TWI684645B - Lead-free tin alloy - Google Patents

Abstract

The invention uses tin, palladium and copper to form a lead-free tin alloy, or tin, palladium, copper, phosphorus and gallium to form a lead-free tin alloy. Because the lead-free tin alloy contains palladium, it can increase the oxidation resistance of the lead-free tin alloy; contains phosphorus, which can slow down the oxidation of the lead-free tin alloy; and, the gallium contained will produce a dense gallium oxide film when oxidized, so Can prevent further oxidation of lead-free tin alloy. When the lead-free tin alloy of the present invention is subsequently used in a tin furnace in the wave soldering process, the amount of tin dross in the molten lead-free tin alloy is small, which can reach only about 1.33% of the weight of the lead-free tin alloy and the tin dross The color is white gray, so it is especially suitable for the wave welding process.

Description

Lead-free tin alloy

The invention relates to a lead-free tin alloy, in particular to a lead-free tin alloy with excellent oxidation resistance at high temperature.

Because lead compounds easily penetrate into groundwater and become a potential crisis for drinking water, the large amount of lead in various solder joints of general electronic products is discarded in nature after being discarded, which makes the high-tech electronics industry feel cautious; EU ( The European Union) RoHS (The Restriction of Hazardous Substances in Electrical and Electronic Equipment) directive, which clearly declares that electronic products are completely banned including lead (Lead), cadmium (Cadmium), mercury (Mercury), and hexavalent chromium ( Hexavalent Chromium), bromide flame retardants (Polybrominated Biphenyls, Polybrominated Diphenyl Ethers) and other substances. Due to the serious environmental pollution caused by lead and its compounds, and the aforementioned RoHS directive, in recent years, tin-lead alloys containing lead have been gradually restricted by international use in recent years, so they have been gradually replaced by "lead-free tin alloys".

Because the traditional lead-free solder (that is, lead-free tin alloy) requires a higher process temperature than the lead solder (that is, tin-lead alloy), and the lead-free solder cannot achieve the wetting effect like the traditional leaded solder, and in the tin furnace (Also called tin bath) When working in an atmospheric environment, because of the high operating temperature, lead-free solder will form more oxides (slag) than leaded solder, which directly affects the welding quality and welding strength. For example, the traditional lead-free tin alloy is a tin-copper alloy. This is because the tin-copper alloy has low cost, high mechanical strength, and good corrosion resistance. Therefore, the tin-copper alloy is often used in wave soldering . However, because the tin-copper alloy has a high content of tin and contains copper, the tin-copper alloy has a greater tendency to be oxidized even in an atmospheric environment at normal temperature; plus the temperature of the tin furnace during the wave soldering process It is higher than the melting point of the aforementioned tin-copper alloy. Therefore, as the temperature increases, the oxidation rate of the surface of the tin-copper alloy in the molten state (melt) in the tin furnace in contact with the atmosphere is accelerated. In the case of rapid oxidation, a layer of oxide scum (tin slag, tin oxide, tin oxide film) will form on the surface of the tin-copper alloy melt, which directly affects the welding quality and welding strength, thus causing the process The low yield rate leads to a substantial increase in production costs and limits its application. For example, tin slag will hinder the contact between the tin-copper alloy and the electronic parts pins, so that the tin-copper alloy cannot solder the electronic parts of the circuit board, which leads to the waste of the circuit board; or, the tin slag will remain on the circuit board The circuit board is uneven, which also leads to the waste of the circuit board. In addition, the thickness of the tin slag can also be judged from the appearance. The tin slag of the tin-copper alloy is usually darker in color, which means that the thickness of the tin slag (oxide film) is thicker, and the darker the color, the thicker the oxide film. The thicker, the higher the probability that the tin-copper alloy cannot weld the electronic components of the circuit board, resulting in a higher probability of scrapping the board.

In the existing technical field, although it is also possible to use a more activated flux to improve the solderability and install a nitrogen environment to reduce the generation of oxides, the use of a more active flux requires a higher cleaning process. In order to avoid the residual corrosion or electron migration of the flux; the equipment cost of installing the nitrogen environment is relatively high, and if the correct operation is not selected, it is easy to produce holes in the solder joints, resulting in the waste of the circuit board.

