1SSR / Heat Sink Assembly Design Product PresentationGN SERIES SOLID STATE RELAYSSSR / Heat Sink Assembly DesignReturn to Main Menu
2Crouzet Innovation In Solid State Technology Technology Plus The TechniqueInnovation In Solid State Technology
3Features Ratings to 125 Amps / 660 Vac Direct Bond Copper Substrate Improved Power Lead Frame DesignInput Status LED IndicatorSurface Mount TechnologyCast Base PlateEMC Compliant ( Level 3 )Internal Transient ProtectionLarger SCR DieOptional IP20 Touch Safe HousingUL / cUL / CSA Recognized, TUV Approved, CE Compliant
4ObjectivesDevelop a solid state relay that utilizes the latest technology and has as many features as possible incorporated into the initial design.Design a back-to-back SCR assembly with a thermal efficiency that is significantly better than our competition’s 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 reducemanufacturing time.Develop and implement automated test procedures that verify theintegrity and functionality of the SSR.All of these objectives were met before the GN SSR’s were introducedinto the market.
5Competetive Analysis GN v. Crydom?? Click Here GN v. Carlo Gavazzi?? GN SSR Feature Crydom Teledyne Carlo Gavazzi ContinentalCurrent Ratings to 125 AmpsDirect Bond Copper substrateEMC Compliant (Level 3)Standard Internal Transient Protection“Bussed” Power Lead-FrameCast Base PlateLED Input Status IndicatorSurface Mount DesignOptional IP20 “Touch-Safe” HousingComparison against Crydom HA/HD Series, Teledyne SSR Series, Continental SV Series, and Carlo Gavazzi RM SeriesYesNo*No*Teledyne uses exposed ceramic substrate as base plateNoYes**Yes**Snap-on protective cover included with the Carlo Gavazzi RM Series SSRYesNoNoYes
6Thermal Derate Information ?? Click Here Thermal EfficiencyHeat is the primary 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 application 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 efficiency 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.Thermal Derate Information ?? Click Here
7Direct Bond Copper SSR Rjb Comparison Direct Bond Copper (also known 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% thinner than traditional ceramic substrates, making the SSR even more efficient.SSR Rjb ComparisonRjb Rating - ºC/W10Amp25Amp50Amp75Amp100Amp125AmpCarlo Gavazzi RM SeriesCrydom HD SeriesTeledyne SSR SeriesN/A0.800.500.201.481.020.630.310.28*0.220.400.350.300.25Crouzet GN Series0.1550.15*Rjb rating for 100A applies to Crydom 90A SSR’s
8GN SERIES SOLID STATE RELAYS “Bussed” Power Lead FrameDirect Bond CopperSubstrateCast Base Plate
9Reliability Surface Mount Components EMC Compliance Epoxy-Free Design Reduces the possibility of human error in component placement and soldering.EMC ComplianceAllows the SSR to operate normally in harsh electrical environments without being damaged or creating electrical noise that might interfere with ancillary equipment.Epoxy-Free DesignEliminates the possibility of components becoming damaged due to the encapsulation expanding and contracting as the relay is heated and cooled. Also reduces capacitive coupling between the input and output circuitry that may allow a relay to be more susceptible to electromagnetic interference. The PCB is covered with a conformal coating to prevent the ingress of dust or moisture and to maintain dielectric strengthAutomated Test EquipmentIn-process test equipment automatically verifies critical parameters and separates any rejected unit from the good units. A proprietary thermal impedance measuring system, called the “Delta Vf” test, verifies the integrity of the SCR assembly. X-ray equipment is then utilized to corroborate the results.
10GN SERIES SOLID STATE RELAYS Regulated AC & DC InputsVDE ApprovedOptical-IsolatorsInternal Transient Protection
11Electromagnetic Compatability 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 normally in this type of environment is essential for reliability.The GN Series SSR’s have been designed and evaluated for compliance with level 3 requirements of the European Union’s EMC Directive. This has resulted in a relay with enhanced reliability that can facilitate an OEM’s evaluation for EMC compliance. It also eliminates the need for external transient protection, such as MOV’s.
