First article inspection (FAI) prior to SMT assembly is a design verification methodology that provides a reported verification and validation of details of a product on the shopfloor per its manufacturing procedure and requirements. There are various ways to perform FAI, from both supplier’s and customer’s side, making it a very dynamic process. This means that each organization can tailor its FAI method to benefit itself and consequently, its customer, yet maintain rigid performance standards at the same time. FAI involves qualitative and quantitative measurement. FAI is also highly effective since it can potentially fulfill process validation requirements of quality management systems like ISO9001 or AS9100.
In the PCBA manufacturing industry, FAI can be effectively employed in validating materials for manufacture, underlying technologies, manufacturing processes used, packaging, and equipment. It can also be applied to a batch of a given sample-size from a mass-production instead of just the first sample, as the name might suggest. At PNC, strict adherence to our manufacturing standards helps in production with better yield but at the same time, facilitating dynamic validation techniques in our manufacturing process allows us to reduce lead time. The focus of FAI in PNC assembly lies in validating the pcb assembly before reflowing so that the SMT team can make necessary adjustments for the next batch, saving time and effort during rework. They are also responsible for validating the correct loading of the right component in its allotted slot per the assembly program. This extra step helps in validating the placements of the components and improves the turnout rate for a successful production.
All aspects of reflow also must be amenable to improve solder performance and the same translates to our guideline where only the most recent batch of solder paste (with most activity) is permitted for use, which is validated by FAI. Apart from pre-reflow FAI, post-reflow X-Ray also helps validate the solder performance based on the reflow profile which can then be adjusted accordingly so that all components are successfully soldered. This can be similarly implemented at the rest of the printed circuit board assembly stages as well up to testing. But there is a necessity to establish a constant groundwork or point of reference in such a dynamic process to give each validation at a particular stage, the perspective of what changes were made before. This is achieved by using a single piece of documentation used to validate at every stage, wherever applicable, and that document reports any changes made to the processes or product, to the next stage.
PNC employs the use of AEGIS software to combine SMT assembly guidelines and inspection requirements into a single document (internally referred to as AEGIS). The AEGIS is used to report every single FAI validation to different stages of assembly. PNC’s FAI process for SMT starts with thorough solder paste FAI & its validation, which will be detailed in another post. For this post, let us consider pre-reflow FAI and highlight its validation process since it is the most crucial stage. The procedure is as follows:
1. The SMT team confirms the correct allocation of components as given in the assembly program. This is done by comparing each component with its description, measuring component value wherever applicable, and checking for physical marking on ICs. This helps in validating that the right component has been placed in its respective position on the board.
2. The next step involves checking for the polarity of components, wherever applicable. This is a two-step process. First, the supply angle of a component in the reel needs to be checked and second, the placement of that very component on the PCB needs to be verified.
3. Now, once the first board is assembled, the pcb assembly is put through FAI, where the placements of all components on the board are checked, any necessary placements that remain are placed manually and polarities of applicable components are checked and changed as per what is given in the AEGIS. The same changes are made in the assembly program to avoid the same occurrence in the rest of the batch. Components that are designated as DNP (Do Not Place) are also checked and finally, the solder paste information such as solder type, lot number, date of manufacture, and expiry are checked to ensure that the right solder paste has been used.
4. All these checks translate to notes, remarks, and checks on the AEGIS document, which can then be referred at later stages up to final inspection. If the job in consideration is a repeat job, it can be optimized to avoid any errors made in the first batch of production.
5. The board is then sent through reflow. Once reflowed, the board is extensively inspected under high magnification camera for quality of component placement, solder joints etc. yielded by SMT process.
6. Each section in the AEGIS is meant for FAI by a different team performing a different operation.
PNC has been able to reduce its lead time and increase customer satisfaction significantly and our personalized and successful FAI is a big factor contributing towards it. Further development to the FAI process is underway as much as it is needed to achieve better production yield over time for all the different types of PC Board assembly that are assembled at PNC.