Authored By:
Raanan Novik, Orbotech Inc.
Billerica, MA
Summary
Printed circuit board manufacturers are continually challenged to fabricate denser solder mask patterns with smaller features to accommodate advanced electronic components. This trend is motivating manufacturers to adopt novel methods to achieve the required solder mask designs. One such method is direct imaging, which utilizes a controlled light source to directly expose the design image onto photosensitive solder mask material. Another method, termed herein direct jetting, uses inkjet printing to direct deposit jettable solder mask ink onto the circuit surface per the designed pattern. Both methods enable manufacturers to achieve fine solder mask features and circuit design registration with tight tolerances. The implementation of these methods in production requires testing and parameter setup as prerequisites, to ensure that the quality criteria are met, and the production process remains robust. This paper details the recommended steps to carry out such testing, included dedicated test vehicle designs that reduce the time and production resources required, while providing valuable data critical to defining process parameters and capabilities. The derived data is analyzed and compared with predefined performance criteria requirements to determine the optimal parameters that should be implemented in actual production.
Conclusions
In this paper, we reviewed the two distinct technologies used for processing SM on printed circuit boards: (1) direct imaging of the SM pattern used to expose photoimageable ink, and (2) direct jetting (additive inkjet printing) of the SM pattern using jettable ink. The operational concepts of these technologies were described along with the underlying parameters that dictate the produced result. It guides an engineer potentially introducing these technologies into a production process on how to carry out efficient and beneficial testing to derive data that can be used to implement such technologies reliably.
For both DI and DJ, a three-step approach was outlined, covering preparation, implementation and analysis. The preparation step is used to plan out the variable parameters, both for process conditions and materials, as well as the testing to be performed. Recommended test vehicle designs were introduced for each method to allow for multiple test variations to be implemented using relatively few panels. These test designs aimed to reduce the time and production resources required, while providing valuable data critical to determining the optimal parameters that should be implemented in actual production. The implementation step is carried out per the devised test plan, considering the resources required and the testing criteria. The implementation step is completed by the collection and organization of the processing variables and the correlating test results. In the third and final analysis stage, the collected data is referenced to the quality requirements as laid out in the preparation step. Those conditions that yielded the results that best satisfy the required performance criteria should be chosen for further investigation and process setup.
Initially Published in the SMTA Proceedings
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