application note light emitting diode this sheet contains tentative information, we may change contents without notice. (SP-QR-C-1841A) oct. 3, 2013 heat dissipation from nc4 u13xx depending on tj hs-a hs-b hs-c t s point figure 2 copper board figure 1 ts measuring point front side reverse surface hs-a hs-b hs-c front side reverse surface figure 3 copper board & heat sink 1. objective the light output of leds is reduced under the influence of heat generation. when leds ar e operated over the absolute maximum junction temperature (t jmax ), the performance is severely degraded. it is critical to design the heat dissipation not to exceed the t jmax for nc4u13xx to achieve a high reliability and a hi gh performance. this document provides the tj evaluation results under three conditions by using different heat sinks. please use the data as reference for nc4u13xx?s thermal design at your site. 2. tj calculation tj can be obtained by the following formula: tj = ts + rthj-s p d where, tj: junction temperature [c] ts: soldering temperature [c] rthj-s: thermal resistance between the led die and the ts measuring point [c/w] * the rthj-s of nc4u13xx is ty p:1.7 [c/w] (max:2.2 [c/w] ) p d : input power [w] 3. tj measurement result ex.1 copper board + heat sink a i f (a) t s ( )v f (v) t j ( ) 0.3 70 13.3 77 0.5 93 13.5 104 0.7 117 13.7 133 ex.2 copper board + heat sink b i f (a) t s ( )v f (v) t j ( ) 0.3 53 13.4 60 0.5 67 13.7 79 0.7 79 14.0 96 ex.3 copper board + heat sink c i f (a) t s ( )v f (v) t j ( ) 0.3 51 13.4 58 0.5 64 13.7 76 0.7 77 14.0 94 4. heat dissipation materials - metal-based board; copper, dimension; 30mm 30mm 1.7mm - heat sink a: 30mm 30mm h=20mm, depth: 4mm, fin; 64 pcs. (dimension of fin; 1mm 2mm, structure; 8 8) - heat sink b: 50mm 38mm h=25mm, depth; 5mm, fin; 8 pcs. (dimension of fin; 1mm 38mm, structure; 1 8 - heat sink c: 54mm 54mm h=35mm, depth; 4mm, fin; 64p cs. (dimension of fin: 0.8mm 9mm and structure; 5 13) note: absolute maximum ratings nichia specifies the absolute maximum ratings for nc4u13xx as i f =0.7a and t jmax =130c. we cannot assure the performance of the leds if they are us ed above the specified temperature and i f . thank you very much for your cooperation.
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