12Applications Typical Applications for the GN Series SSR’s Theatrical Lighting Systems Warehouse Lighting SystemsPlastics; Injection, Blow Molding, Extrusion and Thermoforming EquipmentSolder Reflow Systems Rotisserie OvensDeep Fat Fryers Packaging EquipmentIndustrial Electric Furnaces Conveyer SystemsMaterial Handling Equipment Compressor SystemsMedical Equipment Vending MachinesUninterruptible Power Supplies Copy MachinesWelding Equipment Water Treatment SystemsVirtually any manufacturer of electrical equipment switching current in excess of 1 amp may utilize solid state relays.
13SSR Selection GN Part Number Matrix: To better enable Crouzet in helping you select the right relay, obtain as much information as possible about the application before calling for assistance. A few key questions to ask include:Line Voltage Ambient Temperature Inside PanelLoad & Steady-State Current Type of Load & Duty CycleControl Voltage Available Cabinet SpaceMounting Requirements Airflow (Forced or ConvectionGN Part Number Matrix:Package Style:Output Type:Current:Control Voltage:84 13412= IP00= IP200 = Vac / Zero Cross1 = Vac / Zero Cross2 = Vac / Random3 = Vac / Random*9 = Vac / Triac Output0 = 10 Amps1 = 25 Amps2 = 50 Amps3 = 75 Amps4 = 100 Amps8 = 125 Amps0 = 4-32Vdc**1 = Vac**2 = 18-36Vac*Triac version available with only 10 & 25 amp output**AC input available with only zero-crossing output
26CROUZET CRYDOM GN SERIES SSR's v. HA/HD SERIES SSR's RATINGS TO 660VAC / 125ADBC SUBSTRATE“BUSSED” POWER LEAD FRAMEINTERNAL TRANSIENT PROTECTION(standard)EMC COMPLIANT (LEVEL 3)LED INPUT STATUS INDICATORREGULATED INPUTSURFACE MOUNT PCBOPTIONAL IP20 HOUSINGUL/CSA/TUV (VDE) APPROVED, CE COMPLIANT(OPTIONAL)(HD SERIES ONLY)
27STAMPED ALUMINUM BASE PLATE PRESS-FIT & SOLDERTERMINALSCRYDOMFORM & SOLDERLEAD FRAMETRANSISTOR OUTPUTOPTICAL ISOLATORSTHICK-FILMCERAMIC SUBSTRATESTAMPED ALUMINUM BASE PLATE
28CROUZET TRIAC DRIVER OPTICAL ISOLATORS LED INPUT STATUS INDICATOR INTERNAL TRANSIENTPROTECTION
29CROUZET DIRECT BOND COPPER (DBC) SUBSTRATE “BUSSED” POWER LEAD FRAME CAST BASE PLATE
32CROUZET CARLO GAVAZZI GN SERIES SSR's v. RM SERIES SSR's RATINGS TO 660VAC / 125ADBC SUBSTRATE“BUSSED” POWER LEAD FRAMEINTERNAL TRANSIENT PROTECTION(standard)EMC COMPLIANT (LEVEL 3)LED INPUT STATUS INDICATORREGULATED INPUTSURFACE MOUNT PCBOPTIONAL IP20 HOUSINGUL/CSA/TUV (VDE) APPROVED, CE COMPLIANT100 amps maxMOV Across OutputClip OnUL,CSA,CE
33CARLO GAVAZZI FORMED & SOLDERED LEAD-FRAME; POTENTIAL COLD SOLDER JOINT ANDSTRESS ON DBC SOLDER JOINTCARLO GAVAZZIDIRECT BOND COPPER SUBSTRATE;NOT SOLDERED TO BASE PLATE ON25A AND 50A MODELS
34CARLO GAVAZZI SMALLER BASE PLATE REDUCES THE AVAILABLE SURFACE AREA FORHEAT TRANSFER
35CROUZET TRIAC DRIVER OPTICAL ISOLATORS LED INPUT STATUS INDICATOR INTERNAL TRANSIENTPROTECTION
36CROUZET DIRECT BOND COPPER (DBC) SUBSTRATE “BUSSED” POWER LEAD FRAME CAST BASE PLATE
39SSR / Heat Sink Assembly Design 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 dissipated 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 CycleSSR On-State Voltage Drop (Vf) Panel VentilationSSR Thermal Impedance (Rjb) Surrounding Heat SourcesHeat Sink Thermal Impedance (Rs-a) Surge Currents
40Tdie = Tamb + (Rs-a x (I x Vf)) + (Rjb x (I x Vf)) As can be seen from the formula, the temperature of the SCR die during normal operation is a sum of the product of the ambient 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 125ºC, then one or more of the variables must be reduced in order to prevent a failure of the SSR. If the sum is less 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!
