Handling Note. [Application] [Contents] SHARP COB Zenigata LED Series

Transcription

1 Handling Note SHARP COB Zenigata LED Series Version: V0.3 March 2013 [Application] This note applies to Sharp s Zenigata COB series of LEDs. In particular the following series: Mega ZENIGATA (20 x 24mm) Mini ZENIGATA (12 x 15mm) Petit ZENIGATA (12 x 8mm) [Contents] 1. Storage Conditions 2. Thermal Considerations 3. Electrical Connectivity 4. LED Handling 5. Operating Temperature 6. Operating Environment 7. Driver Design 8. Other Considerations 9. Safety Precautions

2 [1. Storage Conditions] The solder pad material of standard ZENIGATA LEDs is silver. After opening the aluminium packing bag and exposing the LED to atmospheric conditions it is possible that the solder pad will oxidize or react with corrosive gas. This could lead to difficulties during the soldering process and potentially cause damage to the pad. To avoid such issues it is advisable to keep unused LEDs in the bag with some moisture absorbent material (silica gel) or in a desiccator with controlled temperature and humidity. The following images indicate the change in visual appearance of the pad after oxidation damage: Normal appearance Oxidation damaged [2. Thermal Considerations] Operating a Sharp ZENIGATA LED without an adequate thermal solution will cause damage to the LED. Please always use an appropriately specified heat sink to avoid excessive LED junction temperatures. The size and specification of heat sink required is strongly dependent on the design and operating environment of the final application. Therefore it is up to the customer to determine an appropriate thermal solution. The following information should be considered when designing a thermal solution: Heat sink condition The surface of the heat sink to which the LED will be attached must be flat and free from scratches and debris. Any deformation or damage to the heat sink surface will increase thermal resistance and decrease heat dissipation, potentially leading to over-heating and ultimately failure of the LED. If the surface of the heat sink is not flat (e.g. convex) it may induce cracking of the ceramic substrate which will result in failure of the device. Heat sink installation When mounting LED device on heat sink, use highly thermal conductive adhesive or adhesive sheet. In either case, it is very important to take note of the reliability of heat dissipation and adhesion. If heat dissipation does not occur properly due to detachment of LED device from the heat sink, the temperature of LED device may increase beyond the maximum allowed values leading to device deterioration, lead wire detachments, smoke emission, and other LED device defects. Thermal adhesive selection If opting to use a thermal adhesive to attach the LED to a heat sink please select a product with high thermal conductivity. Reliability tests should be performed before entering mass production, especially for high wattage LEDs such as the Mega-ZENIGATA series. Example products with suitable thermal characteristics: (data provided by adhesive supplier) ST0903 (Silanex Technology) 30 W/m K TIA600R (Momentive Performance Materials) 6 W/m K

3 To ensure good heat dissipation check that the mating surface of the LED and heat sink are clean and that the thickness of the adhesive is controlled to be less than 100um. The adhesive should be spread uniformly across the entire back surface of the LED ceramic substrate. It is recommended that adhesive material is pushed out from every side of the substrate by pressing ZENIGATA LED on the heat sink during the mounting process. Adhesive uniformity If adhesive is not spread uniformly across the back side of the ceramic substrate the LED may be damaged by local heat build-up, even if Tc is controlled within specification. In such cases, local variations in thermal expansion may cause the ceramic substrate to crack. Thermal grease selection If opting to use a thermal grease to make contact between LED and heat sink please select a product with high thermal conductivity. Considerations on thickness and uniformity are the same as for thermal adhesives. Please check lifetime performance of heat dissipation as this may be affected by solidification or other forms of degradation after long periods of use. Thermal sheet selection If opting to use a thermal sheet to make contact between LED and heat sink please select a product with high thermal conductivity and thickness <0.3mm. The entire backside area of ceramic substrate should be attached to the thermal sheet. The thermal sheet should provide good adhesion to both LED and heat sink as if either surface becomes detached it may result in damage to the LED. Reliability of adhesive, grease, thermal sheets The reliability of thermal interface materials should be studied very carefully before mass production. Heat and light may affect the performance of these materials and ZENIGATA LEDs do exhibit some light leakage through the ceramic substrate. Effect of heat sink and other heat dissipation materials on LED device s light output: The light reflectivity efficiency of heat sink and other heat dissipation materials that are used, may affect the light-output of LED device. Therefore it is very important to verify the following factors while designing thermal solutions: 1. Whether the initial reflectivity efficiency values of the above mentioned materials are stable or not. 2. Whether any colour change that occurs due to long term use has an effect on light output 3. Whether the materials emit volatile organic compounds (VOCs) which may degrade the phosphor. 4. Whether the materials emit low molecular weight siloxanes which may degrade the electrical contacts. COB Holder: When using a holder to attach the LED device and heat sink, an appropriate thermal interface material must still be used between the LED and heatsink LED device fixing point: Please avoid using the corners, while deciding the fixing-point for LED device or for the holder fixing design, as there may be salient areas on the corners (edges) of LED device.

