| Inexorable and rapid advances in digital electronics enable the development of ever more sophisticated electronic devices but lead to an obsolescence headache for manufacturers outside the consumer sector where design life cycles are long. Semiconductor producers move on to supplying new designs and stop producing the older ones. This leads to a range of problems for equipment manufacturers looking to source obsolete components.
The problem - coping with component obsolescence
For a while the old design will be available along side the new one but eventually production of the old design will stop accompanied by the notification of a “last time buy” - a one off opportunity to stock pile critical components. After this there will still be some available from distributors but the original suppliers will no longer support them.
As stocks dwindle and sourcing becomes more difficult manufacturers are forced to buy not just from franchised distributors who know where their inventory comes from but from other less dependable suppliers - the so called “grey” market. The provenance of components on the grey market is often unknown or at least unclear. There are also more worrying possibilities including counterfeiting and re-marking which may lead to product reliability problems.
Case study - investigating counterfeit components
ERA has recently investigated batches of devices of the same type number for a manufacturer who was encountering failures in production. While identical on the outside, closer inspection revealed several different designs. Figures 1 to 4 show some of these variants, all at the same magnification.
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Figure 1. Variant 1 - the earliest design. No circuitry between the bond pads |
Figure 2. Variant 2. Some protective circuitry between the pads |
The early design in figure 1 had no parts of the circuit or tracks between the bond pads, as the “real estate” was not deemed so valuable. The different design in figure 2 has some of the protective circuitry between the pads. The chip in figure 3 is similar but has undergone a slight shrink. There were also a few variants like the square chip in figure 4.
Figure 3. Variant 3. The chip is slightly smaller |
Figure 4. Variant 4. Redesign into square form factor |
One group of four devices with the same date code (about 6 years ago) had three different types of chip inside. Some of these worked, some passed functional tests of the complete board and some failed automatic testing of components on the board (ATE)
Even with components of known provenance, further potential problems arise when using old components. These include:
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moisture absorption - unless the components have been stored very carefully they may have absorbed moisture with the possibility of “popcorn damage”, where the water boils during soldering and splits the package. |
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solderability - it is often recommended that components are used within 6 months as the terminals may tarnish if left longer and become more difficult to solder. |
Counterfeiting of components increase the uncertainty regarding component performance and so compounds the problem. As the above example shows, even the same date code on the outside of a device provides no guarantee that what is inside is the same.
Further information
The Reliability and Failure Analysis group has investigated many instances of counterfeiting and the reliability issues that arise (click here for another example). To find out more call us on +44 (0)1372 367444 or email.
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Counterfeit components - detection and reliability
