This application note describes the possible hazards of infrared LEDs (IREDs) used for lamp applications with respect to the IEC-62471 standard and how to classify IREDs according to different risk groups

To achieve reliability and optimal performance of LED Light sources a proper thermal management design is necessary.

Like all electronic components, LEDs have thermal limitations. The allowed operation temperature for the specific lifetime is limited by the glass-point of the LED resin. Usually the maximum permissible junction temperature of common SMT LEDs is in the range of 95 - 125 °C. This means that the temperature of the die inside, doesnít have to exceed this value when exposed to the expected operation temperature. This brief will give the design engineer an introduction in the thermal basic of SMT LEDs.

Furthermore, some concepts are shown in order to improve the thermal design.

In recent years, the brightness of LEDs has continually increased, allowing them to be used in completely new application areas. Due to the strong increase in brightness, the bonded system of chip and housing takes on increased significance. Generally, the lifetime of an LED is not due to the actual semiconductor chip itself, but primarily determined by the housing. The “lifetime“ refers to the period of time, whereby the brightness drops to half of its original value at a specific current. In order to achieve a lifetime in the range of 100,000 hours at room temperature for very bright LEDs, Osram has implemented a new sealing compound consisting of silicone.

Various cleaning methods for LEDs are described in this Application Note: Dry cleaning. wet cleaning, ultrasonic cleaning.

In addition to a brief fundamental consideration of the manual lead-free and lead-containing soldering process, this application note describes the essential influencing factors and their effect on the lead-free soldering process.

Furthermore, the basic rules and specific guidelines associated with the new manual lead-free soldering process are illustrated.

Also, possible risks are discussed and the general procedure of the lead-free soldering process is described.

In conclusion an overview of the solderability of the various LED types from OSRAM Opto Semiconductors are presented, along with their ability to be reworked and repaired.

As LEDs become more efficient and more compact their sensitivity to ESD events is also increasing in the majority of cases. Despite a great deal of effort in the semiconductor industry in the past decade, ESD still affects production yields, manufacturing costs, product quality, product reliability, and profitability of all semiconductor devices, including LEDs.

OSRAM MIDLEDs are high powered devices in very small SMT packages. The devices are produced using MID (Molded Interconnected Device) Technology.

They are manufactured using dual component molding with the surface being partially metalized. An integrated reflector yields high radiant intensity without the use of lenses. The die is casted with silicone to ensure high temperature stability. The package can be placed as either toplooker or sidelooker.

This application note describes the handling of MIDLED s (silicone casted devices) and describes their unique radiation characteristics.

This application note shows how radial and SMT LEDs can be processed, from the initial tape or reel to the soldering process.

Temperature measurement generally can be divided into two main categories - contact thermometry and radiation thermometry. Contact thermometry consists of a thermocouple which always remains in contact with the device under test, while radiation thermometry measures the radiation of the device under test without contact, by means of an infrared sensor. In order to guarantee a long lifetime for LEDs, the junction temperature must not be exceeded. The maximum junction temperature is specified in the data sheet for the LED.

This application note provides information about measurement procedures, the thermocouples used and their systematic errors as well as the ways in which thermocouples are mounted.

SMT Replaces Through Hole Technology.

The use of SMT-TOPLED varies greatly from the use of traditional through hole LEDs. Historically through hole LEDs have been incorporated directly into front panels using the leads as a stand off. Due to the automated nature of SMT assembly, and the size constraints of SMT components and assemblies, SMT-TOPLED applications are different from through hole applications.

What is Surface Mounting? In conventional board assembly technology the component leads are inserted into holes through the PC board and connected to the solder pads by wave soldering on the reverse side (through-hole assembly). In hybrid circuits (thick and thin film circuits) ìchipsî, i.e. Ieadless components, are reflow soldered onto the ceramic or glass substrate in addition to the components already integrated on the substrate. Surface mounting evolved from these two techniques.