2D optical coordinate measuring
The iNEXIV VMA4540 from Nikon Metrology is used virtually, continuously for 2D optical coordinate measurement of machined features and copper tracks. It reinforces first article inspection of boards and printed reports, as well as process control in drilling, etching, and routing departments. The VMA4540 is used repeatedly during the life cycle of each new job. As 95% of SCL products only need positional and dimensional measurement of profiles, the machine is used exclusively in 2-D mode.
After the required number of layers has been bonded together to form a board, the first operation is CNC drilling using data sent from SCL’s CADCAM department, which considers stretching or shrinkage during subsequent stages of manufacture. The first-off from each batch of typically 25 is checked at this stage on the video measuring machine against the corresponding Gerber file, a vector format for 2D images used as standard in PCB industry software.
If any discrepancy is found, for example a hole is not present due to a broken drill, the measuring machine stops and flags up an error. An out-of-tolerance hole diameter or position, which typically need to be within ± 50µm and ± 100µm respectively, results in a similar error message. Normally, the PCB passes the inspection and a system report is prepared, although not normally printed out as it is rarely required by the customer.