Thermal Management for XP and MX XLAMP LEDs

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To discuss the thermal management for the XP and MX families of XLamp LEDs

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Thermal Management for XP and MX XLAMP LEDs

  1. 1. Thermal Management for XP and MX XLAMP LEDs <ul><li>Source: Cree </li></ul>
  2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>To discuss the thermal management for the XP and MX families of XLamp LEDs </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>MX and XP XLamp LEDs overview </li></ul></ul><ul><ul><li>Cree LEDs’ thermal characteristics </li></ul></ul><ul><ul><li>Cree solution for using FR-4 PCB to disspipate heat </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>12 Pages </li></ul></ul>
  3. 3. High Power LED Advantages No issues starting in cold environments Low-temperature-friendly Enables new lighting fixtures and energy-saving techniques Infinitely controllable Contains no mercury, lead or other heavy metals Environmentally friendly Reaches full brightness in nanoseconds Instant on No filament to break Inherently rugged 70% lumen maintenance; up to 50,000 hours Extremely long lifetime No wasted light; any pattern possible Directional No compromise between efficacy and CRI High-quality light Available up to 130 lumens/watt and still increasing Very energy efficient
  4. 4. MX Series XLamp ® LEDs <ul><li>Available in white (2,600 K to 8,300 K CCT) </li></ul><ul><li>Maximum drive current: 350 mA </li></ul><ul><li>Wide viewing angle: 120° </li></ul><ul><li>Electrically neutral thermal path </li></ul><ul><li>Qualification at max drive current </li></ul><ul><li>RoHS-compliant </li></ul><ul><li>Unlimited floor life at ≤ 30°C/85% RH </li></ul>
  5. 5. XP Series XLamp ® LEDs <ul><li>High flux output in all whites and colors </li></ul><ul><li>Symmetrical package </li></ul><ul><li>Unlimited floor life at <= 30 º C/85% RH </li></ul><ul><li>Electrically-isolated thermal path </li></ul>Cool white, white, Neutral white, Warm white, Royal blue, Blue, Green, Amber, Red-orange, Red Cool white, Outdoor white, Neutral white, Warm white, Royal blue, Blue, Green, Amber, Red-orange, Red Cool white, Outdoor white, Neutral white, Warm white Color 3.45mm x 3.45mm 3.45mm x 3.45mm 3.45mm x 3.45mm Package Size 110 º 115 º 125 º Viewing Angle 500 mA 700 mA 1500 mA Max Current XP-C XP-E XP-G
  6. 6. Temperature Influence Increasing forward current, increases flux Higher forward current, increases Vf & power Higher power dissipation raises Tj and reduces light output Flux Vf Flux
  7. 7. General Guidelines for Thermal Management <ul><li>Minimizing the amount of heat that needs to be removed </li></ul><ul><ul><li>Separate the LED drive circuitry from the LED board </li></ul></ul><ul><li>Minimizing the ambient temperature inside the fixture </li></ul><ul><li>Enhancing thermal conductivity between the heat sinks and the LED </li></ul><ul><li>The orientation of the LED PCB/heat sink should be considered carefully </li></ul>
  8. 8. XLamp Thermal Characteristics <ul><li>Lighting-class LEDs are designed for high temp operation </li></ul><ul><li>Rth <20 ºC/W typical </li></ul><ul><li>Lamp can stay within data sheet parameters with good thermal design </li></ul>
  9. 9. Adding Thermal Vias for FR-4 PCB <ul><li>FR-4 is one of the most commonly used PCB materials. </li></ul><ul><li>FR-4 has very low thermal conductivity. </li></ul><ul><li>An inexpensive way to improve thermal transfer for FR-4 PCBs is to add thermal vias. </li></ul><ul><li>Adding vias in an appropriate way will improve the thermal resistance of an FR-4 board. </li></ul>Top layer Cu FR4 Dielectric Bottom layer Cu Thermal pad Solder mask HASL Heat Source FR-4 cross-sectional geometry Thermal vias
  10. 10. Thermal Simulations <ul><li>To achieve the lower thermal resistance for an FR-4 board, the dielectric thickness should be reduced. </li></ul><ul><li>Larger vias diameters will reduce thermal resistance. </li></ul><ul><li>Adding additional vias will reduce more thermal resistance. </li></ul>Thermal resistance for FR-4 PCB with no vias with varying thermal pad size Length/Width of top trace (mm) Thermal Resistance ( ºC/W ) 0.8mm thick FR4 no Vias 1.6mm thick FR4 no Vias Via Diameter (mm) Thermal Resistance ( ºC/W ) 70 60 50 40 30 20 10 30 25 20 15 10 5 FR-4 PCB with various via diameters and numbers of vias
  11. 11. Recommended Board Layout <ul><li>To achieve the lowest possible thermal resistance for an FR-4 board, the dielectric thickness should be reduced to 0.8mm. </li></ul><ul><li>While making the vias as large as possible will reduce thermal resistance, the cost of manufacturing the board needs to also be taken into consideration. </li></ul><ul><li>Larger unfilled vias introduce the possibility of voids or gaps in the materials which might fill the vias. Smaller, solid filled vias are a better solution. </li></ul><ul><li>Adding additional vias and increasing the width of the thermal pad beyond a certain point have diminishing returns because of thermal spreading resistance. </li></ul>Cree recommends creating areas of 10-mil (0.254 mm) vias set up on a rectilinear grid of 25 mil (0.635 mm).
  12. 12. Additional Resource <ul><li>For ordering XP & MX XLamp LEDs, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http://www.cree.com/products/xlamp_docs.asp </li></ul></ul><ul><li>Visit Element 14 to post your question </li></ul><ul><ul><li> www.element-14.com </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>

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