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1、,SSR/Heat Sink Assembly Design,Product Presentation,GN SERIES SOLID STATE RELAYS,Return to Main Menu,Innovation In Solid State Technology,Ratings to 125 Amps/660 Vac,Direct Bond Copper Substrate,Improved Power Lead Frame Design,Surface Mount Technology,Cast Base Plate,EMC Compliant(Level 3),Larger S
2、CR Die,Optional IP20 Touch Safe Housing,UL/cUL/CSA Recognized,TUV Approved,CE Compliant,Internal Transient Protection,Input Status LED Indicator,Features,Objectives,Develop a solid state relay that utilizes the latest technology and has as many features as possible incorporated into the initial desi
3、gn.,Design a back-to-back SCR assembly with a thermal efficiency that is significantly better than our competitions relays.,Achieve level 3 compliance with all of the standards set forth by theEuropean Communities EMC Directive.,Automate the assembly line to increase reliability and to reducemanufac
4、turing time.,Develop and implement automated test procedures that verify theintegrity and functionality of the SSR.,All of these objectives were met before the GN SSRs were introducedinto the market.,Competetive Analysis,YesNoNoNoNoNoNoYesNo,NoNoNoNoNoNoYesYesNo,Thermal Efficiency,Heat is the primar
5、y cause of SSR failures in most applications.As current flows through the relay,the SCRs generate heat which must be dissipated through the ceramic substrate,through the base plate,and into the heat sink.The heat sink is then cooled by the ambient air.The SSRs ability to function reliably in an appl
6、ication is dependent upon how well it can transfer heat from the SCR die to the heat sink.If the SSR is not very efficient in transferring heat through the base plate,then the size of the heat sink must be increased to compensate for this or the relay and/or load may be damaged.,SSR thermal efficien
7、cy is measured in degrees Celsius per watt being generated by the SCRs,or Rjb.The lower the SSRs Rjb rating,the more efficient it is.Rjb is determined by the type of ceramic substrate used,the thickness of the ceramic,and how well the SCR die and substrate are assembled.,Direct Bond Copper(also know
8、n as Direct Copper Bonding or Fused Copper)has a much lower thermal impedance than traditional foil substrates.The ceramic and copper are heated and pressed to form a“bond”which minimizes the thermal barrier between the traces and the substrate.The GN series SSRs also utilize a substrate that is 40%
9、thinner than traditional ceramic substrates,making the SSR even more efficient.,Direct Bond Copper,GN SERIES SOLID STATE RELAYS,“Bussed”Power Lead Frame,Direct Bond CopperSubstrate,Cast Base Plate,Reliability,GN SERIES SOLID STATE RELAYS,Regulated AC&DC Inputs,VDE ApprovedOptical-Isolators,Internal
10、Transient Protection,Electrical transients,voltage and current surges,electrostatic discharges,conducted and radiated interference,and line voltage fluctuations,are all phenomena that frequently occur in industrial and commercial environments.Placing a product on the market that will operate normall
11、y in this type of environment is essential for reliability.,The GN Series SSRs have been designed and evaluated for compliance with level 3 requirements of the European Unions EMC Directive.This has resulted in a relay with enhanced reliability that can facilitate an OEMs evaluation for EMC complian
12、ce.It also eliminates the need for external transient protection,such as MOVs.,Electromagnetic Compatability,Applications,Virtually any manufacturer of electrical equipment switching current in excess of 1 amp may utilize solid state relays.,SSR Selection,GN SCR Assembly v.Traditional SCR Assembly,G
