Junction Temperature Derating Curve



Wirebond Life vs Tj [Junction Temperature]

The failure rate of the wire bond between the bonding wire and the bonding pad on a semiconductor die. Which is the attachment point of the semiconductor die to the terminals of an integrated circuit.

Semiconductor Wirebond Time to Failure vs Junction Temperature
Wirebond Time to Failure vs Junction Temperature

The wirebond could fail for a number of reasons, the chart shows the failure rate as the junction temperature rises. Additional types of wirebond failures include Early Failures and Wear Out Failures. However this chart does not include early failures, also called infant mortality. But the graph does include the number of hours at a particular temperature that would cause a failure.

Failure Rate Calculations
Failure Rate = 1 / MTBF
MTBF = Mean Time Between Failure
MTBF = (Total device failures) / (Total number of failures)

Transistor Wirebond Construction Cut-away
Wire-Bond Failures by Temperature




The graphic shows an internal view of a surface mount 3-terminal semiconductor package [FET or BJT] showing the wirebond connection, or bonding wiring between the semiconductor chip and the internal lead frame.

What I did not take note of was what type of wire bonding was used with the failure rate graph above, or if there are different types of wirebonding. However what is strange about the graph is the temperatures used and the related failure rates seem to be below what is recommended in many of the Transistor Derating Curves. For example most if not all the recommendations call for a transistor to be operated at or near 125 degrees centigrade which would only be 200,000 hours of operation [22 years].
However the difference between semiconductor temperature and bonding temperature could be because the wire bond connection survives longer or at a higher temperature than the actual semiconductor die. Any of the derating curves shown by the link will show a maximum operating junction temperature, as the upper most line on the curve.

Reference list
Integrated Circuit Derating Guidelines
Semiconductor Derating Guidelines
Transistor Derating Curves
Transistor Manufacturers, BJT vendors.

Graphic; 14 pin IC semiconductor die.

    16-pin Semiconductor Die showing Bonding Pad locations

An example of a semiconductor die. The bonding pads are the gold squares on the outside of the semiconductor chip. The square pads are the input/output pins while the two longer rectangular pads are power and ground connections. The black square is a company logo and not a wire bonding location.


The example below shows two IC failure modes for the DAC5687 digital to analog converter. The graph shows the life of the part in years vs. continuous junction temperature for both wirebound voiding failures and electromigration failures. Again, just another example of how the temperature of the semiconductor junction effects the life of integrated circuits.

IC failure modes for the DAC5687 digital to analog converter
Failure Modes vs. Junction Temperature

The part number for the IC is noted because the failure rate might change per IC or IC type, in addition to temperature. It also seems probable that the failure rate would change based on the number of terminals an IC has. Because as the number of terminal increase so does the number of wire-bounds between the semiconductor die and the IC package.

Note that the Life cycle definition, including End-of-Life refer to production and obsolescence of a part and have nothing to do with failure rates.


Semiconductor Bonding Wire Attachment to Bonding Pad
Wire-bond





IC Semiconductor Die Bonding shown in a DIP package
Semiconductor Die Bonding





MIL-STD-750 DOD Standard
Test Methods for Semiconductor Devices



Interpreting Deraring Curves, Transistor Derating Graphs
How to Read Derating Curves



Editor note:
Many terms are defined in the
Dictionary of Engineering Terms

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Modified 2/10/12
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