VISHAY SEMICONDUCTORS LEDs Application Note Little Star Specification, Handling, Thermal Management and Design-In Product Specification The datasheet presents the performance for the Little Star in tables and diagrams. Brightness group and color are already defined in the device type name. More details as VF group and color group, production date can be seen on the label. 20783 A 20784 Introduction B 20613 C A) Type of component B) Manufacturing plant C) SEL - selection code (bin): e.g.: DA = code for luminous intensity group 5 = code for color group 4 = code for forward voltage D) Batch: 200707 = year 2007, week 07 PH19 = plant code E) Total quantity For any questions, contact: [email protected] Fig. 1 - Design of the Label APPLICATION NOTE The Little Star package is designed for high current application up to 400 mA, with a super high flux output and presented in a compact package outline. (6.0 x 6.0 x 1.5). With its low package height of 1.5 mm it presents the best combination of compactness and highest brightness. The following application note details product specification in corresponding data sheets for the different series of the product. The InGaN based devices are casted with silicone. Silicone casting has big advantages in terms of optical stability and stress relief, but requires a special handling procedure in assembly. For the solder process there is no special requirement. The device is compatible to the existing SMT processes and standard IR-reflow. Manual solder process is only accepted for engineering purposes and de-soldering for failure analysis. Special conditions are recommended to avoid thermal damage. Optical parameters especially for InGaN based devices are strongly temperature dependent. As a summary beside the handling recommendation a proper thermal management of is the most important part for the design in of high power LED. Driving the LED a high portion of the electrical energy will be converted to heat. This heat conducts from the junction area through the LED die, then trough the package and finally to the ambient via the heatsink. The following application note describes all this phenomena in detail and gives the necessary instructions for a efficient application and a long LED life time. Document Number: 81897 Revision: 1.0, 01-Jul-08 D E www.vishay.com 1 Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In LUMINOUS INTENSITY/FLUX CLASSIFICATION RED/AMBER/YELLOW LUMINOUS FLUX ΦV (MLM) CORRELATION TABLE LUMINOUS INTENSITY IV (mcd) GROUP STANDARD MIN. MAX. MIN. MAX. AA 7150 9000 20 700 26 100 AB 9000 11 250 26 100 33 000 AC 11 250 14 000 33 000 39 000 AD 14 000 18 000 39 000 52 000 AE 18 000 22 400 52 000 71 000 AF 22 400 28 500 71 000 97 000 Note: Luminous intensity is tested at a current pulse duration of 25 ms and an accuracy of ± 11 %. The above type numbers represent the order groups which include only a few brightness groups. Only one group will be shipped on each reel (there will be no mixing of two groups on each reel). In order to ensure availability, single brightness groups will not be orderable. In a similar manner for colors where wavelength groups are measured and binned, single wavelength groups will be shipped in any one reel. In order to ensure availability, single wavelength groups will not be orderable. COLOR CLASSIFICATION DOM. WAVELENGTH (nm) GROUP DOM. WAVELENGTH (nm) YELLOW AMBER MIN. MAX. MIN. MAX. A 585 588 610 616 B 588 591 616 620 C 591 594 D 594 597 Note: Wavelengths are tested at a current pulse duration of 25 ms and an accuracy of ± 1 nm. FORWARD VOLTAGE CLASSIFICATION FORWARD VOLTAGE (V) GROUP MIN. MAX. 02 2.2 2.5 03 2.5 2.8 Note: Forward voltages are tested at a current pulse duration of 25 ms and a tolerance of ± 0.05 V. In order to ensure availability, a single forward voltage group can not be ordered. Fig. 2 - Classification Table for brightness, Color and VF C B Y3 A Y3 Y3 X3 X2 0.49 0.47 0.45 0.43 0.41 0.39 0.37 0.35 0.33 0.31 0.29 X1 0.27 0.48 0.46 0.44 0.42 0.40 0.38 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.25 Cy APPLICATION NOTE Handling Procedure Chromaticity Coordinate Groups for Warm White SMD LED Cx Fig. 3 - Color Grouping on White and Warm-White www.vishay.com 2 The Little star package is, as all platic packages, humidity sensitive. The Jedec level 2a is specified. This means the floortime is 672 h in an environment of 10 °C to 30 °C and humidity < 60 % RH. After more than 672 h under these conditions moisture content will be too high for reflow soldering. In case of moisture absorption, the devices will recover to the former condition by drying under the following condition: 192 h at 40 °C + 5 °C/- 0 °C and < 5 % RH (dry air/nitrogen) or 96 h at 60 °C + 5 °C and < 5 % RH for all device containers or 24 h at 100 °C + 5 °C not suitable for reel or tubes. For any questions, contact: [email protected] Document Number: 81897 Revision: 1.0, 01-Jul-08 Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In AlInGaP based devices as red, amber and yellow are casted with clear resin. There is no special requirement for mechhanical handling. For InGan based devices, especially for the white silicone is used as encapsulant. The advantage of silicone is the thermal and photo stability in a variety of harsch environment. This features minimize the risk of yellowing or changing in physical properties during device operation. As a result of the advantages of a silicone encapsulant the lifetime of the LED can be increased up to 100 kh. On the other side silicone is much softer compared to epoxy resin. Thus, when handling the LED, care should be taken not to apply excessive pressure on top of the silicone. Sharp objects might pierce through the silicone encapsulant and damage the LED. When handling the LED using tweezers, care should be taken to ensure that the tweezers would not be in contact with the silicone surface to prevent scratches on the lens. The right way to pick or place the LED using tweezers from the side of the package as shown in Fig. 4. Fig. 5 - Acceptable Foreign Particle Level on a Silicone Casted LED Optical and Electrical Charactersistics Across Operation Temperature Range The optical and electrical characteristic of a power LED depends strongly on the junction temperature. The forward voltage decreases while the dominant wavelengths increases with the temperature, as shown in fig. 6 to 8 for AlInGaP and InGaN based devices. Rel. VF vs. Ambient Temperature IF = 400 mA 1.5 1.4 1.3 VF rel red 1.2 amber 1.1 yellow 1.0 0.9 0.8 - 40 - 20 Fig. 4 - Requirement for Manual Handling Document Number: 81897 Revision: 1.0, 01-Jul-08 25 50 100 Fig. 6 - VF over Temperature for AllnGaP Based Devices Rel. LD vs. Ambient Temperature IF = 400mA 10 8 yellow 6 LD/nm 4 red 2 0 -2 -4 -6 amber -8 - 10 - 40 - 20 0 25 50 100 Temperature (°C) Fig. 7 - Dominant Wavelength vs. Ambient Temperature For any questions, contact: [email protected] www.vishay.com 3 APPLICATION NOTE For SMT mounting, the pick and place nozzle use must be bigger than the LED emission area, to prevent the LED from sticking to the pick and place nozzle. Parameter settings for pick and place process should also be evaluated to ensure no damage to the LED's. If cleaning is required after soldering, we suggest to use IPA as cleaning agent. Maximum recommended rinsing time is 10 s. No use of ultrasonic to avoid damages during cleaning. Due to the silicone is soft in nature; the tendency of foreign particulate to adhere on the silicone surface would be greater compared to epoxy resin. A certain amount of particles can be accepted without influencing the performance of the LED. Typical contamination in an acceptable range is shown in fig. 5 0 Temperature (°C) Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In Change of x/y vs. Ambient Temperature White IF = 350 mA Rel. Iv vs. Ambient Temperature IF = 400 mA 2.5 0.05 0.04 yellow 2.0 0.03 0.02 dx/dy amber lv rel 1.5 red 0.01 0.00 - 0.01 1.0 - 0.02 - 0.03 0.5 - 0.04 0.0 - 0.05 - 40 - 20 0 25 50 100 - 40 - 20 Fig. 8 - Relative Luminous Intensity vs. Ambient Temperature 1.15 1.10 VF rel 1.05 1.00 0.95 0.90 0.85 - 20 0 25 50 100 Temperature (°C) Fig. 9 - VF vs. Ambient Temperature for White Rel. Luminous Intesity vs. Ambient Temperature White IF = 350 mA Rel. Iv vs. Forward Current 1.8 1.6 1.0 1.4 0.9 1.2 lv rel lv rel 1.1 APPLICATION NOTE 0.8 0.7 red amber yellow 1.0 0.8 0.6 0.6 0.4 0.2 - 40 - 20 0 25 50 100 Temperature (°C) 0.0 0 Fig. 10 - Relative Luminous Intensity vs. Ambient Temperature for White www.vishay.com 4 100 The dominant wavelength is a function of the junction temperature and therefore also a function of the forward current applied to the LED due to a part of energy converted to heat. The typical relationship between the forward current change versus the wavelengths or CxCy shift is shown in fig. 13, 15. For unique illumination of an area the individual device is driven by different brightness and therefore with different current. This will shift the dominant wavelengths and therefore also the color. In applications where this shift can not be tolerated, pulse width modulation (PWM) should be used to dim the brightness. The frequency of PWM should be above 200 Hz, so that the human eye can not follow the on/off cycle. The colour shift can be avoided by PWM (fig. 16). 1.2 0.5 50 Dimming the Little Star 1.20 - 40 25 Fig. 11 - Color Coordinates x, y vs. Ambient Temperature Rel.VF vs. Ambient Temperature White IF = 350 mA 0.80 0 Temperature (°C) Temperature (°C) 200 400 600 800 1000 IF (mA) Fig. 12 - LOP vs. Forward Current For any questions, contact: [email protected] Document Number: 81897 Revision: 1.0, 01-Jul-08 Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In Relative Luminous Intensity IVrel vs. Duty Cycle Rel. LD vs. Forward Current 4.0 1.2 3.0 1.0 2.0 amber LD (nm) 1.0 0.8 red Iv rel 0.0 0.6 - 1.0 yellow 0.4 - 2.0 - 3.0 0.2 - 4.0 0 200 400 600 800 1000 IF (mA) Fig. 13 - Dominant Wavelength vs. Forward Current 0.0 0 20 40 60 80 Duty Cycle (%) 100 120 Fig. 16 - Relative Luminous Intensity vs. Duty Cycle Rel. Luminous Intensity vs. Forward Current White Thermal Management 2.5 Driving an LED part of the power is converted to light. The major part of the energy is converted to heat. This heat generated at the PN junction has to be transferred out of the LED through the package to the PCB and from there to the local ambient as shown in fig. 17 and 18. 