Operational Field Coupled ESD Susceptibility of Magnetic Sensor IC s in Automotive Applications

Transcription

1 Operational Field Coupled ESD Susceptibility of Magnetic Sensor IC s in Automotive Applications *2014 IEEE International Symposium on Electromagnetic Compatibility, Raleigh, North Carolina Cyrous Rostamzadeh, Robert Bosch LLC USA, October 16, 2014

2 Reviewing an EMC paper.. Adobe Acrobat Document

3 Motivation and Objectives In this Work Electrostatic Discharge according to IEC Human Body Model up to ±20 kv (330 pf, 330 Ω Discharge Network) Field Coupled ESD, A Ford Test (1995). Today? Operational Field Coupled ESD, a Fiat - Chrysler Test ESD and Integrated Circuits Susceptibilities, a real possibility, it can happen!

4 Motivation and Objectives... Modern Automobile: more than 80 applications rely on Magnetic Hall-Effect Sensors (Integrated Circuits). More than 2 Billion Hall-Effect Sensors are manufactured annually. Hall-Effect Sensors in Automobiles: Safety, Power Train, Body Electronics Integrated Circuits Future: Shrinking Geometries, Wire-Bond Material Transitioning from Gold to Copper (15 μm)

5 It is important to know ESD is one of the most important Reliability problems in the Integrated Circuit Industry. ~ 50% of all Field Failures are due to ESD. It cannot be ignored!

6 Automotive World Field Coupled ESD History

7 Field Coupled ESD December 1994, Ford Principal EMC Technical Specialist, Mr. Arnie Nielsen investigated an anomaly, a bizarre behavior in a vehicle Difficult to remember, most likely it was Lincoln Town Car. The result of his research: it was an Electrostatic Discharge event, not accounted for in component-level EMC specifications. Not just like a normal ESD event, something different or more accurately, it was Field Coupled ESD phenomena.

8 February 1995: Ford EMC investigated and developed a: Magnetic-Field ESD Test Method for EMC Component-Level Test Requirements. Key-Tek (Manufacturer of ESD Gun for HBM) Developed a fixture (attached to ESD Gun for H-Field ESD Immunity test. It became part of Ford EMC Validation Requirements

9 FT-12 H-Field

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11 OEM EMC Specifications are Revised Continuously to Address Modern Vehicle Environment.

12 October 2006, Daimler-Chrysler Supplier EMC day at Chrysler Auburn Hills Update to the latest EMC Specifications: Mr. Terry North, EMC Technical Fellow: We have observed Electronic Module Malfunctions due to Indirect ESD Event As a Result, we require an additional Component-Level Test, it is called: Field Coupled ESD Test I describe today the Test Setup

13 Chrysler-Fiat Operating "Direct Coupled ESD CS11979 April 2010 ISO 10605

14 Chrysler-Fiat Operating "Field-Coupled ESD 2 X 470 kω Resistors CS11979 April 2010 ISO Discharge Islands Field Coupled Plane 5 = DUT, 6 = DUT Harness, Wiring, 11 = DUT Local Ground, 2 = Filed Coupling Strip, 7 = Battery, 8 = Peripheral and Support Equipment 9 = AN, 16 = Production intent Switches and Sensors, 4 = Isolation Block, 15 = ESD Generator Main Unit

15 Chrysler-Fiat Operating "Field-Coupled ESD CS11979 April 2010

16 Chrysler-Fiat Operating "Field-Coupled ESD CS11979 April 2010 ISO Field Coupled Plane

17 OEM ESD Test Specifications GM3097 (April 2012) Ford EMC_CS_2009 (September 2009) Chrysler CS (April 2010) ISO (2001) & IEC Standards with some Modifications. Ambient Temperature: 23 +/- 3 o C Relative Humidity 20 to 40% Prefer 20 o C and 30% RH. Contact Rise Time: t r < 1 ns Air Discharge Rise Time: t r < 20 ns. Discharge Networks: 150 pf/2 kω and 330 pf/2 kω

