Over the last few years it has become apparent that equivalent semiconductor devices are being offered more and more regularly. This is usually done correctly under controlled conditions and discussed with customers according to their requirements. Unfortunately however, there are times when it is not.
Outlined here we describe two examples. Firstly the case of International Rectifier (IR) parts. As an aside, we note that certain other manufacturers (for example Harris and Motorola), do share similar part number coding, specifically in the range of MOSFETs and Schottky diodes.
In the case of IR, all its products are marked with the official IR logo as shown in the accompanying illustration. No other logo is valid for International Rectifier products. The only variation on this logo is when it is used on the company's high power SCRs and diodes. In these cases the diode symbol shown between the I and the R distinguishes the polarity of the specific device it is marked upon. One should be very wary of purchasing product marked with valid IR part-numbers, but that fail to have the valid logo printed on them.
As in the second case with products from WESTCODE, the same applies. Each device should be clearly marked with the word 'WESTCODE'. Some older devices may be marked with a W as well as the word WESTCODE. This was an old logo that has recently fallen away. Newer devices now only have the word WESTCODE. Again, be wary when purchasing product with valid WESTCODE part-numbers but that fail to display the word WESTCODE clearly.
A unique characteristic of a WESTCODE product is that there is a number etched onto the device. In the case of 'Hockey Puck' type devices the number is marked on the flange, in the case of 'Stud' type devices the number is marked on the metal casing. This etched number is recorded at Westcode Semiconductors' Headquarters in the United Kingdom and is that device's particular tested electrical specification. All these etched numbers are unique - ie no two numbers will be the same.
In conclusion, although here we only discuss two manufacturers, a word of caution to anyone purchasing semiconductor products would be to check on what the original distinguishing manufacturer markings are, and in turn check that the specific product being purchased corresponds to this.
Remember, when in doubt, ask!
For further information contact Steve Cox, Advanced Product Technology, (011) 792 6010, [email protected]
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