Application Note rev1.0 (New : 4. July. 2014) Samsung Electronics LH351B (3535) Index 1. Introduction Page 1.1 Prologue ………………………………………………………………………………… 3 1.2 Application ……………………………………………………………………………… 4 1.3 Dimension ……………………………………………………………………………… 5 1.4 Feature …………………………………………………………………………………… 6 1.5 Estimation of system performance ……………………………………………… 7 2. Characteristics 2.1 Structure ………………………………………………………………………………… 10 2.2 Thermal resistance …………………………………………………………………… 11 2.3 Electrical characteristics …………………………………………………………… 12 2.4 Luminous flux characteristics …………………………………………………… 13 ………………………………………………………… 14 2.6 Optic characteristics ………………………………………………………………… 16 2.5 Color shift characteristics 3. Module performance 3.1 Current sweep comparison ………………………………………………………… 17 3.2 Temperature sweep comparison ………………………………………………… 18 3.3 Derating curve ………………………………………………………………………… 19 4. Mechanical guidance 4.1 SMT guidance ………………………………………………………………………… 2 20 1.1 Prologue Traditional lighting source have several properties like as inexpensive, light, wide viewing angle, high color rendering index(CRI) and simple structure of space. Due to low efficiency of energy conversion, new light source is start to come out and among them LED is the most popular lighting source of next generation. To meet these market needs, Samsung has made full line-up of LED for illumination. Product family of middle power LED is consist of LM561A/B, LM231A/B, LM362A which is adjust to diffuser optic solution lighting - T8 retrofit tube, flat-panel, lamp. And high power product family of large single chip solution based on ceramic substrate is consist of LH351A/B and LH351Z which is powerful solution at directional illumination - MR, PAR, Torch, Street light – linked with 2nd optic Lens solution. Especially Samsung has system merging solution like as LH934A(AC-LED) merged with power supply unit and LC013B, LC026B, LC040B merged with metal PCB board(COB – Chip on Board) making single LES(light emission size) light source. This application note is focused on LH351B which is very powerful solution for directional illumination and adopted advanced techniques such as hot temperature sorting process and robust chip and white package technology. Detail information, characteristics, performances and useful guidance of LH351B are written on this note. Please be careful these all data and graphs are made for designer reference only, not for any guarantee. Thus it could be changeable without any pre-notification. [ Samsung LED Line-up for illumination ] 3 1.2 Application LH351B is most optimal solution for directional application which require small form factor making easy design to target beam angle and high luminous output including robust reliability. Hot binning technique will help designer to match datasheet value with final results of illumination at real operating condition. • Consumer – Torch light LH351B is convenient light source to collect beam to spot area through reflector. LED structure is suitable for reducing yellow ring effect. • Indoor – MR, PAR, Down light, Spot light One of the major market trend of LED is low-cost. Middle power LED is advantageous in these needs. But there are some barriers to design target beam angle due to large amount of LEDs rather than high power LED. For these reason, LH351Z is optimal solution for low-cost and easy to design directional illumination. • Outdoor – Street Light, Security light, Tunnel light, Parking light, Canopy LH351B