2.0 lv rel 1.5 1.0 0.5 0.0 0 200 400 600 800 1000 IF (mA) Fig. 14 - White: Luminous Intensity vs. Forward Current Change of x, y vs. Forward Current White 0.010 0.008 Fig. 17 - The Way the Heat Goes out of the LED via Leadframe to 0.006 the PCB dx, dy (ccd) 0.004 0.002 0.000 - 0.002 - 0.004 - 0.008 - 0.010 0 200 400 600 800 1000 IF (mA) Fig. 15 - White: X, Y vs. Forward Current Fig. 18 - The Thermal Resistance Rthja as a Summary of Individual Parts Document Number: 81897 Revision: 1.0, 01-Jul-08 For any questions, contact: [email protected] www.vishay.com 5 APPLICATION NOTE - 0.006 Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In The heat transfer out of the system described in fig 17 is following "Ohm's Thermal Law" (1) Tj = LED junction temperature Ta = Ambient temperature Rthja = Thermal resistance junction to ambient VF = Forward voltage 90 Thermal Resistance (K/W) Tj = Ta + Rthja x (VF x IF) 100 IF = Forward current 80 70 60 50 40 Rthja (°C/W) 30 20 Rthjs (°C/W) 10 Out of the summary of individual parts to total thermal resistance 0 0 1000 2000 3000 4000 5000 MC PCB Size (mm x mm) Rthja = Rthjs + Rthsa (2) Fig. 20 - Effect of Heat sink size on Rthjs and Rthja Rthjs = Thermal resistance junction to solder point Solder Requirements Rthsa = Thermal resistance solder point to ambient From "ohm's thermal law" Tj - Ts = Rthjs x (VF x IF) (3) or Tj = Rthjs x (VF x IF) + Ts (4) Ts = Solder temperature Equation (4) is particular important in practical calculation to ensure under specific operating condition, the junction temperature will not exceed absolute maximum Tj rating defined in the datasheet. The Ts can be measured by soldering a thermocouple to the solder-point. Theoretically the thermal resistance junction to solder point is solely a function of the component package. In practical the junction to solder point resistance will vary with the different cooling environment. Measurements are shown in fig. 19 and 20. The soldering surfaces are plated 100 % pure Sn. The component is designed to be compatible to the existing industry SMT process and IR-reflow. There are no special processes or equipment required for the mounting of the components in different applications. Both the thermal and electrical connections are provided by the conventional process. Therefore, there is no need to provide for additional process or material to take care for the thermal connection. However, due to the unique design, all the soldering terminals are located at the bottom surface of the component. This greatly reduces the space required and also enhances the thermal dissipation capability of the component. Heat from the LED chip is directly conducted via the soldering terminals to the external environment. Thermal path is kept to the very minimum. As for the soldering process, the component is qualified for both Pb and lead (Pb)-free soldering profile. Both profiles as described in the datasheet are applicable. 140 948625 300 max. 240 °C 10 s ca. 230 °C 250 100 Temperature (°C) Temperature (°C) APPLICATION NOTE 120 80 Tj at 350 mA (°C) 60 40 215 °C 150 max 40 s max. 160 °C 100 90 s to 120 s Ts at 350 mA (°C) 20 200 Lead Temperature 50 Full Line: Typical Dotted: Process Limits 2 K/s to 4 K/s 0 0 0 1000 2000 3000 4000 5000 0 50 100 150 200 250 Time (s) MC PCB Size (mm x mm) Fig. 19 - The Effect of Heat Sink Size on Junction and Solder Point Fig. 21 - Recommended Lead (Pb)-free IR-reflow Profile for Temperature Lead (Pb)-free Soldering www.vishay.com 6 For any questions, contact: [email protected] Document Number: 81897 Revision: 1.0, 01-Jul-08 Application Note Little Star Vishay Semiconductors Specification, Handling, Thermal Management and Design-In Manual Soldering IR Reflow Soldering Profile for Lead (Pb)-free Soldering Preconditioning acc. to JEDEC Level 2a 300 Temperature (°C) max. 260 °C 245 °C 255 °C 240 °C 217 °C 250 200 The device is not released for manual solder process due to undefined heat load. Therefore manual solder or de-solder process should be limited to failure analysis and R & D applications. max. 30 s 150 max. 100 s max. 120 s 100 max. ramp up 3 °C/s 50 max. ramp down 6 °C/s 0 0 50 19885 100 150 Time (s) 200 250 300 max. 2 cycles allowed Fig. 22 - Recommended SnPb IR-reflow Soldering Profile APPLICATION NOTE Document Number: 81897 Revision: 1.0, 01-Jul-08 For any questions, contact: [email protected] www.vishay.com 7