Understanding The Stages of The Surface Mount Process
Surface Mount Technology has revolutionised the PCB designing process. Its on-surface mounting technique has given way to developing complex circuits with compact assemblies at a lesser cost. It makes use of SMD i.e. the Surface Mount Device which are electronic components used within the surface mount assembly process, they come in various shapes and sizes.
The Surface Mount Process starts with the designing of the PCB when based on the requirements, the components are selected and a layout is created. Once the design is finalised, the PCB is sent for manufacturing and the suited components are bought in to facilitate automation.
Stages of Surface Mount Process:
Machine Programming: After receiving the PCB panel and the components, the machines to be used are set up and programmed using CAD and Gerber data.
Solder paste Printing: The Solder Paste Printer uses stencil and squeegees to apply solder paste to the appropriate pads on the PCB. Nowadays, jet printers are making their way as post-printing modifications are more convenient. This is a critical phase, so be sure of any defects and unidentified defects will lead to defects further down the line.
Solder Paste Inspection: Based on the PCB design, there can be a separate machine used for the inspection or the solder printing machine can have the option of automated inspection. 2D and 3D technologies are used to enable a more thorough inspection of the print area including solder paste volume per pad.
Component Placement: The next step is placing the components where each component is removed from its packing using a vacuum or gripper nozzle, checked by the vision system and placed in the desired location. This is an automated system done at a very high speed. The technology used for this phase depends highly on the types and design of the PCB being manufactured.
Pre-Reflow Automated Optical Inspection: Once all the components are placed, the AOI i.e. Automated Optical Inspection machine is used to verify if all the components have been correctly placed.
First Article Inspection: The phase involves re-checking the first assembly design for any errors or defects. In the case of sub-contractors, they must get the first assembly verified by their customers. It might be time-consuming but is a very important step as any defect gone unnoticed can lead to high volumes of re-work.
Reflow Soldering: Once the component placement has been checked and verified, the PCB assembly moves into the soldering phase. The board is put into the reflow soldering machine where the PCB is heated to the desired temperature to form electrical solder connections between the components and PCB. The phase isn’t that complicated but the temperature needs to be managed to ensure acceptable solder joints without damaging the parts or assembly.
Post-Reflow Automated Optical Inspection: After the reflow Soldering, using the AOI machine the components are again checked for any errors or defects.
Process Verification using X-Ray Inspection: As many solder joints are hidden, there is a need to re-investigate the PCB using an X-Ray machine. X-Ray inspection provides a way to check underneath components such as BGA’s, the amount of voiding present within solder joints and also can be used to verify the solder hole fill after the soldering process.
Washing and Drying: Once the entire PCB is built and tested well, it is finally washed and dried before being packed and shipped for delivery.
PCB manufacturing using the SMT is an automated system requiring minimal human intervention. But setting up the required machinery and software, verification of errors and component quality assurance does require expertise. That is why it is always suggested to choose a reputed brand like Gelco EMS for your PCB requirements.