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luxeon z assembly and handling information introduction this application brief addresses the recommended assembly and handling procedures for luxeon z emitters. proper assembly, handling, and thermal management, as outlined in this application brief, ensure high optical output and long lumen maintenance for luxeon z emitters. scope the assembly and handling guidelines in this application brief apply to the following products: luxeon z white (all cct & cri) luxeon z royal blue (lxz1-pr01) luxeon z lime (lxz1-px01) luxeon z deep red (lxz1-pa01) luxeon z green (lxz1-pm01) luxeon z red (lxz1-pd01) luxeon z cyan (lxz1-pe01) luxeon z red-orange (lxz1-ph01) luxeon z blue (lxz1-pb01) luxeon z amber (lxz1-pl01) in the remainder of this document the term luxeon z refers to any product in the luxeon z product family. illumination AB105 luxeon z application brief ?2017 lumileds holding b.v. all rights reserved.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 2 table of contents introduction 1 scope 1 1 component 3 1.1 description .......................................................................... 3 1.2 optical center ....................................................................... 4 1.3 handling precautions ................................................................. 4 1.4 cleaning ............................................................................ 5 1.5 electrical isolation .................................................................... 5 1.6 mechanical files ...................................................................... 5 1.7 soldering ............................................................................ 5 2 printed circuit board design 6 2.1 footprint and land pattern ............................................................ 6 2.2 surface finishing ..................................................................... 6 2.3 minimum spacing .................................................................... 6 3 thermal measurement guidelines 7 4 assembly process guidelines 8 4.1 stencil design ........................................................................ 8 4.2 pick-and-place ....................................................................... 8 4.3 refow accuracy ..................................................................... 11 5 packaging considerations C chemical compatibility 12 about lumileds 14
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 3 1. component 1.1 description the luxeon z emitter is an ultra-compact, surface mount, high-power direct color or white led. each luxeon z emitter consists of a high brightness ingan or alingap led chip on a ceramic substrate. the ceramic substrate provides mechanical support and provides a thermal path from the led chip to the bottom of the emitter. an interconnect layer electrically connects the led chip to cathode and anode pads of equal size on the bottom of the ceramic substrate. the cathode of the luxeon z emitter is marked with a small notch in the center of the electrode (see figure 1). the top of the luxeon z is covered with a thin layer of silicone to shield the chip from the environment. the bottom of the luxeon z emitter contains two equally sized metallization pads for the anode and cathode. all ingan luxeon z emitters contain a transient voltage suppressor (tvs) chip which protects the led chip against electrostatic discharge (esd) events. the tvs chip creates some minor topographical variations across the top surface of the ingan luxeon z emitters; all alingap luxeon z emitters have a fat top surface. the luxeon z emitter comes in four diferent form-factors, depending on the targeted color (see table 1 and figure 2): table 1. summary of various luxeon z colors, chip technology, phosphor and nominal height of the light emitting area. figure 1. 3d renditions of luxeon z with ingan chip (left & center) and alingap chip (right).
