GE Healthcare Submission to the DG Environment Review of Directive 2002/95/ECof the European Parliament and of the Council on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (“RoHS”)

Date: May 25, 2007

To: DG Environment ()

GE Healthcare thanks the Commission for the opportunity to contribute to the review of the RoHS Directive concerning new scientific evidence, in particular with regard to the inclusion of additional categories of equipment in the scope of the Directive. GE Healthcare believes that it is critical to insure the safety and reliability of its products and provides the enclosed reliability test data of lead free soldiers in critical applications used in Medical Devices for your consideration.

In addition to the data presented below, GEHC has extremely strong technical cases which demonstrate catastrophic reliability failures which we would like to share with the Commission. Please let us know if you would like to review these compelling cases and if there is a process in place to ensure the confidentiality of the GEHC test results. We look forward to providing the additional data to you.

Sincerely,

Beth A. Hulse

GE Healthcare

Global Regulatory Manager-Environmental Products

262 548 2267

Summary

GE Healthcare is a core GE business providing transformational medical technologies that are shaping a new age of patient care. GE Healthcare’s expertise in medical imaging and information technologies, medical diagnostics, patient monitoring and life support systems, disease research, drug discovery, and biopharmaceutical manufacturing technologies is helping physicians detect disease earlier and to tailor personalized treatments for patients. GE Healthcare provides products and services that are improving productivity in healthcare and enhancing patient care by enabling healthcare providers to better diagnose and treat cancer, heart disease, neurological diseases, and other conditions.

Headquartered in the United Kingdom, GE Healthcare is a unit of General Electric Company. Worldwide, GE Healthcare employs more than 43,000 people committed to serving healthcare professionals and their patients in more than 100 countries.

GE Healthcare is committed to serving the communities where we do business, to providing our customers with innovative, high-quality products and services, and to protecting the health of our workers and the environment. GE Healthcare believes that it is critical to continue the exclusion of medical devices to insure the safety and reliability of the products. The following points summarize and support the request for the continued exclusion of category 8.

  • Materials are chosen for their desired performance and reliability characteristics, alternatives may not perform as well and need to be thoroughly evaluated before any change is incorporated.
  • The key is that the reliability of Medical Devices is of the highest level of importance to insure the safety of the patient and clinicians. We must thoroughly evaluate material, process or technology changes to minimize risk to the health and safety of the patient and clinicians.
  • Medical devices are manufactured in low volumes and their usage does not compromise the communities’ objective of protecting health and the environment
  • For environmental considerations, GE Healthcare has established take back systems to carefully dispose of or recycle medical devices at their end of life, thereby reducing environmental aspects.

Unique Aspects of Medical Devices

  • Device Complexity

Most Medical Device products, particularly diagnostic imaging and treatment systems, are significantly more complex in design and function compared to consumer products. Similar to aerospace products in this aspect, the opportunities for failure are far more numerous than the consumer segment.

For example, the GEHC Lightspeed Volume CT scanner utilizes over 200 individual circuit boards totaling over 50,000 cm2 area that contain more than 200,000 vias, more than 75,000 electronic components and over 500,000 soldered interconnections.

  • Sensitivity & Dynamic Range of Controlled Energies

Detection sensitivity and the precise control of high power energy sources sets them apart from other product families. For example in a multislice CT scanner or Vascular X-ray system, the X-ray generator and tube may be converting 100KW of instantaneous electrical power into X-ray photons while the detector, about 1 meter away, is quantizing charge levels as small as a few hundred electrons per bit at a rates upwards of 50 MHz.

  • Operating Environments

Operating environments for diagnostic imaging systems can vary widely, which can greatly affect system reliability. Stress factors which can be present in much higher concentration than consumer devices in certain applications include;

  1. Mechanical Shock and Vibration
  2. Long Term G Force Centrifugal Loading
  3. High Magnetic Fields
  4. Ionizing X-ray Energy
  5. Ultrasonic Energy
  6. Chemical stresses including contrasts, cleaners and antibacterial agents
  7. Long term industrial contaminants such as dust and dirt particulates

Attached is a paper prepared by GE Healthcare which has supporting data and test results summarizing reliability issues with lead free alternatives.

Study Summary of RoHS Compliant Electronic Assembly Challenges

By Ashitosh Joshi, Jason Griesbach, Brian Graves, & Jeff Kautzer of GEHC

Executive Summary:

For electronic assemblies that are required to be of high reliability such as those utilized for Medical Devices, there are several areas of risk that the industry is unlikely to sufficiently mitigate until well after the possible inclusion date of category 8 equipment. This paper highlights the two lead-free technologies generally available for circuit board assembly and serves to summarize some of the published studies that have been conducted to evaluate. In most cases, issues raised within each of these studies have been summarized along with photo illustrations where possible.

