relations (1) to (3), Cu, Ni, P, and Ge each represents a content in mass % thereof in the solder alloy, and when the solder alloy is used to produce a bar solder having a width of 10 mm and a length of 300 mm, the thickness of the bar solder is within a range of 7 mm±1 mm.

2. The solder alloy according to claim 1, having the alloy composition consisting of, in mass %: Cu: 0.1% to 0.6%; Ni: 0.01% to 0.4%; P: 0.001% to 0.08%; and Ge: 0.001% to 0.08%, with the balance being Sn.

3. A cast product comprising the solder alloy according to claim 1.

4. A cast product comprising the solder alloy according to claim 2.

5. A formed product, formed from the cast product according to claim 3.

6. A solder joint, obtained from the cast product according to claim 3.

7. A formed product, formed from the cast product according to claim 4.

8. A solder joint, obtained from the cast product according to claim 6.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing the range of the present invention in which the relation (2) is taken as the x-axis and the relation (1) is taken as the y-axis.

(2) FIG. 2 is an enlarged view of FIG. 1 with the x-axis range being 0 to 0.01 and the y-axis range being 0 to 1.

DETAILED DESCRIPTION OF THE INVENTION

(3) The present invention is described in more detail below. In the description, “%” related to a solder alloy composition is “mass %”, unless otherwise specified.

(4) 1. Solder Alloy

(5) (1) Cu: 0.1% to 2.0%, and Ni: 0.01% to 0.4%

(6) Cu and Ni are essential elements which can contribute to control of the liquidus temperature of the solder alloy. In the case where both contents of Cu and Ni are within the above range, the flowability of the molten solder is optimized, so that a cast product having a desired thickness can be obtained. In terms of the lower limit, the content of Cu is 0.1% or more, preferably 0.14% or more, more preferably 0.5% or more, and still more preferably 0.6% or more. In terms of the lower limit, the content of Ni is 0.01% or more, preferably 0.02% or more, and more preferably 0.03% or more. On the other hand, in the case where at least one of the content of Cu and the content of Ni is more than the corresponding upper limit, the liquidus temperature rises and the flowability decreases. In terms of the upper limit, the content of Cu is 2.0% or less, preferably 1.0% or less, more preferably 0.89% or less, and still more preferably 0.75% or less. In terms of the upper limit, the content of Ni is 0.4% or less, preferably 0.1% or less, more preferably 0.07% or less, and still more preferably 0.055% or less.

(7) (2) P: 0.001% to 0.08%, and Ge: 0.001% to 0.08%

(8) P and Ge are essential elements which can contribute to prevention of the oxidation of the solder alloy and control of the flowability of the molten solder. In the case where at least one of the content of P and the content of Ge is less than 0.001%, the oxidation prevention effect cannot be obtained. In terms of the lower limit, the content of P is 0.001% or more, and preferably 0.002% or more. In terms of the lower limit, the content of Ge is 0.001% or more, and preferably 0.003% or more. On the other hand, in the case where at least one of the content of P and the content of Ge is more than 0.08%, the decrease in flowability due to the oxidation of Sn is prevented, but the liquidus temperature becomes high. In terms of the upper limit, the content of P is 0.08% or less, preferably 0.06% or less, more preferably 0.01% or less, still more preferably 0.005% or less, and particularly preferably 0.003% or less. In terms of the upper limit, the content of Ge is 0.08% or less, preferably 0.07% or less, more preferably 0.06% or less, still more preferably 0.01% or less, particularly preferably 0.007% or less, and most preferably 0.005% or less.

(9) (3) Relations (1) to (3)

(10) $\begin{array}{cc}\left(Cu+5Ni\right)\le 0.945\%& \mathrm{Relation}\left(1\right)\\ \left(P+Ge\right)\le 0.15\%& \mathrm{Relation}\left(2\right)\\ 2.0\le \left(Cu+5Ni\right)/\left(P+Ge\right)\le 1000& \mathrm{Relation}\left(3\right)\end{array}$

(11) In the relations (1) to (3), Cu, Ni, P, and Ge each represents a content (%) thereof in the solder alloy.