41GN SERIES SOLID STATE RELAYS If we take the formula in steps, we can calculate the temperature of the two “critical” points of the assembly. The first half of the formula, “Tamb + (Rs-a x (I x Vf))”, gives the actual temperature of the base plate of the SSR. The second half of the formula, “(Rjb x (I x Vf))”, gives the temperature differential between the base plate and the SCR die.To fully appreciate all of the variables involved, we must understand the components that make up those variables;GN SSR - SCR / BASE PLATE ASSEMBLYSCR DIE; Switches the load current. The die are soldered to the copper traces on the top-side of the DBC.CERAMIC SUBSTRATE; Provides electrical isolation between the SCR die, which are at line potential, and the base plate of the SSR. The copper traces on the bottom of the DBC are soldered to the base plate of the SSR.COPPER TRACES; The traces are “fused” with the ceramic, forming the DBC substrate. This provides a path for the load current through the SCR die, and allows heat to spread throughout the entire surface of the substrate.SSR BASE PLATE; Transfers the heat generated by the SCR die to the heat sink.
42Heat Transfer & Thermal Impedances 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 base 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 of 1.2Vpk. The junction-to-base plate thermal impedance is .155ºC/WWe now know that the SCR die are operating 9.3ºC 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 temperature of the SCR die.DT = Rjb x (I x Vf)DT = .155ºC/W x (50A x 1.2Vf)DT = 9.3ºCTo determine the actual temperature of the SCR die, we must determine the temperature of the SSR’s base plate.Heat Transfer
43Base Plate Temperature Ambient to Base PlateThe thermal impedance of the heat sink determines how much the temperature will vary between ambient and the base plate, relative 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 sink 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.Assume the SSR is carrying 50 amps of load current and has a forward voltage drop of 1.2Vpk. The thermal impedance of the heat sink is 1.0ºC/W and Tamb is 40ºCBase Plate TemperatureTbp = Tamb + (Rs-a x (I x Vf))Tbp= 40ºC + (1.0ºC/W x (50A x 1.2Vf))Tbp= 100.0ºCTamb = 40ºCConvection Airflow
44SCR Assembly; 0.155ºC/W Rjb, 1.2Vpk Vf Ambient to SCR DieSince all of the variables are now known, we can estimate the temperature of the SCR die in an SSR with an Rjb of .155ºC/W and a Vf of 1.2Vpk, operating at 50 amps while mounted to a 1.0ºC/W heat sink.Tdie = Tamb + (Rs-a x (I x Vf)) + (Rjb x (I x Vf))Tdie = 40ºC + (1.0ºC/W x (50A x 1.2Vpk)) + (.155ºC/W x (50A x 1.2Vpk))Tdie = 40ºC + 60ºC+ 9.3ºCTdie = 109.3ºCTo be even more accurate, we should include the thermal pad, which has a thermal impedance of approximately 0.1ºC/W.Tdie = 109.3ºC + (60W x .1ºC/W)Tdie = 115.3ºCSCR Assembly; 0.155ºC/W Rjb, 1.2Vpk VfThermal Heat Sink Compound or Thermal Pad1.0ºC/W Heat SinkTamb = 40ºCConvection Airflow
45Now that we have determined that the SCR 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 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 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.To guarantee reliability, never let the base plate exceed 100ºC and allow the SSR to stabilize for a few hours before taking the final measurement!!Thermocouple inserted into a groove milled in the top of the 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)