In other words, if the oxidation resistance of the lead-free tin alloy is not directly improved, even with the assistance of flux and nitrogen environment, in fact, there is actually very limited room for improvement in welding quality and welding strength.

Therefore, the novel lead-free tin alloy proposed by the author is a tin-palladium-copper alloy, which has excellent oxidation resistance at high temperatures. At the same time, the author also found that the liquid lead-free tin alloy formed by melting at high temperature in the tin furnace, the research on the composition of the surface oxide film found that the surface oxide film is mainly tin oxide (tin slag), at high temperature Under the test, if the lead-free tin alloy has good oxidation resistance, the amount of tin slag is also small, so the oxidation resistance of the lead-free tin alloy can be judged from the amount of tin slag. In more detail, if the amount of tin dross is more than one-third of the weight of the liquid lead-free tin alloy (containing one-third of the lead-free tin alloy), the oxidation resistance is poor; if the amount of tin dross is small If it only accounts for less than one-third of the weight of the liquid lead-free tin alloy (not including one-thirtieth), the lead-free tin alloy has good oxidation resistance or strong oxidation resistance. In other words, the greater the amount of tin slag, the worse the oxidation resistance of the lead-free tin alloy; the smaller the amount of tin slag, the stronger the oxidation resistance of the lead-free tin alloy.

In addition, the novel lead-free tin alloy (tin-palladium-copper alloy) proposed by the author has an amount of oxide slag (tin slag, tin oxide) generated in the tin bath. Compared with the traditional lead-free tin alloy, the lead-free tin alloy of this creation Tin alloy produces less tin slag and lighter color. If the tin slag has a dark color (such as dark yellow, orange, golden yellow), the oxidation resistance is poor; if the tin slag has a light color (white gray, light yellow), the oxidation resistance is good or the oxidation resistance is strong . In other words, the darker the tin dross, the worse the oxidation resistance of the lead-free tin alloy; the lighter the tin dross, the stronger the oxidation resistance of the lead-free tin alloy.

Therefore, the lead-free tin alloy with excellent oxidation resistance proposed by the author includes 0.0001wt% to 0.1wt% palladium and 0.5wt% to 8wt% copper, and the rest is tin.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.003 wt% to 0.1 wt% palladium.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.1 wt% of palladium and 0.5 wt% of copper.

Another embodiment of the lead-free tin alloy of the present invention includes: 0.0001wt% to 0.1wt% palladium, 0.5wt% to 8wt% copper, 0.001wt% to 0.005wt% phosphorus and 0.001wt% to 0.005wt % Gallium, the rest is tin.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.003 wt% to 0.1 wt% palladium.

In the foregoing lead-free tin alloy, the sum of the weight percentage value of phosphorus and the weight percentage value of gallium is less than or equal to 0.01 wt%.

In the foregoing lead-free tin alloy, the sum of the weight percentage value of phosphorus and the weight percentage value of gallium is equal to 0.01 wt%.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.005 wt% of phosphorus.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.005 wt% of gallium.

In the aforementioned lead-free tin alloy, the weight percentage of phosphorus is greater than the weight percentage of gallium.

The aforementioned lead-free tin alloy, wherein the lead-free tin alloy system contains 0.001 wt% of palladium, 0.7 wt% of copper, 0.005 wt% of phosphorus, and 0.002 wt% of gallium.

The present invention mainly uses a lead-free tin alloy composed of tin, palladium, and copper. Since lead is not intentionally added, the toxicity is greatly reduced. In addition, another embodiment of the lead-free tin alloy of the present invention is a lead-free tin alloy composed of tin, palladium, copper, phosphorus, and gallium. Since the lead-free tin alloy contains palladium, the oxidation resistance of the lead-free tin alloy can be increased (Anti-oxidation ability); Tin and copper contained in lead-free tin alloy will form eutectic, which can reduce the melting point of the alloy and improve mechanical strength and corrosion resistance; because lead-free tin alloy contains phosphorus, it can increase the fatigue resistance of lead-free tin alloy Strength, and phosphorus easily reacts with oxygen first, so the overall oxidation of lead-free tin alloys can be slowed down; the gallium contained in lead-free tin alloys will produce a dense layer of gallium oxide when oxidized, thus preventing further lead-free tin alloys Oxidation.