(12) As described above, each essential element of the solder alloy in the present invention has an optimum content for controlling the liquidus temperature of the solder alloy and the flowability of the molten solder. The content of each of the above essential elements is determined in order to prevent the decrease in flowability of the molten solder. The factors by which respective elements can control the flowability of the molten solder are different. When the constituent elements other than Sn are classified into element groups exhibiting similar effects and each group is made to satisfy the above relations (1) to (3), the solder alloy in the present invention having excellent castability can be obtained. Each relation is described in detail.

(13) (3-1) Relation (1)

(14) The relation (1) represents the balance of Cu and Ni in the solder alloy. As described above, Cu and Ni are elements which can control the liquidus temperature. In addition, since the contents of both elements determine the precipitation amount of the compound produced during solidification, it is important to control the total amount of both elements in order to optimize the flowability of the molten solder.

(15) In the solder alloy in the present invention, in the case where the relation (1) is more than 0.945%, the liquidus temperature rises. Even in the case where the relation (1) is more than 0.945%, it is within an allowable range for flow soldering. However, in order to produce a desired cast product, in terms of the upper limit, the relation (1) needs to be 0.945% or less. The relation (1) is preferably 0.940% or less, and more preferably 0.875% or less. The lower limit of the left side of the relation (1) is not particularly limited, and the left side of the relation (1) is preferably 0.150% or more, more preferably 0.240% or more, still more preferably 0.250% or more, even more preferably 0.650% or more, particularly preferably 0.750% or more, and most preferably 0.850% or more.

(16) (3-2) Relation (2)

(17) The relation (2) represents the total amount of P and Ge in the solder alloy. Both elements can control the flowability of the molten solder by preventing oxidation. Since the reaction rates in the atmosphere are different between these elements, it is important to control the total amount of both elements in order to optimize the flowability of the molten solder.

(18) In the solder alloy in the present invention, in the case where the left side of the relation (2) is more than 0.15%, the liquidus temperature of the solder alloy rises. In terms of the upper limit, the relation (2) is 0.15% or less, preferably 0.12 or less, more preferably 0.085% or less, still more preferably 0.083% or less, even more preferably 0.050% or less, particularly preferably 0.015% or less, and most preferably 0.013% or less. The lower limit of the relation (2) is not particularly limited, and the relation (2) is preferably 0.002% or more, more preferably 0.004% or more, still more preferably 0.006% or more, and particularly preferably 0.008% or more.

(19) (3-3) Relation (3)

(20) The relation (3) represents the balance between the group of Cu and Ni and the group of P and Ge in the solder alloy. Although the elements belonging to each group have different factors for controlling the viscosity of the molten solder, it is considered that the two groups interact with each other in determining the viscosity of the molten solder. Therefore, in order to control the viscosity of the molten solder, the balance between the above two groups is necessary to be taken into consideration.

(21) In the solder alloy in the present invention, in the case where the relation (3) is less than 2.0, even if the contents of Cu and Ni are optimal, the content of P and Ge is too large and the liquidus temperature of the solder rises. In terms of the lower limit, the relation (3) is 2.0 or more, preferably 5.67 or more, more preferably 10.00 or more, still more preferably 10.24 or more, even more preferably 18.75 or more, particularly preferably 31.25 or more, and most preferably 56.67 or more. Further, in terms of the lower limit, the relation (3) may be 65.38 or more, 81.25 or more, 93.75 or more, or 106.25 or more.

(22) On the other hand, in the case where the relation (3) is more than 1000, even if the contents of Cu and Ni are optimum, the contents of P and Ge are too small, so that Sn in the molten solder is oxidized and the flowability of the molten solder decreases. In addition, even if the contents of P and Ge are optimal, the contents of Cu and Ni are too large, so that the liquidus temperature of the solder alloy rises, the viscosity increases too much, and the flowability of the molten solder decreases, making it impossible to perform casting. In terms of the upper limit, the relation (3) is 1000 or less, preferably 472.5 or less, more preferably 470.00 or less, still more preferably 425.00 or less, even more preferably 212.50 or less, particularly preferably 141.67 or less, and most preferably 118.13 or less. The relation (3) may be 117.50 or less, or 109.38 or less.

