Yield improvement on the catalytic bead sensors as a Consultant at Thermo Fisher Scientific in 2005

1. Dr. Rupendra M. Anklekar
November 20, 2012

2. 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

3. 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

4.  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

5.  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

6. 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
Platinum 0.6 mils/15 µm Φ 1.2 mils/30 µm Φ 2.0 mils/50 µm Φ
Alumina 3.8-4.0 mils/95-100 µm Φ
Winder/Bonder Semi-Automatic Manual Manual
Catalyst Palladium + Platinum Platinum Platinum
Active Bead 40-46 Layers 20-28 Layers 18-26 Layers
Reference Bead 10-12 Layers 20-28 Layers 18-26 Layers
Chemicals Alumina Dispersion Ceramic Former (30%) Ceramic Former (70%)
Application Palladium Chloride Glass Former Solution Glass Former Solution
Platinum Chloride Platinized Alumina Platinum Chloride Solution
Deactivator Solution Deactivator Solution
Application Portables/Genesis Portables/Innova Fixed Systems

7. Innova Genesis
Catalytic Bead Sensors Portable Systems
Explosion-proof Housing Polyester Housing High Temperature Housing
Fixed Systems

8. 6.0 V, 2-3 coatings
Pt Coil Coating of Acrylic Resin in Toluene
20-30 min. drying
Weld to 2-Pin Header
6.0 V, slow voltage ramping
Chemicals Application Insulation Firing and soak for 1 hour
Batting/Wrap Support
Chemicals Curing 4 days
Element Matching Maximum 7 boards each of Active and Reference
elements and each board holding 14 elements
Weld to 3-Pin Header
Assembly in Flame Arrestor
Pre-Assembly Testing Epoxy Gluing/Curing 1 day
Final Assembly in Housing Cementing/Curing 1 day
Final Testing Electrical Offset – 0 +/-20 mV, IP – 5.2-5.65 V
Response – 85-140 mV, Noise – </= 1 mV
Zero Drift Testing 7-10 days

9.  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

10.  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

11.  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

12. 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)

13. Pt Coil Coating of Acrylic Resin in Toluene
Weld to 2-Pin Header
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

14. 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

15. 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

16.  Open for discussion