catalytic bead sensor yield improvement presentation
DESCRIPTION
Yield improvement on the catalytic bead sensors as a Consultant at Thermo Fisher Scientific in 2005TRANSCRIPT
Yield Improvement Project on Catalytic Bead Sensors
Dr. Rupendra M. Anklekar
November 20, 2012
Situation/Problem Statement: Thermo Fisher Scientific acquired Gas Tech Inc. in 1991
with its operations in California Moved to Franklin, MA in 2002 (consolidation) A small team trained in California before the move None of the process engineers or key people moved Erosion of the sensor manufacturing process resulting
in low yields from ~60% to 20-40% and occasionally 0-10%
Sensor business yielded highest EBITA earnings (70%) Business decision to discontinue the sensor and gas
detection products if the yields could not be improved
Reasons for Sensor Yield Loss
Sensor Technologies: Catalytic Bead (Combustible gas)
Electro-chemical (Toxic gas & Oxygen)
Thermal Conductivity (TC)
Infrared (IR)
Semiconductor (SC)
Photo-Ionization Detector (PID)
Flame Ionization Detector (FID)
Paper/Tape
Sensors for Gas Detection
Principle of catalytic bead sensor Catalytic bead sensors
Low Power – 2.0 V Medium Power – 2.2 V High Power – 6.0 V
Catalytic bead sensor comparison Voltage/current/power Process equipment Platinum wire Chemicals used Chemicals application Application – Portable or Fixed System
6.0 V sensor Yield improvement - Focus
Catalytic Bead Sensors
Consists of a very small sensing element called a ‘bead’◦ Active element (with catalyst) ◦ Reference element (no catalyst)
Made of an electrically heated platinum wire coil which acts as a temperature thermometer ◦ Active: Coated with a ceramic (Alumina) and then with a catalyst
(Palladium/Platinum) ◦ Reference: Coated with a ceramic (Alumina) and then with a glass coating &
deactivator
When a combustible gas/air mixture present◦ Active: Heat is evolved due to combustion which increases the temperature and in-
turn the resistance of the bead (TCR)◦ Reference: Since there is no catalyst there is no combustion and no resistance
change ◦ The change in electrical resistance of the active element with respect to the
reference element is measured using a standard Wheatstone bridge circuit◦ This change in resistance is directly correlated to the combustible gas concentration
and displayed on a meter or some similar indicating device
Nearly all modern, low-cost, combustible gas detection sensors are electro-catalytic bead type
Principle of Catalytic Bead Sensor
Property 2.0 Volt (Low) 2.2 Volt (Medium) 6.0 Volt (High)
Voltage 2.0 V 2.2 V 6.0 V
Current 91 mA 142 mA 242 mA
Power 0.18 W 0.31 W 1.45 W
Platinum Wire Bare Bare Alumina Coated
PlatinumAlumina
0.6 mils/15 µm Φ 1.2 mils/30 µm Φ 2.0 mils/50 µm Φ3.8-4.0 mils/95-100 µm Φ
Winder/Bonder Semi-Automatic Manual Manual
Catalyst Palladium + Platinum
Platinum Platinum
Active BeadReference Bead
40-46 Layers10-12 Layers
20-28 Layers20-28 Layers
18-26 Layers18-26 Layers
Chemicals Application
Alumina DispersionPalladium ChloridePlatinum Chloride
Ceramic Former (30%)Glass Former SolutionPlatinized Alumina Deactivator Solution
Ceramic Former (70%)Glass Former Solution
Platinum Chloride SolutionDeactivator Solution
Application Portables/Genesis Portables/Innova Fixed Systems
Catalytic Bead Sensor Comparison
Catalytic Bead Sensors & Products
GenesisInnova
Catalytic Bead Sensors
Explosion-proof Housing Polyester Housing High Temperature Housing
Fixed Systems
Portable Systems
Sensor Assembly/Test ProcessPt Coil
Weld to 2-Pin Header
Coating of Acrylic Resin in Toluene
Chemicals Application Insulation Firing
Batting/Wrap Support
Chemicals Curing
Element Matching
Weld to 3-Pin Header
Assembly in Flame Arrestor
Pre-Assembly Testing Epoxy Gluing/Curing
Final Assembly in Housing Cementing/Curing
Final Testing
Zero Drift Testing
6.0 V, 2-3 coatings20-30 min. drying
6.0 V, slow voltage ramping and soak for 1 hour
4 days
Maximum 7 boards each of Active and Reference elements and each board holding 14 elements