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 4 figure 2. the luxeon z emitter comes in four diferent form fact ors, depending on the targeted color. all dimensions in mm. 1.2 optical center the theoretical optical center of the luxeon z emitter is 0.625mm from the top and 0.650mm from the side edges of the ceramic substrate (see figure 3). 1.3 handling precautions the luxeon z emitter is designed to maximize light output and reliability. however, improper handling of the emitter may gdpdhwkh/(fklsdgdhfwwkhrhudooshuirupdfhdguholdelolwrughuwrpllpl]hwkhulvnrigdpdhwrwkh/( chip during handling, luxeon z emitters should only be picked up manually from the side of the ceramic substrate as shown in figure 4. figure 3. the optical center of the luxeon z emitter is 0.625mm from the top and 0.650mm from the side edges.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 5 figure 4. correct handling (top) and incorrect handling (bottom) of luxeon z emitters. when handling fnished boards containing luxeon z emitters, do not touch the top surface with any fngers (see figure 5a) or apply any pressure to it. also, do no turn over the board for probing, if the electrodes are at the back of the board, or stack multiple boards on top of each other (see figure 5b). a rough or contaminated surface, which is placed on top of a luxeon z emitter, may damage the silicone overcoat of the emitter. furthermore, any pressure applied onto the luxeon z emitter during probing may damage the silicone layer or the chip underneath. 1.4 cleaning the luxeon z emitter should not be exposed to dust and debris. excessive dust and debris may cause a drastic decrease in optical output. in the event that the surface of a luxeon z emitter requires cleaning, a compressed gas duster at a distance of 6 away will be sufcient to remove the dust and debris or an air gun with 20 psi (at nozzle) from a distance of 6. make sure the parts are secured frst. 1.5 electrical isolation the luxeon z emitter contains only two electrical pads on the bottom of the ceramic substrate with a spacing of 0.25mm between them. in order to avoid any electrical shocks and/or damage to the luxeon z emitter, each design needs to comply with the appropriate standards of safety and isolation distances, known as clearance and creepage distances, respectively (e.g. iec60950, clause 2.10.4). 1.6 mechanical files mechanical drawings for luxeon z (2d and 3d) are available upon request. 1.7 soldering luxeon z emitters are designed to be soldered onto a printed circuit board (pcb). for detailed assembly instructions, see section 2. substrate as shown in figure 4. figure 5. do not touch the top of surface of the luxeon z emitt er when handling a fnished board (a) or stack boards with one or more luxeon z emitters on top of each other (b).
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 6 figure 6. recommended pcb footprint for luxeon z. sr denotes solder resist opening and sp denotes stencil pattern. all dimensions in mm. 2. printed circuit board design the luxeon z emitter is designed to be soldered onto a metal core pcb (mcpcb) or a multi-layer fr4 pcb. to ensure optimal operation of the luxeon z emitter, the pcb should be designed to minimize the overall thermal resistance between the led package and the heat sink. 2.1 footprint and land pattern the luxeon z emitter has two pads that need to be soldered onto corresponding pads on a pcb to ensure proper electrical operation. figure 6 shows the minimum footprint design for a single luxeon z emitter in an application where multiple luxeon z emitters are placed in a densely packed array, with each emitter electrically addressable. the electrical pads of the luxeon z emitter also serve as thermal pads between the led and the pcb. to enhance heat dissipation from the luxeon z emitter into the pcb, it is best to extend the copper area around each electrode approximately 4mm from the center of the luxeon z emitter, where possible. furthermore, it is desirable to keep the thermal resistance values of the two copper pads on the pcb underneath each luxeon z emitter approximately equal to ensure a balanced heat transfer from the luxeon z emitter through both electrodes. figure 7 shows an example of a densely packed 2x2 luxeon z array on a metal core starboard. the spacing between the four luxeon z emitters (labeled d1 through d4) is 0.2mm. the pink areas in the drawing represent solder mask openings while the white dotted lines correspond to the outlines of the four luxeon z packages. the drawing of this starboard is available upon request. 2.2 surface finishing lumileds recommends using a high temperature organic solderability preservative (osp) on the copper layer. 2.3 minimum spacing lumileds recommends a minimum edge to edge spacing between luxeon z emitters of 0.2mm. placing multiple luxeon z emitters too close to each other may adversely impact the ability of the pcb to dissipate the heat from the emitters. also, the light output for each led may drop due to optical absorption by adjacent led packages.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 7 figure 7. a closely packed 2x2 luxeon z array confguration on a metal core pcb (left). zoomed-in image of four luxeon z red (alingap) emitters mounted on the board (right). t he pads marked with the dashed circles correspond to the preferred t s measurement points for this confguration. 