46Forced Air v. Convection Cooling 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 through evaluations.For simplicity, let’s 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% derate for back pressure)Forced Vertical AirflowLFM = (40 / (9 / 144)) x .7LFM = (40 / .0625) x .7LFM = 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.1.0ºC/W Heat Sink(Convection)Velocity (LFM) Correction Factor1,(1.0ºC/W x .378)So our heat sink would have a .378ºC/W thermal impedance with 400 LFM of airflow.3” x 3” 40 CFM Fan
47Forced Air EfficiencyTo 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 would have to carry in order to obtain the same 115.3ºC die temperature as before. To insure adequate derating, we will round the impedance of the heat sink to 0.4ºC/W.115.3ºC = Tamb + (Rs-a x (Vf x I)) + (Rjb x (Vf x I))115.3ºC = 40ºC + (.4ºC/W x 1.2X) + (.155ºC/W x 1.2X)115.3 = X X75.3 = .667XX = Amps (Increase 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 in the customers equipment for thermal testing is the best way to insure overall reliability.
48Cut-to-Length Extrusions A standard heat sink profile listed in an extruder’s catalog will typically have the thermal impedance specified when cut to a length of three inches. A rough determination of the impedance 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 assemblies, but the correction factor will vary slightly for each profile due to various spacing and lengths of the fins.A 1.0ºC/W 3” profile cut to a length of 6” would have a thermal impedance of 0.73ºC/W.Extrusion Length Correction Factor1” 1.802” 1.253” 1.004” .875” .786” .737” .678” .649” .6010” .5811” .5612” .54
492X + 3Y = Z qp pq ¹ E=h x f l = h / (m x v) It's All in the Math To Calculate SCR Temperature:Tdie = Tamb + (Rs-a x Power) + (Rjb x Power)Tdie = Tbp + (Rjb x Power)To Calculate Heat Sink Thermal Impedance:Rs-a = (Tbp - Tamb) / PowerRs-a = ((Tdie - (Rjb x Power)) - Tamb) / Powerqp pqTo Calculate Minimum Required Heat Sink Thermal Impedance:Rs-a-min = (Tdie-max -Tamb - (Rjb x Power)) / PowerTo Calculate Maximum Allowable Current Given Heat Sink Impedance:Imax = (Tdie-max - Tamb) / ((Rs-a x Vf) + (Rjb x Vf))To Calculate Base Plate Temperature:Tbp = Tdie - (Rjb x Power)Tbp = Tamb + (Rs-a x Power)E=h x fTo Calculate Rjb:Rjb = (Tdie - Tbp) / Powerl= h / (m x v)
50Ambient Might Not Be Ambient Words of WisdomCorroborate All DataAlways verify any calculation. Catastrophic field failures may occur if the actual value of a variable shifts 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.Derate The DeratingRound up every number in the calculations and use maximum value specifications whenever possible. If the test data yields results that are better than originally estimated, and target pricing is maintained, then everyone wins.Ambient Might Not Be AmbientThe ambient temperature given by the customer may be misleading. The room temperature outside of the panel, or panel temperature when the system is not running, will not help much when calculating minimum heat sink requirements. Insure that the temperature of the air moving through the fins of the heat sink is the value that is used in the estimates.Expect The WorstIf 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 that may occur in any application. If the customer has experienced them before, then he will most certainly experience them again.
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