TC wire – why the thermocouple wire has been used in SMT production

How to use TC wire correctly

TC wire is one of the best tools used to measure ambient temperature in the PCB Assembly factory because it is cheap, accurate, wide range of temperature measurement, and sensitive reaction time.

However, there are a variety of different models of thermocouple wire available on the market and in the industry at present. The types can be divided into B, E, J, K, N, R, S, T… Etc.

According to the metal wire material used by the thermocouple, the microvolt voltage difference generated by the change of each degree Celsius (µV/°C) will also be different, so it must be matched with the temperature meter to choose the correct TC model, otherwise it may cause the temperature reading error.

Table of Contents
    Add a header to begin generating the table of contents

    How to choose SMT TC wire

    K-type TC wire is the most commonly used type in the industry at present, and K-type TC wire is almost always used in reflow ovene for temperature measurement.

    It should be noted that, depending on the type and material of the coating TC wire, the applicable temperature will be limited and different. Please pay attention to the selection and use of the TC wire. It is generally recommended that the TC wire used in reflow should be selected with a temperature resistance of at least 300°C, if considering that the temperature of the PCB soldering process iron head may be measured, It is recommended that the temperature should be above 400°C.

    In addition, K-type TC wire is not recommended if the environment is in a higher temperature zone (700°C ~ 1260°C) and the oxygen concentration is low, because the nichcr alloy wire will deteriorate due to green rot phenomenon in a high temperature and low oxygen environment, resulting in a significant decrease in the thermoelectric EMF value, resulting in excessive measurement error.

    How to select the diameter of TC wire used on SMT temperature measurement board

    How-to-select-the-diameter-of-TC-wire-used-on-SMT-temperature-measurement-board

    The AWG (American wire gauge) standard is used to gauge the diameter of TC wire.In fact, the diameter of TC wire has no correlation with the accuracy of temperature measurement, that is, the diameter of the TC wire will not affect the temperature measurement results. But the diameter of the TC wire will directly affect the bending and wiring abilities of TC on the temperature measurement plate.

    The larger the diameter of the temperature measuring line, the stronger the wire basically, and the less easily broken; But the relative shortcomings are not easy to be bent to wiring, the size of the temperature measurement point will be relatively large, adverse to the fine foot parts of the solder joint temperature measurement.

    On the contrary, the smaller the diameter of the temperature line wiring is easier, some wiring may need to perforate the solder joint below the parts body measurement such as BGA tin ball temperature measurement) you need to use TC wire with small diameter.

    The disadvantage is that the smaller the TC wire diameter, the easier it is to be broken. During and after the temperature measurement point operation, special attention needs to be paid to whether there is a fault with the meter measurement.

    The conventional SMT production line temperature measuring board will recommend the use of AWG30 TC wire diameter ((0.01″/0.254mm) It is recommended to use AWG36 TC wire diameter (0.005″/0.127mm) if there is a perforating operation requirement or need to be used in the fine foot parts.

    What is the function of TC wire in reflow oven profile board

    What is the function of TC wire in reflow oven profile board

    When making profile board, it is best to keep a pair of TC wire to measure the air temperature, which is actually to measure the temperature of the actual environment in the reflow oven.

    In fact, what we really should pay attention to is whether the actual temperature on the board meets the specification requirements of the solder paste and other parts, but the temperature on the board is heated by the ambient temperature in the reflow oven, and the temperature in the furnace is heated by the temperature setting of the reflow oven. 

    Theoretically, the ambient temperature in the furnace should be consistent with the temperature setting of the reflow oven. Therefore, the air line set on the temperature measuring plate is equivalent to measuring the ambient temperature in the welding furnace.

    The temperature of the board is gradually heated from low temperature. According to research, there is a drop between the board and the temperature in the furnace of about 10 ~ 30°C, which is why we need to make temperature measuring board to measure the temperature of the board.

    The working principle of TC wire in reflor oven

    The working principle of TC wire in reflor oven

    Since the TC wire can roughly represent the ambient temperature in the reflow oven, and the temperature in the furnace and thel temperature of the board will be about 10 ~ 30°C, because the board is gradually heated after entering the reflow oven from low temperature. This is why we need to make temperature measuring board to actually measure the temperature of the board.

    Therefore, we can use the temperature of TC wire to compare the actual temperature difference of the feet on the board, and finally fine-tune the speed and temperature setting of the board in the reflow oven by using the data of the TC wire to optimize the reflow temperature curve. 

    This is because so far, the reflow oven has not been able to feedback the actual temperature of the plate in the furnace at the same time, can only be reduced to using an independent thermometer to measure the relationship between the ambient temperature in the furnace and the actual temperature of the plate.

    Some reflow thermometers require an additional TC wire in addition to measuring the temperature of the foot of the welded part. This TC wire does not need to be fixed on any part, but should be suspended on the leading edge of the board. The KIC thermometer specifically requires that the TC wire be fixed in the middle of the front end of the temperature measuring board, which is about 2.5cm beyond the edge of the board.

    Conclusion

    This TC wire can be used to measure the ambient air temperature in the reflow oven as a reference for the fine-tuning of the temperature of the reflow oven later .It will also use the TC wire to judge whether the board has entered the heating area of the reflow oven and automatically open the temperature record.

    Similarly, it can also automatically judge the current reach the area of the reflow oven, whether it has been out of the reflow oven and automatically stop the temperature record, in order to save memory space.

    FAQ

    TC wire is one of the best tools used to measure ambient temperature in the industry because it is cheap, accurate, wide range of temperature measurement, and sensitive reaction time.

    K-type TC wire is the most commonly used type in the industry at present, and K-type TC wire is almost always used in reflow ovene for temperature measurement.

    The AWG (American wire gauge) standard is used to gauge the diameter of TC wire.In fact, the diameter of TC wire has no correlation with the accuracy of temperature measurement, that is, the diameter of the TC wire will not affect the temperature measurement results.

    Related Posts

    Exploring the Role of PCB Fuse in Circuit Protection and Safety

    Exploring the Role of PCB Fuse in Circuit Protection and Safety

    In the realm of electronic circuit design and manufacturing, ensuring the safety and reliability of electrical systems is paramount. One crucial component that plays a ...
    Mastering High-Frequency PCB

    Mastering High-Frequency PCB: From Concept to Production

    In the rapidly advancing world of electronics, the demand for high-frequency PCB continues to soar. From wireless communication systems to radar applications, the need for ...
    How many kinds of the common PCB defects?

    How many kinds of the common PCB defects?

    During the production and processing of PCBs, various defects may occur due to various reasons. These defects not only affect the performance of the PCB ...
    Short Circuit Unveiled

    Short Circuit Unveiled: Causes, Effects, and Solutions

    In the vast domain of electrical engineering, few phenomena hold as much significance and potential danger as the short circuit. A short circuit isn't merely ...
    The Essentials of Solder Joints : A Comprehensive Guide

    The Essentials of Solder Joints : A Comprehensive Guide

    Solder joints are the fundamental building blocks of electronic assemblies, forming the connections that enable the functionality and reliability of countless devices in our modern ...
    Request a Quote

    Leave a Comment

    Your email address will not be published. Required fields are marked *

    en_USEnglish
    Scroll to Top