汽车电子系统中英文对照外文翻译文献

1、汽车电子系统中英文对照外文翻译文献(文档含英文原文和中文翻译)The Changing Automotive Environment:High-Temperature ElectronicsR.WayneJohnson,Fellow,IEEE,JohnL.Evans,PeterJacobsen,JamesR.(Rick)Thompson, and Mark ChristopherAbstractTheunderhoodautomotiveenvironmentisharshandcurrenttrendsin the automotive electronics industry will b

2、e pushing the temperatureenvelopeforelectroniccomponents.Thedesiretoplaceenginecontrolunitsontheengineandtransmissioncontrolunitseitheronorinthetransmissionwill push the ambient temperature above 125. However, extreme costpressures,increasing reliability demands (10 year/241 350 km) and the costoffi

3、eldfailures(recalls,liability,customerloyalty)willmaketheshiftto higher temperatures occur incrementally. The coolest spots on engine andinthetransmissionwillbeused.Theselargebodiesdoprovideconsiderableheatsinkingtoreducetemperatureriseduetopowerdissipationinthecontrolunit. The majority of near term

4、 applications will be at 150 or less and1these will be worst case temperatures, not nominal. The transition toX-by-wire technology, replacing mechanical and hydraulic systems withelectromechanical systems will require more power electronics. Integrationof power transistors and smart power devices in

5、to the electromechanicalactuator will require power devices to operate at 175 to 200 . Hybridelectricvehiclesandfuelcellvehicleswillalsodrivethedemandforhighertemperature power electronics. In the case of hybrid electric and fuel cellvehicles, the high temperature will be due to power dissipation. T

6、healternates to high-temperature devices are thermal management systems whichaddweightandcost.Finally,thenumberofsensorsinvehiclesisincreasingasmoreelectricallycontrolledsystemsareadded.Manyofthesesensorsmustworkinhigh-temperatureenvironments.Theharshestapplicationsareexhaustgas sensors and cylinder

7、 pressure or combustion sensors. High-temperatureelectronics use in automotive systems will continue to grow, but it will begradualascostandreliabilityissuesareaddressed.Thispaperexaminesthemotivation for higher temperature operation,the packaging limitations evenat 125 C with newer package styles a

8、nd concludes with a review of challengesat both the semiconductor device and packaging level as temperatures pushbeyond 125 .Index Automotive,extreme-environmentelectronics.I. INTRODUCTIONIN1977, the average automobile contained $110 worth of electronics 1. By2003 the electronics content was $1510 p

9、er vehicle and is expected to reach$2285in20132.TheturningpointinautomotiveelectronicswasgovernmentTABLE IMAJOR AUTOMOTIVE ELECTRONIC SYSTEMS2TABLE IIAUTOMOTIVETEMPERATUREEXTREMES(DELPHIDELCOELECTRONIC SYSTEMS) 3regulation in the 1970s mandating emissions control and fuel economy. The complexfuel co

10、ntrol required could not be accomplished using traditional mechanical systems.These government regulations coupled with increasing semiconductor computing power atdecreasing cost have led to an ever increasing array of automotive electronics. Automotiveelectronics can be divided into five major cate

11、gories as shown in Table I.The operating temperature of the electronics is a function of location, power dissipationby the electronics, and the thermal design. The automotive electronics industry defineshigh-temperature electronics as electronics operating above 125 .However, the actualtemperature f

12、or various electronics mounting locations varies considerably. Delphi DelcoElectronic Systems recently published the typical continuous maximum temperatures asreproduced in Table II 3. The corresponding underhood temperatures are shown in Fig. 1.The authors note that typical junction temperatures fo

13、r integrated circuits are 10 to15higher than ambient or baseplate temperature, while power devices can reach 25 higher.At-engine temperatures of 125 peak can be maintained by placing the electronics on the3intake manifold.Fig. 1. Engine compartment thermal profile (Delphi Delco Electronic Systems) 3

14、.TABLE IIITHEAUTOMOTIVEENVIRONMENT(GENERALMOTORS ANDDELPHIDELCOELECTRONICSYSTEMS) 4TABLE IVREQUIREDOPERATIONTEMPERATURE FORAUTOMOTIVEELECTRONICSYSTEMS(TOYOTAMOTORCORP. 5V 4Fig. 2. Automotive temperatures and related systems (DaimlerChrysler) 8.automotive electronic systems 8. Fig. 3 shows an actual

