Nowadays, lead-free solder paste is increasingly valued by people because the lead-free solder paste currently in use is mainly environmentally friendly solder paste. Environmentally friendly lead-free solder paste must first better meet environmental protection requirements, ensure the solderability of lead-free solder and the reliability after soldering, and also take into account many issues such as the cost borne by customers. Let's have the solder paste manufacturer explain the features:

First of all, lead-free solder paste that is environmentally friendly is not includedODSSubstances that do not damage the ozone layer; Halogen elements are not included. YesPCBThe plate has no corrosion resistance after welding. High surface insulation resistance and good electrical performance; The weld points are full and bright. Rosin is transparent or light yellow in color.

Environmentally friendly lead-free solder paste can achieve excellent soldering results when operating under the specified parameters. It can meet the high performance requirements of various circuit boards and can be used in conjunction with lead-free solder. The lead-free solder paste for environmental protection has no irritating smell, generates little smoke, is non-toxic to the human body, and causes no pollution to the environment. The lead-free flux for environmental protection has excellent solderability, full and bright solder joints, good solder penetration performance, and after solderingPCBThe surface is smooth and uniform, with good gloss and low odor. 

Environmentally friendly lead-free solder paste should have good wettability; Under normal circumstances, the residence time of solder above the liquid phase line is30-90The contact time between the solder pins and the circuit board substrate and the peak of the solder liquid during the solder bar wave soldering is seconds, while the contact time between the solder pins and the circuit board substrate and the solder liquid peak is4About a second. After using lead-free solder, the solder should exhibit good wettability within the above-mentioned time range to ensure high-quality soldering results. The melting point of lead-free solder paste for environmental protection should be low and as close as possible63/37The eutectic temperature of tin-lead alloy183Celsius, if the eutectic temperature of the new product is only higher183A few degrees Celsius is not a very big problem at all, but currently there is no better lead-free alloy to meet the lead-free solder requirements of this welding simultaneously. At the same time, before developing lead-free solders with relatively low eutectic temperatures, special attention should be paid to reducing the temperature difference between the melting intervals of lead-free solders. That is, it is important to remember to match the temperature range between the solid phase line and the liquid phase line, with the minimum solid phase line temperature being150Celsius, the working temperature depends on the specific application and should be as close as possible to the liquef-phase line temperature. (Solder strips for wave soldering:265Below Celsius; Xi Si:375Below Celsius;SMTUse solder paste:250Below Celsius, it is usually required that the reflow soldering temperature should be lower than225-230Celsius.

Lead-free low-temperature solder paste Its advantages are not only environmental protection, but also can be used for components that cannot meet the conventional temperature requirements, such asLEDorCOM1thePCB. There are mainly two types of lead-free solder pastes at low temperatures: tin and bismuth and Tin, bismuth, silver Of; The former138Celsius melting point, the latter183Melting point around Celsius; According to the actual product requirements, decide which one to use. Solder joints without silver will be more brittle.