PCB007 Magazine

PCB007-Dec2021

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118 PCB007 MAGAZINE I DECEMBER 2021 Plating Anomalies and Defects, Part 2 Introduction One of the most difficult things about trou- bleshooting PCB defects is getting to and understanding the root cause of defects. Many of these defects can have multiple origins, and many may not manifest themselves in the pro- cess where the defect occurred. us are the perils of jumping to conclusions about the defect. Oen, I get involved in solving technical issues and the engineer at the board fabrica- tor or OEM calls the defect an "anomaly." Not really a good idea to go off trivializing the pur- ported anomaly. Failure to understand the true genesis of the defect will lead to incorrect rem- edies to these issues. I will now present some of these defects and the possible remedies. Copper Plating Separation The common com- plaint one hears is "the copper plating is peel- ing." Okay, but where? From the surface or from within the via? Did one perform a proper micro- s e c t i o n ? I s t h e r e a n actual separation or is it debris lodged between the substrate and plating copper? And is the sepa- ration between the elec- troless copper and the electrolytic copper, or is it the electroless copper from the base cop- per? How oen does this problem continue due to an inability to get to the root cause? ese are the questions one must answer in order to work properly. Figure 1 shows a real example of a blistered or peeling deposit. e question is, what is the actual separation? Is it really a loss of adhesion of the plated deposit to the substrate or is it an inclusion of some sort? How about debris, drill dust, or dry film chips? In this situation, there could be debris on the surface of the copper foil or residues le behind from insufficient surface preparation or problems in developing the photoresist. In addition, these separations may be caused by Trouble in Your Tank by Michael Carano, RBP CHEMICAL TECHNOLOGY Figure 1: Arrows point to apparent separations or loss of adhesion of the plated copper.

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