15、measuredtransmission temperature profile during normal and excessive drivingconditions 8. Power braking is a commonly used test condition where thebrakes are applied and the engine is revved with the transmission in gear.Asimilarreal-worldsituationwouldbeapplyingthrottlewiththeemergencybrake applied

16、. Note that when the temperature reached 135, the overtemperature light came on and at the peak temperature of 145, thetransmission was beginning to smell of burnt transmission fluid.5TABLE VIITRSA2002 NTERNATIONAL ECHNOLOGY OADMAPFOR EMICONDUCTORS MBIENTOPERATINGTEMPERATURESFORHARSHENVIRONMENTS (AU

17、TOMOTIVE)9The 2002 update to the International Technology Roadmap for Semiconductors (ITRS)did not reflect the need for higher operating temperatures for complex integrated circuits,but did recognize increasing temperature requirements for power and linear devices asshown in Table VI 9. Higher tempe

18、rature power devices (diodes and transistors) will beused for the power section of power converters and motor drives for electromechanicalactuators. Higher temperature linear devices will be used for analog control of powerconverters and for amplification and some signal processing of sensor outputs

19、 prior totransmission to the control units. It should be noted that at the maximum rated temperaturefor a power device, the power handling capability is derated to zero. Thus, a 200 ratedpower transistor in a 200 environment would have zero current carrying capability. Thus,the actual operating envi

20、ronments must be lower than the maximum rating.In the 2003 edition of the ITRS, the maximum junction temperatures identified forharsh-environment complex integrated circuits was raised to 150 through 2018 9. The6ambient operating temperature extreme for harsh-environment complex integrated circuitsw

21、as defined as 40to 125 through 2009, increasing to 40to 150for 2010 andbeyond. Power/linear devices were not separately listed in 2003.The ITRS is consistent with the current automotive high-temperature limitations. DelphiDelco Electronic Systems offers two production engine controllers (one on cera

22、mic andone on thin laminate) for direct mounting on the engine. These controllers are rated foroperation over the temperature range of 40 to 125. The ECU must be mounted on thecoolest spot on the engine. The packaging technology is consistent with 140 operation,but the ECU is limited by semiconducto

23、r and capacitor technologies to 125.The future projections in the ITRS are not consistent with the desire to place controllerson-engine or in-transmission. It will not always be possible to use the coolest location formounting control units. Delphi Delco Electronics Systems has developed anin-transm

24、ission controller for use in an ambient temperature of 14010 using ceramicsubstrate technology. DaimlerChrysler is also designing an in-transmission controller forusewith a maximum ambient temperature of 150 (Figs. 4 and 5) 11.II. MECHATRONICSMechatronics, or the integration of electrical and mechan

25、ical systems offers a numberofadvantages in automotive assembly. Integration of the engine controller with the engineallows pretest of the engine as a complete system prior to vehicle assembly. Likewise withthe integration of the transmission controller and the transmission, pretesting and tuning to

26、account for machining variations can be performed at the transmission factory prior toshipment to the automobile assembly site. In addition, most of the wires connecting to atransmission controller run to the solenoid pack inside the transmission. Integration of thecontroller into the transmission r

27、educes the wiring harness requirements at the automobileassembly level.7Fig. 4. Prototype DaimlerChrysler ceramic transmission controller 11Fig. 5. DaimlerChrysler in-transmission module 11.The trend in automotive design is to distribute control with network communications. Asthe industry moves to m

28、ore X-by-wire systems, this trend will continue. Automotivefinal8assembly plants assemble subsystems and components supplied by numerous vendors tobuild the vehicle. Complete mechatronic subsystems simplify the design, integration,management, inventory control, and assembly of vehicles. As discussed

29、 in the previoussection, higher temperature electronics will be required to meet future mechatronicdesigns.III. PACKAGINGCHALLENGES AT125Trends in electronics packaging, driven by computer and portable products areresulting in packages which will not meet underhood automotive requirements at125. Mos

