intermetallic issues with wire joining by thermocompression & soldering dr henning leidecker...
TRANSCRIPT
Intermetallic Issues WithWire Joining by
Thermocompression & Soldering
Dr Henning LeideckerGoddard Space Flight Center, Code 562
Parts, Packaging, and Assembly Technologies [email protected]
301-286-9180
21 Oct 2003
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
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 <==
Gold-Indium Phase Diagram
Optical Cross-section of a ball bond
SEM – intermetallic at base of bond
SEM – cross section
Note Cracks
Familiar Intermetallic?
Carbon Exuding From Grain Boundaries
Intermetallic Remaining
Normal and Carbon-Sensitive Images
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)
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”!
Wedge Bond of 1 mil Au to In
Wedge Bond of 1 mil Au to In
Au changing into Au-In compound
Au wire with In attack: side view
Au wire with In attack: top view
Indium Solder and 1 mil Gold Wires
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.htm