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X-Ray Inspection to Identify Counterfeit Parts Continued from previous page
will mix in different components with different die sizes. Another technique to verify the size of the die is to take a side view x-ray image of the part. In this case the through density of the die is enough to appear in the x-ray image.
l Inconsistent leadframe. Similar to
the previous case, counterfeiters often mix parts with different lead- frames in the same lot.
l Broken or missing wire bonds. A
broken wire bond may be a result of extreme mechanical or thermal stress applied to the part. Similarly, the absence of wire bonds is the sign of a suspect lot of parts. It is very important to note that some parts are packaged with aluminum wire bonds. Since alu- minum is a low-density material, these wire bonds will not show in an x-ray image. For this reason, if you cannot see the wire bonds in a part, we recommend decapsulation it to confirm that they are not Al wire bonds. X-ray can show gold and copper wire bonds.
l Incorrect wire-bonding diagram.
Even if the parts have the same leadframe and die size, you must verify that the wire-bonding dia- gram is consistent.
l Missing die. Although you may not
be able to see the die directly, it is important to verify the presence of wire bonds and the die attach fillet. We found several examples of empty packages being sold as functioning parts.
l Inconsistent die attach voiding. The mature semiconductor manufac-
TruView 180HDx X-ray inspection with embedded reel-to-reel inspection system.
Same Part Number In some cases, legitimate com-
ponents with the same part number will have different internal struc- tures. For them to be legitimate, the lot number and/or date code must be different. The following three examples illustrate how good components can
inspection have different lot num- bers and/or date codes. Otherwise they should be deemed highly sus- pect.
l
Different Leadframe Structure. Market globalization has led to the distributed manufacturing of elec- tronic components. Therefore, it is common for original component manufacturers (OCM) to fabricate
turing process leads to consistent parts. The presence of large varia- tions in the die attach voiding may be a reason to fail the parts.
end up with different internal struc- tures as seen by the x-ray inspection. In these examples we assume that the parts analyzed with the x-ray
December, 2012
the same part number in their domestic and international facilities. It is entirely possible that these dif- ferent locations procure different leadframes due to relationships with their suppliers. It is also possible for a manufacturing plant to change leadframes at a certain point in time based on design and/or supplier changes.
l Different Die Size. “Die shrink” is
a term often used in the semicon- ductor industry to refer to the con- tinuous miniaturization of integrat- ed circuits. According to Moore’s Law, the number of transistors in an integrated circuit doubles every two years. This means that the same circuit can be implemented in a fraction of the size of the previous generation of semiconductors. Thus, die shrink is a natural consequence of the evolution of the electronics industry. What it means to you is that it is possible to find legitimate components with different lot num- bers, date codes, and die sizes. The wire bonding diagram of these parts is usually the same, but not neces- sary always identical.
l Different Wire Bonding Diagram.
As a consequence of die shrink, the power and signal characteristics of different generations of the same component can change. For example, it is possible that the earlier genera- tion of a part needed more power to bias larger transistors. Thus, the multiple wire bonds needed to carry the necessary current to bias an earli- er version of the die may not be nec- essary for the lower power later ver- sions of the same circuit.
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