Difference between high temperature solder paste and low temperature solder paste
Generally speaking, high temperature solder paste is generally composed of tin, silver, copper and other metal elements, and the conventional melting point is above 217 ℃. In the LED chip processing, the reliability of high-temperature lead-free solder paste is relatively high, and it is not easy to desolder and crack.
The melting point of conventional low-temperature solder paste is 138 ℃. When the components of the patch cannot withstand the temperature of 200 ℃ or above and the patch reflow process is required, the low-temperature solder paste shall be used for the welding process. It can not withstand high-temperature reflow soldering of the original and PCB. Its alloy composition is tin bismuth alloy. The peak temperature of reflow soldering of low temperature solder paste is 170-200 ℃.
High temperature solder paste:
1.It has good printing rolling and tin dropping performance, and can also complete accurate printing for pads with a spacing as low as 0.3mm.
2. Several hours after the solder paste is printed, it still maintains its original shape without collapse, and the patch elements will not be offset.
3. It can meet the requirements of different grades of welding equipment, does not need to complete welding in nitrogen filled environment, and can still show good welding performance in a wide range of reflow furnace temperature.
4. The residue of high-temperature solder paste after welding is very little, colorless, has high insulation resistance, will not corrode PCB, and can meet the requirements of no cleaning.
5. It can be used in paste in hole process.
Low temperature soldering paste:
1. Excellent printability, eliminating omission, depression and fast knot in the printing process.
2. Good wettability, bright, uniform and full solder joints.
3. Suitable for wide process and fast printing.
4. Fully comply with ROHS standards.
High temperature solder paste is suitable for high temperature welding components and PCB; Low temperature solder paste is suitable for components or PCBs that cannot withstand high temperature welding, such as heatsink module soldering, led soldering, high frequency welding and so on.
The alloy composition of high temperature solder paste is generally tin, silver and copper (SAC for short); The alloy composition of low-temperature solder paste is generally Sn Bi series, including various alloy components such as SnBi, snbiag and snbicu. Sn42bi58 is a eutectic alloy with a melting point of 138 ℃, and other alloy components have no eutectic point and different melting points.
