Abstract
In this paper we report epoxy molding compound lead frames (EMC-LFs) with encapsulated silicone as a simple and inexpensive packaging for AlGaN-based ultraviolet-B (UVB) light-emitting diodes (LEDs) displaying high light extracting efficiencies (LEE) and long operation lifetimes. The convex surfaces and beveled shapes obtained after curing the encapsulated silicone surrounding the UVB-LED chips significantly enhanced the light output power (LOP). With silicone present inside the EMC-LFs having bonding cavity diameters of 1.7 and 1.45 mm, the LOPs of the UVB-LEDs improved by 26 and 42%, respectively; reliability tests performed over a period of 1000 h revealed, however, that the LOPs decreased to 70 and 71%, respectively, of their initial values, but no cracks appeared in the silicone during such long-term operation. Thus, the stability of silicone-encapsulating EMC-LFs for UVB-LEDs was acceptable. When compared with AlN-based direct plating copper ceramic lead frames (AlN-DPC-LFs), our proposed packaging structure and method have the potential to lower the manufacturing cost of UVB-LEDs.
Highlights
III-Nitride–based deep-ultraviolet (DUV) light-emitting diodes (LEDs) have a wide range of applications
Significant enhancements in the light output power (LOP) occurred for samples A1, A2, and A3 after encapsulation (26, 42, and 14%, respectively), presumably because of lower degrees of total internal reflection (TIR) after decreasing the refractive index (n) gap between the UVB-LED chip and air (n = 1) by encapsulating silicone inside the cavity [30]
In conclusion, with comparison to the conventional method by using AlN-DPC-LFs, we report that encapsulating silicone in epoxy molding compound lead frames (EMC-LFs) appears to be a simple and inexpensive packaging technology that can increase the light extracting efficiencies (LEE) and operation lifetimes of AlGaN-based UVB-LEDs
Summary
III-Nitride–based deep-ultraviolet (DUV) light-emitting diodes (LEDs) have a wide range of applications. We developed an inexpensive and highly durable packaging structure, using reliable silicone as the encapsulation material, to improve the LEEs of UVB-LEDs. Compared with AlN-DPC-LFs, the use of such EMC-LFs has the potential to decrease the cost of manufacturing UVBLEDs. II.
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