March 2003 Tire Expo Hamburg DownloadLink 3886

Low Cost integrated Package for
Tyre Pressure Monitoring Systems
A.J. van der Wiel
Melexis
Outline
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Tyre Pressure Monitoring Systems
System Requirements
The Sensor
The ASIC
Why MCM Integration
The Package
Melexis’ Package Integration Process
Measured Characteristics
Outlook
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TPMS
• Stand-alone system
• Tyre Environment
• Large temperature range
• High acceleration forces
• Wireless data transfer
• Calibrated system
• 10 year operational
• System components
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Pressure sensor
Temperature sensor
Roll sensor
Read-out electronics
RF and/or LF transmitter
Battery
Passive components
System Requirements
• Functionality
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3% Accuracy
-40 °C to 125 °C
0 – 1500 g centrifugal forces
High moisture and solvent environment inside the tyre
10 year operational on 1 battery
• Programming
• Calibration
• Timing constants
• Identification
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The Sensor
• Silicon chip ~1.0 x 1.0 x 0.5 mm2
• Integrated Strain Gauges as Wheatstone bridge
• All silicon for excellent drift behaviour
The Asic
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0.6u cmos process
Double poly - double metal
ROM - RAM - EEPROM
Flash memory for software development and limited
production
• On chip active/passive LF interface (receive)
• Power supply range: 1.8 to 5 V
• Temperature measurement
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Why MCM Integration
• Minimising number of components
• Cost saving
• Smaller product
• Better reliability
• Sensor calibration before system assembly
• Sensor characteristics stored in ASIC
• No temperature ramping after final assembly
The Package: Requirements
• Low Cost - High Volume production
• SOIC compatible
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MCM package
Expose sensor to pressure
Minimal stress at sensor
Low g sensitivity
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The Package: Assembly Process
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Die attach dispense on lead frame
Pick and place die on lead frame
Bake
Wire bond
Protective Gel dispense
Bake
Mould
Singulation
The package X-ray graps
FluoroGel protection
• Resist solvents and high temperature range
• No offset change after gel removal
• Thin gel layer assures small g sensitivity
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Characteristics
Parameter
Unit
MLX90268
On the market
Sensitivity
mV/V/Bar
3
3
Offset
mV/V
±5
± 10
Linearity
%FS
0.2
0.2
Hysteresis
% FS
0.1
0.1
k
42
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TC Sensitivity
%FS/°C
-0.2
-0.2
TC Offset
%FS/°C
± 0.03
± 0.04
Acceleration error
mBar/g
< 0.05
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kV
2
2
Bridge Resistance
ESD
Conclusions
• MCM with sensor and ASIC reduces:
• Number of components final product
• Size of final product
• Test and calibration of final product
• Packaging is the key to System Integration
• Realisation of a MCM with sensor and ASIC
• TPMS requirements met by adding a gel dispense
to standard SOIC packaging
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Questions and comments please!
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