The alternative lead-free technologies studied have characteristics as summarized below.

  1. SnAgCu Based Lead Free (LF) Solders:
  • Dissolves copper pads when solder is applied to plated thru-holes (1)
  • Risk from whisker growth (11), (12)
  • Higher process temperatures pose risk to fabs, vias, pads, components (9), (16), (18), (20)
  • Shows decreased reliability in reworked and neighboring ceramic BGAs (1)
  • LF solder is more brittle and prone to mechanical damage (1), (6), (7)
  • Interaction between long term mechanical, thermal stress (17), (18)
  • LF solder shows high infant mortality (5)
  • LF solder has many (unknown) process dependencies (7)
  • LF solder may exhibit interface voiding that grows with aging, leading to brittle joints (6), (7)
  • Increased risk of brittle intermetalics (8), (10)
  • Some do not consider LF solder acceptable for military or mission-critical applications (5)
  • Lack of long term field data (17)
  • May be difficult to evaluate using conventional stress accelerations (23)
  • May not be suitable for high reliability applications (23)
  • LF solder processes must be evaluated for process defects such as voiding, wetting and their effect on overall long term reliability (22)
  1. Metal Loaded Conductive Epoxies (CE)
  2. Has been known to cause galvanic corrosion with tin platings, although this may now be a solved issue (3)
  3. LF solder is normally preferred (3)
  4. Conductive epoxy is not reworkable.

References:

1) Pb-free Assembly, Rework, and Reliability Analysis of IPC Class 2 Assemblies: Gleason, J et al. Electronic Components and Technology, 2005. ECTC '05. Proceedings

31 May-3 June 2005 Page(s):959 – 969.

Issues:

  • SAC solder dissolves copper pads and barrels on thru-hole vias.
  • Decreased reliability on reworked CBGAs on 0.135” boards.
  • Small reliability impact on board thickness for .093” and 0.135” boards.
  • High failure rate in adjacent CBGAs during rework.
  • Better thermal cycling reliability on lead-free from 0C to 100C.
  • Load force to failure of 4-pt bend is half for SAC vs SnPb.

2) Avoiding Tin Whisker Problems: Galyon, G.T., Gedney, R. Circuits Assembly, August 2004, pp 26-31.

Issues:

  • Whisker growth is accelerated by thermal cycling and mechanical fatigue.

3) Cure Processing Effect on Conductive Epoxy Adhesives as Solder Alternatives: Ceramic Applications: Smith, S. et al. SMTA conference proceedings, 2003.

Issues:

  • Conductive epoxy silver causes galvanic corrosion with tin platings, but this may be a solved issue.
  • There are situations where mfg houses will employ conductive epoxy instead of solder, such as to avoid temperature extremes.

4) Interface Description and Failure Mechanism of SnAgCu Solders in BGA Packages: Albrecht, H.J. SMTA conference proceedings, 2004.

Issues:

  • LF solders have more potential for intermetallics which can affect reliability.

5) Impact of Underfill and Solder Joint Alloy Selection on Flip Chip Solder Joint Reliability: Hillman, D., Wilcoxon, R. SMTA conference proceedings, 2004.

Issues:

  • On underfilled flip chips, thermal cycle –55 to +125C, lead free solder failed in far fewer cycles than eutectic tin lead.
  • Underfill type also made significant impact on reliability.
  • Lead free solders had initial high probability of failure, but decreased with time, indicating infant mortality due to solder characteristics, not mfg defect. Leaded solder failure probability increased with time, indicating wear-out.
  • Rockwell did not consider LF to be adequate for military or high reliability, mission critical assemblies.

6) Fragility of Pb-Free Solder Joints. Universal Instruments technical publication, 2004.

Issues:

  • Interface voiding, accelerated by temperature, grows with time resulting in joint brittleness.
  • Black pad phenomenon may be exasperated by lead free solder.

7) Lead-free Rework Process for Chip Scale Packages: Gowda, A., Srihari, K., Primavera, A. Universal Instruments technical publication.

8) Lead Free Assembly Reliability Concerns: Borgesen, P. Universal Instruments presentation to GE Global Workshop, October 2005.

Issues:

  • Lead free has lots more occasional “surprises” and interdependencies that didn’t matter in leaded processes.