Therefore, the novel lead-free tin alloy proposed by the author has excellent oxidation resistance at high temperatures.

The present invention mainly provides a lead-free tin alloy, which is substantially free of lead (Pb). The foregoing substantially free of lead means that in principle, as long as the lead is unintentionally added to the tin alloy, such as unintentional but inevitable impurities or contact during the manufacturing process, it can be regarded as substantially free of lead based on the gist of the present invention Or it can be regarded as lead-free; and because lead often exists as an impurity in tin (Sn) or other metals, similar to a very small amount of impurities, it is difficult to completely remove it with general metallurgical techniques. At present, in various lead-free alloys, The definition of the upper limit of lead impurities has not yet been unified, and the definitions of some important associations in Europe, the United States, and Japan are: 0.1wt%Pb of European Union RoHS; 0.2wt%Pb of American JEDEC; 0.1wt%Pb of Japan JEIDA ; Where wt% refers to weight percentage, the following wt% refers to weight percentage.

A lead-free tin alloy of the present invention includes: 0.0001wt% to 0.1wt% palladium (Pd) and 0.5wt% to 8wt% copper (Cu), and the rest is tin. Another embodiment of the present invention is a lead-free tin alloy composed of tin, palladium, copper, phosphorus (P), and gallium (Ga). The lead-free tin alloy system can include: 0.0001wt% to 0.1wt% Palladium, 0.5wt% to 8wt% copper, 0.001wt% to 0.005wt% phosphorus and 0.001wt% to 0.005wt% gallium, the rest is tin. In order to avoid misunderstanding, the above term "the rest is tin" should not be understood as excluding other impurities that are unintentional but unavoidable in the manufacturing process. Therefore, the aforementioned term "the rest is tin" should be understood as supplementing the lead-free tin alloy to a weight percentage of 100% by weight, which is composed of tin plus inevitable impurities, if the impurities exist. In addition, the limits of the numerical ranges described in the scope of the present invention and patents always include end values.

The manufacture of the lead-free tin alloy of the present invention:

The lead-free tin alloy of the present invention can be manufactured by a lead-free tin alloy manufacturing method including the following steps: (1) prepare the corresponding material according to the corresponding metal composition and weight percentage; (2) heat the prepared material Melt and cast to form the alloy ingot of lead-free tin alloy. Of course, a manufacturing method similar to Taiwan Invention Patent Announcement I485027 can also be used to manufacture the lead-free tin alloy of the present invention.

The effect test and evaluation of the lead-free tin alloy of the present invention:

The present invention pewter no free tin alloy can be tested and evaluated by the following test methods and evaluation of one kind of: taking the alloy ingot was placed 600 g solder pot, heated to 400 ^o C and the alloy melt to form an ingot of the Lead The melt of tin alloy (also called tin liquid), and then keep the tin liquid for 2hr, at this time, a layer of surface oxide film (also called tin slag or oxide slag) will be formed on the surface of the tin liquid; then, first judge the surface The color of the oxide film and record it, then scrape the surface oxide film and place it on the balance to weigh it and record it.

Among them, when the weight of the oxidized slag is evaluated, if the weight of the oxidized slag is greater than or equal to one-third of the weight of the alloy ingot (about 3.33%), it is judged that the oxidation resistance is poor, which is converted to the weight of 600 g of the alloy ingot in the present invention. Multiplied by one-thirtieth equals 20 grams. Therefore, in the examples and comparative examples of the present invention, if the weight of the oxidized slag is greater than or equal to 20 grams, it is determined that the oxidation resistance is poor, and it is marked as "X". If the weight of the oxide slag is less than one-third of the weight of the alloy ingot (about 3.33%), and the weight of the oxide slag is greater than or equal to three-fourths of the weight of the alloy ingot (about 1.33%), it is judged that the oxidation resistance is good ( (Or oxidation resistance can be accepted), converted to alloy ingot weight 600 grams multiplied by three percent four equals 8 grams, so in the examples and comparative examples of the present invention, if the weight of the oxide slag is less than 20 grams and If it is greater than or equal to 8 grams, the antioxidant capacity is judged to be good, and it is marked as "△". If the weight of the oxidized slag is less than three percent of the weight of the alloy ingot (about 1.33%), it is judged that the oxidation resistance is strong (or called good oxidation resistance), so in the examples and comparative examples of the present invention, if the oxidation If the weight of the slag is less than 8 grams, the anti-oxidation ability is judged to be strong, and it is marked as "○".