(23) (4) At least one selected from at least one group of: the group consisting of at least one of Bi, In, Sb, Zn, and Ag in a total amount of 5% or less; and the group consisting of at least one of Mn, Cr, Co, Fe, Si, Ti, and rare earth elements in a total amount of 1% or less

(24) With regard to these elements, as long as the total amount of at least one of Bi, In, Sb, Zn, and Ag is 5% or less and the total amount of at least one of Mn, Cr, Co, Fe, Si, Ti, and a rare earth elements is 1% or less, the castability of the solder alloy in the present invention is not influenced. In the present invention, the term “rare earth element” refers to 17 kinds of elements which are Sc and Y, belonging to Group 3, and 15 elements of the lanthanum group corresponding to the atomic numbers 57 to 71 in the periodic table.

(25) In the present invention, at least one of Bi, In, Sb, Zn, Ag, Mn, Cr, Co, Fe, Si, Ti, and a rare earth element may be contained. With regard to the content of each element, the total amount of at least one of Bi, In, Sb, Zn, and Ag is preferably 5% or less, and the total amount of at least one of Mn, Cr, Co, Fe, Si, Ti, and a rare earth element is preferably 1% or less. The total amount of at least one of Bi, In, Sb, Zn, and Ag is more preferably 1% or less, and the total amount of at least one of Mn, Cr, Co, Fe, Si, Ti, and a rare earth element is more preferably 0.5% or less.

(26) (5) Balance: Sn

(27) The balance of the solder alloy in the present invention is Sn. In addition to the above elements, inevitable impurities may be contained. Even in the case where inevitable impurities are contained, the effects described above are not influenced. Further, as described below, even when an element not contained in the present invention is contained as an inevitable impurity, the effect described above is not influenced.

(28) (6) Al

(29) The solder alloy in the present invention should not contain Al in order to avoid deterioration of wettability due to oxidation.

(30) 2. Cast Product

(31) Because the cast product in the present invention has an alloy composition of the solder alloy in the present invention, the cast product has a desired thickness. Examples of the cast product include a bar solder obtained by cut to have a predetermined length, as described below.

(32) 3. Formed Product

(33) A formed product in the present invention is a product formed from the cast product in the present invention. For example, examples thereof include a wire solder, a flux-cored solder, or a ring-shaped or tubular solder, each obtained by processing the cast product. In addition to this, examples thereof also include a solder powder obtained by melting and spraying, and those formed into a solder ball.

(34) 4. Solder Joint

(35) A solder joint in the present invention is formed by using the solder alloy in the present invention, and is used, for example, for connection between an IC chip and a substrate (interposer) thereof in a semiconductor package, or for connection between a semiconductor package and a printed circuit board.

(36) 5. Method for Producing Solder Alloy

(37) As for the method for producing the solder alloy in the present invention, the solder alloy is produced by, for example, a continuous casting method. In the continuous casting method, first, raw materials are added to a melting furnace so as to have a predetermined alloy composition and heated to approximately 350° C. to 500° C. to melt the raw materials.

(38) After all of the raw materials are melted, the molten solder in the melting furnace is continuously cast into the rotary mold.

(39) The rotary mold has, for example, a shape in which a groove is provided at the central portion in a width direction of the annular plate. When the molten solder is cast, the molten solder is cast into the groove of the mold while rotating the rotary mold. The amount of the molten solder supplied to the mold is appropriately adjusted depending on the rotation speed of the mold.

(40) The molten solder cast into the mold is cooled to approximately 150° C. at a cooling rate of about 10° C./s to 50° C./s. In order to obtain the cooling rate, the bottom of the rotary mold is immersed in cooling water, or the cooling water is circulated in the mold using a chiller or the like.

(41) The cooled solder alloy is guided to the outside of the mold via the guide, and is cut to have a predetermined length. The solder alloy reaching the guide has been cooled to approximately 80° C. to 200° C. In the solder alloy of the present invention, since the viscosity of the molten solder is controlled, a continuous cast product having a desired thickness can be produced.