1 day
1 day
7-10 days
Electrical Offset – 0 +/-20 mV, IP – 5.2-5.65 V Response – 85-140 mV, Noise – </= 1 mV
Identified critical process steps for yield loss Root Cause Analysis Failure Mode Effects Analysis (FMEA) Design and Analysis of Experiments (DOE)
Developed new innovative electrical tests Used correct SPC methodology Put critical in-process specifications
Resistance, current drawn, voltage drop Coil welded to header, after chemicals application and curing
Improved design of processes /components Chemicals application Wrap support Flame arrestor
Simplified processes Removed unwanted/non-value added process steps
6.0 V Sensor Yield Improvements
Upgraded Sensor Lab equipment Improved processes
In-process controls/control plans Developed fixtures/handling aids/visual aids Camera display systems for chemicals application Assembly and test procedures Improved proper handling and packaging of sensors for shipping Identified yield loss due to sensor poisoning by silicones and
specific chemicals/solvents present in the plant Improved testing of sensors
Improved test fixtures, gas flow control and cleanliness for accuracy
Developed zero drift testing for sensor stability Hands-on training
Assembly Testing Applications
6.0 V Sensor Yield Improvements
Short circuit Overlapping coil (2.0 V & 2.2 V) Too compact coil and touching after adding chemicals Loss of insulation, cracking or breakage (6.0 V) High porosity and shorting by catalyst Wrap support touching the flame arrestor
Open circuit Broken coil Coil broken at weld joint
Catalytic bead characterization defects Too small/too large bead size Improper or no glass coverage Incorrect amount of chemicals Incorrect sequence of chemicals Improper curing of chemicals (under curing/over curing)
High electrical offset Improper welding
Unstable/drifting Test results outside specifications
Sensor Failure Mode Effects Analysis
Example: Purity of chemicals
High purity (AR grade) Certified vendors
Correct preparation of chemicals Correct weights/volumes (calibrated analytical balance,
pipettes) Correct sequence of adding chemicals (procedures, Training) No cross-contamination of chemicals (Training)
Chemicals application Correct amounts/volumes (calibrated Matrix dispenser) Correct sequence (automatic dispensing equipment,
procedures, Training) No cross-contamination of chemicals (Training)
Chemicals Application
6.0 V Sensor Process ImprovementsPt Coil
Weld to 2-Pin Header
Coating of Acrylic Resin in Toluene
Chemicals Application Insulation Firing
Batting/Wrap Support
Chemicals Curing
Element Matching
Weld to 3-Pin Header
Assembly in Flame Arrestor
Pre-Assembly Testing Epoxy Gluing/Curing
Final Assembly in Housing Cementing/Curing
Final Testing
Zero Drift Testing
Results/Conclusions: Improved the yields from as low as 20-40% to
80-95% for different sensors Improved the productivity of the Sensor Lab by
~120% for manufacturing the same volume of sensors by reducing the total staff from 12 to 5
Reduced the MRB scrap for sensors and gas detection products from >$110,000 to <$10,000 per year
Provided engineering support for $10-12 million of Industrial Hygiene business per year
Sensor Yield Improvements
Fostered team work and team building Rupendra Anklekar – Senior Project Manager/Consultant / Sensor/
Detector Scientist/Engineer / Senior Process Engineer Jeff Maybruck/Larry Fahey – Manufacturing Engineering Manager Mike Loncar - Production Manager Jayne Clarke - IH Value Stream Leader Van Krikorian/Mike Molinario - Supplier/Product Quality Engineer Brian Faulkner/Todd Muccini – Supply Chain/Materials Manager Aurora Norton/Jill Ligor – Buyer Diane Antosca – Planner Denise Whalen/Judith Lavelle - Production Supervisor Donna Lavelle/Clay Fournier/Maria Don Bourcier - Cell Leads Amy/Jane - Test Technicians Ying, Sophie, Air, Von, Noy, Sai, Seepan, Nog, Christe + 4 part-time
operators - Assembly & Testing
Cross-Functional Team Members
Open for discussion
Questions