30、t notable are leadless and area array packages such as small ball gridarrays (BGAs) and quadflatpacks no-lead (QFNs). Fig. 6 shows the thermal cycletest 40 to 125 results for two sizes of QFN from two suppliers 12. A typicalrequirement is for the product to survive 20002500 thermal cycles with %280）

31、provide options for use to 200.Cyanate ester boards have been used successfully in test vehicles at 175, but failed whenexposed to 250 26. The higher coefficient of thermal expansion (CTE) of the laminatesubstrates compared to the ceramics must be considered in the selection of componentattachment m

32、aterials. The temperature limits of the laminates with respect to assemblytemperatures must also be carefully considered. Work is ongoing to develop and implementembedded resistor and capacitor technology for laminate substrates for conventionaltemperature ranges. This technology has not been extend

33、ed to high-temperatureapplications.One method many manufacturers are using to address the higher temperatures while16maintaining lower cost is the use of laminate substrates attached to metal. The typicaldesign involves the use of higher Tg( +140 and above) laminate substrates attached to analuminum

34、 plate (approximately 2.54-mm thick) using a sheet or liquid adhesive. To assistin thermal performance, the laminate substrate is often thinner (0.76 mm) than traditionalautomotive substrates for under-the-hood applications. While this design providesimproved thermal performance, the attachment of t

35、he laminate to aluminum increases theCTE for the overall substrates. The resultant CTE is very dependent on the ability of theattachment material to decouple the CTE between the laminate substrate and the metalbacking. However, regardless of the attachment material used, the combination of thelamina

36、te and metal will increase the CTE of the overall substrate above that of astand-alone laminate substrate. This impact can be quite significant in the reliabilityperformance for components with low CTE values (such as ceramic chip resistors). Fig. 9illustrates the impact of two laminate-to-metal att

37、achment options compared to standardlaminate substrates 27, 28. The reliability data presented is for 2512 ceramic chipresistors attached to a 0.79-mm-thick laminate substrate attached to aluminum using twoattachment materials. Notice that while one material significantly outperforms the other,both

38、are less reliable than the same chip resistor attached to laminate without metalbacking.This decrease in reliability is also exhibited on small ball grid array (BGA) packages.Fig. 10 shows the reliability of a 15-mm BGA package attached to laminate compared tothe same package attached to a laminate

39、substrate with metal backing 27, 28. Theattachment material used for the metal-backed substrate was the best material selectedfrom previous testing. Notice again that the metal-backed substrate deteriorates thereliability. This reliability deterioration is of particular concern since many IC package

40、sused for automotive applications are ball grid array packages and the packaging trend is forreduced packaging size. These packaging trends make the use of metal-backed substratesdifficult for next generation products.One potential solution to the above reliability concern is the use of encapsulants

41、 andunderfills. Fig. 11 illustrates how conformal coating can improve component reliability forsurface mount chip resistors 27, 28. Notice that the reliability varies greatly dependingon material composition. However, for components which meet a marginal level ofreliability, conformal coatings may a

42、ssist the design in meeting the target reliabilityrequirements. The same scenario can be found for BGA underfills. Typical underfillmaterials may extend the component life by a factor of two or more. For marginal ICpackages, this enhancement may provide enough reliability improvement toall the desig

43、nsto meet under-the-hood requirements. Unfortunately, the improvements provided by17encapsulants and underfills increase the material cost and adds one or more manufacturingprocesses for material dispense and cure.Interconnections: Methods of mechanical and electrical interconnection of the active a

44、ndpassive components to the board include chip and wire,flip-chip, and soldering ofpackaged parts. In chip and wire assembly, epoxy die-attach materials can beused to 165 29. Polyimide and silicone die-attach materials can be used to 200 . Forhigher temperatures, SnPb ( 90Pb), AuGe, AuSi, AuSn, and

45、AuIn have been used.However,with the exception of SnPb, these are hard brazes and with increasing die size,CTE mismatches between the die and the substrate will lead to cracking with thermal18cycling. Agglass die attach has also been used with Si die, but the die stresses are high30. The processing