In addition, when evaluating the color of the oxidized slag, if the color of the oxidized slag is dark, such as deep yellow, orange, or golden yellow, it is judged that the oxidation resistance is poor and marked as "X". If the color of the oxidized slag is light, such as light yellow, the oxidation resistance is judged to be good, and it is marked as "△". If the color of the oxidized slag is lighter, such as white gray, it is judged that the oxidation resistance is strong, and it is marked as "○".

Examples and comparative examples of the present invention:

According to the aforementioned method of manufacturing the lead-free tin alloy of the present invention, a lead-free tin alloy composed of each alloy described in the following Table 1 is prepared. Table 1 includes the lead-free tin alloy of the present invention as Examples 1 to 17, And Comparative Examples 1 to 3 as comparison with the Examples; and, by the aforementioned test and evaluation method of the lead-free tin alloy of the present invention, Examples 1 to 17 and Comparative Examples 1 to 3 Test and evaluate the color of the surface oxide film (oxidized slag) and the weight of the surface oxide film (oxidized slag) separately.

Table 1 Lead-free tin alloy Sn [wt%] Pd [wt%] Cu [wt%] P [wt%] Ga [wt%] P+Ga [wt%] Oxidation slag weight (g) and evaluation Oxidation slag color and evaluation Overall evaluation results of antioxidant capacity Example 1 margin 0.0001 0.5 0 0 0 10.1 △ Light yellow△ △ Example 2 margin 0.0001 4 0 0 0 10.4 △ Light yellow△ △ Example 3 margin 0.0001 8 0 0 0 10.8 △ Light yellow△ △ Example 4 margin 0.001 4 0 0 0 8.2 △ Light yellow△ △ Example 5 margin 0.003 4 0 0 0 7.6 ○ White gray ○ ○ Example 6 margin 0.005 4 0 0 0 7.3 ○ White gray ○ ○ Example 7 margin 0.01 4 0 0 0 6.4 ○ White gray ○ ○ Example 8 margin 0.1 0.5 0 0 0 5.2 ○ White gray ○ ○ ○ Example 9 margin 0.1 4 0 0 0 5.8 ○ White gray ○ ○ Example 10 margin 0.1 8 0 0 0 6.5 ○ White gray ○ ○ Example 11 margin 0.001 4 0.001 0.001 0.002 7.8 ○ White gray ○ ○ Example 12 margin 0.001 4 0.001 0.003 0.004 7.5 ○ White gray ○ ○ Example 13 margin 0.001 4 0.001 0.005 0.006 7.3 ○ White gray ○ ○ Example 14 margin 0.001 4 0.005 0.001 0.006 6.8 ○ White gray ○ ○ Example 15 margin 0.001 4 0.005 0.003 0.008 6.5 ○ White gray ○ ○ Example 16 margin 0.001 4 0.005 0.005 0.01 6.1 ○ White gray ○ ○ Example 17 margin 0.001 0.7 0.005 0.002 0.007 5.7 ○ White gray ○ ○ ○ Comparative example 1 margin 0 0.5 0 0 0 20.8 X Dark Yellow X X Comparative example 2 margin 0 4 0 0 0 21.4 X Dark Yellow X X Comparative Example 3 margin 0 8 0 0 0 22.1 X Dark Yellow X X

