VISHAY SILICONIX www.vishay.com Power MOSFETs Application Note AN840 “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET By Kandarp Pandya These guidelines chronologically cover most pertinent aspects and information for a proficient and valuable failure analysis of a suspect power MOSFET in electronic control applications. Any failure in mass production environment raises the priority flags. Invariably, all the possible resources are pulled in to propel the best possible concurrent engineering efforts. The aim is to identify the root cause of failure and implement the containment action plan at the earliest possible opportunity. These guidelines help to maintain smooth and adequate information exchange in timely manner during the rush mode - due to raised priorities - of failure analysis. One of the immediate and initial steps in most cases is to send the suspect power MOSFET back to the manufacturer and get the manufacturing expertise engaged on the failure analysis as soon as possible. Well established protocol starting with Product Analysis Request form - Appendix A, steers the failure analysis process to a final 8D report concluding the root cause and recommended action plan, if any. However, we do encounter scenarios where it is not possible to establish root cause of the MOSFET failure. That brings us to “The Next Step” for Failure Analysis. The attempt here is to start with a fresh look at everything i.e., work done so far and examine additional aspects that can help establish the root cause of failure. The focus here is extended to include application and examine each and every aspect looking for a possible cause that could lead to the failure of the MOSFET in question. Appendix B Collects the Information with Focus on the Followings: a. Number of failures 1. ICT - In-Circuit Tester - Quantity - Electrical schematic diagram of test setup - Test program 2. Functional Test - Quantity - Electrical schematic diagram of test setup - Test program 3. Field Returns - Quantity - Length of operating life before field failure g. Changes if any at any stage of PC board assembly and testing 1. Any other component level change in the associated circuit 2. Test program changes 3. Assembly or hardware changes at product level 4. Assembly or hardware changes at end use • Actual application, function of the MOSFET in the circuit. • Examination of operating parameters and conditions under normal operation. • Examination of operating parameters and conditions worst case analysis. • Analysis of waveforms for electrical parameters see Appendix C and D: a. VGS - Gate-Source Voltage b. VDS - Drain-Source Voltage c. ID - Drain Current d. PD - Power Dissipation in MOSFET • The waveform analysis for both normal and worst case conditions includes b. Total usage number in the application a. one complete On/Off cycle c. The period of usage in the particular application and platform b. Zoomed view of turn-on event d. Total usage number in identical application but on different platform e. Total usage number in same application but different assembly location/facility Revision: 28-Feb-14 c. Zoomed view of turn-off event • The *.csv files of waveforms listed in “Appendix C and D” above help define power profiles useful for thermal simulations if necessary. Refer to Appendix E for an example. Document Number: 67336 1 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 APPLICATION NOTE • Statistical data: f. Failure point: Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET The recommended protocol in “The Next Step” analysis is to send the complete PC board assembly with the suspect MOSFET - un-disturbed. However, in case, the Entire PC board assembly is not practical to send, at least very carefully removed, 25 mm x 25 mm (1" x 1") cut-out PCB around the suspect MOSFET is the second preferred option. In most of the first time failures, the user tend to test the suspect MOSFET on PC Board assembly using commonly used hand held multimeter to confirm the failure. De-solder the part using standard soldering stations and send the same to the manufacturer. However, the suspect MOSFET could have walked through a pit-fall losing significant failure signature/s. The testing and handling of the suspect MOSFET is quite critical for detecting and retaining the failure signatures in its original conditions. This is imperative as the subsequent failure analysis is equally complex as the original manufacturing process of the MOSFET die. Please refer to the application note AN839, “Guidelines for Handling Failed Power MOSFETs on PCB Assembly”. Recommended Procedure and Steps: • Prepare and pack for shipping the PCB assembly containing the suspect MOSFET or the suspect MOSFET for failure analysis. Typically, the package contains: a. The suspect MOSFET on PCB assembly or cut-out as discussed above. b. The Vishay Siliconix Failure Analysis Request form, Appendix B; duly completed to the possible extent. The missing information can follow later to expedite and facilitate proficient failure analysis. • Here are the shipping instructions: Shipping label should read Leilani L. Taa Manager, Document Control & Customer Returns Quality Engineering & Systems Vishay Siliconix 2201 Laurelwood