9)Materials for Lead Free assembly (Merix presentation: SMTA meeting March 16, 2005)

Issues:

  • Elevated reflow temperatures (230C vs. 260C) threaten through hole (PTH) reliability and increased risk for delamination
  • Higher aspect ratios increase reliability concerns (high Tg material with low CTE required for high temperature excursion)
  • Higher layer count boards have problem of greater temperature gradient in board causing problem of warpage
  • Surface finishes of board is another major issue of lead free boards

References:

“Effect of NEMI SAC alloy assembly reflow on plated through hole performance” by John J Devignon et al Merix Corporation

“An assessment of the impacts of Lead-free assembly process on base material and PCB reliability” by Edward Kelly, Cookson Electronics

10)NIST Research in NIST Research in Lead-Free Solders: Lead-Free Solders: Properties, Processing, Reliability (Presentation by Carol Handwerker, National Institute of Standards and Technology (NIST)

Issues:

  • Fillet Lifting in High Tin Content Solder
  • Separation between intermetallic and solder

11)Tin Whisker Test Committee Results (Phase 3) (NEMI)

Issues:

  • Tin whisker growth for Sn related finishes
  • Temperature and humidity enhances Tin whisker growth
  • High whisker growth for Sn finishes
  • Localized corrosion and whisker presence at high temperature & humidity
  • Lead-free finishes have larger whisker growth then Pb-Sn for all conditions (pp68)
  • Conflict in data from different research groups on whisker growth

12)Evaluation of Conformal Coatings as a Tin Whisker Mitigation Strategy

Thomas A. Woodrow, Eugene A. Ledbury: The Boeing Company

Issues:

  • Coatings penetrated by the whiskers
  • Thin coatings are easily penetrated on long term
  • No correlation between material properties and growth suppression capability
  • Thick coatings (4-6 mils) have no penetration and are low cost

13)Calibration of Virtual Qualification Model for Leaded Packages with Pb-free Solder

(B. Han: CALCE Univ. of Maryland)



Issues:

14)The hidden challenges of manufacturing Lead-free Electronics (Melissa E. Grupen Shemansky and John W. Osecbach of Agere Systems): Website


Issues:

15)Rockwell Collins and Pb free Soldering Processes (Presentation: David Hillman)

Issues:

  • ACF bonding using Sony ACF bonding tape (6 years history)
  • Printed Wiring board finishes

16)Challenges in Manufacturing Reliable Lead Free Components

White paper by Altera

Issues:

  • Extended moisture exposures at elevated reflow temperatures
  • Package warpage due to higher moisture absorption
  • Die surface delamination for larger packages
  • Higher MSL (military) qualification required for packages

17)Assessment of long term reliability of Lead free assemblies

S. Ganesan et al. (CALCE)

Issues:

  • Short term data exists for single loading condition but long term (>5years life) reliability data is not available
  • Tin whiskering for peripheral lead-free components (no long term data)
  • Intermetallic compound at pad finishes (could have effect on fatigue life under vibration)
  • Solder lift-up at fillet
  • Combined reliability loading (mechanical+ thermal cycling) data for long term required  interaction of different loading needs to be understood

18)Key concerns in lead free assemblies S. Ganesan et al, CALCE

Issues:

  • Part terminal finish
  • Component moisture and temperature sensitivity (Organic compounds MSL ratings to go down for every 10C rise)
  • Passive components (flexture induced damage)
  • PCB laminate material to withstand reflow and high PTH life
  • No flame retardant (PBBs halides)
  • Lead contamination could cause fillet lifting at high temperature

19)Characterization of Anisotropic conductive adhesive: By A. Dasgupta, CALCE, UMD

Issues:

  • Loss of compressive residual stress caused by epoxy curing after temperature cycling

20)Has Electronics Industry missed the boat on Pb-free? Failures in ceramic capacitors with Pb-free solder interconnects: N. Blattau and C. Hillman, CALCE, UMD

Issues:

  • Allowable board flexure reduce due to higher temperatures
  • Flex cracks due to bending of PCB during manufacturing process (higher melting point of solder)


  • To maintain 0.01% failures: 25% reduction in board curvature for Pb-free boards

21)Stud Bumps in Flip chip application: Jerry Jordan of Palomar Technologies

Issues:

  • Very few manufacturers in this area
  • New alternate technology to solder joints for flip chips
  • Underfill material necessary for structural integrity
  • Bump height inconsistencies can lead to die fracture or open circuit

22)GEHC-Universal Instruments Test Report M00263642: SAC305 test board report

Issues:

  • IPC classified solder joints autopsied
  • SAC305 processes sensitive to voiding and wetting issues
  • Degradation in thermal cycle reliability

23) Reliability of Lead Free (LF) Solder Joints Revisited: Global SMT & Packaging Nov 2003 - Engelmaier

Issues:

  • Creep rates of LF solders are ~100X slower than SnPb eutectic
  • Lack of acceleration profiles taking into account creep rates
  • Usage of LF solder in high reliability applications is questioned

1