Electronics Assembly Knowledge, Vision & Wisdom
Selective Removal of Conformal Coatings by Pulsed Ultraviolet Lasers
Selective Removal of Conformal Coatings by Pulsed Ultraviolet Lasers
To miniaturize electronics conformal coating removal solution needs to provide fine cut resolutions, witout compromising quality, cost, and throughput.
Production Floor

Authored By:
Cristian Porneala, Joshua Schoenly, Xiangyang Song, Rouzbeh Sarrafi, Dana Sercel, Sean Dennigan, and Marco Mendes
IPG Photonics Corporation
Manchester, NH, USA
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Summary
Within the microelectronics and medical device industries, thin conformal Parylene coatings are deposited on sensitive components in order to offer protection from, and biocompatibility within, a wide variety of environments. Oftentimes these coatings need to be removed from select areas to provide access to underlying circuit components. As electronic devices continue to miniaturize any conformal coating removal solution needs to provide even finer cut resolutions, all while not compromising quality, cost, and throughput demands. Pulsed ultraviolet (UV) laser machining offers a high-precision, high-throughput solution with no compromise on quality.
Conclusions
Short pulse ns UV lasers can selectively remove conformal Parylene coatings with a dimensional precision that cannot be achieved using alternate techniques, while allowing for high throughput. When all system functions are considered (e.g., beam formation and delivery, vision alignment, part fixturing and movement and integrated metrology), a production tool can be delivered with the level of scalability and process traceability necessary when removing conformal coatings on today's most critical electronic and medical devices.

While the choice of laser depends on the exact application requirements a new generation of UV fiber lasers offers unique advantages vs. standard bulk solid state lasers. For example, constant pulse duration over the full range of pulse energy and repetition rate, which allows for very easy process scalability. The short 1.5 ns pulse duration of the ULPN fiber lasers at 355 nm allows for unique Parylene removal approaches. A laser lift off removal process is possible at low fluence (~ 0.2 J/cm2), while higher fluences (≥ 0.7 J/cm2) allow for ablative high quality removal. In
addition these lasers maintain the typical advantages of fiber lasers such as compactness, high wall-plug efficiency, cost effectiveness, and robustness which makes them highly suitable for high volume manufacturing.
Initially Published in the SMTA Proceedings
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