10-Watt Lednium SMD
OVTL09LG3x Series
Typical elements in the conducting path and corresponding nominal thermal conductivities are:
Elements
Epilayers
Substrate
Die attach material
Package
Solder
Copper cladding
GaN/InGaN
Sapphire
Conductive epoxy
Silver plated copper
Solder (Sn/Ag/Cu)
Copper
w/mK
150
50
10
350
35
300
Note : Thermal conductivity is a physical constant. For the materials above, the respective contribution each makes
to the overall thermal resistance (Rθ
j-b
) is a function of the thickness of each material layer, and the surface area.
Thermal Conductivity (TC) is defined to be the heat conducted in time (t), through thickness (T) in a direction normal
to a surface area (A), due to a temperature difference (δT).
Therefore
TC= q/t x {T/[A x
δT]}
and
δT
= [Q x T]/[A x TC]
where
δT
= Temp. difference (K)
Q = Power (w)
A = Surface area (m
2
)
T = layer thickness (m)
TC = Thermal Conductivity (w/mK)
Theoretical Calculation (for 1 watt dissipated in a cup product via a single 40mil die)
GaN
Thickness approx 10 x 10
-6
Area 10
-6
T = 60 x 10
-6
T = 20 x 10
-6
A = 2 x 10
-6
T = 0.4x10
-3
A = 6x10
-6
T = 60x10
-6
A = 6x10
-6
= 1 x 10x10
-6
/ 10
-6
x 150
= 0.07 K
= 1 x 60x10
-6
/ 10
-6
x 50
= 1.2 K
= 1 x 20x10
-6
/ 2x10
-6
x 10
=1
= 1 x 0.4x10
-3
/ 6x10
-6
x 350
= 0.19
= 1 x 60x10
-6
/6x10
-6
x 25
= 0.4
Total Calculated
δT
= 2.86K
Substrate
Die attach
Package
Solder
OPTEK reserves the right to make changes at any time in order to improve design and to supply the best product possible.
OPTEK Technology Inc. —
1645 Wallace Drive, Carrollton, Texas 75006
Phone: (972) 323-2200 or (800) 341-4747 FAX: (972) 323-2396 visibleLED@optekinc.com www.optekinc.com
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