TWI839955B - Use of indium-bismuth alloys as solder - Google Patents

Abstract

The present invention relates to a use of indium-bismuth alloys as solder for solving the problem that the copper electric soldering iron tips may be oxidized while tin, which has high melting point, is used as solder in prior arts. The present invention includes: providing an indium-bismuth alloy solder between a base plate and a conductor, wherein the melting point of the indium-bismuth alloy solder is between 60℃ and 120℃; coating a rosin between the base plate and the indium-bismuth alloy solder; heating a copper tip of an electric soldering iron to a temperature slightly higher than the melting point of the indium-bismuth alloy solder; making the copper tip of the electric soldering iron contact and thereby melt the indium-bismuth alloy solder to solder the base plate and the conductor, in the course of which a copper oxide layer formed on the copper tip of the electric soldering iron can be reduced by the rosin. According to the present invention, the solder can be melted at a low temperature, and the copper tip of an electric soldering iron is prevented from being oxidized.

Description

Use of indium-bismuth alloy as solder

This invention is about the use of an indium-bismuth alloy as a solder, especially the invention of using the low melting point of the indium-bismuth alloy as a solder for welding operations to prevent the copper soldering iron tip from oxidizing.

With the rapid development of science and technology, human beings have become inseparable from electronic products. Various electronic-related technologies have gradually become mature and efficient over time. As for the welding of electronic products, the most common solder used is tin. Due to its good ductility and welding performance, and its conductive properties, tin has become the most commonly used solder in the electronics industry. The melting point of tin is 232℃, and PCB circuit boards are commonly welded with electric soldering irons. The electric soldering iron tip is commonly made of copper, and the oxidation temperature of copper is approximately 200℃. Therefore, in order to melt tin for welding electronic components, the high temperature will cause oxidation of the copper electric soldering iron tip and/or damage to the electronic components.

The semiconductor layer components are bonded using indium-bismuth alloy as the bonding layer, such as US Patent Publication No. US09502376B2, which uses 66.7% indium and 33.3% bismuth. The melting point of the indium-bismuth alloy used in this case is about 120°C.

Therefore, in order to prevent the copper soldering iron tip from being oxidized due to welding, the inventor proposes a method of using an indium-bismuth alloy as a solder, which includes: placing an indium-bismuth alloy solder between a substrate and a conductor, wherein the melting point of the indium-bismuth alloy solder is between 60°C and 120°C; applying rosin between the substrate and the indium-bismuth alloy solder; heating a copper soldering iron tip of a soldering iron to a temperature slightly higher than the melting point of the indium-bismuth alloy solder; and making the copper soldering iron tip contact the indium-bismuth alloy solder to melt the indium-bismuth alloy solder to weld the substrate and the conductor.

Wherein, heating the copper soldering iron tip to a temperature slightly higher than the melting point of the indium-bismuth alloy solder means heating the copper soldering iron tip to a temperature 10% higher than the melting point of the indium-bismuth alloy solder.

Furthermore, the substrate and the conductor that were soldered using indium-bismuth alloy solder were kept at 100°C for 1 hour.

The indium-bismuth alloy solder is a mixture of indium and bismuth. The indium-bismuth alloy solder is in sheet form and has a thickness ranging from 0.01 mm to 1 mm.

Furthermore, the indium-bismuth alloy solder fills the interface gaps of the substrate and/or the conductor when in liquid state.

Furthermore, after the indium-bismuth alloy solder is heated and melted, an oxide layer will be further formed on the solidified surface, thereby preventing the indium-bismuth alloy solder from melting and flowing out due to heating again.

Among them, the tensile strength of the indium-bismuth alloy solder after solidification ranges from 5.90 kgf/mm2 to 9.66 kgf/mm2.

Wherein, the conductor is a wire or an electronic component pin.

Among them, the substrate is a circuit board.

The rosin will reduce the copper oxide layer produced by the copper soldering iron tip during the welding process.

