Issue link: https://iconnect007.uberflip.com/i/1166358
30 PCB007 MAGAZINE I SEPTEMBER 2019 the repair happens to be on an internal layer, it is not visible but will still affect the finished product. Figure 5 shows what an inner layer repair looks like under magnification from the surface; it's hard to find with the naked eye. When viewed with the aid of a backlight, it can be seen that there has been an open circuit on the inner layer track and this has been track welded/repaired. Even if the repair is reliable, the track is reduced by more than the ac- ceptable IPC allowance. The track weld provides a track that is 65% thinner than it should be. In Figure 6, the red lines show how thick the track should be. We also have our own re- quirements, such as a specific minimum solder mask thick- ness and a cleanliness re- quirement that is above what IPC requires. We have de- fined tolerances for profiles, holes, and other mechanical features—all of which will contribute to the reliability and the longevity of the fin- ished product. This becomes that much more important when you realize that the finished product may have a life depending on it. Verification of Standards Designing and manufacturing a PCB at the lowest total cost does not necessarily mean price. A product built to specifications by a PCB producer with knowledge and experience—in- cluding an established and proven set of standards—will ultimately produce a product that will withstand its intend- ed lifecycle. The best way to reinforce the different stan- dards put on PCBs is by test- ing the performance and qual- ity of the end product. This can be done using cross-sec- tional testing as well as more in-depth testing of chemical properties seen on the board after manufacturing. NCAB gathers performance data on all their productions to further analyze the key per- formance indicators of main processes within the facilities. Figure 5: An inner layer repair under magnification from the surface. Figure 6: The red lines show how thick the track should be.