What is "high temperature" and "low temperature"?
Generally speaking, it refers to the difference between the melting points of these two types of
solder paste. Conventional high-temperature solder paste with a melting point above 217°C is generally composed of tin, silver, copper and other metal elements. The reliability of high-temperature lead-free solder paste in LED patch processing is relatively high, and it is not easy to desolder and crack.
The conventional low-temperature solder paste has a melting point of 138°C. When the components of the patch cannot withstand the temperature of 200°C and above and the patch reflow process is required, low-temperature solder paste is used for the soldering process. In order to protect components and PCBs that cannot withstand high-temperature reflow soldering, its alloy composition is tin-bismuth alloy. The peak reflow temperature of low-temperature solder paste is 170-200°C.
(1) Characteristics of high temperature solder paste:
1. Good printing rollability and tinning performance, and can complete accurate printing for pads with a pitch as low as 0.3mm;
2. During continuous printing, its viscosity changes very little, and the operable life of the stencil is long, and it will not dry out after more than 8 hours, and still maintain a good printing effect;
3. After several hours of solder paste printing, it still maintains its original shape, without collapse, and the patch components will not shift;
4. It has excellent welding performance and can show proper wettability in different parts;
5. It can adapt to the requirements of different grades of welding equipment, does not need to complete welding in a nitrogen-filled environment, and can still show good welding performance in a wide range of reflow oven temperatures;
6. The high-temperature solder paste has very little residue after welding, is colorless and has high insulation resistance, will not corrode the PCB board, and can meet the requirements of no-cleaning;
7. It has better ICT test performance and will not cause misjudgment;
8. It can be used in the process of through-hole roller coating (Paste in hole);
9. Tin-silver-copper solder paste has a relatively high melting point and has higher requirements on the furnace, but tin-silver-copper solder paste has a good welding effect, high mechanical strength, less rosin residue, and is white and transparent. When printing high-temperature solder paste, it has good moisture retention, can obtain stable printability, and has excellent mold release performance. It can be printed continuously on the stencil for 8 hours. It has good solderability, good tin climbing, and full and bright solder joints.
(2) Characteristics of low temperature solder paste:
1. Melting point 138℃
2. Fully compliant with RoHS standards
3. Excellent printability, eliminating the omission of depressions and fast knots in the printing process
4. Good wettability, bright and full solder joints
5. No tin beads and tin bridges during reflow soldering
6. Long-term pasting life, steel screen printing life is long
7. Suitable for wide process and fast printing
What are the differences between high temperature solder paste and low temperature solder paste?
1. Different uses.
High-temperature solder paste is suitable for high-temperature soldering components and PCBs; while low-temperature solder paste is suitable for components or PCBs that cannot withstand high-temperature soldering, such as radiator module soldering, LED soldering, high-frequency soldering, etc.
2. The welding effect is different.
Look at reflow soldering. High-temperature solder paste has better weldability, is hard and firm, has few and bright solder joints; relatively poor solderability, solder joints are brittle, easy to detach, and the solder joints have dull luster.
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