Based on the above technical features, the following effects can be achieved:

1. By mixing indium and bismuth into an indium-bismuth alloy as solder, the copper soldering iron tip can effectively achieve the task of soldering electronic circuits at a temperature between 60℃ and 120℃, preventing the copper soldering iron tip from oxidizing due to high temperature and/or damaging the circuit board due to heat.

2. By coating the rosin between the substrate and the indium bismuth alloy solder, the surface tension between the substrate and the indium bismuth alloy solder is reduced and the wetting effect is achieved, ensuring that the indium bismuth alloy solder can flow or expand smoothly on the substrate surface after being melted. At the same time, the copper oxide layer produced by the copper soldering iron tip can be restored during the welding process. Since the rosin volatile temperature is 153°C, when welding is performed at 120°C, the rosin can prevent the metal on the substrate and the conductor surface from being oxidized, and can also avoid contact with oxygen for up to 1 hour.

3. The tensile strength of indium-bismuth alloy solder after solidification can reach between 5.90 kgf/mm2 and 9.66 kgf/mm2, which effectively reduces the risk of the soldered conductor separating from the substrate again.

4. Keeping the substrate and conductor soldered with indium-bismuth alloy solder at 100°C for 1 hour can increase the tensile strength of indium-bismuth alloy solder to 21.57 kgf/mm2.

5. When the indium-bismuth alloy solder melts, it is a low-viscosity liquid that can effectively fill the interface gaps of the substrate and/or conductor, providing a good transmission path for the transmission of electricity.

6. After the indium bismuth alloy solder is heated up for the first time, melted and solidified, an oxide layer will naturally form on the surface to protect the indium bismuth alloy solder from melting due to heating up again, causing it to flow out from the interface gap.

7. Since the viscosity of the indium bismuth alloy solder of the present invention is very low, it is difficult to control its flow direction during the welding process. By forming the indium bismuth alloy solder into a sheet structure with a thickness between 0.01 mm and 1 mm, and then cutting the sheet of indium bismuth alloy solder into the size of its welding plane, and directly placing it on the part of the substrate to be welded, the control difficulty is effectively reduced, and the indium bismuth alloy solder on the welding plane can be evenly distributed.

1: Substrate

2: Conductor

3: Rosin

4: Indium-bismuth alloy solder

[Figure 1] is a three-dimensional appearance diagram of the use of the indium-bismuth alloy of the present invention as solder.

[Figure 2] is a cross-sectional schematic diagram of the use of the indium-bismuth alloy of the present invention as solder.

Combining the above technical features, the main effect of the indium-bismuth alloy of the present invention as solder can be clearly presented in the following embodiments.

Please refer to the first figure, which discloses the use of indium bismuth alloy as solder in the embodiment of the present invention, including a substrate 1, a conductor 2, a rosin 3 and an indium bismuth alloy solder 4, wherein the indium bismuth alloy solder 4 is located between the substrate 1 and the conductor 2, and the rosin 3 is located between the substrate 1 and the indium bismuth alloy solder 4.

Specifically, the substrate 1 is a circuit board, the conductor 2 is a wire or an electronic component pin, and the substrate 1 and the conductor 2 are electrically connected through an indium-bismuth alloy solder 4, which is an indium-bismuth alloy formed by mixing indium and bismuth, and is used as a solder for welding. The melting point of the indium-bismuth alloy solder 4 is between 60°C and 120°C, and the tensile strength after solidification is between 5.90 kgf/mm2 and 9.66 kgf/mm2, and it has conductive properties, which effectively enables the welding operation to be achieved at a temperature between 60°C and 120°C, so as to prevent the copper soldering iron tip from being oxidized due to high temperature and/or the circuit board from being damaged due to heat.

In addition, the indium-bismuth alloy solder 4 of the present invention can also be selected from an indium-bismuth-tin alloy, wherein the indium-bismuth-tin alloy is a mixture of indium, bismuth and tin in the required proportion. If the amount of tin added is the lowest in the mixed proportion, it can still be implemented. The above proportions are only for example purposes and are not limited to this.