13、N PCB Assembly v.Traditional PCB Assembly,Heat Sinks&Custom Assemblies,HS-3 1.5C/W Heat Sink,Single Phase SSRs,HS-4 1.0C/W Heat Sink,Single Phase SSRs,HS-7 0.9C/W Heat Sink,1 Three Phase SSR,1-4 Single Phase SSRs,HS-8 2.1C/W 45mm Din Rail Heat Sink,Single Phase SSRs,Crouzet 84060001“Smart Module”mou
14、nted to GN Series SSR,HS-9 1.3C/W 90mm Din Rail Heat Sink,1-2 Single Phase SSRs,HS-12 0.5C/W 60mm Din Rail Heat Sink,Single Phase SSRs,Manual Reset ThermalCutout,60mm 22CFM Fan,Digital I/O Modules,Solid State Relays,I/O Mounting Boards,Proximity Sensors,Sub-Fractional H.P.Motors,Safety Relays,Indust
15、rial Timers,Industrial Counters,For technical assistance,pricing&availability,call 1-800-677-5311,Miniature Snap Action Switches,Limit Switches,Axial Fans,CROUZET,SSR/Heat Sink Assembly Design,GN SERIES SOLID STATE RELAYS,Return to Main Menu,CROUZET,CRYDOM,SOLID-STATE RELAYS,V.,CROUZET,CRYDOM,RATING
16、S TO 660VAC/125ADBC SUBSTRATE“BUSSED”POWER LEAD FRAMEINTERNAL TRANSIENT PROTECTION(standard)EMC COMPLIANT(LEVEL 3)LED INPUT STATUS INDICATOR(standard)REGULATED INPUTSURFACE MOUNT PCBOPTIONAL IP20 HOUSINGUL/CSA/TUV(VDE)APPROVED,CE COMPLIANT,GN SERIES SSRs v.HA/HD SERIES SSRs,PRESS-FIT&SOLDER TERMINAL
17、S,FORM&SOLDERLEAD FRAME,TRANSISTOR OUTPUTOPTICAL ISOLATORS,THICK-FILMCERAMIC SUBSTRATE,STAMPED ALUMINUM BASE PLATE,CRYDOM,TRIAC DRIVEROPTICAL ISOLATORS,INTERNAL TRANSIENTPROTECTION,LED INPUT STATUSINDICATOR,CROUZET,CROUZET,“BUSSED”POWERLEAD FRAME,DIRECT BOND COPPER(DBC)SUBSTRATE,CAST BASE PLATE,GN S
18、ERIES SSR PRESENTATION,Return to Main Menu,CROUZET,SOLID-STATE RELAYS,V.,CARLO GAVAZZI,CROUZET,RATINGS TO 660VAC/125ADBC SUBSTRATE“BUSSED”POWER LEAD FRAMEINTERNAL TRANSIENT PROTECTION(standard)EMC COMPLIANT(LEVEL 3)LED INPUT STATUS INDICATOR(standard)REGULATED INPUTSURFACE MOUNT PCBOPTIONAL IP20 HOU
19、SINGUL/CSA/TUV(VDE)APPROVED,CE COMPLIANT,GN SERIES SSRs v.RM SERIES SSRs,UL,CSA,CE,Clip On,MOV Across Output,100 amps max,CARLO GAVAZZI,CARLO GAVAZZI,FORMED POTENTIAL COLD SOLDER JOINT AND STRESS ON DBC SOLDER JOINT,DIRECT BOND COPPER SUBSTRATE;NOT SOLDERED TO BASE PLATE ON25A AND 50A MODELS,CARLO G
20、AVAZZI,SMALLER BASE PLATE REDUCES THEAVAILABLE SURFACE AREA FORHEAT TRANSFER,TRIAC DRIVEROPTICAL ISOLATORS,INTERNAL TRANSIENTPROTECTION,LED INPUT STATUSINDICATOR,CROUZET,CROUZET,“BUSSED”POWERLEAD FRAME,DIRECT BOND COPPER(DBC)SUBSTRATE,CAST BASE PLATE,Back to the GN SSR Presentation,CROUZET,CORPORATI
21、ON,SSR Thermal Derating,Properly derating any SSR-heat sink assembly is critical to the reliability of the assembly and overall satisfaction of the customer.Cost,Size,shape,color,or any other particular requirement,is secondary to insuring that the heat generated by the relay will be adequately diss
22、ipated by the heat sink.Lack of attention to detail when designing an assembly may significantly decrease the life of the relay or result in catastrophic field failures.,Essential derating information:Additional Helpful Information:Ambient Temperature(Tamb)Air Flow(CFM or LFM)Load Current(I)Duty Cyc
23、le SSR On-State Voltage Drop(Vf)Panel VentilationSSR Thermal Impedance(Rjb)Surrounding Heat SourcesHeat Sink Thermal Impedance(Rs-a)Surge Currents,SSR/Heat Sink Assembly Design,As can be seen from the formula,the temperature of the SCR die during normal operation is a sum of the product of the ambie
24、nt temperature,heat sink efficiency,SSR thermal impedance,and the total power being dissipated by the relay.If the sum exceeds the maximum temperature rating of the SCRs,which is typically 125C,then one or more of the variables must be reduced in order to prevent a failure of the SSR.If the sum is l
25、ess than the maximum temperature rating of the SCRs,then it is safe to proceed with a verification analysis of the assembly.,IT IS ALWAYS IMPORTANT TO VERIFY THE RESULTS OF THE INITIAL ESTIMATE,AS THE VARIABLES ARE NOT ALWAYS 100%ACCURATE!,Tdie=Tamb+(Rs-a x(I x Vf)+(Rjb x(I x Vf),GN SSR-SCR/BASE PLA