has wide operation range(~5Watt) and outstanding reliability performance. With optimum 2nd lens, it is easy to make required beam pattern for street lighting standard. High flux and efficacy help designer to make superior outdoor illumination. • Industry – High bay, Low bay [ Optimal illuminations of LH351Z ] 4 1.3 Dimension Anode (+) LED Zener Diode Cathode (-) [ Electrical circuit diagram ] [ Dimension] 5 1.4 Feature • 3.5 x 3.5 x 1.93 ㎜ • Ceramic substrate LED package • 120˚ viewing angle • JEDEC Level 2a (Precondition) • Up to ±5kV (HBM – ESD) • Hot temperature sorting (Tj 85℃) • Max forward current 1500mA Typical forward current 350mA • Max junction temperature 150℃ • Reliability Test : IES-LM-80-08 qualified Light Phosphor Lens Reflector material Flip - LED chip Zener Diode Wire Cu pad Ceramic substrate [ structure of cross section] LH351B is built of high technology manufacturing process and consists of cutting edge material. To simplify manufacturing process and reduce forward voltage level, LH351B consists of flip-chip solution and to increase ability of color binning supply (MacAdam3step yield), film phosphor technology is adopted. Package structure using reflection material could help to reduce yellow ring phenomenon. The optimum material having fast heat transfer characteristic, reliability, design freedom of electrical pad space and dielectric behavior at once is ceramic material. LH351B also mounted on this ceramic substrate and could have small form factor with 1~5watt operation. To progress optic design (lens, reflector etc,.), designer could get optic raw-file of LH351B from webpage http://www.samsung.com/global/business/led/lighting/component/highpower/overview/259 (ASAP,FRED,LightTools,Photopia,SimuLux,Speos,TracePro,Zemax,RS8). 6 1.5 Estimation of System performance 1.5.1 Flux rank & color binning supply LH351B Luminous Flux Rank 160 P1 150 N1 140 M1 130 K1 120 J3 110 100 J3 J3 J3 J3 J3 0.46 0.44 3500K 0.42 4000K 4500K UM 5000K TM 5700K 0.40 0.38 6500K T0 0.34 0.32 PT U0 V0 3000K 2700K WM VM W0 RT QT 0.28 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50 [ Binning of chromaticity coordinate] 7 6500K (70Ra) 5700K (75Ra) 5700K (70Ra) 5000K (75Ra) 5000K (70Ra) 4000K (80Ra) 4000K (70Ra) E1 Nominal CCT [K} 0.30 H1 F1 F3 0.36 J1 G1 G3 G3 3500K (80Ra) 80 3000K (80Ra) 90 G3 2700K (80Ra) Luminous Flux [lm] 170 1.5.2 Estimation of system performance 1400 140 1200 120 1200 120 1000 100 1000 100 800 80 800 80 600 60 600 60 400 Case1-1 (80%/80%) Case1-2 (85%/85%) Case1-3 (90%/90%) 200 0 40 20 400 200 Typical Case1-1 (80%/80%) 80% 80% 0.6 7 Case1-2 (85%/85%) 85% 85% 0.6 7 Case1-3 (90%/90%) 90% 90% 0.6 7 Range Worst Typical Best Worst Typical Best Worst Typical Best 20 Typical Best lm(H1) / Vf(max) lm(J1) / Vf(typ) lm(K1) / Vf(min) [ Estimation of set output @5000K(70Ra) – 600mA, 7LEDs] PSU Optic current # of efficiency efficiency [A] LEDs 40 0 Worst Best lm(H1) / Vf(max) lm(J1) / Vf(typ) lm(K1) / Vf(min) 351Z Case2-2 (85%/85%) 0 0 Worst Case2-1 (80%/80%) Set efficiency [lm/W] 140 Total flux output [lm] 1400 Set efficiency [lm/W] Total flux output [lm] When designer start to consider illumination, important thing is to choice LED which specification is characteristics, reliability and then performance estimation of final illumination output is important design steps. Indeed estimation of system performance is quite necessary to forecast the range of mass production and these kinds of estimation are closely related