A new class of thermoplastic optical polymers made by substantially fully hydrogenating block copolymers of styrene and butadiene, known as cyclic block copolymers (CBCs), were recently discovered to exhibit lead-free solder reflow resistance with peak reflow temperature up to 260°C. This kind of behavior is uncommon for traditional thermoplastic polymers. The block copolymer design and the resulting nanostructured morphology lead to strong elastic and soft solid material characteristics for CBC, which may explain why CBCs can maintain good dimensional stability at high temperatures (i.e., above its glass transition temperature, Tg) for a short period of time such as in a solder reflow process. This hypothesis was examined by computational fluid dynamics modeling on a molded CBC lens of LUXEON K2 LED package configuration. When the CBC lens is subjected to a simulated solder reflow process, the change in physical dimension due to thermal expansion and gravity effects is predicted to be negligible. However, the residual stress in the molded lens may play a profound role on its dimensional stability. There exists a critical stress value below which no observable deformation is predicted for the CBC lens. With excellent optical transparency and good long term optical stability, low moisture absorption, and good injection moldability, CBCs is a promising class of materials for LED packaging that contributes to improved LED manufacturing economics.
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Research Article|
January 01 2010
Thermoplastic Optical Polymers with Lead-Free Solder Reflow Resistance for HB-LED Packaging and Assembly
Weijun Zhou;
Weijun Zhou
*
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
Tel: (979) 238-1347, Email: [email protected]
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Quan Yuan;
Quan Yuan
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
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Chris Li;
Chris Li
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
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Stephen F. Hahn;
Stephen F. Hahn
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
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Kurt A. Koppi;
Kurt A. Koppi
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
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Berend Hoek
Berend Hoek
The Dow Chemical Company, Core R&D – Materials Science & Engineering, 2301 N. Brazosport Blvd., B-1470, Freeport, TX 77541
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International Symposium on Microelectronics (2010) 2010 (1): 000156–000163.
Citation
Weijun Zhou, Quan Yuan, Chris Li, Stephen F. Hahn, Kurt A. Koppi, Berend Hoek; Thermoplastic Optical Polymers with Lead-Free Solder Reflow Resistance for HB-LED Packaging and Assembly. International Symposium on Microelectronics 1 January 2010; 2010 (1): 000156–000163. doi: https://doi.org/10.4071/isom-2010-TA5-Paper4
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