PCBA Tech - Smt processing assembly line production and Smt processing

In this era, most original equipment manufacturers (OEM) and electronic contract manufacturers have to use automated equipment to solder electronic components to printed circuit boards. In addition, the equipment used to process SMT components is completely different from the equipment used to process through-hole components. According to the production volume, the company has one or more SMT processing production lines. A typical SMT production line has the following configurations: automatic stencil printer, automatic placement machine and reflow oven with multiple areas.

SMT process

Printing is the first step of the SMT process, using an automatic stencil printer to apply solder paste on the exposed PCB pads. The mechanical fixture inside the printer fixes the PCB and the SMT stencil together, and the pads on the PCB and the holes on the template are perfectly aligned using the printer's vision system. The thickness of the template, the size of the hole, the pressure and speed of the squeegee control the amount of solder paste deposited on the SMT pads on the PCB.

smt patch

Mounting is the second step of SMT, using an automatic "pick and place" machine to place SMT components on the PCB. On this machine, the robotic device will automatically place the components on the PCB. Prior to this, the machine needs to be programmed with design files (Gerber files, BOM and CAD files, also called XY data). The CAD file contains the position and rotation information of all components on the BOM list.

Reflow soldering is the third step of the smt placement process, and the PCB is sent to the reflow oven. The solder paste is used as an adhesive to fix the components during heating. Program the oven with a thermal profile corresponding to the solder paste used. Once the solder paste reaches its reflow temperature, it will melt. In the case of double panels, each side must be completed separately. Only in strict accordance with all prescribed procedures can the quality of PCBA processing be guaranteed.

How to choose three anti-paint spraying and PCB potting in Smt processing

The characteristics of PCB potting:

Circuit board potting

Glue is mainly used for potting the circuit board in the BOX with epoxy resin, etc., which can provide a high level of protection for the circuit board. This high level of protection is ensured by the large amount of resin surrounding the entire unit. Compared with the three-proof paint spraying, this is obviously a much higher protection level. In fact, potting and conformal coating provide relevant protection. However, potting and conformal coating need to be tested in a variety of environments to determine their specifications and applicability. These tests usually involve exposing them to controlled atmospheric conditions for a period of time.

Characteristics of three anti-paint coating:

Three anti-paint spraying

In addition to potting, it can also be coated with three-proof paint to protect the circuit board. This is done by using a thin film to isolate the outside oxidation and moisture. Since the three anti-paint layer is sprayed according to the contour of the circuit board, it will not cause any size changes or significantly increase the weight. This is actually a big advantage in favor of conformal coating, because it is easy to make the device portable.

The difference between the two lies in the protection of the product and the impact on the weight and volume of the product. The specific method to be selected needs to be specifically evaluated according to the application scenario and use environment.