PCB Rework Strategies Pay
A well-thought-out rework strategy begins with EMS provider and OEM engineering getting together to map out a first article’s rework plan to include design-for-manufacturing (DFM) criteria. A process engineer at an EMS provider clearly defines all the steps a rework project requires.
Each step, its related issues, and the required assembly materials and processes are described in detail. Those details include such items as solder type, for example, whether the project calls for a “no clean” versus water-soluble solder; whether an active or passive flux is to be used; or if the PCB is to go to a wash after rework. Sometimes, a board cannot be washed due to its moisture sensitive components that are already assembled on the board. Therefore, those PCBs can be reworked with only no clean solder to avoid the wash and maintain component integrity.
Details like these are instrumental in a rework strategy. They comprise clear cut notes and instructions that rework personnel must follow to the letter. Those notes should use simple language to avoid ambiguity and confusion. This makes it easy for the rework technician to follow step-by-step instructions. Whenever possible, figures and illustrations added to these notes make the rework process more efficient.
There can be component, process, or assembly issues involved at rework. Rework can be solely focused on a component or group of components, on the PCB, itself, or at both component and board levels. It involves the number and types of components, as well as several other variables.
Once rework is performed on a PCB, it should be functional and fully operational. Reducing the number of rework cycles should be engineer’s main goal. Otherwise, subjecting a PCB through multiple rework cycles can fatigue it and its components will be tampered with to the extent the board’s integrity is jeopardized. Hence, performing as thorough a debug process as possible will subsequently contribute to reducing rework cycles to only one. This might involve a single page of rework instructions or sometimes even more. Once a seasoned rework engineering team follows those instructions carefully, the end of the rework process will yield a fully operational board.