The factors that caused tips easily-oxidized when using lead-free solder.
Lead-free solder oxidizes the tip of the soldering iron four to five times as fast as eutectic solder. Lead, one of the components of eutectic solder, relieves the oxidization of the tips. The lead-free solder, then, speeds up the oxidization. It is unavoidable that the life span of the tip decreases. Besides, the melting point of lead-free solder is approximately 30℃ higher than that of eutectic solder. Determining the preset temperature with little regard for the characteristics of lead-free solder, and leaving the tip at the high temperature of lead-free solder's melting point, speed up oxidization of the tips. Understanding the characteristics of lead-free solder and maintaining the soldering irons in a clean condition is the shortcut to preventing the soldering iron tips from oxidizing.
Set the preset temperature as low as possible to slow the oxidization of the tips. (Never increase the temperature to more than what you need.) The melting point of lead-free solder is higher than that of eutectic solder. Setting the preset temperature with little regard for the characteristics of lead-free solder could raise the temperature of the tip and speed up oxidization. Here, we suppose that you are wondering how one can solder securely with high-melting-point lead-free solder without raising the temperature of the soldering iron. It's the thermal recovery rate that answers your question.
Let us find the optimal temperature for the soldering iron using the formulas above when the melting point of solder is 180ºC.
180ºC + 50ºC = 230ºC
230ºC + 100ºC = 330ºC
The optimal temperature for the soldering iron is 330ºC.
The melting point of lead-free solder is about 30ºC higher than that of eutectic solder. The melting point of lead-free solder, when using the formulas above, is about 360ºC. It is risky to use different types of soldering irons as often as the type of solder changes when soldering the same items.
If the optimal temperature changes in a 30ºC range as often as the type of soldering iron changes, heat-sensitive parts will be negatively affected from the temperature changes. Consequently, both the thermal recovery efficient soldering irons and the thermal manageable soldering irons are required to keep the optimal temperature for the soldering iron for lead-free solder at the same temperature as that of the soldering iron for eutectic solder.
When using the thermal recovery efficient soldering irons, the formula above 2 will be:
The optimal temperature for the tip + about 60 to 70°C = the optimal temperature for the soldering iron The formula above cancels the increased temperature of the melting point of lead-free solder. In this way, the optimal temperature when using lead-free solder can be reduced to a temperature almost as low as the temperature needed for eutectic solder.
One of the soldering irons for lead-free solder that we would like to recommend, which meet the requirements above, is the HAKKO FX-951, FM series. Especially, we would like to recommend the HAKKO FX-951 and HAKKO FX-952 that accept the T12/T15 series, which has 84 variations of standard tips. For detailed information, click the URLs below.