1. Intermetallic Issues With Wire Joining by Thermocompression & Soldering Dr Henning Leidecker Goddard Space Flight Center, Code 562 Parts, Packaging, and Assembly Technologies Office Henning.W.Leidecker@nasa.gov 301-286-9180 21 Oct 2003

2. Outline Wire Bonding Au-Al Intermetallics – Equil. Intermetallics – Rates Degradation/Failure GFSC Websites Wire Soldering Au-I Intermetallics – Equil. Intermetallics – Rates Degradation/Failure GSFC Websites

3. But first, a bit about COTS... The Commercial Off-The-Shelf (COTS) market is huge and competitive: the stakes are high. Hence, some of the best designers in the world develop COTS parts, sharply focused on a target market. Often, they hit this market with exquisite precision. But trade-offs are usually made in this target-focused design, and the resulting parts may not be apt for a different market whose needs differ from the target. Reliability over long times (5+ years) is a prime example. ==> DO NOT FEAR COTS BUT BE WARY <==

4. Gold-Indium Phase Diagram

5. Optical Cross-section of a ball bond

6. SEM – intermetallic at base of bond

7. SEM – cross section

8. Note Cracks

9. Familiar Intermetallic?

10. Carbon Exuding From Grain Boundaries

11. Intermetallic Remaining

12. Normal and Carbon-Sensitive Images

13. GSFC Websites about this topic NASA/GSFC Wire Bond Website: Selected Topics of Interest to GSFC Parts http://nepp.nasa.gov/wirebond/Index.htm Richard Katz Website: http://klabs.org/richcontent/fpga_content/pages/notes/fpga_reliability.htm Pay special attention to Horsting's work on the effects of impurities on the bonding pad; see also Issues with Gold Electroplating for Microelectromechanical Systems Applications, by C. A. Kondoleon, et al. Materials Research Society Symposium Proceedings 2002, 687 (143--148)

14. Indium Solder and 1 mil Gold Wires Before there was wire bonding (e.g., thermocompression), there was soldering Pb-Sn solder dissolves gold; not good for 1 mil. About early 1950's, Indium was used to solder thin gold wires --- Initial success, followed by high frequency (--> 100%) of the joins breaking. The short-term attractiveness of Indium as a solder induces repeated lessons learned!

15. Wedge Bond of 1 mil Au to In

17. Au changing into Au-In compound

18. Au wire with In attack: side view

19. Au wire with In attack: top view

20. Indium Solder and 1 mil Gold Wires

21. GSFC Websites about this topic NASA/GSFC Technology Validation Assurance Web Site: http://misspiggy.gsfc.nasa.gov/tva/ Reliability of Laser Diodes for Space Flight Applications: http://misspiggy.gsfc.nasa.gov/tva/meldoc/photonicsdocs/LDreliability.ht m