with the ability of LED supplying which consist of luminous flux rank, forward voltage bin and chromaticity bin. For example, in case of a certain system condition such as 80% power supply conversion efficiency and 80% optic transmission efficiency, the output performance of illumination could be estimated by the number of LEDs and driven forward current. The expected performance range of mass production is depends on the combination of fine flux rank and voltage binning. Worst case of poor performance could be made by the combination of high voltage bin and low flux rank. At 5000K CCT, 7 LEDs and 600mA driving current per LED, the combination of H1 flux rank and highest voltage could be expected to make 917lm luminous output, 16.7W total power consumption and 54.8lm/W set efficiency. Otherwise best performance could be made by K1 rank and minimum voltage bin at same CCT and operating condition. It could be expected 1083lm luminous output, 18.1W total power consumption and 71.8lm/W set efficiency. Depends on which rank and which binning is used, the output performance could vary. Designer should consider these relations to expect product yield of final set. [ Estimation of set output @5000K(70ra) – 700mA, 6LEDs] Flux Vf lm W lm/W rank rank H1 max 917 16.7 54.8 J1 typ 1000 16.2 61.8 K1 min 1083 15.1 71.8 H1 max 974 15.8 61.8 J1 typ 1063 15.2 69.8 K1 min 1151 14.2 81.1 H1 max 1031 14.9 69.3 J1 typ 1125 14.4 78.2 K1 min 1219 13.4 90.9 351Z [ Case1 - 1,2,3 @600mA, 7LEDs] PSU Optic Current # of efficiency efficiency [A] LEDs Case2-1 (80%/80%) 80% 80% 0.7 6 Case2-2 (85%/85%) 85% 85% 0.7 6 Case2-3 (90%/90%) 90% 90% 0.7 6 Range Worst Typical Best Worst Typical Best Worst Typical Best Flux Vf lm W lm/W rank rank H1 max 883 17 51.9 J1 typ 964 16.5 58.6 K1 min 1044 15.3 73.5 H1 max 939 16 58.6 J1 typ 1024 15.5 66.1 K1 min 1109 144 76.8 H1 max 994 15.1 65.7 J1 typ 1084 14.6 74.1 K1 min 1174 13.6 86.2 [ Case2 - 1,2,3 @700mA, 6LEDs ] 8 1.5.3 Design support Tool In order to expect set performance, through the graph of characteristics, designer needs to find estimated luminous flux and forward voltage of each LED matching with real operating current and solder temperature(Ts). Actually this job does not need high techniques but somewhat inefficient action. In order that designer save development time and get more accuracy expectation, samsung provide design support tool. One is ‘system estimation & compare tool (circle-B)’ and another is ‘color mixing tool (circle-C)’. Circle-B could help designer to estimate LED and system performance at each various operating conditions. Especially in mechanical and reliability aspect, dynamic derating curve and expected lifetime could be shown in accordance with real input current and Ts value. [ circle-B ] Circle-C could help designer to estimate color shift characteristics of LED relating with given driving current, Ts information and also expect final coordinate of color mixing result among several different chromaticity bins. Especially circle-C could be used for manufacturing steps of mass production. Some examples are presented as follows. Center At 25℃, Shifted At 85℃, Shifted Coordinate coordinate coordinate [ color shift on circle-C ] [ color mixing on circle-C ] In case of 5000K R4 bin, center coordinate could be shifted depends on input current and Ts condition. In LH351B, hot bin sorting technique is adopted, therefore coordinate of original bin could be almost same as coordinate of real operating condition, Ts 85℃. In case of 5000K R1, R3 and R4 bin, the expected color mixing coordinate could be shown relating with input number of LEDs , driving current and Ts condition. 