In Table 1, the meaning of Sn marked "remaining amount" is equivalent to the aforementioned term "the rest is tin". Therefore, the meaning of the aforementioned term "remaining tin" or "remaining amount" should be understood to make up the weight of the lead-free tin alloy to 100 wt% Examples of percentages. The meaning of "the overall evaluation result of the oxidation resistance" in Table 1 means the overall evaluation result of the oxidation resistance of the lead-free tin alloys of Examples and Comparative Examples, in which the same Example or the same Comparative Example is subjected to the foregoing Two evaluations, such as the weight of oxidized slag and the color of oxidized slag, if any "X" appears in the evaluation result, it is marked as "X" in the column of "Overall Evaluation of Antioxidant Capacity" in Table 1; If any "△" appears in the result, it is marked as "△" in the field of "Overall Evaluation of Antioxidant Capacity" in Table 1; if "○" appears in both evaluation results, then "" The column of "the overall evaluation result of antioxidant capacity" is marked as "○". If "X" appears in the overall evaluation result of the antioxidant capacity, it means that this embodiment or the comparative example has poor antioxidant capacity, which does not meet the requirements of the present invention; if "△" appears in the overall evaluation result of the antioxidant capacity, it represents This embodiment or comparative example has good antioxidant capacity and meets the requirements of the present invention; if "○" appears in the overall evaluation result of the antioxidant capacity, it means that this embodiment has strong antioxidant capacity, which not only meets the requirements of the present invention but is relatively good A preferred embodiment; if "○○" appears in the overall evaluation result of the antioxidant capacity, it means that this embodiment has strong antioxidant capacity, which not only meets the requirements of the present invention but is also the best embodiment.

Table 1 shows that the "Overall Evaluation Results of Antioxidant Capacity" of Example 8 and Example 17 is marked as "○○", so Example 8 and Example 17 are the best examples. Among them, in Example 8, the lead-free tin alloy includes: 0.1 wt% palladium, 0.5 wt% copper, and the rest is tin; in Example 17, the lead-free tin alloy includes: 0.001 wt% palladium, 0.7 wt % Copper, 0.005wt% phosphorus, 0.002wt% gallium, the rest is tin, and the weight percentage value of phosphorus (in this embodiment is 0.005wt%) and the weight percentage value of gallium (in this embodiment is 0.002wt%) The total value of is equal to 0.007wt%. It should be particularly noted that the judgment of the best embodiment, in addition to the weight of the oxidized slag and the color of the oxidized slag as the criteria for judgment, can additionally consider the cost of the lead-free tin alloy, for example, when the lead-free tin alloy As the weight percentage of palladium increases, the cost of the lead-free tin alloy also increases. The color of the oxidation slag of Example 17 and Example 8 are both white and gray, and the weight of the oxidation slag is that Example 17 (5.7 g) is heavier than Example 8 (5.2 g). The anti-oxidation ability of Example 17 is still strong, and Example 8 is the best example. However, if the cost of the lead-free tin alloy is taken into consideration, the weight percentage of palladium in Example 8 (0.1 wt%) is 100 times the weight percentage of palladium in Example 17 (0.001 wt%), which is obviously The cost is much higher than the cost of Example 17. In Example 17 and Example 8, the color of the oxide slag is the same (both are white and gray) and the weight of the oxide slag is similar (5.7 grams in Example 17 and 5.2 grams in Example 8). ) Under the condition that the oxidation resistance shown is all strong, when the cost of the lead-free tin alloy is measured, Example 17 is the best example.

In the entire creative conception process of the present invention, it is not easy to predict the characteristics that can be exhibited in the overall alloy from a single material, but it must be evaluated through the cumbersome manufacturing process (manufacturing process, preparation process) of the alloy, and By gradually changing materials or components with similar properties, explore the characteristics that may be required, and then determine whether the properties of each material or component can make the final lead-free tin alloy composition have better oxidation resistance. Therefore, the examples and comparative examples in Table 1 are explained as follows:

0.0001wt% to 0.1wt% palladium and 0.5wt% to 8wt% copper:

In a lead-free tin alloy, the weight percentage of added palladium will affect the oxidation resistance. The absence of added palladium will make the lead-free tin alloy fail the oxidation resistance test. The addition of palladium will increase the oxidation resistance of the lead-free tin alloy. However, an excessively high weight percentage of palladium will have a good oxidation resistance, but it will also lead to the high cost of lead-free tin alloy. In addition, the excessively high weight percentage of palladium will also cause the viscosity of the molten lead-free tin alloy to be too high, which is not conducive to the subsequent wave soldering process; and, the excessively high weight percentage of palladium will also lead to The lead-free tin alloy at the soldering position of the electronic part feet is brittle, which results in insufficient strength after soldering, and it is easy to fall off due to external force collision.

