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88 The PCB Magazine • July 2014 wedge between the B-stage material and the ox- ide (or oxide alternative). The wedge defect thus can act as a via allowing acid chemicals to seep in, removing some of the treated copper foil coating leading to the appearance of pink ring. Stay tuned for more on these manufacturing interactions in a future column. Process Flow the alternative bonding process is easily im- plemented as an immersion system or in hori- zontal conveyorized mode. Equipment consid- erations are minimal and capital expenditure is within the realm of the majority of pwb fabri- cators. Let's look at a more detailed view of the process flow: The recommended process flows and dwell times for the immersion (vertical) and horizon- tal (conveyorized) processes are listed below: Figure 3: etchback leading to wedge between pre-preg B stage and treated copper foil. Immersion Horizontal acid cleaner 180 sec 30 sec rinse 60 sec 45 sec Pre-dip 60 sec 45 sec coating step 60 sec 40 sec rinse 60 sec 20 sec dry 300 sec 30 sec OXIDE ALTERNATIvE PROCESSES: PERFORMANCE CHARACTERISTICS continues

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