3. thermal measurement guidelines this section provides general guidelines on how to determine the junction temperature of a luxeon z emitter in a stand-alone or array confguration in order to verify that the junction temperature in the actual application during regular operation does not exceed the maximum allowable temperature specifed in the datasheet. the typical thermal resistance r j-thermal pad between the junction and the thermal pad for luxeon z is specifed in the luxeon z datasheet. in luxeon z, both the electrode pads serve as thermal pads. with this information, the junction temperature t j can be determined according to the following equation: t j = t thermal pad + r j-thermal pad ? p electrical in this equation p electrical is the electrical power going into the luxeon z emitter and t thermal pad is the temperature at the bottom of one of the luxeon z electrodes, assuming both luxeon z electrodes are connected to copper pads on the pcb with approximately the same thermal resistance. in typical applications it may be difcult, though, to measure the thermal pad temperature t thermal pad directly. therefore, a practical way to determine the luxeon z junction temperature is by measuring the temperature t s of a predetermined sensor pad on the pcb right next to the luxeon z emitter with a thermocouple. to ensure accurate readings, the thermocouple must make direct contact with the copper of the pcb onto which the luxeon z electrode pads are soldered, i.e. any solder mask or other masking layer must be frst removed before mounting the thermocouple onto the pcb. the luxeon z emitter is ideally suited for applications where multiple color leds need to be placed in a closely packed array confguration. to mimic this scenario, lumileds built a 2x2 densely packed array confguration (see figure 7). given the asymmetry in the copper pads on the pcb, there are several candidate sensor pad locations around the 2x2 array confguration. the most appropriate t s point depends, to a large extent, on the type of luxeon z emitters used and the operating conditions of the emitter array. the following guidelines help determine the most appropriate t s location in a densely packed array application in order to approximate the maximum junction temperature in the luxeon z emitter array: a. if there is no symmetry in the copper layout of the pcb, it is best to place the t s point next to the electrical pad (anode or cathode) where lateral heat spreading into the pcb is most impeded. this is typically the electrode with the least amount of copper. for example, in the closely packed 4-up confguration of figure 7, the circular pads on the d1-, d2+, d3- and d4+ electrodes are preferred.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 8 b. if multiple luxeon z emitters of the same color are used, select the pad next to the luxeon z emitter with the highest nominal forward voltage (v f ). c. if a mixture of ingan and alingap luxeon z emitters is operated at approximately the same drive current, it is preferred to measure the pad temperature of the luxeon z alingap emitter with the lowest wavelength and the luxeon z ingan emitter with the highest wavelength. in this ranking according to wavelength, a luxeon z white emitter falls somewhere between a luxeon z royal blue and luxeon z cyan emitter. the highest observed temperature should then be used to approximate the junction temperature. d. if diferent drive currents are used for each luxeon z emitter, it is generally best to measure the temperature next to the luxeon z emitter which consumes the most amount of electrical power. the thermal resistance r j-s between the luxeon z junction and t s point was experimentally determined to be approximately 5k/w for a densely packed 2x2 array of luxeon z emitters of the same color on a 1.0mm thick al-mcpcb board (1oz copper with 4 mil thick arlon 92ml dielectric layer). the spacing between the luxeon z emitters was 200m. during these thermal measurements all four luxeon z emitters were powered to take into account any thermal crowding efects due to the close packing of the emitters. the junction temperature can then be calculated as follows: t j = t s + 5 ? p electrical_array (assuming all 4 leds are powered) in this equation p electrical_array is the combined electrical power going into the four luxeon z emitters. the r j-s will typically be a bit lower if: ? the spacing between luxeon z emitters is increased ? the thickness of the top copper foil of the pcb is increased ? the thickness of the dielectric layer between the top copper foil and metal core is decreased ? the thermal conductivity of the dielectric material is increased. the thermal resistance r j-s between the junction of a single (powered) luxeon z emitter and t s point on the same 4-up board confguration of figure 7 was experimentally determined to be 18k/w. the junction temperature for the single luxeon z emitter can then be calculated as follows: t j = t s + 18 ? p electrical (assuming a single emitter is powered only) led board confgurations with a larger number of closely packed luxeon z emitters may require additional thermal modeling to determine the pad temperature of those luxeon z emitters in the center of the array which are not easily accessible. 4. assembly process guidelines 4.1 stencil design the appropriate stencil design for the luxeon z emitter is included in the pcb footprint design (see figure 6). the recommended stencil thickness is 125m. the slightly smaller stencil pattern, compared to the solder resist opening, prevents the solder paste from accidentally bridging between the electrodes, which are only spaced 250m apart. 4.2 pick-and-place automated pick and place equipment provides the best handling and placement accuracy for luxeon z emitters. figure 8 and figure 9 show two pick and place nozzle designs and corresponding machine settings which were successfully used for the various luxeon z confgurations with pick and place equipment from yamaha (yv100x) and juki (ke2080l).
