Issue link: https://iconnect007.uberflip.com/i/1383248
36 PCB007 MAGAZINE I JUNE 2021 Uneven—Unbalanced Copper Distribution Can Give Bow and Twist Layer-to-layer copper coverage: Within sev- eral layers causing low pressure areas through the bonding process of the board. In Figure 7, all features in red are balancing patterns on the inner layers. On this 14-layer board there were a total of eight nearly similar layers. Same Net Spacing Electrically nothing is wrong with this (Fig- ure 8), but during automatic optical inspec- tion (AOI) this will cause problems and delay in production. In the sample, the same net dis- tance is below 45 µm. Unwanted Angles—Causing Acid Traps In these sharp angles, chemicals from the processes can remain and cause reduced or broken connections over time (Figure 9). Some Parameters Can Be Set and Taken Care of During Post-Processing Do you keep or remove unused pads and vias? ere is no rule without exceptions, but my general recommendation is to keep pads on all layers for through-hole components and screw holes. Allow unused via pads to be removed if there is no risk for low pressure area. Do not remove all unused via pads in local areas where there is a high proportion of vias, such as typical BGA areas. BGA areas may require higher tempera- tures during soldering. is can promote de- lamination. Teardrops or Snowmen? My general recommendation is to enable this feature. I have been working with PCBs for decades. In the past year, I have held numerous semi- nars and webinars, talked to customers, im- proved designs, scrapped designs, helped stu- dents, made hundreds of drawings, explained the basics, experienced advanced technology and materials, and pushed the PCB design to its limits. Figure 7: All features in red are balancing patterns on the inner layers. Figure 8: In the sample, the same net distance is below 45 µm. Figure 9: a) The original; b) The routing has changed a bit and the SMT corners have also been rounded. A possible problem solved. a) b)