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AB174 Datasheet(PDF) 8 Page - Lumileds Lighting Company |
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AB174 Datasheet(HTML) 8 Page - Lumileds Lighting Company |
8 / 10 page AB174 LUXEON 5050 Application Brief 20170507 ©2017 Lumileds Holding B.V. All rights reserved. 8 5.6 JEDEC Moisture Sensitivity The JEDEC moisture sensitivity level (MSL) for this LUXEON emitter is rated as level 3. Proper storage, handling and/or baking guidelines must be observed to prevent damage to the LUXEON emitter during reflow (see Table 2). Table 2. Storage and baking conditions. Note that if any of the temperature, relative humidity, humidity indicator card or the periodisnotmet,bakingisrequired.Formoreinformation,seeIPC/JEDECJ-STD-033C. OpErATION pAckINg bAg sTATUs TEMpErATUrE rELATIvE hUMIdITy (rh) hUMIdITy INdIcATOr cArd pErIOd Storage As received ≤30°C (non-condensing atmospheric environment) ≤90% n/a Within 12 months of shipment date code Storage After opening bag ≤30°C ≤60% If 60% color spot is no longer blue 168 hours Baking (drying) n/a 60 ±5°C ≤5% n/a 16 hours 6. Packaging Considerations—Chemical Compatibility The LUXEON emitter package contains a silicone overcoat to protect the LED chip and extract the maximum amount of light. As with most silicones used in LED optics, care must be taken to prevent any incompatible chemicals from directly or indirectly reacting with the silicone. The silicone overcoat used in the LUXEON emitter is gas permeable. Consequently, oxygen and volatile organic compound (VOC) gas molecules can diffuse into the silicone overcoat. VOCs may originate from adhesives, solder fluxes, conformal coating materials, potting materials and even some of the inks that are used to print the PCBs. Some VOCs and chemicals react with silicone and produce discoloration and surface damage. Other VOCs do not chemically react with the silicone material directly but diffuse into the silicone and oxidize during the presence of heat or light. Regardless of the physical mechanism, both cases may affect the total LED light output. Since silicone permeability increases with temperature, more VOCs may diffuse into and/or evaporate out from the silicone. Careful consideration must be given to whether LUXEON emitters are enclosed in an “air tight” environment or not. In an “air tight” environment, some VOCs that were introduced during assembly may permeate and remain in the silicone. Under heat and “blue” light, VOCs captured inside the silicone may partially oxidize and create a silicone discoloration, particularly on the surface of the LED where the flux energy is the highest. In an air rich or “open” air environment, VOCs have a chance to leave the area (driven by the normal air flow). Transferring the devices which were discolored in the enclosed environment back to “open” air may allow the oxidized VOCs to diffuse out of the silicone and may restore the original optical properties of the LED. Determining suitable threshold limits for the presence of VOCs is very difficult since these limits depend on the type of enclosure used to house the LEDs and the operating temperatures. Also, some VOCs can photo-degrade over time. Table 3 provides a list of commonly used chemicals that should be avoided as they may react with the silicone material. Note that Lumileds does not warrant that this list is exhaustive since it is impossible to determine all chemicals that may affect LED performance. The chemicals in Table 3 are typically not directly used in the final products that are built around LUXEON emitters. However, some of these chemicals may be used in intermediate manufacturing steps (e.g. cleaning agents). Consequently, trace amounts of these chemicals may remain on (sub) components, such heat sinks. Lumileds, therefore, recommends the following precautions when designing your application: – When designing secondary lenses to be used over an LED, provide a sufficiently large air-pocket and allow for “ventilation” of this air away from the immediate vicinity of the LED. – Use mechanical means of attaching lenses and circuit boards as much as possible. When using adhesives, potting compounds and coatings, carefully analyze its material composition and do thorough testing of the entire fixture under High Temperature over Life (HTOL) conditions. |
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