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 9 based on these pick and place experiments, lumileds advises customers to take the following general pick and place guidelines into account: 1. for luxeon z ingan emitters, the tip of the nozzle should be positioned on the fat surface above the led chip area; the area around the tvs should be avoided because of the height diferences (see figure 10). there is no such constraint on the nozzle position for luxeon z alingap emitters. 2. the nozzle tip should be clean and free of any particles since this may interact with the silicone coating of the luxeon z package during pick and place. 3. during setup and any initial production runs, it is a good practice to inspect the top surface of the luxeon z emitters under a microscope to ensure the emitters are not accidentally damaged by the pick and place nozzle. pick and mount information vision information pick timer 0s alignment group special mount timer 0s alignment type odd.chip pick height alignment module fore & back & las ingan (white) [1] 0.28mm light selection main + coax ingan lime [1] 0.18mm lighting level 5/8 ingan (direct color) [1] 0.30mm comp. threshold 91 alingap [1] 0.19mm comp. tolerance 15 mount height 0mm search area 1.5mm mount action normal comp. intensity n/a mount speed 100% auto threshold not used pickup speed 100% vacuum check normal chk pick vacuum 20% mount vacuum ingan 60% alingap 90% notes: 1. luxeon z alingap product family uses deeper emitter pocket tape depth (1.15mm) than luxeon z ingan product family (0.88mm). figure 8. pick and place nozzle design and corresponding machin e settings for yamaha yv100x in combination with the of-the-shelf nozzle 7wa. note that some of the machine settings are unique to each luxeon z confguration.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 10 pick and mount information vision information xy fast2 centering method laser pick depth 0mm comp shape corner square picking stroke 0mm pick z down fast2 pick z up fast2 placing stroke 0mm place z down fast2 place z up fast2 theta (measure) fast theta (other) fast figure 9. pick and place nozzle design and corresponding machin e settings for juki ke2080l in combination with the of-the-shelf nozzle 502. these machine settings were successfully used for all luxeon z confgurations.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 11 figure 10. nozzle pick-up location for luxeon z (ingan ) emitters. note that pick and place nozzles are customer specifc and are typically machined to ft specifc pick and place tools. also, the pick and place machine settings in this application brief are typical values and should be used as a starting point to fne tune the actual pick and place process of interest. finally, some pick and place machines may have additional hidden parameters, and when used with the nozzle design as described here, can afect the overall performance. sometimes a customized nozzle such as the one shown in figure 11 to prevent luxeon emitter from getting stuck on the nozzle tip during pick and place process may be needed. lumileds recommends that customer contact their pick and place manufacturer for additional nozzle support. since the luxeon z emitter has no primary optics or lens which can act as a mechanical enclosure protection for the led chip, the pick-up and placement force applied to the top of the package should be kept to a minimum. this is particularly important for luxeon z ingan direct color and luxeon z white emitters in which the silicone layer (with phosphor for white emitters) is about 25m and 50m thick, respectively. the luxeon z alingap emitters, in contrast, have a much thicker silicone layer and luxeon z ingan lime emitters have hard phosphor platelet and are therefore, able to absorb higher forces. experimental studies with various pick and place machines confrmed that luxeon z emitters can be reliably picked from tape and placed onto a pcb with a placement force 30grams. note that this placement force, consisting of impact force and dwell force (also known as static force), depends on the nozzle tip material, nozzle spring stifness, nozzle diameter, vacuum pressure, over travel distance, pcb height diferences and pcb warping. figure 11. an example of a custom nozzle with vacuum relief not ches to minimize luxeon z emitter from getting stuck to the nozzle tip during pick and place process. shown here is a nozzle designed by panasonic (p/n qubs40209220-assy) for panasonic pick and place machine. the nozzle tip inner diam eter is 0.70 mm and outer diameter 1.00 mm with relief notches of 0.25 mm wide as shown. note that the vacuum relief notch does not necessarily have to be a triangular shape as long as the edges are rounded of to prevent surface damage. further, the size and the number of notches may need to be optimized for specifc sticky condition. 4.3 refow accuracy using the solder resist and stencil pattern layout as shown in figure 6, lumileds has determined the placement accuracy after refow to be within a standard deviation of 24m in the x and y direction. for a small and lightweight package like luxeon z, the surface tension of liquid solder is typically sufcient to realign the luxeon z package to the nominal position of the footprint layout as demonstrated in figure 12.
