Below a short description of the general process flow of SMT-line machines. The SMT-line cycle time can vary for different projects depending on the materials that are used.
1. The SMT-line process starts with preparation. We prepare and examine the SMC (Surface-mount components) and PCB whether any issues could arise during the process.
2. Preparation of the stencil that is used to provide a fixed position for the solder paste. The stencil is fabricated during the design process.
3. Next, we print solder paste onto PCB.
4. Then the solder volume and quality are inspected by SPI.
5. The electronic components are placed by the SMT pick and place machine.
6. Now the boards will be placed in the reflow soldering oven. The reflow soldering process contains several steps:
a. First, the boards will be preheated. The temperature rises gradually at this step.
b. Then they go into a soak zone where the boards are kept at temperatures from 140 to 160 degrees celsius for 60 to 90 seconds.
c. In the reflow zone, the temperature rises again by 1 to 2 degrees celsius per second and peaks at 210 to 230 degrees celsius. This will melt the mixture of the solder paste and bond the components together.
d. It's now time to cool down and ensure the solder mixture is set correctly.
7. Once the boards are cooled down after the reflow soldering process, they are ready for cleaning and inspection. First, the boards are cleaned, this gives an optimal view of whether there are any flaws, any repairs needed or other defects show. Inspection is done with the help of x-ray machines, ICT(In-circuit tester), AOI (automated optical inspection) and magnifying lenses.