(42) The casting method using a fixed mold may be a method in the related art. For example, raw materials are melted so as to have a predetermined alloy composition in the same manner as described above, then poured into a fixed mold and cooled at the above cooling rate. After cooling, the solder alloy can be produced by taking out the solder alloy from the mold.

EXAMPLES

(43) (1) Preparation of Evaluation Sample

(44) In order to demonstrate the effects of the present invention, a bar solder was prepared and evaluated as follows. Raw materials were weighed and added to a melting furnace, and melted in the melting furnace whose temperature was set to 450° C., and then molten solder was cast into the grooves of the rotary mold through which water was circulated. The cooling rate was approximately 30° C./s.

(45) The continuous cast product was then guided from the rotary mold to the outside of the rotary mold. Then, the continuous cast product was cut to have an appropriate length, and bar solders were prepared so as to have a total length of 10 m including a bar solder having a width of 10 mm and a length of 300 mm. The evaluation method is described below.

(46) (2) Evaluation Method

(47) The thickness of the prepared bar solder was measured with a caliper. The case where all the bar solders fell within the range of 7 mm±1 mm was evaluated as “∘”, and the case where at least one of the bar solders did not fall within the above range was evaluated as “X”. For “∘”, there is no problem in practical use.

(48) TABLE-US-00001 TABLE 1 Alloy composition (mass%) Relation (1) Relation (2) Relation (3) Thickness of bar Sn Cu Ni P Ge Optional element (%) (%) (%) solder Example 1 Bal. 0.1 0.03 0.003 0.005 0.250 0.008 31.25 ∘ Example 2 Bal. 0.6 0.03 0.003 0.005 0.750 0.008 93.75 ∘ Example 3 Bal. 0.7 0.03 0.003 0.005 0.850 0.008 106.25 ∘ Example 4 Bal. 0.89 0.01 0.003 0.005 0.940 0.008 117.50 ∘ Example 5 Bal. 0.6 0.01 0.003 0.005 0.650 0.008 81.25 ∘ Example 6 Bal. 0.6 0.055 0.003 0.005 0.875 0.008 109.38 ∘ Example 7 Bal. 0.1 0.169 0.003 0.005 0.945 0.008 118.13 ∘ Example 8 Bal. 0.7 0.03 0.001 0.005 0.850 0.006 141.67 ∘ Example 9 Bal. 0.7 0.03 0.01 0.005 0.850 0.015 56.67 ∘ Example 10 Bal. 0.7 0.03 0.08 0.005 0.850 0.085 10.00 ∘ Example 11 Bal. 0.7 0.03 0.003 0.001 0.850 0.004 212.50 ∘ Example 12 Bal. 0.7 0.03 0.003 0.01 0.850 0.013 65.38 ∘ Example 13 Bal. 0.7 0.03 0.003 0.08 0.850 0.083 10.24 ∘ Example 14 Bal. 0.1 0.01 0.003 0.005 0.150 0.008 18.75 ∘ Example 15 Bal. 0.7 0.03 0.001 0.001 0.850 0.002 425.00 ∘ Example 16 Bal. 0.7 0.03 0.08 0.07 0.850 0.15 5.67 ∘ Example 17 Bal. 0.89 0.01 0.001 0.001 0.940 0.002 470.00 ∘ Example 18 Bal. 0.1 0.169 0.001 0.001 0.945 0.002 472.50 ∘ Example 19 Bal. 0.14 0.02 0.06 0.06 0.240 0.12 2.00 ∘ Example 20 Bal. 0.7 0.03 0.003 0.005 Bi: 0.05 0.850 0.008 106.25 ∘ Example 21 Bal. 0.7 0.03 0.003 0.005 In: 0.05 0.850 0.008 106.25 ∘ Example 22 Bal. 0.7 0.03 0.003 0.005 Sb: 0.05 0.850 0.008 106.25 ∘ Example 23 Bal. 0.7 0.03 0.003 0.005 Zn: 0.05 0.850 0.008 106.25 ∘ Example 24 Bal. 0.7 0.03 0.003 0.005 Ag: 0.05 0.850 0.008 106.25 ∘ Example 25 Bal. 0.7 0.03 0.003 0.005 Mn: 0.01 0.850 0.008 106.25 ∘ Example 26 Bal. 0.7 0.03 0.003 0.005 Cr: 0.01 0.850 0.008 106.25 ∘ Example 27 Bal. 0.7 0.03 0.003 0.005 Co: 0.01 0.850 0.008 106.25 ∘ Example 28 Bal. 0.7 0.03 0.003 0.005 Fe: 0.03 0.850 0.008 106.25 ∘ Example 28 Bal. 0.7 0.03 0.003 0.005 Fe: 0.05 0.850 0.008 106.25 ∘ Example 29 Bal. 0.7 0.03 0.003 0.005 Si: 0.01 0.850 0.008 106.25 ∘ Example 30 Bal. 0.7 0.03 0.003 0.005 Ti: 0.01 0.850 0.008 106.25 ∘ Example 31 Bal. 0.7 0.03 0.003 0.005 Rare earth element: 0.850 0.008 106.25 ∘ 0.01 Comparative Bal. 3 0.03 0.003 0.005 3.150 0.008 393.75 x Example 1 Comparative Bal. 0.7 1.1 0.003 0.005 6.200 0.008 775.00 x Example 2 Comparative Bal. 0.7 0.03 0.0003 0.005 0.850 0.0053 160.38 x Example 3 Comparative Bal. 0.7 0.03 0.17 0.005 0.850 0.175 4.86 x Example 4 Comparative Bal. 0.7 0.03 0.003 0.0005 0.850 0.0035 242.86 x Example 5 Comparative Bal. 0.7 0.03 0.003 0.17 0.850 0.173 4.91 x Example 6 Comparative Bal. 0.7 0.055 0.003 0.005 0.975 0.008 121.88 x Example 7 Comparative Bal. 0.7 0.03 0.16 0.16 0.850 0.320 2.66 x Example 8 Comparative Bal. 0.1 0.01 0.17 0.17 0.150 0.340 0.44 x Example 9 Comparative Bal. 0.7 0.03 0.0003 0.0005 0.850 0.0008 1062.50 x Example 10 Comparative Bal. 3 1.1 0.003 0.005 8.500 0.008 1062.50 x Example 11 Comparative Bal. 0.1 0.02 0.08 0.07 0.200 0.150 1.33 x Example 12 The underlined value means that the value is outside the range of the present invention.

