Issue link: https://iconnect007.uberflip.com/i/1259453
72 PCB007 MAGAZINE I JUNE 2020 the knee of the hole. When thin plating over the knee (often referred to as dishing) is en- countered, the most likely causes are exces- sive solution agitation, organic contamination in the copper plating electrolyte, or additional agent imbalance. Agitation is easily adjusted. Organic build-up must be rectified through so- lution purification. A final word on this defect analysis: There were clear issues that caused the plated cop- per to be below specification. On the day in question, there were several electrical issues, including lower direct current to be applied to the plating cell lead in part to lower plating thickness in the hole (Faraday's law). In addi- tion, the fabricator should look into improved drilling, more uniform solution agitation (less turbulence), and adjustment of the organic ad- ditives in the plating electrolyte. PCB007 Reference 1. Wikipedia, "Faraday's laws of electrolysis." Michael Carano is VP of technology and business development for RBP Chemical Technology. To read past columns or contact Carano, click here. (12 microns), which was obviously thinner than the specification. Could this have been a contributing factor? The answer is yes, clearly. In simple terms, the thinner copper did not provide sufficient strength to prevent the possible rupture of the copper during as- sembly. It is also possible that there was a micro-void that went undetected. Regardless, it resulted in a combination of rough holes due to poor drilling (excessive in-feed rates, slow up-feeds, incomplete cure of the lami- nate material). What went wrong in the electrolytic copper plating operation, at least for this part num- ber? Electroplating follows the rule of Fara- day's Law of Electrolysis [1] . Simply put, when electroplating any metal from a solution of its electrolyte (in this case, copper ions +2 valence in a water/acid solution), it takes so much current flowing per unit of time to reach the required plating thickness. This assumes excellent plating distribution and high effi- ciency. In the real world, there will be devia- tions that do not allow for the perfect distribu- tion and uniform plating thickness across the circuit board. Process engineers must use the tools available to optimize the plating distribution as much as possible. However, in this case, the tools were not used properly. As Figure 2 shows, plating is also related to the thin amount of copper at Figure 3: Blowholes or outgassing. (Source: Carano, Advanced Troubleshooting Course)