1、TOYOTA ENGINEERING STANDARDNO.:TSC0509GTITLE: Life bench test method for solder oints of automotiveelectric and electronic equipmentCLASS:C1Established:/Revised:Rsv.4 (Nov. 2020)This standard has been revised as a result of the following changes:the method of observing solder cracks in BGA package p

2、arts has been added and revised Section 2 (21), Table 4, and Fig 19); andthe name of the check item has been changed from element size to die size (Table 1)Prepared and Written by:Electronic Performance Development &Engineering Dept.Electronics Control System Development Div.Design Quality Innovatio

3、n Dept.TOYOTA MOTOR CORPORATIONLife bench test method for solder joints of automotive electric and electroniceauipmentScopeThis standard covers the implementation method of life bench test for solder joints of electric and electronic equipment installed in automobiles. The solder joints of electroni

4、c equipment that are specified here conform to the terms and definitions in Section 2 below In the case where this life test method is applied to solder joints other than these, the concerned parties shall discuss this separately and the test shall be carried out in accordance with the strength of t

5、he relevant joints, the stresses that are applied to those joints, and the target performance of the component. For items whose conditions are not specified in detait here (measurement range.test conditions, etc.), the conditions shall be determined in consideration of the design specifications afte

6、r agreement with the concerned departments.DefinitionsAutomotive electric and electronic equipment (hereinafter referred to as equipment) The term automotive electric and electronic equipment refers mainly to devices (ECU) that control the system using semiconductor devices and also other equipment

7、such as various detection devices (sensors) and electromagnetic equipment (actuators) that are used in conjunction with the ECU. SolderSolder is a soft metal alloy with a melting point of less than 450 C whose main component is tin (Sn). It is used to create a bond between metals and join them toget

8、her. The solder utilizes the capillary action phenomenon between two metal surfaces to spread and distribute itself.Resin circuit boardA resin circuit board is a resin part in the shape of a board or film that has several electronic parts attachied to its surface. An electrical circuit is formed by

9、connecting these electronic parts with wiring. The main materials of the circuit board are glass epoxy.Electronic parts.Electronic parts are the general term used for the parts that compose the electrical circuits in the electronic equipment. The main active elements are devices such as semiconducto

10、rs, while the main passive elements are devices such as resistors and capacitors.Solder jointsSolder joints refer to the portions where the copper film pattern of the resin circuit board and the electrode terminal of electronic parts are connected together using solder.Upper limit temperature of tes

11、t sampleThe upper limit temperature of test sample is the upper limit value of the test temperature conditions applied to the test samples. This is the temperature that is determined by considering the atmospheric temperature, change in solar radiation temperature, change in operating temperature of

12、 surrounding parts, change in operating temperature ofelectronic parts, and the required specifications.Lower limit temperature of test sampleThe lower limit temperature of test sample is the lower limit value of the test temperature conditions applied to the test samples. This is the temperature th

13、at is determined by considering the minimum atmospheric temperature of the destination region and the required specifications.Change in atmospheric temperatureThe change in atmospheric temperature causes the change in temperature of solder joints by the atmospheric temperature of the environment in

14、which the vehicle is actually used (minimum atmospheric temperature to maximum atmospheric temperature).Change in solar radiation temperatureThe change in solar radiation temperature causes the change in temperature of solder joints by heating (conduction, radiating heat) due to radiation from the s

15、un (formerly referred to as radiation).The change may differ depending on the mounting position.Change in operating temperature of surrounding equipmentThe change in operating temperature of surrounding equipment is the change in temperature caused by heating due to the operation of other equipment

16、mounted around the electronic equipment. The temperature of solder joints changes due to the transfer of heat via conduction and radiation.The change may differ depending on the mounting position or the surrounding equipment usage.Change in operating temperature of electronic partsThe change in oper

17、ating temperature of electronic parts is the change in temperature caused by heating due to the operation of the electronic parts mounted on the circuit board. The temperature of solder joints changes due to the transfer of heat via conduction and radiation.The change may differ depending on the equ

18、ipment usage.Total amount of field stressThe total amount of field stress refers to the phenomenon that is dominant among the phenomena that cause stress and strain to the solder joints in the field. It is determined according to the amount and number of times the temperature changes in (8) to (11).

19、Theoretical studyTheoretical study is an activity to study the feasibility of the design specifications using technigues such as simulations in the phase in which test parts are yet to be available.Weaknesis detectionWeakness detection is the activity to identify weaknesses that were not identified

20、in the early phase of the development.This activity includes the activity of checking the failure mode and failure limit of the weakness.Design verificationDesign verification is the verification activity to ensure that the reliability requirements are achieved in a quantitative manner using the pro

21、duct with the final specifications to be applied to the mass production.Micro voidMiqro void is a minute void.Kirkendall voidKirkendall void is a void generated by the diffusion between different metals.Die attach agentDie attach agent is an adhesive to fix the element to the base material. It is al

22、so called the die-bonding agent.InterposerInterposer is the circuit board that relays between the integrated chip having different terminal pitch and main circuit board.UnderfillUnderfill is the general term of the curable liquid resin used for the sealing of the integrated circuit.Ink impregnation

