As part of any good process control system, soldering iron tip temperature should be periodically checked to verify that the soldering iron is operating within specifications and meets or exceeds any defined tolerances for temperature stability and accuracy.  Hakko does not establish the frequency for this verification since it is dependent on your own process control culture as well as past results. 

NOTE:  When making any measurement, tolerances of both the the soldering station and measuring device must be figured into this process since these tolerances will stack.  In the case of measuring tip temperature for verification, the tolerance stack should be calculated using the Root-Sum-Square (RSS) method.

To measure soldering iron tip temperature, we recommend the use of a Hakko FG-100 Tip Thermometer or Hakko FG-101 Station Tester.  For the purpose of this article, we will use a Hakko FG-100 Tip Thermometer.  Be sure that the measuring device you choose to use has a valid certificate of calibration with traceability to an accepted standard.

It is also important to take precautions against measurement error that can be introduced unintentionally.  To mitigate common measurement errors:

• Measurements should be made in a location free from any air currents or drafts such as from an air conditioning vent or room fan.
  
  
• Sensors should be replaced every 50 to 60 measurements.  Studies have shown that sensors oxidize during use and their ability to conduct heat deteriorates over time which can reduce the accuracy of the reading over time.
  
  
  
• Measurements should be made by the same person under the same conditions to reduce the affect of errors between variations in conditions and techniques used.

Start by cleaning the soldering iron tip to remove any oxidation or other deposits on the tip's surface that can interfere with the tip temperature measurement and reduce the accuracy of the temperature reading.

Place the soldering iron tip onto the sensor and apply solder as if you were making a solder connection.

IMPORTANT:
Be sure that the soldering iron tip is held in the horizontal to the sensor with minimal movement to maximize physical contact between the middle of the working surface of the tip and the sensor.  An angle between the tip and sensor and/or movement of the tip on the sensor may reduce the accuracy of the temperature reading.

Example 1 - Correct Tip-to-Sensor Alignment (Typical Tip Shapes)

Example 2 - Incorrect Tip-to-Sensor Alignment (Typical Tip Shapes) - Bad Position

Example 3 - Incorrect Tip-to-Sensor Alignment (Typical Tip Shapes) - Bad Angle

Example 4 - Correct Tip-to-Sensor Alignment (Narrow/Sharp Tip Shapes)

Example 5 - Incorrect Tip-to-Sensor Alignment (Narrow/Sharp Tip Shapes) - Bad Position

Example 6 - Incorrect Tip-to-Sensor Alignment (Narrow/Sharp Tip Shapes) - Bad Angle

Hold the soldering iron tip on the sensor allowing enough time for the temperature measurement to stabilize at the highest reading.  This is very important for tips that have a narrow, sharp shapes.

NOTE:  The Hakko FG-100 Tip Thermometer and Hakko FG-101 Station Tester includes a 'Max Hold' feature that cause the display to only show the highest reading.

Repeat the measurement three (3) times to obtain the highest tip temperature.  Use this temperature to verify/validate that the soldering iron is operating within specifications and meets or exceeds any defined tolerances for temperature stability and accuracy.