The document summarizes efforts to improve production yields for catalytic bead gas sensors from 20-40% to 80-95% after the manufacturing process was moved. Critical process steps were identified and improved through tools like root cause analysis and design of experiments. Process upgrades like chemical application methods and quality controls helped address defects. Testing procedures were enhanced and hands-on training provided. The changes reduced scrap and improved productivity while supporting $10-12M in annual business.

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