23、method (ink immersion method)A method including immersing BGA package parts in a colored liquid or fluorescent liquid, peeling off solder joints, and then observing the fracture cross sections of the joints.Basic Knowledge Related to SolderSolderingSoldering is to join the printed wiring board elect

24、rode (land) and electrode of the mounted part by solder.rrmrea wiring ooaroFig. 1 Example of SolderingSolder Deterioration MechanismThere are some modes of solder deterioration. Since on-board parts have many chances to be exposed to severe temperature under installation environment and usage enviro

25、nment, it is important to secure solder joint life affected by thermal stress. Fig. 2 shows an example of the solder joint model using the chip capacitator on ECU.Since linear expansion coefficient ap of the printed wiring board is different from linear expansion coefficient ac of the ceramic capaci

26、tator, strain occurs in the solder joint portion due to the expansion gap caused by thermal stress in the field. By repeated strain caused by thermal stress, the solder joint fatigues and starts cracking, resulting in rupture. Fig. 3shows a picture example of a crack in the solder joint. This pictur

27、e shows that crack occurs in the solder joint because of the rupture mode starting from the portion where strain concentrated.Solder crackFig. 3 Picture Example of Crack at Solder JointSolder crackFig. 3 Picture Example of Crack at Solder JointCrack Generation MechanismEutectic Solder (Leaded Solder

28、)Stress is repeatedly applied on the solder joint portion by temperature cycle. Diffusion of Sn is promoted and coarsening of the a phase (Pb rich) progresses. Since stable low energy sate is tried to be maintained in stress direction, shape of the a phase becomes long and thin. Especially, in the a

29、 phase and p phase (Sn rich) boundary faces, many grid missing and segregation of impurities are found and metastatic spread due to the application of stress is generated. Micro holes are generated in the grain boundary of the a phase and p phase, leading to lower breaking stress and crack progresse

30、s.Lead-free SolderAs shown in Fig. 4 inelastic strain accumulates at the solder joint portion with heat fatigue received. In order to release that strain, crystal orientation becomes misaligned and miniaturization progresses. That means heat fatigue progresses with accumulation of strain and repeate

31、d miniaturization to release the strain.Also, if further heat fatigue progresses, micro cracks occur in the formed grain boundary and the cracks progress due to the destruction of the grain boundary, which is caused by these micro cracks. Initial state(3 Subgrain boundaryformedSn phase Inelastic str

32、ain Miniaturization of crystal grain Destruction of grain boundary (crack) Initial state(3 Subgrain boundaryformedSn phase Inelastic strain Miniaturization of crystal grain Destruction of grain boundary (crack)Fig. 4 Lead-Free Solder Crack Generation MechanismSoldering Check SheetThe soldering check

33、 sheet (Table 1) shall be used to extract weaknesses and concerns.Check itemSoldenng guidelineExample proposal entries (make specific entries)Comments (Reason of discrepancy, etc.)Solder pasteMetal component ratioSn3AgO.5Cu(Solder composition)FluxThere shall be a standard for voids in solder, and It

34、 shall be satisfied. When coating is applied, hardening conditions for coating shall not be affectedVoid standard:%Solder shapeTIS 01201-00384 -Standard for soldering appearance quality shall be satisfied.Pnnted circuit boardUnear expansion coefficient in X. Y, and Z directionsShall be consistent wi

35、th the componentsX=ppmY= ppmZ=ppm(BGA land) Select SMD or NSMDNSMD is recommended (Note that the pattern shall not separate due to the strain caused in the process)(Solder resist: select)SMD NSMDSMD： Solder MaskDefinedNSMD: No Solder Mask DefinedBGA land diameterShall be 500 M m min. and the same as

36、 that of the BGALand diameterP mCu pattern surface treatmentCaution shall be used in micro-voids for Ag substitution, in migration for Sn substitution, and in Kirkendall voids for Ni plating Au plating.(Type of surface treatment)Table 1 (Continued)Check itemSoWering guidelineExample proposal entries

37、 (make specific entries)Comments (Reason of discrepancy, etc.)Mounted componentChip capacitatorSizeAmbientChip sizetemperature used 1051608max90 P2125max.85 P3216max.Ambient temperature used: C Max. chip size:Max. strain in assembly line500 M E max.Max. strain:M eEvaluation resultsEvaluation results

38、 shall be available.(More than target number of cycles shall be passed using the same type of the circuit board (substrate and layer structure) under the same evaluation conditions (temperature)Evaluation conditions used in past Number of cycles (actual):Chip resistorSizeAmbientChip sizetemperature

39、used 105 P1608max.90 X2125max.85 C3216max.Ambient temperature used: CMax chip size:Conformal coatingThe matenal shall not be silicone.(When siicone needs to be used, make sure to use sulfide resistant chips )Conformal coating material model: Material:Evaluation resultsEvaluation results shall be ava

40、ilableMore than target number of cycles shall be passed using the same drcult board under the same evaluation conditions (temperature).)Evaluation conditions used in past: Number of cycles (actual):BGAUnear expansion coefficient of package resinShall be consistent with that of the printed circuit bo

