DFA inspection is needed to ensure there will be no soldering defects. Your PCB fabricator may perform this inspection if they will contract with a preferred PCB assembler. However, if you’re using your own assembly house, you might want to send the design to your assembler so that they can evaluate the design. Assemblers are intimately familiar with automated soldering processes, and they might spot things a designer or fabricator will miss. Some common problems a designer can check include:
- Placement of thermal reliefs, which will prevent cold joints and a lift-off defect called tombstoning
- Solder mask expansion, which can prevent bridging between pins on a component
- Spacing between components
- Vias placed in SMD pads that have not been tented or plated
- Placement of solder mask dams near holes to prevent wicking
- The density of thermal vias on a component pad
This is just a short list of some of the points to check when preparing for PCB assembly, but they are the most important as these common problems can cause assembly failures. A PCB assembly team might also prepare a report for your review that outlines potential design changes that might be needed before a design can enter production.