26、TE ASSEMBLY,GN SERIES SOLID STATE RELAYS,As the load current flows through the SCR die,heat is generated proportional to the amount of the current and the Vf of the SCRs.The total thermal impedance of the SCR/base plate assembly determines how much of this heat is transferred through the DBC and bas
27、e plate,and is measured in degrees Celsius per Watt being generated,or Rjb.,To calculate the temperature differential,or DT,between the SCR die and the base plate,we multiply the Rjb by the total power being generated.,Assume the SSR is carrying 50 amps of load current and has a forward voltage drop
28、 of 1.2Vpk.The junction-to-base plate thermal impedance is.155C/W,DT=Rjb x(I x Vf)DT=.155C/W x(50A x 1.2Vf)DT=9.3C,We now know that the SCR die are operating 9.3C hotter than the base plate of the SSR.Alone,this information is not very helpful,as it only gives us the DT,and not the actual temperatur
29、e of the SCR die.,To determine the actual temperature of the SCR die,we must determine the temperature of the SSRs base plate.,Heat Transfer,Heat Transfer&Thermal Impedances,The thermal impedance of the heat sink determines how much the temperature will vary between ambient and the base plate,relati
30、ve to how much power the SSR is dissipating.Heat sink efficiency is also measured in degrees Celsius per Watt of power,but will change depending upon the ambient temperature and the availability of forced airflow.For applications where the device is to be cooled through convection airflow,the heat s
31、ink must be mounted in a manner that will allow air flow to move up through the fins.,To estimate the base plate temperature of the SSR,simply multiply the heat sink impedance by the total power being dissipated,then add the sum to ambient.,Tbp=Tamb+(Rs-a x(I x Vf)Tbp=40C+(1.0C/W x(50A x 1.2Vf)Tbp=1
32、00.0C,Convection Airflow,Ambient to Base Plate,Since all of the variables are now known,we can estimate the temperature of the SCR die in an SSR with an Rjb of.155C/W and a Vf of 1.2Vpk,operating at 50 amps while mounted to a 1.0C/W heat sink.,Convection Airflow,Tdie=Tamb+(Rs-a x(I x Vf)+(Rjb x(I x
33、Vf),Tdie=40C+(1.0C/W x(50A x 1.2Vpk)+(.155C/W x(50A x 1.2Vpk),Tdie=40C+60C+9.3C,Tdie=109.3C,To be even more accurate,we should include the thermal pad,which has a thermal impedance of approximately 0.1C/W.Tdie=109.3C+(60W x.1C/W)Tdie=115.3C,Ambient to SCR Die,Now that we have determined that the SCR
34、 die should operate at less then their maximum rated temperature,a quick thermal analysis of the assembly must be performed to verify the accuracy of the calculation.This is important since any deviation in one or more of the variables will lead to significant differences between the calculated and
35、actual die temperature.Since it is not always feasible to attach a thermocouple to the die of an SSR,temperatures can be measured at the base plate of the SSR to verify the accuracy of the estimate.Unfortunately,this method still leaves a level of uncertainty in the analysis since we must calculate
36、the differential between the die and the base plate.However,as this calculation has the least impact in total temperature rise,and given the accuracy of measured power over estimated power dissipation,the end result will be fairly accurate.,Thermocouple inserted into a groove milled in the top of th
37、e heat sink.The groove should be slightly larger then the diameter of the TC to allow the SSR to mount flush with the heat sink.Tdie=actual base plate+(specified Rjb x actual power),To guarantee reliability,never let the base plate exceed 100C and allow the SSR to stabilize for a few hours before ta
