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PCB manufacturer: Eight super details that cannot be ignored in the SMT process
2021-10-08
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Author:Aure

PCB manufacturer: Eight super details that cannot be ignored in the SMT process







As an electronic processing supplier, we must thoroughly understand all the processing processes in the factory, especially the main SMT processing process.

 

Inside each production workshop, there will be an SMT processing line. In this pipeline, we can be divided into the following parts.


 

1. Printing of lead-free solder paste
In the previous article, I mentioned the printing of lead-free solder paste. In this part, the machine we use is SMT semi-automatic printing machine. In this part of the operation, we should notice that the stencil is aligned with the PCB, the opening of the stencil and the PCB pad must be completely overlapped, and after the trial printing of 3 pieces, confirm OK to start normal production. After printing, each PCB must be self-inspected, and the printed solder paste is not allowed to appear excessive tin, less tin, continuous tin, offset and other undesirable phenomena. Badly printed products should be carefully cleaned. Wipe the stencil in time. Add solder paste in time to ensure the amount of solder paste rolling on the stencil.

 

2. Mounting of small materials
The machine we use in this process is a CP machine. Able to quickly place materials. Before starting up, you need to do enough preparations, such as the placement of materials, the positioning of the machine, and when the machine lights up in yellow, you should prepare to fill it with materials.

 

3. Placement of large materials
This process is to help the PCB add large materials that could not be mounted on the CP machine before, such as crystal oscillators. In this link, we are using an XP machine. It can realize the automatic placement of large materials. Note that the process is similar to the CP machine.

 


PCB manufacturer: Eight super details that cannot be ignored in the SMT process



4. QC in front of the furnace
This link is an essential and important link in the entire SMT process. This link can ensure that all the semi-finished products are completely free before the furnace, so it is called QC before the furnace. This position usually uses a QC to check the PCB boards flowing out of the placement machine. See if there are any leakage or partial material problems in the layout. Then manually correct the missing or partial board.

 

5. Reflow soldering
The function of reflow soldering is to melt the solder paste on the layout, so that the material is tightly soldered to the layout. The machine required for this process is wave soldering. There are also several points that should be paid attention to in wave soldering. The first is the adjustment of the temperature in the furnace, which requires comprehensive consideration of various aspects such as the degree of heating of the PCB board and the degree of heat resistance of the material, and then set the optimal temperature for the wave soldering, so that there will be basically no other problems after the PCB board passes the furnace. problem.

 

6. QC after the furnace
Quality is life. After the furnace, some problems will definitely occur, such as empty welding, virtual welding, continuous welding, etc. So how to find these problems? We must also be equipped with a QC in this link to detect the board surface problems after the furnace. Then make manual corrections.

 

7. QA sampling
After all the automatic placement processes are completed, we have the last step, which is random inspection. This step of random inspection can roughly evaluate the production pass rate of our products, that is, the quality. Of course, every step must be done carefully during random inspection, and every detail on the layout should not be missed, so as to ensure the quality of the company's products.

 

8. Warehousing
Final storage. It is also necessary to pay attention to the storage, and the packaging must be neat and not sloppy. Only in this way can we give customers a perfect experience.