Athira seminar
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Transcript of Athira seminar
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WELCOME
8/3/2013 DEPT ECE,SNMIMT,Maliankara 1
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SEMINAR ON
PRESENTED BY
ATHIRA M JOSHY
ROLL NO:14,S8 ECE
8/3/2013 DEPT ECE,SNMIMT,Maliankara 2
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CONTENTS
INTRODUCTION
MOISTURE MEASUREMENT INSIDE ELECTRONIC DEVICES
MOISTURE MEASUREMENT OF SKIN
BLOCK DIAGRAM
OVERVIEW
MOISTURE MEASUREMENT IN PCB
EXPERIMENTAL SETUP
MODELLING PTH AND NON-PTH IN COPPER PLANES
ADVANTAGES DISADVANTAGES
FUTURE SCOPE
CONCLUSION
REFERENCE
8/3/2013 DEPT ECE,SNMIMT,Maliankara 3
Moisture Measurement
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Moisture is the amount of water in any form in a material
It is a component of molecular makeup for all material
Excessive or deficient moisture adversely impact the physicalproperties of a material
INTRODUCTION
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Moisture Measurement
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BLOCK DIAGRAM Measurement
Primary
Air oven
Secondary
Destructive Non-Destructive
Interdigital capacitor Ultracapacitor
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Moisture Measurement
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MOISTURE MEASUREMENT INSIDE ELECTRONIC DEVICES
USING ULTRACAPACITOR
Ultracapacitor:Electrochemical capacitor with relatively high energy density
Lack of dielectric permits packaging of plates with large surface area into a given volume
Formed of ordinary activated carbon electrodes
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Moisture Measurement
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CONTD…
No liquid electrolyte exists inside the device
Electrodes are placed on both sides of a layer of porous silicon
Potassium hydroxide in powder form is embedded inside
porous silicon
Useful for monitoring moisture penetration inside small
electronic devices
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Moisture Measurement
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CONTD…
As moisture penetrates the porous silicon layer, a liquid electrolyte starts to form
Presence of moisture causes:
• Conductivity of electrolyte increases
• Hence the capacitance of the ultracapacitor increases
• Results in high capacitance
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Moisture Measurement
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CONTD…
Ultracapacitor (dry, without electrolyte) (with electrolyte)
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Moisture Measurement
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CONTD…
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Capacitance with relative humidity
(5-80)% of MC causes (0-17) μF
Moisture Measurement
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MOISTURE MEASUREMENT OF SKIN
Importance: Needed for the identification and prevention of ECZYMA
Method adopted for skin moisture measurement:capacitancemethod(Interdigital Capacitor)
Mild case of eczyma
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Moisture Measurement
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CONTD…
Stratum corneum is the outermost layer of the skin
It is composed of dead skin cells, a protein called Keratin, naturally secreted oils
Dry skin exhibits a lack of oils results in cracking of the stratum corneum
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Moisture Measurement
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CONTD…
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Stratum corneum
Moisture Measurement
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BLOCK DIAGRAM
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INTERDIGITAL CAPACITANCE
CAPACITANCE MEASURING
CIRCUIT
MICRO
CONTROLLERDISPLAY
Moisture Measurement
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CONTD…
INTERDIGITAL CAPACITOR:
IDC is the core component in capacitance method
It contains thin strips of copper
Moisture is measured as proportional increase in capacitance
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Moisture Measurement
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CONTD…
SCATTERFIELD EFFECT:
• Deviation of the linear path from one plate to the other
• Important concept in the design of an IDC
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Moisture Measurement
Interdigital capacitance
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CONTD…
CAPACITANCE MEASURING CIRCUIT:
Circuit to measure the increase in capacitance is required
“Add on capacitance meter” is used for the purpose
Add on capacitance circuit is used to identify capacitors of therange 1pF to 100pF
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Moisture Measurement
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CONTD…
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Add on capacitance circuit
Moisture Measurement
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CONTD…
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Circuit charges the test capacitor via a resistor selected by the rotary switch
Circuit charges the largest capacitor (in the range) in exactly 100 units of time
Voltmeter works only when the pin 6 of 74c14 IC is low
Voltmeter gives the reading corresponding to the test capacitance
Moisture Measurement
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CONTD…
MICROCONTROLLER :
Project incoporates AVR butterfly microcontroller
It has an ADC converter built in, labelled as Voltage V_in
Microcontroller takes data from the ADC port (V_in) and performs the conversion
It produces a value of 0 on the display when the device is turned on and IDC is exposed to air
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Moisture Measurement
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CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 21
AVR butterfly microcontroller kit
Moisture Measurement
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RESULT
SKIN TYPE VALUE DISPLAYED ON LCD
Moist skin 10-12
Normal skin 4-9
Dry skin 1-3
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CONTD…
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Complete circuit of moisture sensor
Moisture Measurement
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MOISTURE MEASUREMENT IN PCB
EFFECTS OF MOISTURE IN PCB :
Moisture reduces the quality of lamination and solder
Excessive moisture increases dielectric constant leading to changes in circuit switching speed
Ionic corrosion causes electrical open circuit or short circuit
High levels of residual moisture in PCBs causes delaminationduring soldering
