SMT is a comprehensive system engineering technology, which includes substrates, design, equipment, components, assembly technology, production accessories and management. SMT equipment and SMT process require stable voltage, electromagnetic interference, anti-static, good lighting and exhaust emission facilities, special requirements for operating environment temperature, humidity, air cleanliness, etc., operators should also undergo professional technical training
In general, SMT workshop temperature of 25 + 3 ℃.
solder paste
1.Solder paste printing, the materials and tools required to prepare solder paste, steel plate, scraper, wipe paper, dust-free paper, cleaning agent, mixing knife.
2.Tin paste ingredients include: metal powder, solvent, flux, anti-sag agent, active agent, the main components of tin powder and flux, volume ratio of about 1:1, weight ratio of about 9:1
3. The flux begins to evaporate in the constant temperature area for chemical cleaning; The main function of flux in welding is to remove oxide, destroy the surface tension of molten tin and prevent reoxidation. Rosin - based flux can be divided into four types: R, RA, RSA, RMA;
4. lead solder Sn/Pb ratio of 63/37, melting point is 217 ℃. Lead-free solder Sn/Ag/Cu for 0.5/96.5/3.0, melting point is 217 ℃
5. Remove the solder paste from the refrigerator and gently stir it through two important processes before opening. The purpose of temperature recovery is to restore the temperature of the refrigerated tin paste to normal temperature for printing. If the temperature does not return, the PCB is easy to produce tin beads after reflow welding
steel mesh
1.The common manufacturing methods for steel mesh are:
etching, laser, electroforming
2.The commonly used SMT steel mesh is made of stainless
steel. Thickness 0.15mm(or 0.12mm)
3.SMT steel mesh hole is generally 4um smaller than PCB PAD can prevent the phenomenon of bad tin ball
heating furnace(reflow oven)
1.the oven temperature curve its highest temperature 215 ℃ is the most appropriate
2.When inspection, tin stove furnace temperature 245 ℃ more appropriate
3.RSS curve is heating - constant temperature - reflux - cooling curve;
red gum
1.Red gum is a kind of rare compounds, and the solder paste is different is the heated after curing, its freezing point temperature is 150 ℃, at this point, the red glue started directly by the paste body becomes solid.
Use on printer or dispenser
2.Please placed in the refrigerator frozen (5 + 3 ℃) for storage
3.When decorating the rubber hose, please use the special glue water machine for packaging to prevent bubbles from being mixed into the glue.
