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SMT reflow oven types introduction

  • Time:2022-01-12
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SMT reflow oven soldering types introduction

The quality of soldering directly determines the quality of the entire product, and soldering quality depends on soldering materials, soldering equipment, and soldering technology. Soft brazing technology is used in the SMT process, mainly including SMT reflow oven soldering and wave soldering. To help everyone gain a deeper understanding, this article will summarize the relevant knowledge of SMT reflow oven soldering. If you are interested in the content that will be covered in this article, then continue reading.

1. What is SMT reflow oven soldering?

SMT reflow oven soldering relies on the action of hot air flow on the solder joint, allowing the adhesive solder paste to undergo a physical reaction under a certain high-temperature air flow to achieve SMC/SMD soldering. Because the gas circulates in the soldering machine to generate high temperature and achieve the soldering purpose, it is called SMT reflow oven soldering.

2. According to technical classification

(1)Hot air SMT reflow oven soldering

By using the heater and fan inside to heat up and continuously increase the internal temperature before cycling, soldering is carried out in this way. The characteristic of this type of reflow soldering is to transfer the heat required for soldering through laminar flow of hot air; The advantage is that during soldering, the thermal energy is always maintained within a certain temperature range, and there will be no sudden hot or cold situations. This makes soldering easier and the success rate higher.

(2)Hot gas SMT reflow oven soldering

The characteristic of hot gas reflow soldering is to use hot gas for soldering. This soldering method requires continuous adjustment of the welded joint according to the size of the soldering, which greatly reduces the efficiency of soldering.

(3)Hot wire SMT reflow oven soldering

Using heated metal for direct soldering is often used on cables, and its joints have a certain degree of flexibility. Therefore, soldering is carried out by heating without the need for solder paste, which is a relatively difficult soldering technique, resulting in slower soldering speed and reduced work efficiency.

(4)Induction SMT reflow oven soldering

Using a principle of inductive eddy current, this product does not require mechanical contact, which reduces the need for a carrier and greatly improves heating speed. However, due to the lack of a carrier, temperature control is difficult, and if the technology is not advanced, errors are prone to occur.

(5)Laser SMT reflow oven soldering

Using laser heating SMT reflow oven soldering for soldering, because laser has good directionality and specificity, using laser soldering can effectively process a point that needs to be welded, so that the welded product can be well controlled and reduce deviation.

(6)Infrared (IR) SMT reflow oven soldering furnace

This type of SMT reflow oven soldering furnace is also mostly conveyor belt type, but the conveyor belt only serves as a support and conveying substrate. Its heating method mainly relies on infrared heat sources to heat in a radiation manner. The temperature in the furnace is more uniform than the previous method, with larger mesh holes, suitable for SMT reflow oven soldering heating of double-sided assembled substrates. This type of SMT reflow oven soldering furnace can be said to be the basic type of SMT reflow oven soldering furnace. It is widely used in China and the price is relatively cheap.

(7)Gas phase SMT reflow oven soldering

Gas phase SMT reflow oven soldering, also known as vapor phase soldering (VPS) or condensation soldering. Heating carbon fluoride (using FC-70 fluorochlore solvent in the early days) with a melting point of about 215 ℃, boiling produces saturated vapor. There are condenser tubes above and on both sides of the furnace, which restrict the vapor in the furnace. When encountering low temperature PCB components to be soldered, the latent heat of vaporization is released, allowing the solder paste to melt and then solder the components and pads. The United States initially used VPS for soldering thick film integrated circuits (ICs). The release of latent heat from gas is not sensitive to the physical structure and geometric shape of SMA, allowing the components to be uniformly heated to the soldering temperature. The soldering temperature is maintained at a certain level, without the need for temperature control to meet the soldering needs at different temperatures. The gas phase of VPS is saturated vapor, with low oxygen content and high heat conversion rate, but the solvent cost is high, and it is a typical ozone layer depleting substance, Therefore, the application is greatly limited, and the international community basically no longer uses this environmentally harmful method.

3. Classify according to shape

(1)Desktop SMT reflow oven soldering furnace

Desktop devices are suitable for small and medium-sized PCB assembly production, with stable performance and affordable prices. They are commonly used by domestic private enterprises and some state-owned units.

(2)Vertical SMT reflow oven soldering furnace

There are many models of vertical equipment that are suitable for PCB assembly and production for users with different needs. The equipment is available in high, medium, and low grades, with significant differences in performance and varying prices. It is commonly used by domestic research institutes, foreign enterprises, and well-known enterprises.

4. Classification based on temperature zone

The length of the temperature zone in a SMT reflow oven soldering furnace is generally 45cm to 50cm, and there can be 3, 4, 5, 6, 7, 8, 9, 10, 12, 15 or even more temperature zones. From a soldering perspective, SMT reflow oven soldering has at least 3 temperature zones, namely preheating zone, soldering zone, and cooling zone. Many furnaces usually exclude the cooling zone when calculating the temperature zone, that is, only the heating zone, insulation zone, and soldering zone are calculated.