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Moisture Measurement
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CONTD…
Moisture enters the PCB when the partial pressure of themoisture is greater to that inside the PCB
Focused on capacitance measurements to follow theabsorption and desorption behaviour of moisture
Capacitance is dependent on permitivity (which is dependenton moisture)
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Moisture Measurement
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DELAMINATED PCB
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Moisture Measurement
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EXPERIMENTAL SETUP
Test boards are designed with capacitors situated on inner layers between external copper planes
It is placed in 85°C and 85 per cent relative humidity (RH) environment
Moisture removal at bake temperatures of 80, 110 and 125°C is monitered
Capacitance is periodically measured at a frequency of 100 kHz
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Moisture Measurement
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(a)Test board showing plated and non-plated through holesat different densities (b) Illustration of the internal gridcapacitors
Dimensioned capacitor design
Moisture Measurement
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CAPACITANCE MEASURED
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Effect of non-PTH hole density on average capacitance decrease for the test boards baked at (a) 80°C, (b) 110°C and (c) 125°C
Moisture Measurement
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CONTD…
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Comparison of PTH and non-PTH on the capacitance decrease with bake time at 125°C for three hole densities
Moisture Measurement
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CONTD…
Average capacitance decreases more quickly for higher hole densities due to the increase in surface area
Capacitance decreases faster for boards with non-PTH such boards require shorter bake time
PTH boards have a smaller exposed surface area than non-PTH boards so moisture cannot escape so easily
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Moisture Measurement
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MODELLING PTH AND NON-PTH IN COPPER PLANES
Modelling is done to compare different moisture desorption capability of PTH and non-PTH boards during a baking
Model boards are subjected to stimulated baking
Model consisted of a PCB with a 0.4 mm hole repeated infinitely in both x and y directions and with a pitch of 4 mm
Extra model was created to represent copper planes on inner layers only
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Moisture Measurement
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CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 33
(a) Non-PTH with copper plane on outer layers, (b) PTH with copper plane on ouer layers and (c) PTH with internal copper planes
Moisture Measurement
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MODELLED MOISTURE PROFILE :
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Modelled moisture profile (a) non-PTH with copper plane on outer layers, (b) PTH with copper plane on outer layers and (c) PTH with internal copper planes
Moisture Measurement
CONTD…
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CONTD…
Dark blue colour represents saturation and light yellow as dry regions
Moisture exits non-PTH PCB model more quickly as moisture can escape more easily from the greater open surface area
For PTH board, rate of moisture loss is slower as moisture must diffuse a greater distance to find surface free from copper
For boards with internal copper planes moisture rapidly exists first,then becomes slow
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Moisture Measurement
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CONTD…
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Modelled effect of bake time on the mean moisture content in the centralregion (1 mm off the copper plane) in boards PTH and non-PTH boards.
Moisture Measurement
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ADVANTAGES
ULTRACAPACITOR SKIN MOISTURE SENSOR
Long life High accuracy
Low cost portability
Extremely low internal resistance inexpensive
High output power and Improved safety
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Moisture Measurement
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DISADVANTAGES
ULTRACAPACITOR SKIN MOISTURE SENSOR
Highest dielectric absorption Difficulty in producing the device
Low maximum voltage Not a handheld device
High self discharge
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Moisture Measurement
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FUTURE SCOPE
SCOPE OF ULTRACAPACITOR IN PACEMAKER:
Pacemaker helps to monitor and control your heartbeat
It consists of a battery, a computerized generator, and wires with sensors at their tips
Malfunction can occur if moisture happens to be inside the device
Ultracapacitor can be used inside the device to check the amount of moisture
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Moisture Measurement
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CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 40
Pacemaker implanted inside human body
Moisture Measurement
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CONCLUSION
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Food
Medicine
Industry
RELEVANCE
CONCLUSION
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Moisture Measurement
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CONTD…
A processed material's MC will define its physical properties at
all stages of processing and final product existence
Non-destructive methods are preferred and each method
discussed has specific applications
Moisture analysis means testing at the point of
processing, and making adjustments before product integrity
is effected
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Moisture Measurement
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REFERENCE
Design of a handheld skin moisture measuring device for application towards eczema, By Scott Truong
Moisture measurements in pcbs and impact of design on desorption behaviour , Chris Hunt,, National Physical Laboratory, UK
N.P. Avdelidis, P. I. Nicholson & P. Wallace, ”Pulsed thermography in the investigation of PCBs for defect detection & analysis”,
www.wikipedia.org
www.ecma-international.org
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Moisture Measurement
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Moisture Measurement
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Moisture Measurement