Talking about SMT reflow soldering technology Briefly

484 Published by FASTPCBA 4月 15,2019

Talking about SMT reflow soldering technology Briefly

SMT reflow soldering , also known as return soldering, is a soldering method that does not require any additional solder during the soldering process by remelting the pre-placed solder to form solder joints.

Compared with wave soldering, it has the following advantages:

  1. Quantitative distribution of solder paste, high precision, less heat generation of solder, less agitation and less usage;
  2. Suitable for all kinds of high precision and high requirements components;
  3. There are few soldering defects in the mountingprocessing, and the bad solder joint rate is below10ppm.

Second, reflow welding method:

  1. Infrared reflow oven
  2. 80% of the energy in the heat is emitted in the form of electromagnetic waves – infrared rays. The wavelength is between 0.7~0.8um and 1mm of visible light, 0.72~1.5um for near infrared; 1.5~5.6um for mid-infrared; 5.6~1000um for far infrared, and microwave is above on far infrared.
  3. The mechanism of temperature rise: When the vibration frequency of the infrared wavelength coincides with the vibration frequency between the molecules of the irradiated object, resonance occurs, and the intense vibration of the molecule means the temperature rise of the object. The wavelength is 1~8um.
reflow soldering

reflow soldering

The fourth zone has the highest temperature setting, which can cause the temperature of the weld zone to rise rapidly and improve the wetting force. Advantages: rapid water gasification of flux and organic acid and halide to improve wetting ability; infrared heating radiation wavelength is similar to absorption wavelength, so substrate heating is fast, temperature difference is small; temperature curve control is convenient, elasticity is good; infrared heater High efficiency and low cost.

Disadvantages: poor penetration, shadow effect – uneven heat.

Countermeasure: A hot air circulation is added to the reflow.

2.Infrared hot air reflow soldering.

The speed of convective heat transfer depends on the wind speed, but excessive wind speed will cause component displacement and promote oxidation of the solder joint. The wind speed is controlled at 1.0~1.8m/s. There are two forms of hot air generation: axial fan generation (easy to form laminar flow, which causes the temperature to be unclear) and tangential fan (the fan is installed outside the heater to create a panel vortex to make the first temperature zone available to control precisely).

Adjustment of basic structure and temperature curve:

  1. Heater: tube heater, plate heater aluminum plate or stainless steel plate;
  2. Transfer system: heat-resistant PTFE fiberglass cloth;
  3. Smooth operation and good thermal conductivity;
  4. Suitable for small hot plate stainless steel mesh, suitable for double-sided PCB.

The above is the industry knowledge provided by FASTPCBA Electronics, I hope it’s helpful you! For more information, please visit Thank you for your attentions and comments! ! !


PCB manufacturer reflow soldering machine heating system

PCB manufacturer reflow soldering machine heating system   The full hot air and infrared hea...

Do you like ? 598

Read more
Types and advantages of flexible pcb circuit board

Types and advantages of flexible pcb circuit board The PCBA board is the finished product after t...

Do you like ? 715

Read more
What are the SMT process

What are the  SMT process Everyone knows that the electronic products we use in our lives are ass...

Do you like ? 1,684

Read more
What is the difference between PCB and PCBA

What is the difference between PCB and PCBA What is a PCB PCB = printed circuit board; PCB is an ...

Do you like ? 1,667

Read more