The rosin 3, also known as rosin, is coated between the substrate 1 and the indium bismuth alloy solder 4. It is a product obtained by removing the volatile components of turpentine from the oil resin of pine and coniferous trees. The melting point of the rosin 3 is between 110°C and 135°C, and the volatility temperature is 153°C. Therefore, when soldering is performed at 120°C, the rosin can prevent the surface metal of the substrate 1 and the conductor 2 from being oxidized, and can also avoid contact with oxygen for up to 1 hour. This is difficult for people with ordinary knowledge in the relevant technical field to guess. Since the melting point of the indium bismuth alloy solder 4 is lower than the melting point and volatility temperature of the rosin 3, the use of the indium bismuth alloy solder 4 for soldering does not affect the use of the rosin 3.

Please refer to the first and second figures. When actually performing the welding operation, the rosin 3 is evenly coated on the part of the substrate 1 to be welded. Since the viscosity of the indium bismuth alloy solder 4 of the present invention is very low, it is difficult to control its flow direction during the welding process. By forming the indium bismuth alloy solder 4 into a sheet structure with a thickness between 0.01 mm and 1 mm, and then cutting the sheet-shaped indium bismuth alloy solder 4 into a size that meets the welding plane, and directly placing it on the part of the substrate 1 to be welded, there is The control difficulty is effectively reduced, and the indium bismuth alloy solder 4 on the welding plane can be evenly distributed. Then, a copper electric soldering iron tip of an electric soldering iron is heated to contact the indium bismuth alloy solder 4 at a temperature 10% higher than the melting point of the indium bismuth alloy solder 4, so that the indium bismuth alloy solder 4 is changed from solid to liquid and flows between the conductor 2 and the substrate 1 coated with rosin 3. Then, the conductor 2 is brought close to or against the part of the substrate 1 to be welded to complete the welding operation. Since the indium bismuth alloy solder 4 passes through the rosin 3 on the substrate 1, the surface tension between the indium bismuth alloy solder 4 and the substrate 1 is reduced, and the wetting effect is further improved. In this way, the melted indium bismuth alloy solder 4 can increase fluidity and spread smoothly on the substrate 1, and can also reduce the copper oxide layer generated by the copper soldering iron tip during the welding process, and has a low viscosity in the liquid state. The indium bismuth alloy solder 4 with viscosity characteristics fills the interface gaps of the substrate 1 and/or the conductor 2, and covers or envelops the end of the conductor 2, so that the power has a good transmission path. Finally, after the indium bismuth alloy solder 4 is transformed into a solid state, the substrate 1 and the conductor 2 can be combined and electrically connected through the indium bismuth alloy solder 4 to complete the purpose of power transmission.

In addition, the present invention further uses the indium bismuth alloy solder 4 and the aforementioned indium bismuth tin alloy as solders at different temperatures, uses rosin 3 or citric acid to coat the substrate 1 and then performs a soldering operation to test the tensile strength of the indium bismuth alloy solder 4 or the indium bismuth tin alloy solder after being soldered between the substrate 1 and the conductor 2. Please refer to Table 1. When rosin 3 is coated on substrate 1 at 60°C and indium bismuth alloy solder 4 and indium bismuth tin alloy solder are used for soldering, the tensile strength after soldering is 2.50 kgf/mm2 and 1.90 kgf/mm2 respectively. When citric acid is used to replace rosin 3, the tensile strength is reduced to 0.40 kgf/mm2 and 1.50 kgf/mm2 respectively. When rosin 3 is coated on substrate 1 at 70°C and indium bismuth alloy solder 4 and indium bismuth tin alloy solder are used for welding, the tensile strength after welding is 9.66 kgf/mm2 and 7.80 kgf/mm2 respectively. When citric acid is used to replace rosin 3, the tensile strength is reduced to 4.40 kgf/mm2 and 4.10 kgf/mm2 respectively. When rosin 3 is coated on substrate 1 at 80°C and indium bismuth alloy solder 4 and indium bismuth tin alloy solder are used for welding, the tensile strength after welding is 8.60 kgf/mm2 and 6.30 kgf/mm2 respectively; when citric acid is used to replace rosin 3, the tensile strength is reduced to 4.70 kgf/mm2 and 0.60 kgf/mm2 respectively.

