Modern plastic package assembly utilizes gold wire
bonded to aluminum bonding pads throughout the
electronics industry. As the temperature of the silicon
(junction temperature) increases, an intermetallic compound
forms between the gold and aluminum interface. This
intermetallic formation results in a significant increase in the
impedance of the wire bond and can lead to performance
failure of the affected pin. With this relationship between
intermetallic formation and junction temperature established,
it is incumbent on the designer to ensure that the junction
temperature for which a device will operate is consistent with
the long term reliability goals of the system.
levels that permit acceptable reliability levels, in most
systems, under the conventional 500 lfpm (2.5m/s) airflow.
11554.267
–9
T = 6.376 × 10
e
273.15 + T
J
Where:
T = Time to 0.1% bond failure
Junction
Time (Hrs.)
Time (yrs.)
Temp. (°C)
80
90
1,032,200
419,300
178,700
79,600
37,000
17,800
8,900
117.8
47.9
20.4
9.1
4.2
2.0
Reliability studies were performed at elevated ambient
temperatures (125°C) from which an arrhenius equation,
relating junction temperature to bond failure, was
established. The application of this equation yields the table
of Figure 3. This table relates the junction temperature of a
device in a plastic package to the continuous operating time
before 0.1% bond failure (1 failure per 1000 bonds)
100
110
120
130
140
1.0
The MC10SX1130 device is designed with chip power
Figure 3. Tj vs Time to 0.1% Bond Failure
High Performance Frequency
Control Products — BR1334
MOTOROLA
7
MOTOROLA [ MOTOROLA ]
