Issue link: https://iconnect007.uberflip.com/i/1372612
MAY 2021 I PCB007 MAGAZINE 59 ter brainstorming some ideas and looking for possible linkages, sort them into groupings to better understand the root cause of the prob- lem. A fishbone diagram is particularly useful when you don't have very much quantitative data available, and can only rely on your team's experience. Fishbone diagrams show possi- ble linkages among the critical aspects of ma- chines, materials, people. See an example of a fishbone diagram in Figure 1. Once the team has set up its test plan based on a narrowing of potential causes, the divide- and-conquer approach will aid in the efforts. For example, if one suspects that thin plating of copper in the hole is caused by problems asso- ciated with the electrodeposition process, sim- ply processing the PCB in the acid copper plat- ing solution for the required time and current density should tell whether the copper plating process or the equipment (copper plating an- odes, rectifier, or electrical connections, etc.) are the cause. If not, then one must examine the previous steps. Did anyone check the ca- bles leading from the power supply to the plat- ing cell? Are there resistance issues with the plating racks or other connections that may cause less current to flow into the cell (Fig- ure 2)? Are there discontinuities in electroless copper deposit or direct metallization process causing thin plating? Are there voids in the vias that have not yet been detected? ese are just some of the questions to be asked. Only a sys- tematic approach will help solve problems ex- peditiously. Figure 1: Fishbone depiction of microvia interfacial fracture issue. (Courtesy of IPC-V-TSL and the IPC-V-MVIA committees) Figure 2: Acid copper electrolytic plating tank with excellent cable attachments from the rectifier to the bus bars, and multiple connections employed to improve current flow.