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Technology Stocks : Rambus (RMBS) - Eagle or Penguin -- Ignore unavailable to you. Want to Upgrade?

To: Bilow who wrote (42792)	5/22/2000 6:25:00 PM
From: John Walliker	Read Replies (1) \| Respond to of 93625

Carl, I have plenty of experience of making thermal measurements (from liquid helium at around 4 deg Kelvin up to around 2000 deg C) and I am well aware of the difficulties involved in obtaining reliable results without perturbing the system which is being measured. I have used gas thermometers, various liquid thermometers, platinum resistance thermometers, diode thermometers, thermistors, various thermocouples, optical pyrometers and made quite a few sensors myself. Why do you think semiconductor manufacturers now often provide diodes on-chip specifically for measuring junction temperatures? It is because it is so hard to make reliable and meaningful measurements from the surface of the package. I did look at the photographs; that is why I made the comments that I did. Have you read the application report on how to make accurate thermal measurements on RIMMs, taking proper account of the various thermal resistances? Anand specifically said that a thermistor was used. Why do you keep referring to thermocouples? He did not say how he ensured good thermal contact with the RAM package surface. You seem to forget that heat shrink sleeving is a thermal conductor. There was no control over the airflow in the two situations. The thermal conductivity of an IC package is much lower than that of an aluminium plate. That is why the thermal loading of the thermistor and its wires could make a significant difference. Anand concluded that heat dissipation does not appear to be a problem. Fair enough. It is not sensible to try and deduce much more than that from a set of measurements which were never intended to be highly accurate. Nor did he. So why do you? John