9 le ho N-type el ec tro n 2.1 Structure P-type LH351B Lighting Thermal Solder Cu pad (-) Thermal pad Cathod (+) Anode Insulator Metal PCB Al substrate Electrical resistance Thermal resistance Ts (solder temperature point) TJ (junction temperature point) [ Cross section of LED on McPCB] Ts [ Test McPCB of LH351B] Dynamic operating relations with thermal, optical and electrical properties which parameters are forward current, voltage, thermal resistance, solder temperature, phosphor performance and other’s is major unique characteristics of LED. From these complex relation, LED sweep curves doesn’t have simple linear properties. In this application note, more detail sweep curves which have 2nd or 3rd polynomial properties are presented. And surely main curves are based on datasheet. Datasheet of sorting LH351B adopt hot binning condition to be referenced by LED junction temperature (Tj). But actually designer can easily measure Ts which is solder temperature on PCB instead of Tj. Between Tj and Ts surely some differences of electrical and thermal characteristics could be happened due to electrical and thermal resistance. For example, let’s assume 100lm at Tj 85 ℃ on datasheet. Then 100lm should be recognized as same as lower Ts temperature including thermal resistance (Rth j-s). In this application note, Ts temperature is criterion of every information such as graphs and data. 10 2.2 Thermal resistance Normally thermal resistance (Rth) of LED package could be variable depending on temperature and current like as following graph. Especially high power LED (normally over 1watt power consumption) has wider deviation range of thermal resistance rather than middle power or small power LED. This effect is caused by the difference of thermal density and current density versus fixed physical dimension. Thermal resistance (Rth) could be defined variously as like Rth(j-s), Rth(j-a), Rth(s-c) etc,. Rth(j-s) is Rth from LED chip juction to solder point on PCB, Rth(j-a) is junction to ambient. Normally Rth(j-a) is called as thermal resistance of system. Tj (temperature of LED junction) = Ts (temperature of solder) + Rth(j-s) X Power consumption of LED TJ : Junction Temp. PLED : Thermal Source Ceramic (substrate) Solder to PCB PCB Solder Pads PCB Dielectric layer Copper thermal pad RJS : Junction-Solder TS : Solder Temp. RSB : Solder to Board Aluminium Plate TB : Board Temp. Classical TIM to heat-sink RBC : Board to Case TC : Case Temp. RCA : Case to Air Heat Sink TA : Ambient Temp. Tambient : Thermal Ground K factor [ Thermal resistance of LH351B] 4.0 K/W (@350㎃, 25℃) 6.0 K/W (@700㎃, 85℃) Rth (K/W) [ Thermal resistance (Rth j-s) of LH351B] 11 2.3 Electrical characteristics Forward Current (mA) measuring time Even if same measuring time, measured data could be different according to test condition. Data of LH351B datasheet is measured and sorted by pulse testing signal. Testing current Normally illumination development engineer signal wave is interested in data which is measured under continuous wave driving current condition. In [ Pulse measuring (pulse)] [ Continuous wave (CW)] this application note, ‘CW’ means measuring condition under continuous current wave and ‘pulse’ means pulsed signal test condition. 