Comparative Example 1, Comparative Example 2 and Comparative Example 3 use 0.5wt%, 4wt% and 8wt% copper, respectively, and the overall evaluation result of the oxidation resistance is marked as "X", so Comparative Example 1, Comparative Example 2 and Comparative Example 3 has poor antioxidant capacity and does not meet the requirements of the present invention; while Example 1, Example 2 and Example 3 are similar to Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively, 0.5 wt%, 4wt%, 8wt% copper, but Example 1, Example 2 and Example 3 compared to Comparative Example 1, Comparative Example 2 and Comparative Example 3, 0.0001wt% palladium is used, which makes the implementation The overall evaluation results of the antioxidant capacity of Example 1, Example 2 and Example 3 are marked as “△”, which means that Example 1, Example 2 and Example 3 have good oxidation resistance and meet the requirements of the present invention. Similarly, Example 8, Example 9 and Example 10 also use 0.5wt%, 4wt% and 8wt% copper, respectively, but Example 8, Example 9 and Example 10 all use 0.1wt% Palladium, which makes the overall evaluation results of Example 8, Example 9 and Example 10 on the antioxidant capacity marked as "○", which represents the strong antioxidant capacity of Example 8, Example 9 and Example 10, in line with The requirements of the present invention.

Compared with Example 2 (using 0.0001 wt% of palladium), Example 4 uses 10 times the palladium content (using 0.001 wt% of palladium), and obviously the weight of the oxidized slag is reduced from 10.4 g of Example 2 to the example 8.2 grams of 4, that is, the oxidation resistance of Example 4 is higher than that of Example 2, so increasing the content of palladium helps to improve the oxidation resistance of the lead-free tin alloy. Example 5, Example 6, Example 7, and Example 9 all use 4wt% copper, compared with Example 2 (using 0.0001wt% palladium), Example 5, Example 6, Example 7, Example 9 uses 30 times (using 0.003wt% palladium), 50 times (using 0.005wt% palladium), 100 times (using 0.01wt% palladium), 1000 times (using 0.1wt% palladium) respectively Content, apparently the weight of the oxidized slag was reduced from 10.4 g in Example 2 to 7.6 g in Example 5, 7.3 g in Example 6, 6.4 g in Example 7, and 5.8 g in Example 9, ie the antioxidant capacity The order from low to high is Example 2, Example 4, Example 5, Example 6, Example 7, Example 9 because the increase in the content of palladium leads to the improvement of the oxidation resistance of the lead-free tin alloy.

The lead-free tin alloy of the present invention preferably contains 0.003 wt% to 0.1 wt% palladium.

The sum of the weight percentage value of phosphorus and the weight percentage value of gallium is less than or equal to 0.01wt%:

In lead-free tin alloys, adding and increasing the weight percentage of phosphorus and gallium will have better oxidation resistance. Example 11, Example 12, Example 13, Example 14, Example 15, Example 16 all use 0.001wt% palladium and 4wt% copper, and sequentially adopt the weight percentage value of phosphorus and the weight of gallium The sum of the percentage values is 0.002wt%, 0.004wt%, 0.006wt%, 0.006wt%, 0.008wt%, 0.01wt%, which is the sum of the weight percentage of phosphorus and gallium It is less than or equal to 0.01wt%. In addition, as the sum of the weight percent of phosphorus and the weight percent of gallium is increased sequentially, the weight of the oxidized slag also decreases sequentially, from 7.8 grams of Example 11 to 7.5 of Example 12 Grams, 7.3 grams of Example 13, 6.8 grams of Example 14, 6.5 grams of Example 15, 6.1 grams of Example 16. In other words, the oxidation resistance from low to high is Example 11, Example 12, Example 13, Example 14, Example 15, Example 16, in order. It should be particularly noted that the sum of the weight percentage values of phosphorus and gallium weights used in Examples 13 and 14 is 0.006wt%, and that of Example 13 uses 0.001wt% phosphorus and 0.005wt% The weight percentage of gallium and phosphorus is less than the weight percentage of gallium; Example 14 uses 0.005wt% of phosphorus and 0.001wt% of gallium, and the weight percentage of phosphorus is greater than the weight percentage of gallium. Since the weight of the oxidized slag of Example 13 (7.3 g) is greater than the weight of the oxidized slag of Example 14 (6.8 g), it is clear that the oxidation resistance of Example 14 is higher than that of Example 13, so for the lead-free tin alloy In other words, the weight percentage value of phosphorus is greater than the weight percentage value of gallium, which has better oxidation resistance.

