Qualification of the Assembly Process of Flip-Chip BGA Packages ...

2.1 What is Qualification? [7]
Texas Tech University, Nivetha Shivan, May 2012
CHAPTER 2
PURPOSE OF THIS QUALIFICATION
Whenever a product, process or package type is changed, it is required to validate that
these changes did not affect the functionality and reliability of the final product. The
devices are subjected to a baseline of acceptance tests which are capable of stimulating
device and packaging failures. These failures are stimulated in an accelerated manner as
compared their normal use conditions. The motive behind any qualification project is to
look for any new and unique failure modes, and also to look for any situations where the
stress tests will induce invalid failures.
2.2 Quad Data Rate SRAM
Memory devices are semiconductor units that are capable of retaining digital data.
Depending on whether the memory loses its contents upon power removal, it is divided
into volatile and non-volatile memory. Volatile being the type which loses and non-
volatile being the one which does not lose its contents. The volatile memory is divided
into static and dynamic.
Unlike dynamic memory, static memory does not have to be refreshed periodically. It
also runs faster than the former type of memories. There are two types of SRAMs –
Synchronous and Asynchronous. The asynchronous SRAMs do not have a clock signal
which can control when the data input and output signals are transferred. The data output
comes out after a delay with the data input signal. But in synchronous SRAM, there are
clock signals which can control the timing of the data input and output signals because of
which the frequency with which the signals are transferred can be increased. Hence Sync
SRAMs are faster than Async SRAMs.
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