78℃-pulse 1400 LH351B is very powerful 25℃-CW 1200 LED component allowing 50℃-CW Vf driving current until 78℃-CW Solder 1000 1500mA. Due to electrical 100℃-CW Resistance resistance generated 800 from SMT process, IVAluminium Plate curve measured by CW Vf on PCB Board 600 has somewhat incline 400 properties rather than pulse testing. 200 From IV-curve, power consumption could be 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 calculated and the reason why constant Forward Voltage (V) current (C.C) operation is recommended in LED driving could be understood easily. If [Forward current vs. Typical driven by constant voltage(C.V), output forward voltage @Ts] variation versus solder temperature becomes larger than C.C. 3.5 Forward Voltage (V) Forward Current (mA) 1400 1200 1000 800 25℃ 50℃ 78℃ 100℃ 600 400 200 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 3.3 3.1 2.9 25℃ 50℃ 78℃ 100℃ 2.7 2.5 0.0 Power Consumption (W) 1.0 2.0 3.0 4.0 Power Consumption (W) [Forward current vs. Power consumption @Ts] [Forward voltage vs. Power consumption @Ts] 12 5.0 2.4 Luminous flux characteristics (for illumination CCT) Luminous flux is shown as following graphs. Luminous flux at 5000K is higher than 3000K at same power consumption, but relative ratio is similar between each CCT – WM, VM, UM, TM, RJ. From referenced by 25℃ room temperature, relative ratio also presented. 550 400 350 450 300 250 200 150 400 350 300 250 200 150 100 100 50 50 0 200 400 600 800 1000 1200 Forward Current (mA) 0 200 1400 [Luminous flux vs. Forward current @3000K(85Ra) J1 rank] 600 800 1000 1200 Forward Current (mA) 1400 130% 78℃-pulse 25℃-CW 50℃-CW 78℃-CW 100℃-CW 300% 250% 78℃-pulse Normalized Luminous Flux Ratio (%) Relative Luminous Flux Ratio (%) 400 [Luminous flux vs. Forward current @5000K(70Ra) M1 rank] 350% 200% 150% 100% 50% 200 78℃-pulse 25℃-CW 50℃-CW 78℃-CW 100℃-CW 500 Luminous Flux [lm] 450 Luminous Flux [lm] 550 78℃-pulse 25℃-CW 50℃-CW 78℃-CW 100℃-CW 500 400 600 800 1000 1200 Forward Current (mA) [Relative luminous flux ratio vs. Forward current] 50℃-CW 78℃-CW 110% 100℃-CW 100% 90% 80% 70% 200 1400 25℃-CW 120% 400 600 800 1000 Forward Current (mA) 1200 [Relative luminous flux ratio referenced by Ts 25℃] 13 1400 2.5 Color shift characteristics (for illumination CCT) 0.020 0.020 350mA 700mA 0.010 1000mA 0.005 350mA 0.015 Relative chromaticity (△Cy) Relative chromaticity (△Cx) 0.015 0.000 -0.005 -0.010 -0.015 -0.020 700mA 0.010 1000mA 0.005 0.000 -0.005 -0.010 -0.015 -0.020 0 25 50 Ts (℃) 75 100 0 [ Relative chromaticity (△Cx) Vs. Ts @VM 3000K ] 50 Ts (℃) 75 100 [ Relative chromaticity (△Cy) Vs. Ts @VM 3000K ] 0.43 0.42 25 0.414 0.412 V0 0.410 Cy Cy 0.41 25℃ 350mA 0.408 50℃ 0.406 0.40 0.402 1000mA 75℃ 0.404 0.39 700mA 100℃ 0.400 0.38 0.41 0.42 0.43 0.44 Cx 0.45 0.46 [ Color shift @VM 3000K ] 0.424 0.428 Cx 0.432 0.436 [ Color shift @VM 3000K ] 14 2.5 Color shift characteristics (for illumination CCT) 0.020 0.015 350mA 0.010 700mA 1000mA 0.005 0.000 -0.005 -0.010 -0.015 -0.020 0 25 50 75 350mA 0.015 Relative chromaticity (△Cy) Relative chromaticity (△Cx) 0.020 700mA 0.010 1000mA 0.005 0.000 -0.005 -0.010 -0.015 -0.020 0 100 25 50 75 100 Ts (℃) Ts (℃) [ Relative chromaticity (△Cx) Vs. Ts @RJ 5000K ] [ Relative chromaticity (△Cy) Vs. Ts @RJ 5000K ] 0.362 0.38 RJ 0.360 0.37 25℃ 0.358 350mA Cy Cy 0.36 0.35 0.356 50℃ 0.354 700mA 1000mA 75℃ 0.352 0.34 100℃ 0.350 0.33 0.33 0.34 0.35 0.340 0.36 0.344 0.348 0.352 Cx Cx [ Color shift @RJ 5000K ] [ Color shift @RJ 5000K ] 15 2.6 Optic characteristics 3000K V0 (85Ra) 5000K