Hi,
When using a heat sink with AM57xx, please tell me what N(newton) is allowed as a load of the fastener.
In the case of other company's processor, the following description seems to be defined.
Is there such definition in AM57xx too?
It does not seem to be in the data sheet.
Best Regards,
Shigehiro Tsuda
Shigehiro,
The figure below shows the maximum pressure per ball for SAC305 solder balls on a package with 0.8mm pitch.
This shows that the allowable pressure must be derated based on system lifetime projections and average operating temperature. This value selected from this table can be multiplied times the number of balls in the package. Then an additional derating factor must be applied assuming that ball pressure is not consistent (i.e. it is higher on one corner due to soldering which results in the device planarity not matching the PCB). For instance, using 61 grams/ball (from 10 years at 100C) times 760 balls results in a pressure of 46,360 grams or about 21 pounds. This value then needs to be derated based on the mechanical coplanarity or spring tension variations.
Tom
