On 9/29/2020 4:38 PM, Bob kb8tq wrote:
Hi The gotcha with *any* SMT part is that stress / strain from the soldering process gets into the performance of the part for a *long* time. There is no mechanical “buffering” in most parts. Whatever the PCB does is what the guts of the part sees …. Given the popularity here on the list of hand soldering SMT parts, that’s a very high stress way to mount them …. yikes …. Bob
The other issue with SMT thermistors is that you normally want glass bead thermistors with very long and very skinny leads that reduce head transmission via the leads. Proper management of the thermistor leads in OCXO's is very important. In the 10811 for example, the thermistor in potted into a very deep hole using thermally conductive (silver loaded) epoxy. The leads run all the way through this hole which is filled with the epoxy. The hole is drilled in the oven mass. An analogous scheme is used in the E1983A. What you could do with SMT thermistors is to glue leads onto them with *electrically* conductive epoxy. This avoids soldering trauma. You could use very small gauge wire, as is SOP with leaded thermistors. You might take the opportunity to use wire with low thermal conductivity, such as nickel. Rick N6RK _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
