The temperature drop is not always the same. It depends on:
- Geometry of the tip
- Thermal transfer surface (tinned surface in contact with pin and pad)
- The mass to be soldered
Geometry and Thermal Transfer Surface
A long and slim soldering tip, like C245030, has a small tinned surface (Ø0,3mm). Because of that its thermal transfer surface is small and the heat is transferred to the joint at a very slow rate. That is why small tips don’t require too much power to the station.
On the other side, a short and heavy tip like C245301 has a very large thermal transfer surface (Ø8,8mm). Because of that, thermal transfer from the tip to the joint is done at very high rate. The tip loses heat very fast and that’s way the station delivers a lot of power.
The bigger the difference in temperature between the tip and the selected temperature the more power is given to the cartridge. That is way the station gives the 100% of the power when taking the iron out of the hibernation mode. When the tip temperature and the selected temperature are equal, the power delivered to the cartridge is just about 5%, the minimum needed to maintain selected temperature.
Example of soldering speeds and temperature drops depending on the Thermal Transfer Surface
Next we have reproduced the client’s test. We have lasered welded K‐Thermocouples to the tip and to the “bulb”of a C245944 cartridge. Look at the temperature drop depending on the thermal transfer surface applied to a 0,8gr Ø10,5 copper coupon.
The bigger the tinned surface of the tip in contact with the coupon the bigger the temperature drop but also the more power transferred to the cartridge and the faster the solder joint is made.
That said, the longer the tip the bigger the distance between the thermocouple of the cartridge and the solder joint. For a given thermal transfer surface (tinned surface), the shorter the distance “L” the smaller the temperature drop will be.
Guidelines when selecting the best tip for the job:
- Select the tip that offers the maximum contact with pin and pad.
- If there is more than one tip that complies with the previous guideline, select the shorter one that the application allows. (A difficult to reach joint will require a longer tip).
- When making small joints, we recommend trying C210 cartridges (with T210 handpiece). C210 cartridges use very small tips where distance between thermocouple and solder joint is half the distance compared to C245 cartridges.