18 Typically OEM Requires: ESD Handling Unpowered ESD Powered, Remote Input/Output Examples

19 CI 280 Handling Unpowered

20 7.1 Handling Unpowered

21 3.6.5 Handling Unpowered

22 Magnetic Sensor Integrated Circuits in Automotive Applications

23 Modern Automobile & Hall Effect Sensor Applications

24 Automotive DC Motor with Hall-Effect Sensor Schematic C1

25 Hall-Effect Sensor IC

26 Test Setup

27 Pre-Field-Coupled ESD Hall-Sensor Output Hall Sensor Output (Horizontal 5 sec/div. Vertical 10 Volt/div), 100 Hz.

28 Post-Field-Coupled ESD (±15 KV)Hall-Sensor Output Hall Sensor Output (Horizontal 5 sec/div. Vertical 10 Volt/div). 100 Hz

29 At (±20 KV Field-Coupled ESD) Complete Loss of Hall-Sensor Output Signal! Corrupted Sensor Output Signal ±15 KV, incrementing at 1KV above ±15 KV - Output Signal Degrades Gradually, Worsens - Resulting in a large DC Offset Voltage. Finally, Complete Loss of ±20 KV. Resulting in Permanent Damage to Device.

30 Monitoring Field Coupled to DUT

31 Magnetic Field Coupling Magnetic Field Coupling, Horizontal scale: 5ns/div, Vertical scale: 500mV/div

32 Pre-ESD, Post-ESD Impedance Characteristics

33 Impedance Characterization

34 Impedance Characterization C1 10 nf MLCC

35 Pre-ESD, Post-ESD Hall-Sensor IC Imaging Inspection

36 Pre-ESD Hall Effect Sensor IC Post-ESD Bond-Wire Defect

37 ESD Observations

38 We can ESD see in action! ESD when applied to 0603 MLCC (Multi-Layer Ceramic Capacitor - X7R)

39 ESD Causes Physical Damage, you can see it!

40 ESD Causes Permanent Damage! When you look at its Electrical Characteristics Pre-ESD, Post-ESD 600 Ω R Behavior

41 A Discharge Voltage < 3500 Volts Cannot be felt by the person involved. Semiconductor devices fail at 100 s of Volts!

42 ESD Impact

43 IC s fail due to Excessive Voltage or Energy Excessive Voltage can cause Dielectric Breakdown in IC s such as Oxide Barriers.

44 Excessive Energy can cause Thermal Failure by Melting Silicon or Metallization of IC. Melting Temperature of Silicon ~ 1,420 0 C Melting Temperature of Metallization ~ C

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46 ESD Voltages as high as 30 kv has been observed in automotive environment.

47 ESD is rich in High- Frequency (> 3 GHz)!

48 ESD event can create Currents in Excess of 30 Amps!

49 ESD currents can destroy IC s, PCB traces and other Components!

50 ESD can create timevarying Magnetic Field: 25 Amp/m

51 ESD can create timevarying Electric Field as high as 10 kv/m

52 ESD can create Susceptibility Problems.

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56 ESD phenomena involves Electrical & Thermal Transports on the Scale of nanometers (nm), Circuits and Electronics on the Scale of micrometers (μm), Semiconductor Chip designs range from picoseconds (ps) to microseconds (μs), Electrical Currents of interest range from ma to 10 s of Amperes. Voltages range from Volts to kilovolts (kv). Temperatures vary from room temperature to melting temperatures of 1000 s 0 K

57 Must Quantify the Scale in Space & Time ESD phenomena involves: Microscopic to Macroscopic Scales. ESD is a Thermo-Electric Transport of Material Physics

58 Human Body ESD HBM

59 Capacitance ESD Charge Storage Element

60 Charge Storage Capacitance C = 1 r 1 4 πε 1 r 2 r 1 r 2 if r 2 C =, ( 111 r) diameter sphere, and for free space, ε = pf, a human has a surface area to1 meter C Human Body pf 12 F / m

61 = = = = = = = = = = = , rˆ 4, 4, 2 1 r r C CV Q r r Q dr E V r Q E Q E r ds E E E D Q dv ds D r r s r v s πε πε πε πε ε ε ε ρ v v v v v v v v v v v Starting with Guass s Law