Road, Santa Clara, CA. 95054-1595, USA Phone: +1 (408) 970-5481 | Fax: +1 (408) 567-8991 e-mail: [email protected] • Vishay Siliconix will further investigate the failure mode. The failure analysis continues with communications exchanges on findings and mutually agreed action plans. APPLICATION NOTE • Final response from Vishay Siliconix - an updated “8D” summarizes finding of failure analysis and mutually agreed containment action plan - required if any. Revision: 28-Feb-14 Document Number: 67336 2 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET APPENDIX A Customer Analysis Request CS Group Ref: Customer Information CS Group -xxxxx Vishay Information Customer : Vishay Originator : Contact Person : Date Vishay 1st Rec'd : Tel No. : Date Sent to Mfg Site : Email Address : Sent to : Cust. Ref. No. : Sales/CS Contact : Cust. Location : AWB # : Datecode : Device Information Vishay PN : Customer PN : Plant Code : Quantity : Lot/Serial # : Potential Return : DN/Invoice # : Defect Information [ Type of Complaint [ [ ] Electrical [ ] Mechanical [ ] Visual ] Packing [ ] Label [ ] Mixed Part ] Other: Comments: ~For soldering complaint, pls attach customer's profile and solder composition~ Point of Defect [ ] Qualification [ ] Field/Warranty Defect (How long has the product been in use?): [ [ ] Reliability: [ ] Incoming [ ] Assembly ] Line / 0km (for automotive) Comments: APPLICATION NOTE ~Please note any important test, process, or usage conditions~ Defect Rate : Application : Remarks/Other Data : Notes: 1. Please attach a copy of the reel label. 2. Please take precaution against ESD and mechanical damage when forwarding samples. Revision: 28-Feb-14 Document Number: 67336 3 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET APPENDIX B VISHAY SILICONIX FAILURE ANALYSIS REQUEST FORM COMPANY INFORMATION Company Name: Contact Person: Request Reference # and Date: Adress: DEVICE INFORMATION Quantity Purchased: Quantity Returned: Failure Rate: Part Number: Geometry: Lot#: Assembly Location: APPLICATION INFORMATION Application: Time on Field: Failure Events: Number of Parts Failed: APPLICATION NOTE Total Usage in the Same Application: Failure Detection Mechanism/Code: Purpose of this Transistor in Application: Is the Application Working after Replacement of the Suspect Transistor with Another fresh Transistor? Application Details - (Electrical Schematic and Operation Parameters): Application Waveforms for Failing Parts - (VGS, VDS, ID, PD, One Complete On-Off Cycle, Zoomed at Turn-on, at Turn-off: Revision: 28-Feb-14 Document Number: 67336 4 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET VISHAY SILICONIX FAILURE ANALYSIS REQUEST FORM APPLICATION INFORMATION Application Waveforms for Good Parts: Worst Case Operating Conditions: Operating Ambient (Temperature): Board and Assembly Level Testing: Does the Customer want the Board Back after Complete Failure Analysis? Customer Comment/Suggest FA: APPLICATION NOTE Attached Documents (Electrical Schematics, Application Details, etc) Revision: 28-Feb-14 Document Number: 67336 5 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET APPENDIX C V- Example of Signals Useful for Analysis of MOSFET Behavior R1 10k 3 V- U1 2 2 V1 1 V+ 4 I R2 1.2k 12 VDC Si4948BEY 1 R4 Q1 2N2222A/ZTX V1 = 0 V V2 = 10 V TD = 0 TR = 10 ns TF = 10 ns PW = 100 µs PER = 200 µs 10k V2 V+ R3 6E APPLICATION NOTE 0 Revision: 28-Feb-14 Document Number: 67336 6 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix APPLICATION NOTE “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET Revision: 28-Feb-14 Document Number: 67336 7 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix APPLICATION NOTE “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET Revision: 28-Feb-14 Document Number: 67336 8 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET APPENDIX D Please Ignore the Voltage Values as these are for Different Circuit and Different MOSFET: Example of Fully On VGS and VDS APPLICATION NOTE Example of Turn-On Zoomed: Notice Shorter Time Scale Revision: 28-Feb-14 Document Number: 67336 9 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET Example of Turn-Off Zoomed. Notice Shorter Time Scale. APPLICATION NOTE Revision: 28-Feb-14 Document Number: 67336 10 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note AN840 www.vishay.com Vishay Siliconix “The Next Step" for Failure Analysis of Vishay Siliconix Power MOSFET APPENDIX E Example of *.CSV file (Partial Data) of the Series 1 Waveform on Right. 0 0 300 1.2E-06 9.482123 1.5E-06 2.914048 250 1.74E-06 10.84139 1.75E-06 3.895316 200 1.79E-06 10.95363 1.8E-06 3.935556 150 Series1 1.82E-06 18.09269 1.83E-06 3.124866 100 1.85E-06 11.08923 1.88E-06 3.156623 50 1.91E-06 4.024415 1.92E-06 3.182206 1.93E-06 10.41826 0 0 0.00001 0.00002 0.00003 0.00004 0.00005 0.00006 0.00007 1.95E-06 3.202057 1.96E-06 4.065218 1.97E-06 3.214845 2E-06 11.43216 2.01E-06 3.241309 2.03E-06 11.50232 2.05E-06 4.140664 2.06E-06 11.57245 2.09E-06 3.294675 2.11E-06 4.192073 2.13E-06 10.85343 2.14E-06 4.217782 2.15E-06 11.78912 2.18E-06 3.355981 2.2E-06 4.269763 APPLICATION NOTE 2.21E-06 3.376714 Revision: 28-Feb-14 Document Number: 67336 11 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000