In general, the present invention uses indium-bismuth alloy as solder during welding, and the operation can be completed at a temperature between 60°C and 120°C, which effectively reduces the working temperature during the welding operation, avoids high-temperature oxidation of the copper soldering iron tip and/or damage to electronic components due to heat, or prevents the temperature from exceeding 153°C and causing the rosin 3 to evaporate completely. In addition, the tensile strength of the indium bismuth alloy solder 4 after solidification is between 5.90 kgf/mm2 and 9.66 kgf/mm2, which effectively reduces the risk of the conductor 2 being separated from the substrate 1 again after welding. If the substrate 1 and the conductor 2 are welded using the indium bismuth alloy solder 4 and kept at 100°C for 1 hour, the tensile strength can be increased to 21.57 kgf/mm2, and an oxide layer will be formed on the surface of the indium bismuth alloy solder 4 after solidification. Through the coating of the oxide layer, the indium bismuth alloy solder 4 will not melt due to heating again, resulting in outflow from the interface gap.

Combined with the description of the above embodiments, the operation, use and effects of the present invention can be fully understood. However, the above embodiments are only the preferred embodiments of the present invention and should not be used to limit the scope of implementation of the present invention. That is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention description are all within the scope of the present invention.

1: Substrate

2: Conductor

3: Rosin

4: Indium-bismuth alloy solder

Claims (9)

A use of an indium-bismuth alloy as a solder includes: placing an indium-bismuth alloy solder between a substrate and a conductor, the melting point of the indium-bismuth alloy solder being between 60°C and 120°C; coating a rosin between the substrate and the indium-bismuth alloy solder; heating a copper soldering iron tip of an electric soldering iron to a temperature slightly higher than the melting point of the indium-bismuth alloy solder; making the copper soldering iron tip contact the indium-bismuth alloy solder to melt the indium-bismuth alloy solder to solder the substrate and the conductor; keeping the substrate and the conductor soldered with the indium-bismuth alloy solder at 100°C for 1 hour. The use of indium-bismuth alloy as solder as described in claim 1, wherein heating the copper soldering iron tip to a temperature slightly higher than the melting point of the indium-bismuth alloy solder is heating the copper soldering iron tip to a temperature higher than 10% of the melting point of the indium-bismuth alloy solder in degrees Celsius. The use of indium-bismuth alloy as solder as described in claim 1, wherein the indium-bismuth alloy solder is a mixture of indium and bismuth, and the indium-bismuth alloy solder is in the form of a sheet with a thickness ranging from 0.01 mm to 1 mm. The use of the indium-bismuth alloy as a solder as described in claim 1, wherein the indium-bismuth alloy solder fills the interface gaps of the substrate and/or the conductor when in liquid state. As described in claim 1, the indium-bismuth alloy is used as a solder, wherein after the indium-bismuth alloy solder is heated and melted, an oxide layer will be further formed on the solidified surface, thereby preventing the indium-bismuth alloy solder from melting and flowing out due to heating again. The use of indium-bismuth alloy as solder as described in claim 1, wherein the tensile strength of the indium-bismuth alloy solder after solidification is between 5.90 kgf/mm2 and 9.66 kgf/mm2. The use of indium-bismuth alloy as solder as described in claim 1, wherein the conductor is a wire or an electronic component pin. The use of indium-bismuth alloy as solder as described in claim 1, wherein the substrate is a circuit board. The use of indium-bismuth alloy as solder as described in claim 1, wherein the rosin will reduce the copper oxide layer produced by the copper soldering iron tip during the soldering process.

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