RJ (70Ra) [ Optic diagram of White LED ] Normalized CCT [K] 0.10 0.06 0.04 0.02 0.00 -90 -60 -30 0 30 60 Emission Angle (deg.) -90 -60 -30 0 30 Emission Angle (deg.) 90 [ △u’v’ over angle ] 60 90 [ CCT over angle ] 1.2 Normalized spectrum Delta_u'v' 0.08 7000 6000 5000 4000 3000 2000 1000 0 1.0 1 0 30 0.8 0.6 60 0.5 0.4 0.2 0 380 430 480 530 580 630 680 730 780 Wave length [nm] [ Spectrum ] -90 -60 0.0 -30 0.0 00.0 Emission Angle (deg.) 90 0.5 1.0 Normalized intensity [ CCT over angle ] Optic graphs should be used only for reference. For accurate design, please refer to the linked optic raw-file of LH351B from webpage. http://www.samsung.com/global/business/led/lighting/component/high-power/resource (ASAP,FRED,LightTools,Photopia,SimuLux,Speos,TracePro,Zemax,RS8). 16 3.1 Current sweep comparison For verification of Tool (circle-B) and for testing LH351B, simple experiment is done. Without 2nd optic and power supply unit(PSU), the current sweep performance of assembled module mounting LH351B 6 LEDs, McPCB and heat-sink are measured and then compared with data from Tool at 25℃ Ts condition. LH351B LED cost Flux factor Electrical efficiency 100% Step : LED → CCT → CRI → Bins → IF_current → Input filed CASE A 1 2 3 4 5 6 CCT [K] 5000 CRI [Ra] Optical efficiency 70 100~40 % 100~40 % 100% 100% LED Vf : Min.Typ.Max Bins Flux : J1,K1,M1,N1 LED performances @min/flux_rank IF_driving # Ts Ta [A] of LED [℃] [℃] 0.350 0.500 0.700 1.000 [ Real module test without 2nd optic and PSU ] 6 6 6 6 25 25 25 25 25 25 25 25 VF [V] Flux [㏐] 2.86 2.92 2.99 3.07 159.7 217.5 289.4 386.2 $ /100lm TJ [℃] ∑Flux [㏐] 29.0 30.8 33.4 37.3 958 1305 1736 2317 Sorting IF_driving Typ = 0.350 A Tj_max. = 150 ℃ Sorting Temperat M1 ure = 85 ℃ IF_max. = 1.500 A Estimations of system Derating performance Efficac ∑LES ∑cost Rth(J-a) IF_max. IF_margin ∑Power y Location [W] (A) (A) [㎟] [$] (℃/W) [Lm/W] 6.0 8.8 12.6 18.4 159.4 148.7 138.1 125.9 74 74 74 74 4.0 4.0 4.0 4.0 1.500 1.500 1.500 1.500 1.150 1.000 0.800 0.500 Safe zone Safe zone Safe zone Safe zone [ Current sweep simulation ] Luminous flux output [lm] 2400 2000 measurement 1600 simulation 1200 958lm 800 868lm 400 0 0.2 0.4 0.6 0.8 1 1.2 Forward current [A] Relative luminous flux ratio [%] From the graph of measurement and simulation, two points come to be noticeable. One is that their absolute real data does not equal with each case, another is their deviation ratio is almost same. In case of simulation, deviation parameter is linked with initial starting value which is same value of datasheet. Otherwise, measurement value might need some calibration due to wrong center allocation of DUT(device under test) with integrating sphere and also need to check calibration file of software. Through this simple test, deviation used in Tool might be considered as a quite reliable. And in order to get more exact measuring data, considerable calibration of measuring instrument would be necessary when real measurement. 