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INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY

1.2 ASSEMBLY (BACK-END)

The first step of assembly is to separate the silicon chips: this step is called die cutting.

Then, the die are placed on a lead frame: the “leads” are the chip legs (which will be soldered

or placed in a socket on a printed circuit board. On a surface smaller than a baby's fingernail

we now have thousands (or millions) of electronic components, all of them interconnected and

capable of implementing a subset of a complex electronic function. At this stage the device

is completely functional, but it would be impossible to use it without some sort of supporting

system. Any scratch would alter its behaviour (or impact its reliability), any shock would cause

failure.

Therefore, the die must be put into a ceramic or plastic package to be protected from the ex-

ternal world. A number of operations have to be made to realize this: they are described on the

following graph.