Type K thermocouple for Super M.O.L.E| 3 November, 2001
Hi I have question about thermocouple type use for Super M.O.L.E. I found in some article that type K T/C (Nickel-Chromium vs. Nickel-Aluminum) may suffer from temperature cycling hysteresis at above 250 degree C and also diffecult to solder. Now I use type K T/C with Super M.O.L.E and found that it really hard to solder and our plant will implement lead free process soon. So I would like to know can i use another type of T/C with super M.O.L.E ? Which type of T/C is suit for attachment by solder and lead-free process?
I would appreciate any help you can give me regards Ben
Type K thermocouple for Super M.O.L.E| 5 November, 2001
Most people do not intend to �solder� Type K thermocouples. They use solder to �attach� the thermocouple. Search the fine SMTnet Archives for a posting by Chrys Shea.
1 Common thermocouple types commonly used for thermal profiling are: * Type K � nickel-chromium vs. nickel-aluminum. The operating temperature range is -200� to 1,250�C with an accuracy of �1.5�C. This material is difficult to solder. It is the most commonly used thermocouple wire. * Type T � copper vs. copper-nickel. The operating temperature range is -200� to 400�C with an accuracy of �0.5�C. This material is easy to solder. * Type J � iron vs. copper-nickel. The operating temperature range is -210� to 800�C with an accuracy of �1.5�C. This material is difficult to solder. * Type N � nickel-chromium-silicon vs. nickel-silicon-magnesium. The operating temperature range is -200� to 1,280�C with an accuracy of �1.5�C. This material is difficult to solder.
2 KIC Thermal Profiling did a DOE [Nepcon West 1999] on thermal couple attach. Comparing the reliability and repeatability of thermocouple attachment methods: * High temperature solder was found to be the most reliable and repeatable method of attaching thermocouples to PCB�s. * Aluminum tape provides a reliable alternative to high temperature solder, though it is slightly less repeatable. * Kapton tape is not reliable or repeatable. * Conductive Epoxy is reliable for a single profiling run, but offers poor repeatability. Its thermal conductivity is very inconsistent, and the results of these profiles seem inaccurate and unreliable
Returning to your comment that Type K thermocouples �suffer from temperature cycling hysteresis at above 250� C� � * Certainly all thermocouples exhibit measurement hysteresis [A lack of voltage retraceability as the temperature decreases], what is temperature cycling hysteresis? * What happens with this temperature cycling hysteresis upon reaching the 250�C? * What are the references for these articles? * What are the implications of this �suffering� in a typical electronic mass-soldering environment? * Is this �suffering� different for other thermocouple types?