Date post: | 04-Aug-2015 |
Category: |
Education |
Upload: | ninnuathi91 |
View: | 83 times |
Download: | 0 times |
WELCOME
8/3/2013 DEPT ECE,SNMIMT,Maliankara 1
SEMINAR ON
PRESENTED BY ATHIRA M JOSHY ROLL NO:14,S8 ECE
8/3/2013 DEPT ECE,SNMIMT,Maliankara 2
MOISTURE MEASUREMENT
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
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 physical properties of a material
INTRODUCTION
8/3/2013 DEPT ECE,SNMIMT,Maliankara 4
Moisture Measurement
BLOCK DIAGRAM Measurement
Primary
Air oven
Secondary
Destructive Non-Destructive
Interdigit
al capacitor
Ultracapacitor
8/3/2013 DEPT ECE,SNMIMT,Maliankara 5
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 6
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 7
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 8
Moisture Measurement
CONTD…
Ultracapacitor (dry, without electrolyte) (with electrolyte)
8/3/2013 DEPT ECE,SNMIMT,Maliankara 9
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 10
Capacitance with relative humidity
(5-80)% of MC causes (0-17) μF
Moisture Measurement
MOISTURE MEASUREMENT OF SKIN
Importance: Needed for the identification and prevention of ECZYMA
Method adopted for skin moisture measurement:capacitance method(Interdigital Capacitor)
Mild case of eczyma
8/3/2013 DEPT ECE,SNMIMT,Maliankara 11
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 12
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 13
Stratum corneum
Moisture Measurement
BLOCK DIAGRAM
8/3/2013 DEPT ECE,SNMIMT,Maliankara 14
INTERDIGITAL
CAPACITANCE
CAPACITANCE
MEASURING CIRCUIT
DISPLAY
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 15
Moisture Measurement
CONTD…SCATTERFIELD EFFECT:
• Deviation of the linear path from one plate to the other • Important concept in the design of an IDC
8/3/2013 DEPT ECE,SNMIMT,Maliankara 16
Moisture Measurement
Interdigital capacitance
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 the range 1pF to 100pF
8/3/2013 DEPT ECE,SNMIMT,Maliankara 17
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 18
Add on capacitance circuit
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 19
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
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 20
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 21
AVR butterfly microcontroller kit
Moisture Measurement
RESULT
SKIN TYPE VALUE DISPLAYED ON LCD
Moist skin 10-12
Normal skin 4-9
Dry skin 1-3
8/3/2013 DEPT ECE,SNMIMT,Maliankara 22
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 23
Complete circuit of moisture sensor
Moisture Measurement
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 delamination during soldering
8/3/2013 DEPT ECE,SNMIMT,Maliankara 24
Moisture Measurement
CONTD…
Moisture enters the PCB when the partial pressure of the moisture is greater to that inside the PCB
Focused on capacitance measurements to follow the
absorption and desorption behaviour of moisture
Capacitance is dependent on permitivity (which is dependent on moisture)
8/3/2013 DEPT ECE,SNMIMT,Maliankara 25
Moisture Measurement
DELAMINATED PCB
8/3/2013 DEPT ECE,SNMIMT,Maliankara 26
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 27
Moisture Measurement
8/3/2013 DEPT ECE,SNMIMT,Maliankara 28
(a)Test board showing plated and non-plated through holes at different densities (b) Illustration of the internal grid capacitors
Dimensioned capacitor design
Moisture Measurement
CAPACITANCE MEASURED
8/3/2013 DEPT ECE,SNMIMT,Maliankara 29
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
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 30
Comparison of PTH and non-PTH on the capacitance decrease with bake time at 125°C for three hole densities
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 31
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 32
Moisture Measurement
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
MODELLED MOISTURE PROFILE :
8/3/2013 DEPT ECE,SNMIMT,Maliankara 34
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…
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 35
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 36
Modelled effect of bake time on the mean moisture content in the central region (1 mm off the copper plane) in boards PTH and non-PTH boards.
Moisture Measurement
ADVANTAGES
ULTRACAPACITOR SKIN MOISTURE SENSOR
Long life High accuracy
Low cost portability
Extremely low internal resistance inexpensive
High output power and Improved safety
8/3/2013 DEPT ECE,SNMIMT,Maliankara 37
Moisture Measurement
DISADVANTAGES
ULTRACAPACITOR SKIN MOISTURE SENSOR
Highest dielectric absorption Difficulty in producing the device
Low maximum voltage Not a handheld device
High self discharge
8/3/2013 DEPT ECE,SNMIMT,Maliankara 38
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 39
Moisture Measurement
CONTD…
8/3/2013 DEPT ECE,SNMIMT,Maliankara 40
Pacemaker implanted inside human body
Moisture Measurement
DEPT ECE,SNMIMT,Maliankara 41
CONCLUSION
8/3/2013
Food
Medicine
Industry
RELEVANCE
CONCLUSION
7/2/2013 DEPTOF ECE,SNMIMT,Maliankara 42
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 42
Moisture Measurement
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
8/3/2013 DEPT ECE,SNMIMT,Maliankara 43
Moisture Measurement
8/3/2013 DEPT ECE,SNMIMT,Maliankara 44
THANK YOU…
Moisture Measurement
8/3/2013 DEPT ECE,SNMIMT,Maliankara 45
QUESTIONS???
Moisture Measurement