46、temperatures (330 to 425) required for the hard brazes and theAg-glass are not compatible with the laminate-based substrates.Small-diameter Au and Pt wire bonding can be used to 500 on thick-film Au with Aupads on the SiC die 22.However, most Si die have aluminum metallization and the use ofAu wire

47、is limited to 180 to 200 due to AuAl intermetallic formation andKirkendall voiding. Use of Al wire creates a monometallic bond at the die interface.Pd-doped thick-film Au conductors have been developed for compatibility withsmall-diameter Al wire to 300 31. While Al wire can be bonded to silver bear

48、ingthick-film conductors, the primary concern is corrosion due to the galvanic potentialbetween Al and Ag 32. Chlorine contamination in the presence of moisture is the primarycorrosion mechanism. Increasing the Pd content of the PdAg conductor, extreme care inthe cleanliness of the assembly and pott

49、ing in silicone gel can be used to reduce the risk ofcorrosion. Au wire can be bonded to pure Ag thick films, but the Ag migrates along thesurface of the gold wire at elevated temperatures 33.On laminate substrates, Ni/Aufinishes over the copper are compatible with Au wire(thick Aufinish) and with A

50、l wire (thin Aufinish). In the case of Al wire, the Au layer mustbe thin so the Al wire bonds to the underlying Ni. Intermetallic formation and voiding willoccur if the Au layer is too thick. If a phosphorus containing Ni is used, the phosphoruscontent should be limited to 6 8 .AlNi bonds are potent

51、ially reliable to 300, butfurther study is required 32.For wire bonding to power devices, large-diameter Al wire bonding is used. In some19cases the Al wire is bonded directly to the thick-film PdAg conductors (the potential for AlAg corrosions exists) or to Ni-plated slugs soldered to the metalliza

52、tion.For solder assembly of passives,flip-chip die and packaged semiconductors, alternatesolders are required above 135 to 140 to replace eutectic SnPb. High-lead solders canbe used if the substrate and component can withstand the assembly temperature. Atintermediate temperatures, lead-free solders

53、are being considered. The SnAgCu eutecticalloy has been selected by the general electronics industry to replace eutecticSnPb.However, the performance of this alloy with 2512 chip resistors and 1206 chipresistors arrays on high- laminate over the 40to 150 thermal cycle range issignificantly worse com

54、pared to eutectic SnPb (Figs. 12 and 13) 34. As seen in Fig. 12,fourth-element additions such as Bi to the SnCuAg alloy improve the thermal cycleperformance.The NCMS report on lead-free, high-temperature, fatigue-resistant solder recommendsSn3.35Ag1Cu3.3Bi and Sn4.6Ag1.6Cu1Sb1Bi for 55to 160 applica

55、tions35. Theperformance of the NCMS-selected solders over the range from 55 to 160 is still lessthan the reliability of SnPb over the 55to 125 range. Thus, extending the temperaturerange with these alloys will be less reliable than the current SnPb assemblies at 125 Withthe push in the automotive in

56、dustry to 150 000 mile/10 year design goals, this will pose anissue for high-temperature electronics acceptance. Amagai et al. have evaluated the effectof Ag and Cu percent composition as well as the addition of various fourth elements onreliability with a goal of optimizing thermal cycle and mechan

57、ical shock performance 36.Nowottnicket al.have proposed using liquid solders for high-temperature applications 37.In this approach, Sn Bi solders are used. At elevated operating temperatures, the solderalloys melt, but maintain electrical contact. A polymer encapsulant is used to maintainmechanical

58、integrity when the solder is molten. Work continues tofind betterhigh-temperature soldering solutions or automotive applications.Flip-chip assembly on thick-film ceramic substrates with high Pb-containing solders hasbeen used for many years. With increasing die size and thermal cycle range, underfil

59、ls willbe required to improve the thermal cycle reliability on ceramic. Underfill is definitelyrequired on laminate substrates. Most commercial underfills have a less than 150 and arenot suitable. Higher underfills are being developed for higher temperature automotiveapplications on both ceramic and

60、 laminate Substrates.20Electromigration and underbump metallurgy diffusion at elevated temperature are alsoissues withflip-chip solder bumps. Electromigration can contribute to consumption of theunderbump metallurgy and joint failure. The allowable current density (current/area ofpassivation opening