Basic Information About Solder Paste
In the 1970s, the surface mount technology (Surface Mount Technology, SMT for short) refers to printing and coating solder paste on the printed circuit board pads, and accurately placing the surface mount components on the On the solder paste pad, the circuit board is heated according to a specific reflow temperature profile to melt the solder paste. After the alloy composition is cooled and solidified, solder joints are formed between the components and the printed circuit board to achieve metallurgical connection.
2. Definition and Information
Solder paste is a new type of soldering material that came into being with SMT. Solder paste is a complex system, which is a mixture of solder powder, flux and other additives. The solder paste has a certain viscosity at room temperature, which can initially bond the electronic components to the predetermined position. At the soldering temperature, with the volatilization of the solvent and some additives, the soldered components and the printed circuit pads will be welded together to form Permanently connected.
（1 ）Preservation method
The storage of solder paste should be controlled at 1-10℃; the service life of solder paste is 6 months (unopened); it should not be placed in a place exposed to sunlight.
（2）How to use
(Before opening) The temperature of the solder paste must be raised to the ambient temperature (25±2℃) before opening, and the temperature recovery time is about 3-4 hours, and it is forbidden to use other heaters to increase the temperature instantly; after temperature recovery It must be fully stirred. The mixing time of the mixer is 1-3 minutes, depending on the type of the mixer.
（3）How to use
1) Add about 2/3 of the solder paste to the stencil, and try to keep the amount not more than 1 can on the stencil.
2) Depending on the production speed, the amount of solder paste on the stencil should be added in small amounts and multiple times to maintain the quality of the solder paste.
3) Solder paste that has not been used up that day should not be placed together with unused solder paste, and should be stored in another container. After opening the solder paste, it is recommended to use it up within 24 hours at room temperature.
4) When using the next day, you should use the newly opened solder paste first, and mix the unused solder paste the previous day with the new solder paste in a ratio of 1:2, and add them in small amounts for multiple times.
5) After the solder paste is printed on the substrate, it is recommended to place the parts into the reflow furnace within 4-6 hours to complete the dressing.
6) Please scrape the solder paste from the steel plate and put it into the solder paste tank before changing the wire for more than 1 hour.
7) After the solder paste is continuously printed for 24 hours, due to air dust and other pollution, in order to ensure the product quality, please follow the "step 4)" method.
8) In order to ensure the printing quality, it is recommended to manually wipe the openings on both sides of the steel plate every 4 hours.
9) Please control the indoor temperature at 22-28℃, and the humidity RH30-60% is the best working environment.
10) To wipe off the wrongly printed substrate, it is recommended to use industrial alcohol or industrial cleaning agent
3. Use matters
1) Manual stirring: Take out the solder paste from the refrigerator, open the cover after returning to room temperature (at 25°C, it takes about three to four hours), and stir the solder paste completely with a stirring knife. If the cap is broken, the solder paste will become a tin mass due to moisture absorption.
2) Use an automatic mixer: If the solder paste is only briefly warmed up after being taken out of the refrigerator, an automatic mixer is needed. Using automatic stirring will not affect the characteristics of the solder paste. After a period of stirring, the solder paste will gradually warm up. If the stirring time is too long, it may cause the solder paste to be higher than the operating room temperature, causing the solder paste to be poured on the board as a whole, and causing bleeding during printing, so be careful. Due to different machines, changes in room temperature and other conditions, different mixing times will be required, so please prepare enough tests before proceeding.
Contact Person: Mr. Ivan Zhu