Leveraging Existing Market Knowledge to Ensure a Successful Transition to Pb-Free Medical Products Randy Schueller, Ph.D. & Cheryl Tulkoff DfR Solutions Outline Intro Medical Electronics Testing Reliability Testing to Identify Common Pb- free issues.
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Leveraging Existing Market Knowledge to Ensure a
Successful Transition to Pb-Free Medical Products
Randy Schueller, Ph.D. & Cheryl Tulkoff
DfR Solutions
Outline
Intro
Medical Electronics Testing
Reliability Testing to Identify Common Pb-free issues.
Medical Electronics – Very diverse!
What are ‘medical’ electronics? Is it a realistic category?Some implanted in the body; some outside
Some portable; some fixed
Some complex; some simple
Some control; some monitor; some medicate
All connected by the perception that one’s life may be dependent upon this productCreates a powerful emotional
attachment/effect
Assuring reliability becomes critical
Pb-Free Medical Electronics
A main question is “What can we learn from other Pb-free electronics that will help us most effectively test medical electronic devices as we transition to Pb-free?
Types of Testing
First we should understand that there are different types of testingFeasibility (or Functional) Testing
V&V: Validation & Verification
Production Testing
Reliability Testing
Safety / Regulatory Testing
Feasibility or Functional Testing
Feasibility TestingFunctional testing – confirm that design meets
basic performance requirements
Is it possible?
Proof of concept
Does it work
Failures undesirable
V & V Testing
V&V: Validation & Verification Conformance to specifications & standards
Industry standards like IPC, JEDEC, ISO, FDA, IEC
Environmental Testing
Failures Undesirable
Production Testing
Production TestingStatistical
Optimize design & manufacturing
Failures undesirable
Reliability Testing (our focus)
Two primary objectives:
1. Prove the product can withstand the environment it is going into.ATC, S&V, THB, Heat age, etc.
2. Reveal any weaknesses (in design or process) so risks can be accessed and improvements made. HALT, ESS, Analytical techniques
Some failures are expected.
Safety Testing
Safety / RegulatoryMay overlap with some others
Some fails may be desirable
Varies based on industry
Key Elements of a Product Reliability Plan Reliability Requirement & Targets
Reliability Organization Structure
Reliability Activities (Reports, Tests, Analyses)
Schedule
Supply chain management /oversight
Listing of relevant standards, specifications, procedures
General Reliability Management Needs Create & work to reliability plan
Define and Identify external servicesTest
Failure Analysis
Reliability Training
How to ID the Best Reliability Tests Key Points:
Must test at increased stresses, not actual expected stresses, to create failures then use this information to improve reliability Only true upper stress limits for reliability testing are test
Optimum flux Acids are neutralized after soldering process
Residual wetting agents are minimized
Cleanliness Controls: Ion Chromatography
Contamination tends to be controlled through industrial specifications (IPC-6012, J-STD-001) Primarily based on original military specification
10 g/in2 of NaCl ‘equivalent’ Calculated to result in 2 megaohm surface insulation resistance (SIR) Not necessarily best practice
Best practice is contamination controlled through ion chromatography (IC) testing IPC-TM-650, Method 2.3.28A
*Based on R/O/I testing
PaulsGeneral Electric
NDCEE DoD* IPC* ACI
Chloride (g/in2) 2 3.5 4.5 6.1 6.1 10
Bromide (g/in2) 20 10 15 7.8 7.8 15
Sources of Contaminants (cont.)Ion Possible Sources
Cl Board Fab, Solder Flux, Rinse Water, Handling
Br Printed Board (flame retardants), HASL Flux
Fl Teflon, Kapton
PO4 Cleaners, Red Phosphorus
SO4 Rinse Water, Air Pollution, Papers/ Plastics
NO4 Rinse Water
Weak Organic Acids Solder Flux
High Temperature Products
Medical equipment that runs hot will require forced air cooling.
If Immersion silver surface finish is used then creep corrosion should be evaluated with corrosion testing.
Plated through-hole vias can fracture so should be tested (IST, Thermal cycle, etc.)
Creep Corrosion of ImAg Copper sulfide grows in the presence of
sulfur compounds.
Greatly enhanced with airflow bringing in S containing gasses and particulates
Summary
Reliability testing of Pb-free products should take into consideration the various defects and failure mechanisms that have been associated with this change.
Stress tests and failure analysis techniques should be designed to explore these known mechanisms to ensure sufficient robustness is designed into the products.