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 12 5. packaging considerationschemical compatibility the luxeon z package contains a silicone overcoat to protect the led chip. 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 in luxeon z is gas permeable. consequently, oxygen and volatile organic compound (voc) gas molecules can difuse into the silicone overcoat. vocs may originate from adhesives, solder fuxes, 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 difuse into the silicone and oxidize during the presence of heat or light. regardless of the physical mechanism, both cases may afect the total led light output. since silicone permeability increases with temperature, more vocs may difuse into and/or evaporate out from the silicone. careful consideration must be given to whether luxeon z 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 overcoat. under heat and blue light, the vocs inside the silicone overcoat may partially oxidize and create a silicone discoloration, particularly on the surface of the led where the fux 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 fow). transferring the devices which were discolored in the enclosed environment back to open air may allow the oxidized vocs to difuse out of the silicone overcoat and may restore the original optical properties of the led. figure 12. luxeon z self alignment before (left) and after refow (right).
AB105 luxeon z application brief 20171214 ?2017 lumileds holding b.v. all rights reserved. 13 rohs compliant determining suitable threshold limits for the presence of vocs is very difcult 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 2 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 afect led performance. the chemicals in table 2 are typically not directly used in the fnal products that are built around luxeon z leds. 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 as heat sinks. lumileds, therefore, recommends the following precautions when designing your application: ? when designing secondary lenses to be used over an led, provide a sufciently 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 fxture under high temperature over life (htol) conditions. table 2. list of commonly used chemicals that will damage the silicone overcoat of luxeon z. avoid using any of these chemicals in the housing that contains the led package. chemical name normally used as hydrochloric acid acid sulfuric acid acid nitric acid acid acetic acid acid sodium hydroxide alkali potassium hydroxide alkali ammonia alkali mek (methyl ethyl ketone) solvent mibk (methyl isobutyl ketone) solvent toluene solvent xylene solvent benzene solvent gasoline solvent mineral spirits solvent dichloromethane solvent tetracholorometane solvent castor oil oil lard oil linseed oil oil petroleum oil silicone oil oil halogenated hydrocarbons (containing f, cl, br elements) misc. rosin flux solder flux acrylic tape adhesive
?2017 lumileds holding b.v. all rights reserved. luxeon is a registered trademark of the lumileds holding b.v. in the united states and other countries. lumileds com neither lumileds holding b.v. nor its afliates shall be liable for any kind of loss of data or any other damages, direct, indirect or consequential, resulting from the use of the provided information and data. although lumileds holding b.v. and/or its afliates have attempted to provide the most accurate information and data, the materials and services information and data are provided as is, and nei ther lumileds holding b.v. nor its afliates warrants or guarantees the contents and correctness of the provided information and data. lumileds holding b.v. and its afliates reserve the right to make changes without notice. you as user agree to this disclaimer and user agree - ment with the download or use of the provided materials, information and data. a listing of lumileds product/ patent coverage may be accessed at lumileds com/patents. about lumileds companies developing automotive, mobile, iot and illumination lighting applications need a partner who can collaborate with them to push the boundaries of light. with over 100 years of inventions and industry frsts, lumileds is a global lighting solutions company that helps customers around the world deliver diferentiated solutions to gain and maintain a competitive edge. as the inventor of xenon technology, a pioneer in halogen lighting and the leader in high performance leds, lumileds builds innovation, quality and reliability into its technology, products and every customer engagement. together with its customers, lumileds is making the world safer, better and more beautifulwith light. to learn more about our lighting solutions, visit lumileds.com . AB105 luxeon z application brief 20171214

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