Datasheet
DD2.X
PowerPC 750CL Microprocessor
Preliminary
The 750CL FCPBGA module features a silicon die that is connected to a plastic laminate substrate by a
number of solder balls. The thermal coefficient of expansion (CTE) of the silicon and the plastic are unequal,
which creates mechanical stress on the interconnect as the temperature changes. In normal operation, large
temperature changes are usually the result of turning the power on and off (on/off cycles). Smaller tempera-
ture changes (mini-cycles) are caused by a number of factors, including the change of the 750CL from nap or
sleep mode to full-on operation. Mini-cycles cause smaller temperature changes so are less stressful than
on/off cycles, but both must be considered when assessing the package reliability in a specific application.
Figure 1-2 on page 15, Figure 1-3 on page 16, Figure 1-4 on page 17, and Figure 1-5 on page 18 show the
maximum number of on/off cycles and mini-cycles that can occur over the life of the 750CL without reducing
the lifetime of the part. These limits are more than adequate for most applications. If a particular application
falls outside the stated limits, the designer should review the expected application conditions to see if realistic
values are being used. Often, minor tweaking and trade-offs can be made in order to bring the application into
compliance. Contact your IBM PowerPC field applications engineer or ppcsupp@us.ibm.com for information
or assistance.
To use the figures to verify that the expected on/off cycles and mini-cycles do not reduce the reliability of the
750CL:
1. Choose the expected amplitude of the mini-cycles for the target system. Use Figure 1-2 for 20°C mini-
cycles, Figure 1-3 for 30°C mini-cycles, Figure 1-4 for 40°C mini-cycles, and Figure 1-5 for 50°C mini-
cycles.
2. Choose the curve that represents the amplitude of the on/off temperature cycles in the target system. The
graphs assume that the low point of the temperature cycle (T [low]) is 20°C. The high point of the temper-
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ature cycle (T [high]) is labeled for each curve (as 60°C, 70°C, 80°C, 90°C, or 100°C).
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3. The envelope of acceptable temperature cycles is defined as the area below the appropriate curve.
For example, suppose the target system is expected to experience mini-cycles of 20° amplitude, and on/off
cycles that vary T from 90°C down to 20°C and back. See Figure 1-2 for 20°C mini-cycles. Any combination
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of on/off cycles and mini-cycles that is on or below the 90° curve will not reduce the reliability of the part:
• 9000 on/off cycles and 1000 mini-cycles
• 8000 on/off cycles and more than 10,000 mini-cycles
• 7000 on/off cycles and approximately 30,000 mini-cycles
• 4000 on/off cycles and approximately 70,000 mini-cycles
There is some overlap in the graphs. For example, a power cycle could cycle the temperature from 20°C to
70°C, which is a 50°C cycle. In this case, these cycles can be considered either on/off cycles or mini-cycles,
whichever is more favorable.
Note: The graphs in Figure 1-2 through Figure 1-5 were generated using the following assumptions, and are
not valid under other conditions:
• T (high) is 100°C or less.
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• The maximum junction temperature that the part will experience is T (high) + 20°C, not to exceed 105°C.
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The part will experience this maximum junction temperature for no more than 10% of its lifetime.
• Mini-cycles vary T from T(high) down to a lower temperature and back. For example, in Figure 1-2, the
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lower temperature is T(high) - 20°C.
• T(high) and the amplitude of the mini-cycles represent the median expected values.
General Information
Page 14 of 70
Version 2.5
December 2, 2008
IBM [ IBM ]
