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February 2017 • The PCB Magazine 85 So it is somewhat obvious that excellent plat- ing adhesion to the substrate is necessary for a circuit that will experience potentially many flex- ures over the course of its life. In addition, low to no stress in the copper deposit is preferred. It is important to keep in mind that adhesion of a thin film to a substrate is a complex mechanism. Internal deposit stress is just one factor. Addi- tional factors affecting adhesion are: • Ionic bonding between two surfaces • Adsorption: adhesion is based on interatomic and intermolecular interactions such as van der Waals and perhaps Lewis Acid interactions • Mechanical interlocking The last bullet point depends on the contri- bution from a roughened surface. In the case of flexible polyimide, a roughened topography is not achievable. With respect to flexible polyimide, opti- mum adhesion of the electroless copper deposit is heavily dependent on internal deposit stress and adsorption of the palladium catalyst to a plasma desmear treated surface. Please keep these factors in mind when troubleshooting an adhesion issue. PCB Michael Carano is VP of Technol- ogy and Business Development at RBP Chemical Technology. To read past columns or to contact Carano, click here. Figure 3: Spiral contractometer for measuring internal stress in the plated deposit. METALIZING DIFFICULT-TO-PLATE SUBSTRATES Manufacturing is undergoing the fourth industrial revolution (Industry 4.0), an era where we see new technologies and tech- niques transforming the systems and processes of our factories. Automation, IoT, analytics, and ro- botics, to name a few, are among the advances and strategies that electronics assem- blers must embrace to improve their manufacturing performance, lower labor costs and create smarter factories. Electronics manufacturers are beginning to consider investing in new systems to take their pro - cesses to the next level. In a recent I-Connect007 sur- vey on the topic of new technolo- gy, the top reasons cited by man- ufacturers to invest in new tech- nologies are to increase efficiency, improve yield, reduce cycle time, and the advance capability of the process. Adopting new technologies involves a heavy capital investment, but surprisingly, the majority of the respondents considered the capabilities of these systems as the most important factor when buying new equipment. Read more here. I-Connect007 Survey: Investing in New Technologies