41、ard.Linear expansion coefficient: ppmDie sizeCheck solder crack around chip in anatysismmx mmDie attach materialWhen it is hard compared to package, check solder crack around chip in analysisComposition:SoWer ball compositionShall be consistent with that of solder paste composition.(SoWer compositio

42、n)Interposer (without build-up layer)BT resin(Type of base matenals)Check itemSoldering guidelineExample proposal entries (make specific entries)Comments (Reason of discrepancy, etc.)Mounted componentBGAInterposer (with build-up layer)There shall be no Stacked Via.(Type of base materials)There shall

43、 be no solder electrode immediately below Via hole.Build-up layer onto die surfaceUnderfill shall be used.(BGA land) SMD? NSMD?NSMD is recommended (Note that the pattern shall not separate due to the strain caused in the process.)(Solder resist: select)SMDNSMDLand diameterShall be 500 口 m min. and t

44、he same as that of land diameter on the circuit board side.口 mMax. strain in assembly lineElectrode in the soldering portion shall not separate although max. strain is applied.H Mounting positionMirror mounting layout on the surface side and back side of the circuit board shall not be apied.Underfil

45、lLinear expansion coefficient shall be close to that of solder.(Soldering portion shall have thermal cycle resistance.)Code:Material:Linear expansioncoefficient:ppmEvaluaUon resultsEvaluation results shall be available.(More than target number of cycles shall be passed using the same circuit board u

46、nder the same evaluation conditions (temperature)lEvaluation conditions used in past: Number of cycles (actual):Storage of componentsHumidity shall be controlled, and component shall be taken out of package immediately before mounting process.(Storage method of components)QFNLinear expansion coeffic

47、ient of package resinShall be consistent with that of the printed circuit board.Linear expansion coefficient:ppmEvaluation resultsEvaluation results shall be available.More than target number of cycles shall be passed using the same circuit board under the same evaluation conditions (temperature).Ev

48、aluation conditions used in past: Number of cycles (actual):Plating on terminalPb shall not be contained.When Bi is contained, content shall be less than 4 mass%.Pb content:mass%Bi contentmass%Check itemSoldenng guidelineExample proposal entries (ntake specific entries)Comments (Reason of discrepanc

49、y, etc.)Mounted componentQFNStorage of componentsHumidity shall be controlled, and component shall be taken out of package immediately before mounting process.(Storage method of components)Resin package with leadsEvaluation resultsEvaluation results shall be available.(More than target number of cyc

50、les shall be passed using the same circuit board under the same evaluation condibons (temperature).Evaluabon conditions used in past: Number of cycles (actual):Plating on tenninalPb shall not be contained When Bi is contained, content shall be less than 4 mass%Pb content：mass%Bi content:mass%Storage

51、 of componentsHumidity shall be controlled, and component shall be taken out of package immediately before mounting process.(Storage method of components)Other general itemsLead componentsLinear expansion coefflaent of package resinShall be consistent with that of the arcuit base board.Linear expans

52、ion coefficientppmConformal coatingApplication areaAreas to apply coating and areas where coating application is prohibited need to be made dearHardenrgWhen coating ts known to penetrate beneath die. it shall be confirmed that hardening has been completed.Power cycle testWhen frequency of self heati

53、ng cooling is high, study is required.(Study result)Theoretical studyStudy verification of solder joint life by theoretical study. However, when weakness and concerns were not found in the design review and solder check sheet and when there are verified results, this procedure can be omitted.Results

54、 of weakness detection and design verification can be, substituted for theoretical study.Analysis ProceduresClarify weakness identified by the design review and element package type of concerns.Clarify the linear expansion coefficient of identified elements and all of their properties.Clarify the ga

55、p of the linear expansion coefficient of components to which the element mentioned above is installed.Analyze fatigue life of the part joint portion result from expansion and shrinkage during the part thermal cycle, and quantitate it.Identify the analysis method used in the determination of the fati

56、gue life, and check verification result as well as the analysis method.Deterioration Index StudyIn general, when stress due to the heat load is applied to the lead-free solder, crystal orientation of Sn phase becomes misaligned, miniaturization of crystal grain progresses and crack is generated, for

57、ming crystal grain boundary. By conducting analysis using EBSD (Electron Backscatter Diffraction) which enables observation of crystal orientationof Sn phase, deterioration degree can be estimated There is an example that allows to make judgment at early stage by scaling the fatigue life to the ther

58、mal dycle about the weakness and concerned elements and making deterioration index in advance. Identify the deterioration index that was used for estimating fatigue life and submit it with the verification result.Weakness DetectionStudy verification of the design of solder joint life by high acceler

59、ation test. Check for the limit and breakage mode related to weakness and concerns of a part in the early phase of the development. However, when weakness and concerns were not found in the design review and solder check sheet and when there are verified results, this procedure can be omitted.Result

60、s of the design verification can be substituted.Initial MeasurementMeasure the following items under the standard conditions (normal temperature: 5 to 35 C, normal humidity: 45 to 85 % RH, and normal atmospheric pressure: 86 to 106 kPa).Characteristic measurementMeasure the characteristics in accord