SP-QR-C-4089A Datasheet, PDF (1/2 Pages) NICHIA CORPORATION – Tj Control for Good Heat Dissipation in NVSU233A (U405)

Application Note
Tj Control for Good Heat Dissipation in NVSU233A (U405)
1. Objective
The LEDs’ light output can be affected by the heat generated from the LEDs/LED-assembled products.
Also, the reliability performance can be seriously degraded, if the LEDs are operated over the absolute
maximum rated junction temperature (Tj).
It is critical to design the heat dissipation performance not to exceed the T_jmax for NVSU233A, to deliver high
reliability/performance.
This document shows the Tj evaluation results by demonstrating two heat dissipation conditions. Please use
the data for reference to your thermal design.
2. Tj Calculation
Tj can be calculated by the following formula:
Tj = Ts + Rthj-s × P_D
Tj: Junction Temperature
Ts: Soldering Temperature (°C)
Rthj-s: Thermal resistance (°C/W) from the die to the Ts measuring point
* Rthj-s (NVSU233A): 5.7°C/W
PD: Input Power (W)
3. Ts Measuring Point
TS Point
Picture 1 Ts Measuring Point
The thermocouple was solder-attached to
the Ts measuring point for the evaluation.
4. Tj Evaluation Result
Example 1. Copper Board + Heat Sink B
I_F(A)
1.0
1.4
T_S (℃)
48.2
58.6
V_F(V)
3.4
3.5
T_j (℃)
68
87
Example 2. Copper Board + Heat Sink C
I_F(A)
1.0
1.4
T_S (℃)
43.6
51.9
V_F(V)
3.4
3.5
T_j (℃)
63
80
Front Side
Reve　rse Side
Picture 2 Copper Board
HS-B
HS-C
Front Side
HS-B
HS-C
Reverse Side
Picture 3 Copper Board + Heat Sink
This sheet contains tentative information; we may change the contents without notice.
(SP-QR-C-4089A)
Oct. 14, 2014