In the lead-free tin alloy of the present invention, it is preferable that the sum of the weight percentage value containing phosphorus and the weight percentage value of gallium is equal to 0.01 wt%.

Phosphorus from 0.001wt% to 0.005wt%:

In a lead-free tin alloy, adding and increasing the weight percentage of phosphorus will slow down the oxidation of the lead-free tin alloy, thus improving the oxidation resistance of the lead-free tin alloy. In Example 11 and Example 14, the weight percentages of palladium, copper and gallium are the same, the only difference is that Example 11 uses 0.001 wt% phosphorus and Example 14 uses 0.005 wt% phosphorus. Since the weight of the oxidized slag of Example 11 (7.8 g) is greater than the weight of the oxidized slag of Example 14 (6.8 g), it is clear that the oxidation resistance of Example 14 is higher than that of Example 11, so for the lead-free tin alloy In other words, adding and increasing the weight percentage of phosphorus will increase the oxidation resistance of lead-free tin alloys. Similarly, Example 12 and Example 15, Example 13 and Example 16 have the same trend.

The lead-free tin alloy of the present invention preferably contains 0.005 wt% of phosphorus.

0.001wt% to 0.005wt% gallium:

In lead-free tin alloys, adding and increasing the weight percentage of gallium can prevent further oxidation of lead-free tin alloys, thus improving the oxidation resistance of lead-free tin alloys. In Example 11, Example 12, and Example 13, the weight percentages of palladium, copper, and phosphorus are all the same, the only difference is that Example 11 uses 0.001 wt% gallium, Example 12 uses 0.003 wt% gallium, Example 13 Use 0.005wt% gallium. Since the weight of the oxidized slag is 7.8 g for the slag of Example 11, 7.5 g for the slag of Example 12, and 7.3 g for the slag of Example 13, the antioxidant capacity is obviously from low to high It is Example 11, Example 12, and Example 13 in this order, so for the lead-free tin alloy, adding and increasing the weight percentage of gallium will increase the oxidation resistance of the lead-free tin alloy. Similarly, Example 14, Example 15, and Example 16 also have the same trend.

The lead-free tin alloy of the present invention preferably contains 0.005 wt% gallium.

Compared with the traditional conventional technology, the present invention mainly uses tin, palladium, and copper to form a lead-free tin alloy; in addition, another embodiment of the present invention is a lead-free tin alloy using tin, palladium, copper, phosphorus, and gallium. Composition of a lead-free tin alloy. Compared with conventional lead-free tin alloys, the lead-free tin alloys created in this work improve the oxidation resistance of lead-free tin alloys by means of palladium, phosphorus, and gallium.

The above-mentioned embodiments are only to illustrate the technical ideas and features of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, but cannot limit the patent scope of the present invention, That is to say, any equivalent changes or modifications made in accordance with the spirit disclosed by the present invention should still be covered by the patent scope of the present invention.

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Claims (7)

A lead-free tin alloy, comprising: 0.0001wt% to 0.1wt% palladium, 0.5wt% to 8wt% copper, 0.001wt% to 0.005wt% phosphorus and 0.001wt% to 0.005wt% gallium, the rest is tin. The lead-free tin alloy as described in item 1 of the patent application range, wherein the lead-free tin alloy contains 0.003 wt% to 0.1 wt% palladium. The lead-free tin alloy as described in item 1 of the patent application scope, wherein the sum of the weight percentage value of phosphorus and the weight percentage value of gallium is less than or equal to 0.01 wt%. The lead-free tin alloy as described in item 1 of the patent application scope, wherein the sum of the weight percentage value of phosphorus and the weight percentage value of gallium is equal to 0.01 wt%. The lead-free tin alloy as described in item 1 of the patent application range, wherein the lead-free tin alloy system contains 0.005 wt% of phosphorus, and the lead-free tin alloy system contains 0.005 wt% of gallium. The lead-free tin alloy as described in item 1 of the patent application, wherein the weight percentage value of phosphorus is greater than the weight percentage value of gallium. The lead-free tin alloy as described in item 1 of the patent application scope, wherein the lead-free tin alloy contains 0.001 wt% palladium, 0.7 wt% copper, 0.005 wt% phosphorus, and 0.002 wt% gallium.