38、king the final measurement!,Calculating the thermal impedance of a heat sink with forced air is a little more difficult since there are a few more variables and intangibles involved.There is,however,a simple formula that can give an estimate of the thermal impedance,which can then be verified throug
39、h evaluations.,Forced Vertical Airflow,For simplicity,lets assume that there is minimal obstruction to the airflow and that the“open”area in the heat sink is roughly the same size as the area of the fan.,First,we must convert the CFM rating to linear feet per minute(LFM);,LFM=(CFM/(area/144)x 70%(70
40、%derate for back pressure),LFM=(40/(9/144)x.7,LFM=(40/.0625)x.7,LFM=448(Derate down to 400LFM),Once the approximate LFM rating is known,a correction factor can be applied to the heat sink to determine the thermal impedance with airflow.,Velocity(LFM)Correction Factor100.757200.536300.439400.378500.3
41、38600.309700.286800.268900.2521,000.239,So our heat sink would have a.378C/W thermal impedance with 400 LFM of airflow.,Forced Air v.Convection Cooling,To demonstrate the increase in the efficiency of the heat sink provided by the 40CFM fan,we can calculate how much more current(I 50 Amps)the SSR wo
42、uld have to carry in order to obtain the same 115.3C die temperature as before.To insure adequate derating,we will round the impedance of the heat sink to 0.4C/W.,115.3C=Tamb+(Rs-a x(Vf x I)+(Rjb x(Vf x I),115.3C=40C+(.4C/W x 1.2X)+(.155C/W x 1.2X),115.3=40+.48X+.186X,75.3=.667X,X=112.9 Amps(Increas
43、e of 62.9 Amps),Always evaluate an assembly that is to be cooled by forced air before the customer begins using the assembly in their production.Forced air cooling systems are tricky at best and SSR failure may result from an inadequate understanding of the systems parameters.Installing assemblies i
44、n the customers equipment for thermal testing is the best way to insure overall reliability.,Forced Air Efficiency,A standard heat sink profile listed in an extruders catalog will typically have the thermal impedance specified when cut to a length of three inches.A rough determination of the impedan
45、ce of an extrusion profile cut in different lengths can be obtained with a correction factor.Multiplying the Rs-a/3”by the correction factor for the desired extrusion length will give the thermal impedance of that profile when cut to that length.This is a valuable tool when designing prototype assem
46、blies,but the correction factor will vary slightly for each profile due to various spacing and lengths of the fins.,Extrusion LengthCorrection Factor1”1.802”1.253”1.004”.875”.786”.737”.678”.649”.6010”.5811”.5612”.54,Cut-to-Length Extrusions,2X+3Y=Z,To Calculate Heat Sink Thermal Impedance:Rs-a=(Tbp-
47、Tamb)/PowerRs-a=(Tdie-(Rjb x Power)-Tamb)/Power,To Calculate Base Plate Temperature:Tbp=Tdie-(Rjb x Power)Tbp=Tamb+(Rs-a x Power),To Calculate Rjb:Rjb=(Tdie-Tbp)/Power,To Calculate SCR Temperature:Tdie=Tamb+(Rs-a x Power)+(Rjb x Power)Tdie=Tbp+(Rjb x Power),To Calculate Minimum Required Heat Sink Th
48、ermal Impedance:Rs-a-min=(Tdie-max-Tamb-(Rjb x Power)/Power,To Calculate Maximum Allowable Current Given Heat Sink Impedance:Imax=(Tdie-max-Tamb)/(Rs-a x Vf)+(Rjb x Vf),E=h x f,Its All in the Math,Always verify any calculation.Catastrophic field failures may occur if the actual value of a variable s
49、hifts even a slight amount from the estimate.Evaluate every new assembly in an environment as close as possible to the actual application or in the actual equipment for which it is intended.,Round up every number in the calculations and use maximum value specifications whenever possible.If the test
50、data yields results that are better than originally estimated,and target pricing is maintained,then everyone wins.,If something bad can possibly happen,assume that it will.Loss of airflow,100%duty cycle operation,heavy surge currents,and excessive ambient temperatures,are just examples of anomalies