4 [3. Electrical Connectivity] Soldered connection Standard ZENIGATA LEDs have been designed for use with soldered electrical connections. Soldering should be performed before the LED is mounted to a heat sink as the increased thermal mass of a heat sink may make it difficult to reach a high enough temperature to melt the solder. The soldering iron tip temperature should be set to 380 degrees Celsius, and the soldering duration should be no longer than 5 seconds per electrode, but be long enough to ensure a high quality connection. If it is not possible to solder before attaching the LED to the heat sink, the soldering tip temperature should be adjusted to ensure a high quality soldered connection. A soldering material with good reliability at elevated temperatures is essential because the LED will go through many temperature cycles during its lifetime. Lower quality materials may experience cracking or creep. The soldering iron should not touch the resin (circular) area of the LED. To avoid damage to this area arrange the soldering process such that the soldering tool approaches the pad from the outside of the LED, as depicted in the diagram below. Other: Please do not attempt to re-solder a detached wire as this may result in a connection with reduced strength. Please ensure that the entire pad is covered in solder. Please arrange wire to not cause mechanical stress to the solder pad. Please study inhabitation of connection by low molecular siloxane which may be generated from grease or other materials. Flow/reflow soldering techniques are note applicable for Zenigata COB LED devices. Non-soldered connection Standard ZENIGATA LEDs have been developed for use with soldered electrical connections and employ a silver electrical contact pad. In case a solder-less electrical connector will be used, a different pad material is available and should be considered depending on the application. [4. LED Handling] Do not touch the coloured resin area of the LED or the white dam ring that surrounds it as there are wire connections underneath. Additional components (holder, lens) should be designed to avoid this area. The handling area for each type of LED is shown below: If pressure is applied to the resin area the following damage may occur:

5 (X-ray inspection) It is recommended to avoid using pointed tools for handling ZENIGATA LEDs. [5. Operating Temperature] The temperature of LED devices should be maintained as per the Tc (case temperature) measured at the measuring point mentioned in the specification, and always use it inside the range of de-rating curve. While measuring Tc, please take care of the following things: The LED device mounting surface should be flat/plain surface. The substrate surface temperature should be uniform. Refer to section 3 for regulations related to soldering temperature and reliabilities. [6. Operating Environment] This product is not designed for use under any of following conditions: A high moisture environment. In briny air or corrosive gas (Cl, H 2 S, NH 3, SO 2, NO X, etc. ). Under direct sunlight (due to photovoltaic effect). Outdoor exposure. Dust. Water, oil, medical fluid or organic solvent. If a customer intends to use a ZENIGATA LED under any of these conditions they will need to confirm performance and reliability for themselves. Do not use component parts containing sulphur (gaskets, adhesives, etc.) Under sunlight When an LED is illuminated under sunlight the photoelectric effect can induce a reverse voltage and damage the device. Please prevent direct and indirect illumination of ZENIGATA LEDs by sunlight

6 The photovoltaic effect is dependent on the properties of the light illuminating a chip and the characteristics of the chip itself. ZENIGATA LEDs are connected in series, meaning the LED chip with the lowest electromotive force (E.M.F) will be affected by the reverse voltage of all LED chips in the series. [7. Driver Design] Please use a driver with built-in surge protection. Design the driver to avoid spikes in current as inrush currents may cause gold contact wires to melt. Do not apply reverse polarity to the LED. When the LED is not in operation avoid applying forward to reverse voltage. LED chips are connected in both series and parallel in ZENIGATA LED. LED voltage will decline with increasing temperature. Do not use constant voltage power supplies as current may increase beyond safe limits. Do not connect ZENIGATA LEDs in parallel. This may lead to high currents passing through those LEDs with the lowest voltages. [8. Other Considerations] To protect from electrostatic damage, please use an antistatic wrist band when handling. Do not use tools and processes which create a large amount of vibration as this may damage the LED. Avoid cleaning, since silicone resin may be eroded by cleaning. To remove any foreign material from the resin surface, please gently wipe using cotton with alcohol. [9. Safety Precautions:] Looking directly at LEDs for a long time may result in hurting your eyes. In the event of excess current (over ratings) being supplied to the device, hazardous phenomena including abnormal heat generation, smoke emission, or fire can be caused. Take appropriate measures to avoid excess current and voltage. Please confirm the safety standards or regulations of application devices. Please be careful with substrate edges, which may injure your hands.