SMT reflow soldering technology process classification and characteristics

SMT reflow soldering technology process classification and characteristics

Before discussing the technical characteristics of wave soldering, let's first understand the classification characteristics of the next SMT reflow soldering. SMT reflow soldering has developed various specific forms, with the main difference reflected in the types of SMT reflow soldering equipment. According to the different heating ranges of the components, they can be divided into integral SMT reflow soldering and local SMT reflow soldering: integral SMT reflow soldering places the components in a reflow furnace for heating and soldering, which has high production efficiency and is the main form of large-scale production. Local SMT reflow soldering is the process of soldering each solder end and solder foot of one or more components onto a PCB one by one, in order to meet the requirements of components with strong thermal soldering requirements.

According to the heating sources of the equipment, there are conduction, convection, infrared radiation, gas-phase, and laser heating. In the entire SMT reflow soldering process, in order to improve heating efficiency and uniformity, and avoid the defects of a single heating method, a SMT reflow soldering furnace with two or more heat sources is usually used. At this point, infrared convective multi chip integrated SMT reflow soldering has become mainstream.

The classification and general characteristics of SMT reflow soldering technology are as follows:

1. Integrated SMT reflow soldering includes: infrared SMT reflow soldering, gas-phase SMT reflow soldering, and electric hot plate SMT reflow soldering.

2. Infrared convection type: All chips are in the radiation convection type SMT reflow soldering process, but the proportion of infrared radiation absorbed by the heated object is different. Infrared hot air SMT reflow soldering is widely used, but in many cases, it is mainly used.

3. Gas phase SMT reflow soldering: When the saturated vapor of an inert organic solvent accumulates into a liquid, it releases a strong heat of vaporization. Require the use of organic solvents with high heat transfer coefficients (using fluorinated liquids to destroy the ozone layer). The welding temperature is determined by the weaving point of the organic solvent. Accurate temperature control, fast and uniform heating, and low thermal shock.

4. Electric SMT reflow soldering: Using the thermal conductivity method of electric SMT reflow soldering for heating, the thermal efficiency is low and the heating is uneven.

5. Local SMT reflow soldering: Laser method, which uses the thermal energy of the laser to heat and concentrate the heat on the rose, and welds point by point.

6. Tool method: Heat with various tools, and the shape of the tool changes with the changes of the parts.

7. Infrared beam method: Using the high-temperature light points of an infrared lamp to heat, forming point light sources and line light sources.