CL-824-U1 参数 Datasheet PDF下载

Thermal Management of CL-824

1. Introduction

The light-emitting element of an LED radiates light and heat according to the input power. However,

the surface area of an LED package is quite small, and the package itself is expected to release little

heat into the atmosphere. An external radiator such as heat sinks is thus required. The heat release

configuration to the connection portion of the external radiator mainly uses heat conduction.

Regarding LED packages, to control the junction temperature of the light-emitting element

Tj

is

important. The

Tj

must be kept from exceeding the absolute maximum rating in the specifications under

any conditions. Because direct measurement of the junction temperature of a light-emitting element

inside a package is seldom possible, the temperature of a particular part on the package outer shell (the

case temperature)

Tc

[deg C] is normally measured.

Tj

[deg C] is calculated from the thermal resistance

between the junction and the case

Rj-c

[deg C/W] and the amount of emitted heat that is nearly equal to

the input power

Pd

[W]. The package structure of the CL-824 series minimizes the thermal resistance

Rj-c

and the heat generated at the light-emitting element can be conducted to the external radiator

efficiently.

This document describes the detailed heat release configuration of the CL-824 series and provides

necessary data for thermal design of lighting apparatus, which leads to optimal utilization of LED

performance.

2. Package configuration and thermal resistance

Fig. 1 (a) illustrates the example of the cross-section structure where the package of the CL-824

series is connected to an external

laminated circuit board. The package

structure is composed of a light-emitting

element mounted on a substrate that

has conductive copper foil patterns and

through holes.

A distinctive point is the heat

generated at the light-emitting element

can be efficiently conducted via through

Fig. 1 (a)

Fig. 1 (b)

holes to the outside of the package.

The electrode section of the package outer shell is electrically conductive and connects via solder to

the electrode on the external circuit board, which also has the function of a heat sink. As described

above, the heat generated in the junction section of the light-emitting element is mainly transferred as

conductive heat from the light-emitting element via element-mount adhesive, through holes, electrodes

on the outer shell, and solder to the external circuit board, which doubles as the heat sink. The thermal

resistance from the junction section of the light-emitting element to the electrode side of the outer shell

is

Rj-c,

which is the specific thermal resistance value of the package. Hence, the following equation

makes sense.

Tj

=

Rj-c

x

Pd

+

Tc

In addition, the thermal resistance of the solder outside of the package is

Rs

[deg C/W], that of the

electrodes with the heat sink function is

Re

[deg C/W], and the ambient temperature is

Ta

[deg C].

Fig. 1 (b) shows the equivalent thermal resistance along the cross-section diagram on Fig. 1 (a). The

thermal resistances

Rj-c, Rs,

and

Re

are connected in series between the junction temperature

Tj

and

the ambient temperature

Ta.

Now the thermal resistances outside the package

Rs

and

Re

can be

integrated into the thermal resistance Rc-a, which leads to the following equation.

Tj

= (Rj-c + Rc-a) x

Pd

+

Ta

Ref.CE-P473 04/09