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28 PCB007 MAGAZINE I NOVEMBER 2025 sive on the micro-etch. The result is poor or insuf- ficient anchoring of the electrolytic copper to the electroless. The solution to this problem is simple: If your electroless copper process cannot stand up to a micro-etch that removes 15–20 microinches, then find one that does. One suggestion is to under- stand the grain structure orientation of the electro- less copper. A tighter, more angular grain structure with well-defined grain boundaries helps mitigate excess electroless copper removal. Another cause often not considered is the incom- plete removal of unexposed dry film. A lower pH in the developer solution usually causes this, or excessive loading of dry film resist in the develop- ing chamber. Use an online real-time controller for the developer to ensure optimum performance and resist residue removal. Also, look for any possibil- ity of overexposure or defects in the phototool that could lead to partial polymerization of the resist in the via. Type 3 ICDs Type 3 ICDs are a horse of a different color. Here, the electroless copper deposit actually separates from itself, known as cohe- sive failure (Figure 2). Copper is deposited in a disorderly fashion. Excessive deposition rates, over-catalyzation, and too high an operating temper- ature are all known causes of this type of ICD. Various conditions of the plating oper- ation prevented the copper deposit from achieving epitax- ial growth. Epitaxial growth is a crystallization process that deposits a new crystal- line layer on a substrate with a specific orientation relative to the substrate's crystal struc- ture, essentially creating an ordered, single-crystal film. This technique produces high- quality, atomically flat layers If the electroless copper deposit is plated at excessive deposition rates or has been over-catalyzed, there is a good chance the deposit will be disoriented, with the copper looking like a sponge. When this happens, the copper will separate from itself, resulting in cohesive failure. Constantly check the deposition rates with coupons. If you detect copper deposit plating at excessive thicknesses, this should be an alarm to check the entire process for the root cause. Summary No matter the defect, brainstorm the various causes with your team so as not to go down a rabbit hole with a misdiagnosed defect. PCB007 Michael Carano brings over 40 years of electronics indus- try experience with special expertise in manufactur- ing, performance chemi- cals, metals, semiconduc- tors, medical devices, and advanced packaging. To read past columns, click here. T RO U B L E I N YO U R TA N K Figure 2: Cohesive failure of the electroless copper. ⊲