(49) As is clear from the results in Table 1, in each of Examples according to the present invention, a bar solder having a desired thickness could be obtained. On the other hand, since none of Comparative Examples satisfies at least one of the requirements of the present invention, a bar solder having a desired thickness could not be obtained. The fact that the content of each constituent element is necessary to satisfy the range of the present invention and the relations (1) to (3) are necessary to be satisfied is described with reference to the drawings.

(50) FIG. 1 and FIG. 2 are diagrams showing extracted Examples satisfying the relations (1) to (3) and extracted Comparative Examples not satisfying at least one of the relations (1) to (3) in Table 1, in which the relation (2) is taken as the x-axis and the relation (1) is taken as the y-axis. FIG. 2 is an enlarged view of FIG. 1 with the x-axis range being 0 to 0.01 and the y-axis range being 0 to 1. In FIG. 1 and FIG. 2, “∘” represents Example and “X” represents Comparative Example. Further, in FIG. 1 and FIG. 2, the region surrounded by the thick line is the range surrounded by the relations (1) to (3).

(51) As is clear from FIG. 1 and FIG. 2, all the solder alloys falling within the range surrounded by the thick line have a desired thickness. On the other hand, as shown in FIG. 1, the Comparative Examples not satisfying any of the relations does not have a desired thickness. Particularly, as shown in FIG. 2, it becomes clear from Comparative Example 7 not satisfying only the relation (1) and Comparative Example 10 not satisfying the relation (3), that the desired thickness may not be obtained even if the value is slightly out of the range surrounded by the thick line.