240% ratio_measurement ratio_simulation 200% 160% 120% 80% 0 0.2 0.4 0.6 0.8 1 1.2 Forward current [A] [ Luminous flux compare @25℃ measurement vs simulation ] [ Relative luminous flux ratio compare @25℃ measurement vs simulation ] 17 3.2 Temperature sweep comparison With same DUT, temperature sweep test is also done. At constant 700mA driving current, output is measured at every 25℃, 40℃, 50℃ and 60℃ which is saturation temperature. And this measured output is compared with simulation result. Similar comparison result comes out like as current sweep test. LH351B LED cost Flux factor Electrical efficiency 100% Step : LED → CCT → CRI → Bins → IF_current → Optical efficiency Input filed CASE A 1 2 3 4 5 6 CCT [K] 5000 70 100~40 % 100~40 % LED 100% Bins 100% LED performances @min/flux_rank CRI IF_driving # Ts Ta [Ra] [A] of LED [℃] [℃] 0.700 0.700 0.700 0.700 [ Real module test without 2nd optic and PSU ] 6 6 6 6 25 40 50 60 25 25 25 25 VF [V] Flux [㏐] 2.99 2.97 2.95 2.94 289.4 279.8 273.5 267.2 $ /100lm Vf : Min.Typ.Max Flux : J1,K1,M1,N1 Sorting IF_driving Typ = 0.350 A Tj_max. = 150 ℃ Sorting Temperat M1 ure = 85 ℃ IF_max. = 1.500 A Estimations of system Derating performance Efficac ∑LES ∑cost Rth(J-a) IF_max. IF_margin y Location (A) (A) [㎟] [$] (℃/W) [Lm/W] Safe zone 12.6 138.1 74 4.0 1.500 0.800 Safe zone 12.5 134.6 74 11.2 1.500 0.800 Safe zone 12.4 132.2 74 16.1 1.500 0.800 Safe zone 12.3 129.8 74 21.0 1.500 0.800 TJ [℃] ∑Flux ∑Power [W] [㏐] 33.4 48.3 58.3 68.2 1736 1679 1641 1603 [ Temperature sweep simulation ] From this temperature sweep test, deviation parameter used in Tool might be considered as a quite reliable. And calibration factor also necessary to match compensation between measurement and simulation. In case of current sweep test, 1.19 calibration factor is calculated and 1.17calibration factor of temperature sweep test is calculated. 105% 1736lm 1600 1549lm 1400 1200 1000 measurement simulation 800 600 0 20 40 60 80 Relative luminous flux ratio [%] Luminous flux output [lm] 1800 Ts. Temperature of solder [℃] 100% 95% 90% ratio_measurement ratio_simulation 85% 80% 0 20 40 60 80 Ts. Temperature of solder [℃] [ Luminous flux compare @700mA measurement vs simulation ] [ Relative luminous flux ratio compare @700mA measurement vs simulation ] 18 3.3 Derating curve [ Derating performance simulation ] With same DUT, Ts becomes 60℃ in saturation time. Tool (circle-B) could supply derating property of system through the graph. From the graph, system thermal resistance (22.7K/W-Rth) and max allowable current (1.0A) could be known at that operating condition. Therefore this operating status is located at ‘safe zone’ with safe margin about Tj and max current. Maximum current [A] [ DUT ] CASE-C.1 CASE-C.1 1.200 1.000 0.800 0.600 0.400 0.200 0.000 0 20 40 60 80 100 120 140 Ta Ambient temperature [℃] [ Derating curve ] [ Derating performance simulation ] If heat-sink thermal capacity is reduced, surely weaker reliability of system could be expected. Actually like as case C.2, solder temperature increase until 120℃. At that point, Tj reaches up to 135.1℃ and allowable max current becomes low as 0.795A. This value is within 10%, therefore status is ‘warning zone’. If Ts more increase and Tj start to over Tj-max(150℃) and allowable current falls down under 0.7A, then status of location would change to ‘out of range’. Maximum current [A] [ DUT ] 1.200 1.000 0.800 0.600 0.400 0.200 0.000 0 20 40 CASE-C.1 CASE-C.2 CASE-C.1 CASE-C.2 60 80 100 120 140 Ta Ambient temperature [℃] [ Derating curve ] 19 4.1 SMT guide Ø 3.1 120˚ 1.09 1.23 Vac. Hole Ø 1 Unit : mm Ø 3.1 Ø 4.0 Ø 4.0 [ The nozzle of pick-up & place tool ] [ Recommended foot-print for SMT ] Solder Mask O X (missalign) X (solderlack) X (solderincline) O X (faultcathode) X (faultcathode) X (missplace) O X (solderlack) X (solderball) Pick & Place After reflow [ Recommended example ] 20 X (thicksolder) Date 2014.7.4 Revision History -. New Version 21 Writer Drawn Approved Y. J. Lee I.H. Choi