After PCB design part completes, it is important to get the PCB manufactured, components sourcing and getting PCB assembled. The initial assembly is mostly for prototypes and for few units. Then bulk assembly is required, which is normally related to production. Normally it is very difficult to have one stop solution for PCB fabrication and manufacturing, then components sourcing and components assembly. Normally PCB is fabricated at one place, components are sourced separately and the assembled. Ideally, all PCB should come from same factory from start to finish. Any factory movement introduces element of risk and errors.
But nowadays, we have PCB plants with fabrication facility, components sourcing and assembly at one place. In this case, fabrication house have most of the basic components already available with them. All the types of components are used in assembly in modern set ups. These fabrication houses provide customers the convenience of a “One Stop Solution” to their PCB and PCB Assembly needs. Our advanced capabilities include Surface Mount (SMT), Thru-hole, Mixed Technology (SMT & Thru-hole), Single or Double Sided Placement, Fine Pitch Components, and so much more. Based upon turnaround time for customer requirements, it can be from 1-2 days to weeks. Quicker the turnaround time, higher the production cost Get More Info. The parts are procured based upon turnkey, out-sourced or Kitted/Consigned or partially turnkey.
The assembly process required stencils as they help in components placements and soldering/assembly. For bulk production, laser cut stainless steel stencils are used. The stencils are printed based upon pick and place files provided by PCB designer.
The PCB review is also done for error check. In general, PCB audits involve surface finish highlights, process control and analysis, cleanliness, recognizing common defects, testing and final inspection and material handling. The proper PCB packaging is required as a damage free approach is required. This is normally part of supply chain management. Some further and advance inspection method involves Automated X-ray inspection.
Automated X-ray inspection
This process is next step to automated optical inspection. In case of automated optical inspection, a camera autonomously scans the device under test for both catastrophic failure (e.g. missing component) and quality defects (e.g. fillet size or shape or component skew). It is commonly used in the manufacturing process because it is a non-contact test method. It is implemented at many stages through the manufacturing process including bare board inspection, solder paste inspection (SPI), pre-reflow and post-reflow as well as other stages.
In case of automated X-ray inspection, in place of visible light camera, X-ray is used to automatically inspect features, which are typically hidden from view. This method is rapidly accepted by industry, especially for complex and high density boards. X-ray images of solder joints can be analyzed automatically to detect structural defects, such as insufficient solder, voiding, shorts, opens, and other defects – that typically make up 80% to 90% of the total defects on an assembled circuit board. X-ray imaging can be used for 2D and 3D analysis of PCB. With increased PCB density due to SMT and BGA packages, the PCB is getting compact and smaller. During PCB design, most of the electrical defects are corrected as automated error checks help. The error generated during PCB manufacturing and assembly is mostly structural errors. X-rays therefore have a unique advantage for generating images of solder joints: the solder shows up extremely well, while most packages, the PC board substrate, silicon ICs, and component leads, become barely visible. This makes analysis of the solder joints straightforward. X-ray vision helps hidden features to be examined like in BGAs and other array-style packages, the heels of solder joints on fine pitch packages, and the internal characteristics of the solder joints themselves. Boards with defects not optically visible are an obvious fit for X-ray examination for e.g., BGAs, CGAs, CSPs, or components under RF shields. Many cell phones and wireless communication products are placing RF shields over unsoldered components at pick and place, using the reflow process to solder them to the board. X-ray inspection is the best way to isolate soldering defects obscured by the shields.