62 Free-Space Capacitance Human Body Capacitance Earth s Capacitance An object a size of marble 50 pf 700 μf 1 pf In addition, we must consider Parallel Plate Capacitance due to the proximity of an object to the surrounding

63 Human Body Self-Capacitance 50 pf 25 kv NP

64 Human Body Model (HBM)

65 Human Body Energy Storage The human body is an Electrical Conductor, full of Salty Fluids. Like any Conductor, the human body has a Capacitance, i.e., it stores Electrical Energy, with respect to its surroundings, such as the floor, the walls, or other people

66 Human Body Energy Storage a person's Capacitance is one of his or her body's attributes. Human attributes can be affected by the surroundings. a person's Capacitance depends on many factors, including it's Posture, its Relative Position, and its Proximity to other Electrically Conducting Objects.

67 Human Body Model (HBM) Therefore, the Capacitance of a Human Body is the Combination of Free-Space Capacitance + Parallel-Plate Capacitance and can vary from 50 pf to 250 pf

68 Human Body Model (HBM) V HB C R V HB HB HB = 50 = 500 = 0 to 250 pf Ω kv kω

69 Human Body Model (HBM) For a Human Body of 100 pf Capacitance, Charged Up to 25 kvolt, Energy Released Per Discharge. Energy Energy = CV 2 30 mj = (25,000)

70 Human Body Model (HBM) The Discharge of a Human (via a small, hand-held metal piece) is basis for the current waveform most often used IEC standard.

71 ESD Mathematical Analysis

72 + + + = exp 1 exp 1 ) ( τ τ τ τ τ τ t t t k i t t t k i t i n n n n, exp 1/ = n n k τ τ τ τ = n n k 1/ exp τ τ τ τ I 1 = 21.9 Amp τ 1 = 1.3 ns τ 3 = 6 ns n = 3 I 2 = 10.1 Amp τ 2 = 1.7 ns τ 4 = 58 ns

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75 HBM ESD Time Constant τ τ HB HB = = R HB C HB 1500 Ω 100 pf = 150 ns Similar to Thermal Diffusion Time of many materials used in semiconductor industry

76 ESD is a Non-Linear Electro-Thermal Physical Event. Very Difficult to Model Accurately. Simple Linear Model is insightful.

77 ESD Modeling

78 ESD Generator Model

79 ESD Generator Model V Gen = 8 kv

80 ESD HBM Model V HBM = 25 kv

81 ESD HBM Model V HBM = 25 kv

82 ESD Protection Schemes

83 ESD Protection Devices 1. TVS (Transient Voltage Suppressor) 2. MOV Multilayer Zinc Oxide 3. Diode 4. Capacitor 5. Spark Gap 6. Filters 7. Ferrites

84 ESD Strategies Avoid Direct Connection from an exposed external point to an Integrated Circuit. E ~ 30 mj

85 ESD Strategies In no case should there be a direct connection from an Integrated Circuit to an exposed external point.

86 ESD Strategies Divert or limit the ESD Energy away from Circuit Inputs using Filters or Transient Suppressors.

87 ESD Capacitor Mounting Strategy How far from Connector Pin PCB layer stack up Y-Connection

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89 ESD Strategies Solution IC absorbs a small % of ESD Current! I HF

90 ESD Frequency ~ 3 GHz Fast Transient Electromagnetics Field Collapses to V within 50 ps 5 ns Structure Electrically Large l > λ

91 High Frequency Design Practice ESD

92 Conclusion Potential Destructive Damage to Integrated Circuit due to Field Coupled ESD may occur. The failure mechanism was investigated and explored. Coupling Fields may induce device latch-up. Miniaturization, die-shrink and Transitioning bond-wire Material (from Gold to Nickel Palladium, Copper) may introduce immunity concerns which may have not existed for older generation devices. Field Coupled ESD appears to be a good (critical) test, correlating well to real-world scenarios. Further OEM (Ford, GM) research is needed!

93 Thank you for your Participation