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What are the trace metals often added in the soldering process of automatic soldering machine?

Release time:2020-11-04 15:27Popularity:
What are the trace metals often added in the soldering process of automatic soldering machine?Other metals are added to enhance the special requirements of the solder joint, such as improving the toughness and strength of the solder to obtain the desired mechanical, electrical and thermal properties.
What are the trace metals often added in the soldering process of automatic soldering machine?
So far, "TiN" is the world's best soldering materials for electronic parts, commonly used with TiN metals: silver (Ag), indium (In), zinc (Zn), antimony (Sb), copper (Cu), bismuth (Bi), etc.The characteristics and uses of the trace metals that may be contained in these solder pastes are summarized as follows:
Silver (silver) :
Generally speaking, "silver (AG)" is added to solder paste to improve the wettability of solder, enhance the strength of solder joint, and improve fatigue resistance.Favorite products with added silver pass the cold/hot cycle test, but if the silver content is too high (more than 4 % by weight), the solder joint will become brittle instead.
Zinc (zinc) :
Zinc (Zn) is a very common mineral, so its price is very cheap, almost as far as the price of lead.Although the melting point of zinc-tin alloy is lower than that of pure tin (melting point of 91.2Sn8.8Zn is 200C), the difference is not so obvious.And zinc has a big disadvantage.It reacts quickly with oxygen in the air (O2) to form a stable oxide layer that hinders the wettability of the solder.In the wave soldering process, a large amount of tin slag will be produced, and even affect the quality of solder.Therefore, the modern soldering process of zinc alloy was gradually ruled out.
Bismuth (Bi) :
Bismuth (Bi) is also significant in reducing the melting point of tin alloys.The melting point of Sn42Bi58 is only 138C, and the melting point of Sn64Bi35AG1 is only 178C. If it is tin/lead/bismuth alloy, the melting point can be as low as 96C. "Bi" has very good wettability and better physical properties.After the popularity of lead-free solder, the biggest drawback of tin-bismuth alloy is the lack of solder joint strength and brittleness, which is poor reliability, so a small amount of "silver" was added to improve solder joint strength and fatigue resistance.Unfortunately, its strength is still not satisfactory, so special care should be taken when choosing this low temperature solder alloy, or use glue to enhance its impact resistance and fatigue resistance.
What is the purpose of adding trace metal solder in the soldering process of automatic soldering machine
Nickel (Ni) :
Nickel (Ni) is not added to the solder to reduce the melting point, but the melting point of 100% pure tin is the lowest in the nickel-tin alloy ratio.The sole purpose of adding a small amount of nickel to the solder is to inhibit the dissolution of the copper substrate during soldering, especially to prevent the OSP plate from biting copper during the wave soldering process.It is generally recommended to use SnCunI (SCN) alloy tin bar with nickel added.
Copper (Cu) :
Adding a small amount of "copper (Cu)" to the solder increases the rigidity of the solder and thus the strength of the solder joint.A small amount of Cu can also reduce the corrosion effect of solder on the welding head of automatic soldering machine.Copper content in solder paste is usually required to be less than 1% by weight, if more than 1%, may endanger solder quality.

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